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Perhaps the most important differences we find between labs testing "patients" vs. labs testing so-called "normal" subjects is the use of the 12-lead ECG and the availability of resuscitation equipment and personnel trained in it's use.
2. Equipment for the Cardiac Stress TestThe equipment required is usually obvious and well understood, but you should be aware that there is a big price differential between Resting ECG and Stress Testing ECG. In evaluating competing systems, be sure you understand software options, such as "Full Disclosure", "Automatic Arrhythmia Detection", "ST Segment Analysis" and others, which may affect the cost of the system.
Minimum requirements are a 12-lead system with STRESS TEST software.
Other equipment required:
Blood pressure sphygmomanometer (e.g. Baumanometer) or
Emergency Resuscitation Equipment
3. Equipment for the Pulmonary Stress Test LabThe instrumentation here can vary greatly depending on the type of testing to be performed, the reason for the test, the mission of the laboratory and the desired accuracy. For example, a college teaching laboratory might be more interested in a basic low cost system, while a lab planning to publish their findings would be more interested in accuracy. Listed in approximate order of importance
4. The VO2 System: What to look forAll CPX's (VO2 Measurement Systems) contain the same basic building blocks:
Oxygen and CO2 analyzers, a ventilation measurement device, interfacing electronics, gas sampling system, data acquisition system and some kind of computer and software.
Most CPX manufacturers do not make their own gas analyzers, instead they buy them from companies that specialize in making nothing but gas analysis equipment. This is actually good news, because better quality can often be achieved by specialization.
The other major component is the ventilation measurement device or flow sensor. The chart below may help you select a desirable flow sensor.
Almost all companies use a PC now, so very little differentiation can be expected there.
The final and perhaps most important component is the software. It is the software that ultimately determines the accuracy of the VO2 measurement. You may have the world's best gas analyzers, but if the software does not correctly align gas data with flow data, or if the compensation for barometric pressure, temperature and humidity is not handled correctly, then the system cannot report accurate VO2's.
To our knowledge only a Metabolic Simulator(1,2) can accurately verify if the system operates correctly.
Here are some other questions you may want to ask before you buy:
5. Exercise DevicesThere are a lot of exercise devices on the market and this listing is not intended to be complete.
VacuMed's models 13610 and 13620 meet this description and also include a "Kill Switch" that automatically shuts of the treadmill if the runner gets too far away from the control console. Model 13610 is a heavy duty research type treadmill. Most manufacturers of exercise stress testing devices offer treadmills with their own name on them but manufactured by other companies specializing in treadmill manufacturing.
In our opinion, for CPX testing you should not consider an ergometer costing less than $2000. Ergometers are stationary bicycles that have some kind of braking mechanism that can be calibrated in Watts, Joules or KPM. Braking mechanisms using belts, brake pads tend to be less accurate. Modern braking mechanisms use electro-magnetic brakes (eddy current). For more advise on selecting ergometers, go back to Dr Andrew's Corner.
Rowing Machines and Stairclimber are sports-specific and are almost never used in a clinical setting.
6. Accessories & SuppliesTypical cardiac supplies:
7. Laboratory Setup
Make sure large equipment, such as treadmills and underwater weighing tanks will fit through doors, hallways or windows.
8. Test Precautions
Consult the publications listed on the next page.
9. What are the reasons for Exercise (CPX) Stress Testing
9.1 Exercise PhysiologyExercise requires the integration of physiological mechanisms to enable both, the respiratory and cardiovascular systems to support the increased metabolic demands.
During exercise, both ventilatory and cardiovascular systems are under stress. The ability to respond adequately to this stress is a measure of physiological health and fitness.
Exercise testing evaluates the respiratory and cardiovascular responses to increased gradual workloads in order to define the level of physical work capacity, and to determine the limiting factors to the increased metabolic demands of exercise.
Serial exercise studies help define the effects of treatment or fitness programs on the physiological response to physical work.
Here are some examples of exercise related study subjects:
9.2 Studies of MetabolismThis involves the measurement of VO2 and VCO2 at rest for the determination of :
See also Dr. Andrew's Corner
9.3 Occupational ApplicationsExercise Stress (CPX) Testing is frequently used in professions that require high physical demands, such as
Rescue & Disaster Response Teams
Steel Mill Workers
CPX testing in such professions may be used for:
9.4 Clinical Applications
RESPONSE TO EXERCISE IN CARDIAC OR PULMONARY DISEASE (5)*
3. Exercise-induced asthma
10. What is measured during a CPX test?
1. Oxygen Uptake ResponseVO2max: This is the gold standard to measure functional capacity of the cardiovascular system to transport oxygen.
VO2max depends on the mode of exercise, the degree of training and the integrity of cardiovascular function.
It is usually reduced in any sort of cardiopulmonary disease. In most cases, except in athletes, the presence of a normal or elevated VO2max virtually ensures the absence of any major cardiovascular or pulmonary diseases.
VO2max is expressed in ml/kg of body weight and relates to exercise tolerance.
2. Haemodynamic ResponsesThe behavior of heart rate, systolic and diastolic pressures and cardiac output, during exercise provides insight into cardiovascular response.
3. Ventilatory ResponsesChanges in Minute ventilation (VE), Tidal Volume (TV) and breathing frequency (f) reflect the magnitude of ventilatory response to exercise. The pattern of increase in tidal volume and breathing frequency may provide information about certain pulmonary and circulatory disorders.
4. Metabolic ResponseThis usually involves the measurement of VO2 and VCO2 at rest. Metabolism is affected be diet, exercise, disease, climate variations, etc.
5. Electrocardiographic ResponseThis represents the main focus of conventional ECG Stress testing. It is useful in defining the presence or absence of exercise induced ischemias as well as the presence or absence of dysrhythmias.
Clinical exercise testing requires monitoring of ECG and prompt termination of exercise testing is mandatory when a patient develops signs of distress, such as changes of PQRST pattern.
11. Other Publication
1. GUIDELINES FOR EXERCISE TESTING (4) A Report of the American College of Cardiology/American Heart Association Task Force on Assessment of cardiovascular Procedures (Subcommittee on Exercise Testing) Reprints: Mr. David J Feild, Assistant Executive Vice President, American College of Cardiology, 9111 Old Georgetown Road, Bethesda MD 20814
2. Books PRINCIPLES OF EXERCISE TESTING AND INTERPRETATION By Karlman Wasserman, MD, PhD., James E Hanson, MD., Darryl Y Sue, MD., Brian J Whipp, PhD., Richard Casaburi MD, UCLA Medical Center, 274 pp, illus., 1994, 2nd ed.
3. Books RESOURCE MANUAL FOR GUIDELINES FOR EXERCISE TESTING AND PRESCRIPTION Edited by the AMERICAN COLLEGE OF SPORTS MEDICINE, Indianapolis, IN. (64 Contributors) 580 pp, 205 illus., 1993
4. Books GUIDELINES FOR EXERCISE TESTING AND PRESCRIPTION, 4th ed. Edited by the AMERICAN COLLEGE OF SPORTS MEDICINE, Indianapolis, IN. 314 pp, paperback, 1991
5. Books EXERCISE PHYSIOLOGY LABORATORY MANUAL Basic principles of field and laboratory testing, includes forms for data collection and typical calculations. By Gene M Adams, California State University-Fullerton 304 pp, illus, wirecoil, 1993, 2nd ed.
6. Books EXERCISE PHYSIOLOGY Energy, Nutrition, And Human Performance William D McArdle PhD, Frank I Katch EdD and Victor L Katch EdD 853 pp, illustrations, 1991, Third Edition
7. Books EXERCISE IN HEALTH & DISEASE Evaluation & Prescription for Prevention and Rehabilitation, 2nd ed. By Michael L Pollock & Jack H Willmore, 754 pg, 367 illus, 1990
8. Books PRINCIPLES AND PRACTICE OF PULMONARY REHABILITATION Up-to-date info about diagnostic techniques & rehabilitation By Richard Casaburi MD PhD & Thomas L Petty MD. 510 pp, 190 illus, 1993
(1) Huszczuk, A., B.J. Whipp, and K.Wasserman. A respiratory gas exchange simulator for routine calibration in metabolic studies. Eur. Respir. J. 3:465-468, 1990
(2) Gore, C.J., P.G. Catcheside, S.N. French, J.M. Bennett, and J. Laforgia. Automated VO2 max calibrator for open-circuit indirect calorimetry systems. Med. Sci. Sports Exerc 29:1095-1103, 1997
(3) Wilmore, J.A., P.A. Vodak, R.B. Parr, R.N. Girandola an J.E. Billing. Further simplification of a method for determination of residual lung volume. Medicine and Science in Sports and Exercise Vol. 12, No. 3.
(4) SPECIAL REPORT: Guidelines for Exercise Testing. JACC Vol. 8, No. 3. Sept 1986:725-38
(5) ACCP, San Francisco1991, A Pulmonary Approach to Exercise Testing, Idelle M. Weisman, FCCP, El Paso, TX