The “Ear-Sternal Notch” Line—How Should You Lie?
Sinha et al1 recommend that the scale-ampule assembly be used to align the ear with the sternal notch in an imaginary line parallel to the ground. The basis for this imaginary line is to achieve the “sniffing position,” in so far as the “optimal positioning of the head and neck in the sniffing position is governed by the ability to flex the lower cervical spine and extend the occipito-atlanto-axial complex.”2 Levitan et al3 describe the head-elevated laryngoscopy position (Figure, A) and refer to excellent illustrations by Jackson in 1934 to describe the correct method for the elevation of the head to achieve the neck flexion of the sniffing position.
A crucial point of confusion is the term “ramping.” Ramping has been used to denote elevating only the very upper torso to include more flexion and rounding of the very upper thoracic spine to achieve head elevation in the otherwise supine patient. In a much-quoted study, Collins et al4 “ramped” their obese patients by placing blankets mostly under their patients’ heads to achieve what appears to be a “sniffing position,” as demonstrated by their representative photograph (group 2). In contrast, in the other arm of Collins et al’s4 study, the obese patients supposedly placed in the “sniff” position had a 1-size-fits-all 7-cm pillow, which, as judged by their representative photograph, in no way achieved the “sniffing position” (group 1). Unsurprisingly, they found that the ramped patients in the “true” sniffing position (group 2) achieved 88% grade 1 views as opposed to 66% of patients in group 1.
Alternatively, “ramping” can refer to angling up the whole torso in a semisitting position. This was the case in Semler et al’s5 randomized trial of the ramped position (25° whole-torso sitting position) (Figure, B) versus sniffing position during intubation of critically ill patients.4 The method for positioning the ramped patients’ head and neck, in effect, utilized an imaginary line parallel to the ground connecting the ear and the sternal notch.
While maintaining the line connecting the ear to the sternal notch parallel to the ground, the more the patient is sitting up with their whole torso ramped, the more neck extension will result; the very opposite of the desired neck flexion. Indeed, the anti-intubation nature of maintaining this parallel line in Semler et al’s5 “ramped” patients was confirmed by the finding that 20.8% of glottic views in the study were Cormick and Lehane grade 3 and 4.6% were grade 4. Figure C demonstrates what should be an appropriate angle of the imaginary line crossing the ear and sternal notch if a patient is “ramped” as defined by Semler et al.
How to position a patient for intubation is at the very core of airway management. Yet, there seems to be significant confusion regarding terminology, thus leading to polar opposite beliefs in what the optimum position should be. This confusion needs to be highlighted and a discussion had. Concerningly, medical websites6,7 devoted to teaching practitioners successful intubation are advocating the anti-intubation position of Semler et al, in the context of a misunderstanding of the imaginary parallel line.