Urge-to-cough and dyspnea conceal perception of pain in healthy adults

Although dyspnea has been shown to attenuate pain, whether urge-to-cough, a respiratory sensation preceding cough, exerts a similar inhibitory effect on pain has not been clarified. We examined the effects of both urge-to-cough and dyspnea on pain induced by thermal noxious stimuli. Urge-to-cough was induced by citric acid challenge and dyspnea was induced by external inspiratory resistive loads. During inductions of two respiratory sensations, perception of pain was assessed by thermal pain threshold (TPTh) and tolerance (TPTo). TPTh and TPTo were significantly increased accompanied by increases in perception of both urge-to-cough and dyspnea. Fractional change in TPTh during dyspnea was significantly correlated with that during urge-to-cough. Fractional change in TPTo during dyspnea was significantly correlated with that during urge-to-cough. The study suggests that both two distinct respiratory sensations, i.e., urge-to-cough and dyspnea may harbor perception of pain. Further studies investigating interactions among these sensations in clinical settings are warranted.