Comparative bronchodilator responses to atropine and terbutaline in asthma and chronic bronchitis

We have compared bronchodilator responses to atropine and terbutaline in 39 chronic bronchitics and 16 stable asthmatics. Fasting subjects were given either 1.05 mg atropine of 5.0 mg terbutaline orally. Pulmonary function was assessed using the peak responses, namely: three 60-minute intervals for terbutaline and three 30-minute intervals for atropine. A subgroup of five reactive bronchitis patients was given a placebo with no response. Areas under the percent response-time interval curve were compared. Both patient groups responded to the same degree to atropine and terbutaline with respect to reduction of airway resistance. However, the FEV1 and V50 responses to terbutaline were markedly enhanced compared to atropine in the asthmatics while equal to the atropine response in the bronchitis patients. Thus, atropine appears to exert its effect upon both large and small airways in bronchitis, but predominantly on large airways in asthma. The results are consistent with a state of enhanced vagal tone in small airways in bronchitis compared to asthma, but other explanations are conceivable.