Guidelines for Clinical Exercise Testing Laboratories
A Statement for Healthcare Professionals From the Committee on Exercise and Cardiac Rehabilitation, American Heart Association
Exercise testing is a noninvasive procedure that provides diagnostic and prognostic information and evaluates an individual’s capacity for dynamic exercise. Exercise testing facilities range from the sophisticated research setting to more conventional equipment in the family practitioner’s or internist’s office. Regardless of the range of testing procedures performed in any given laboratory, basic equipment, personnel, and protocol criteria are necessary to conduct meaningful tests and ensure the comfort and safety of the patient.
This statement provides a guide to initiating and maintaining a high quality clinical laboratory for administering graded exercise tests to adults. Pediatric testing is addressed separately.1
Exercise testing equipment varies in size. The testing room should be large enough to accommodate all the equipment necessary, including emergency equipment and defibrillator, while maintaining walking areas and allowing adequate access to the patient in emergency situations. Compliance with local fire codes and with procedures for other types of emergencies (eg, earthquake, hurricane) is essential.
The laboratory should be well lighted, clean, and well ventilated with temperature and humidity control. Including posters or pictures of outdoor scenes can reduce boredom and anxiety, particularly if the room has no windows. A wall-mounted clock with a “sweep” second hand or a digital counter is useful. The examining table should have space for towels, tape, and other items needed for patient preparation and testing. A curtain for privacy during patient preparation is useful. Minimizing interruptions and maintaining privacy allows the patient and laboratory personnel to concentrate on the testing procedure.
To assess the level of effort, a large-print scale of perceived exertion2 (Table 1⇓) should be mounted on the wall in clear view of the patient. The same scale has been used to assess symptoms of fatigue, dyspnea, or leg fatigue/pain.3 Dyspnea can also be measured by means of a visual analog scale that is valid and reliable.4 In addition, a hand-held symptom scale is useful during cardiopulmonary testing when the mouthpiece or mask may prevent speech. This should be clearly explained to the patient.
A thermometer, barometer, and hygrometer should be kept in the room. Heart rate and perceived exertion rise with an increase in ambient temperature.5 6 Furthermore, cardiovascular responses become variable when humidity exceeds 60%. The combination of heat and humidity will lower maximum performance.7 In general, a temperature of 22°C (71.6°F) is considered comfortable for exercise. With short exercise periods, however, a temperature as high as 26°C (78.8°F) is acceptable as long as there is adequate air movement.8 A cool, dry environment (50% humidity) enhances cutaneous heat exchange or loss and serves to dissipate excessive heat provoked by exercise.7 Circulating fans can assist in controlling room temperature and ventilation. If gas exchange measurements are being performed, barometric pressure and temperature should be measured since gases expand with heat and/or low barometric pressures and contract with cold and/or high barometric pressures. Most modern automated cardiopulmonary testing systems will make adjustments for ambient conditions.
A suitable electrocardiographic (ECG) recording system is essential for continuous monitoring of heart rhythm and evaluation of ischemic ECG changes during exercise and recovery. Equipment ranges from more sophisticated and costly computerized systems to simpler, more conventional types. Nonetheless, the instrument should meet the specifications set by the American Heart Association.9 10
When purchasing a highly specialized computer system, care must be taken to ensure that the frequency response accurately reflects ST segment changes. It is necessary therefore to compare raw analog data with computer-generated data for validity. Continuous oscilloscopic monitoring of a minimum of three leads is recommended to optimally identify arrhythmia patterns. Furthermore, the ability to produce a 12-lead hard copy will enhance interpretation.11 The Mason-Likar adaptation of the 12-lead ECG has been commonly used in the clinical setting.12 ECG systems with built-in automatic arrhythmia sensing, which alerts the user to the occurrence of arrhythmias, are commercially available. Although not essential in every laboratory, these automatic arrhythmia detectors may be practical when the population being tested is at high risk.
Silver–silver chloride electrodes are recommended as the most dependable for minimizing motion artifact. Commercially available disposable electrodes vary in size and adhesive preparation. However, the importance of adequate skin preparation cannot be overlooked, regardless of the size or type of electrode used. Lightweight, shielded cables will lessen motion artifact. In addition, cable systems that arise from a central box can be worn around the waist and further stabilize the ECG signal. Flexible knit “tube” shirts for stabilizing the electrodes and cables are also available.
Blood Pressure Monitoring
Manual auscultation is still the most feasible method of monitoring blood pressure during exercise and the easiest to use.11 A variety of automated blood pressure units are available, but these devices are expensive and may perform erratically at high exercise intensities because of motion. In addition, diastolic blood pressure may not be accurate.13 If such systems are used, their reliability should be validated against manual cuff measurements within each respective laboratory before routine use, and distinctly abnormal hypertensive or hypotensive blood pressure recordings during exercise should be corroborated by manual recordings. A second staff member should check abnormally high or low blood pressure readings.
The laboratory should have cuffs of various sizes, including large and pediatric.13 The mercury manometer is recommended instead of the aneroid manometer because it is more accurate and easier to maintain and calibrate.13 The manometer should be placed at the level of the patient’s heart. Sphygmomanometers and cuffs, along with other testing equipment, should be cleaned and inspected on a regular schedule.
Treadmill. A treadmill should be electrically driven and should accommodate a variety of body weights up to at least 157.5 kg (350 lb). In addition, it should have a wide range of speeds, from a low of 1.6 km (1 mph) to a high of at least 12.8 km (8 mph). Elevation should be electronically controlled and should offer a variety of settings, from no elevation to 20% elevation. A dedicated 220-volt outlet may be required along with heavy electrical cables that meet electrical safety standards. The treadmill platform should be a minimum of 127 cm (50 in) in length and 40.64 cm (16 in) in width. Models are available with side platforms to allow the patient to adapt to the moving belt before fully stepping onto it. For patient safety and stability, padded front and side rails are recommended. An emergency stop button must be easily visible and readily accessible to the staff and the patient when needed.
Bicycle. Cycle ergometry is an alternative to treadmill testing for those patients who have orthopedic, peripheral vascular, or neurological limitations that restrict weight bearing. It can also serve as a less expensive, portable substitute for testing. Work intensity can be adjusted by variations in resistance and cycling rate. Work rate can be calculated in watts or kilopond-meters per min−1 (kpm/min).
Two types of stationary bicycles are used for testing: mechanically braked and electronically braked. Mechanically braked ergometers require that a specified cycling rate be maintained to keep the work rate constant. Electronically braked ergometers are more expensive and less portable but automatically adjust internal resistance to maintain specified work rates according to the cycling rate. Regardless of the type of stationary bicycle used, the ergometer must have the capability to adjust the work rate in increments either automatically or manually.
The cycle ergometer must include handle bars and a seat that adjusts for height. At the ideal seat height the knee should be slightly flexed at full extension. For safety purposes, adaptable pedal grips should be included. In addition, meters, dials, or digital displays should be appropriately sized and placed for easy reading.
Physiological responses to exercise on a cycle ergometer differ from those obtained on a treadmill.14 15 Moreover, maximum oxygen uptake is 5% to 20% lower than on the treadmill.3 Table 2⇓ lists the approximate oxygen cost in metabolic equivalents (METs) for cycle ergometry relative to weight.
Arm Ergometer. Arm exercise testing is a useful alternative for diagnostic testing of patients with lower extremity impairment caused by vascular, orthopedic, or neurological conditions. In addition, arm ergometry is helpful for performing occupational evaluation in patients whose work primarily involves the arms and upper body. Dynamic arm exercise involves a smaller muscle mass than does leg ergometry for a given workload. However, arm exercise often necessitates the use of other muscles in the chest, back, buttocks, and legs for body stabilization, depending on exercise position and intensity.16
Arm exercise testing can be performed with either mechanically braked or electronically braked arm ergometers. The former can be purchased separately as a specifically designed unit for graded arm cycling or can be adapted from standard bicycle ergometers by replacing the pedals with handles for cranking.17 18
Recommended protocols for arm ergometry testing require that the subject be seated in the upright position, with the fulcrum of the handle adjusted at shoulder height. The arm should be slightly bent at the elbow during farthest extension movements. Cycling speeds of 60 to 75 revolutions per minute must be maintained. Work rate increments of 10 W per 2-minute stage are suggested. Testing end points are similar to those of other types of ergometry. Vo2 requirements during arm cycle ergometry can be determined from formulas that take into account work rate, gender, and subject body weight19 and can be estimated easily using data in Tables 3 and 4. Other techniques used to test the upper body include rowing machines and air-braked arm/leg ergometers.20 21
Oxygen uptake during any equivalent submaximal level (eg, 50 W) of arm work exceeds that of leg work. Accordingly, the rates of increase of heart rate and blood pressure responses during arm ergometry are more rapid.19 Other physiological responses to dynamic arm exercise, eg, stroke volume and diastolic blood pressure, also differ from those of leg exercise.22 23 24
The sensitivity of arm exercise testing for detection of significant coronary artery disease is less than that of treadmill testing and is discussed elsewhere.25
Equipment for Ventilatory Gas Exchange Analysis
Recent technological advances have made it easier to perform gas exchange analysis during exercise testing, and this technology is being used with increasing frequency in the clinical setting. The use of gas exchange analysis techniques can greatly enhance both precision and reproducibility for assessing cardiopulmonary function compared with indirectly estimating oxygen uptake from work rate.26 27 Gas exchange analysis is essential for accurately quantifying the effects of medical interventions. For this reason, gas exchange analysis techniques are being used in an increasing number of clinical research trials. However, the additional accuracy and information provided by this technology is dependent on some basic skills required of both the technician, who must properly calibrate the system and perform the test, and the physician, who must interpret the results and communicate them to the patient. In addition, the equipment must meet certain specifications, and specific calibration procedures must be followed.
Equipment Calibration (see Appendix 4)
If ancillary imaging is to be performed in conjunction with the stress test, certain modifications should be considered. The use of a gamma camera for radionuclide images or a cardiac ultrasound machine for stress echocardiograms will require increased space to accommodate this equipment. Dedicated electrical outlets or a 220-V line may be necessary as well. Institutional radiation safety committee guidelines must be carefully followed.
If a large volume of stress echocardiograms are to be performed, a platform or bed with a “cut away” mattress for easier imaging can be helpful. A wide variety of systems are available for display of continuous loop rest and stress images in a side-by-side format. For laboratories performing pharmacologic stress tests such as those using dobutamine or dipyridamole, a precision intravenous delivery system (eg, IVAC) is also needed.
Staff members may include exercise physiologists, exercise specialists, physical therapists, ECG technicians, nurses, and physicians’ assistants. Appropriate training and performance skills for exercise testing personnel are available in published guidelines.3 All staff members must have received training in basic life support. Training in advanced cardiac life support is strongly encouraged.28
The degree of exercise testing supervision required is primarily dependent on the type of patients being tested. For patients who are at a higher risk (eg, unstable angina after stabilization, heart failure, or high-grade arrhythmia), a physician must directly monitor the test. In other cases, another properly trained healthcare professional (ie, nurse or exercise physiologist/specialist) can conduct the test and directly monitor patient status throughout testing and recovery. However, the supervising physician must be readily available.
The medical director of the exercise laboratory is responsible for the structure of the laboratory and its policies. The physician should also ensure that the laboratory is properly equipped and that the staff is appropriately qualified and trained.
The physician is responsible for interpreting the data, suggesting further evaluation or additional techniques for testing, if needed, and delivering appropriate emergency care when necessary.29 Requirements for physician competency in this area are clearly outlined in the American College of Physicians/American College of Cardiology/American Heart Association statement on clinical competence29 and include successful completion of an AHA-sponsored course in advanced cardiac life support.
Accurate and timely written interpretation of the exercise test results should be available, ideally in 72 hours or less. A preliminary test reading, however, should be available immediately. If the test results are highly abnormal, the referring physician should be notified as soon as possible.
Although exercise testing is relatively safe, the risk of testing varies with the patient population being tested.28 When testing a population of both men and women who for the most part have no coronary artery disease, a rate of 0.8 complications in 10 000 tests has been reported.30 In contrast, the rate of complications in a population with malignant ventricular arrhythmias can be as high as 23 in 10 000 tests.31 Others have reported 2 deaths in 24 complications encountered in 50 000 tests, for a mortality rate of 0.4 per 10 000.32 Since the majority of diagnostic laboratories perform exercise tests in a population with a higher prevalence of coronary disease, all testing facilities must have equipment, drugs, and personnel trained to deliver appropriate emergency care.
An exercise laboratory should have a written emergency plan appropriate to the individual facility. All personnel should know and review the planned procedures at least quarterly. The plan must allow for evacuation of unstable patients by a specified route for rapid transfer to hospital emergency facilities. AHA protocols for basic and advanced life support should be followed as appropriate.33
Equipment and Drugs
Table 5⇓ lists the minimum emergency equipment necessary in any testing laboratory. If intubation becomes necessary, suction equipment, laryngoscope with blades of various sizes, and intubation equipment should be readily available. If a more extensive equipment cart is located in an area other than the testing area, a specific plan for rapid accessibility to the cart should be clearly defined. A defibrillator should be in every exercise testing laboratory and should be tested on a daily basis.
To optimize the value of diagnostic testing, patient cooperation is essential. In most cases, an adequately informed patient will give a maximum of effort and thus provide the most information for an optimum interpretation. Therefore, careful patient preparation should precede all exercise testing.
In the current practice environment, a written request for exercise testing should be provided by the referring physician with a brief description of the diagnosis (confirmed or suspected), the reason for testing, and, if possible, a list of the patient’s medications. With regard to medications, dose and time taken should be recorded. To standardize the response to testing and minimize patient anxiety, both written instructions given before the test and verbal instructions at the time of the test are recommended. A detailed set of instructions should be provided to the patient when the testing appointment is made. The instructions should include abstinence from food and smoking for 3 hours before regular testing and 8 hours before a nuclear imaging study. Clothing should be comfortable and loose, and footwear should be sturdy and comfortable.
If the patient is receiving multiple medications, the instructions should include a request for a list of drugs and dosing to be brought to the testing center. Tests are usually performed even if patients are receiving drug therapy, but withdrawal of certain medications such as β blockers or calcium blockers34 should be considered if the physiological response may be altered and thus lessen diagnostic accuracy. The physician ordering the test should make the decision to taper or discontinue medications, because rebound effects can occur.
At the Time of Testing
A brief history and physical exam with a focus on the cardiovascular system should be conducted before testing to elicit any signs and symptoms of peripheral vascular disease, orthopedic, or neurological restrictions that may limit performance. Information about usual physical activity will aid the laboratory staff in selecting an appropriate testing protocol. A sample history and physical form is shown in Appendix 2. The patient’s questions must be thoroughly answered before the test. Informed consent may be obtained and witnessed by personnel who can accurately describe the tests and potential risks. The informed consent should be included in the exercise test record. Five informed consent samples are included as Appendix 1A27 and Appendixes 1B through 1E. These can be modified to fit the needs of a particular laboratory. Specific instructions should be given on how to perform the exercise test, with a brief demonstration of the test procedure.
To obtain the best interpretation of an ECG, the interface between the skin and the electrode must be optimal. Resistance should be reduced to 5000 Ω or less.3 To achieve this, the superficial layer of skin must be removed. The areas where electrodes will be applied should be shaved with a battery-operated trimming device, to decrease the incidence of abrasions, or with a standard razor. Alcohol-saturated gauze should be used to clean and remove oil from the skin. When the skin is dry, the electrode-placement areas should be marked with a felt-tipped pen and rubbed with fine sandpaper or commercially prepared abrasive tape to remove the superficial layer of skin. After electrode placement, the technician can lightly tap the electrode to assess adequacy of skin preparation. A flexible tubing “vest” may be necessary to reduce cable motion.
A standard 12-lead ECG should be recorded initially, followed by an exercise 12-lead ECG. Resting ECG, heart rate, and blood pressure should be taken in both supine and standing positions before testing. This is necessary to determine the presence of any ECG abnormalities that might contraindicate the test and to determine any changes that occur due to body position.
Changes in T waves with hyperventilation can be common. ST segment depression can also occur with hyperventilation but is less common.35 The decision to perform hyperventilation pretesting can be made by the physician supervising the test, based on the clinical evaluation of the patient. If gas exchange analysis is being performed, resting values should be recorded with the patient at rest for at least 2 minutes or until a stable baseline is achieved.
Exercise testing protocols can be chosen by the supervising physician or laboratory staff. It is recommended that protocols be selected and/or adapted based on the limitations of the individual. Ideally, the desired testing end point should be reached within 8 to 12 minutes of testing.28 Longer protocols do not yield additional diagnostic information and result in reduced values for exercise capacity.36
Measurements recorded during testing should include heart rate and blood pressure at rest and at each workload level, ECG recording each minute, arrhythmias, abnormal ECG responses, and patient symptoms. Furthermore, the patient’s appearance should not be overlooked: changes in skin color, alertness, coordination, and strength during exercise should be noted and recorded. End points for testing usually include symptoms such as chest pain, shortness of breath or fatigue, ECG changes, arrhythmias, and abnormal blood pressure responses. Specific definitions and interpretation of these observations are discussed in the AHA’s exercise standards.28 A sample data recording form is shown as Appendix 3. Recovery data are included since abnormalities that occur during exercise can persist after exercise. In addition, symptoms, ECG abnormalities, and arrhythmias can first appear after exercise has been completed.11 35 The patient should be carefully monitored until heart rate, blood pressure, and ECG have returned to near-baseline levels. Moreover, if the patient has experienced any discomfort, monitoring should continue until significant symptoms have resolved. If symptoms and/or abnormal signs persist beyond 15 minutes in recovery, the supervising physician should evaluate the patient and recommend further observation or treatment.
Report of Test Results
The written report should be completed in a timely fashion and should contain the information necessary to assist the physician in clinical decision-making. The demographic data, date of test, and protocol used should be clearly identifiable. The report should include the peak work rate achieved by the patient in METs or Vo2, peak heart rate and blood pressure, and any abnormal signs or symptoms that occurred during or after the test. The ECG data should consist of rest, abnormal exercise changes, and return to baseline. Occurrence of arrhythmias must be noted as well. If ischemia was demonstrated by ECG changes, the time and double product at which the changes initially occurred should be specified. If gas exchange measurements were made, peak oxygen uptake, ventilatory threshold (if achieved), and level of effort should be reported. Since the referring physician may not be familiar with normal standards, appropriate reference values for age and gender data should be provided. With modern ECG and gas exchange testing systems detailed summary reports can be issued, allowing the physician to add comments as needed. A summary impression of the findings must be included and should be made part of the patient’s permanent record. Any recommendations for further diagnostic testing can be included as well.
Exercise laboratories must have an active quality assurance plan that should address and enforce practice for emergency situations. The plan should also assess staff performance during emergencies. Other quality control issues include keeping laboratory records that indicate regular maintenance and nonscheduled repairs of testing equipment, calibration logs, defibrillator testing, and review of emergency medications and their expiration dates. Hospital-based laboratories will need to review quality control issues for Joint Accreditation of Hospital certification.
Example of Informed Consent for Exercise Testing27
To determine my cardiovascular response to exercise, I voluntarily agree to engage in an exercise test. The information obtained about my heart and circulation will be used to help my doctor understand more about any problems related to my heart and advise me about activities in which I may engage.
I have been told that before I undergo the test, I will be evaluated either by a physician or by another member of the healthcare team in an attempt to determine if I have a condition indicating that I should not engage in this test.
I am told that the test I will undergo will be performed on a _____ (description), with gradually increasing effort until symptoms such as fatigue, shortness of breath, or chest discomfort may appear, indicating to me or to my physician that I should stop. I have been told certain changes may occur during the test, including abnormal blood pressure, fainting, an abnormal ECG, disorders of heart beat (too rapid, too low, or ineffective), and, possibly, heart attack and death.
I have read the above and understand it, and my questions have been answered to my satisfaction. Patient _____ Date_____ Physician Supervising the Test _____Witness _____
Informed Consent for Exercise Tolerance Test
Your physician has asked that you undergo an exercise test to evaluate the functional capacity of your heart, lungs, and/or blood vessels. The information obtained will be important for your diagnostic and future healthcare management. The test will measure your tolerance of exercise until fatigue, breathlessness, chest discomfort, or other symptoms occur, which will stop the test. The electrocardiogram will be monitored by a physician, and precautions for your safety will be observed. Risks of the testing procedure are minimal and rare and include fainting, falling, irregularities of heart beat, and, very rarely, heart attack or death (less than l in 10 000 cases). Professional staff will be present during testing and emergency treatment will be available if it becomes necessary. You understand that in the event of physical injury resulting from this procedure, physician services will be provided without charge but not compensation or costs of any required hospitalization. _____
I have read and fully understand the above and voluntarily consent to perform this exercise test at the _____Hospital or center. Signed _____Witness _____Date _____
Informed Consent Form for Exercise Testing
To determine an appropriate plan of treatment to assist in my recovery from my heart illness, I hereby consent to voluntarily engage in an exercise test to determine the state of my heart and circulation. The information obtained will aid my physician in advising me about activities in which I may engage.
Before I undergo the test, I will have an interview with a physician. I will also be examined by a physician to determine if I have any condition that could indicate that I should not engage in this test.
The test that I will undergo will be performed on a treadmill or bicycle with the amount of effort increasing gradually. This increase in effort will continue until symptoms such as fatigue, shortness of breath, or chest discomfort may appear, which would indicate to me to stop.
During the performance of the test, a physician or trained observer will monitor my pulse, blood pressure, and electrocardiogram. Oxygen intake may also be measured and _____tests performed.
Certain changes may occur during the tests. These changes include abnormal blood pressure, fainting, disorders of heart beat (too rapid, too slow, or ineffective), and, in very rare instances, heart attack. Every effort will be made to minimize such changes through the preliminary examination and observations during testing. Emergency equipment and trained personnel will be available to deal with unusual situations that may arise.
The information obtained will be treated as privileged and confidential and will not be released or revealed to any person without my expressed written consent. The information obtained, however, may be used for a statistical or scientific purpose with my right of privacy retained. _____
I have read the foregoing and I understand it, and any questions that may have occurred to me have been answered to my satisfaction. _____Signed: _____Date Patient _____ _____ Physician supervising test Witness
Emory Health Enhancement Program Informed Consent for Exercise Testing and Training
To determine my cardiovascular status and state of physical condition, I hereby consent to perform an exercise test.
Based on the results of this exercise test and evaluation, I will be given a prescription for an exercise program. It is my decision to select either a supervised group exercise program, to exercise on my own, or not to exercise. In any event, I do not hold Emory University, the George W. Woodruff Physical Education Center, or the Emory Health Enhancement Program responsible for any cardiovascular event and/or other accidents connected with either testing or training.
This consent remains valid as long as I remain in the supervised exercise program at the Emory Health Enhancement Program and includes all exercise tests and other evaluations. The Emory Health Enhancement Program, the George W. Woodruff Physical Education Center, and Emory University are not responsible for any cardiovascular event and/or other accidents occurring apart from the supervised exercise programs and/or testing. Signed _____ _____ _____ Date _____ _____ _____
I give my informed consent to the following procedure: Treadmill Exercise Test which consists of a progressive increase in exercise that begins with walking and may progress to a fast walk and jogging. The test will be conducted by trained personnel who will carefully monitor my performance, blood pressure, and heart rhythm. All efforts will be made to safeguard my safety and comfort.*
Potential risks are associated with exercise testing. These include dizziness, fainting, orthopedic problems, chest discomfort, disorders of heart rhythm, heart attack, and death.
I understand these risks, though rare, can occur and I voluntarily accept the risks associated with the procedure. In addition, I understand that I may ask that the test be discontinued at any time.
*A cardiologist is available at all times should a problem arise. Date _____Patient _____ Witness _____
Sample Pretest Data Summary
Name _____ Study Date _____MR No. _____ Referring MD _____Test indication: Follow-up _____ Pre-op _____Chest pain Yes/no
Typical/atypical; New/changing pattern/chronic;
Exertional/rest/nocturnal Comments: _____Past medical history Myocardial infarction: Yes/no; date: _____; region: _____; complicated by: _____ Coronary artery bypass graft: Yes/no; date: _____; number of vessels _____ Other cardiac disease: CHF/valvular _____ arrhythmias _____ Percutaneous transluminal coronary angioplasty: Yes/no;
date: _____; vessels: _____Other: _____Risk factors: Smoking/family history/hypertension/obesity/
high cholesterol/insulin-dependent diabetes mellitus or
non–insulin-dependent diabetes mellitus/
peripheral vascular disease Prior workup Cardiac catheterization: Yes/no; Date: _____; Results: _____Endotracheal tube: Yes/no; Date: _____; Results: _____Nuclear tracer study: Yes/no; Date: _____; Results:_____
β-blocker: Yes/no; last taken: _____
Ca2+-blocker: Yes/no; last taken: _____
Digoxin: Yes/no; last taken: _____
Theophylline Dipyridamole: Yes/no; last taken: _____
Converting enzyme inhibitors: Yes/no; last taken: _____Physical exam: Heart: murmur, S3, S4 Pretest _____ posttest _____ Lungs: clear _____ crackles _____ wheezes _____ Peripheral pulses __________Precordial dyskinetic areas by palpation: _____Resting ECG _____ _____ _____Comments: _____ _____ _____
Type of test: Maximal Submaximal Dipyridamole Canceled Treadmill: Protocol _____Cycle: _____ kpm/min or W per stage Arm: _____ Leg: _____
Symptoms: C indicates chest pain; S, dyspnea; D, dizzy; PVD, peripheral vascular disease; CP, calf pain; F, flushing; H, headache; M, musculoskeletal pain; 0, no symptoms Exercise time: _____ minutes Highest stage (no.): _____ Time: _____Peak Vo2: _____ METs _____Ventilatory threshold: _____ ST depression: Yes No
Time turned positive: _____ min.
Heart rate at ischemic threshold: _____
ST depression: H indicates horizontal; D, downsloping;
Type _____ lead(s) _____ amount (mm) _____
ST elevation: Lead(s) _____ amount (mm) _____
ST depression ≥5 leads? Yes _____ No _____
ST depression persisted ≥5 min in recovery? Yes _____ No _____
_____ mg aminophylline given (dipyridamole test)
Adenosine dose reduced? Yes _____ No _____
Treadmill and Cycle Ergometer Calibration
Calibration of the treadmill and cycle ergometer (both leg and arm) should be performed on a monthly basis, or more frequently if a large number of tests are performed.3 Specific directions for calibration and preventive maintenance are included in the treadmill or ergometer operation manual provided by the manufacturer. Each laboratory should record dates that calibrations are performed. These records are an important part of quality assurance procedures.
Calibration of treadmill speed requires knowledge of the belt length, which can be obtained from the manufacturer or measured with a tape. The treadmill speed can be calibrated by counting the number of rotations of the treadmill belt per unit of time. Using a mark on the treadmill belt as a reference, the number of belt revolutions in 1 minute can be counted, and, knowing the length of the belt, the actual miles per hour calculated by:
(1056 = conversion of inches per minute to miles per hour)
The value obtained is the treadmill speed in miles per hour. If the speed indicator does not agree with this value, adjust the meter to the proper setting. Frequently a calibration adjustment screw is found in a small opening in the front of the control panel. If not available, the manufacturer should be contacted. The calibration procedure should be repeated for several different speeds to ascertain accuracy across commonly used protocols in a given laboratory.
Treadmill elevation is calibrated by measuring a fixed distance on the floor and determining the difference in height of the treadmill over the fixed distance. The following specific procedures are performed:
1. With the use of a carpenter’s level, ensure that the treadmill is resting on a level surface. Set the treadmill elevation to 0% grade. If the elevation does not read 0% when it is level, adjust the potentiometer until it does.
2. Mark 2 points 50 cm (20 in) apart along the length of the treadmill.
3. Elevate the treadmill to its metered reading of 20% grade and measure the distance of each of the 2 points to the floor.
4. Divide the difference between the two heights by 20. The results should be .20 or 20% when the elevation is properly calibrated. If the result is not 20%, adjust the elevation meter potentiometer so that it displays the calculated elevation percentage. A check of 5%, 10%, and 15% grade readings is recommended to ensure the validity of intermediate positions.
Speed and elevation should be calibrated without a subject on the treadmill. It is recommended, however, that after calibration a moderately heavy subject (75 to 100 kg) walk on the treadmill to ensure that the calibrations remain accurate when in use. Speed should remain unchanged regardless of the weight of the individual on the treadmill.
After approximately 1000 hours of use, the treadmill should be serviced, which should include lubricating the motor bearings, checking the variable speed belt for wear, centering the belt, greasing the chain drive, and cleaning and lubricating the gears. Service and maintenance schedules should be available from the manufacturer.
Bicycle Ergometer Calibration
Since the work rate on a mechanically braked ergometer depends not only on the resistance but also on the cycling rate in revolutions per minute, it is essential that a counter quantify this factor. It is also important that the belt tension be adjusted appropriately and that the flywheel be cleaned to ensure smooth operation. Electronically braked ergometers are more difficult to calibrate and require special instruments generally not available to the individual purchaser, so calibration is usually provided by the manufacturer or by the institutional biomedical engineering department.
To check the calibration on a mechanically braked cycle ergometer, the belt should be removed from the wheel. The mark on the pendulum weight should be set at “0,” and a weight that is known to be accurate should be attached to the belt. The weight should hang freely. A reading of that weight should be given accurately on the scale. If all conditions are met and the scale continues to show an incorrect reading for the known weight, the adjusting screw should be turned until the scale reads the appropriate weight.
When calibrating an ergometer that is braked by a lateral friction device, the ergometer is placed on two chairs so that the brake scale plate is vertical. After releasing the brake regulator knob on the handlebar, a known metric weight is hung on the brake arm using a wire S-hook. After loosening the fastening screw of the shock absorber at one end, the scale should read, in kiloponds, the exact amount of the weight attached to the brake arm. The pointer should always be read from directly above. If the scale does not accurately read the weight, the regulating nut should be turned. When the pointer indicates the same figure as the weight attached, the ergometer is correctly calibrated.
Mechanically braked ergometers can be delicate and may lose adjustment from frequent use or if they are transported. Before using an ergometer, the chain should be checked for tightness and lubrication, and the braking surfaces of the flywheel should be free of any dirt that has gathered. A fine sandpaper pressed against the braking surface while pedaling the ergometer will smooth the surface.
Mechanically braked arm ergometers should be manually calibrated routinely as recommended for bicycle ergometers. Electronically braked models require periodic calibration by experienced biomedical technicians as recommended by the specific equipment manufacturer.
Gas Exchange Systems
The metabolic system should be calibrated just before and immediately after each test. This should include calibration of airflow and both the oxygen (O2) and carbon dioxide (CO2) analyzers. Gas analyzers and flow meters are prone to drift, which can lead to serious errors. Today, nearly all commercially available systems have convenient calibration procedures controlled by a microprocessor. Validation studies have been performed on a number of the computerized systems.37 38 Because ambient conditions affect the concentration of O2 in the inspired air, it is necessary to have a thermometer, barometer, and hygrometer in the room. A copy of the calibration report should be printed before and after each test and should be attached to the test report. Valid interpretation of test results is possible only if calibration values are appropriate.
Gas exchange measurements are highly reproducible within a given subject if testing methods are consistent. One method often used for validating a system’s performance is to test laboratory staff members at a matched submaximal workload on a periodic basis. It is recommended that several staff members participate in this process, each using a slightly different steady-state submaximal workload. Jones39 has outlined the limits of variation in oxygen uptake and hemodynamic data for a given steady-state work rate (Table 7⇑). In addition to being reproducible, the data should approximate the predicted oxygen cost of a given steady-state work load (±10%).3 The following specific calibration procedures should be performed to ensure that valid data are obtained:
1. Room air should read 20.93±0.03% O2 at 0% humidity. However, the precise fraction is dependent on humidity and should be adjusted accordingly. A calibration source containing 100% nitrogen should read 0% O2. The analyzer should be checked further by simulating the fraction of expired O2 (Feo2) during the test, ie, approximately 16% O2. The exercise laboratory should be well-ventilated to assure a representative fraction of inspired O2; a fan is helpful for this purpose.
2. The CO2 analyzer should read a room air fraction of 0.03±0.02% and should not change when the 100% N2 or 16% O2 fractions are sampled from the calibration tanks. The CO2 analyzer should be checked further by simulating the fraction of expired CO2 (FeCO2) during exercise, ie, approximately 4% CO2.
3. For both the O2 and CO2 analyzers, it is also preferable to check the analyzer response time or “delay.” It is important that the system meets the specifications outlined by the manufacturers; this feature is available in most systems.
4. Once limited to large weather balloons and tissots, great strides have been made in the measurement of ventilatory volume, and numerous flow devices are now available, including small turbines, propellers, and even disposable pneumotachometers. All can be validated before testing by ascertaining a stable baseline (0 L/min) and injecting a known volume (usually 3 or 4 L) from a syringe. It is preferable to perform several injections at different flow rates to ensure stability; the average error should be within ±3% of the known volume.
“Guidelines for Clinical Exercise Testing Laboratories” was approved by the SAC/Steering Committee of the American Heart Association on June 16, 1994.
Requests for reprints should be sent to the Office of Scientific Affairs, American Heart Association, 7272 Greenville Avenue, Dallas, TX 75231-4596.
- Copyright © 1995 by American Heart Association
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