In Reply:—
We agree with Professor Benumof that the angle of flexion of the neck shown on the radiograph was not exactly 30–35° from the horizontal axis. This radiograph was obtained while the patient was in standard position for intubation, with a cushion under the head as routinely performed in our operating room. However, we are not sure that the angle was 5°, as stipulated by Professor Benumof. Professor Benumof stated that the sniffing position necessitates 30–35° of flexion of the neck axis on the chest. This was established by Horton et al. 1These angles were defined between (1) the neck axis (defined by two landmarks: anterior portion of the cricoid and the lowermost depth palpable in the sternal notch) and (2) the horizontal axis. 1Our radiography was performed with use of a portable X-ray machine; therefore, it is uncertain that the bottom of the radiograph corresponds to the horizontal axis. Moreover, because the two landmarks described by Horton et al. 1are not visible in the radiograph, it is difficult to measure the angle of the neck flexion. We also disagree with Professor Benumof in establishing a relation between the degree of neck flexion (or extension of the head) and the alignment of the oral, pharyngeal, and laryngeal axes. This relation has never been shown. The relation between angle of neck flexion (or head extension) and alignment of the three axes (oral, pharyngeal, and laryngeal) has never been investigated scientifically to our knowledge. The figure reproduced in the textbook by Benumof 2shows a patient in the sniffing position with the hard palate (i.e. , oral axis) in line with the trachea; this alignment is almost impossible to attain in a anatomically normal patient, whatever the angle of neck flexion. The most important point is that, in the classic article by Bannister et al. , 2this anatomic error was described because the figure is not true to the radiograph. Nevertheless, this figure has found its way into the anesthesiology literature.
We thank Dr. Hirsch and Dr. Smith for their interesting historical contribution. We can credit Dr. Kirstein as the first author who described atlantooccipal extension for direct laryngoscopy. However, Chevalier Jackson, in 1914, was the first who described clearly this maneuver for laryngoscopy to intubate a patient during anesthesia. The three-axis alignment theory was described not by Chevalier Jackson, but by Bannister in 1944. 3For the sake of completeness, the name “sniffing position” comes from the Magill 4article (in 1936) in which he described the optimal head position for laryngoscopy:
… The head itself is slightly extended on the atlas, so that the mandible is approximately at right angles to the table. When he wishes to sniff the air, a man in the normal erect posture instinctively and unconsciously takes this attitude … .
