EFFECT OF AMINOPHYLLINE ON VENTILATORY RESPONSES IN NORMAL MAN

Abstract

The bronchodilator effects of aminophylline are well documented, but its effect on ventilatory drives was not systematically evaluated. Accordingly, the ventilatory responses to hypoxia and to hypercapnia were measured before and after the i.v. administration of aminophylline at 5 mg/kg of body wt to 6 normal subjects. Hypoxic ventilatory response, as measured by an index of the relation between ventilation and hypoxia (parameter A) increased from a mean .+-. SE control value of 146 .+-. 25 to 254 .+-. 35, 75 min after the infusion (P < 0.05). Significant increases in A were also noticed immediately after, and 35 and 50 min after, the aminophylline infusion. O2 consumption increased from a control value of 235 .+-. 21 to 263 .+-. 21 ml/min STPD [Standard Temperature and Pressure, Dry] (P < 0.03), and CO2 production increased from 184 .+-. 12 to 202 .+-. 13 ml/min STPD (P < 0.01) after aminophylline. Hypercapnic ventilatory response, measured as the slope of the ventilatory response to hypercapnia, was not altered after the aminophylline. In addition to bronchodilation, the augmentation of the ventilatory response to hypoxia may be a useful factor when this drug is used in acute respiratory failure secondary to airway obstruction.