Abstract
Continuous multistage treadmill exercise tests were performed in 35 COPD patients to evaluate anaerobic threshold (A.T.) Minute ventilation (VE), VO2, VCO2, arterial blood gases and pH in addition to blood lactate were measured at each work load.
Twenty-four patients were considered to have reached an anaerobic threshold (A.T.), whereas eleven patients did not. The mean value of VO2 max of the former group was 1.141·min-1, which was significantly greater than that of the latter group, 0.71·min-1. This difference was mainly attributed to that of ventilatory function.
It was found that the A.T. was difficult to determine from the changes of gas exchange ratio or VE in patients who developed CO2 retention during exercise.
The mean oxygen uptake at A.T. in 24 patients was 0.908±0.215 (0.596-1.481)1·min-1, which was slightly lower than that in healthy subjects of comparable age. It can be said that the cardiovascular response to exercise in these patients were not so disturbed as compared to cardiac patients.
The decrease of PaO2 during exercise was not necessarily associated with the increase of blood lactate, suggesting the presence of a compensatory mechanism for oxygen transport.
