Tussigenic agents in the measurement of cough reflex sensitivity

Different inhalation methods are used for cough reflex sensitivity (CRS) measurement. The single-breath method of tussigenic agent aerosol inhalation is widely used now. Comparison of two tussigenic agents--citric acid and capsaicin--in cough reflex sensitivity measurement was used in healthy volunteers. In 17 healthy volunteers (7 M, 10 F; mean age 21 years) without respiratory tract infection in last 3 weeks, without cardiovascular, allergic, respiratory metabolic diseases, and with normal spirometry, cough reflex sensitivity was examined by nebuliser ProvoJet Ganshorn Medizin Elektronic, Germany) with doubled concentrations of capsaicin (SIGMA) from 0.49 to 1000 micromol/l and citric acid (LACHEMA) concentrations of 1, 3, 10, 30, 100, 300, 1000 micromol/l. Cough reflex sensitivity was defined as the lowest concentration of tussigenic agents which elicited 2 and 5 coughs (C2, C5). Geometric mean and 95% confidence interval (CI) of citric acid C2 was 454.5 (284.8-725.4) mmol/l in 88.2% of volunteers; citric acid C5 was 1000 micromol/l (0) in 47.1% of volunteers. Capsaicin C2 was 23.5 (8.2-67.5) micromol/l in 100% of volunteers and C5 was 263.7 (111.2-625.1) micromol/l in 76.5% of volunteers. We conclude that capsaicin single-breath test is more relevant for cough reflex sensitivity measurement in healthy volunteers than citric acid cough test.