Accuracy of Ratio of Height to Thyromental Distance in Predicting Difficult Visualization of Larynx

Authors

  • Pragya Shrestha Department of Anesthesiology, Shree Birendra Hospital, Kathmandu, Nepal.
  • Binita Acharya Departement of Anesthesiology, Tribhuvan University Teaching Hospital, Kathmandu, Nepal.
  • Priska Bastola Department of Cardiothoracic and Vascular Anesthesiology, Manmohan Cardiothoracic, Vascular and Transplant Centre, Kathmandu, Nepal.
  • Arjun Gurung Department of Cardiothoracic and Vascular Anesthesiology, Manmohan Cardiothoracic, Vascular and Transplant Centre, Kathmandu, Nepal.
  • Aashish Shah Department of Anesthesiology, Shree Birendra Hospital, Kathmandu, Nepal.

DOI:

https://doi.org/10.61122/jkistmc369

Keywords:

Difficult laryngoscopy, Height, Intubation, Larynx, Thyromental distance

Abstract

Introduction: Difficult laryngoscopy (DL) and intubation (DI) is a significant contributing cause in anaesthesia-related morbidity and mortality. To identify potentially difficult airways, number of anthropometric measurements have been recommended. This study is aimed to evaluate the accuracy of Ratio of Height to Thyromental Distance (RHTMD) to predict difficulty in the visualization of the larynx in patients undergoing elective surgery under general anaesthesia.

Methods: We conducted a prospective, observational study including 94 patients of ASA PS I and II patients scheduled for elective surgery requiring general anaesthesia with endotracheal intubation. Preoperatively, airway assessments were performed including TMD and RHTMD. During intubation CL grading of the patient was noted by attending anaesthesiologist. TMD, RHTMD, CL gradings and other parameters measured were analysed using R programming language. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of RHTMD in predicting the difficult visualization of larynx during intubation was assessed.

Results:The total incidence of difficult laryngoscopy, defined by CL III and IV was 5.3%, and sensitivity, specificity, PPV, NPV and accuracy of RHTMD were 40%, 98%, 50%, 97% & 94% respectively. In ROC the area under the curve (AUC) was 0.937, 95% CI 0.854-1.0 indicating high diagnostic accuracy in predicting difficult visualization of the larynx.

Conclusions:  RHTMD can be used as a bedside preoperative test for predicting difficult laryngoscopy with higher specificity, negative predictive value and accuracy.

 

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Published

2026-01-31

How to Cite

1.
Shrestha P, Acharya B, Bastola P, Gurung A, Shah A. Accuracy of Ratio of Height to Thyromental Distance in Predicting Difficult Visualization of Larynx. J. KIST Med. Col [Internet]. 2026 Jan. 31 [cited 2026 May 1];8(15):14-9. Available from: https://www.jkistmc.org.np/jkistmc/index.php/JKISTMC/article/view/369

Issue

Vol. 8 No. 15 (2026): Journal of KIST Medical College

Section

Original Article

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Copyright (c) 2026 Pragya Shrestha, Binita Acharya, Priska Bastola, Arjun Gurung, Aashish Shah

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