Comparison of thyromental height test with ratio of height to thyromental distance, thyromental distance, and modified Mallampati test in predicting difficult laryngoscopy: A prospective study

Abstract

Background and Aims:Preoperative airway assessment to predict patients with difficult laryngoscopy is always crucial for anesthesiologists. Several predictive tests have been studied by various authors in quest of finding the best airway predictor. Recently, a new airway predictor, thyromental height test (TMHT) has been reported to have good predictive value in assessing difficult airway. We conducted this study with primary aim to evaluate the diagnostic accuracy of TMHT and to compare it with other established airway predictors, such as ratio of height to thyromental distance (RHTMD), thyromental distance (TMD), and modified Mallampati test (MMT) for predicting difficult laryngoscopy.Material and Methods:This prospective, observational study was conducted in 550 patients of either sex aged >18 years scheduled for elective surgery under general anesthesia. The patients’ airway was assessed preoperatively by two anesthetists. Standard anesthetic protocol was followed in all the patients. The laryngoscopic view was graded according to Cormack–Lehane scale. The receiver operating characteristic (ROC) curve was used to calculate the ideal cut off values for TMHT and RHTMD. Standard formulae were used to calculate validity indexes.Results:The incidence of difficult laryngoscopy was 10%. The cut-off value for TMHT and RHTMD were 5.1 cm and 19.5, respectively. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of TMHT were 78.18%, 93.94%, 58.90%, and 97.48%, respectively. The highest sensitivity, PPV, and NPV were observed with TMHT as compared with RHTMD, TMD, and MMT (P < 0.0001).Conclusions:TMHT is the best predictive test with highest accuracy and odds ratio for predicting difficult airway out of all predictive tests evaluated.

Development and validation of a difficult laryngoscopy prediction model using machine learning of neck circumference and thyromental height

“…These findings support that the NC and TMHT may be predictors of DL. Several studies showed promising results, even with a single predictor [4,[16][17][18][19][20][21][22]. However, the previous studies are different from those of ours.…”

“…AUROC and AUPRC, which evaluate the model's performance, showed the best performance in the model to which BRF was applied but did not show excellent In many studies, the NC has been associated with difficult airway intubation in obese patients [8,16,17]. Thyromental height has also been reported as a predictor of difficult airway management [4,[16][17][18][19][20]. These findings support that the NC and TMHT may be predictors of DL.…”

Use of the Thyromental Height Test for Prediction of Difficult Laryngoscopy: A Systematic Review and Meta-Analysis

“…As for the TMH measurement during preoperative assessment, 17 studies mentioned the use of either digital gauges (10 articles) [ 11 , 12 , 13 , 16 , 18 , 20 , 22 , 25 , 26 , 27 ] or regular rulers (7 articles) [ 14 , 15 , 17 , 19 , 23 , 24 , 33 ], while 6 studies failed to specify their measurement tools. Patients were placed in sniffing position for direct laryngoscopy and intubation in 14 studies [ 11 , 12 , 14 , 16 , 17 , 18 , 19 , 20 , 23 , 26 , 27 , 33 , 34 , 35 ].…”

“…As for the TMH measurement during preoperative assessment, 17 studies mentioned the use of either digital gauges (10 articles) [ 11 , 12 , 13 , 16 , 18 , 20 , 22 , 25 , 26 , 27 ] or regular rulers (7 articles) [ 14 , 15 , 17 , 19 , 23 , 24 , 33 ], while 6 studies failed to specify their measurement tools. Patients were placed in sniffing position for direct laryngoscopy and intubation in 14 studies [ 11 , 12 , 14 , 16 , 17 , 18 , 19 , 20 , 23 , 26 , 27 , 33 , 34 , 35 ]. During the direct laryngoscopy, a Macintosh blade was used in 17 studies in which one [ 31 ] used only size 3, 7 [ 12 , 16 , 17 , 18 , 20 , 23 , 26 ] used size 3 or 4, 2 [ 11 , 25 ] used only size 4, and 1 [ 13 ] used size 4 or 5.…”

“…In the original study of Etezadi et al [ 11 ], thyromental height (TMH) was defined as the height between the anterior border of the thyroid cartilage (on the thyroid notch just between the 2 thyroid laminae) and the anterior border of the mentum (on the mental protuberance of the mandible), with the patient lying supine with her/his mouth closed. Subsequently, several studies evaluated the actual performance of TMHT as a single predictor for DL in different populations [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. In 2021, moreover, Carvalho et al [ 21 ] performed a meta-analysis that included eight studies and showed that TMHT was a good predictor of DL with a better performance than most previously reported bedside airway assessment tests.…”