Effect of aminophylline on ventilatory response to hypercapnea in patients with asthma

The nature of ventilatory response to CO2 in patients with airway obstruction is controversial. Although the bronchodilating effect of aminophylline has been well documented, its effect on direct stimulation of breathing has not been systematically evaluated. Therefore, the effect of intravenous aminophylline on ventilatory response to CO2 of patients with asthma was studied by comparing with that of the healthy subjects. Ventilation (VE) at rest was not significantly different between in asthmatics and healthy subjects, and mouth occlusion pressures (P0.1) at rest was significantly higher in asthmatics than in healthy group (p less than 0.05). P0.1 after aminophylline increased significantly (p less than 0.05) compared to control value in asthmatics. Changes in VE and P0.1 relatively correlated well in both groups before and after aminophylline (r = 0.58). Ventilatory response to CO2 (VE/PA CO2) and P0.1 response to CO2 (P0.1/PACO2) in asthmatics were slightly increased, but not significantly different from those in the healthy group before and after aminophylline. These findings suggest that aminophylline might be effective in enhancing ventilatory response to CO2 in asthmatics than in healthy subjects, because of its bronchodilating effect and stimulation to the respiratory neurons.