Difficult Laryngeal Exposure in Microlaryngoscopy: Can it be Predicted Preoperatively?

Abstract

The aim of the present study was to identify preoperative clinical predictors for difficult laryngeal exposure (DLE) and to define a simple grading system for laryngeal exposure. This is a prospective descriptive study carried out in a tertiary teaching hospital in South India. Patients above 18 years undergoing microlaryngoscopy had presurgical evaluation of 11 physical parameters. Grading of Modified Cormack-Lehane Score (MCLS) and rigid laryngoscopy were done during procedure. On logistic regression analysis, with a 95 % confidence interval (CI) MCLS was found to be a statistically significant predictor (odds ratio 12). With 90 % CI, neck circumference, atlanto-occipital extension and MCLS were significant (odds ratio of 4, 4, 12 respectively). Neck circumference of more than 34.25 cm and limited atlanto-occipital extension of less than 19.50, predicts difficult laryngeal exposure. A simple grading system for laryngeal exposure during microlaryngoscopy is being proposed. MCLS grade more than 2a done intra operatively correlates well with difficult intubation.

Prediction of difficulty in direct laryngoscopy

“…For Pinar et al, this correlation was found with measurement of the HMD and SMD in the full extension position, which are related to the degree of retrognathia and length of the neck 8 . However, in other studies, those measures were not good predictors for DLE 9 , 15 .…”

“…Hekiert et al 14 proposed a visual analog score (VAS) of 1 to 10 assessed by the laryngologist, with 1 being the least difficult and 10 being the most difficult. However, although this definition varies according to the authors, the majority agree that exposure limited to the posterior third or less of the vocal cord defines DLE 9 , 12 , 13 , 15 . We applied the protocol proposed by Hsiung, which consists of evaluating laryngeal exposure after putting the patient in the sniffing position, external counterpressure and changing to a smaller laryngoscope if the exposure is not complete 9 .…”

“…Factors leading to difficult intubation are intricately related to those leading to difficult exposure during suspension laryngoscopy. Thus, it is usually believed that patients who are difficult to intubate are considered likely DLE candidates 8 , 12 , 15 . Likewise, a high Mallampati grade can predict high Cormack–Lehane scores and, consequently, DLE 8 , 9 , 15 .…”

“…Thus, it is usually believed that patients who are difficult to intubate are considered likely DLE candidates 8 , 12 , 15 . Likewise, a high Mallampati grade can predict high Cormack–Lehane scores and, consequently, DLE 8 , 9 , 15 . This was confirmed in this study since we found a strong correlation between high Mallampati and Cormack scores and DLE.…”

“…They found that a flexion–extension degree less than 90° was significantly correlated with DLE. Paul et al 15 measured the atlanto-occipital extension degree and found that it was a good predictor of DLE if less than 19.5° (p: 0.001).…”