TREADMILL EXERCISE DURATION AND DYSPNEA RECOVERY-TIME IN CHRONIC OBSTRUCTIVE PULMONARY-DISEASE - EFFECTS OF OXYGEN BREATHING AND REPEATED TESTING

Oxygen supplementation is known to improve exercise capacity in patien ts with chronic obstructive pulmonary disease (COPD). Although some CO PD patients use oxygen after exercise to relieve dyspnea, the effect o f oxygen during recovery from exercise is not clearly understood. Exer cise duration and dyspnea recovery time were studied in 18 patients wi th stable COPD. Patients exercised at a constant submaximal work rate on a treadmill ergometer until they no longer wished to continue. Oxyg en, room air and compressed air were randomly administered in three co nsecutive post-exercise recovery periods. Dyspnea was scored on a 100 mm visual analog scale at 30 s intervals until return to baseline. An additional 20 minute post-recovery resting period was allowed between each lest. No significant differences were found in dyspnea recovery t ime breathing oxygen (271 s), room air (290 s) or compressed air (311 s). When the groups were sorted by sequence of testing, there was a hi ghly significant increase in recovery time (208 s, 307 s and 358 s for the first, second and third tests; P<0.005) and a non-statistically s ignificant decrease in exercise duration (89 s, 79 s and 76 s). Post-e xercise oxygen supplementation had no effect on dyspnea recovery time in these COPD patients. Repeated bouts of exercise increased dyspnea r ecovery time and tended to decrease exercise duration. These findings suggest that, despite recovery of symptoms, physiological recovery fro m prior exercise is incomplete.