Cough Reflex and Obstructive Sleep Apnea Syndrome

Effect of Obstructive Sleep Apnea Syndrome Associated With Obesity on Cough Reflex Threshold to Citric Acid

Up to 70% of obese patients undergoing bariatric surgery have obstructive sleep apnea syndrome (OSAS). OSAS is responsible for laryngeal sensory impairment. As the afferent neural pathway involved in the initiation of cough is located in the laryngeal epithelium, cough reflex sensitivity may be decreased in obese OSAS patients. The researchers therefore conducted this study to determine the effect of OSAS associated with obesity on cough reflex sensitivity, assessed by cough reflex threshold to an inhaled irritant (citric acid).

Obese patients undergoing scheduled bariatric surgery underwent a cough challenge as part of their routine preoperative evaluation. Patients were classified as presenting OSAS if apnea-hypopnea index obtained from preoperative full-night polysomnography was greater than 5/hour. Cough threshold was measured with citric acid. Increasing concentrations of mouth- nebulized citric acid (2.5, 5, 10, 20, 40, 80, 160, 320 and 640 mg/mL) were delivered during inspiration until a cough was elicited. The citric acid concentration eliciting one cough (C1) was defined as the cough reflex threshold.

To compare cough reflex threshold to citric acid between obese OSAS patients and obese non-OSAS patients

To correlate OSAS severity assessed by apnea-hypopnea index and cough reflex threshold to citric acid

Inclusion Criteria: Obese patient scheduled to undergo bariatric surgery Exclusion Criteria: Age less than 18 Active smoking Psychotropic medication Angiotensin-converting enzyme inhibitor or angiotensin II receptor antagonist medication Pregnancy Anesthesia or endotracheal intubation during the previous month Allergic rhinitis Upper airway or bronchopulmonary infection during the previous month Chronic cough Chronic respiratory disease Pharyngolaryngeal disease Neurological disease

Nguyen AT, Jobin V, Payne R, Beauregard J, Naor N, Kimoff RJ. Laryngeal and velopharyngeal sensory impairment in obstructive sleep apnea. Sleep. 2005 May;28(5):585-93. doi: 10.1093/sleep/28.5.585.