Clinical predictors of difficult laryngeal exposure

Purpose. Although difficult laryngeal exposure (DLE) is a common problem encountered after procedures using a rigid laryngoscope, to date, no anticipatory physical indicators have been formally noted as reliable predictors of DLE. The purpose of this paper is to identify useful and reliable indicators by which to predict, with acceptable accuracy, the occurrence of DLE following rigid laryngoscopy. Study design: Fifty-six patients, each of whom had undergone a rigid laryngoscope procedure, were classified as belonging to either the DLE group (n = 19) or the control group (n = 37) for purposes of this prospective study. Methods: All patients were given a physical examination, which encompassed the following nine measures: age, sex, modified Mallampati index (MMI), body mass index (BMI), hyoid-mental distance (HMD), thyroid-mental distance (TMD), thyroid-mandible angle (TMA), horizontal thyroid distance (HTD), and vertical thyroid distance (VTD). Stepwise regression was employed on patient data to identify those with DLE. Results: The ages of patients in the DLE group ranged from 35 to 79 years, with a mean of 51.3 years. Among the nine variables, we found sex (P = .045, odds ratio = 69.159) and TMA (P = .004, odds ratio = 1.510) to be "reliable" DLE predictors. Using these two variables, 94.6% of study case patients could have been correctly classified preoperatively. Based on our comparison of case results, we found that a TMA value greater than 120 degrees in men and 130 degrees in women indicates a strong likelihood of DLE. Conclusions: TMA is a sensitive, reliable, and useful predictor of DLE in both men and women. The combination of sex and TMA provide important initial clinical indicators that can alert a clinician regarding DLE probability.