EFFECT OF CAPSAICIN ON AIRWAY RESPONSIVENESS TO HYPERTONIC SALINE CHALLENGE IN ASTHMATIC AND NONASTHMATIC CHILDREN

Recurrent cough and asthma are common problems in children. In the eva luation of children with recurrent cough, the sequential measurements of airway responsiveness (AR) and capsaicin cough receptor sensitivity may be useful. However, the effect of capsaicin on AR induced by an i ndirect stimulus such as hypertonic saline (HS) is not known. Current evidence suggests that a common pathway is involved in both capsaicin and HS challenges. This study was designed to determine whether inhala tion of capsaicin for the cough receptor sensitivity test before HS ch allenge will alter AR of asthmatic and non-asthmatic children to that challenge. Twenty-one children (12 asthmatics, 9 non-asthmatics; mean age, 11.3 years) performed the HS challenge alone or 2 min after capsa icin inhalation on 2 different days in random order. The end point of the capsaicin inhalation was when greater than or equal to 5 coughs we re stimulated from a single inhalation. The power of the study was >90 % at a significance level of 0.05.Capsaicin inhalation prior to HS cha llenge did not alter the AR of normal children. In the asthmatic group , the PD15 (provocation dose causing a fall in forced expiratory volum e in 1 s of greater than or equal to 15% from the baseline) without pr ior inhalation of capsaicin (mean, 2.44 +/- SEM 1.21 ml) was not signi ficantly different from that when HS challenge was performed after cap saicin inhalation (mean, 2.19 +/- SEM 0.83 ml). The mean of the differ ence in log PD15 of the HS challenge with and without capsaicin was -0 .02 (95% Cl, -0.16, 0.12), i.e. within the equivalence range of the HS challenge in children with asthma. We conclude that in normal and ast hmatic children, capsaicin inhalation does not alter AR to HS; consequ ently the capsaicin cough sensitivity test can be performed validly be fore an HS challenge. (C) 1997 Wiley-Liss, Inc.