Upper lip bite test as a predictor of difficult mask ventilation: a prospective study.

BACKGROUND Oxygenation and ventilation by means of bag-mask and ambubag play a significant role in maintaining an optimal oxygen saturation of blood and hence the essence of life itself. Predicting difficulty in mask ventilation is again of paramount importance at the time of induction of anesthesia, and in emergency situations. In this study we aimed at evaluating factors that could help in predicting the difficulty of bag-mask ventilation. METHODS In a prospective study, 200 patients were allocated into two groups, 100 each. First group with a ULBT class I, and the other group with ULBT class II and III. Factors such as height, weight, gender, past history of snoring, neck circumference, Mallampati class, sternomental and thyromental distances were then evaluated in each of the patients in the two groups in order to arrive at their impact on the incidence of difficult mask ventilation. Data were analyzed using Chi-square, student t-test and Fisher's exact tests depending upon the situation. A p < 0.05 was considered to be statistically significant. RESULTS The results revealed that negative predictive value (NPV) of ULBT class, history of snoring and neck circumference were 86%, 83%, 81%, respectively. A combination of these three predictors had an NPV of 95%. CONCLUSION ULBT class alone was of value in predicting difficulty in mask ventilation, but a combination of the three tests significantly improved the predictive value.