[Methodologic and exercise-physiologic principles of ergometry: value of noninvasive parameters in the detection of compromised exercise capacity due to heart disease (author's transl)]

1. Ergometric studies enable comparable and reproducible determinations of the cardio-pulmonary-corporeal performance. Prerequisite, however, is a well-based knowledge of the methodology and exercise-physiologic principles of ergometry. 2. With respect to the methodologic prerequisites, consideration must be given to the length of shaft displacement and the inertial mass of the ergometer. Additionally, at submaximal workloads, standardized performance at 50 revolutions/min must be ensured. This also holds true for r.p.m.-independent ergometers since the biologic capacity varies at differing r.p.m. values. Furthermore, the results of ergometric examinations are comparable only on standardization of workload and duration (for example, 10 watts/1 min, 25 watts/2 min). Consideration should also be given to ancillary determinants of exercise capacity such as environmental factors, previous physical exertion, nutrition, medications and other self-administered drugs or stimulants as well as the clothing worn at the time of examination. 3. Based on the limited equipment necessary and the good reproducibility, the physical working capacity 170 (the capacity in watts at a heart rate of 170 beats/6 min) is well-suited for assessment of cardio-pulmonary-corporeal performance. The results do not differ significantly at workloads of 25 watts/min or 50 watts/6 min. The decreasing maximal heart rate with increasing age (on the average 10 beats/min per decade; in the individual case, substantially more) may result in a marked misestimation in elderly subjects. This also applies to patients with coronary artery disease in whom, for example, a slow heart rate during ergometry is caused by ischemia and only mimics an economic circulatory function. Evaluation of the systolic and diastolic blood pressure during ergometry is, to some degree, indicative of the pump function in patients with coronary artery disease. Measurement of oxygen uptake alone at submaximal workloads does not permit differentiation between healthy and diseased subjects since the latter compensate for a reduced cardiac output by a more marked oxygen extraction with subsequently greater arterio-venous oxygen differences. On calculation of the oxygen uptake per stroke, however, in relation to the heart volume, a clinically relevant differentiation between healthy subjects and diseased patients can be established. Thus, in patients with heart disease, noninvasive parameters also enable assessment of the cardio-pulmonary-corporeal performance. 4. Under physiological conditions, there is a close relationship between invasively and noninvasively-measured parameters during ergometry. In patients with heart disease, however, the response of noninvasively-measured parameters is not a reliable indicator of pressure in the pulmonary circulation and the cardiac output.