Low dose aminophylline selectively increases upper airway motor activity in normals

Abstract

Because certain pharmacologic agents differentially influence upper airway and diaphragm motor activity, we postulated that the adenosine antagonist theophylline might preferentially increase alae nasi activity in human subjects. Using a double-blinded, randomized, placebo controlled design, we studied the effect of low dose aminophyline (1–2 mg/kg) on alae nasi and diapragm surface electromyographic (EMG) activity. Seven healthy volunteers served as subjects for two trials on separate days. Subjects breathed from a closed circuit while end tidal P CO 2 was held constant in the eucapnic range. During each trial we recorded EMG signals from the alae nasi and diaphragm before and after intravenous infusion of either aminophylline or placebo. After the administration of aminophylline, the mean alae nasi EMG signal increased 87 ± 31 (SD)% ( P<0.005) while the mean diaphragmatic EMG signal did not change. There was no significant change in either the alae nasi or diaphragmatic EMG signal after placebo. There was no change in minute ventilation, tidal volume, or respiratory frequency after either aminophylline or placebo. We speculate that low dose aminophylline produced a selective increase in upper airway muscle activity through stimulation of the reticular activating system.