Relief of hypoxia-related bronchoconstriction by breathing 30 per cent oxygen.
Airway resistance decreases when hypoxemic subjects with chronic obstructive pulmonary disease (COPD) breathe 30% O2. To verify this finding and to localize the site of action of O2, flow-volume curves on air and helium-O2 mixtures were obtained before and after subjects breathed 30% O2. Patients with COPD and hypoxemia showed an increase in flow rates and a decrease in the density dependence of flow while breathing 30% O2. Atropine produced a similar change in flow rates and density dependence, but then no further change occurred with 30% O2. Five control subjects with COPD, who performed the same sequence of tests without breathing 30% O2, showed no change in flow rates or density dependence. Normal control subjects also showed no change in flow rates or density dependence while breathing 30% O2. Breathing 30% O2, relieves hypoxia-induced bronchoconstriction and appears to act on large airways.
D000368:Aged; D001991:Bronchitis / Q000628:therapy; D002908:Chronic Disease; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000628:therapy*; D008173:Lung Diseases, Obstructive / Q000628:therapy*; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D010102:Oxygen Inhalation Therapy