A comparison of Mallampati classification, thyromental distance and a combination of both to predict difficult intubation

Abstract

Background and Objective: Failed intubation is an important cause of anesthetic related mortality. The purpose of this study was to determine the ability to predict difficult visualization of the larynx from the preoperative tests, either Mallampati classification (MPC) and thyromental distance (TMD) alone or in combination.
Methodology: The cross-sectional study was conducted at the main operation theatre of Liaquat National Medical Hospital and Medical College Karachi from September 2012 to April 2013 after an approval from hospital ethics committee and a written informed consent was obtained, 501 patients meeting the inclusion criteria for a non-emergency elective surgery under general anesthesia requiring tracheal intubation were included in the study. We assessed the two preoperative tests, e.g. MPC and TMD, either alone or combined. Data were collected after induction, laryngoscopy and grading was performed (as per Cormack-Lehane classification). Sensitivity and positive predictive value (PPV) for each test alone and in combination were determined.
Results: Difficult laryngoscopy (Grade 3 or 4) occurred in 55 patients (11%). Used alone MPC and TMDs were associated with poor sensitivity specificity, PPV: Negative predictive value combining Mallampati with TMD – sensitivity decreases but specificity and PPV increases.
Conclusion: Our study shows that a combination of MPC and TMD is preferable for assessment of the airway because of its better specificity and positive predictive value than MPC, TMD alone, but the tests alone or in combination have low sensitivity. 
Citation: Mallhi AI, Abbas N, Naqvi SMN, Murtaza G, Rafique M, Alam SS. A comparison of Mallampati classification, thyromental distance and a combination of both to predict difficult intubation. Anaesth Pain & Intensive Care 2018;22(4):­­468-473
Abbreviations used: MPC-Mallampati classification; TMD-Thyromental distance; SMD-Sternomental distance; MMT-Modified Mallampati test; HLM-Horizontal length of the mandible; C-L-Cormack and Lehane classification; TP-True Positive; FP-False Positive; TN-True Negative; FN-False Negative; PPV-Positive predictive value; NPV-Negative predictive value  
Received: 8 Mar 2018, Reviewed: 23, 27 May 2018, Corrected: 18 Jul 2018, Accepted: 31 Aug 2018