A Multicenter, Randomized Trial of Ramped Position vs Sniffing Position During Endotracheal Intubation of Critically Ill Adults

Abstract

Background: Hypoxemia is the most common complication during endotracheal intubation of critically ill adults. Intubation in the ramped position has been hypothesized to prevent hypoxemia by increasing functional residual capacity and decreasing the duration of intubation, but has never been studied outside of the operating room.

Methods: Multicenter, randomized trial comparing the ramped position (head of the bed elevated to 25°) with the sniffing position (torso supine, neck flexed, and head extended) among 260 adults undergoing endotracheal intubation by pulmonary and critical care medicine fellows in four ICUs between July 22, 2015, and July 19, 2016. The primary outcome was lowest arterial oxygen saturation between induction and 2 minutes after intubation. Secondary outcomes included Cormack-Lehane grade of glottic view, difficulty of intubation, and number of laryngoscopy attempts.

Results: The median lowest arterial oxygen saturation was 93% (interquartile range [IQR], 84%-99%) with the ramped position vs 92% (IQR, 79%-98%) with the sniffing position (P = .27). The ramped position appeared to increase the incidence of grade III or IV view (25.4% vs 11.5%, P = .01), increase the incidence of difficult intubation (12.3% vs 4.6%, P = .04), and decrease the rate of intubation on the first attempt (76.2% vs 85.4%, P = .02), respectively.

Conclusions: In this multicenter trial, the ramped position did not improve oxygenation during endotracheal intubation of critically ill adults compared with the sniffing position. The ramped position may worsen glottic view and increase the number of laryngoscopy attempts required for successful intubation.

Trial registry: ClinicalTrials.gov; No.: NCT02497729; URL: www.clinicaltrials.gov.

Keywords: endotracheal intubation; hypoxemia; randomized trial.

Copyright © 2017 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Enrollment, randomization, intervention, and analysis.

Figure 2

A-C, Procedural outcomes by study group. Cormack-Lehane grade of glottic view (A), operator-reported difficulty of intubation (B), and the number of laryngoscopy attempts required for successful intubation (C) are displayed for patients assigned to the sniffing position (red) and the ramped position (blue).

Figure 3

Lowest arterial oxygen saturation by study group. The primary outcome of lowest arterial oxygen saturation between induction and 2 minutes after completion of endotracheal intubation (lowest oxygen saturation) is displayed for patients randomized to the sniffing position (circles) and the ramped position (squares). Horizontal bars represent median and interquartile range.

Figure 4

A, B, Heterogeneity of treatment effect. (A) The mean and 95% CI for the primary outcome of lowest arterial oxygen saturation is displayed relative to BMI for patients in each study group. (B) The mean difference in lowest arterial oxygen saturation (%) between the ramped position and the sniffing position is given for patients in prespecified subgroups present at the time of induction. Vertical bars represent the 95% CI around the mean difference. P values for the interaction between study group assignment and each variable were all > .10, except for oxygen saturation at the time of induction (P value for the interaction = .08). BiPAP = bilevel positive airway pressure; Fio2 in 6 hours prior = highest fraction of inspired oxygen in the 6 hours before intubation; MACOCHA = “Mallampati score III or IV, apnea syndrome (obstructive), cervical spine limitation, opening mouth < 3 cm, coma, hypoxia, anesthesiologist nontrained” score which predicts difficulty of endotracheal intubation in the ICU on a scale from 0 (easy) to 12 (very difficult). Values for the MACOCHA score were calculated immediately prior to induction for those patients randomized to a written preintubation checklist as part of the factorialized design; Spo2 in 6 hours prior = lowest noninvasively measured arterial oxygen saturation in the 6 hours before intubation.