Value Of Capsacin Cough Sensitivity And Airway Inflammation Detection In Chronic Cough

Objectives To explore the value of capsaicin cough reflex sensitivity and airway inflammation detection in chronic cough.Part OneMethods 104 patients with chronic cough,who were referring to Department of Respiratory Medicine in our hospital,were recruited into the study between February 2006 and February 2007.The causes of chronic cough included cough-variant asthma, post nasal drip syndrome,gastroesophageal reflux disease and eosinophilic bronchitis. Control group were 98 healthy volunteer.The cough symptom score were recorded, and cough reflex sensitivity with inhaled capsaicin,expressed as the lowest concentration of capsaicin required for the induction of≥2 coughs(C2)or≥5 coughs (C5)was performed at first visit.The cough symptom and cough reflex sensitivity were re-evaluated in 27 patients after successful management of chronic cough.Results Cough symptom score in the patients with chronic cough was 3.754±0.94,C2 and C5 was 1.034±0.22μmol/L and 2.424±0.50μmol/L respectively,which were significantly lower than 2.94±0.28μmol/L and 28.274±6.41μmol/L in control subjects (t=10.41 and 16.84 respectively,P＜0.0001).However,there were no obvious differences in the cough reflex sensitivity among the patients with chronic cough caused by different etiologies.After successful resolution of chronic cough,the cough reflex sensitivity decreased obviously.Apparent negative relation was found between cough symptom score and Log C2 or C5(r=-0.24 and -0.34 respectively,P＜0.05).Conclusion Similar to the cough symptom score,the cough flex sensitivity test with inhaled capsaicin can represent the cough severity at some degree,but have the limited value for cause diagnosis of chronic cough.Part TwoMethods 43 patients with chronic cough referring to Department of Respiratory Medicine in our hospital were recruited into the study between February 2006 and February 2007,who consisted of cough-variant asthma(16 patients),post nasal drip syndrome(10 patients),gastroesophageal reflux diseas(9 patients)and eosinophilic bronchitis(8 patients).Control groups were 10 healthy volunteer and 10 patients of PNDS without chronic cough respectively.The cough symptom score and cough reflex sensitivity(C2 and C5)were recorded.Changes of total cell number, differentials in the induced sputum and the concentration of the histamine and PGE₂ in the supernatant were analyzed.Results C2 and C5 in the patients with chronic cough due to different causes were significantly lower than healthy volunteer and postnasal drip syndrome without chronic cough(P＜0.05).However,the difference between groups of the patients with chronic cough or between healthy volunteer and postnasal drip syndrome without chronic cough was not obvious(P＞0.05).The total inflammatory cell number in induced sputum among the patients with chronic cough and postnasal drip syndrome without chronic cough trended to increased,with decresed macrophage and increased neutrophil differential(P＜0.05).Specially,pronounce eosinophilia in induced sputum was observed in the patients with cough variant asthma and eosinophilic bronchitis compared with the other groups(P＜0.05).Similar to total inflammatory cell number in induced sputum,the concentration of the histamine and PGE₂ in the patients with chronic cough also trended to increase.Among which,postnasal drip syndrome and eosinophilic bronchitis were the most predominant(P＜0.05).Couclusion Airway inflammation may play an importent role in the pathogenesis of chronic cough by increasing cough reflex sensitivity.Activation of mast cell in mucosa in lower airway may be a key pathway linking airway inflammation with the occurrence of cough.