Perception of urge-to-cough and dyspnea in healthy smokers with decreased cough reflex sensitivity

Fourteen male healthy never-smokers and 14 age-matched male healthy current-smokers were recruited via public postings. The cough reflex sensitivity and the urge-to-cough were evaluated by the inhalation of citric acid. The perception of dyspnea was evaluated by Borg scores during applications of external inspiratory resistive loads.The cough reflex threshold to citric acid, as expressed by the lowest concentration of citric acid that elicited two or more coughs (C2) and the lowest concentration of citric acid that elicited five or more coughs (C5) in smokers was significantly higher than in non-smokers. The urge-to-cough log-log slope in smokers was significantly milder than that of non-smokers. There were no significant differences in the urge-to-cough threshold between non-smokers and smokers. There were no significant differences in perceptions of dyspnea between non-smokers and smokers.The study showed that decreased cough reflex sensitivity in healthy smokers was accompanied by a decreased cognition of urge-to-cough whereas it was not accompanied by the alternation of perception of dyspnea. Physicians should pay attention to the perceptual alterations of cough in smokers.Cough and dyspnea are common respiratory symptoms for which patients seek medical attention. Although cigarette smoking has been implicated as an important risk factor for the development of respiratory symptoms [1-3], the perceptional aspects of cough and dyspnea in smokers have not been fully elucidated. Since tobacco smoking is also associated with an increase in respiratory and non-respiratory infections [4], it is of importance in a clinical setting to know whether perceptional alternations of these two symptoms occur in smokers, and if so, how they are related. However, there have been few studies which investigated both the perceptions of cough stimuli and dyspneic stimuli in smokers.Although dyspnea is a respiratory sensation, cough is a motor action typically preceded by a respiratory