Background: Modified Mallampati test is a standard method of assessing the airway for predicting potentially difficult laryngoscopy and intubation. It is performed in sitting position, while intubation is done in supine position. It is unclear whether a change in position while assessment of the Mallampati class causes significant changes in prediction of a difficult airway, and if it does, then whether we need to change our guidelines currently in place.
Materials and methods: This prospective study was conducted in 350, ASA I and II patients undergoing various routine surgical procedures under general anesthesia, over a period of 18 months. The airway assessment was done using modified Mallampati grade in sitting and supine positions. Mallampati grade of III or IV was defined as the predictor of difficult airway. The laryngoscopy grade was assessed using the Cormack and Lehane grading scale. Grade III or IV of Cormack and Lehane grades was defined as the difficult laryngoscopy and assumed as the predictor of difficult intubation. Statistical measures including sensitivity, specificity, positive and negative predictive values, and accuracy were used for comparing the two positions for predicting difficult or ease of intubation.
Results: Out of 350 patients, Mallampati grade III or IV was observed in more patients in a supine position compared to sitting position (12.29 vs 4.57%). Difficult laryngoscopy was observed in 23 (6.57%) patients. Sensitivity of modified Mallampati test was comparable in both the positions (sitting 97.55 vs supine 92.66%). Specificity was better in supine position as compared to sitting, 65.22 and 34.78%, respectively. Positive predictive value for difficult intubation in sitting position and supine positions were 95.5 and 97.43%, respectively, while negative predictive values were 50 and 38.46%. The diagnostic accuracy in both positions was comparable; sitting 93.43% and supine position 90.86%. The kappa agreement was 0.377 for sitting position and 0.437 for supine position, hence shows a fair agreement for both the sitting and supine positions in the prediction of difficult intubation.
Conclusion: There was no statistically significant difference between airway assessment conducted in sitting and supine positions. The modified Mallampati classification (MMC) in supine position can be used to predict difficult tracheal intubation with comparable efficacy as in the sitting position.