title: Impaired response to deep inspiration in obesity.
abstract: Deep inspirations modulate airway caliber and airway closure and their effects are impaired in asthma. The association between asthma and obesity raises the question whether the deep inspiration (DI) effect is also impaired in the latter condition. We assessed the DI effects in obese and nonobese nonasthmatics. Thirty-six subjects (17 obese, 19 nonobese) underwent routine methacholine (Mch) challenge and 30 of them also had a modified bronchoprovocation in the absence of DIs. Lung function was monitored with spirometry and forced oscillation (FO) [resistance (R) at 5 Hz (R5), at 20 Hz (R20), R5-R20 and the integrated area of low-frequency reactance (AX)]. The response to Mch, assessed with area under the dose-response curves (AUC), was consistently greater in the routine challenge in the obese (mean ± SE, obese vs. nonobese AUC: R5: 15.7 ± 2.3 vs. 2.4 ± 2.0, P < 0.0005; R20: 5.6 ± 1.4 vs. 1.4 ± 1.2, P = 0.027; R5-R20: 10.2 ± 1.6 vs. 0.9 ± 0.1.4, P < 0.0005; AX: 115.6 ± 22.0 vs. 1.5 ± 18.9, P < 0.0005), but differences between groups in the modified challenge were smaller, indicating reduced DI effects in obesity. Given that DI has bronchodilatory and bronchoprotective effects, we further assessed these components separately. In the obese subjects, DI prior to Mch enhanced Mch-induced bronchoconstriction, but DI after Mch resulted in bronchodilation that was of similar magnitude as in the nonobese. We conclude that obesity is characterized by increased Mch responsiveness, predominantly of the small airways, due to a DI effect that renders the airways more sensitive to the stimulus.
authors.affiliation: Division of Pulmonary, Critical Care & Sleep Medicine, Mount Sinai Medical Center, One Gustave L. Levy Place, Box #1232, New York, NY 10029, USA. gwen.skloot@mssm.edu
authors.forename: Gwen
authors.initials: G
authors.lastname: Skloot
authors.forename: Clyde
authors.initials: C
authors.lastname: Schechter
authors.forename: Alpa
authors.initials: A
authors.lastname: Desai
authors.forename: Alkis
authors.initials: A
authors.lastname: Togias
mesh_terms: D000328:Adult; D000403:Airway Resistance; D016535:Bronchial Hyperreactivity / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D001985:Bronchial Provocation Tests; D016084:Bronchoconstriction; D016085:Bronchoconstrictor Agents / Q000008:administration & dosage; D016022:Case-Control Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D001239:Inhalation; D016014:Linear Models; D008168:Lung / Q000503:physiopathology*; D008297:Male; D016210:Methacholine Chloride / Q000008:administration & dosage; D008875:Middle Aged; D009765:Obesity / Q000150:complications* / Q000503:physiopathology; D013147:Spirometry; D014797:Vital Capacity
chemical_list: D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride