[Study of spontaneous resolution of bronchial spasm after methacholine challenge. Comparison of patients with...

The study was designed to assess the spontaneous recovery of bronchial spasm induced by methacholine in bronchial challenge tests and to examine the mechanisms and the modalities involved as well as the influence of dosage. The phenomenon was analysed in 32 hyperreactive patients diagnosed as asthmatics by measuring FEV1 as soon as maximum bronchial constriction (PD20) had been achieved and after 5, 10, 15, 30 and 60 minutes. The data obtained were subjected to variance analysis. Results show: 1) as regards duration of spontaneous recovery, that FEV1 returned to pre-challenge levels after 60 minutes in both the severely and moderately hyperreactive patients; 2) as regards onset of regression, that onset depended on the level of sensitivity, occurring after 30 minutes in the severely affected, after 15 minutes in the mild cases; 3) as regards recovery intensity, that in the moderated cases the recovery was more pronounced in the first 15 minutes than subsequently. Data show that the onset and intensity of the spontaneous recovery change according to the degree of sensitivity. That might reflect a greater affinity and/or bonding of methacholine in the muscarinic receptors of the severely affected, but the possibility of a difference in mediator metabolization speed cannot be excluded. In conclusion, research into the recovery of bronchial spasm may contribute to a better understanding of bronchial hypersensitivity and provide new information of value on the diagnosis, pathogenesis and treatment of the condition.