Deep nasal inspirations increase the cough threshold in children with mild asthma

Asthma is a chronic inflammatory disease characterized by bronchospasms accompanied with frequent coughing, the pathogenesis of which is not clear. In healthy adults deep inspirations (DIs) provide a protective effect against bronchoconstriction triggered by methacholine inhalation, which correlates with the number of accompanying cough efforts. The aim was to study the effect of deep nasal inspirations representing the voluntary equivalent of the sniff-like aspiration reflex on the capsaicin-induced cough in children with mild asthma. The cough reflex sensitivity to capsaicin was determined using a compressed air-driven nebulizer in 21 children (8 girls and 13 boys of median age 13.3 year) suffering from mild asthma (FEV(1)∼80%). The effect of five previous DIs through the nose was examined on the elicitability of two and five or more cough efforts (C2, C5). Under control conditions, the concentration of 20.86 (14.58-29.8) μmol/l of capsaicin provoked two cough efforts (C2). After five DIs similar reaction required significantly higher concentrations of capsaicin: 29.02 (18.88-44.6) μmol/l; P=0.016. Five or more cough efforts (C5) were not significantly changed after previous DIs 161.49 (77.31-337.33) μmol/l and without DIs 141.52 (68.77-291); P=0.54. A series of five deep inspirations decreases the cough reflex sensitivity to evoke two efforts (C2) in children with mild asthma. The inhibitory effect of similar DIs disappeared after repeated applications of increasing doses of capsaicin, aiming to evoke five or more cough efforts, suggesting a reflex character of protective effect of DIs.