Objective Chronic cough is often present as increasing cough reaction to various physical and chemical stimulating factors. This study is aimed to investigate the difference of cough sensitivity and its mechanisms which are not clear among different causes of chronic cough.
Methods Patients with chronic cough were recruited from cough clinic of Guangzhou Institute of Respiratory Diseases between 2005 to 2010. Using a modified diagnostic algorithm of chronic cough, common causes were identified. Capsaicin cough provocation test was also performed in these patients to assess the cough threshold. The relations between cough reflex sensitivity and duration of cough, cough severity, pulmonary function, induced sputum cell counts were then investigated.
Results Through the diagnostic algorithm of chronic cough, the current study evaluated 133 adult patients, including 24 cases with upper airway cough syndrome (UACS) , 26 patients with cough variant asthma (CVA) , 31 cases with eosinophilic bronchitis (EB) , 30 patients with atopic cough (AC) , 22 cases with gastroesophageal reflux induced cough (GERC) . There were 30 healthy volunteers recruited as normal control. The cough threshold of LgC5 in AC, CVA, EB, GERC and UACS was 1.70 ±0.70, 2.12 ±0.67, 2.13 ±0.69, 1.69 ±0.73, 2.16 ±0.66, respectively. The LgC5 of the normal group ( 2.63 ±0.39) was higher than those in chronic cough groups( All P lt; 0.05) . The LgC5 of AC and GERC were lower than CVA, EB and UACS ( all P lt;0.05) . Duration and daytime score of cough showed positive correlations with LgC5( r =-0. 280, -0. 168, all P lt;0.05) . Pulmonary function and differential cell count of induced sputumwere not associated with LgC5 ( all P gt;0.05) .
Conclusions Different cause of chronic cough exhbit high cough reflex sensitivity to different extent. The difference of cough sensitivity may reflect the different pathogenesis among different causes, and may be related to the type of nerve fiber dominating the cough reflex.
Citation： CHEN Ruchong,LIU Chunli,LUO Wei,LAI Kefang,ZHONG Nanshan. Difference of Capsaicin Cough Sensitivity in Common Causes of Chronic Cough. Chinese Journal of Respiratory and Critical Care Medicine, 2013, 12(4): 384-389. doi: 10 . 7507 /1671 -6205 . 20130092 Copy