Head elevating device and cricothyroid membrane position in pregnant women with obesity class 3: an observational study

Abstract

Background: Obesity and pregnancy are risk factors for difficult intubation. A head-elevating positioning device increases functional residual capacity and improves direct laryngoscopy. It is unclear what effect such device has on the airway anatomy. The primary aim of this study was to determine the change in distance from the sternal notch to the cricothyroid membrane (CTM) mid-point among pregnant women with class 3 obesity, comparing the supine positioning and the head-elevated position.

Methods: In this prospective observational study, 50 pregnant women with class 3 obesity provided their consent for participation, and airway anatomy was assessed with ultrasound when presenting either for elective cesarean delivery or in early stages of labor. The CTM's depth and height were measured in supine (Time 1) and head-elevated (Time 2) positions. The CTM midpoint was established and the distance from this point to the sternal notch was obtained. The primary outcome was change in distance from sternal notch to CTM midpoint. Secondary outcomes included changes in CTM depth and height.

Results: The median (± standard deviation) sternal notch to CTM midpoint distance increased significantly from 41.07 mm (± 8.35 at Time 1 to 45.40 mm ± 8.97) at Time 2 (mean difference 4.33 mm, 95% CI 3.06 to 5.61, P <0.0001). No differences were observed in CTM depth (mean difference -0.15 mm, P =0.66) or height (mean difference 0.34 mm, P =0.20).

Conclusion: Head elevation increased the distance from the sternal notch to the CTM midpoint but did not affect CTM depth or height in pregnant women with class 3 obesity. Further research is needed to assess neck ultrasound anatomy in high-risk patients for difficult intubation.

Keywords: Airway management; Cricothyroid membrane; Head-elevating positioning device; Ultrasound.