Is the “Sniffing Position” Essential for Orotracheal Intubation?Adnet et al.(page 83)

Eight healthy volunteers were recruited for a study by Adnet et al.  designed to test the conventional wisdom of the superiority of the so-called sniffing position for successful orotracheal intubation. The rationale given for using this position (neck in flexion, face extended, pillow under neck) is that the oral, pharyngeal, and laryngeal axes align. Accordingly, the researchers performed magnetic resonance imaging with the volunteers’ heads in neutral position, in simple extension, and in the sniffing position. All scans were interpreted by a radiologist who was blinded to the aims of the study. On each scan, the following measurements were performed: the axis of the mouth (defined as a straight line drawn parallel to the hard palate), the pharyngeal axis (a line passing through the anterior portion of the atlas and C2), the laryngeal axis (a straight line passing through the centers of the inferior and superior orifices), and the line of vision (a straight line passing through the inferior extremity of the superior incisors and posterior extremity of the superior portion of the cricoid cartilage).

What the researchers found is that anatomic alignment of the laryngeal, pharyngeal, and mouth axes is impossible to achieve in any of the three positions tested. Although the study was limited by inability to examine volunteers with a laryngoscope blade in place, the results do not support the widely held assumption that the sniffing position improves anatomic alignment of the three important axes in laryngoscopy. Definite answers to the question of whether simple head extension or the sniffing position provides the best alignment might be provided by a prospective, randomized trial of the two methods.