title: Anatomic and physiologic predictors of apnea severity in morbidly obese subjects.
abstract: OBJECTIVE
  While obesity is the most common risk factor for the development of obstructive sleep apnea, the correlation between measures of obesity and apnea severity is only moderate. We thus attempted to identify anatomic and physiologic predictors of apnea severity.
  
  
  METHODS
  We combined a careful assessment of upper airway anatomy, upper airway physiology, and ventilatory control in a group of obese individuals to identify predictors of apnea severity.
  
  
  METHODS
  Tertiary care academic medical center.
  
  
  METHODS
  14 morbidly obese subjects being evaluated for weight-reduction surgery.
  
  
  METHODS
  N/A MEASUREMENT AND RESULTS: We found no relationship between obesity (weight or body mass index) and apnea severity (respiratory disturbance index, RDI). However, those with severe apnea (RDI > 30) were found to have higher peak genioglossus EMG (GGEMG) (23.5 +/- 1.9 vs. 14.1 +/- 3.7 %max, p = 0.05) and greater airway collapsibility during pulses of negative pressure (7.6 +/- 0.9 vs. 4.4 -/+/-0.7 cmH2O, p =0.02). Airway collapsibility was significantly associated with RDI (r = 0.62, p < 0.01) as was peak GGEMG (r = 0.55, p < 0.05). Of the anatomic variables airway shape (A-P/lateral ratio) and volume change of the pharyngeal airway between total lung capacity and residual volume were different between those with and without severe apnea. Both correlated with RDI (A-P/lateral ratio: r = 0.70, p < 0.01 and volume change: r = 0.77, p < 0.01).
  
  
  CONCLUSIONS
  We believe these findings suggest that specific anatomic and physiologic properties of the airway interact with obesity to predispose to the development of airway collapse during sleep.
authors.affiliation: Divisions of Sleep Medicine and Pulmonary/Critical Care, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston MA, USA. rfogel@partners.org
authors.forename: Robert B
authors.initials: RB
authors.lastname: Fogel
authors.forename: Atul
authors.initials: A
authors.lastname: Malhotra
authors.forename: Georgia
authors.initials: G
authors.lastname: Dalagiorgou
authors.forename: Malcolm K
authors.initials: MK
authors.lastname: Robinson
authors.forename: Marianna
authors.initials: M
authors.lastname: Jakab
authors.forename: Ron
authors.initials: R
authors.lastname: Kikinis
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Pittman
authors.forename: David P
authors.initials: DP
authors.lastname: White
mesh_terms: D000328:Adult; D015992:Body Mass Index; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications* / Q000175:diagnosis*; D010614:Pharynx / Q000033:anatomy & histology* / Q000502:physiology; D017286:Polysomnography; D011237:Predictive Value of Tests; D012129:Respiratory Function Tests; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis / Q000209:etiology*