Theophylline and diaphragmatic contractility. Investigation of a dose-response relationship.

Our study evaluated whether a dose-response relationship exists for theophylline and diaphragmatic contractility within the usual therapeutic range for theophylline. The study, involving 16 patients with mild to moderate chronic obstructive pulmonary disease, was done in a randomized, placebo-controlled, double-blind, crossover fashion. We found no statistically significant effect of theophylline on diaphragmatic contractility at mean theophylline concentrations of 5.13, 12.07, and 18.6 micrograms/ml.