EFFECT OF NASAL CONTINUOUS POSITIVE AIRWAY PRESSURE ON METHACHOLINE-INDUCED BRONCHOCONSTRICTION

Bronchial hyper-responsiveness is a cardinal feature of asthma. To det ermine whether nasal continuous positive airway pressure (NCPAP) influ ences airway smooth muscle in response to exogenous stimuli, we examin ed the effect of NCPAP on aerosolized methacholine-induced bronchocons triction in 16 stable asthmatic patients. The dose-response curve for each subject was measured by a log transformation and linear regressio n analysis as well as a formula fitted to the data points to obtain va lues for a (slope) and b (position). The PD(20)FEV(1) significantly in creased in patients receiving 8 cmH(2)O of NCPAP by one doubling dose compared with that in patients using sham pressure. NCPAP shifted the dose-response curves to be flatter, deviated upwards and to the right. The coefficient a, indicating bronchial reactivity, was significantly lower in patients receiving NCPAP. The coefficient b, indicating the bronchial sensitive threshold, was higher after applying NCPAP. In con trast, coefficients a and b did not change in subjects with sham press ure. NCPAP also significantly enhanced the bronchodilator effect of in haled salbutamol in response to methacholine-induced bronchoconstricti on. In summary, we have shown that NCPAP therapy improves bronchial sm ooth reactivity with an increase in PD(20)FEV(1) and a reduction in th e bronchial reactivity and bronchial sensitivity. Therefore, NCPAP may provide an adjuvant therapy in patients with acute bronchial asthma.