Between 1 – 3% of patients who require endotracheal intubation have airways that make intubation difficult. Recognizing those patients who may have a difficult airway allows the paramedic to proceed with caution and to keep as many options open as possible. It also allows the paramedic to prepare additional equipment (such as the bougie and BIAD) that may not ordinarily be part of a standard airway kit.
The mnemonic LEMON is useful in evaluating patients for signs that may be consistent with a difficult airway and should raise the paramedic’s index of suspicion.
Evaluating for the difficult airway (LEMON)
- External indicators of either difficult intubation or difficult ventilation include: presence of a beard or mustache, abnormal facial shape, edentulous mouth, facial trauma, obesity, large front teeth or “buck teeth”, high arching palate, receding mandible, short bull neck.
Evaluate 3-3-2 Rule
- 3 fingers between the patient’s teeth (patient’s mouth should open adequately to permit three fingers to be placed between the upper and lower teeth)
- 3 fingers between the tip of the jaw and the beginning of the neck (under the chin)
- 2 fingers between the thyroid notch and the floor of the mandible (top of the neck)
- Besides the obvious difficulty if the airway is obstructed with a foreign body, the paramedic should also consider other obstructer's such as tumor, abscess, epiglottis, or expanding hematoma.
- Ask the patient to place their chin on their chest and to tilt their head backward as far as possible. Obviously, this will not be possible in the immobilized trauma patient.