Acute sustained hypoxia suppresses the cough reflex in healthy subjects
Date
2006
Authors
Eckert, D.
Catcheside, P.
Stadler, D.
McDonald, R.
Hlavac, M.
McEvoy, R.
Editors
Advisors
Journal Title
Journal ISSN
Volume Title
Type:
Journal article
Citation
American Journal of Respiratory and Critical Care Medicine, 2006; 173(5):506-511
Statement of Responsibility
Danny J. Eckert, Peter G. Catcheside, Daniel L. Stadler, Rachel McDonald, Michael C. Hlavac, and R. Doug McEvoy
Conference Name
Abstract
Rationale: An intact cough reflex is important to protect the lung from injurious substances and to clear excess secretions. A blunted cough reflex may be harmful or even fatal in respiratory disease. Hypoxia is common in respiratory disorders and has been shown to have depressant effects on respiratory sensation and ventilation. We hypothesized that it might also suppress the cough reflex. Objectives: To determine if acute hypoxia increases cough threshold and cough tachyphylaxis to inhaled capsaicin. Methods: On two occasions, 16 healthy subjects inhaled a saline control followed by doubling doses of capsaicin aerosol (range, 0.49–500 μM) every minute for 15 s during controlled ventilation (∼ 190% baseline) with isocapnic hypoxia (SpO2, ∼ 80%) or isocapnic normoxia, in random order. When a subject responded to a dose with five or more coughs, the next doubling dose of capsaicin was administered continuously for 60 s to assess acute tachyphylaxis. Main Results: The capsaicin concentration required to elicit five coughs was significantly higher during isocapnic hypoxia compared with normoxia (29.6 ± 16.0 vs. 23.4 ± 15.6 μM, p = 0.01). During continuous capsaicin inhalation, significantly more coughs were evoked in the first 10 s compared with the last (2.3 ± 0.3 vs. 1.3 ± 0.3, p < 0.01), indicating cough tachyphylaxis. However, the decrease was the same during hypoxia and normoxia (−1.3 ± 0.4 vs. −0.9 ± 0.6, p = 0.54). Conclusions: Acute isocapnic hypoxia suppresses cough reflex sensitivity to inhaled capsaicin. This finding raises the possibility that the cough reflex may be impaired during acute exacerbations of hypoxic-respiratory disorders.
School/Discipline
Dissertation Note
Provenance
Description
Access Status
Rights
Copyright status unknown