Cardiopulmonary Exercise Testing: Indications, Interpretation & Cases
The Cardiopulmonary Exercise
Test ( CPET) is an extremely
valuable but underutilized
non-invasive examination. The
Exercise Health and Sports Cardiology Committee would like to promote
CPET as an effective tool in
evaluating cardiac function.
Authors, alphabetical order
- Gerald Bourne, MD, FACC, The Adaptive Behavior Institute, Kensington, CA
- Elizabeth H. Dineen, DO, Assistant Clinical Professor, University of California Irvine, School of Medicine, Division of Cardiology
- Jeffrey H. Dwyer, PhD, Department of Cardiology, Kaiser Permanente Medical Center, Vallejo, CA
- Victor Froelicher, MD, Professor of Medicine, Stanford University, Palo Alto VA Medical Center, Division of Cardiology
- Jonathan Myers, PhD, Exercise Physiologist/Cardiopulmonary Specialist, Director, Cardiopulmonary Research, Stanford University, Palo Alto VA Medical Center
- on behalf of the CA ACC Exercise Health and Sports Cardiology Committee
- For questions, contact us at SportsCardio@caacc.org
- Figures 1 - 9: Sample findings in CPET Testing
- How to Perform a Cardiopulmonary Exercise Test
- Cardiopulmonary Exercise Test Case Studies
- Heart Failure
- Coronary Artery Disease
- Dyspnea of Unknown Etiology
- Chronic Fatigue Syndrome (CFS) / Post-Exertional Malaise (PEM)
- Exercise Prescription and Training
- CPET Resources
Exercise Health & Sports Cardiology Committee
The American College of
Cardiology’s California Chapter
has established an Exercise Health and Sports Cardiology Committee in response to the
growing need for evidence-based,
standardized, comprehensive care
for athletes. The committee aims
to serve as a resource for
assessment of highly active
individuals as well as a home
for educational tools to aid in
their assessment and management.
IntroductionPhysical activity requires the integrated performance of cardiovascular, pulmonary, metabolic, and neuromuscular systems. The Cardiopulmonary Exercise Test (CPET or CPX) evaluates the concerted response of these systems during exercise and provides an assessment of each component required for exercise performance. In contrast to standard exercise test modalities, the defining element of CPET is the continuous measurement of ventilation and gas exchange.
The relationship between oxygen consumption and carbon dioxide production and a vast array of non-invasive physiological parameters are used to determine the function of each component of physical exertion. From rest, through moderate exercise, to exhaustion, CPET enables an evaluation of overall capacity of the subject and the physiologic integrity of each system from ventilation, to circulatory transport, to tissue uptake. Although the significance of disturbances in the relationships between physiologic systems measured during CPET may be initially daunting, the utility and indications for this test are important and easy to understand.
Cardiopulmonary fitness is determined by measuring oxygen uptake (V̇O₂) at maximal exercise, while the ventilatory (anaerobic) threshold (VT) occurs at a submaximal point during exercise when pulmonary ventilation increases disproportionately to oxygen uptake. Cardiovascular limitations are exemplified by low values for peak V̇O₂ and ventilatory threshold. The ratio of oxygen uptake to work rate is reduced due to an impaired ability of the cardiopulmonary system to provide oxygen to the working muscles. A low stroke volume may be reflected by a low peak V̇O₂ per heart beat (O₂ pulse). Pulmonary limitations that may result in a reduced V̇O₂ are revealed by an abnormal breathing reserve, oxygen desaturation, CO₂ retention, or abnormal expiratory flow rate. Peripheral myopathy is suggested by a low peak V̇O₂ , with an elevated minute ventilation to V̇O₂ ratio and a high cardiac output to V̇O₂ slope. Further discrimination of the cause of exercise intolerance can be determined by evaluating the relationships between additional variables. Endurance athletes commonly will have findings on CPET that may be considered abnormal in the sedentary population. These athletes may have higher peak V̇O₂ , higher anaerobic threshold, a high O₂ pulse reflecting a higher stroke volume and a maximum exercise ventilation that nearly matches the maximum voluntary ventilation, such that the breathing reserve is nearly zero given their exceptionally high cardiovascular capacity.
Sample findings in CPET TestingView Slides Below in PDF Format [best for mobile device]
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Dyspnea of unknown etiologyCPET can help differentiate between pulmonary, cardiac, neurologic, muscular and psychological basis of dyspnea that limits exercise performance.
Diagnosis and assessment of the severity of organ dysfunction,
relative compensatory contributions of other organ systems,
prognosis, sequential monitoring in the following disease
processes.Heart Failure with reduced ejection fraction
Heart Failure with preserved ejection fraction
Valvular Heart Disease
Congenital Heart Disease: Persons with CHD often have abnormal recognition of DOE
Coronary Artery Disease.
PulmonaryPulmonary Artery Hypertension
Secondary Pulmonary Artery Hypertension
Chronic Obstructive Pulmonary Disease
Interstitial Lung Disease
Chronic Fatigue/ Post Exertional Malaise
Assessment of Surgical RiskCPET responses have been increasingly applied to stratify risk as part of pre-surgical assessment. For example, peak V̇O₂ strongly predicts risk for surgical complications, length of hospital stay, and ability to return to work across a wide spectrum of surgical interventions.
Development of Cardiac or Pulmonary Rehabilitation exercise prescriptions and guidelinesThe foundation of an appropriate exercise prescription in a patient with cardiovascular or pulmonary disease is the exercise test, and because of its superior precision, the CPET provides the most accurate method to develop an individualized exercise prescription.
Assessment of safety and metrics for an exercise training programThe CPET provides a wealth of information on safety, rhythm abnormalities, ischemic responses, and symptoms that are important in developing a safe and appropriate exercise prescription.
Assessment of cardiorespiratory fitness and subsequent response to a training program or interventions in healthy individuals, athletes or those with underlying cardiovascular disease (as listed above)The CPET provides an accurate metric to quantify changes in fitness in response to exercise training and other interventions (eg. drug, surgical or device) among both healthy individuals and those with cardiovascular disease.
Equipment and StaffCPET test administration requires specific equipment and personnel in order to generate accurate and reliable data.
EquipmentErgometer (cycle, treadmill, rowing simulator, etc)
Gas exchange mask/mouthpiece
Metabolic cart consisting of gas analyzers, expiratory gas flow and volume, and software
Blood pressure measurement device
PersonnelExercise physiologist to set up the exercise protocol, prepare/calibrate equipment and possibly monitor during the test
Medical assistant or nurse to monitor during the test
Qualified medical professional for interpretation of the test
Many patients can be tested on a cycle ergometer or treadmill, based on comfort level and lab availability. If testing athletes, the type and intensity of the test protocol should be matched to their sport (ex: having a sprinter perform sprints on a treadmill or a rower using the rowing ergometer) which will provide more useful test results. Cycle tests are logistically easier for monitoring blood pressure and generate electrocardiogram tracings with fewer artifacts and unstable baselines.
The exercise protocol will vary depending on the interview conducted by the ordering provider. Common exercise protocols include the step protocol (ex: Bruce-type protocol), with a step-wise or incremental increase in work rate over time, or a ramp protocol with a continuous increase in work rate over time. The exercise test should be individualized by the exercise physiologist or medical provider administering the test with a target test time between 8-12 minutes.
Key MetricsHeart rate, blood pressure, and electrocardiographic responses to exercise should be evaluated in a similar fashion as a routine exercise test
Ventilation and Gas Exchange: Measured throughout exercise
Maximum V̇O₂ : This is the aerobic capacity or total body oxygen uptake verified by achieving a heart rate within 10 bpm of the age-predicted HRmax, a lack of change in the V̇O₂ over two consecutive work rates, and/or a respiratory exchange ratio above 1.10 (presumably reflecting a lactate accumulation above 70-80 mg/dl). If these criteria cannot be met, the oxygen uptake at maximally tolerated exercise is referred to as peak V̇O₂ . V̇O₂ is often a metric that is tracked over time to monitor treatment or interventions as well as to monitor disease progression or prognosis.
V̇CO₂: Carbon dioxide elimination measured throughout the test.
Lactate Threshold V̇O₂ ≈ Anaerobic Threshold ( AT ) ≈ Ventilatory Threshold ( VT ): V̇O₂ above which lactate accumulates in the blood. This may be a useful marker of an individual’s cardiorespiratory fitness and endurance. Often referred to as anaerobic threshold or ventilatory threshold. Can be determined by ventilatory analogs of lactate accumulation such as V̇O₂ vs V̇CO₂ and V̇E vs V̇O₂ graphs.
Respiratory exchange ratio (RER): The ratio of CO₂ produced to oxygen consumed (V̇CO₂/V̇O₂). A marker of fuel utilization (0.70 ≈ fat utilization and ≥1.0 ≈ carbohydrate utilization). Also a reflection of the degree of physiologic effort (≥1.10 associated with maximal effort)
Oxygen Pulse (V̇O₂ /HR): Will increase at the beginning of exercise largely due to the increase in stroke volume and then will reach a plateau near the end of exercise. If this plateau is reached sooner than expected, it can be due to impaired oxygen extraction or impaired stroke volume (due to CAD or left ventricular dysfunction).
Pulmonary Ventilation (V̇E): Volume of air exhaled per unit time. Generally not a limiting factor unless there is a low breathing capacity or a disease state that impairs air flow.
Change in V̇O₂ /change in work rate: This generally has a linear relationship of 10 mL/min of oxygen uptake for every 1 Watt increase in work rate. This relationship may change in illnesses such as cardiovascular diseases where oxygen uptake may be decreased compared to change in work rate.
Heart rate recovery: Reflection of vagal reactivation. Slow heart rate recovery associated with higher adverse outcomes. Often expressed as 1-minute post exercise (HRR1) or 2-minutes post exercise (HRR2). HRR1 <12 beats/min or HRR2 <22 beats/min associated with higher risk.
V̇E/V̇CO₂: Can be expressed as a ratio (at a point in time during exercise) or as the slope of the change during exercise. Reflects ventilatory efficiency, ie. the ventilatory requirement to eliminate a given amount of CO₂, and is a strong prognostic marker.
Oxygen uptake efficiency slope (OUES): The relation between the change in oxygen uptake during exercise and the log of the change in ventilation. The OUES is another measure of ventilatory inefficiency, and is a strong predictor of prognosis in patients with heart disease.
Perceived exertion: A reflection of the degree of the individual’s physical effort. Often expressed using a 6-20 scale, with 6 representing a resting state and 20 representing maximal effort.
HistoryThe patient is a 60 year old sedentary Caucasian male outpatient 71 inches tall, weighing 180 lbs. He is currently not smoking but has 23 pack years of smoking (1 pack/day for 23 years). The patient’s weight is normal (BMI=25). A history of abnormal lipids was reported (high TC, LDL, low HDL). The patient also has a history of high blood pressure. He over the past 6 months has noted increasing shortness of breath with exertion.
Reason for ReferralEvaluation of increasing shortness of breath with regular daily activities.
Past Medical HistoryThere is a history of “mildly reduced ventricular function”, diagnosed approximately 6 years ago, although no imaging results are available. He reports infrequent “skipped beats”. No other history of non-cardiac or other medical problems are noted. Current medications include an ACE inhibitor, statin, and diuretic.
CPX Test ResultsRest:
|Exercise time (min:sec)||4:43|
|Heart rate (beats/min)||98|
|Oxygen uptake (ml/kg/min)||7.7|
|Oxygen uptake (ml/min)||630|
|V̇O₂ % peak||57%|
|Peak Exercise||Reason for stopping - Shortness of Breath|
|Exercise time (min:sec)||11:14|
|Systolic blood pressure (mmHg)||166|
|Estimated METs||5.1||Ventilatory Efficiency|
|Oxygen uptake (ml/kg/min)||13.4||(40.4% predicted)||V̇E/V̇CO₂ Slope||38.7|
|Oxygen uptake (ml/min)||1,096||OUES||1.18|
|V̇CO₂ (ml/min)||1,243||Peak V̇E/V̇O₂||41.0|
|O₂ pulse (ml/beat)||7.50|
|RER||1.13||Breathing Reserve 27.5%|
|SaO₂||96||HRR1 = 5|
|Perceived exertion||20||HRR2 = 16|
View Figure 2, 3, 4 of Sample Findings in CPET Testing [pdf]
HistoryThe patient is a 68 year old sedentary Caucasian male outpatient 65 inches tall, weighing 160 lbs. The patient is currently not smoking but has a 50 pack year history of smoking (2 packs/day for 25 years). The patient is 10 lbs over the average appropriate body mass index (BMI=26.6) which qualifies as overweight. A history of abnormal lipids was reported (high TC, LDL, low HDL). The patient also has a history of high blood pressure.
Reason for ReferralEvaluation of chest pain
Past Medical HistoryThe patient has the following symptoms: shortness of breath with regular daily activities and occasional mild chest discomfort. There is no other history of cardiac disease, cardiac events or dysrhythmias. No other history of non-cardiac or other medical problems are noted. Current medications include a beta blocker, ACE inhibitor, statin, and diuretic.
CPX Test ResultsRest:
|Oxygen uptake (ml/kg/min)||8.2|
|Oxygen uptake (ml/min)||868.4|
|V̇O₂ % peak||71%|
|Peak Exercise||Reason for stopping - Shortness of Breath (with slight chest pain)|
|Exercise time (min:sec)||8:01|
|Systolic blood pressure (mmHg)||180|
|Estimated METs||6.0||Ventilatory Efficiency|
|Oxygen uptake (ml/kg/min)||11.5||(62% predicted)||V̇E/V̇CO₂ Slope||35.9|
|Oxygen uptake (ml/min)||1,215||OUES||1.48|
|V̇CO₂ (ml/min)||1,470||Peak V̇E/V̇O₂||34.40|
|O₂ pulse (ml/beat)||12.3|
|RER||1.21||Breathing Reserve 23%|
|SaO₂ %||95||HRR1 = 10|
|Perceived exertion||19||HRR2 = 16|
History of Current ComplaintPatient is a 62 y-o female who reports dyspnea on exertion of progressive intensity and frequency over the past eight months. She denies symptoms at rest and in self-care activities. Unable to climb a flight of stairs without stopping to catch her breath. Stopped exercising on her stationary cycle 4 months ago due to fatigue and SOB. She denies chest pain but reports occasional tightness or pressure when she is severely SOB.
Reason for ReferralDyspnea of unknown origin; is it cardiac, pulmonary, or deconditioning?
Past Medical HistoryFour years ago, the patient had NSTEMI; symptoms were chest tightness, mid-scapular pain, and severe dyspnea. Two stents placed in culprit RCA. LAD and LCX with luminal irregularities. 90% stenosis in OM1 and OM2 treated medically. HTN, Type-2 DM, obesity; stopped smoking 8 years prior to NSTEMI. No asthma. PFTs two years ago with normal. BMI above 30.0 for the past 20 years with recent 15-pound weight gain.
CPX Test ResultsExercise Performance:
Key CPX Variables
PeakV̇O₂ is only mildly reduced
Oxygen-pulse is low-normal consistent with a normal stroke volume
Low AT and elevated V̇O₂/Watts
Fast Vf with reduced Vt; the result of forced expiratory efforts limited by progressively collapsing small airways as the patient ventilated low in her FVC. This abnormal ventilatory pattern invariably creates sensation of SOB and may result in CO₂ retention as demonstrated by this patient.
ConclusionPatient’s dyspnea is pulmonary in origin. Patient is deconditioned.
View Figure 8 of Sample Findings in CPET Testing [pdf]
History of Current ComplaintPatient is a 52 yo female who reports weakness in arms and legs for the past 14 years. Over the past 4 years, she has experienced profound fatigue after mild activity that may last for days. She discontinued using her stationary cycle two years ago. She felt compelled to quit her job due to fatigue and weakness. When deeply fatigued, she has short-term memory deficits and a sensation she describes as “brain fog.”
Reason for ReferralTwo-Day CPX (24-hour interval) to document functional capacity on Test-1 and Test-2; identify bio-markers consistent with CFS/PEM.
Past Medical HistoryPatient never smoked. No DM, HTN, hyperlipidemia, renal or pulmonary disorders. Muscle CK and inflammatory markers are negative. Normal echocardiogram. No previous exercise tests. Normal blood panel and Chem-7.
CXR is normal.
CPX Test ResultsPFTs:
|PeakV̇O₂ (ml/kg/min)||Max Work Watts||V̇O₂ @AT (ml/kg/min)||Work@AT Watt||
(ml V̇O₂ /Watt)
|* Normal range: 8.7-11.9 ml/min/Watt|
Key CPX Variables
ConclusionExercise is limited by muscular fatigue, greater in Test-2, associated with reduced peakV̇O₂ , maximal work rate, work at V-AT, and an increased V̇O₂ per unit work, consistent with PEM/CFS as described in the literature.
HistoryPatient is a 70 yo female who requests exercise evaluation and prescription in preparation for attempts to climb to base-camp on Mount Everest (17,500 feet) and Mount Kilimanjaro (19,341 feet). She denies chest discomfort when exercising.
ReferralAssess peakV̇O₂ , ventilatory anaerobic threshold (V-AT), and optimal target HR six months prior to climbing events to provide training guidelines ( TEST 1). Perform second CPX two weeks prior to the event to assess progress and status ( TEST 2).
Past Medical HistoryNo HTN, hyperlipidemia, diabetes, pulmonary disease, cardiac disease. Never a smoker. BMI = 22.48. She is active and participates in Pilates and Zumba exercise classes.
CPX Test Results10 Watts ramp cycle protocol.
|Test 1||Test 2||% Change|
|Watts @ V-AT||60 W||75 W||+25.0|
|V̇O₂ /Watts (ml V̇O₂ / Watt)||9.5||11.9||+25.0|
|HR max (bpm)||168||170||+1.2|
|% age-pred HRmax||112%||113%||-|
|Oxygen-pulse (ml V̇O₂ / HR)||8.3||9.2||+10.8|
|HR/V̇O₂ slope (beat / ml V̇O₂ )||3.5||3.9||+8.6|
|HR @ V-AT||130||141||+8.5|
|%HRmax @ V-AT||77%||83%||-|
|ECG||No ECG Change||No ECG Change||-|
|Peak systolic BP||142/81||152/78||+7.0|
|V̇ E MAX (L/min)||52.2||60.1||+15.0|
|PetCO₂ (mm Hg)||38||36||-5.0|
|Peak V̇E / V̇CO₂ (LV̇E/LV̇CO₂)||34.8||35.0||+2.8|
Key CPX Variables
ConclusionPatient’s baseline (Test-1) indicates an exceptional fitness status:
Training at the prescribed target intensities;
Textbook: Principles of Exercise Testing and Interpretation 5th Edition. Authors: Karlman Wasserman, James E. Hansen et al. Marco Guazzi, Francesco Bandera, Cemal Ozemek, David Systrom, Ross Arena.
Marco Guazzi, MD, PHD,a Francesco Bandera, MD, PHD,a Cemal Ozemek, PHD,b David Systrom, MD,c,d Ross Arena, PHDb, Cardiopulmonary exercise testing: what is its value? J Am Coll Cardiol. 2017 Sep, 70 (13) 1618-1636.
Guazzi M, Adams V, Conraads V, et al. EACPR/AHA Scientific Statement. Clinical recommendations for cardiopulmonary exercise testing data assessment in specific patient populations. Circulation. 2012 Oct;126(18):2261-2274. DOI: 10.1161/cir.0b013e31826fb946.
1. To add value to our membership by educating our members
in diagnosis and treatment of athletes.
2. To raise the awareness of Exercise Health to the Californians
thereby reducing and preventing Cardiovascular related morbidity
The ACC is THE Professional Home for Cardiovascular Specialists and the Care TeamTo represent YOU, the ACC is actively working on:
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Transformation of Care