Introduction to Exercise Testing PDF

Summary

This document provides an introduction to exercise testing, focusing on responses of the cardiovascular and ventilatory systems to exercise. It covers key concepts like VO2 max, METs, and maximum heart rate, along with the factors influencing these measures. An important resource for physical therapy and related health sciences students, professors, and practitioners.

Full Transcript

# Introduction to Exercise Testing ## By Dr. Sherif Osama Elabd Lecturer at physical therapy for internal medicine department, faculty of physical therapy May University. ## What is the Exercise Testing? Exercise testing is the study of responses of the cardiovascular and ventilatory systems to...

# Introduction to Exercise Testing ## By Dr. Sherif Osama Elabd Lecturer at physical therapy for internal medicine department, faculty of physical therapy May University. ## What is the Exercise Testing? Exercise testing is the study of responses of the cardiovascular and ventilatory systems to known exercise stress. It is an exercise test for analyzing both diagnostic and prognostic assessment by evaluating both submaximal and peak exercise response involving the pulmonary, cardiovascular, hematopoietic, neuropsychological, and skeletal muscle systems. CPET is aimed at the evaluation of exercise performance, functional capacity, and impairment by assessing undiagnosed exercise intolerance and exercise-related symptoms. ## Cardiac and Respiratory Response to Exercise * **Ventilation** to deliver oxygen to the alveoli and eliminate carbon dioxide. * **Gas exchange** to move oxygen from the alveoli to the blood and carbon dioxide from the blood to the alveoli. * **Maintenance** of hemoglobin stores to bind and carry oxygen to the tissues. * **Delivery** of oxygenated blood to the exercising tissues and carbon dioxide to the lungs. * **Extraction** of oxygen by the muscle mitochondria where ATP is generated to support muscle contraction. ## To assess an individual's capacity to perform all of these tasks and conduct sustained, vigorous exercise, one of the most useful parameters is the maximum oxygen consumption or VO2 max ### VO2 max Oxygen consumption (VO2) describes how much oxygen is being used by the tissues per minute, while maximum oxygen consumption (VO2max) is the amount of oxygen being used at peak exercise. ### Fick equation: $VO_2 = Q \times (CaO_2 - CVO_2)$ $CaO_2 = [(1.39 \times Hb \times SaO_2) + (0.003 \times PaO_2)]$ $CVO_2 = [(1.39 \times Hb \times SVO_2) + (0.003 \times PVO_2)]$ * Like heart rate, there's no one "good" VO2 max. Your VO2 max will differ from someone else's based on age, gender, fitness level and outside factors like altitude. * The average sedentary (inactive) male achieves a VO2 max of about 35 to 40 mL/kg/min, and the average sedentary female scores approximately 27 to 30 mL/kg/min. * Oxygen consumption is therefore dependent on the hemoglobin concentration, the arterial partial pressure and saturation of oxygen (reflecting the adequacy of the ventilatory pump and gas exchange), and the mixed venous saturation and partial pressure of oxygen (reflecting the ability of the tissues to extract and utilize oxygen). As a result, VO2max gives us information about many of the systems that are necessary to generate sustained, vigorous exercise; the higher the VO2max, the more effective all of these systems are at performing their tasks and the greater the person's exercise capacity. ## The metabolic equivalent (MET) * It is defined as the amount of oxygen consumed while sitting at rest and is equal to 3.5 ml O2 per kg body weight x min. * So, for example, if you weigh 160 pounds (72.5 kg), you consume about 254 milliliters of oxygen per minute while you're at rest (72.5 kg x 3.5 mL). * Energy expenditure may differ from person to person based on several factors, including your age and fitness level. For example, a young athlete who exercises daily won't need to expend the same amount of energy during a brisk walk as an older, sedentary person. | MET Categories | | | :-------- | :-------- | | **Light** | **< 3.0 METS** | | Sitting at a desk: 1.3 | Sitting, playing cards: 1.5 | | Standing at a desk: 1.8 | Strolling at a slow pace: 2.0 | | Washing dishes: 2.2 | Hatha yoga: 2.5 | | Fishing (sitting): 2.5 | **Moderate** | | | **3.0-6.0 METS** | | | Housework (cleaning, sweeping): 3.5 | | | Weight training (lighter weights): 3.5 | | | Golf (walking, pulling clubs): 4.3 | | | Brisk walking (3.5-4 mph): 5 | | | Weight training (heavier weights): 5 | | | Yard work (mowing, moderate effort): 5 | | | Swimming laps (leisurely pace): 6 | | | **Vigorous** | | | **> 6.0 METS** | | | Walking at very brisk pace (4.5 mph): 6.3 | | | Bicycling 12-14 mph (flat terrain): 8 | | | Circuit training (minimal rest): 8 | | | Singles tennis: 8 | | | Shoveling, digging ditches: 8.5 | | | Competitive soccer: 10 | | | Running (7 mph): 11.5 | ## Maximum Heart Rate * Maximum heart rate is the highest number of heart beats per minute (bpm) when exercising maximally. This is best measured during a maximal exercise test (direct measurements), in which the body is pushed to its physical limit. * **The calculation is simple with this method:** 226- your age for women, 220 - your age for men. * **Target Heart Rate** = [(max HR - resting HR) x %Intensity] + resting HR * **The American Heart Association generally recommends a target heart rate of:** * **Moderate exercise intensity:** 50% to about 70% of your maximum heart rate * **Vigorous exercise intensity:** 70% to about 85% of your maximum heart rate ## Exercise Responses in Normal Individuals * **A) ARTERIAL PARTIAL PRESSURE OF CARBON DIOXIDE (PaCO2) (--- & ↓) :** It reflects a balance between how much carbon dioxide is produced in the tissues on the one hand and eliminated in the lungs by alveolar ventilation on the other. This parameter remains relatively constant during exercise until the ventilatory threshold is reached because alveolar ventilation increases at a rate proportional to the increasing quantities of carbon dioxide being produced in the tissue. * **B) ARTERIAL PARTIAL PRESSURE OF OXYGEN (PaO2) (-):** This parameter remains relatively constant throughout exercise. * **C) ARTERIAL pH (--- & ↓) :** The blood pH remains constant until the ventilatory threshold when it begins to fall because the increase in minute ventilation, and subsequent respiratory alkalosis, is not sufficient to fully compensate for the developing metabolic acidosis. * **D) CARDIAC OUTPUT (Q) (↑):** As work rate increases, cardiac output increases in a linear fashion before leveling off near peak exercise. * **E) HEART RATE (↑):** This increases in a linear manner as work rate or VO₂ increases until peak exercise when it plateaus. * **F) MINUTE VENTILATION (VE) (↑):** It refers to the volume of air exhaled in 1 minute. The units of this parameter, which is measured at the mouth, are liters/minutes. This initially increases in a linear fashion as power output and VO2 increase. This increase is due to increases in both respiratory rate and tidal volume. * **G) OXYGEN SATURATION (SaO2) (---):** Given that the PaO2 remains constant throughout exercise, oxygen saturation should remain constant as well. * **H) OXYGEN CONSUMPTION (VO2) (↑) :** This parameter increases in a linear manner as work rate increases until a plateau is reached at maximum effort. Individuals cannot continue to exercise for very long once they reach their VO2max, although highly fit individuals can sustain exercise at this level longer than normal subjects. In normal individuals, VO2max should be more than 80% predicted for that individual based on their age, height, and gender. * **I) RESPIRATORY EXCHANGE RATIO (R) (↑):** R is the ratio of carbon dioxide output to oxygen consumption (VCO2 / VO2). At rest this value depends on the balance between fat and carbohydrate metabolism, and usually ranges from 0.8 to 0.9. With increasing levels of exercise, carbohydrate utilization becomes a progressively larger fraction of the metabolic fuel. As a result, R increases progressively. After the onset of the ventilatory threshold, VCO₂ rises to a greater extent than VO2 and R rapidly rises to levels as high as 1.1-1.3. * **J) STROKE VOLUME (↑) :** During upright exercise, two pumps facilitate cardiac output: the heart pumping blood into the aorta, and the calf capacitance veins and their valves, pumping blood from the legs back into the vena cava. Stroke volume, which as noted above is estimated using the O₂ pulse (Oxygen consumption/HR), increases with the onset of exercise, primarily because of the mobilization of blood in the venous capacitance vessels in the legs while in the later stages of exercise stroke volume increases only minimally as a result of increased inotropic activity. * **K) SYSTEMIC BLOOD PRESSURE (↑):** This parameter increases with exercise due to a rise in cardiac output and increase in vascular resistance in the renal, splanchnic, and skin circulations. In normal individuals, there is usually a step-change in the systolic pressure near the ventilatory threshold, after which systemic pressure can often reach very high levels. In fact, it is not uncommon for normal individuals to have systolic pressures rise into the 200 mmHg range at peak exercise. Diastolic pressure will ordinarily decrease modestly throughout exercise, reflecting vasodilation of the exercising muscle beds. * **L) TIDAL VOLUME (VT) (↑):** The tidal volume (VT) increases until around the time of the ventilatory threshold after which time it tends to level off at about 60% of the individual's vital capacity. ## Exercise Testing When deciding on the most appropriate exercise test, consider: * **The primary purpose of the test.** * **The workload intensity achieved during the assessment and its implication for risk.** * **The clinical risk of the patient and the setting in which testing will be undertaken.** * **Whether the assessment will also be used for research or to evaluate your service.** If so, strict adherence to testing procedure guidelines will promote validity and reproducibility of results. * In clinical settings, submaximal_exercise testing is used more commonly than maximal testing as it is easily administrated, less likely to cause adverse events and does not require medical supervision and ECG monitoring. * **Most submaximal, non-diagnostic tests are performed while the patien is taking their normal medication.** HR-based calculations are complicated by medications that alter HR response during exercise (e.g., such as beta-blockers). Therefore, it is important to document all medications at the time of assessment and consider cardiac medications that impact on exercise response. * **HR response may not be a reliable guide to exercise prescription so it is useful to also use the The Rating of perceived exertion (RPE) - Borg scale.** * **Perceived exertion is particularly important for patients taking beta-blockers.** HR, blood pressure (BP, oxygen saturation, RPE and any symptoms should be recorded. The test should be terminated if the patient's HR exceeds the pre-determined limit or if symptoms develop. * **Which Borg Scale?** Rating of perceived exertion (RPE) is commonly used to monitor and prescribe exercise intensity. The original Borg Scale ranged from 6-20 and was developed to correlate with HR. The modified Borg Scale is a category ratio on a scale of 0-10. | **20-Grade Scale** | | | :-------- | :-------- | | 6 | Very, very light | | 7 | Very light | | 8 | | | 9 | | | 10 | Fairly light | | 11 | | | 12 | | | 13 | Somewhat hard| | 14 | | | 15 | Hard | | 16 | | | 17 | | | 18 | | | 19 | Very hard | | 20 | Very, very hard | ## Indication of Exercise Testing * **Diagnostic and prognostic:** * Cardiovascular disease. * Pulmonary diseases. * Unexplained Dyspnea. * **Assessment of functional Exercise capacity.** * **Exercise prescription.** * **Evaluation of efficacy of the therapeutic intervention.** * **Measurable goals to improve fitness.** * **Development of knowledge and understanding of the disease.** ## Contraindication: | **Absolute**| **Relative**| | :-------- | :-------- | | * Acute myocardial infarction (3-5 days) | * Left main coronary stenosis or its equivalent | | * Unstable angina | * Moderate stenotic valvular heart disease | | * Uncontrolled arrhythmias causing symptoms or hemodynamic compromise | * Severe untreated arterial hypertension at rest (> 200 mm Hg systolic, > 120 mm Hg diastolic) | | * Syncope | * Tachyarrhythmias or bradyarrhythmias | | * Active endocarditis| * High-degree atrioventricular block | | * Acute myocarditis or pericarditis | * Hypertrophic cardiomyopathy | | * Symptomatic severe aortic stenosis | * Significant pulmonary hypertension | | * Uncontrolled heart failure | * Advanced or complicated pregnancy | | * Acute pulmonary embolus or pulmonary infarction | * Electrolyte abnormalities | | * Thrombosis of lower extremities | * Orthopedic impairment that compromises exercise performance | | * Suspected dissecting aneurysm | | | * Uncontrolled asthma | | | * Pulmonary edema | | | * Respiratory failure | | | * Acute non-cardiopulmonary disorder that may affect exercise performance or be aggravated by exercise (i.e. infection, renal failure, thyrotoxicosis) | | | * Mental impairment leading to inability to cooperate | | ## The exercise tests are as follow: * Exercise stress test (EST) * Cardiopulmonary exercise test (CPET) * Pharmacologic stress test * Nuclear stress test * Six-Minute Walk Test; 6MWT) * Incremental shuttle Walk test (ISWT) * Sit to stand test. * Functional exercise tests. ## Exercise stress test (EST) This test uses an ECG during exercise to evaluate blood flow to your heart. We perform an exercise stress test while you are exercising on a treadmill or stationary bicycle at a gradually increasing rate. We use this test to raise your heart rate so that we can detect heart problems affecting blood flow. We use this test to: * **Determine safe exercise levels after a heart attack or heart surgery.** * **Diagnose and determine the severity of CAD and other types of heart disease.** * **Diagnose an arrhythmia.** * **Find the cause of symptoms that appear only during exercise, such as shortness of breath, fainting, or irregular heartbeat.** * **Guide treatment planning, such as medication, cardiac catheterization (minimally invasive heart procedures), surgery, or transplantation.** ## Preparation of the test: * Wear comfortable shoes and loose clothing to allow you to exercise. * Ask the provider if you should take any of your regular medicines on the day of the test. Some medicines may interfere with test results. Never stop taking any medicine without first talking to your doctor. * You must not eat, smoke, or drink beverages containing caffeine or alcohol for 3 hours (or more) before the test. In most cases, you will be asked to avoid caffeine or caffeine-like substances for 24 hours before the test. This includes: * Tea and coffee * All sodas, even ones that are labeled caffeine-free * Chocolates * Certain pain relievers that contain caffeine ## Exercise Testing Protocols 1. **Maximal incremental cycle ergometer protocols (IET)** * **IET protocol** * Totally, 3 minutes of rest, then 3 minutes of unloaded pedaling then the incremental phase of exercise every minute (5 to 25 W/minute) until the patient reaches volitional exhaustion or the test is terminated by the medical monitor (increases in intensity over time) * **Ramp protocol** * Increase the work rate continuously, usually every 1 to 2 seconds in a Ramp like fashion * **Standardized exponential exercise protocol** * Work rate is increased exponentially by 15% of the previous workload every minute. 2. **Maximal incremental treadmill protocols** * **Bruce protocol:** * The starting point (ie, stage 1) is 1.7 mph at a 10% grade * Stage 2 is 2.5 mph at a 12% grade * Stage 3 is 3.4 mph at a 14% grade * This protocol includes 3-minute periods to allow achievement of a steady state before workload is increased. * **Modified Bruce protocol** * 2 warm up stages, each lasting 3 minutes. * The first is at 1.7 mph and a 0% grade, * The second is at 1.7 mph and a 5% grade 3. **Constant work rate protocol** * It is based on externally imposed and constant cycling or walking that the patient has to maintain until exhaustion. ## Evaluation of the exercise stress test: Parameters to assess | **PARAMETER** | **COMMENT** | | :-------- | :-------- | | General appearance | The presence of chest discomfort (pain) must be assessed repeatedly during the test. The severity of chest pain is graded from 0 (no pain) to 10 (maximal pain). | | Chest discomfort (pain) | | | Dyspnoea/dyspnea and exercise effort | | | Leg fatigue | Leg fatigue graded from 0 (none) to 10 (maximal. | | Maximal worldoad acheived and duration of the test | | | Heart rate | Maximal heart rate is noted during the entire procedure (including the recovery period). Heart rate acceleration is also noted. | | EKG/ECG reaction | | | Blood pressure reaction | Systolic blood pressure is measured every other minute. It is also measured at the termination of exercise and then every other minute during the recovery period. An automatic blood pressure monitor should not be used: measurements should be manual. | | Cause of termination | If the exercise test is terminated prematurely, the cause must be noted | ## Indications for termination of exercise testing * **Absolute indications for termination of testing include the following:** * Drop in systolic blood pressure (SBP) of more than 10 mm Hg from baseline, despite an increase in workload, when accompanied by other evidence of ischemia. * Moderate-to-severe angina. * Increasing nervous system symptoms (eg, ataxia, dizziness, near-syncope). * Signs of poor perfusion (cyanosis or pallor). * Technical difficulties in monitoring electrocardiographic (ECG) tracings or SBP. * Subject's desire to stop. * Sustained ventricular tachycardia. * ST elevation (> 1 mm) in leads without diagnostic Q waves (other than V1 or aVR). * **Relative indications for termination include the following:** * Drop in SBP of 10 mm Hg or more from baseline, despite an increase in workload, in the absence of other evidence of ischemia. * ST or QRS changes such as excessive ST depression (horizontal or down sloping ST-segment depression >2 mm) or marked axis shift. * Arrhythmias other than sustained ventricular tachycardia, including multifocal premature ventricular contractions (PVCs), triplets of PVCs, heart block, or Brady arrhythmias. * Fatigue, shortness of breath, wheezing, leg cramps, or claudication. * Development of bundle branch block or intraventricular conduction delay that cannot be distinguished from ventricular tachycardia. * Increasing chest pain. * Hypertensive response (SBP of 250 mm Hg, diastolic blood pressure [DBP] higher than 115 mm Hg, or both). ## Cardiopulmonary exercise test (CPET) * The cardiopulmonary exercise test (CPET) is an example of a maximal exercise test. Maximal tests are characterized by HRs greater than 85% of age-predicted values off medication or a rating of perceived exertion >15 (6-20 Borg scale; RPE). * **Maximal exercise testing allows for:** * **More precise exercise prescription than submaximal testing and greater reproducibility for follow up assessment.** * **Identification of cardiovascular compromise at higher levels of exercise and provision of an individualized maximum HR on which submaximal prescription can be based.** * **Gradation of exercise until the patient experiences signs/symptoms of cardiovascular compromise or reaches volitional exhaustion, or some other limiting symptom.** * **A CPET is similar to an exercise stress test, with the addition of ventilatory gas analysis to determine peak oxygen consumption (VO2 peak).** Oxygen consumption is determined by central (heart) and peripheral (muscle) factors that respectively influence the body's capacity to pump and utilize oxygenated blood. * **A CPET is commonly used to determine prognosis in patients with HF and to stratify patients for cardiac transplantation.** | | **Summary Data** | | | :--: | :---: | :--: | | **Measurement** | **Rest** | **Max exercise** | | Work (W) | 188 | 129 | | VO₂ (ml/minute) | 242 | 1,458 | | VO₂/kg (ml/kg/minute) | 3.0 | 17.8 | | Heart rate (bpm) | 81 | 153 | | O₂ pulse (mil O₂/beat) | 3 | 10 | | Blood pressure (mmHg) | 98/60 | 162/90 | | Ventilation (l/minute) | 84 | 65.9 | | Respiratory rate (bpm) | 31 | | | Tidal volume (l) | 0.88 | 2.11 | | O₂ saturation (%) | 100 | 100 | | PETCO₂ (mmHg) | 35 | | * **Predicted max** | **% Predicted** | | :--: | :--: | | 129 | 91 | | 1,620 | 90 | | 19.8 | 90 | | 169 | 91 | | 10 | 99 | | | 50% of MVV | | 116 | 57% of FEV₁ | | | | | | | | | | | | | * **Time point** | **pH** | **PaCO₂** | **PaO₂ (A-)10:** | **Lactate** | **VO₂/VT** | | :--: | :--: | :--: | :--: | :--: | :--: | | **Rest** | 7.42 | 39 | 100 | 9 | 0.8 | | **Max exercise** | 7.42 | 30 | 125 | 3 | 8.3 | ## Pharmacologic stress test * This stress test evaluates blood flow to your heart using an EKG but does not involve any physical activity. We recommend a pharmacologic stress test for people who are unable to exercise because of physical limitations such as arthritis, joint or back conditions, injury, or disability. In this test, you receive medication to stimulate your heart and cause it to beat harder and faster, as if you were exercising. * We use a pharmacologic stress test to: * Determine safe levels of physical activity if you have had a heart attack or heart surgery. * Diagnose many types of heart disease and determine their severity. * Guide decisions on treatment options, such as medication, cardiac catheterization (minimally invasive heart procedures), surgery, or transplantation. * Assess how well your treatment is working to increase blood flow to the heart. ## Nuclear stress test * This type of stress test includes radioactive dye and imaging studies to show blood flow to the heart, both at rest and when your heart rate is elevated. As with other types of stress tests, we record your heart's electrical activity with an EKG. * During a nuclear stress test, you receive an injection of radioactive dye through an intravenous (IV) line. The dye travels through your bloodstream and your heart. While you are still at rest, we scan your heart with a special camera that picks up the radioactive dye to show blood flow to and through your heart. * For the second part of the test, you begin exercising on a treadmill or stationary bicycle. If you are unable to exercise, we can give you medication to increase your heart rate. We then scan more images of your heart to capture blood flow to the heart during increased activity. ## Six-Minute Walk Test; 6MWT) * The six-minute walk test (6MWT), submaximal exercise test, is a self-paced walking test well suited to a hospital or community setting. * The test is undertaken using strict guidelines to ensure standardization. A 30-metre track is recommended where space is available and standardized instructions are given. * **Change in 6MWT distance can be measured in several ways.** The most common include: * **Absolute change (post-program distance minus pre-program distance)** * The minimum important distance (MID) is 25m in patients with coronary artery disease (CAD) and 36m for patients with chronic HF. * **Percentage change** * This may be a more relevant measure for frail patients whose baseline distance is very short (e.g., <100m), and can be calculated as follows: * % change = (post-program distance - pre-program distance) pre-program distance x 100 ## Incremental shuttle walk test (ISWT) * Another submaximal exercise test is the Incremental shuttle walk test (ISWT). Whilst this externally paced test is commonly used in pulmonary rehabilitation programs, it is not frequently used in cardiac rehabilitation. The ISWT may be beneficial for patients with few symptoms who may reach a ceiling effect in the 6MWT. * This incremental test is an externally paced test and involves walking between two markers 10 m apart. Auditory cues signal increased walking pace at each level (levels last 1 minute), until the patient reaches a predetermined criterion for test termination (85% max HR, Borg scale RPE = 15, failure to maintain walking pace on two consecutive lengths, development of symptoms). ## Sit to stand tests * The sit to stand test (STST) is easily performed, requires minimum time and equipment and closely resembles daily functional activities. As such, it is a valuable outcome measure in acute and subacute care settings. In recent years, it has also become popular for home-based and virtual cardiac and heart failure rehabilitation programs. * Several varieties of the STST are available, the most common of which are the 5 times sit to stand (5STST), the 30 second sit to stand (STST-30) and the 60 second sit to stand test (STST-60). Whilst the STST-60 has been shown to elicit similar physiological responses to the 6MWT, the 5STST is less demanding and thought to correlate more closely with lower limb strength. * **Test procedure** * The test commences with the patient sitting in a chair of standard height (46-48 cm), with arms crossed across the chest. * Upon command, the patient stands to a full standing position and returns to sitting. * For the 5STST, the time taken to complete 5 cycles of sitting to standing is recorded. * For the STST-30 and STST-60, the number of complete stands completed during the respective time period is recorded. * If the patient is unable to stand without using their arms for assistance, they are scored 0. * Only 1 test is required due to high levels of reliability.

Use Quizgecko on...
Browser
Browser