What Is the 3 3 2 Rule for Predicting Difficult Airways


Predicting difficult airways is key to successful intubation, and can minimize psychological and physical trauma to patients. Patients with difficult airways face higher morbidity and mortality rates because intubation may be delayed or even impossible. A simple mnemonic device can help you quickly assess a patient’s airway and respond appropriately. 


Predicting Difficult Airways with 3-3-2 

The 3-3-2 rule uses three simple assessments to predict the difficulty of intubating a patient:

  • 3 

    • You should be able to fit three fingers between the upper and lower teeth of a patient with an open mouth.
    • Ask the patient to open their mouth and place three fingers vertically between their incisors, or do it yourself.
    • If this is impossible, the narrow space may make it more difficult to visualize the glottis or insert the laryngoscope. 
  • 3

    •  An additional three fingers that fit between the tip of the mandible and the anterior neck helps estimate the size of the submandibular region.
    • A distance of less than three fingers suggests a narrower angle, which will make it more difficult to insert a tube. It also suggests that there is less space for the tongue next to the throat, potentially occluding the pharynx further. 
  • 2

    • Two fingers should fit between the base of the mandible and the thyroid notch on the anterior portion of the neck.
    • A larynx positioned too highly in the neck makes laryngoscopy more challenging because of the acute angle between the larynx and base of the tongue. It will also be more difficult, and maybe impossible, to see the larynx.

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Other Signs of a Difficult Airway

3-3-2 is just one standard for assessing difficult airways. Some other indicators that an airway may present challenges include:


  • Visual signs of malformations or blockages, such as a broken jaw or missing teeth 
  • A high Mallampati score 
  • Limited neck mobility 
  • Medical conditions that can obstruct the airway 
  • The patient is elderly or an infant or toddler 
  • The patient is pregnant 
  • Snoring 
  • Acute respiratory distress or pneumonia

Remember – the risk of aspiration is higher in patients with difficult airways, especially those with other obstructions or pneumonia. Pregnant women produce the hormone relaxin, which can relax the airway, increasing the risk of aspiration.


Other anatomical changes during pregnancy can make aspiration more dangerous in a pregnant person. The DuCanto Catheter safely delivers continuous suction, even when a patient is actively bleeding or vomiting, empowering you to efficiently treat aspiration episodes.


Managing Difficult Airways 

Identifying a potentially difficult airway is not enough. You must be prepared to deliver appropriate treatment without delay, even when an exam suggests that the airway may present significant obstacles.


Take your time, try different equipment, and keep the patient calm. It is important that agencies frequently conduct training for treating difficult airways, then drill first responders in scenarios that mimic the high-stress situations they encounter in real life.


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The Right Equipment Matters 

It doesn’t matter how skilled you are or how carefully you assess your patients. If you don’t have the right equipment, you can’t properly manage any airway, let alone one that’s difficult. Some suction machines lose suction over time.


Traditional wall-mounted suction is unavailable in emergencies, which means treatment delays as you transport the patient. Every agency needs a portable suction machine. For help choosing the right fit, download our free guide, The Ultimate Guide to Purchasing a Portable Emergency Suction Device.


Editor's Note: This blog was originally published in July 2022. It has been re-published with additional up-to-date content.