To the Editor:—
Recently, residents in our program have told me that they read about the “sniffing position” being an anatomic myth and of little clinical use. 1
Being a clinician who strongly advocates the sniffing position, I examined the article by Dr. Adnet et al.1
to find out whether there is substance to this apparent revelation.
In their article, Dr. Adnet et al.1
study the x-ray anatomy of the upper airway. The axial alignment of the mouth, the pharynx, and the larynx is measured with the head in the neutral position, in simple head extension, and in the sniffing position. The authors find no alignment of the axis of the hard palate, the upper cervical spine, the visual axis (upper incisors to posterior cricoid cartilage), and the laryngeal axis in the sniffing position and call the superiority of the sniffing position over simple head extension into question.
The most problematic part of this study is the definition of the laryngeal axis, defined as “a straight line passing through the centers of the inferior (cricoid cartilage) and superior (base of epiglottis) orifices.” This definition is not an accepted standard, highly dependent on the acquisition of an exactly median-sagittal magnetic resonance image slice and the comparison of identical anatomic landmarks. The authors have published a figure that underscores my point of criticism as follows: the diameter of the “superior orifice” in the sagittal image of the subject in simple head extension connects what seems to be the superior aspect of the cricoid cartilage (posterior) to the inferior aspect of the thyroid cartilage (anterior). However, in the sagittal image of the subject in the sniffing position, the same line connects the cricoid cartilage with the center, rather than the inferior aspect of the thyroid cartilage. Thus, the course of the laryngeal axis is altered and deviates to a larger degree with the visual axis. This modification happens to substantiate the authors’ point. In fact, almost all significant findings are related to the position of this poorly defined “laryngeal axis.” Three-dimensional reconstruction of the larynx might have been superior to define the laryngeal axis with a higher degree of accuracy.
I am also not convinced that the authors studied the sniffing position in all subjects. The heads of all subjects were uniformly elevated by 7 cm. Whether this degree of head elevation (cervical protrusion) is optimal for all subjects remains unanswered. In this context, it might have been helpful to correlate the degree of head elevation with cervical length or simply patient height, a parameter that unfortunately was not disclosed.
Based on these considerations, I am not convinced that Dr. Adnet et al.1
have made a case good enough to challenge the clinical usefulness of the sniffing position. My bias is that the sniffing position facilitates the anterior displacement of the tongue and submental tissues and thus frees up visualization of the glottis—the most clinically relevant axis.
Michael A. Froelich, M.D., D.E.A.A.
1. Adnet F, Borrow SW, Dumas JL, Lapostolle F, Cupa M, Lapandry C: Study of the “sniffing position” by magnetic resonance imaging. A nesthesiology 2001; 94: 83–6
© 2001 American Society of Anesthesiologists, Inc.