To the Editor:—
I read with interest the recent article by Adnet et al.1
wherein magnetic resonance imaging of eight awake subjects was used in an attempt to determine whether the “sniffing position” aligns the axes of the upper airway. The authors compared the neutral position to both simple extension and the sniffing position. Using the magnetic resonance images, axes were drawn through the mouth (MA), the pharynx (PA), and the larynx (LA). The angle between MA and PA was defined as α, that between PA and LA was defined as β, and δ was defined as the angle between the line of vision and LA. No subjects were anesthetized or paralyzed, and no laryngoscopies or tracheal intubations were performed.
The authors noted that angle δ was significantly greater in the neutral position than in the other two positions, demonstrating a disadvantage to the neutral position and an advantage that seemed to be equal for simple extension and the sniffing position. A larger study is necessary to determine whether the sniffing position is better than simple extension.
The authors did not note that the sum of α and β was numerically the lowest in the sniffing position. This indicates that the sniffing position does seem advantageous in aligning the axes.
Adnet et al.1
concluded, “Anatomic alignment of the LA, PA, and MA axes is impossible to achieve in any of the three positions tested.” This statement seems to contradict the fact that anesthesiologists perform laryngoscopies every day and are usually able to align these axes satisfactorily for visualization of the vocal cords and tracheal intubation. Moreover, it is obvious that simply placing a patient in the sniffing position or any other position does not automatically align the axes of the upper airway. Indeed, this is the reason that a laryngoscope is required for successful tracheal intubation. Therefore, perhaps a more important question for anesthesiologists is, Does the sniffing position facilitate laryngoscopy and tracheal intubation? This question is not addressed by this study.
I plan to continue positioning my patients in the sniffing position for tracheal intubation for four reasons: (1) the study of Adnet et al.1
shows a lower value of δ in the sniffing position than in the neutral position; (2) the sum of α and β is lowest in the sniffing position; (3) patients are generally more comfortable with a pillow under their head; and (4) this position has been successfully used for endotracheal intubation in a large number of cases.
It is also worth mentioning that in figure 1C, 1
the authors have not drawn axis PA correctly. This line does not contact the anterior portion of C2 as it is supposed to by their definition.
Mitchel B. Sosis, M.D., Ph.D.
1. Adnet F, Borron 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.