Correlation of Nonspecific Bronchial Responsiveness to Baseline Pulmonary Function in Patients with Asthma and Sinobronchial Syndrome

Abstract

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 methacholine, causing a 20% fall in forced expiratory volume in one second (PC₂₀-FEV₁) in 82 asthmatic patients, 54 patients with sinobronchial syndrome and 57 normal subjects. Log PC₂₀-FEV₁ was directly correlated to baseline pulmonary function. The strongest correlation was seen between log PC₂₀-FEV₁ and baseline FEV₁ as a %of the predicted FEV₁ (%FEV₁), both in asthma (log PC₂₀-FEV₁ = 0.020x %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 value of PC₂₀-FEV₁ at 100% FEV₁ was calculated as 1.02 and 18.5 mg/ml in asthmatic and sinobronchitic patients, respectively, and the value was 35.5 mg/ml in normal subjects. The PC₂₀-FEV₁ to %FEV₁ relationship may be helpful to assess individually measured PC₂₀-FEV₁ values in patients with airway obstruction.
(Internal Medicine 32: 1-5, 1993)