I. Assessment of Exercise Intolerance in Patients with Pre-Dialysis CKD with Cardiopulmonary Function Testing: Translation to Everyday Practice
- “CPET can delineate multisystem changes and offer comprehensive phenotyping of factors determining overall cardiovascular risk”. Please read this article and explain how the authors reaches this conclusion
- What are the most important parameters derived by the CPET?
- What is the level of evidence provided by this article?
The article is of level 5 of evidence.
Cardiovascular complications are the main cause of death in chronic kidney disease patients. Cardiopulmonary exercise test a dynamic noninvasive test is used for identification and assessment of risks as well as response to treatment.
Indications include evaluation of exercise capacity, assessment of the different causes of exercise intolerance, preoperative assessment and evaluation of those presenting with cardiac or respiratory diseases as well as assessing the response of treatment.
Contraindications of CPET include severe respiratory failure, serious dysrhythmias, uncontrolled HF, Acute MI, pulmonary edema or acute PE, severe electrolyte imbalance.
Most important indices elucidated by the CPET include: VO2 and Peak Oxygen Uptake, Anaerobic Threshold, Respiratory Exchange Ratio.
CPET
Indications:
Potential Clinical Applications of CPET in Patients with CKD:
Commonly measured variables are:
What is the level of evidence provided by this article?
Level of evidence is 5
CPET should be considered the gold standard for evaluating the causes of exercise intolerance
It is founded on the idea that system failure often happens when a stressed system (such the cardiovascular, pulmonary, or muscular-energetic systems) is involved. This dynamic, noninvasive test allows the doctor to assess both submaximal and peak exercise responses, giving them pertinent data for making therapeutic decisions
Principle :
In order to assess how each organ system responds to coupling external respiration (i.e., oxygen uptake (VO2) and carbon dioxide output at the airways) to cellular respiration (i.e., oxygen consumption and carbon dioxide production), during CPET, a large number of “routine” exercise testing variables and more advanced cardiorespiratory parameters are continuously measured or estimated
Indication :
a) determining exercise capacity
(b) determining exercise intolerance and its differential diagnosis; (c) determining disability;
(d) designing the rehabilitation programme and determining its effectiveness;
(e) preoperative evaluation;
(f) determining the functional and prognostic status of patients with heart diseases;
(g) determining the functional and prognostic status of patients with respiratory disorders; and
(h) determining the effectiveness of treatment
Common Parameters used:
VO2max (in mL/min or L/min)
VO2peak (in mL/min or L/min)
RER
VE
Ventilatory equivalents for O2 (VE/VO2) and CO2 (VE/VCO2)
VE-VCO2 slope
PETCO2 (in mmHg)
Respiratory reserve (VE/MVV) (both VE, MVV in L/min)
ΔVO2/ΔWR relationship (VO2 in mL/min and workload in watts)
Oxygen pulse (VO2/HR) (in mL of O2/min/bpm)
AT or VT
3- What is the level of evidence provided by this article?
Level V
“CPET can delineate multisystem changes and offer comprehensive phenotyping of factors determining overall cardiovascular risk”. Please read this article and explain how the authors reaches this conclusion. level of evidence V as its evidence from systemic review of descriptive and qualitative studies.
* CPET is an important tool to differentiate exercise intolerance ,monitor treatment response. It is a non-invasive multisystem stress evaluation which identify functional reserve of patient’s cardiopulmonary , metabolic system and neurophysiological system during a stress or resting state to see system failure. It can be used to evaluate the causes of exercise intolerance, in cardiovascular and respiratory patients.
What are the most important parameters derived by the CPET?
1. O2 consumptionVO2 = COP * difference of arterial-mixed venous O2 content , and Peak Oxygen Uptake: expressed in ml/min, It expresses the volume of oxygen during inhalation per minute. While, (VO2 max) is the highest value reached, despite progressive increase of the load applied, with the development of a plateau in the VO2 curve during an incremental exercise test. Peak VO2: is highest value reached at the end of an exhausting exercise test, used in both healthy and diseased populations.
2. Anaerobic Threshold (AT):( lactate threshold ), gas exchange threshold : an estimator of the onset of lactic acidosis under stress or exercise condition, which is a form of metabolic acidosis with anaerobic energy utilization. The normal AT values are about 40-60% of peak VO2.
3. Respiratory Exchange Ratio (RER) = VCO2/VO2, ratio between CO2 output and O2 uptake, it is the maximal exercise intensity. RER more than 1.1 means a state of maximal efforts and exhaustion. It considers now the best non-invasive indicator of maximal exercise intensity. It helps to differentiate cardiac and non-cardiac causes of exercise limitations, fatigue before reaching anaerobic threshold.
4.Pulmonary ventilation (VE): the volume of air moved in and out of the lungs. It is the RR product by the volume of air exhaled at every cycle (tidal volume).
CPET can obviate different changes with phenotyping of factors influencing cardiovascular risk factors:
– Exercise test can be used as a tool for assessment of heart and lung functions as it evaluates O2 delivery to the tissues and neuromuscular system efficiency, exercise intolerance indicates a problem in these systems.
With stress, it is possible for good assessment of functional reserve in non invasive dynamic interactive and reliable way.
The most important parameters of assessment are :
-Vo2 peak which is the highest value of oxygen uptake reached following exhausting exercise; value < 85% of predicted value is abnormal.
– Anaerobic threshold is the maximum level of exercise VO2 which produce aerobic energy. normal range is 40–65% of peak VO2
-Respiratory exchange ratio (VCO2- CO2 output/VO2-O2 uptake). Accepted value is ≥1.10.
-A review article with level of evidence 5.
Assessment of Exercise Intolerance in Patients with Pre-Dialysis CKD with Cardiopulmonary Function Testing: Translation to Everyday Practice
CPET is The gold standard for identifying exercise limitation .CPET provides an integrative evaluation of cardiovascular, pulmonary, hematopoietic, neuropsychological, and metabolic function during maximal or submaximal exercise.
CEPT allows the assessment of the physiological reserves of these systems that are not adequately reflected through the measurement of individual organ system at rest.
Indications of CPET include:
(a) evaluation of exercise capacity.
(b) evaluation and differential diagnosis of exercise intolerance.
(c) eval- uation of disability.
(d) designing the rehabilitation pro- gram and assessing its efficacy.
(e) preoperative evaluation.
(f) functional and prognostic evaluation of patients with heart diseases.
(g) functional and prognostic evalua- tion of patients with respiratory disorders, and
(h) assessing treatment efficacy .
Commonly measured variables are :
VO2max (in mL/min or L/min)
VO2peak (in mL/min or L/min)
RER
VE
Ventilatory equivalents for O2 (VE/VO2) and CO2 (VE/VCO2)
VE-VCO2 slope PETCO2 (in mmHg) AT or VT
Oxygen pulse (VO2/HR) (in mL of O2/min/bpm)
ΔVO2/ΔWR relationship (VO2 in mL/min and workload in watts)
Respiratory reserve (VE/MVV) (both VE, MVV in L/min)
IC (L or mL)
Potential Clinical Applications of CPET in Patients with CKD:
CPET is the optimal tool in the differential diagnosis of conditions associated with re- duced cardiovascular reserve, it may help towards the identification of previously “hidden” causes of poor exercise capacity in patients with pre-dialysis CKD, such as respiratory functional disturbances and neuromuscular disorders
CPET use, through discrimination of the underlying causes of physical impairment and exertional fatigue in CKD patients, who suffer from multiple comorbidities, may facilitate treatment optimization towards symptom relief and functional capacity improvement.
CPET could be used to identify individuals with impaired exercise tolerance that would benefit from intervention.
it can provide valuable information before the initiation of training. i.e., determine the optimal training intensity level and exercise safety, and after program completion, i.e., evaluate the efficacy of the intervention .
CPET is also used for several years in preoperative evaluation of different patient groups, including patients before heart surgery or organ transplantation (including heart, lung, and liver)
CPET information can be used to inform the decision-making and consent processes, to direct preoperative interventions, intraoperative anesthetic practice, prehabilitation, and rehabilitation, as well as to estimate the likelihood of perioperative morbidity and mortality.
CPET is currently used for long-term risk stratification in a wide range of populations, such as patients with lung diseases and heart failure.
Level of evidence is 5
This new CPET is an emerging new investigation which is becoming one of the most important tests in detecting Cardiac and non-cardiac causes in CKD patients.
As in this type of test you can reach the exact cause of intolerance in CKD patients.
in CKD patients and by doing this test we can assess the actual cardiac function, arterial stiffness and endothelial problems.
The most important parameters derived by the CPET:
VO2max and VO2peak.
Respiratory Exchange Ratio.
Ventilatory equivalents for O2 (VE/VO2) and CO2 (VE/VCO2).
VE-VCO2 slope.
PETCO2: The partial pressure of carbon dioxide at the end of expiration.
Anaerobic Threshold: The point at which minute ventilation increases disproportionately relative to VO2.
Oxygen pulse (VO2/HR): the ratio between VO2 and the heart rate.
ΔVO2/ΔWR relationship: It is the relationship between VO2 and workload.
Respiratory reserve (VE/MVV): It is the ratio between maximum VE and MVV assessed at rest.
IC: It is the maximum amount of air that can be expired after a normal exhalation.
Level of evidence is class 5.
1- CPET can delineate multisystem changes and offer comprehensive phenotyping of factors determining overall cardiovascular risk”. Please read this article and explain how the authors reaches this conclusion
CPET , cardiopulmonary exercise testing, is an integrated way of assessment of the function of multiple system during exercise. It involves different parameters that are assessed during exercise. The author mentioned some studies with the following conclusions:
· Arterial stiffness and eGFR were independently associated with VO2peak
· Patients with low FMD , flow-mediated dilation, (lower than the common median FMD value) had significantly poorer exercise capacity.
· When CPET was performed before and after a cardiac rehabilitation program, VO2peak and the work rate improved significantly after 3-month cardiac rehabilitation.
So, the CPET can help determining the cardiopulmonary phenotype of patients with CKD as it assesses the maladaptive physiological responses that can affect exercise. It can help differentiating cardiac from non-cardiac causes of poor exercise capacity. These include respiratory functional disturbances and neuromuscular disorders.
CKD had lower predicted VO2peak, VO2max, lower peak heart rate, lower AT, impaired heart rate recovery and deterioration of exercise tolerance with advancing CKD. So, CPET can define the causes of physical impairment in CKD patients with multiple comorbidities. This will help in providing the optimum therapy according to the underlying cause
2- What are the most important parameters derived by the CPET?
The parameters derived by CEPT are many including VO2max ,VO 2peak , respiratory exchange ratio, VE , Ventilatory equivalents for and CO2 ,VE-VCO2 slope , anaerobic threshold,PETCO2 , Oxygen pulse , ΔVO2/ΔWR relationship , Respiratory reserve, inspiratory capacity. The most important ones are
· VO2 and Peak Oxygen Uptake which refer to the O2 volume per time unit that is extracted from the air. This is considered the gold standard test in patients with many cardiopulmonary situations like HF, COPD ,pulmonary hypertension, hypertrophic cardiomyopathy, restrictive pulmonary disease and physical fitness level .
· The anaerobic threshold ( lactate threshold, lactic acid threshold, or gas exchange threshold) estimate the lactate acidosis onset due to exercise. This will differentiate between cardiac and noncardiac exercise limitation causes as the anaerobic threshold fatigue is associated with cardiac causes
· Respiratory exchange ratio estimates the maximal exercise intensity by calculating the ratio between CO2 output and O2 uptake
3- What is the level of evidence provided by this article?
This paper represents the opinion of respected authorities based on descriptive studies. So the level is V.
“CPET can delineate multisystem changes and offer comprehensive phenotyping of factors determining overall cardiovascular risk”.
This was concluded after examining different parameters of exercise testing and specific cardiorespiratory variables, with a large volume of physiological data being assessed to adequately estimate expected organ and further system response in coupling external respiration to cellular respiration during exercise.
The most important variables used during CPET are:
VO2 and Peak Oxygen Uptake, which is considered the most sensitive universal marker and the gold standard laboratory measure of cardiorespiratory fitness as well as the most important measurement required during the functional exercise testing.
It can indicate disease severity in those suffering heart failure, pulmonary hypertension, hypertrophic cardiomyopathy, chronic obstructive pulmonary disease, and restrictive pulmonary disease, besides level of physical fitness.
Anaerobic Threshold level is an estimate of the onset of metabolic acidosis manifested by the rising rate of arterial lactate concentration resulting during exercise. It is also has other synonyms as lactate threshold, lactic acid threshold, or gas exchange threshold. The AT is used to assist in differentiating cardiac and noncardiac reasons of exercise limitation as for example fatigue before reaching AT mostly indicates noncardiac reasons.
Respiratory Exchange Ratio, is now being considered the best noninvasive indicator of maximal exercise intensity. It is an expression of the ratio between CO2 output and O2 uptake (VCO2/VO2).
CKD patients are considered special population whereas their oxygen-carrying capacity is low, so hemoglobin (Hgb) level is an important parameter must be highlighted then .A 3 g/dL drop in Hgb level is associated with total oxygen-carrying capacity decline by 4 mL per 100 mL blood.
So, it can be used to evaluate exercise capacity, differential diagnosis of exercise intolerance, disability, rehabilitation program efficacy, preoperative as well as functional and prognostic evaluation of patients with heart diseases and respiratory disorders along with their treatment efficacy.
The most important parameters derived by the CPET:
VO2max and VO2peak.
Respiratory Exchange Ratio.
Ventilatory equivalents for O2 (VE/VO2) and CO2 (VE/VCO2).
VE-VCO2 slope.
PETCO2: The partial pressure of carbon dioxide at the end of expiration.
Anaerobic Threshold: The point at which minute ventilation increases disproportionately relative to VO2.
Oxygen pulse (VO2/HR): the ratio between VO2 and the heart rate.
ΔVO2/ΔWR relationship: It is the relationship between VO2 and workload.
Respiratory reserve (VE/MVV): It is the ratio between maximum VE and MVV assessed at rest.
IC: It is the maximum amount of air that can be expired after a normal exhalation.
Level of evidence is class 5.
CPET able to assess the following aspects
1. exercise capacity and the differential diagnosis of exercise intolerance.
2. Evaluation of disability besides designing the rehabilitation program and assessing its efficacy.
3. Premorbid cardiac function and prognostic evaluation among patients with heart diseases.
4. Prognostic evaluation of patients with respiratory disorders and lung function.
Most important parameters derived by the CPET.
1) VO2 and Peak Oxygen Uptake
VΟ2peak has become the “gold standard” investigation parameter for cardiorespiratory
function and the most important measurement for functional exercise assessment.
2) Anaerobic Threshold
Differentiating cardiac and noncardiac causes of exercise limitation
3)Respiratory Exchange Ratio
Best noninvasive indicator of maximal exercise intensity.
Level 5 evidence review.
First question
CKD patients are at increased risk for cardiovascular events due to presence of classical factors as DM ,HTN , dyslipidemia, smoking, obesity and non classical factors as anemia and disorders in calcium phosphate metabolism .
Due to presence of all these factors in CKD patients, CKD patients have decreased cardiorespiratory fitness compared to general population and also they have increased aortic stiffness , LVH
Exercise intolerance mainly related to cardiac function disturbance, endothelial dysfunction arterial stiffness, muscle disorders.
Cardiopulmonary Exercise testing is used for assessment of cardiovascular, Pulmonary, muscular and neurophysiological responses during Exercise and this is a gold standard test for assessment peak and submaximal Exercise response .
CPET is the optimal tool in the DD of conditions associated with reduced cardiovascular resrve and can identify hidden causes of poor Exercise tolerance in CKD patients such as respiratory disorders and neuromuscular disturbances.
Second Question
The most important parameters derived by the CPET
VO2 peak : it is the highest value of oxygen uptake reached at the end of an exhausting exercise test .
Anaerobic threshold: an estimator of the onset of metabolic acidosis caused by the increased rate of arterial lactate concentration during Exercise
Respiratory Exchange Ratio : the ratio between Co2 output and O2 up take . It is indicator of maximal Exercise intensity
Third question
Literature review. Level 5
CPET is composed by the evaluation of certain parameters extracted during the exercises that make up the program. The parameters studied allow the evaluation of the relationship between physiological responses and physical performance and and later the relationship of these data with the cardiac risk of each population
Among the parameters studied, the most important are:
– VO2 and Peak Oxygen Uptake
– Anaerobic Threshold
– Respiratory Exchange Ratio
This article is a narrative reviews, so your level of evidence is 5.
CPET provides an integrative evaluation of cardiovascular, pulmonary, hematopoietic, neuropsychological, and metabolic function during maximal or submaximal exercise. It is useful in clinical setting for differentiation of the causes of exercise intolerance, risk stratification, and assessment of response to relevant treatments.
Parameter measured
1. VO2max (in mL/min or L/min) The product of the highest CO and arterial and venous O2 content difference (A − V) O2, VO2max = COmax × (A − V) O2max
2. VO2peak (in mL/min or L/min) The highest value obtained at the end of an exercise test to exhaustion
3. RER The ratio of CO2 production and O2 consumption (VCO2/VO2)
4. VE The product of RR by the volume of air exhaled at every respiratory cycle (tidal volume, Vt)
5. Ventilatory equivalents for O2 (VE/VO2) and CO2 (VE/VCO2) The ratio of pulmonary ventilation and O2 consumption (VE/VO2) or the ratio of pulmonary ventilation and CO2 production (VE/VCO2)
6. VE-VCO2 slope The relationship between VE (plotted in the y-axis), and VCO2 (plotted in the x-axis)
7. PETCO2 (in mmHg) The carbon dioxide partial pressure at the end of expiration
8. AT or VT It is defined as the point at which minute ventilation increases disproportionately relative to VO2
9. Oxygen pulse (VO2/HR) (in mL of O2/min/bpm) It is the ratio between VO2 and the heart rate
10. ΔVO2/ΔWR relationship (VO2 in mL/min and workload in watts) It is the relationship between VO2 and workload. It is measured during exercise on a cycle ergometer with a ramp protocol
11. Respiratory reserve (VE/MVV) (both VE, MVV in L/min) It is the ratio between maximum VE and MVV assessed at rest
12. IC (L or mL) It is the maximum amount of air that can be expired after a normal exhalation
Level of evidence: 5
“CPET can delineate multisystem changes and offer comprehensive phenotyping of factors determining overall cardiovascular risk”.
Please read this article and explain how the authors reaches this conclusion
CPET evaluates all the involved systems during exercise which include heart, lung, muscles, nerves and joints. It evaluates the exercise capacity of individuals and predicts the overall risk of all cause related mortality and cardiovascular related mortality.
CPET is a non-invasive test that can be used to differentiate causes of exercise intolerance, evaluate risk stratification and assess the response to proposed treatments and therapies. It depends on analyzing the expired air (breath by breath) during exercise so exercise capacity can be evaluated, disabilities can be detected, rehabilitation program can be designed, pre-operative and intra-operative interventions can be planned.
CPET is indicated to assess patients with heart and lung disorders.
CKD patients usually have low cardio-pulmonary health (as evidenced with CPET using studies) compared to general population.
What are the most important parameters derived by the CPET?
1- VO2max = maximum oxygen uptake
2- VO2peak= peak oxygen uptake;
3- RER, respiratory exchange ratio = VCO2/VO2 ratio.
4- CO, cardiac output.
5- IC, inspiratory capacity;
6- AT, anaerobic threshold.
7- VT, ventilatory threshold.
8- PETCO2, end-tidal CO2 partial pressure.
9- VE, Ventilatory equivalent for O2 and CO2.
10- VE, ventilation during exercise.
11- MVV, maximum voluntary ventilation.
12- RR, respiratory rate.
What is the level of evidence provided by this article?
Level 5 evidence
In the assessment , evaluation and preparation of CKD S 5 +/- dialysis for conducting transplantation, we should be sure that the patient has no failure of the most vital organ (cardiopulmonary system ) .
As we know that disaeas of the heart affect the kidneys , and vise versa , the CKD patient have 25% more risk factor of developing cardiovascular events and death .
So assessment of cardiopulmonary systems is vital to obtain a successful transplantation and graft function and by the end of the day , to improve quality of life of the recipient .
@ How the studies reach the conclusions:
All randomize trials using CPET in patient with pre-dialysis CKD ,(studies of program of sxcercise training ).
Results of metanalysis show pooled estimates of improved VO2 peak/VO@ max with physical rehabilitation program
CPET is the most valuable test of assessing exercise capacity and limitation of the recipient , as cardiopulmnary and associated condition (DM , vascular affection ..etc) assessment involved in any evaluation take high percentage of parameters of scores and indexes , eg (40% of charlson comorbidity index) .
CEPT parameters:
VO2max: COmax*(A-V)O2max.
VO2 peak
RER: VCO2/VO2.
VE/VO2 & VE/VCO2.
VE-VCO2 slop.
PETCO2.
AT or VT.
VO2/HR
change in VO2/ change in WA relationship.
VE/MVV.
IC (max amount of air expired after normal exhalation.
What is the level of evidence provided by this article?
Level 5.
Author conclusion result from:
CEPT parameters:
Review article, level 4.
sorry, level 5
CPET not CEPT
CPET can delineate multisystem changes and offer comprehensive phenotyping of factors determining overall cardiovascular risk”. Please read this article and explain how the authors reaches this conclusion?
– chronic kidney disease is a public health problem about 9% of world population increasing to 12% in western countries all those associated with increase risk to cardio-vascular disease which associated increased risk factor ( age, diabetes, hypertension, dyslipidemia , smoker and obesity) and other non classical risk factor as anaemia and calcium and phosphorus disturbances which leads to low cardiopulmonary fitness.
– cardiopulmonary exarase testing is noninvasive technique used clinical setting for diagnosis and evaluations it is provide integrative assessment of cardiopulmonary muscular – and neurological during exercises, allows assessment of physiological reserve which cannot be done at rest.
Most common use CPET indexes.
-VO2 and peak oxygen uptake.
-Anerobic threshold.
-Respiratory exchange ratio.
* physiology of exercise and tick equation:-
According to fick equation , VO2 =(SV xHR)x (CaO2- CvO2)
exercise intolerance is the presence of abnormal low VO2 peak of any cause s according to pick equation any factor impair cardiac output leads to decreased VO2 peak.
– randomizes trial used. CPET suggest significant improvement in physical performance of chronic Kidney disease patients. Following exercise intervention
VO2 and peak oxygen uptake.
-Anerobic threshold.
-Respiratory exchange ratio.
What is the level of evidence provided by this article?
Level 5.
Q1
Assessment of Exercise Intolerance in Patients with Pre-Dialysis CKD with Cardiopulmonary Function Testing: Translation to Everyday Practice
CKD has high incidence and prevalence of about 10% in population. Ti is afifth leading cause of death .
CPET It is a gold standard for identifying cardiopulmonary exercise limitation .
It provides an integrative assessment of cardiovas cular, pulmonary, hematopoietic, neuropsychological, and metabolic function during maximal or submaximal exercise.
It is beneficial for differentiation of the causes of exercise intolerance, risk stratification, and assessment of response to t treatments.
This noninvasive, dynamic test permits the evaluation of exercise responses, help physician in decision making .
During CPET, large number of variables are used ( “routine” exercise testing and sophisticated cardiorespiratory
parameters are used to assess each organ system contribution to exercise intolerance ) .
each organ system
response is assessed :-
1- external respiration ( oxygen uptake (VO2) and carbon dioxide output at the airways)
2- cellular respiration (i.e., oxygen consumption and carbon production), during exercise.
Indications of CPET include:
(a) evaluation of exercise capacity,
(b) evaluation and differential diagnosis of exercise intolerance,
(c) evaluation of disability,
(d) designing the rehabilitation program and assessing its efficacy,
(e) preoperative evaluation,
(f) functional and prognostic evaluation of patients with heart diseases,
(g) functional and prognostic evaluation of patients with respiratory disorders,
(h) assessing treatment efficacy [25].
Q2-
Commonly measured variables during CPET are the following .
Parameter measured (units) Definition
1- VO2max (in mL/min or L/min)
The product of the highest CO and arterial and venous O2 content difference (A − V) O2,VO2max = COmax × (A − V) O2max
2- VO2peak (in mL/min or L/min)
The highest value obtained at the end of an exercise test to exhaustion
3- RER
The ratio of CO2 production and O2 consumption (VCO2/VO2)
4- VE
The product of RR by the volume of air exhaled at every respiratory cycle (tidal volume, Vt)
5- Ventilatory equivalents for O2 (VE/VO2) and CO2 (VE/VCO2)
The ratio of pulmonary ventilation and O2 consumption (VE/VO2) or the ratio of pulmonary ventilation and CO2 production (VE/VCO2)
6- VE-VCO2 slope
The relationship between VE (plotted in the y-axis), and VCO2 (plotted in the x-axis)
7- PETCO2 (in mmHg)
The carbon dioxide partial pressure at the end of expiration
8- AT or VT
It is defined as the point at which minute ventilation increases disproportionately relative to VO2
9- Oxygen pulse (VO2/HR) (in mL of O2/min/bpm)
It is the ratio between VO2 and the heart rate
10- ΔVO2/ΔWR relationship (VO2 in mL/min and workload in watts)
It is the relationship between VO2 and workload. It is measured during exercise on a cycle ergometer with a ramp protocol
11- Respiratory reserve (VE/MVV) (both VE, MVV in L/min)
It is the ratio between maximum VE and MVV assessed at rest IC (L or mL) It is the maximum amount of air that can be expired after a normal exhalation
Q3 –
Evidence level 5 .
Q1.
Nowadays the incidence of CKD is increasing and due to its cardiovascular complications, CV evaluation in this population is very important.
The gold standard for of exercise intolerance evaluation is CEPT that assesses heart, lungs muscles and neuropsychological responses in details by measurement of many variables such as; VO2 max, VO2 peak, RER (VCO2/ VO2), VE, VE/ VO2, VE/ VCO2, VE- VCO2 slope, PET CO2, AT or VT.
Fick equation says that: VO2: (SVXHR) x (CaO2- CVO2) in exercise
VO2 max = [(SV max) x (HR max)] x [(CaO2 max) – (CVO2 min)] and an abnormal low VO2 peak means exercise intolerance. CKD patients had lower VO2 peak, HR and AT compared to healthy controls that deteriorates with progression of the disease. Those patients showed some improvement with exercise training on CPET parameters such as VO2 peak/ VO2 max in a meta- analysis. CPET provide a wide range of cardiopulmonary assessment with increasing exercise and provides breath –by- breath gas exchange and nervous and muscular system in addition to cardiorespiratory systems.
This could be helpful for treatment and intervention. CPET could determine intensity level for exercise which can be tolerated by these patients. CPET could determine intraoperative anesthesia, preoperative intervention and its mortality and morbidity. VO2 peak and VO2 AT are variables of CPET which have high prognostic value before kidney TX and can predict the risk of hospitalization or all-cause mortality more in CKD patients because it is associated with other vascular components such as arterial stiffness and endothelia function. CPET could help for differential diagnosis of exercise intolerance and risk stratification.
Q2:
VO2 and peak oxygen uptake: VO2 means the volume of O2 which is extracted from air during ventilation and express by ml/ min.
VO2 peak is the highest one reached at the end of exercise test and is gold standard for measurement of cardiorespiratory fitness.
AT (Anaerobic Threshold): is the VO2 which is an estimator for the onset of metabolic acidosis.
* Respiratory Exchange Ratio (VCO2/ VO2) : the ratio between CO2 output and O2 uptake. Values. more than 1 shows intense exercise
Q3:
level of evidence is 5 (Review article)
CKD currently lists among the fastest growing global causes of death and is projected to become the fifth global cause of death by 2040.
Cardiovascular disease is the most common cause of death in patients with CKD
Classical cardiovascular risk factors including the following
1-age
2-hypertension
3-diabetes mellitus
4- dyslipidemia
5-obesity
6-smoking
nonclassical risk factors relevant to CKD and the uremic environment per se (i.e.
1-anemia
2-disturbed metabolism of calcium and phosphate
These factors are highly prevalent in patients with CKD and also contribute to the risk of developing cardiovascular disease. Therefore, cardiovascular complications are the principal cause of death in patients with CKD
Cardiorespiratory fitness reflects the ability of the cardiovascular and respiratory systems to transport oxygen to the working muscles of the human body during physical activity.
Impaired cardiorespiratory fitness is strongly associated with early all-cause and cardiovascular-related mortality
Patients with CKD have lower cardiorespiratory fitness than the general population; this occurs early in the disease process, declines further with renal function drop, and is also associated with increased aortic stiffness, poor left ventricular function, and higher risk of cardiovascular events . Thus, exercise intolerance, a prognostic factor of morbidity and mortality, is inherently associated with CKD.
The ability of these patients to exercise can be related to a number of factors, including cardiac function disturbances, endothelial dysfunction, arterial stiffness, morphological and functional abnormalities of skeletal muscles, dysautonomia of nervous system, anemia, depression, and others. The above-mentioned causes lead these patients to inactivity, diminished functional capacity, feeling of fatigue, social isolation, and finally, low quality of life .
Cardiopulmonary exercise testing (CPET) is a dynamic, noninvasive technique that is useful in various clinical settings for diagnosis, risk stratification, and the evaluation of response to cardiopulmonary therapies
It is long considered to be the gold standard for evaluating the degree and differentiating the causes, by unmasking physiological mechanisms of exercise intolerance
Cardiopulmonary Exercise Testing
CPET provides an integrative assessment of the cardiovascular, pulmonary, muscular, and neuropsychological responses during exercise; this allows the assessment of the physiological reserves of these systems that are not adequately reflected through the measurement of individual organ system at rest
Indications of CPET include:
(a) evaluation of exercise capacity
(b) evaluation and differential diagnosis of exercise intolerance
(c) evaluation of disability
(d) designing the rehabilitation program and assessing its efficacy
(e) preoperative evaluation
(f) functional and prognostic evaluation of patients with heart diseases
(g) functional and prognostic evaluation of patients with respiratory disorder
(h) assessing treatment efficacy
Most Commonly Used CPET Indexes
1-VO2 and Peak Oxygen Uptake VO2 is the volume of O2 extracted from the air inhaled during pulmonary ventilation in a period of time.
It is usually expressed in mL/min or L/min. Historically, the VO2 plateau demonstrated by a series of high intensity constant work-rate tests was used to define maximum VO2 (VO2max), in healthy individuals. However, the flattening of the VO2-work rate relationship is often not seen during incremental exercise tests; thus, VO2max is defined as the highest VO2 attainable for a given form of exercise, as evidenced by a failure for VO2 to further increase, despite a progressive increase in work rate. In practice peak VO2 (VO2peak), that is the highest value reached at the end of an exhausting exercise test, is used alternatively to VO2max, both in healthy individuals and diseased populations . Mean values at intervals of 10-60 s should be measured depending on the protocol (short-interval means for protocols with short stages and longer interval means for protocols with longer stages)
VO2peak is considered abnormal when below 85% of the predicted value
VΟ2peak has become the “gold standard” laboratory measure of cardiorespiratory fitness and the most important measurement during the functional exercise testing. It has been used as a universal marker, which can reflect disease severity in patients with heart failure, pulmonary hypertension, hypertrophic cardiomyopathy, chronic obstructive pulmonary disease, and restrictive pulmonary disease, in addition to physical fitness level
2-Anaerobic Threshold
The anaerobic threshold (AT) (Fig. 1), also known as the lactate threshold, lactic acid threshold, or gas exchange threshold, is considered an estimator of the onset of metabolic acidosis caused predominantly by the increased rate of arterial lactate concentration during exercise.
The normal mean AT values expected for adults are around 40–65% of peak VO2 .The AT is calculated with the V-slope method; when VCO2 is plotted against VO2, their relationship is composed of 2 linear components, the lower of which has a slope of less than 1 and the upper has a slope steeper than 1. The intercept of these 2 slopes is the AT
The ability to achieve the AT can assist in differentiating cardiac and noncardiac causes of exercise limitation; fatigue before reaching AT is likely related to noncardiac causes
3-Respiratory Exchange Ratio
It expresses the ratio between CO2 output and O2 uptake (VCO2/VO2). It is currently the best noninvasive indicator of maximal exercise intensity. Values above 1.0 can reflect intense exercise, but those ≥1.10 are those searched on CPET, and have been accepted as a parameter of maximal effort/exhaustion
In general, since the subject is exercising in the laboratory under close monitoring and with resuscitation measures readily available, there are only a few absolute contraindications for the conduction of CPET, even in patients with multiple comorbidities. The most important refer to acute or uncontrolled cardiovascular conditions (e.g., syncope, unstable angina, uncontrolled heart failure, acute myocardial infarction, and acute pulmonary embolism), serious cardiac dysrhythmias on resting ECG or severe respiratory failure (rest oxygen saturation, sPO2 ≤85%). Severe electrolyte abnormalities and uncontrolled hypertension at rest (>200 mm Hg systolic, >120 mm Hg diastolic), which may be established among CKD patients are relative contraindications, along with severe pulmonary hypertension and serious valvular disorders. Finally, subjects with orthopedic or neurologic disorders, are also not ideal candidates for CPET
4-Physiology of Exercise and Fick Equation At rest, the metabolic processes of the human body are met primarily through aerobic metabolism. During activity, an increase in VO2 is required to meet the metabolic demand of the working muscle. Initially, increasing VO2 is largely dependent on the rate and amount of oxygen delivered to exercising muscle, a function of the cardiac output, oxygen carrying capacity of the blood, and vascular convective transport
Once oxygen is delivered to the working muscle, VO2 is dependent on oxygen utilization properties of the skeletal muscle
As long as the activity intensity levels remain light to moderate, aerobic metabolism effectively matches the energy demand [36]. High intensity exercise, though, is limited by the capacity of aerobic metabolism and often results in VO2 rising to its most tolerable limit, due to symptomrelated fatigue that causes the individual to stop the activity
5-Exercise Intolerance Exercise intolerance (or decreased exercise capacity) is defined by the presence of abnormally low VO2peak, of any cause. Based on the Fick equation, any factor that may impair maximum cardiac output (e.g., heart failure) or affect arterial or mixed venous oxygen content (e.g., diseases of the lungs, skeletal muscle dysfunction, or anemia) may result to decreased VO2peak
CPET Studies in Patients with Pre-Dialysis CKD
various studies aimed to quantify the cardiovascular reserve of CKD patients who were not on renal replacement therapy or kidney transplanted using the CPET technology. In the following lines, existing studies using CPET in patients with non-dialysis CKD are described, categorized by type of design; observational studies, and randomized trials.
A few early studies used CPET in small samples of predialysis CKD patients to evaluate exercise tolerance in association with other cardiovascular factors
Studies Comparing CPET Parameters in CKD Patients of Various Stages with Controls In a cross-sectional analysis, Nelson et al. [42] used CPET in 93 CKD stage 3 patients, in comparison to 840 individuals with renal function >60 mL/min/1.73 m2. Patients with CKD had lower predicted VO2peak, lower peak heart rate, lower AT, and impaired heart rate recovery.
Studies Examining CPET Parameters in Relation to Vascular Function Measures
Two studies investigated whether endothelial dysfunction or arterial stiffness are associated with exercise capacity in CKD patients. Van Craenenbroeck et al.evaluated 63 patients with CKD divided in 2 eGFR groups, both of which displayed significantly lower VO2peak and VO2AT
Arterial stiffness measured with pulse wave velocity (β = −0.301, p = 0.01) and eGFR (β = 0.363, p = 0.002) were independently associated with VO2peak in multiple regression analysis. In the second study, Downey et al. [46] examined exercise capacity in 38 CKD patients divided into 2 groups according to flow-mediated dilation (FMD) levels.
Studies Examining the Reproducibility of CPET Testing Wilkinson et al.
tried to determine the reliability and the estimated minimal detectable change of CPET and other physical function tests in 41 patients with pre-dialysis CKD. Assessments were performed at 2 time points (test 1 and 2) separated by a 6-week period in which patients were instructed to maintain their habitual lifestyle. There was minimal difference between the 2 CPET tests (intraclass correlation coefficient [r] 0.866) and all the other tests examined, with the exception of sit-to-stand test-5.
Randomized Trials Using CPET in Non-Dialysis CKD Patients
All randomized trials using CPET in patients with predialysis CKD have studied the effects of programs of exercise training. Among these trials, several suggest significant improvement of physical performance of CKD patients following exercise interventions. The earliest of positive studies which showed significantly improved VO2peak and endurance time in the exercise group, randomized 20 pre-dialysis CKD patients in a 12-month exercise program or standard care
Potential Clinical Applications of CPET in Patients with CKD
CPET is a highly useful clinical tool that evaluates organ-specific maladaptive physiological responses which may limit physical performance. It provides breath-bybreath gas exchange measures while progressively increasing exercise intensity in a linear function over time to maximally stress the oxygen delivery and utilization system
CPET may have a wide range of clinical applications that can help to better characterize the cardiopulmonary phenotype of patients with CKD. As discussed above, exercise limitation in patients with CKD can be attributed to a wide variety of coexisting disorders of the cardiac, respiratory, nervous, and muscular systems that can be directly or indirectly linked with reduced renal function
CPET may help towards the identification of previously “hidden” causes of poor exercise capacity in patients with pre-dialysis CKD, such as respiratory functional disturbances and neuromuscular disorders
CPET use, through discrimination of the underlying causes of physical impairment and exertional fatigue in CKD patients, who suffer from multiple comorbidities, may facilitate treatment optimization towards symptom relief and functional capacity improvement. Furthermore, as exercise training has shown to improve physical function and walking capacity among subjects with CKD
CPET could be used to identify individuals with impaired exercise tolerance that would benefit from intervention. In addition, it can provide valuable information before the initiation of training, i.e., determine the optimal training intensity level and exercise safety, and after program completion, i.e., evaluate the efficacy of the intervention
CPET is also used for several years in preoperative evaluation of different patient groups, including patients before heart surgery or organ transplantation (including heart, lung, and liver)
CPET information can be used to inform the decision-making and consent processes, to direct preoperative interventions, intraoperative anesthetic practice, prehabilitation, and rehabilitation, as well as to estimate the likelihood of perioperative morbidity and mortality
CPET is currently used for long-term risk stratification in a wide range of populations, such as patients with lung diseases and heart failure. For example, in patients with chronic obstructive pulmonary disease, CPET has been used to predict the risk of all-cause mortality, independently of lung function indices while in patients with heart failure, CPET offers incremental value beyond clinical characteristics and ejection fraction in predicting the risks of hospitalization and mortality
CPET parameters are associated with relevant outcomes and, as such, they can be used for risk stratification with regards to perioperative complications or long-term cardiovascular and all-cause mortality in patients with CKD
Conclusion
CPET has been used in pilot observational studies that, in most cases, examine exercise capacity in patients with CKD versus non-CKD controls and, in some cases evaluate simple associations with other vascular parameters, such as endothelial function and arterial stiffness. In addition, CPET has been used in randomized trials examining the effect of exercise training interventions on cardiovascular reserve in patients with CKD, in order to obtain an objective measure of exercise tolerance.
CPET in patients with pre-dialysis CKD in order to examine its diagnostic accuracy for underlying diseases, to delineate the associations of CPET indexes with cardiac and vascular parameters that represent well-known cardiovascular risk factors, as well as to directly assess the prognostic significance of CPET derived indexes for hard outcomes, can be particularly useful in order to establish CPET as a valid diagnostic and prognostic tool for the benefit of our patients.
level V
The author described several studies, including Observational Studies and randomized Using CPET in CKD-Non-Dialysis patients.
Observational studies such as, Studies Comparing CPET Parameters in CKD Patients of Various Stages with Controls
Also he described the studies which examine the parameters in relations to different factors such as Studies Examining CPET Parameters in Relation to Vascular Function Measures, Studies Examining the Efficacy of Exercise Programs, Studies Examining the Reproducibility of CPET Testing.
And the Randomized Trials Using CPET in Non-Dialysis CKD Patients, many of them which proves significant improvement of physical performance of CKD patients following exercise interventions.
He started his article with introduction showing the increase incidence and prevalence of CKD and the increased mortality in this population due to cardiovascular events, this signify importance of early detection of the cardiovascular impairment in ckd patient to reduce mortality. One of the promising techniques could be CPET.
. Ckd is projected to be the 5th global cause of death by 2040 ,the increased mortality in these population is attributed to increased cardiovascular complications.
Chronic kidney disease is associated with increased cardiovascular risk and subsequently leading to death. This is mostly due to their reduced cardiovascular reserve and decrease exercise tolerance.
Cardiopulmonary exercise testing is a new technique which carries great value in identifying the problem and degree of exercise limitations.
CPET is a unique way to evaluate multisystem, including cardiovascular , pulmonary ,hematopoietic, neuropsychologic and metabolic function. During exercise.
It plays great role in clinical practice to differentiate the causes of exercise intolerance and assess the response to treatment.
The increased cardiovascular mortality is attributed to impaired cardiorespiratory fitness in this population. CKD patients are prone for cardiorespiratory impaired tolerance which starts early in the course of CKD due to aotic stiffness, poor ventricular function , and this increases with advancing stages of CKD.
The poor exercise tolerance of ckd patients is mostly due to
1- cardiac function disturbances,
2- endothelial dysfunction
3- arterial stiffness
4- morphological and functional abnormalities of skeletal muscles
5- dysautonomia of nervous system
6- anemia
7- depression
subsequently leading to inactivity, reduced functional capacity, fatigued, social isolation, and finally, low quality of life
CPET is a dynamic non invasive technique to evaluate cardio-pulmonary function and response to therapy. It identifies the degree in addition to causes of the impairment.
The principle of CPET is, system failure occurs while the system under stress. Hence it Identifies if the cause is respiratory or cardiac. It used to determine functional capacity and impairment
Indications of CPET
(a) evaluation of exercise capacity,
(b) evaluation and differential diagnosis of exercise intolerance
(c) evaluation of disability
(d) designing the rehabilitation program and assessing its efficacy
(e) preoperative evaluation
(f) functional and prognostic evaluation of patients with heart diseases
(g) functional and prognostic evaluation of patients with respiratory disorders
(h) assessing treatment efficacy
measured variables during CPET
1- VO2max (in mL/min or L/min) : The product of the highest CO and arterial and venous O2 content difference (A − V) O2,
2- VO2peak (in mL/min or L/min) :The highest value obtained at the end of an exercise test to exhaustion
3- RER: The ratio of CO2 production and O2 consumption (VCO2/VO2)
4- VE :The product of RR by the volume of air exhaled at every respiratory cycle (tidal volume, Vt)
5- Ventilatory equivalents for O2 (VE/VO2) and CO2 (VE/VCO2)
6- The ratio of pulmonary ventilation and O2 consumption (VE/VO2) or the ratio of pulmonary
7- ventilation and CO2 production (VE/VCO2)
8- VE-VCO2 slope: The relationship between VE (plotted in the y-axis), and VCO2 (plotted in the x-axis)
9- PETCO2 (in mmHg) The carbon dioxide partial pressure at the end of expiration
10- AT or VT It is defined as the point at which minute ventilation increases disproportionately relative to
11- VO2
12- Oxygen pulse (VO2/HR) (in mL of O2/min/bpm) :It is the ratio between VO2 and the heart rate
13- ΔVO2/ΔWR relationship (VO2 in mL/min and workload in watts)
14- It is the relationship between VO2 and workload. It is measured during exercise on a cycle ergometer with a ramp protocol
15- Respiratory reserve (VE/MVV) (both VE, MVV in L/min) : It is the ratio between maximum VE and MVV assessed at rest
16- IC (L or mL): It is the maximum amount of air that can be expired after a normal exhalation
However the most important factors are:
1-VO2 and Peak Oxygen Uptake:
VO2 is the volume of O2 extracted from the air inhaled during pulmonary ventilation in a period of time. It is usually expressed in mL/min or L/min.
VO2peak is considered abnormal when below 85% of the predicted value
2-VO2max is defined as the highest VO2 attainable for a given form of exercise, as evidenced by a failure for VO2 to increase more, despite a progressive increase in work rate. In practice peak VO2 (VO2peak), that is the highest value reached at the end of an exhausting exercise test.
It is used in identifying severe disease in heart failure, pulmonary hypertension, hypertrophic cardiomyopathy, chronic obstructive pulmonary disease, and restrictive pulmonary disease, in addition to identifying physical fitness level.
3-Anaerobic Threshold
The anaerobic threshold (AT) , also known as the lactate threshold, lactic acid threshold, or gas exchange threshold, is the maximum rise in lactate concentration during exercise.
The normal mean AT values expected for adults are around 40–65% of peak VO2.
The ability to achieve the AT can assist in differentiating cardiac and noncardiac causes of exercise limitation; fatigue before reaching AT is likely related to noncardiac causes.
4-Respiratory Exchange Ratio
It expresses the ratio between CO2 output and O2 uptake (VCO2/VO2). It is currently the best noninvasive indicator of maximal exercise intensity. Values above 1.0 can reflect intense exercise, but those ≥1.10 are those searched on CPET, and have been accepted as a parameter of maximal effort/exhaustion
In CKD patient anemia should be taken in consideration while interpretation the results of this study
During methodology (Hgb) level is an issue that should be taken under consideration. Since the oxygen-carrying capacity of the blood depends directly on the level of Hgb, a 3 g/dL decrease in Hgb concentration would result in a reduction of the total oxygen-carrying capacity by 4 mL per 100 mL blood
5
the authors reaches this conclusion by reviewing existing studies using CPET in patients with non-dialysis CKD and categorized by type of design; observational studies, and randomized trials.
Observational Studies Using CPET in Non-Dialysis CKD Patients
Studies comparing CPET parameters in CKD patients of various stages with controls
Faria Rde et al. [43] and other
Studies examining CPET parameters in relation to vascular function measures
Van Craenenbroeck et al. [45] and other
Studies examining the efficacy of exercise programs
Hama et al. [47] and other
Studies examining the reproducibility
Wilkinson et al. [48]
Randomized Trials Using CPET in Non-Dialysis CKD Patients
Eidemak et al. [63]
Leehey et al. [50]
Other
CPET can delineate multisystem changes and offer comprehensive phenotyping of factors determining overall cardiovascular risk”.
CPET is a highly useful clinical tool that evaluates organ-specific maladaptive physiological responses which may limit physical performance.
What are the most important parameters derived by the CPET?
VO2max (in mL/min or L/min) : maximum oxygen uptake
The product of the highest CO and arterial and venous O2 content difference (A – V) O2,
VO2max = COmax × (A – V) O2max
VO2peak (in mL/min or L/min) : peak oxygen uptake
The highest value obtained at the end of an exercise test to exhaustion
RER: respiratory exchange ratio
The ratio of CO2 production and O2 consumption (VCO2/VO2)
VE : ventilation during exercise
The product of RR by the volume of air exhaled at every respiratory cycle (tidal volume, Vt)
Ventilatory equivalents for O2
(VE/VO2) and CO2 (VE/VCO2)
The ratio of pulmonary ventilation and O2 consumption (VE/VO2) or the ratio of pulmonary
ventilation and CO2 production (VE/VCO2)
VE-VCO2 slope
The relationship between VE (plotted in the y-axis), and VCO2 (plotted in the x-axis)
PETCO2 (in mmHg) The carbon dioxide partial pressure at the end of expiration
AT or VT It is defined as the point at which minute ventilation increases disproportionately relative to
VO2
Oxygen pulse (VO2/HR) (in mL of O2/min/bpm)
It is the ratio between VO2 and the heart rate
ΔVO2/ΔWR relationship (VO2 in mL/min and workload in watts)
It is the relationship between VO2 and workload. It is measured during exercise on a cycle ergometer with a ramp protocol
Respiratory reserve (VE/MVV) : ventilation during exercise l maximum voluntary ventilation
(both VE, MVV in L/min)
It is the ratio between maximum VE and MVV assessed at rest
IC (L or mL) : inspiratory capacity
What is the level of evidence provided by this article?
ü CKD and proteinuria are associated with long term morbidity and mortality, mainly due to cardiovascular diseases.
ü CKD related anemia and CKD-BMD in addition to older age, associated hypertension and diabetes all can increase this burden.
ü Exercise tolerance can be a prognostic factor indicating physiological adaptation and its marked affection in advanced CKD indicated cardiovascular insufficiency, aortic calcification and endothelial dysfunction.
ü CPET is dynamic test, and none invasive to find the body response and reserve in cardiovascular, respiratory, muscular and psychological systems.
ü CPET aims at diagnosis of any exercise intolerance, its cause, diagnosis of any disability and appropriate rehabilitation program and its efficacy, prognostic evaluation of cardiac disorders.
Most important parameters:
ü VO2 max, maximum oxygen uptake;
ü VO2peak, peak oxygen uptake;
ü RER, respiratory exchange ratio;
ü IC, inspiratory capacity;
ü AT, anaerobic threshold;
ü VT, ventilatory threshold;
ü PETCO2, end-tidal CO2 partial pressure;
ü VE, pulmonary ventilation;
ü VE, ventilation during exercise;
ü MVV, maximum voluntary ventilation
Level of evidence is ; 5
CPET is very helpful in assessment of CV system , pulmonary system , muscular and neuropsychological response during exercise which allows assessment of the physiological reserve of these system which not adequately assessed during rest .
Also it is considered non invasive dynamic test that allows peak and submaximal exercise response giving a relevant information for clinical decision-making.
What are the most important parameters derived by the CPET?
1- Oxygen consumption (VO2): volume of Oxygen extracts from air during ventilation in a period of time and expressed in mL.min-1 or L.min-1
2-Pulmonary ventilation (VE): is the volume of air expired and inspired .
3-Ventilatory equivalents for oxygen (VE/VO2) and for carbon dioxide (VE/VCO2)
4-End-tidal CO2 partial pressure (PETCO2).
5-Oxygen pulse (O2 pulse)
6-Breathing reserve (VE/MVV)
What is the level of evidence provided by this article?
The gold standard for identifying exercise limitation is cardiopulmonary exercise testing (CPET). CPET provides an integrative evaluation of cardiovascular,pulmonary,hematopoietic,neuropsychological, and metabolic function during maximal or submaximal exercise.
A number of recent studies have used CPET in patients with pre-dialysis CKD, aiming to assess the cardiovascular reserve of these individuals, as well as the effect of interventions such as exercise training programs on their functional capacity.
Cardiorespiratory fitness reflects the ability of the cardiovascular and respiratory systems to transport oxygen to the working muscles of the human body during physical activity. Impaired cardiorespiratory fitness is strongly associated with early all-cause and cardiovascular-related mortality
A number of observational studies and randomized trials have applied CPET technology to evaluate cardio- pulmonary reserve in patients with pre-dialysis CKD and CPET in Patients with Pre-Dialysis CKD end-stage kidney disease.
This noninvasive, dynamic test permits the evaluation of both submaximal and peak exercise responses, providing the physician with relevant information for clinical decision-making. CPET is being used increasingly in a wide spectrum of clinical applications for evaluation of undiagnosed exercise intolerance and for objective determination of functional capacity and impairment
CKD has a prevalence of 9–12% in Western societies and is per se associated with increased risk for cardiovascular events and all-cause mortality. Among patients with CKD, cardiovascular disease is the leading cause of death. Existing studies suggest that exercise intolerance is an in- herent disturbance of CKD patients resulting in inactiv- ity, deconditioning, diminished functional capacity, feel- ing of tiredness, social isolation, and impaired quality of life.
Oxygen consumption (VO2): is the volume of O2 extracted from the air inhaled during pulmonary ventilation in a period of time. It is usually expressed in mL.min-1 or L.min-1 (STPD).
Anaerobic Threshold
The anaerobic threshold (AT) (Fig. 1), also known as the lactate threshold, lactic acid threshold, or gas exchange threshold, is considered an estimator of the onset of met- abolic acidosis caused predominantly by the increased rate of arterial lactate concentration during exercise
Respiratory Exchange Ratio
It expresses the ratio between CO2 output and O2 up- take (VCO2/VO2). It is currently the best noninvasive in- dicator of maximal exercise intensity. Values above 1.0 can reflect intense exercise, but those ≥1.10 are those searched on CPET, and have been accepted as a param- eter of maximal effort/exhaustion
Respiratory Exchange Ratio (RER) = VCO2/VO2, it tells the maximal exercise intensity. A RER above 1.1 denotes a state of maximal exhaustion.
Level of evidence is v
· “CPET can delineate multisystem changes and offer comprehensive phenotyping of factors determining overall cardiovascular risk”. Please read this article and explain how the authors reaches this conclusion.
· CPET is a non-invasive multisystem stress evaluation that informs of functional reserve of the patient’s cardiopulmonary system, hematopoietic and metabolic system, as well as neurophysiological system during a stress or resting state. It’s of great clinical utility, especially in differentiation the causes of exercise intolerance, treatment response monitoring, risk stratification and prognostication.
· What are the most important parameters derived by the CPET?
1. VO2 and Peak Oxygen Uptake: expressed in ml/min, represents the volume of oxygen during inhalation per minute ventilation
2. Anaerobic Threshold (AT): also known as lactate threshold or gas exchange threshold, an estimator of the onset of lactic acidosis under stress or exercise condition, which is a form of metabolic acidosis with anaerobic energy utilization. The normal AT values are about 40-65% of peak VO2.
3. Respiratory Exchange Ratio (RER) = VCO2/VO2, it tells the maximal exercise intensity. A RER above 1.1 denotes a state of maximal exhaustion.
· What is the level of evidence provided by this article?
Level V
CPET provides an integrative assessment of the cardiovascular, pulmonary, muscular, and neuropsychological responses during exercise; this allows the assessment of the physiological reserves of these systems that are not adequately reflected through the measurement of individual organ systems at rest.
This non-invasive dynamic test permits the evaluation of both submaximal and peak exercise responses, providing the physician with relevant information for clinical decision-making.
During CPET, a vast number of routine exercise testing variables and more sophisticated cardiorespiratory parameters are continuously (breath-by-breath) measured or estimated; this volume of physiological data obtained is necessary in order to assess each organ system’s response in coupling external respiration to cellular respiration during exercise.
Cardiopulmonary exercise testing (CPET) provides an integrated evaluation of the cardiorespiratory, muscular and neuropsychological system during exercise. CPET is designed to allow the assessment of the physiological factors that limit maximal exercise capacity. These factors may be related to the cardiovascular system, ventilatory and gas exchange response, or metabolic issues. CPET allows the measurement and identification of the patterns of the body’s responses to exercise. Since most dyspnea is associated with exertion, CPET provides the opportunity to simulate real-world conditions to cause dyspnea on exertion under controlled and monitored circumstances. The development of dyspnea can then be related to the normal or abnormal functioning of each of the body systems that contribute to maximal exercise capacity. CPET is a noninvasive, dynamic test and allow the evaluation of both submaximal and peak exercise responses, providing the physician with relevant information for clinical decision-making. CPET is used for evaluating the causes of exercise intolerance, particularly in patients with cardiovascular or respiratory disorders. It is based on the principle that system failure typically occurs while the system (e.g., muscle-energetic, cardiovascular, or pulmonary)is under stress.
CPET allows defining mechanisms related to low functional capacity that can cause symptoms, such as dyspnea, and correlate them with changes in the cardiovascular, pulmonary and skeletal muscle systems. Furthermore, it can be used to provide the prognostic assessment of patients with heart or lung diseases, and in the preoperative period
Oxygen consumption (VO2): is the volume of O2 extracted from the air inhaled during pulmonary ventilation in a period of time. It is usually expressed in mL.min-1 or L.min-1 (STPD). In practice, maximum VO2 (VO2 max) is defined as the highest value reached, despite progressive increase of the load applied, with the development of a plateau in the VO2 curve during an incremental exercise test. When no plateau can be identified, the highest value obtained at the end of an exhausting exercise is characterized as peak VO2, which, in practice, is used as VO2 max.
Pulmonary ventilation (VE): expressed as liters per minute, is the volume of air moved in and out of the lungs. It is determined as the product of respiratory rate by the volume of air exhaled at every cycle (tidal volume).
Respiratory coefficient or respiratory exchange ratio (R): expresses the ratio between CO2 production and O2 consumption (VCO2/VO2). It is currently the best non-invasive indicator of maximal or quasi-maximal exercise intensity. Values above 1.0 can reflect intense exercise, but those ≥ 1.10 are those searched on CPET, and have been accepted as a parameter of exhaustion or quasi-exhaustion.
Ventilatory equivalents for oxygen (VE/VO2) and for carbon dioxide (VE/VCO2): are the ratios between pulmonary ventilation and O2 consumption (VE/VO2) or CO2 production (VE/VCO2). Both decline from rest to submaximal exercise intensities, with VE/VO2 reaching minimum values before AT, when its progressive increase occurs, caused by the increase in ventilation to eliminate extra CO2 production. That results in lactate buffering by blood bicarbonate. Later, VE/VCO2 increases (respiratory compensation point – RCP, or second ventilatory threshold – VT2), resulting from ventilatory increase (compensatory respiratory alkalosis) in response to blood pH reduction due to the progressive accumulation of lactic acid at muscle level
End-tidal CO2 partial pressure (PETCO2): reflects ventilation-perfusion within the pulmonary system, and, indirectly, cardiac function. Its value ranges from 36 to 42 mmHg, with 3- to 8-mmHg elevations during moderate intensity exercise, reaching a maximal value with subsequent drop, due to VE increase, characterizing RCP. Abnormal values can represent disease severity in patients with HF, HCM, pulmonary hypertension, COPD and restrictive pulmonary disease.
Oxygen pulse (O2 pulse): is the ratio between VO2 (mLO2/min) and heart rate (HR – bpm). Its meaning is better understood by observing the Fick equation: VO2 = HR x systolic volume (SV) x arteriovenous oxygen difference [(A-V)O2 diff].
Breathing reserve (VE/MVV): represents the ratio between maximal ventilation during exercise (VE) and maximum voluntary ventilation (MVV) at rest, both variables in L/min. Equations to predict MVV can be used (forced expiratory volume in the first second – FEV1 x 40), although it can be measured directly on pre-test spirometry. Normal values are greater than 0.20
ΔVO2/ΔWR Relationship: relationship between VO2 (Y axis in mL.min-1) and workload (X axis in Watts), measured only during exercise on a cycle ergometer with ramp protocol, whose value is progressively and linearly incremented until maximal effort. It is useful in the diagnosis of patients suspected of having myocardial ischemia with left ventricular dysfunction on exertion. Its normal value for adults is 9 mL.min-1.W-1 (the lowest limit being 8.6 mL.min-1.W-1).
VE-VCO2 slope The relationship between VE (plotted in the y-axis), and VCO2 (plotted in the x-axis)
AT or VT It is defined as the point at which minute ventilation increases disproportionately relative to VO2
Level 5
Chronic kidney disease (CKD) is often characterized by increased prevalence of cardiovascular risk factors and increased incidence of cardiovascular events and death
CPET is the gold standard for identifying exercise limitation is cardiopulmonary exercise testing . . CPET provides an integrative evaluation of cardiovascular, pulmonary, hematopoietic, neuropsychological, and metabolic function during maximal or submaximal exercise. It is useful in clinical setting for differentiation of the causes
of exercise intolerance, risk stratification, and assessment of response to relevant treatments .
VO2:
The volume of oxygen taken from the inhaled air during ventilation in a period of time.
VO2 max:
The highest VO2 attainable for a given exercise evidenced by failure of VO2 to increase more, despite progressive increase in work rate.
Peak VO2:
The highest value reached at the end of an exhausting exercise test, used in both healthy and diseased populations, test the functional exercise and determine the severity of the disease
Anaerobic threshold (lactate threshold, gas exchange threshold):
Estimate the onset of metabolic acidosis due to increased lactate concentration during exercise and is expressed as percentage of predicted value of VO2 peak, it helps to differentiate cardiac and non-cardiac causes of exercise limitations, fatigue before reaching anaerobic threshold is mostly due to non-cardiac causes.
Respiratory exchange ratio:
The ratio between CO2 output and oxygen uptake indicating maximal exercise intensity.
Level five
Based on the article which was very informative. CPET is the gold standard to help identify the limitation of exercise in patients who have high cardiovascular risk. It is indeed very important to evaluate patients who need kidney transplants. It is integrative, comprehensive and a procedure that is non-invasive. Due to its effectiveness, it can be used to evaluate cardiovascular pathologies or if there are any limiting pathologies, pulmonary functions and their limitations, the hematopoietic system, neurophysiological changes, and metabolic functions. It can be used in the clinical setting to differentiate causes like how the patient tolerates the exercise, any risk stratification, and saw how best patients respond to treatment. It helps to evaluate both submaximal and peak exercise responses allowing physicians to make proper clinical decisions. During CPET, many routine exercise testing variables and cardiorespiratory parameters are continuous measures or estimated. In so doing, it provides information on each organ.
The most important parameters derived by the CPET are as follows:
1) VO2 peak: it is the highest volume of oxygen extracted from the air inhaled at the end of an exercise to exhaustion. If it is less than 85% of the predicted value, it will be considered abnormal. If the VO2 peak is less than 17 ml/kg/min it is associated with possible cardiovascular events and all-cause mortality. It is the gold standard to measure cardiovascular fitness and the most important measurement during exercise testing.
So, in summary, VO2 max is the product of the highest CO and arterial and venous O2 content difference. While VO2 peak is the highest value that can be obtained at the end of an exercise test to exhaustion.
2) The anaerobic threshold. It is also known as the lactate threshold, the lactic acid threshold, or the gas exchange threshold. It estimates the onset of metabolic acidosis caused by the increase of the arterial lactate concentration during the process that is exercise.
3) The other is the respiratory exchange ratio. It is the ratio between the CO2 output and the O2 uptake. If a ratio of 1.1 is found, it reflects as the marker of maximal effort/exhaustion. Currently, it is the best non-invasive marker of maximal exercise intensity.
Based on what is mentioned it is a level 5 which is evidence from systematic reviews of descriptive and qualitative studies.
“CPET can delineate multisystem changes and offer comprehensive phenotyping of factors determining overall cardiovascular risk”. Please read this article and explain how the authors reaches this conclusion
CPET is an integrative, comprehensive, and non-invasive evaluation of multiple organ systems like Cardiac, Pulmonary, Neurophysiologic and Muscular system during exercise and evaluate multiple parameters which can guide cardio-pulmonary reserve/capacity in an individual especially during stress.
Evaluation of individual system at rest can’t predict their behavior during periods of surgical stress and thereby have variable prognostic significance during periods of surgical stress/exercise.
Oxygen Transport chain depicts three gears (Respiration, circulation, and muscular function) which are inter-dependent and CPET is gold standard in evaluating these three gears/systems to reliably predict performance of an individual under surgical stress/exercise
CPET can assess
1. Factors causing exercise intolerance/Disability
2. Differential diagnosis of conditions associated with decreased cardio-pulmonary reserves
3. Preoperative fitness for surgery
4. Cardiac/Pulmonary disorders functional and prognostic significance
5. Formulating schedule for exercise training and prehabilitation
6. Long term risk stratification in patient with cardiac and pulmonary disorders
7. Efficacy of treatment imparted
CPET has been widely used for preoperative evaluation in cardiac, pulmonary disorders and organ transplantation (Like liver, Heart and Lung) but is underutilized in patients with CKD due to various factors of exercise limitation already prevalent in this condition (CKD) like inactivity, deconditioning, feeling of tiredness, diminished functional capacity and anemia.
What are the most important parameters derived by the CPET?
a) Vo2 Max/Vo2 Peak: Vo2 is defined as volume of oxygen extracted during respiration in a given period.
Vo2 max is highest value attainable with failure of further increase with increase in exercise/stress.
Vo2 peak can be alternatively used as Vo2 achieved during exhaustion.
Vo2 peak is considered abnormal when it is below 85% of its predicted value.
It is a considered as gold standard measure during CPET for assessing exercise testing and finding physical fitness level.
It can also mark diseases severity in various respiratory and cardiac disorders like COPD, Pulmonary Hypertension, Heart failure, Cardiomyopathy.
b)Anaerobic /Lactate/Lactic acid/Gas exchange Threshold(AT) : represents upper limit of aerobic metabolism while increasing workloads during exercise.
It also represents Vo2 peak where lactate levels in the blood start increasing, thereby an estimator of onset of metabolic Acidosis.
It can also differentiate between cardiac and non-cardiac factors of exercise limitation as exhaustion/fatigue before reaching AT points towards non cardiac cause.
AT Normal mean values ranges between 45 to 60% of peak V02
c)Respiratory Exchange ratio: It is considered as best noninvasive measure of exercise tolerance and defined as ratio of Co2 output and O2 uptake (Vco2/Vo2).
Value of 1 point towards intense exercise and greater than equal to 1.1 represent maximal effort/exhaustion
d)Exercise Intolerance: Defined as abnormal low Vo2 Peak of any cause.
As per Fick’s Equation, Vo2 equals cardiac output times difference of Arterial-mixed venous oxygen content.
Any abnormality in heart rate/stroke’s volume like heart failure or disease of lung, skeletal muscle function, anemia which affects arterial-mixed venous oxygen content results in decrease exercise capacity.
Exercise intolerance is prevalent in CKD patient due to various factors like anemia, cardiac and pulmonary dysfunction, sarcopenia and has been associated with decreased QoL, frequent hospitalization and social life limitations.
What is the level of evidence provided by this article?
As the article is a mix of observation studies and Randomized trial so level of evidence is 5
The gold standard for identifying exercise limitation is cardiopulmonary exercise testing (CPET). CPET provides an integrative evaluation of cardiovascular, pulmonary, hematopoietic, neuropsychological, and metabolic function during maximal or submaximal exercise. It is useful in clinical setting for differentiation of the causes of exercise intolerance, risk stratification, and assessment of response to relevant treatments.
Potential clinical applications of CPET in CKD patients range from objective diagnosis of exercise intolerance to preoperative and long-term risk stratification and providing intermediate endpoints for clinical trials. Future studies should delineate the association of CPET index- es, with cardiovascular and respiratory alterations and hard outcomes in CKD patients, to enhance its diagnostic and prognostic utility in this population.
This noninvasive, dynamic test permits the evaluation of both submaximal and peak exercise responses, providing the physician with relevant information for clinical decision-making .
CPET is a highly useful clinical tool that evaluates organ specific maladaptive physiological responses which may limit physical performance. It provides breath-by- breath gas exchange measures while progressively increasing exercise intensity in a linear function over time to maximally stress the oxygen delivery and utilization system .
CPET may have a wide range of clinical applications that can help to better characterize the cardiopulmonary phenotype of patients with CKD.
CPET information can be used to inform the decision-making and consent processes, to direct preoperative interventions, intraoperative anes- thetic practice, prehabilitation, and rehabilitation, as well as to estimate the likelihood of perioperative morbidity and mortality.
——————————————
VO2 and Peak Oxygen Uptake
VΟ2peak has become the “gold standard” laboratory measure of cardiorespiratory fitness and the most important measurement during the functional exercise testing. It has been used as a universal marker, which can reflect disease severity in patients with heart failure, pulmonary hypertension, hypertrophic car- diomyopathy, chronic obstructive pulmonary disease, and restrictive pulmonary disease, in addition to physical fitness level .
Anaerobic Threshold
The ability to achieve the AT can assist in differentiating cardiac and noncardiac causes of exercise limitation; fatigue before reaching AT is likely related to noncardiac causes
Respiratory Exchange Ratio
————————————————————
Level V
Evidence from systematic reviews of descriptive and qualitative studies (meta-synthesis)
Well done
What about the respiratory exchange ratio VCO2/VO2 ?
CPET provides an integrative assessment of the cardiovascular, pulmonary, muscular, and neuropsychological responses during exercise; this allows the assessment of the physiological reserves of these systems that are not adequately reflected through the measurement of individual organ systems at rest.
This non-invasive dynamic test permits the evaluation of both submaximal and peak exercise responses, providing the physician with relevant information for clinical decision-making.
During CPET, a vast number of routine exercise testing variables and more sophisticated cardiorespiratory parameters are continuously (breath-by-breath) measured or estimated; this volume of physiological data obtained is necessary in order to assess each organ system’s response in coupling external respiration to cellular respiration during exercise.
Level 5
Thank You, well done
CPET integrates cardiovascular, pulmonary, neuromuscular and neurophysiological responses during exercise, helping to assess the physiological reserve of the patient and take a decision regarding overall morbidity and mortality risks.
This is a non-invasive test, which assesses routine exercise testing parameters and more advanced cardiorespiratory parameters continuously (breath-by-breath) by capturing and analysing the expired gas helping in predicting outcomes in such patients and taking an informed decision regarding pre-operative interventions, intra-operative actions and rehabilitation.
Observational CPET studies in CKD patients showed that VO2peak and VO2 at the AT were lower. Studies have shown that VO2peak increased with cardiac rehabilitation. CPET tests have been shown to be reproducible over time, lending credence to their use. RCTs have shown that following exercise intervention, there is significant improvement in the physical performance of the patients.
Based on the evidence regarding use of CPET in pre-operative evaluation of different patients, the authors reached the conclusion. CPET in CKD may help in assessing exercise intolerance, getting its differential diagnosis and stratifying long-term risk.
The most important parameters derived by CPET include:
1) VO2peak: Highest volume of oxygen extracted from the air inhaled at the end of an exercise to exhaustion (it is different from VO2max, which is the highest volume attainable for a given form of exercise). VO2peak, if less than 85% of the predicted value, is considered abnormal. VO2peak less than 17ml/kg/min is associated with future cardiac event and all-cause mortality. It is the gold standard of laboratory measure of cardiorespiratory fitness.
2) Anaerobic threshold (AT)/ Lactate threshold/ lactic acid threshold/ gas exchange threshold: It is the level of exercise VO2 above which anaerobic mechanisms for energy productions are utilized, which can be detected by sudden increase in lactate levels. The normal AT values are 40-65% of peak VO2. AT less than 11 ml/min/Kg is a risk for major surgery. Fatigue before reaching AT is likely due to non-cardiac causes.
3) Respiratory exchange ratio (RER): It is the ratio between CO2 output and O2 uptake (VCO2/VO2). Ratio above 1.1 is a marker of maximal effort/ exhaustion. It is the best non-invasive marker of maximal exercise intensity.
The level of evidence is level 5 (a narrative review)
In the assessment , evaluation and preparation of CKD S 5 +/- dialysis for conducting transplantation, we should be sure that the patient has no failure of the most vital organ (cardiopulmonary system ) .
As we know that disaeas of the heart affect the kidneys , and vise versa , the CKD patient have 25% more risk factor of developing cardiovascular events and death .
So assessment of cardiopulmonary systems is vital to obtain a successful transplantation and graft function and by the end of the day , to improve quality of life of the recipient .
@ How the studies reach the conclusions:
All randomize trials using CPET in patient with pre-dialysis CKD ,(studies of program of sxcercise training ).
Results of metanalysis show pooled estimates of improved VO2 peak/VO@ max with physical rehabilitation program
CPET is the most valuable test of assessing exercise capacity and limitation of the recipient , as cardiopulmnary and associated condition (DM , vascular affection ..etc) assessment involved in any evaluation take high percentage of parameters of scores and indexes , eg (40% of charlson comorbidity index) .
@ The most important parameters derived from CPET are:
define as the ratio of CO2 production and O2 consumption ( VCO2/VO2).
4.VE :
define as the product of RR by the volume of air exhaled at every respiratory cycle (tidal volume, Vt)
5.Ventilatory equivalent for O2 (VE/VO2):
define as the ratio of pulmonary ventilation and O2 consumption (VE/VO2) or the ratio of pulmonary ventilation and CO2 production (VE /VCO2).
6.VE-VCO2 slope :
define as the relationship between VE (plotted in the y-axis ) , and VCO2 (plotted in the x-axis ).
7.PETCO2 (in mmgh);
define as the carbon dioxide partial pressure at the end of expiration .
8.AT or VT :
define as the point at which minute ventilation increases disproportionately relative to VO2.
9.Oxygen pulse (VO2/HR ) (in mL of O2/min/bpm):
define as the ratio between VO2 and the heart rate .
10.ΔVO2/ΔWR relationship (VO2 in mL /min and workload in watts):
define as the relationship between VO2 and workload . It is measured during exercise on a cycle ergometer with a ramp protocol .
11.Respiratory reserve (VE/MVV) (both VE, MVV, in L/min):
define as the ratio between maximum VE and MVV assessed at rest .
12.IC (Lor mL):
define as the maximum amount of air that can be expired after a normal exhalation .
( CO : cardiac output
CPET: cardiopulmonary exercise testing
VO2 max : maximum O2 uptake
VO2 peak : peak O2 uptake
RER: respiratory exchange value
IC inspiratory capacity
AT : anaerobic threshold
VT: ventilatory threshold
PETCO2: end-tidal CO2 partial pressure
VE : pulmonary ventilation
VE : ventilation during exercise
MVV : maximum voluntary ventilation
RR : respiratory rate .
@ level of evidence (( 5 )).
Thank You, well done
The authers consider Cardiopulmonary exercise testing (CPET) is The gold standard for identifying overall cardiovascular risk
** First it is a noninvasive technique
** provides an integrative evaluation of cardiovascular, pulmonary, hematopoietic, neuropsychological, and metabolic function during maximal or submaximal exercise.
** Assessment CKD patients and predialysis patients for CAD before transplantation
** cost-effective
** assess cardiorespiratory fitness.
** valuable in identifying the source of exercise intolerance
** Assessment exercise capacity
** Preoperative assessment for cardiovascular and polmunary state
** Monitoring disease progression
** evaluating treatment responsiveness and providing information about prognosis.
The most important parameters derived from CPET is
# VO2 and Peak Oxygen Uptake which is the gold standard laboratory measure of cardiorespiratory fitness
# PETCO2 The carbon dioxide partial pressure at the end of expiration
# Anaerobic Threshold
# Respiratory Exchange Ratiothe ratio between CO2 output and O2 uptake
(VCO2/VO2)
The level of article is 5
Thank You, But this is a very short summary. CPET is coming up fast and a comprehensive investigation which we should know about it.
The provided article has evidence level 5.
CPET provides an integrative assessment that evaluates patient’s cardiovascular, pulmonary, muscular, and neuropsychological response to physical stress. CPET allows the assessment of the physiological reserves of these systems that are not accurately reflected through the measurement of individual organ system at rest.
What are the most important parameters derived by the CPET?
Commonly Used CPET Indexes:
1-VO2 and Peak Oxygen Uptake: VO2 is the volume of O2 extracted from the air inhaled during pulmonary ventilation in a period of time. VO2 peak is considered abnormal when below 85% of the predicted value. VO2 become the “gold standard” laboratory measure of cardio-respiratory fitness and the most important measurement during the functional exercise testing.
2- Anaerobic Threshold: Lactate threshold, lactic acid threshold, or gas exchange threshold, is considered an estimator of the onset of metabolic acidosis caused predominantly by the increased rate of arterial lactate concentration during exercise. AT is referenced to the VO2 at which this change occurs and is expressed as a percentage of the predicted value of VO2peak. AT can assist in differentiating cardiac and noncardiac causes of exercise limitation; fatigue before reaching AT is like related to no cardiac causes.
3-Respiratory Exchange Ratio:
The ratio between CO2 output and O2 uptake (VCO2/VO2). It is currently the best indicator of maximal exercise intensity. Values above 1.0 can reflect intense exercise, but those ≥1.10 are those searched on CPET, and have been accepted as a parameter of maximal effort/exhaustion.
Thank You, well done
.
CPET is a dynamic, noninvasive technique that is useful in various clinical settings for
• diagnosis,
• risk stratification,
• and the evaluation of response to cardiopulmonary therapies
the gold standard for evaluating the degree and differentiating the causes, by unmasking physiological mechanisms of exercise intoleranc
Indication of CPET include:
(a) evaluation of exercise capacity,
(b) evaluation and differential diagnosis of exercise intolerance,
(c) evaluation of disability,
(d) designing the rehabilitation program and assessing its efficacy,
(e) preoperative evaluation,
applied CPET technology to evaluate cardiopulmonary reserve in patients with pre-dialysis CKD and end-stage kidney disease
(f) functional and prognostic evaluation of patients with heart diseases,
(g) functional and prognostic evaluation of patients with respiratory disorders, and
(h) assessing treatment efficacy
The author highlighted CPET Studies in patients with Pre-Dialysis CKD. VO2max was lower in CKD patients than in controls but higher when compared to heart failure patients
The randomized trials using CPET in Non-Dialysis CKD Patients shown beneficial effects of various exercise programs on VO2peak and other CPET parameters
But long-term and optimally designed studies should first evaluate the association of key CPET parameters, such as VO2peak, with key outcomes such as cardiovascular and all-cause mortality specifically in patients with CKD.
most important variables obtained during CPET
1. VO2 and Peak Oxygen Uptake
VO2peak is the highest value reached at the end of an exhausting exercise test,VΟ2peak has become the “gold standard” laboratory measure
2. Anaerobic Threshold
AT is referenced to the VO2 at which lactate threshold change occurs and is expressed as a percentage of the predicted value of VO2peak (%VO2peak predicted).
3. Respiratory Exchange Ratio
It expresses the ratio between CO2 output and O2 uptake (VCO2/VO2). It is currently the best noninvasive indicator of maximal exercise intensity
The level of evidence provided by this article is 5
Thank you Ghalia
The authors reach this conclusion since CPET provides an integrative assessment of multiple systems involved in the process of exercise like cardiovascular, pulmonary, muscular, and neuropsychological systems. By this CPET allows the assessment of the physiological reserves of these systems that are not adequately reflected through the measurement of individual organ system at rest. Furthermore their idea is based on the principle that system failure typically occurs while the system (cardiac, muscular, or pulmonary)is under stress. Finding out the dynamic changes of these systems objectively and noninvasively is very useful in determining the overall cardiac risk.
1-VO2max (in mL/min or L/min) The product of the highest CO and arterial and venous O2 content difference (A − V) O2, VO2max = COmax × (A − V) O2max
2-VO2peak (in mL/min or L/min): The highest value obtained at the end of an exercise test to exhaustion
3-RER: The ratio of CO2 production and O2 consumption (VCO2/VO2)
4-VE: The product of RR by the volume of air exhaled at every respiratory cycle (tidal volume, Vt).
5-Ventilatory equivalents for O2 (VE/VO2) and CO2 (VE/VCO2): The ratio of pulmonary ventilation and O2 consumption (VE/VO2) or the ratio of pulmonary ventilation and CO2 production (VE/VCO2).
6-VE-VCO2 slope:The relationship between VE (plotted in the y-axis), and VCO2 (plotted in the x-axis).
7-PETCO2 (in mmHg) The carbon dioxide partial pressure at the end of expiration.
8-AT or VT It is defined as the point at which minute ventilation increases disproportionately relative to VO2.
9-Oxygen pulse (VO2/HR) (in mL of O2/min/bpm):It is the ratio between VO2 and the heart rate.
10-ΔVO2/ΔWR relationship (VO2 in mL/min and workload in watts): It is the relationship between VO2 and workload. It is measured during exercise on a cycle ergometer with a ramp protocol.
11-Respiratory reserve (VE/MVV) (both VE, MVV in L/min): It is the ratio between maximum VE and MVV assessed at rest.
12-IC (L or mL): It is the maximum amount of air that can be expired after a normal exhalation
This is low level, level 5
Thank you
CPET is considered the “gold standard” in the assessment of exercise capacity, it depends on principle that system failure occurs when system is under stress so it evaluates submaximal and peak exercise response.
It provides breath by breath gas exchange measure at the time of increasing exercise intensity to maximally stimulate oxygen delivery and utilization.
It can identify hidden causes of poor exercise capacity as respiratory function disturbances and neuromuscular disorders.
It differentiates the causes of decreased exercise capacity in CKD patients with multiple comorbidities and allow treatment optimization to improve the functional capacity.
It can identify patients who will benefit from intervention to improve physical function and determine the optimal training intensity level and exercise safety
It can follow up the effect of intervention and response to treatment.
It can estimate perioperative morbidity and mortality.
In patients with COPD, it is used to predict the risk of all-cause mortality independent of lung function indices, also in patients with heart failure, CPET predicts the risk of hospitalization and mortality independent of ejection fraction and clinical condition.
VO2:
The volume of oxygen taken from the inhaled air during ventilation in a period of time.
VO2 max:
The highest VO2 attainable for a given exercise evidenced by failure of VO2 to increase more, despite progressive increase in work rate.
Peak VO2:
The highest value reached at the end of an exhausting exercise test, used in both healthy and diseased populations, test the functional exercise and determine the severity of the disease
Anaerobic threshold (lactate threshold, gas exchange threshold):
Estimate the onset of metabolic acidosis due to increased lactate concentration during exercise and is expressed as percentage of predicted value of VO2 peak, it helps to differentiate cardiac and non-cardiac causes of exercise limitations, fatigue before reaching anaerobic threshold is mostly due to non-cardiac causes.
Respiratory exchange ratio:
The ratio between CO2 output and oxygen uptake indicating maximal exercise intensity.
Level 5 (review article)
Thank you
“CPET can delineate multisystem changes and offer comprehensive phenotyping of factors determining overall cardiovascular risk”. Please read this article and explain how the authors reaches this conclusion
CPET provides an integrative assessment of the cardiovascular, pulmonary, muscular, and neuropsychological responses during exercise; this allows the assessment of the physiological reserves of these systems that are not adequately reflected through the measurement of individual organ system at rest .
It considered the gold standard for evaluating the causes of exercise intolerance, especially in patients with cardiovascular or respiratory disorders, and is based on the principle that system failure typically occurs while the system (e.g., muscle-energetic, cardiovascular, or pulmonary) is under stress .
It is noninvasive, dynamic test permits the evaluation of both submaximal and peak exercise responses . It is being used increasingly in a wide spectrum of clinical applications for evaluation of undiagnosed exercise intolerance
and for objective determination of functional capacity and impairment .
What are the most important parameters derived by the CPET?
VO2 and Peak Oxygen Uptake
VO2 is the volume of O2 extracted from the air inhaled during pulmonary ventilation in a period of time in mL/min or L/min. VO2peak is considered abnormal when below 85% of the predicted value . VΟ2 is the “gold standard” laboratory measure of cardiorespiratory fitness and the most important measurement during the functional exercise testing.
It can reflect disease severity in patients with heart failure, pulmonary hypertension, hypertrophic cardiomyopathy, chronic obstructive pulmonary disease, and restrictive pulmonary disease, in addition to physical fitness level .
Anaerobic Threshold
The anaerobic threshold (AT) , also known as the lactate threshold, lactic acid threshold, or gas exchange threshold, is considered an estimator of the onset of metabolic acidosis caused predominantly by the increased rate of arterial lactate concentration during exercise. AT is referenced to the VO2 at which this change occurs and is expressed as a percentage of the predicted value of VO2peak (%VO2peak predicted).
The normal mean AT values expected for adults are around 40–65% of peak VO2 .The ability to achieve the AT can assist in differentiating cardiac and noncardiac causes of exercise limitation; fatigue before reaching AT is likely related to noncardiac causes .
Respiratory Exchange Ratio
It expresses the ratio between CO2 output and O2 uptake (VCO2/VO2). It is currently the best noninvasive indicator of maximal exercise intensity. Values above 1.0 can reflect intense exercise, but those ≥1.10 are those
searched on CPET, and have been accepted as a parameter of maximal effort/exhaustion .
What is the level of evidence provided by this article?
5
Thank you
Ckd patients have alot of comorbidity and cardiovascular complication .
Exercise intolerance is affected in ckd patient and decresed of excersie tolerance is prognostic fator of morbidity and mortality
It is of beneficial to measure the exercise capacity in ckd patient
Cpet is an evaluation test of the
cardiopulmonary system used usually to assess the performance of heart and lungs at rest and during exercise.
It depends on the mesearment of multiple parameters to assess the balance between demands and output.
The use of cpet is inreasing with benefits in multiple clinical application
The most important indication are,:
1- evaluation of exercise capacity
2_causes of exercise intolerance
3_preoperative evaluation (ckd and transplant patient)
4_prognostic indicator of mortality in cvd and copd patients.
5_monitoring of treatment efficacy.
Cpet uses multiple parameter to know the balance between demand and output as mension above ,the most important parameters are :
1-vo2max and peak oxygen uptake :
Ammount of oxgen extract ed for air inhaled in a pulmonary ventilation in period of time
It measures by ml/min or per liter
2_ anerobic threshold:depends on the how lactic acid concentration increase with exercise,by this measurement we could determine the upper limit of workload.
3_respiratory exchang ratio :
Measures the ratio between co2 output and o2 uptake,so we could know the maximal exercise intensity.
4_ fick equation : to measure the functional aerobic capacity of the individual.
Which is the maximal ability of a person to take in-transport and use of oxygen.
level of evidence : (5)
Thank you
CPET provides an integrative assessment of the cardiovascular, pulmonary, muscular, and neuropsychological responses during exercise; this allows the assessment of the physiological reserves of these systems that are not adequately reflected through the measurement of individual organ system at rest.
VO2 – This is the volume of oxygen extracted from the air inhaled during ventilation within a specific time period. Historically, the VO2max was used which was the highest VO2 obtained by healthy individual for a given form of exercise and this was compared to the patient being assessed. Currently VO2peak, which is the highest value of VO2 reached at the end of an exhausting exercise test is used alternatively to the VO2max.
VO2max is considered abnormal when It is below 85% of the predicted value.
Level of evidence: 5
Thank you, this is a very short summary
Summary:
__________
Assessment of Exercise Intolerance in Patients with Pre- Dialysis CKD with Cardiopulmonary Function Testing
¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
Introduction
▪︎Patients with CKD are at increased risk for cardiovascular events and all-cause mortality. They also have lower cardiorespiratory fitness than the general population. Thus, exercise intolerance is inherently associated with CKD.
▪︎The ability of CKD patients to exercise can be related to a number of
factors, including cardiac function disturbances, endothelial dysfunction, arterial stiffness, morphological and functional abnormalities of skeletal muscles, dysautonomia of nervous system, anemia, depression, and others . these factors can lead to low quality of life.
▪︎Cardiopulmonary exercise testing (CPET) is a dynamic, noninvasive technique that is useful in various clinical settings for diagnosis, risk stratification, and the evaluation of response to cardiopulmonary therapies.
Cardiopulmonary Exercise Testing:
___________________________________
▪︎CPET provides an integrative assessment of the cardiovascular, pulmonary, muscular, and neuropsychological responses during exercise; this allows the assessment of the physiological reserves of these systems that are not adequately reflected through the measurement of individual organ system at rest.
Indications of CPET include:
(1) Evaluation of exercise capacity.
(2) Evaluation and differential diagnosis of exercise intolerance.
(3) Evaluation of disability.
(4) Designing the rehabilitation program and assessing its efficacy.
(5) Preoperative evaluation.
(6) Functional and prognostic evaluation of patients with heart diseases.
(7) Functional and prognostic evaluation of patients with respiratory disorders (8) Assessing treatment efficacy.
The most important parameters derived by the CPET:
1) VO2 and Peak Oxygen Uptake
▪︎VO2 is the volume of O2 extracted from the air inhaled during pulmonary ventilation in a period of time.
VO2max is defined as the highest VO2 attainable for a given form of exercise.
▪︎In practice peak VO2 (VO2peak), that is the highest value reached at the end of an exhausting exercise test, is used alternatively to VO2max, both in healthy individuals and diseased populations.
▪︎Mean values at intervals of 10– 60 s should be measured depending on the protocol.
▪︎VΟ2peak has become the “gold standard” laboratory measure of cardiorespiratory fitness and the most important measurement during the functional exercise testing and it is considered abnormal when below 85% of the predicted value.
2) Anaerobic Threshold (AT):
▪︎The anaerobic threshold, also known as the lactate threshold, lactic acid threshold, or gas exchange threshold, is considered an estimator of the onset of metabolic acidosis caused predominantly by the increased rate of arterial lactate concentration during exercise.
▪︎It is referenced to the VO2 at which this change occurs and is expressed as a percentage of the predicted value of VO2peak.
▪︎The normal mean AT values expected for adults are around 40–65% of peak VO2.
▪︎The ability to achieve the AT can assist in differentiating cardiac and noncardiac causes of exercise limitation; fatigue before reaching AT is likely related to noncardiac causes.
3) Respiratory Exchange Ratio
▪︎ It expresses the ratio between CO2 output and O2 uptake (VCO2/VO2).
▪︎Now it is the best noninvasive indicator of maximal exercise intensity.
▪︎ Values above 1.0 can reflect intense exercise, but those ≥1.10 are those searched on CPET, and have been accepted as a parameter of maximal effort/exhaustion.
Level of evidence: 5
Thank you Tahani for your reply, yes level 5
CPET provides an integrative assessment of thecardiovascular, pulmonary, muscular, and neuropsychological responses during exercise.
CPET helps in evaluation of both submaximal and peak exercise response
Important parameters:
V O2 and peak oxygen uptake
Anaerobic threshold
Respiratory exchange ratio
Level of evidence:
1
Thank you, Tufayelfor your reply. Please review the evidence based on the attached diagram. Also, please write more. This is a short summary.
As chronic kidney disease has increased risk for cardiovascular events and death, it was crucial to identify exercise limitation, and the gold standard for this is cardiopulmonary exercise testing (CPET). CPET evaluate cardiovascular, pulmonary, hematopoietic, neuropsychological, and metabolic function during maximal or submaximal exercise.
CPET can be used for differentiation of the causes of exercise intolerance, risk stratification, and assessment of response to appropriate treatments.
During CPET a lot of routine exercise testing and complex cardiorespiratory parameters are continuously measured or estimated.
Indications of CPET:
1) evaluation of exercise capacity
2) evaluation and differential diagnosis of exercise intolerance
3) evaluation of disability
4) designing the rehabilitation program and assessing its efficacy
5) preoperative evaluation
6) functional and prognostic evaluation of patients with heart diseases
7) functional and prognostic evaluation of patients with respiratory disorders
8) assessing treatment efficacy
The most important variables obtained during CPET:
1) VO2 and peak Oxygen Uptake. VO2 is the volume of O2 extracted from the air inhaled during pulmonary ventilation in a period of time (usually expressed in ml/min or L/min).
VO2 peak: is the highest value reached at the end of an exhausting exercise test, used in both healthy and diseased populations.
VO2 peak became the gold standard laboratory measure of cardiorespiratory fitness and the most important measurement during the functional exercise testing.
VO2 peak can reflect disease severity in patients with heart failure, COPD, and restrictive pulmonary disease, plus physical fitness level.
2) Anaerobic Threshold (AT): an estimator of the onset of metabolic acidosis caused by mainly by elevated lactate levels during exercise.
The AT is the level of exercise VO2, above which aerobic energy production is supplemented by anaerobic mechanism, which is reflected by an abrupt increase in the arterial lactic acid concentration.
The ability to achieve the AT may help to differentiate between cardiac and noncardiac causes of exercise limitation; fatigue before reaching AT is mostly related to noncardiac causes.
3) Respiratory Exchange Ratio: the ratio between CO2 output and O2 uptake(VCO2/VO2) .
It is the best non-invasive indicator of maximal exercise intensity .
Thank you for your reply, yes level 5
“CPET can delineate multisystem changes and offer comprehensive phenotyping of factors determining overall cardiovascular risk”. Please read this article and explain how the authors reaches this conclusion
The authors looked in-depth in CPET in multiple aspects,
Firstly: it covers what is CPET, when its indicated, what its various specific detailed variables and its different clinically used parameters.
Secondly observational CPET Studies in Patients with Pre-Dialysis CKD:
It aimed to quantify the cardiovascular reserve of CKD patients who were not
on renal replacement therapy by comparing CKD group to control group .
9 studies were analysed, each group target different parameters like VO2peak,
VO2 at the ventilatory threshold , VO2max, parameters in relation to vascular function measures.
Then Randomized Trials CPET in Non-Dialysis CKD Patients (different stages)
15 studies were reviewed with sample size from 11 to 142 participants: the commonest studied parameter was VO2peak which have shown beneficial effects, over an average of 12 months’ duration.
Putting in consideration it was uses in cardiopulmonary assessment for several years mainly in heart surgery and organ transplantation. CPET information can be used to risk stratification of the patients and to estimate the likelihood of perioperative morbidity and mortality.
Regarding CKD group:
Although the article covers apparently good number of studies BUT most of them of small sample size so significance might be questionable, and all patients were pre renal replacement therapy-dialysis so we still have no clue about the CPET in dialysis population.
What are the most important parameters derived by the CPET?
CPET provides an evaluation of cardiovascular, pulmonary, hematopoietic, neuropsychological, and metabolic function.
Cardiopulmonary parameters: VO2 and Peak Oxygen Uptake:
VO2 is the volume of O2 extracted from the air inhaled during pulmonary ventilation in a period of time. It is expressed in mL/min or L/min.
VO2peak: is the highest value reached at the end of an exhausting exercise test, is considered abnormal when below85% of the predicted value has become the gold standard cardiopulmonary parameters.
What is the level of evidence provided by this article?
Covering physiological based topic, It reviewed in details observational studies and Randomized Trials – Level 5
Thank you for your reply, yes level 5
Chronic kidney disease is common worldwide, with reduced cardiovascular reservoir and excise intolerance. Cardiovascular disease is associated with adverse outcome.
Cardiopulmonary exercise testing (CPET) is the gold standard for identifying exercise imitation. CPET can be used to evaluate cardiovascular, pulmonary, hematopoietic, neuropsychological, and metabolic function at maximal and submaximal exercise. It used in clinical practice for risk stratification, identification of the causes of exercise intolerance and assessment of treatment response. CKD is emerging to become the fifth cause of death globally by 2040, and cardiovascular complications are the main cause of death in these patients. Cardiopulmonary fitness reflects the ability of the cardiovascular and respiratory systems to transport oxygen to the working muscles during physical activity. This fitness decrease with declining CKD function, and is associated with aortic stiffness, poor left ventricular function, and higher cardiovascular events risk. Therefore, exercise intolerance, is a prognostic factor of morbidity and mortality in CKD patients. CPET is a dynamic, noninvasive test. During CPET, many number of routine exercise testing variables and more sophisticated cardiorespiratory parameters are continuously (breath by breath) measured or estimated, data obtained is used to assess organ system response to respiration during exercise.
Indications of CPET:
1- Evaluation of exercise capacity.
2- Evaluation of disability.
3- Differential diagnosis of exercise intolerance
4- Describing the rehabilitation program and assessing its efficacy.
5- Preoperative assessment
6- Functional and prognostic evaluation of patient with heart disease and patient with respiratory disease.
7- Assessing treatment efficacy.
The most important parameters:
VO2 and Peak Oxygen Uptake
VO2 is the volume of O2 extracted from the air inhaled during pulmonary ventilation in a period of time. It is usually expressed in mL/min or L/min.
In practice peak VO2 (VO2peak), that is the highest value reached at the end of an exhausting exercise test, is used alternatively to VO2max, both in healthy individuals and diseased populations.
VO2peak is considered abnormal when below 85% of the predicted value.
It is considered gold slandered test.
It has been used as a universal marker, which can reflect disease severity in patients with heart failure, pulmonary hypertension, hypertrophic cardiomyopathy, chronic obstructive pulmonary disease, and restrictive pulmonary disease, in addition to physical fitness level
Anaerobic Threshold = lactate threshold = gas exchange threshold = lactic acid threshold:
is considered an estimator of the onset of metabolic acidosis caused predominantly by the increased
rate of arterial lactate concentration during exercise.
The ability to achieve the AT can assist in differentiating cardiac and noncardiac causes of exercise limitation; fatigue before reaching AT is likely related to noncardiac causes.
Respiratory Exchange Ratio
It expresses the ratio between CO2 output and O2 uptake (VCO2/VO2). It is currently the best noninvasive indicator of maximal exercise intensity. Values above 1.0 can reflect intense exercise, but those ≥1.10 are those searched on CPET, and have been accepted as a parameter of maximal effort/exhaustion.
Continuous 12-lead electrocardiogram (ECG) monitoring, pulse oximetry, and frequent noninvasive blood pressure measurements are required as well, during CPET.
CPET can be performed using incremental or constant work rate protocols, according to the purpose of the test and the functional status of the patient.
On the day of the test, it is important for the patient to adhere to his medication. The haemoglobin should be within recommended level.
Absolute contraindications for the conduction of CPET:
1- acute or uncontrolled cardiovascular conditions (e.g., syncope, unstable angina, uncontrolled heart failure, acute myocardial infarction, and acute pulmonary embolism).
2- serious cardiac dysrhythmias on resting ECG.
3- Severe respiratory failure (PO2 ≤ 85% at rest).
Relative CT:
1- Severe electrolyte disturbance
2- Uncontrolled hypertension > 200/120
3- Neurologic disease
4- Orthopedic disease
Fick Equation
At maximal exercise, the Fick equation is expressed as follows:
VΟ2max = [(SVmax) × (HRmax)] × [(CaO2max) – (CvO2min)].
VΟ2max reflects the maximal ability of a person to take in, transport, and use oxygen; it, therefore, equals the functional aerobic capacity of that individual. In practice, however, VO2peak, that is,
the highest value obtained at the end of an exercise test to exhaustion is used as VO2max.
Exercise Intolerance
Exercise intolerance (or decreased exercise capacity) is defined by the presence of abnormally low VO2peak, of any cause.
Based on the Fick equation, any factor that may impair maximum cardiac output (e.g., heart failure) or
affect arterial or mixed venous oxygen content (e.g., diseases of the lungs, skeletal muscle dysfunction, or anaemia) may result in decreased VO2peak.
Exercise intolerance is highly prevalent in CKD and is associated with increased frailty, worsened quality of life, and a high risk of hospitalization and mortality.
As of this writing, CPET has been used in pilot observational studies that, in most cases, examine exercise capacity in patients with CKD versus non-CKD controls and, in some cases evaluate simple associations with other vascular parameters, such as endothelial function and arterial stiffness. In addition, CPET has been used in randomized trials examining the effect of exercise training.
It is level 5 of evidence.
Thank you for your reply, yes level 5
Cardiopulmonary exercise testing is a screening test to assess intigrity of several body systems and its interactive functions by increasing the workload and stress on the body. The involved systems in the assessments are Cardiovascular, respiratory, metabolic, anemia, and neuropsychological. Furthermore, assessment of exercise tolerance and cardiovascular reserve will be highlighted as well.
As cardiovascular mortality is the leading cause of death in patients with Chronic kidney disease, dut to mutiple common primary factors and other inherent factors stemmed from chronic kidney disease changes such as anemia, hypervolemia, hyperhomocystenemia, hyperparathyroidism and arteriosclerosis etc. Henceforth, the cardiovascular mortality is mutually epic during and post operatively. Therfore, cardiovascular reserve and pulmonary function level with exercise tolerance
The condition that can cause impaired CPST are multiple and involved different systems such us congestive heart failure,, pulmonary hypertension coronary artery disease, obstructive and restrictive lung diseases.
Several variable are assessed in this test as follow,
in order to assess the the physiological reserve of the cardiovascular and respiratory systems the CPFT is evaluating the extraction of O2 by the lungs and its transport to the muscles adequately in a volume that meet and deemed satisfactory for its metabolic needs. Therefore , the whole test is revolving around O2, CO2, and lactate.
CPET indexes:
VO2: Its the volume of O2 extracted from the air inhaled during s period of time.
VO2 max: The flattening of VO2-Work rate is often not seen in healthy subjects doing an incremental exercise. Therefore, VO2 max is the maximum volume of VO2 attainable for a certain exercise, which is reflected by failure of VO2 to increase despite the persistently increasing workload.
VO2 peak is the highest VO2 reached at the end of a strenuous exercise. which is considered abnormal when its below 85% of predicted value. Its the gold slandered for assessment of cardiopulmonary function. Furthermore , its considered a marker of disease severity.
Anaerobic threshold, Lactic acid threshold, gas exchange threshold AT:
Its reflecting the commencement of metabolic acidosis caused by the liberation of lactic acid from the tissues, its essentially related to VO2 peak pertaining to maximum expenditure of energy and deficiency of O2 supply.
The normal AT is at around 40-65 % of the VO2 peak. It depends on the VCo2 as well .
It can differentiate between cardiac and non cardiac causes of impaired exercise tolerance.
Respiratory exchange ratio:
Its the ratio between CO2 output and O2 uptake {VCO2/VO2} . Its reflecting the most sensitive non-invasive tool of assessment of maximum exercise intensity.
Contraindications for CPET:
uncontrolled cardiovascular conditions such as:
uncontrolled Hypertension
Cardiac failure.
unstable angina.
pulmonary hypertension.
Myocardial ischemia.
cardiac arrhythmias
Respiratory failure.
It was assessed in Pilot studies which revealed result that was uncomparable to counterparts with normal renal function in the term of lower predicted VO2 value, AT and other cardiovascular parameters.
This paper is a review article with level of evidence 4
Thank you for your reply, it is level 5 instead 4, but at least it is low in the hierarchy of evidence
Cardiopulmonary exercise testing (CPET) :
Level of evidence:5
Thank you for your reply, but it is too short
“CPET can delineate multisystem changes and offer comprehensive phenotyping of factors determining overall cardiovascular risk”. Please read this article and explain how the authors reaches this conclusion.
Cardiopulmonary exercise testing (CPET) is a dynam-ic, noninvasive technique that is useful in various clinical settings for diagnosis, risk stratification, and the evalua-
tion of response to cardiopulmonary therapies [20]. It islong considered to be the gold standard for evaluating thdegree and differentiating the causes, by unmasking
physiological mechanisms of exercise intolerance [21,
22].
Cardiorespiratory fitness reflects the ability of the car-diovascular and respiratory systems to transport oxygen to the working muscles of the human body during physi-
cal activity. Impaired cardiorespiratory fitness is strongly associated with early all-cause and cardiovascular-related mortality [11, 12]. Patients with CKD have lower cardio-
respiratory fitness than the general population; thiscurs early in the disease process, declines further with renal function drop, and is also associated with increased
aortic stiffness, poor left ventricular function, and higher risk of cardiovascular events [12–14].
Thus, exercise in-tolerance, a prognostic factor of morbidity and mortality is inherently associated with CKD [15–17].
CPET is being used increasingly in a wide spectrum of clinical ap-plications for evaluation of undiagnosed exercise intoler- ance and for objective determination of functional capacity and impairment [23, 24].
During CPET, a vast number of “routine” exercise testing variables and more sophisticated cardiorespiratory parameters are continuously (breath-by-breath) mea-
sured or estimated; this volume of physiological data obtained is necessary in order to assess each organ system response in coupling external respiration (i.e., oxygen up-
take (VO2) and carbon dioxide output at the airways) to cellular respiration (i.e., oxygen consumption and carbon dioxide production), during exercise.
What are the most important parameters derived by the CPET?
CPET involves measurements of respiratory oxygen uptake (Vo2), carbon dioxide production (Vco2), and ventilatory measures during a symptom‐limited exercise test.
VO2 and Peak Oxygen Uptake
VO2 is the volume of O2 extracted from the air inhaled during pulmonary ventilation in a period of time. It is usually expressed in mL/min or L/min. Historically, the
VO2 plateau demonstrated by a series of high intensityconstant work-rate tests was used to define maximumVO2 (VO2max), in healthy individuals. However, the flat-
tening of the VO2-work rate relationship is often not seen during incremental exercise tests; thus, VO2max is de-fined as the highest VO2 attainable for a given form of exercise, as evidenced by a failure for VO2 to further in-crease, despite a progressive increase in work rate.
In practice peak VO2 (VO2peak), that is the highest valuereached at the end of an exhausting exercise test, is used alternatively to VO2max, both in healthy individuals and diseased populations [26]. Mean values at intervals of 10–60 s should be measured depending on the protocol(short-interval means for protocols with short stages and
longer interval means for protocols with longer stages)
[27, 28].
VO2peak is considered abnormal when below85% of the predicted value [29].
VΟ2peak has become the“gold standard” laboratory measure of cardiorespiratory fitness and the most important measurement during thefunctional exercise testing. It has been used as a universal marker, which can reflect disease severity in patients with heart failure, pulmonary hypertension, hypertrophic cardiomyopathy, chronic obstructive pulmonary disease, and restrictive pulmonary disease, in addition to physical
fitness level [30].
Anaerobic Threshold
The anaerobic threshold (AT) (Fig. 1), also known as
the lactate threshold, lactic acid threshold, or gas exchange
threshold, is considered an estimator of the onset of met-
abolic acidosis caused predominantly by the increased
rate of arterial lactate concentration during exercise.
The ratio of pulmonary ventilation and O2 consumption (VE/VO2) or the ratio of pulmonary ventilation and CO2 production (VE/VCO2)
The carbon dioxide partial pressure at the end of expiration
AT or VT It is defined as the point at which minute ventilation increases disproportionately relative to VO2 oxygen pulse (VO2/HR) (in mLof O2/min/bpm).
It is the ratio between VO2 and the heart rateΔVO2/ΔWR relationship (VO2 in
mL/min and workload in watts)
It is the relationship between VO2 and workload. It is measured during exercise on acycle.
.
AT is referenced to the VO2 at which this change occursand is expressed as a percentage of the predicted value ofVO2peak (%VO2peak predicted). From the physiologicalviewpoint, AT represents the upper limit of workloadsduring exercise, which can be sustained over a prolongedperiod of time without progressively increasing arterial
blood lactate or as the level of exercise VO2 above whichaerobic energy production is supplemented by anaerobicmechanisms.
The normal mean AT values expected for
adults are around 40–65% of peak VO2 [29].
What is the level of evidence provided by this article?
level 5, based on physiology.
Thank you for your reply; yes level 5 it is a review article rather than on the nature of the article