Digital imaging as an objective airway assessment: A pilot study measuring tongue and unoccupied area in the oral cavity in patients undergoing thyroid surgery

Abstract

Objective: The primary aim of our study was to develop an alternative airway exam to calculate the size and shape of the tongue, the unoccupied area of the oral cavity, and the ratio of unoccupied area to the entire oral cavity in patients with thyroid disease. A secondary aim was to compare the ratio of the unoccupied area of the oral cavity to the Mallampati classification.
Methodology: An IRB-approved prospective observational study was performed at Wake Forest Baptist Health in patients undergoing thyroid/parathyroid surgery who were 18 and older, and had an anticipated difficult airway indicated either by the physical exam, previous history, or planned use of a specialized airway device. Awake intubations or tracheostomies were excluded. Demographic data were collected including the airway exam (Mallampati classification, oral aperture, thyromental distance, neck range of motion) and a picture of the oral cavity with the tongue protruding was captured. Digital imaging analysis was performed with ImageJ to measure the area of the tongue, the unoccupied area of the oral cavity, and the entire oral cavity area. The ratio of unoccupied area to the entire oral cavity was calculated and correlated to the Mallampati classification.
Results: Eleven patients undergoing thyroid surgery were included in analysis. There was a wide variation in the size and shape of the tongue, leading to different unoccupied areas of the oral cavity and different ratios of unoccupied area to the entire oral cavity area. There was a negative correlation between Mallampati class and the ratio of unoccupied area (r = -0.696). Unoccupied area ratios < 18 were correlated with Mallampati III/IV while that > 36 were correlated with Mallampati I; the distinction between Mallampati I and II was harder to define.
Conclusion: We found that the ratio of unoccupied area to that of the entire oral cavity may be classified similarly to the Mallampati class and may quantify the distinction between Mallampatis I and III. The use of digital imaging to measure the size and shape of the tongue and the unoccupied area of the oral cavity may provide a quick and reliable alternative method to predict difficult intubation.
Citation: Bryan Y, Johnson KN, Krebs J, Leech P, Rosenthal S, Harris HM, Cannon J. Digital imaging as an objective airway assessment: A pilot study measuring tongue and unoccupied area in the oral cavity in patients undergoing thyroid surgery. Anaesth Pain & Intensive Care 2018;22(4):­­438-443
Received – 20 Sep 2018; Reviewed – 17 Nov 2018; Corrected & Accepted – 30 Nov 2018