Reversibility of small airway obstruction after therapy with salbutamol. Studies in asymptomatic asthmatic patients after inhalation of pressurized aerosol

A group of 18 asymptomatic asthmatic patients and a control group of five healthy individuals were examined in order to evaluate the effect of inhalation of 400 microng of salbutamol on the small airways. All patients were free of symptoms for at least three days before the investigation. On the day of investigation, total lung resistance, static lung compliance, and dynamic compliance at a respiratory frequency of 60 breaths per minute (Cdyn60) were measured. While no change in Cdyn60 occurred in the control group, a statistically significant decrease in Cdyn60 was found before inhalation of salbutamol in all 18 asthmatic patients (P less than 0.005), indicating obstruction of small airways. After inhalation of 400microng of salbutamol, a significant increase in Cdyn60 occurred (P less than 0.005), starting five minutes after inhalation and lasting over one hour, indicating an almost complete abolishment of the frequency dependence of lung compliance in these patients. The present findings indicate that sulbutamol aerosol has a potent bronchodilator effect on the large, as well as the small, airways in the early stage of recovery following an acute asthmatic attack.