CORRELATION OF NONSPECIFIC BRONCHIAL RESPONSIVENESS TO BASE-LINE PULMONARY-FUNCTION IN PATIENTS WITH ASTHMA AND SINOBRONCHIAL SYNDROME

To examine the relationship of nonspecific bronchial responsiveness to baseline pulmonary function, and to compare the reactivity in asthma and sinobronchitis, we measured the provocative concentration of metha choline, causing a 20% fall in forced expiratory volume in one second (PC20-FEV1) in 82 asthmatic patients, 54 patients with sinobronchial s yndrome and 57 normal subjects. Log PC20-FEV1 was directly correlated to baseline pulmonary function. The strongest correlation was seen bet ween log PC20-FEV1 and baseline FEV1 as a % of the predicted FEV1 (%FE V1), both in asthma (log PC20-FEV1 = 0.020 X %FEV1 -1.988, r = 0.54, p < 0.01) and in sinobronchial syndrome (log PC20-FEV1 = 0.025 x %FEV1 -1.233, r - 0.64, p < 0.01). From the regression equations, the mean v alue Of PC20-FEV1 at 100% FEV1 was calculated as 1.02 and 18.5 mg/ml i n asthmatic and sinobronchitic patients, respectively, and the value w as 35.5 mg/ml in normal subjects. The PC20-FEV1 to %FEV1 relationship may be helpful to assess individually measured PC20-FEV1 values in pat ients with airway obstruction.