MODIFIED LEMON AS A PREDICTOR OF DIFFICULT INTUBATION IN THE ED

Abstract

Background: Airway management is a critical component of emergency care, and difficult endotracheal intubation may increase the risk of repeated attempts and airway-related complications. The Modified LEMON score provides a structured bedside assessment of anatomical and clinical features associated with difficult intubation.

Objectives: To validate the Modified LEMON score for predicting difficult intubation in adult patients undergoing endotracheal intubation in the Emergency Department.

Study Design & Setting: Prospective observational study conducted in the Emergency Department of Combined Military Hospital from March 2024 to March 2025.

Methodology: A total of 150 adult patients aged >18 years requiring endotracheal intubation were included. The Modified LEMON score was assessed immediately before intubation and consisted of Look externally, Evaluate the 3-3-2 rule, Modified Mallampati, Obstruction, and Neck mobility. A score <3 was considered low risk and ≥3 was considered high risk. Difficult intubation was defined by the presence of at least one of the following: Cormack-Lehane Grade III/IV on initial direct laryngoscopy, ≥3 intubation attempts, rescue adjunct requirement following failed direct laryngoscopy, or change of operator after a failed attempt. Sensitivity, specificity, positive predictive value, negative predictive value, diagnostic accuracy, and ROC analysis were performed.

Results: A total of 150 patients were included, with a mean age of 41.88 ± 14.42 years and mean BMI of 26.10 ± 4.12 kg/m². Difficult intubation occurred in 31 (20.7%) patients, while 119 (79.3%) had easy intubation. Using a Modified LEMON score cutoff of ≥3, 76 (50.7%) patients were classified as high risk, including 28 (18.7%) with difficult and 48 (32.0%) with easy intubation. Among 74 (49.3%) patients classified as low risk (<3), 71 (47.3%) had easy and 3 (2.0%) had difficult intubation. The Modified LEMON score demonstrated a sensitivity of 90.3%, specificity of 59.7%, positive predictive value of 36.8%, negative predictive value of 95.9%, and overall diagnostic accuracy of 66.0% for predicting difficult intubation.

Conclusion: The Modified LEMON score demonstrated high sensitivity but modest specificity and diagnostic accuracy for predicting difficult intubation in the emergency department.