Aminophylline, respiratory muscle strength and exercise tolerance in chronic obstructive airway disease

Fourteen patients with chronic obstructive airway disease participated in a randomized, double-blind, placebo controlled, cross-over study to assess the effect of acutely administered aminophylline on respiratory muscle strength and exercise tolerance. An increase in the distance walked in 6 min occurred following aminophylline (p less than 0.01). There was no improvement in respiratory muscle strength, assessed by maximal static mouth pressures, and no increase in maximal ventilation or oxygen uptake during a progressive exercise test. The ventilatory response to inhaled CO2 was increased (p less than 0.02), suggesting a central stimulatory effect of aminophylline. The mean increase in walking distance was 5.7%. In most cases, the change was small and unlikely to be of practical benefit.