title: Airway responsiveness measured by forced oscillation technique in severely obese patients, before and after bariatric surgery.
abstract: BACKGROUND
  The influence of obesity on airway responsiveness remains controversial.
  
  
  OBJECTIVE
  This study was designed to investigate airway responsiveness, airway inflammation, and the influence of sleep apnea syndrome (SAS), in severely obese subjects, before and after bariatric surgery.
  
  
  METHODS
  A total of 120 non-asthmatic obese patients were referred consecutively for pre-bariatric surgery evaluation. Lung function, airway responsiveness to methacholine, exhaled nitric oxide measurement, and sleep studies were performed. Airway hyperresponsiveness (AHR) was defined as a 50% or greater increase in respiratory resistance measured using the forced oscillation technique in response to a methacholine dose ≤ 2000 μg. Forced expiratory volume in 1 second (FEV₁) was measured after the last methacholine dose. Airway responsiveness was reevaluated after weight loss in patients with a pre-surgery AHR.
  
  
  RESULTS
  AHR was found in 16 patients. The percent FEV₁ decrease or percent respiratory resistance increase in response to methacholine was related to baseline expiratory airflow (forced expiratory flow at 50%) (r = 0.26, p < .006 and r = 0.315, p = .0005, respectively) but not to body mass index (BMI) or exhaled nitric oxide. Both airway responsiveness parameters were significantly related to forced expiratory flow at 25-75%/forced vital capacity, a measure of airway size relative to lung size (r = 0.27, p < .005 and r = 0.25, p < .007, respectively). Sleep apnea was not significantly associated with AHR or airway inflammation. About 11 patients with AHR were reevaluated 18 months to 2 years after surgery, with no change in AHR associated with weight loss.
  
  
  CONCLUSIONS
  Airway responsiveness is not related to BMI or to SAS. AHR in severely obese patients might be related to distal airway obstruction or low relative airway size.
authors.affiliation: Service de Physiologie-Explorations Fonctionnelles, Hôpital Henri Mondor, AP-HP, Creteil, France. francoise.zerah@hmn.aphp.fr
authors.forename: Françoise
authors.initials: F
authors.lastname: Zerah-Lancner
authors.forename: Laurent
authors.initials: L
authors.lastname: Boyer
authors.forename: Saida
authors.initials: S
authors.lastname: Rezaiguia-Delclaux
authors.forename: Marie-Pia
authors.initials: MP
authors.lastname: D'Ortho
authors.forename: Xavier
authors.initials: X
authors.lastname: Drouot
authors.forename: Isabelle
authors.initials: I
authors.lastname: Guilloteau-Schoennagel
authors.forename: Stephan
authors.initials: S
authors.lastname: Ribeil
authors.forename: Christophe
authors.initials: C
authors.lastname: Delclaux
authors.forename: Serge
authors.initials: S
authors.lastname: Adnot
authors.forename: Claude
authors.initials: C
authors.lastname: Tayar
mesh_terms: D000328:Adult; D050110:Bariatric Surgery; D001944:Breath Tests; D016535:Bronchial Hyperreactivity / Q000276:immunology* / Q000503:physiopathology; D001985:Bronchial Provocation Tests / Q000379:methods; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride / Q000008:administration & dosage; D009569:Nitric Oxide / Q000378:metabolism; D009767:Obesity, Morbid / Q000276:immunology* / Q000503:physiopathology / Q000601:surgery; D011446:Prospective Studies; D012891:Sleep Apnea Syndromes / Q000276:immunology* / Q000503:physiopathology; D013147:Spirometry / Q000379:methods
chemical_list: D016210:Methacholine Chloride; D009569:Nitric Oxide