- Neck Range of Motion: Ask patient to assume sniffing position (cervical flexion and atlanto-occipital extension), the position they will be in while being intubated. Normal patients should achieve 35 degrees or more of extension without pain, tingling or numbness.
- TMJ mobility and degree of mouth opening: Required to determine adequacy of space for manipulating laryngoscope.
- Measure Inter-incisor distance (<2 finger breadths = difficult intubation predicted).
Upper lip bite test: Ask patient to move lower incisors as high on the upper lip as possible (if lower teeth do not reach vermilion of upper lip, sign of inadequate TMJ movement).
Dentition: Note the presence of dentures, poor dentition, loose teeth or caps, which may not tolerate digital manipulation or be at risk of damage when the laryngoscope blade is inserted. Patients with large incisors are difficult to intubate. Edentulous patients are easier to intubate but difficult to ventilate.
Tongue/Oropharynx: * Direct laryngoscopy allows visualization of the larynx by displacing the tongue anteriorly into the mandibular space, which moves the tongue out of the line of sight. A normal sized tongue will generally fit easily into the space between the two mandibular rami. However, if the tongue is too large (macroglossia) or the mandible is too small (micrognathia), there will likely be difficulty with proper visualization of the glottis.
Mallampati score: A measure of how large the tongue is in relation to the oropharynx. Ask patient to open their mouth wide and stick out their tongue as far as it will go (Do not ask them to say "aah"). Grade the airway based on the illustration below. Grade 3 or 4 is associated with difficult laryngoscopy.
- Thyromental Distance: Assesses the size of the mandible. Distance from the mandible mentum to the thyroid cartilate. Difficult intubation if thyromental distance < 3 finger breadths.
The American Society of Anesthesiologists (ASA) Classification should be recalculated. A table to calculate the ASA score is given below: