AIRWAY OBSTRUCTION DUE TO HYPOXEMIA IN PATIENTS WITH CHRONIC LUNG DISEASE

Abstract

Using a whole-body constant volume plethysmograph, estimates of airway resistance and lung volume were obtained in 18 patients with chronic nonspecific lung disease and in a control group of 5 hospital patients without chest disease, after breathing air and after breathing a mixture of 30% O2 in N for 20 min. There was a significant association between airway resistance and arterial O2 tension in the patients with chronic lung disease while breathing air. There was no evidence of a similar relationship involving arterial CO2 tension. After 20 min. of breathing 30% O2, there was a significant reduction of the airway resistance in this group of patients, averaging approximately 20%. The decrease in airway resistance on breathing 30% O2 was significantly related to the severity of the hypoxemia expressed in terms of the arterial O2 tension. There was no consistent change in the airway resistance of the patients of the control group after breathing 30% O2. An intramuscular injection of atropine in 2 patients with chronic lung disease was followed by a decrease in airway resistance of the same magnitude as that which had followed a previous administration of 30% O2. A further period of breathing 30%, after the injection of atropine, was not associated with any further change in airway resistance. When hypoxemia present in patients with chronic lung disease, it is responsible for a part of the increase in airway resistance shown by these patients and that this effect may be reversed, at least temporarily, by the administration of 30% O2.