Introduction: Difficult intubation is an emergency situation that an anaesthetist come across frequently. It is a frequent cause of mortality in practice of anesthesia. Mallampati classification (MPC) of the oropharyngeal structures is a simple test to assess anticipated difficult airway for endotracheal intubation. thyromental height (TMH) test is now also commonly used to predict difficult intubation. Objective: To evaluate diagnostic accuracy of modified mallampati classification and thyromental height using Cormack and Lehane's classification of laryngoscopy as a gold standard. Study Design: Descriptive cross sectional validation study. Setting: Department of Anaesthesia, Benazir Bhutto Hospital, Rawalpindi. Duration: 20-Sep-2021 to 19-Mar-2022. Material and Methods: A total number of 1035 were included in this study. Pre-operatively modified Mallampati test (MMT) and TMH test was performed. Mallampati class III and IV were considered difficult. While TMH height >50 mm was considered as difficult intubation. Difficult intubation equipment’s was ready, i.e. stylet, boogie, LMA, I-gel. General anaesthesia was induced in the operating room after collecting baseline vital signs. After three minutes, a skilled anesthesiologist performed a laryngoscopy while the patient was sniffing. To validate the diagnosis of difficult intubation, the laryngeal view was appraised using a modified Cormack and Lehane (C-L) grading system. Results: Mean age of patients was 40.16±12.19 years. Mean height of patients was 152.94±8.32 cm, mean weight was 65.01±13.59 Kg and Mean body mass index (BMI) was 27.78±5.64 kg/m2. There were 768 (74.20%) males and 267 (25.80%) females. TMH was 77.8% sensitive, 94.6% specific having 70.0% PPV, 96.3% NPV and 92.27% accuracy. On diagnostic accuracy of MMP taking difficult intubation according to standard as gold standard, MMP was 92.4% sensitive, 90.1% specific having 60.2% PPV, 98.6% NPV and 90.3% accuracy. Practical implications: Thyromental Height (TMH) needs more broad usage in multiple settings to be validated as a single most important predictor of difficult laryngoscopy. It will thus be used widely all over the country rendering fewer complications for the patients. Conclusion: TMH was the test that was most sensitive and accurate at foretelling difficult laryngoscopy when compared to the modified Mallampati score. TMH has potential as a single anatomical metric to predict the possibility of a difficult laryngoscopy. Keywords: Mallampati classification, thyromental height, Cormack and Lehane's classification, laryngoscopy.

Background: To keep the airway open, a flexible plastic tube (ETT) is inserted into the trachea during tracheal intubation. Even when done correctly, tracheal intubation requires much clinical experience, and catastrophic problems can occur. Mandibular space has been estimated using hyomental distance (HMD), although HMD has only been found to provide a limited amount of diagnostic accuracy on its own. In order to determine how well the Hyomental Distance Ratio (HMDR) predicts difficult laryngoscopy, we conducted this study. Objectives: Using the Cormack and Lehane classification as the gold standard, the objective is to assess the diagnostic validity of the Hyomental Distance Ratio (HMDR) for the prediction of challenging laryngoscopy in patients undergoing surgery under general anaesthesia. Materials & Methods: The department of anesthesiology and the general surgery operating rooms at Sir Ganga Ram Hospital in Lahore conducted this cross-sectional study over the course of six months in 2015–2016. The approach of non-probability purposive sampling was applied. Informed consent was acquired, and patient demographics were recorded. The researcher herself then assessed patients for HDMR. In order to determine if a patient had a difficult or normal laryngoscopy, HDMR was determined. After that, the researcher performed a laryngoscopy on the patients. If the vocal cords were visible, the mouth was opened, and the case was assessed using the Cormack and Lehane classification (CL), with easy or difficult laryngoscopy being designated. SPSS version 20 was used to enter and analyse all of the data. Results: The patients in our study had a mean age of 43.23 11.63 years and a male to female ratio of 1.5:1. In this study, 43.91% of patients had an HDR difficult intubation. HDR's difficult intubation has a sensitivity of 95.05%, a specificity of 96.12%, and a diagnostic accuracy of 95.65% when using CL as the gold standard. Practical Implication: According to this study, this strategy can be applied accurately in other hospitals. Government should establish guidelines for using the most trustworthy techniques as the benchmark in healthcare settings. Conclusion: According to the findings of our study, the HMDR is a viable diagnostic tool for anticipating challenging laryngoscopy in patients having general anaesthesia with tracheal intubation. According to this study, this strategy can be applied accurately in other hospitals. Government should establish guidelines for using the most trustworthy techniques as the benchmark in healthcare settings. Keywords: Laryngoscopy, difficult intubation, Cormack Classification, difficult surgery