Study Design

• Randomized controlled trial

Subjects

• 42 sequential patients presenting for elective bariatric surgery

Methods

• Both groups received preoxygenation via facemask O2 with normal breathing for 3 minutes: the control group was supine for this while the experimental group was placed in 25 degrees head up position
• Both groups received standard RSI with propofol and suxamethonium

Results (see graphic)

  p = .02 favoring head of bed elevated for time to desaturation

Discussion:

• Head of bed up likely increases oxygen reservoir during preoxygenation by shifting the weight of the patient's torso off the chest

• This likely decreases atelectasis and recruits more alveoli available to receive oxygen, while reducing shunting (see expert artwork illustration)

Conclusion:

• Consider adopting the head of bed elevated approach for preoxygenation

• This technique has subsequently been shown to be effective even for non-obese patients in prolonging time to desaturation after intubation

References

Dixon, Benjamin et al. Preoxygenation Is More Effective in the 25 Degree Head-up Position Than in the Supine Position in Severely Obese Patients. Anesthesiology 2005; 102:1110-5.

Ramkumar V, Umesh G, Ann Philip A. Preoxygenation with 20 degrees head-up provides longer desaturation of non-hypoxic apnea than conventional preoxygenation in non-obese healthy adults. J Anesth 2011; 25:189-194.