Obstructive sleep apnea is not a risk factor for difficult intubation in morbidly obese patients

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. 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.