Introduction
In emergency medical situations, securing the airway is a critical task that can determine a patient’s outcome. A failed intubation can lead to severe complications or death, making pre-intubation assessment a vital skill for all healthcare providers. The LEMON Law is a systematic and reliable approach designed to identify potentially difficult airways before intubation begins.
What is the LEMON Law?
The LEMON Law is an acronym used in emergency medicine to assess the likelihood of a difficult airway. Each letter stands for a specific assessment component:
- L – Look externally
- E – Evaluate the 3-3-2 rule
- M – Mallampati score
- O – Obstruction
- N – Neck mobility
These five steps form a comprehensive and rapid evaluation process that can be performed at the bedside, helping practitioners anticipate challenges and plan accordingly.
Detailed Breakdown of the LEMON Assessment
Look Externally
External examination can provide immediate clues. A patient with a large tongue, recessed chin, facial trauma, swelling, thick neck, or obesity may present challenges. These anatomical features can hinder both the insertion and visualization during laryngoscopy.
Evaluate the 3-3-2 Rule
This rule assesses the space available for intubation:
- 3 fingers – The patient should be able to open their mouth three finger-widths.
- 3 fingers – The distance from the mentum (chin) to the hyoid bone should be three finger-widths.
- 2 fingers – The distance from the hyoid bone to the thyroid notch should be two finger-widths.
Deviations from these norms can indicate a reduced field and a higher risk of difficulty.
Mallampati Score
This score is derived from visualizing the anatomy within the oral cavity. Patients are asked to sit upright, open their mouth, and protrude their tongue:
- Class I: Full visibility of tonsils, uvula, and soft palate
- Class II-III: Partial visibility
- Class IV: Only the hard palate visible
A higher class correlates with greater intubation difficulty.
Obstruction
Check for signs of physical blockage that could impair airway management. Blood, vomit, facial trauma, tumors, infections, or foreign bodies can all compromise both visibility and passage.
Neck Mobility
The ability to align airway axes is crucial for successful intubation. Patients should be able to assume the sniffing position (neck flexed, head extended). Conditions such as cervical spine immobilization, arthritis, or obesity may reduce mobility, complicating the procedure.
Clinical Application
A trauma patient arrived with facial swelling, limited mouth opening, uncooperative for Mallampati scoring, and blood in the airway. His neck was immobilized due to spinal precautions. Using the LEMON assessment, four out of five criteria indicated a difficult airway. The team switched to video laryngoscopy, employed a bougie, and prepared a surgical airway kit—resulting in a successful first-pass intubation.
Conclusion
The LEMON Law is not just a mnemonic—it is a practical and effective framework that enhances clinical judgment and patient safety. By integrating this assessment into routine pre-intubation protocols, healthcare providers can significantly improve outcomes, reduce the risk of complications, and ensure preparedness in high-stakes scenarios.
Recommended Resources
- American Society of Anesthesiologists – Difficult Airway Algorithm
- Manual of Emergency Airway Management, Ron Walls
- YouTube Video: LEMON Law for Intubation
- NEJM: Airway Management in the Emergency Department
- EMCrit – Airway Strategy Planning
Stay informed, stay prepared, and remember—every second counts in airway management.
