Bronchoconstriction due to isocapnic cold air inhalation minimally influences bronchial hyperresponsiveness to methacholine in asthmatic subjects.

The aim of this study was to investigate if bronchial hyperresponsiveness to methacholine could be influenced by a previous bronchoconstriction due to isocapnic inhalation of cold air. Twelve adult asthmatic subjects in a clinical steady state were seen on four different days in a randomized way according to three different sequences. After assessment of spirometry, bronchial responsiveness to inhaled methacholine was determined on each occasion by the provocative concentration causing a fall of 20% in FEV1 (PC20). On two occasions, the methacholine test was preceded by the inhalation of dry cold air which caused significant (greater than 20% change in FEV1) bronchoconstriction. The methacholine test was performed after functional recovery. There was a significant (t = 2.53; p less than 0.05) but minimal (mean changes of 0.65 single two-fold concentration difference) reduction in PC20 after cold air inhalation. It is concluded that cold air-induced bronchoconstriction causes significant but minimal changes in bronchial responsiveness to methacholine in asthmatic subjects.