Ultrasound guided airway assessment- an observational study to correlate airway parameter to cormack-lehane grading of laryngoscopy

Abstract

Securing airway is an important routine for any Anesthesiologist. Assessment of airway preoperatively is an essential part of predicting difficulty in airway management. Mallampati test (MP) is commonly applied during such preoperative assessments. However, Mallampati test is an indirect clinical sign in which thickness of the base of the tongue is assessed by whether it masks faucial pillar (palatoglossal and palatopharyngeal arches) or not. Though MP is an indirect assessment, this test is routinely applied because of ease of applying this test. This test however is not completely reliable in predicting difficulty in laryngoscopy and intubation and has high false-positive and false-negative outcome. The depth of floor of the mouth and thickness of tongue can be assessed to improve prediction of difficult airway. This depth can be measured by cheap and rapid test using ultrasonography. Material and Methods: In this study depth of the tissues in the floor of the mouth were measured by placing USG probe above hyoid bone in sagittal plane and measurement taken from skin to mucous membrane of tongue and attempted to establish any relationship between this thickness and difficulty in laryngoscopy as assessed by Cormack-Lehanne scoring. 60 ASA I & II patients undergoing elective surgeries under GA were assessed during the pre-anaesthetic evaluation and supra-hyoid USG depth in sagittal plane was measured and recorded. During laryngoscopy Cormack and Lehanne scoring was recorded for each of the subjects by 2 experienced anaesthesiologists who were blinded to the depth assessment.