title: Obstructive sleep apnea is not a risk factor for difficult intubation in morbidly obese patients.
abstract: BACKGROUND
  Morbid obesity (MO), obstructive sleep apnea (OSA), and neck circumference (NC) are widely believed to be independent risk factors for difficult tracheal intubation. In this study, we sought to determine whether these factors were associated with increased risk of difficult intubation in patients undergoing bariatric surgery. The predictive factors tested were OSA and its severity, as determined by apnea-hypopnea index (AHI), gender, NC, and body mass index (BMI).
  
  
  METHODS
  All sequentially enrolled MO patients underwent preoperative polysomnography. Severity of OSA was quantified using AHI and the American Society of Anesthesiologists' OSA severity scale. All patients had a standardized anesthetic that included positioning in the "ramped position" for direct laryngoscopy.
  
  
  RESULTS
  One hundred eighty consecutive patients were recruited, 140 women and 40 men. The incidence of OSA was 68%. The mean BMI was 49.4 kg/m(2). The mean AHI was 31.3 (range, 0-135). All the patients' tracheas were intubated successfully without the aid of rescue airways by anesthesiology residents. Six patients required three or more intubation attempts, a difficult intubation rate of 3.3%. There was an 8.3% incidence of difficult laryngoscopy, defined as a Cormack and Lehane Grade 3 or 4 view. There was no relationship between NC and difficult intubation (odds ratio 1.02, 95% confidence interval 0.93-1.1), between the diagnosis of OSA and difficult intubation (P = 0.09), or between BMI and difficult intubation (odds ratio 0.99, 95% confidence interval 0.92-1.06, P = 0.8). There was no relationship between number of intubation attempts and BMI (P = 0.8), AHI (P = 0.82), or NC (P = 0.3). Mallampati Grade III or more predicted difficult intubation (P = 0.02), as did male gender (P = 0.02). Finally, there was no relationship between Cormack and Lehane grade and BMI (P = 0.88), AHI (P = 0.93), or OSA (P = 0.6). Increasing NC was associated with difficult laryngoscopy but not difficult intubation (P = 0.02).
  
  
  CONCLUSIONS
  In MO patients undergoing bariatric surgery in the "ramped position," there was no relationship between the presence and severity of OSA, BMI, or NC and difficulty of intubation or laryngoscopy grade. Only a Mallampati score of 3 or 4 or male gender predicted difficult intubation.
authors.affiliation: Department of Anaesthesia and Critical Care, Hospital of University of Pennsylvania, Philadelphia, PA, USA. patrick.neligan@hse.ie
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Neligan
authors.forename: Steven
authors.initials: S
authors.lastname: Porter
authors.forename: Bryan
authors.initials: B
authors.lastname: Max
authors.forename: Guarav
authors.initials: G
authors.lastname: Malhotra
authors.forename: Eric P
authors.initials: EP
authors.lastname: Greenblatt
authors.forename: E Andrew
authors.initials: EA
authors.lastname: Ochroch
mesh_terms: D000328:Adult; D050110:Bariatric Surgery; D015992:Body Mass Index; D005260:Female; D006801:Humans; D007442:Intubation, Intratracheal / Q000009:adverse effects*; D007828:Laryngoscopy / Q000009:adverse effects*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009333:Neck / Q000473:pathology; D009767:Obesity, Morbid / Q000150:complications* / Q000503:physiopathology / Q000601:surgery; D016017:Odds Ratio; D017286:Polysomnography; D011187:Posture; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D012737:Sex Factors; D020181:Sleep Apnea, Obstructive / Q000150:complications* / Q000503:physiopathology