[Exercise induced hypoxemia and exercise tolerance in patients with COPD and the benefits of oxygen supplementation]

In order to evaluate the benefits of O2 supplementation during exercise, slowly incremental treadmill exercise tests were performed twice with 30 minutes interval rest in fourteen patients with severe COPD. The patients breathed room air. 31/min of compressed air by nasal prongs, and 31/min of supplemental oxygen in single blind fashion at random. The patients who developed arterial desaturation below 88% on exercise, group D, showed slight but significant increase in walked distance (397 m vs 424 m) and significant decrease in breathlessness (22.9 vs 16.9) on oxygen as compared to on air. On the other hand in patients without significant arterial desaturation, group S, there was no improvement in those parameters. The increase in walked distance on oxygen was closely related with the decrease in mean inspiratory flow (VT/Ti), blood lactate level, and CO2 production at identical work load. Plasma human atrial natriuretic peptide (h-ANP) levels in group D increased with exercise from a resting value of 27.6 +/- 6.9 to 44.0 +/- 9.0 on compressed air whereas the increase was significantly suppressed to 35.4 +/- 9.0 on oxygen. In group S there was no difference in the increase of plasma h-ANP levels between air and oxygen breathing during exercise (33.1 +/- 5.1 vs 31.9 +/- 9.6). A close correlation (r = 0.908) was found between mean pulmonary artery pressures and plasma h-ANP levels at rest and during exercise performed in four patients breathing air and oxygen. Those findings suggested that arterial plasma h-ANP levels reflected the right ventricular afterload and that they could be used to evaluate the effectiveness of O2-supplementation during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)