What factors influence successful endotracheal intubation in the critically ill morbidly obese patient in the intensive care unit?
Smith, Kate M
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Objectives: To determine what factors influence successful endotracheal intubation in the critically ill morbidly obese patient in the intensive care unit? Method: An English language literature search was undertaken using Google scholar, Medline, MD Consult, Cochrane and Cinahl (1975-2009) with the key words ‘obesity’, ‘morbid obesity’, ‘ICU’, ‘intensive care’, ‘airway management’, ‘difficult intubation’, ‘positioning’, ‘critical care’, ‘bag mask ventilation’. Reference lists were examined manually to find further articles. Results: Obesity has become a worldwide epidemic and morbidly obese patients are accessing intensive care services. Thirteen articles were found for analysis. The incidence of difficult intubation was greater in obese patients rather than lean patients; 15.5% and 2.2% respectively (p<0.001). Mallampati scoring had a correlation with ease of laryngoscopy (p < 0.001). Mallampati score was more likely to be higher (loss of pharyngeal structures) in obese versus lean, 27% versus 13% respectively. Neck circumference was found to be an independent risk factor for difficult intubation. Ramped positioning for direct laryngoscopy provided a consistently better laryngeal exposure than the traditional sniff position. Difficult mask ventilation (DMV) was found to be present in those with a body mass index (BMI) >26kg/m². Difficult intubation and high Cormack-Lehane grades were significantly greater in the DMV group. The intubating laryngeal mask airway (ILMA) was inserted with similar ease regardless of Cormack-Lehane grade. Mean arterial oxygen saturations were similar during ILMA insertion for obese and lean, 96% and 98%, respectively. In the reverse Trendelenburg position it took longer for oxygen saturations to fall to 92% during apnoea when compared with the supine position. It took twice as long for patients in the supine position to reach oxygen saturations of 97% when ventilation was re-instituted than those in the reverse trendelenburg position. In the 25 degrees head up position gives 23% higher mean oxygen tension after three minutes of pre-oxygenation. Conclusion: Predictors of difficult intubation are Mallampati class and a large neck circumference for the morbidly obese. Ramped positioning provides a better laryngeal exposure for ease of intubation. With head up positioning oxygenation can be optimised reducing periods when oxygen saturation values fall. The ILMA is a safe and effective rescue device for a failed intubation.