Cough frequency and cough receptor sensitivity to citric acid challenge during a simulated ascent to extreme altitude.

The aim of this study was to determine the frequency of cough and the citric acid cough threshold during hypobaric hypoxia under controlled environmental conditions. Subjects were studied during Operation Everest 3. Eight subjects ascended to a simulated altitude of 8,848 m over 31 days in a hypobaric chamber.