Risk factors for airway hyperresponsiveness in severely obese women.

Obesity affects airway diameter and tidal ventilation pattern, which could perturb smooth muscle function. The objective was to assess the pathophysiology of airway hyperresponsiveness in obesity while controlling for gastro-oesophageal reflux disease. Obese women (n=118, mean±SD BMI 46.1±6.8kg/m(-2)) underwent pulmonary function testing (including tidal ventilation monitoring and methacholine challenge) and oesogastro-duodenal fibroscopy. Fifty-seven women (48%, 95% CI: 39-57%) exhibited hyperresponsiveness (dose-response slope ≥2.39% decrease/μmol) that was independently and positively correlated with predicted % FRC, Raw0.5 and negatively correlated with sigh frequency during tidal ventilation. Obese women had an increased breathing frequency but a similar sigh frequency than healthy lean women (n=30). Twenty-two obese women (19%, 95% CI: 12-26%) were classified as asthmatics (hyperresponsiveness and suggestive symptoms) without confounding effect of gastro-oesophageal reflux disease. In conclusion, in women referred for bariatric surgery, unloading of bronchial smooth muscle (reduced airway calibre and sigh frequency) is associated with hyperresponsiveness.