[Bronchial response to acetylcholine and Dermatophagoides pteronissimus in asymptomatic asthmatics].

Bronchial reactivity to increasing concentrations of acetylcholine (from 0.01 to 10 mg X ml-1) was studied in 84 asthmatic patients during a remission period. Three groups were identified based on decreasing reactivity : group 1 : 57 patients (68%) who exhibited a decrease equal or of more than 20% of forced expiratory volume per second (FEV1) and a decrease equal or of more than 35% of specific airway conductance (sGaw); group 2: 16 patients (19%) with a decrease in FEV1 of less than 20%, but a decrease in sGaw still equal or superior to 35%; group 3 : 11 patients (13%) with a less than 20% decrease in FEV1 and a less than 35% decrease of sGaw. Basal measurements of FEV1 and sGaw gave significantly lower values in group 1 than in group 2 and in group 2 than in group 3. A strong positive relationship was found between initial FEV1 (% of predicted) and acetylcholine concentration giving a fall of 20% in FEV1 (PD20-FEV1) (r = 0.87; p less than 0.001); a weak but still statistically significant relationship existed between initial sGaw and PD35-sGaw (r = 0.38; p less than 0.01). Twenty-five patients with allergic asthma were submitted to an inhalation test with Dermatophagoides pteronissimus (Dpt). Bronchial reactivity to Dpt was significantly correlated with acetylcholine (r = 0.9; p less than 0.001). Twenty-four hours after Dpt exposure, seven patients (28%) still presented bronchial obstruction. Eleven patients without persistent obstruction 24 h after Dpt exposure were resubmitted to acetylcholine; bronchial reactivity was found increased when compared to the initial acetylcholine-induced bronchospasm.(ABSTRACT TRUNCATED AT 250 WORDS)