Cardiopulmonary Exercise Test (CPET) PDF

Cardiopulmonary Exercise Test (CPET) Objectives: Define Cardiopulmonary Exercise Test (CPET) Discuss clinical applications for CPET Describe the basic exercise physiology underlying CPET Discuss the main CPET parameters Compare and discuss different test modalities used as part of CPET Di...

Cardiopulmonary Exercise Test (CPET) Objectives: Define Cardiopulmonary Exercise Test (CPET) Discuss clinical applications for CPET Describe the basic exercise physiology underlying CPET Discuss the main CPET parameters Compare and discuss different test modalities used as part of CPET Discuss CPET preparation and procedure What is Cardiopulmonary Exercise Test (CPET)? Cardiopulmonary exercise test (CPET) is a maximal exercise test with gas exchange analysis. What is CPET? CPET is the gold standard in assessing Cardiorespiratory Fitness (CRF) (or functional/exercise capacity) Cardiopulmonary Exercise Test (CPET or CPX), also known as Metabolic Test Assessment of the integrative exercise responses involving the pulmonary, cardiovascular and skeletal muscle systems Involves measurements of respiratory oxygen uptake, carbon dioxide production and ventilatory measures at rest and during a symptom-limited (maximal) exercise test. CPET: Clinical applications (common) Determine cause of unexplained SOB or dyspnea (cardiac vs. pulmonary limitation to exercise) Assess surgical risk Assess peri-surgical and postsurgical complication risk Assess the severity of respiratory disease Assess prognosis in various disease states Congestive heart failure patients (guide therapy, risk stratify patients with end-stage CHF for heart transplant) Exercise prescription (CR) Individualize Ex Rx to safely maximize exercise training CPET: Clinical applications  Peak exercise capacity (pVO₂, VO₂max) maximum ability of the cardiovascular system to deliver oxygen to exercising skeletal muscle and of the exercising muscle to extract oxygen from the blood  Chain of O₂ Delivery during Exercise The ability to perform exercise is related to the CV system capacity to supply O₂ to the muscles and pulmonary system’s ability to clear CO₂ from the blood via lungs. Under steady state conditions, O2 uptake and CO2 output measured at the mouth are equivalent to O2 utilization and CO2 production occuring at the cell level. Physiology of Exercise Exercise tolerance is determined by 3 factors: 1. Pulmonary gas exchange 2. Cardiovascular performance 3. Skeletal muscle metabolism Physiology of Exercise: The Fick Equation Fick Equation is important in understanding the assessment of functional exercise testing (CPET). The Fick equation states that oxygen uptake (VO₂) equals cardiac output (SV x HR) multiplied by the arterial venous O2 difference (arterial minus mixed venous O2 content): VO₂ = (SV x HR) x (Cao – Cvo) SV=stroke volume HR=heart rate Cao=arterial oxygen content Physiology of Exercise: The Fick Equation At maximal exercise, the Fick Equation is expressed as follows: VO₂max = (SVmax x HRmax) x (Caomax – Cvomax) This reflects maximum ability of a person to take in, transport and use oxygen. How well lungs work, how efficiently heart pushes blood to the muscles, and how effectively muscles extract and use O2 in the blood. VO2max defines functional aerobic capacity. Physiology of Exercise: The Fick Equation In healthy people, a VO₂ plateau occurs at near maximal exercise (best evidence of VO₂ max). It represents the maximal achievable level of oxidative metabolism involving large muscle groups. In clinical testing, a clear plateau may not be achieved before symptom limitation of exercise, therefore peak VO₂ (pVO₂) is used as estimate of VO₂max. Main Parameters of CPET 1. VO₂ (volume of O₂ consumed); VCO₂ (volume of CO₂ produced) 2. Respiratory Exchange Ratio (RER) or Respiratory Quotient (RQ) 3. Anaerobic Threshold (AT) or Ventilatory Threshold (VT), Lactate Threshold (LT) Parameters of CPET: VO₂ VO₂ - volume of O₂ consumed Expressed in mL/min (absolute); but usually expressed in mL/kg/min (relative) to facilitate intersubject comparison VCO₂ - volume of carbon dioxide produced in Parameters of CPET - RER Respiratory Exchange Ratio, RER (Respiratory Quotient, RQ) RER = VCO₂ / VO₂ Ratio calculated by dividing the volume of CO₂ produced by the volume of O₂ consumed RER gives an indication of resting energy substrate (main macronutrient metabolized) RER affected by diet RER may also be affected by anxiety level and hyperventilation Parameters of CPET - RER at rest Substrate Ratio 100% Carbohydrate 1.0 100% Fat 0.7 100% Protein 0.8 Normal RER (Mixed Diet) 0.82-0.85 Parameters of CPET – RER At rest, RER 0.82-0.85 (mixed diet range) With exercise (max effort), RER >1.09 ( as high as 1.29 at peak) RER >1.0 indicates anaerobic metabolism (lactic acid build up)  RER increases as CO₂ production rises at a greater rate than O₂ consumption Parameters of CPET – AT Anerobic Threshold (AT) (or VT, LT) Reflects the highest exercise level or level of oxygen consumption (VO₂) that can be sustained without developing metabolic acidosis (build up of lactic acid) Normal range between 40-80% of VO₂max (most 40-60%, as high as 80% well-conditioned athletes) Implications for exercise training (to determine the work levels for CR patients) Parameters of CPET – AT Anerobic Threshold (AT) Reflects rise in CO₂ that is disproportionate to the rise in O₂ Indicates a point of exercise where body has reached maximal aerobic capacity (starts relying on anaerobic energy production) Above AT, can no longer sustain prolonged workload Below AT, can maintain level of exercise comfortably Parameters of CPET VE – Expiratory Volume (Minute Ventilation) The amount of air brought into and out of the lungs every minute (Tidal volume x breathing frequency) L/min RR – Respiratory Rate (or Vf, frequency of ventilation) Breaths/min Vt – Tidal Volume the amount of air that moves in or our lungs with each respiratory cycle mL/min Parameters of CPET: Exercise responses VO2 and HR linear rise in relation to work rate. VCO2 and VE rise in relation to work rate up to anaerobic threshold (AT). VE may rise AT exponentially at the end of a true MAX test. Exponenti RER=1, intersection al ↑ in VE of VO2 and VCO2 A true MAX test: no further increase in HR and VO2, plateau Parameters of CPET: Determining AT -AT is the point where CO2 production rises disproportionately to O2 consumption (V-Slope Method) -RER will start to rise abruptly after AT, RER ~1.0 -Can double check: PETO2 & VE/VO2 (lowest point) (end tidal partial pressure for O2; maximal concentration of O2 at the end of an exhaled breath; ventilatory equivalent of O2) CPET: Normal Values CPET protocols: Treadmill vs Bike Treadmill Bike -walking on treadmill -may not be familiar more familiar -safer? -holding onto treadmill rails discouraged -less prone to induce (decreases metabolic artifact (better cost) quantification of metabolic cost?) -PVO₂ 5-10% higher -less expensive -less space Other measurements: O₂ Saturation Pulse Oximeter – electronic device that measures the saturation of oxygen carried in red blood cells (analyzes light source that passes through the finger to determine % of O₂ in red blood cells) can attach to finger (also forehead, nose, foot/toes, ears) limitations (can lead to inaccuracy): poor circulation, dark skin pigmentation, thick skin, smoker, dark nail polish, artificial nails Also, movement (more on the treadmill) Other measurements: O₂ Saturation Acquire a resting and exercise O2 saturation reading using the finger pulse oximeter. Normal Resting SpO2 value 95% or greater A drop of >3-5% during exercise is abnormal Abnormal SpO2 value is less than 88%, oxygen therapy is recommended CPET Pre-test instructions: Similar to regular GXT Take medications as usual Wear comfortable clothing/ footwear No heavy meal 2 hours before test (light snack ok) Avoid caffeine 2 hours before test Avoid smoking or vaping, intensive sports/ exercise before test Test Prep and Instructions Before the test- system warm-up, calibration Review referral- what is the indication for test? Explanation of test Patient history- any contraindications? Day of test- patient clinically stable? “any changes to your health since the test referral, any recent procedures or hospital visits?” Patient prep Test consent Demonstration? Which modality (bike/ treadmill)? Protocol? Adjustment of equipment (mask, mouthpiece/ head gear, seat height) CPET: Contraindications (Review) Absolute  Acute myocardial infarction within 2 days  Ongoing unstable angina  Uncontrolled cardiac arrhythmia or hemodynamic compromise  Active endocarditis  Symptomatic severe aortic stenosis  Decompensated heart failure  Acute pulmonary embolism, pulmonary infarction or deep vein thrombosis  Acute myocarditis or pericarditis  Acute aortic dissection  Physical disability that precludes safe and adequate testing CPET: Contraindications (Review) Relative Known obstructive left main coronary stenosis Moderate to severe aortic stenosis with uncertain relationship to symptoms Tachyarrhythmias with uncontrolled ventricular rates Acquired advanced or complete heart block Recent stroke or transient ischemia attack Mental impairment with limited ability to cooperate Resting hypertension with systolic >200 mm Hg or a diastolic >110 mm Hg Uncorrected medical conditions, such as significant anemia, important electrolyte imbalance and hyperthyroidism CPET procedure: Calibration Gas calibration- calibrate O2 and CO2 analyzers, ensures gas analyzers produce valid and reliable data (usually complete before each test) Verifying the accuracy of gas analyzers by exposing them to known concentration of gases Ambient (room) air (O2 20.93%, CO2 0.03%) to reference gas (O2 16%, CO2 5%) Flowmeter calibration- ensures device accurately measures the volume of air, usually required in the morning and afternoon (this may vary depending on CPET machine) CPET: Gas Analysis (mask, mouthpiece) CPET: Gas Analysis (mask, mouthpiece Mask vs. Mouthpiece Advantages?/ Disadvantages? Patient comfort (if using mouthpiece - dentures? anxious/claustrophobic? gag reflex?) Leak test/ “smile test” Test Procedure: Key Points Purpose of the test – include “what” “why” “how” Maximal effort Reporting of RPE (dyspnea, leg effort, or overall effort) Reporting of symptoms, communication of hand signals (ie., using 10-point scale modified Borg scale or 4- point scale, site specific) Mouthpiece (importance of tight seal) Treadmill- do not allow patient to hold onto the treadmill rails as this will produce inaccurate gas analysis (for balance support may need to rest hands against side rail) PATIENT SAFETY  General Indications for Termination of an Exercise Test ST elevation (>1.0 mm) in leads without preexisting Q-waves because of prior MI (other than aVR, aVL. Or V1)  Drop in systolic blood pressure of > 10 mm Hg, despite an increase in workload, when accompanied by other evidence of ischemia  Moderate-to-severe angina  Central nervous system symptoms (e.g., ataxia, dizziness, or near syncope)  Signs of poor perfusion (cyanosis or pallor)  Sustained ventricular tachycardia or other arrhythmias, including second- or third- degree atrioventricular block, that interferes with normal maintenance of cardiac output during exercise  Technical difficulties monitoring the ECG or systolic blood pressure  The subject’s request to stop  General Indications for Termination of an Exercise Test (continuation)  Marked ST displacement (horizontal or downsloping of >2 mm, measured 60 to 80 ms after the J point in a patient with suspected ischemia)  Drop in systolic blood pressure of >10 mm Hg (persistently below baseline) despite an increase in workload, in the absence of other evidence of ischemia  Increasing chest pain  Fatigue, shortness of breath, wheezing, leg cramps, or claudication  Arrhythmias other than sustained ventricular tachycardia, including multifocal ectopy, ventricular triplets, supraventricular tachycardia, and bradyarrhythmias that have the potential to become more complex or to interfere with hemodynamic stability  Exaggerated hypertensive response (systolic blood pressure of >250 mm Hg and/or a diastolic blood pressure of >115 mm Hg.)  Development of bundle-branch block that cannot be distinguished from ventricular tachycardia  SpO2 ≤80%  Test Prep: Explanation of test “Spiel” “You have been referred for a metabolic test as part of the Cardiac Rehab program. This information will be used to assess your functional capacity and used to determine your exercise prescription in the program. You will be attached to monitors that will measure your ECG, BP, and breathing while you exercise. You’ll breathe through a mouthpiece connected to a monitor that will measure how much oxygen you breathe in and how much carbon dioxide you breathe out. It is important that you keep a tight seal throughout to ensure accurate measurements. Nose clips will be placed on your nostrils to ensure all the breathing is done through the mouth. You will exercise on the treadmill/bike; it will be easy at first and then progressively harder with time. This is a maximal test so exercise for as long as you can and give your best effort.”  Test Prep: Explanation of test “Spiel” (continuation) “Throughout the test, I’ll ask you to rate your level of effort. This is a scale from 0-10 that will be used to monitor how difficult you perceive the work you are doing; where 0 is no effort and 10 is working as hard as you ever have. We ask you not to speak and every couple of minutes, I will ask you to point to the number from 0 to 10 that corresponds to your level of effort. We expect that at the end of the test you will be closer to a rating of 10. When you can’t continue, please raise your hand and I will stop the test. Know that your legs will get tired and you will get short of breath, these are normal with exercise, but if you should develop any unusual symptoms such as chest discomfort or muscle/joint pain, please indicate that to me by pointing to your chest or part of your body if able. At this time, we can discuss your symptoms further. Do you have any questions? Are you ready to proceed?”  Test Prep and Instructions Data Entry- Demographics (age, height, weight, ethnicity) reference values (% predicted normal values) Test modality selection - site specific Treadmill vs bike Consider patient’s limitations if option to use different modalities Which patient population more appropriate for treadmill? bike? Protocol selection – site specific based on exercise history, age, patient limitations Treadmill- no set guidelines, different ramping protocols (Bruce Ramp, Naughton) Bike- 10 Watts/min, 15 Watts/min, 20 Watts/min, 25 Watts/min Protocol should max the patient in 8-12 minutes Test Prep and Instructions Spirometry prior to CPET Provides baseline info about patient’s lung function, helps with CPET interpretation (lung vs. heart problems). MVV (maximum voluntary ventilation; maximum level of ventilation by patient per minute, L/min); calculated (indirectly) as FEV1 x 40. Breathing reserve (BR)(%) = MVV – VEmax/ MVV x 100 (determine ventilatory limitation) References American College of Sports Medicine. (2018). ACSM’s guidelines for exercise testing and prescription (10th ed.). Lippincott Williams & Wilkins. American Lung Association. (n.d.). Pulse oximetry. https://www.lung.org/lung-health-diseases/lung-procedures-and-tests/pulse-oximetry#:~:text=Th e%20pulse%20oximeter%2C%20or%20Pulse,%2C%20foot%2C%20ears%20or%20toes Chambers, D. J., & Wisely, N. A. (2019). Cardiopulmonary exercise testing-a beginner's guide to the nine-panel plot. BJA education, 19(5), 158–164. https://doi.org/10.1016/j.bjae.2019.01.009 Glaab, T., and Taube, C. (2022). Practical guide to cardiopulmonary exercise testing in adults. Respiratory Research, 23 (9), 1-12. https://respiratory-research.biomedcentral.com/articles/10.1186/s12931-021-01895-6#citeas Radtke, T et al. (2019). ERS statement on standardization of cardiopulmonary exercise testing in chronic lung diseases. European Respiratory Review, 28, 1-25. https://err.ersjournals.com/content/28/154/180101 Triantafyllidi, H., Birmpa, D., Benas, D., Trivilou, P., Fambri, A., & Iliodromitis, E.K. (2022). Cardiopulmonary exercise testing: The ABC for the clinical cardiologist. Cardiology, 147, 62-71. https://karger.com/crd/article-pdf/147/1/62/3708642/000520024.pdf