Cardiopulmonary Responses to Maximal Exercise and Submaximal Steady-state Exercise in Patients with Chronic Obstructive Pulmonary Diseases

The purpose of this study was to compare the exercise responses in normal subjects and subjects with chronic obstructive pulmonary diseases (COPD). Eleven stable COPD patients from outpatient department and 9 persons with no known cardiopulmonary diseases served as the subjects of the study. Cardiopulmonary responses to maximal workload during an incremental exercise test and submaximal steady-state exercises of three intensities, 50%, 60%, and 70% VO2max respectively, were studied. No differences in resting or preexercise data between the groups were found. Subjects with COPD attained comparable breathing frequency (Fb), heart rate (HR), oxygen pulse, ventilatory equivalent for O2 and CO2 (VE/V02, VE/VCO2), and O2 pulse with the normal controls, but significantly lower workload (WL), oxygen consumption (V02), minute ventilation (VE), tidal volume (Vt), and respiratory exchange ratio (RER) at maximal exercise. Five-minute postexercise lactate level was also significantly lower in patient group. The absolute values of all these parameters required for 50%, 60%, and 70% VO2max in COPD patients were not significantly different from the values in normal subjects. However, VE as a percentage of achieved maximal values was significantly higher in these three exercise intensities in COPD patients. Minute ventilation for intensities of 50%, 60%, and 70% VO2max were found to be 51.1±5.9%, 62.2±10.6%, and 70.3±9.0% of the patients' maximal VE.