Karlman Wasserman

Detecting the threshold of anaerobic metabolism in cardiac patients during exercise

Abstract The measurement of the respiratory gas exchange ratio (R) during a standard exercise test is used to detect the onset of anaerobic metabolism during exercise, which results from failure of the cardiovascular system to supply the oxygen requirements of the tissues. The method described uses end-tidal gas concentrations to calculate R while the exercise test is taking place. Blood sampling is unnecessary, and the results can be determined during the test, thus avoiding exhaustive exercise. The method provides an objective measurement of one of the factors influencing exercise tolerance.

Lung Function and Exercise Gas Exchange in Chronic Heart Failure

BACKGROUND The ventilatory response to exercise in patients with chronic heart failure (HF) is greater than normal for a given metabolic rate. The objective of the present study was to determine the mechanism(s) for the high ventilatory output in patients with chronic HF. METHODS AND RESULTS Centers in Germany, Italy, Japan, and the United States participated in this study. Each center contributed studies on patients and normal subjects of similar age and sex. One hundred thirty patients with chronic HF and 52 healthy subjects participated. Spirometric and breath-by-breath gas exchange measurements were made during rest and increasing cycle exercise. Arterial blood was sampled for measurement of pH, PaCO2, PaO2, and lactate during exercise in 85 patients. Resting forced expiratory volume in 1 second (FEV1) and vital capacity (VC) were proportionately reduced at all levels of impairment. Patients with more severe HF had greater tachypnea and a smaller tidal volume (VT) at a given exercise expired volume per unit time (VE). This was associated with an expiratory flow pattern characteristic of lung restriction. VE and VCO2 as a function of VO2 were increased during exercise in HF patients. The increases were greater the lower the peak VO2 per kilogram of body weight. The ratio of VD (physiological dead space) to VT and the difference between arterial and end tidal PCO2 at peak VO2 also increased inversely with peak VO2/kg. In contrast, the difference between alveolar and arterial PO2 and PaCO2 were both normal, on average, at peak VO2 regardless of the level of impairment. The more severe the exercise limitation, the higher the lactate and the lower the HCO3- at a given VO2, although pH was tightly regulated. CONCLUSIONS The increase in VE in chronic HF patients is caused by an increase in VD/VT due to high ventilation/perfusion mismatching, an increase in VCO2 relative to VO2 resulting from HCO3- buffering of lactic acid, and a decrease in PaCO2 due to tight regulation of arterial pH. With regard to the excessive VE in HF patients, the increases in VD/VT and VCO2 relative to VO2 are more important as the patient becomes more exercise limited. Regional hypoperfusion but not hypoventilation typifies lung gas exchange in HF. This and other mechanisms might account for the restrictive changes leading to exercise tachypnea in HF patients.

Effect of Bilateral Carotid-Body Resection on Ventilatory Control at Rest and during Exercise in Man

Abstract To investigate the role of the carotid bodies in the control of ventilation during rest and moderate exercise, seven asthmatic subjects who had undergone bilateral carotid-body resection (the barostatic reflexes remained intact) were studied while they were breathing air and hypoxic, hypercapnic, and hyperoxic gas. During breathing of air and 25 per cent oxygen, ventilation was not different between this group and control subjects either at rest or during exercise. The hyperpnea of hypoxia was absent, and the ventilatory response to increased arterial carbon dioxide tension was reduced 30 per cent after carotid-body resection. These studies indicate that ventilation with the subject breathing air during rest and steady-state exercise is not affected by the operation, the carotid bodies appear to be responsible for the hyperpnea of hypoxia, and this response is not enhanced by moderate exercise, and the ventilatory response to increased arterial carbon dioxide tension is reduced after bilateral ca...

Relation of oxygen uptake to work rate in normal men and men with circulatory disorders

The relation between the increase in oxygen uptake (VO2) and increase in work rate (WR) between unloaded pedaling and maximal work during incremental cycle ergometer exercise was studied in normal men, men with uncomplicated systemic hypertension and ambulatory men with various cardiovascular diseases. The postulation was that impaired peripheral oxygen delivery would reduce the ratio of the oxygen utilized relative to work performed. The ratio of increase in VO2 to increase in WR (delta VO2/delta WR) was relatively constant: 10.29 +/- 1.01 ml/min/W in normal men (n = 54) for exercise 6 to 14 minutes in duration with uniform work increments of 15, 20, 25 or 30 W/min, regardless of age. The value in men with uncomplicated systemic hypertension (n = 24) was not significantly different from that of normal men. However, more than half of the men with peripheral vascular disease (n = 7) or pulmonary vascular disease (n = 5) or men who had electrocardiographic abnormalities during exercise (n = 39) had a significantly lower delta VO2/delta WR, 8.29 +/- 1.17 ml/min/W (p less than 0.05) especially evident as maximal work rates were approached. Thus, delta VO2/delta WR during incremental exercise testing is predictable for normal men and a reduction in this ratio indicates cardiovascular dysfunction.

Effect of ramp slope on determination of aerobic parameters from the ramp exercise test

The effect of ramp slope on determination of aerobic parameters from the ramp exercise test. Med. Sci. Sports Exercise, Vol. 14, No. 5, pp. 339-343, 1982. We have previously demonstrated that the four parameters of aerobic function (maximal oxygen uptake (muVO2), VO2 at the anaerobic threshold (theta an), the time constant for VO2 kinetics (tau VO2), and work efficiency (eta)) may all be determined reliably from a single test in which the work rate increases continuously at a constant rate, i.e., ramp. That study, however, utilized a single ramp slope of 50 W X min-1, which may not be appropriate for subjects with very low or very high work tolerances. We therefore studied the effect of different ramp slopes on the determination of these parameters. Ramp slopes of 20, 30, 50, and 100 W X min-1 were generated on a cycle ergometer, and each was assigned randomly to 14 healthy subjects. Ventilatory and gas exchange variables were measured breath-by-breath utilizing on-line digital computation. Ramp slopes of 20, 30, and 50 W X min-1 yielded the same values for each aerobic parameter. The 100 W X min-1 ramp yielded muVO2 and eta an values that were the same as those found for the other ramp slopes, but tau VO2 and eta could not be discerned validly from this ramp slope. We conclude that valid assessment of the four parameters of aerobic function is possible with ramp slopes between 20 and 50 W X min-1; no further information on the parameters is to be gained by prolonging the tests with ramps slower than 20 W X min-1.

Oxygen uptake as related to work rate increment during cycle ergometer exercise

SummaryWe postulated that the commonly observed constant linear relationship between

Effect of exercise testing protocol on parameters of aerobic function

\dot V_{{\text{O}}_{\text{2}} }

Mechanisms and patterns of blood lactate increase during exercise in man.

and work rate during cycle ergometry to exhaustion is fortuitous and not due to an unchanging cost of external work. Therefore we measured