Coughing induced by airway irritation modulates the sensation of air hunger

The aim of this study was to clarify whether coughing elicited by airway irritation can modulate the sensation of air hunger. Using a visual analog scale (VAS), we measured air hunger for 30 s following breakpoint of a breath-hold in healthy young subjects who were asked to resume their breathing according to four patterns (free breathing, citric acid inhalation, voluntary cough, and panting) before and/or after airway anaesthesia. We also measured air hunger for citric acid-induced coughing and voluntary coughing without the preceding breath-holding. The free breathing after breakpoint of breath-holding causes an immediate relief of air hunger (VAS median values at 5, 15 and 25 s after breath-hold: 39, 0 and 0), whereas voluntary coughing causes a delay in the relief of air hunger (67, P < 0.05; 17, P < 0.05; and 0, NS) and a slower relief occurred during citric acid-induced coughing (81, P < 0.01; 49, P < 0.05; and 12, P < 0.05). Conversely, the voluntary coughing and citric acid-induced coughing per se failed to induce air hunger. Inhalation of lidocaine aerosol completely abolished the cough response to citric acid inhalation causing an immediate relief of air hunger, whereas airway anaesthesia alleviated only slightly the air hunger during voluntary coughing. The changes in air hunger during the panting were similar to those during the voluntary coughing observed before airway anaesthesia and were not affected by airway anaesthesia (VAS at 15 s point before versus after anaesthesia: 18 versus 15; NS). Coughing induced by airway irritation per se does not generate the sensation of air hunger but can aggravate it, presumably by vagally mediated mechanisms and/or central mechanisms.