In anaesthetics we are trained to pre-oxygenate and intubate our theatre patients in a flat supine position. Then, when we graduate to intubating the really gnarly ICU/ED patients in severe heart or respiratory failure, we wise up. A paper in Anaesthesia & Analgesia demonstrates how patients who are intubated in a semi-sitting position are less likely to suffer complications when intubated.
Laying a truly marginal COPD/pulmonary oedema patient flat before the RSI is rarely a good idea. Instead, as long as their blood pressure is reasonably stable, we pre-oxygenate them in a semi-sitting position with the neck somewhat extended. We carefully titrate the meds and intubate them while standing on a stool. This is the Back Up Head Elevated (BUHE) position.
While we understand the physiological merits of non-supine airway management (Sitting reduces venous return and preload, shifts volume out of the thorax, functional residual capacity and lung volumes increase etc), we rarely consider the benefits specific to airway management.
Evidence supporting non-supine airway management
There are a few studies exploring non-supine endotracheal intubation. Most of them deal with BUHE pre-oxygenation but theres one demonstrating improved laryngoscopy views.
Lane et al. 2005.: ¨Mean (95% CI) apnoea time was 386 (343-429) s in the 20 degrees head-up position (n = 17) vs 283 (243-322) s in the supine position (n = 18; p = 0.002). Pre-oxygenation is significantly more efficacious and by inference more efficient in the 20 degrees head-up position than in the supine position.¨
Ramkumar et al. 2011: ¨Preoxygenation is clinically and statistically more efficacious and by inference more efficient in the 20º head-up position than with conventional technique in non-obese healthy adults. Although application of 5 cmH(2)O PEEP provides longer duration of non-hypoxic apnea compared to conventional technique, it is not statistically significant.¨
Altermatt et al.: ¨Pre-oxygenation in sitting position significantly extends the tolerance to apnoea in obese patients when compared with the supine position.¨
Dixon et al. 2005: ¨Preoxygenation in the 25 degrees head-up position achieves 23% higher oxygen tensions, allowing a clinically significant increase in the desaturation safety period–greater time for intubation and airway control. Induction in the 25 degrees head-up position may provide a greater safety margin for airway control.¨
Boyce et al. 2003: ¨In morbidly obese patients, the 30 degrees Reverse Trendelenburg position provided the longest safe apnoea period when compared to the 30 degrees Back Up Fowler and Horizontal-Supine positions. Since on induction of general anesthesia morbidly obese patients may be difficult to mask ventilate and/or intubate, this extra time may preclude adverse sequelae resulting from hypoxemia. Therefore, Reverse Trendelenburg is recommended as the optimal position for induction.¨
Lee et al. 2007: ¨During laryngoscopy, the laryngeal view, as assessed by POGO scores, improves significantly in the 25 degrees back-up position when compared with the flat supine position.¨
The study in Anesthesia & Analgesia was a retrospective observational analysis from two academic medical centres of procedural notes recording intubation technique, no of attempts, laryngeal views and patient positioning. The authors compared complications in patients who were intubated supine (<30°) vs with their backs and heads elevated (≥30°).
The authors, Khandelwal et al., enrolled all adult patients who underwent endotracheal intubation outside OR or recovery areas, i.e. emergent intubations. The study excluded patients intubated in cardiac arrest or where direct laryngoscopy was not used. The primary endpoint was the occurrence of intubation related complications. Complications were defined as difficult intubation (>3 attempts, >10 mins duration or surgical airway), hypoxemia, esophageal intubation, or pulmonary aspiration.
The study enrolled 528 patients. In the supine positioning group, 22,6% suffered at least one intubation related complication. In the BUHE group, only 9,3% had complications. Surprising, as one would expect patients in the BUHE group to be sicker or have more difficult airways. Interestingly, the incidence of difficult intubation was not affected by positioning. The reduction in complications with BUHE was driven by fewer episodes of hypoxemia, esophageal intubation and pulmonary aspiration.
I have colleagues, very few, who insist on intubating high-risk patients with their heads down. They argue that this way gastric contents will clear more easily, preventing aspiration. I don´t buy into that nonsense.
The more concerned I am about the patient and the intubation, the more likely I am to elevate the back. Pre-oxygenation improves with heads up positioning, laryngoscopy views improve and complications are less likely to occur.
Shouldn’t then a lot more patients, including the ‘healthy’ OR patients, be intubated in a BUHE position? Patients in circulatory shock or with spinal injury might not tolerate non-supine positioning, but the others, the vast majority?
Study lives here:
Anesth Analg. 2016 Apr;122(4):1101-7. Head-Elevated Patient Positioning Decreases Complications of Emergent Tracheal Intubation in the Ward and Intensive Care Unit. Khandelwal N1, Khorsand S, Mitchell SH, Joffe AM.