[Bronchoconstriction in isocapnic hyperventilation-induced asthma].

It is well known that some asthmatic patients develop bronchoconstriction after exercise challenge (exercise-induced asthma, EIA). Recently, it has been pointed out that isocapnic hyperventilation also induces similar bronchoconstriction (hyperventilation-induced asthma, HIA) in the same asthmatic subjects. However, the mechanism of HIA has not yet been determined. In the present study, we performed exercise and hyperventilation challenge in the same patients and pulmonary function data and neutrophil chemotactic factor (NCF) in peripheral blood were examined before and after both challenges. Twelve asthmatic patients with normal pulmonary function data on testing days were subjected to exercise test on a bicycle ergometer and then isocapnic hyperventilation tests in subsequent days. Subjects breathed dry air from the cylinder. Isocapnic hyperventilation was performed by monitoring minute ventilation and each patient followed the same minute ventilation exercise. The reduction of FEV1.0 and time course of airway obstruction were almost the same after exercise and hyperventilation testing. All patients who developed EIA also developed HIA and other patients did not develop both EIA and HIA. Changes of Rrs, V50 and V25 and their time course after each test were also similar in EIA(+) and HIA(+), and in EIA(-) and HIA(-). NCF increased significantly after both challenges in EIA(+) and HIA(+) patient, although increment of NCF was much less these the increases of HIA(+). These data may suggest that the development of bronchoconstriction was compatible after exercise and hyperventilation in each asthmatic patient, however, the mechanism of HIA may differ from EIA, although NCF slightly but significantly increased in HIA, suggesting the possible role of a chemical mediator.