Optimizing Head Positioning for Intubation
Source: Adnet F. Randomized study comparing the "sniffing position" with simple head extension for laryngoscopic views in elective surgery patients. Anesthesiology 2001;95: 836-841.
In this prospective, randomized study, the authors compared the ease of intubation in patients positioned in the sniffing position vs. simple head extension. Four hundred fifty-six patients were enrolled. Airway characteristics and total body mass were recorded in all participants. The sniffing position was obtained by placement of a 7-cm cushion under the head of the patient. The anesthetic procedure included two laryngoscopies without paralysis: the first was used for topical glottic anesthesia. During the second direct laryngoscopy, intubation of the trachea was performed. The head position was randomized as follows: group A was in the sniffing position during the first laryngoscopy and the extension position during the second; group B was in the extension position during the first laryngoscopy and the sniffing position during the second. Glottic exposure was assessed by the Cormack scale.
The sniffing position improved glottic exposure (decreased the Cormack grade) in 18% of patients and worsened it (increased the Cormack grade) in 11% of patients in comparison with simple extension. The Cormack grade distribution was not modified significantly between groups. Multivariate analysis showed that reduced neck mobility and obesity independently were related to improvement in laryngoscopic view with the application of the sniffing position.
Commentary by Michael A. Gibbs, MD, FACEP
The sniffing position has been widely recommended for decades to optimize glottic visualization during endotracheal intubation. This is the first study to test this assertion. The results are in keeping with a recent magnetic resonance imaging (MRI) study by the same authors, which demonstrated that the sniffing position did not improve alignment of the three airway axes (mouth axis, pharyngeal axis, and laryngeal axis) when compared with simple head extension. In fact, true anatomic alignment of all three axes was not possible in either position.1
So, what to do with the information? In the majority of patients with "normal" airway anatomy, intubation usually can be accomplished in either position without difficulty. If one doesn’t work, try the other. On the other hand, all obese patients and those with limited neck mobility (without known or suspected cervical spine injury) should be placed in the sniffing position prior to intubation. A very simple step will increase your chances of success and avoid unnecessary heartburn for you and the patient.
Reference
1. Adnet F. Study of the "sniffing position" by magnetic resonance imaging. Anesthesiology 2001;94:83-86.
Dr. Gibbs, Residency Program Director, Medical Director, Medcenter Air, Department of Emergency Medicine, Carolinas Medical Center, Charlotte, NC, is on the Editorial Board of Emergency Medicine Alert.
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