A Prospective Study to Correlate Difficult Intubation with Difficult Laryngeal Exposure for Microlaryngeal Surgery using Various Grading Scales of Difficult Intubation.

ABSTRACT

Adequate visualization of the vocal folds is essential for optimal phonosurgery. Pre-operative knowledge of a difficult laryngeal exposure (DLE) can alert the surgeon regarding the need for alternative measures. Our study is based on the hypothesis that a patient who has difficult intubation (DI) is likely to have DLE, thus scales anticipating DI should also anticipate DLE. Our aims were to correlate patients of actual DI on table with patients who had DLE, secondly to assess the ability of grading scales of DI to predict DLE and finally to obtain a cut-off value of neck circumference and length for predicting DLE. This is a prospective, observational study wherein four grading scales; Modified Mallampati Classification (MMC), 3-3-2, Upper lip bite test (ULBT) and Neck Mobility (NM) were used for anticipating DI and correlated with DLE during MLS. Occurrence of actual DI and DLE was correlated. Neck circumference and neck length was correlated with incidence of DLE. Out of 42 patients, 22 were anticipated to have DI (52.38%). Actual incidence of DI was 6 (14.28%) and DLE was 10 (23.80%). Correlation between actual DI and DLE was statistically significant. Of the 4 grading scales, ULBT was significant in predicting DLE. Neck circumference more than 37.5 cm and neck length less than 15.3 cm was significant in anticipating DLE. There is a significant correlation between DI and DLE. A positive ULBT, neck circumference more than 37.5 cms and neck length less than 15.3 cms are independently suggestive of a DLE.