2021 May 12. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–.
The airway is one of the most important components in the body to be protected regardless of why a patient is in a hospital, whether for outpatient surgery or admission to the intensive care unit (ICU) for observation and therapy. For this reason, when a physician considers intubation, they must evaluate the risk of failure to intubate and optimize variables for success. 1% to 3% of the patient population that requires endotracheal intubation has difficult airways. Recognizing these patients is crucial as it allows the clinician to prepare accordingly to minimize complications. The 3-3-2 rule is an assessment tool for the prediction of difficult intubations in the unexpected difficult airway.
According to the American Society of Anesthesiologists, intubation is determined to be difficult to secure when an appropriately trained and experienced anesthesiologist requires more than three attempts or longer than 10 minutes for successful endotracheal intubation. Similarly, ventilation is determined to be difficult when a trained clinician is unable to maintain an oxygen saturation of more than 90% when using a facemask for ventilation, and 100% fraction of inspired oxygen (FIO2) is in use for oxygenation.
The airway should be managed in a very time-sensitive way as poor oxygenation or ventilation can lead to hypoxia and hypercapnic abnormalities; this can be detrimental at the cellular level. Hypoxic brain injury can lead to permanent neuronal damage and acidosis due to hypoxia and hypercapnia, which together can lead to cardiac arrest or death.