Cold air inhalation has a cumulative bronchospastic effect when inhaled in consecutive doses for progressively increasing degrees of ventilation

Abstract

In 12 asthmatic subjects, we compared the bronchoconstriction obtained with 3 methods of isocapnic inhalation of cold dry air (IICDA) on 6 visits, two visits for each method: Dose-response curves (DRC), which were obtained by asking the subjects to inhale at progressively increasing degrees of ventilation (7.5, 15, 30, 60 L/min and maximal voluntary ventilation [MVV] at a fixed breathing rate); free MVV, i.e., breathing frequency not set; same degree of ventilation as the last required for DRC (VEeq). Degrees of ventilation were significantly greater with the free MVV method. The percentage fall in FEV1 obtained by VEeq method was significantly lower than the changes recorded with the DRC and the MVV methods, the 2 latter being not significantly different. We conclude that IICDA induces a cumulative bronchoconstriction by the DRC method. However, the bronchoconstriction obtained with the latter method is not significantly different from the one obtained with the free MVV method.