Preoxygenation Is More Effective in the 25[degrees] Head-up Position Than in the

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Preoxygenation Is More Effective in the 25[degrees] Head-up Position Than in the Supine Position in Severely Obese Patients: A Randomized Controlled Study.
Anesthesiology. 102(6):1110-1115, June 2005.
Dixon, Benjamin J. M.B.B.S. *; Dixon, John B. M.B.B.S., Ph.D., F.R.A.C.G.P. +; Carden, Jennifer R. M.B.B.S., F.A.N.Z.C.A. ++; Burn, Anthony J. M.B.B.S., F.A.N.Z.C.A. ++; Schachter, Linda M. M.B.B.S., F.R.A.C.P.; Playfair, Julie M. R.N.; Laurie, Cheryl P. R.N., R.M. ; O'Brien, Paul E. M.D., F.R.A.C.S. #

Background: Class III obese patients have altered respiratory mechanics, which are further impaired in the supine position. The authors explored the hypothesis that preoxygenation in the 25[degrees] head-up position allows a greater safety margin for induction of anesthesia than the supine position.

Methods: A randomized controlled trial measured oxygen saturation and the desaturation safety period after 3 min of preoxygenation in 42 consecutive (male:female 13:29) severely obese (body mass index > 40 kg/m2) patients who were undergoing laparoscopic adjustable gastric band surgery and were randomly assigned to the supine position or the 25[degrees] head-up position. Serial arterial blood gases were taken before and after preoxygenation and 90 s after induction. After induction, ventilation was delayed until blood oxygen saturation reached 92%, and this desaturation safety period was recorded.

Results: The mean body mass indexes for the supine and 25[degrees] head-up groups were 47.3 and 44.9 kg/m2, respectively (P = 0.18). The group randomly assigned to the 25[degrees] head-up position achieved higher preinduction oxygen tensions (442 +/- 104 vs. 360 +/- 99 mmHg; P = 0.012) and took longer to reach an oxygen saturation of 92% (201 +/- 55 vs. 155 +/- 69 s; P = 0.023). There was a strong positive correlation between the induction oxygen tension achieved and the time to reach an oxygen saturation of 92% (r = 0.51, P = 0.001). There were no adverse events associated with the study.

Conclusion: 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.

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Canadian Journal of Anesthesia 54:744-747 (2007)
© Canadian Anesthesiologists' Society, 2007
Case Reports/Case Series
Noninvasive bilevel positive airway pressure for preoxygenation of the critically ill morbidly obese patient
[La ventilation en pression positive non invasive à bi-niveau pour la préoxygénation des obèses morbides sévèrement malades]
Mohamad F. El-Khatib, PhD, Ghassan Kanazi, MD and Anis S. Baraka, MD
From the Department of Anesthesiology, American University of Beirut, Beirut, Lebanon.

Address correspondence to: Dr. Anis Baraka, Professor & Chairman, Department of Anesthesiology, American University of Beirut, P.O.Box: 11-0236, Beirut 1107 2020, Lebanon. Phone: 00-961-1350000, ext. 6380; Fax: 00-961-1; E-mail:

Purpose: We describe the use of noninvasive bilevel positive airway pressure (BiPAP) in a critically ill, hypoxemic and morbidly obese patient for preoxygenation prior to rapid sequence induction of anesthesia.

Clinical features: A critically ill morbidly obese patient (body mass index: 49 kg·m–2) was scheduled for urgent laparoscopic cholecystectomy. Preoxygenation with 5 L·min–1 oxygen flow resulted in a moderate increase in oxygen saturation (SpO2) from 79% to 90%. Prior to rapid sequence induction of anesthesia, a trial of noninvasive BiPAP with oxygen delivery at 5 L·min–1 increased his SpO2 to 95% initially, with full saturation of 99% achieved when oxygen flow was increased to 10 L·min–1. Bilevel positive airway pressure with an inspiratory and expiratory pressures of 17 cm H2O and 7 cm H2O, respectively, was applied using a full face mask to achieve a tidal volume of 8 mL·kg–1. Rapid sequence induction proceeded uneventfully.

Conclusions: Prior to rapid sequence induction of anesthesia in patients with respiratory compromise secondary to factors which reduce FRC, noninvasive BiPAP in combination with supplemental oxygen may be indicated whenever traditional preoxygenation does not provide adequate oxyhemoglobin saturation. Improved oxygenation is most likely attributable to improved ventilation and alveolar recruitment.


That was a good study conducted and produced. Logically it sounds very right, spicially for very high risk patients with compromised resp reserves. I will certainly give it a try on my next 100 cases and compare the results in our set up in small time private practice in Mumbai, India.


As mentioned about a year back, I did try out preoxygenation with a Bipap, in high risk septic patients. The result was quite encouraging.
I also heard lecture by Dr. Moraro from Rome ( I hope I am right). He presented a series of cases under GA, along with post op CT scan pictures showing basal atalacacis in practicallyy all patients after, even a 15 min surgery. In high risk, and now for all patients, he recommends use of Bipap venti frequently to improve the CT scan picture. It is also a good point to note.


i also find this slight head up position useful while intubating obese patients with big breasts when the introduction of laryngoscope is difficult.i find this slight head up position with chin above the level of breast very useful.waiting for comments from senior people.