[Relations between nonspecific bronchial hyperreactivity, diurnal variation of peak expiratory flow and medication...

To assess the relation between non-specific bronchial hyperreactivity, we recorded diurnal peak expiratory flow variation (PFV) and asthma symptoms in 36 individuals with mild allergic asthma. The patients were challenged with methacholine to induce decreases greater than 40% in FEV1, or until a maximum of 200 mg/ml had been administered. Over the next 14 days, PFV was measured three times per day and symptoms and inhaled salbutamol requirements were recorded. In the 11 patients with complete dose-response curves, the geometric mean of diurnal PFV variation (% mean range) was 5.0%; this parameter was 8.3% (p < 0.01) in the 25 subjects whose curves did not reach a plateau. A correlation (r = -0.56, p < 0.001) was found between PC20 and % mean range. PFV for the sample as a whole. In the 11 patients with complete curves, however, no correlation (r = -0.31, p = NS) between % mean range of PFV and PC20 was found. Nor could the plateau (r = 0.19, p = NS) or EC50 (r = -0.26, p = NS) be found for these patients. The geometric mean for PC20 in the 12 subjects who needed salbutamol throughout the 14-day study period after methacholine challenge was 1.06 mg/ml; this parameter was 1.32 mg/ml (p = NS) for those with no symptoms. A plateau was reached by 2 of the 12 patients who experienced asthma symptoms and in 9 of the 24 who were asymptomatic (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)