Ethnicity and upper airway measurements: A study in South Indian population

BACKGROUND AND AIMS: Most studies on upper airway are conducted based on airway measurements in the western population. We set out to find the normal values of upper airway measurements in South Indian population. The aim of this study was to perform various upper airway examinations and to set standards for normal measurements in the South Indian population as well as to analyse the data for predictors of difficult intubation. METHODS: This prospective observational study was conducted in a tertiary cancer hospital in Southern India. Airway assessment parameters, including modified Mallampati classification (MPC), upper lip bite test (ULBT), sternomental distance, thyromental distance (TMD), and the inter-incisor distance were documented for 2004 patients meeting the inclusion criteria. Laryngoscopic view after induction was graded as per Cormack and Lehane's (CL) classification. Any CL ≥3 was considered to be difficult laryngoscopy. The collected data (2004 cases) was analyed with SPSS software version 17. Receiver operating characteristics (ROC) curve was used to determine cut-offs in the population. Sensitivity, specificity, positive and negative predictive value were computed. RESULTS: MPC, ULBT, and ratio of height to TMD (RHTMD) predicted difficult intubation with sensitivity of 40.86%, 45.53% and 64.60%, respectively and these were statistically significant with P < 0.001. Using the area under the curve of the ROC curve and discrimination analysis normal RHTMD in our population had a cut off value of 17.1. CONCLUSION: The cut off value for RHTMD to predict difficult laryngoscopy in the South Indian population is 17.1.