What is the most sensitive examination finding for predicting difficult endotracheal intubation (ETI)?

From the Guidelines

The most sensitive examination finding for predicting difficult endotracheal intubation (ETI) is the Mallampati classification, particularly class III or IV, as it has been identified as a key predictor in the MACOCHA score, a validated predictive score for difficult intubation 1. This assessment involves examining the visibility of oropharyngeal structures when a patient opens their mouth and protrudes their tongue without phonation.

• In Mallampati class III, only the soft palate and base of uvula are visible,
• while in class IV, only the hard palate is visible. To perform this evaluation properly, the patient should be seated upright, with their mouth maximally opened and tongue protruded without phonation. The examination should be conducted at eye level with the patient. Other important predictors that should be assessed include:
• thyromental distance less than 6 cm,
• limited neck extension (less than 35 degrees),
• reduced mouth opening (less than 3 cm),
• and presence of obstructive sleep apnea or obesity. No single predictor is perfect, so combining multiple assessments improves accuracy. The Mallampati classification works by revealing potential obstacles to visualizing the glottis during laryngoscopy - when posterior pharyngeal structures are poorly visualized in the awake patient, this often correlates with difficult visualization during intubation attempts, as supported by the development and validation of the MACOCHA score 1. It is essential to note that the MACOCHA score, which includes the Mallampati classification, has been shown to have a high discriminative ability for predicting difficult intubation, with a sensitivity of 76% and 73% in the original and validation cohorts, respectively 1. Therefore, the Mallampati classification, particularly class III or IV, should be considered the most sensitive examination finding for predicting difficult endotracheal intubation (ETI).

From the Research

Examination Findings for Predicting Difficult Endotracheal Intubation (ETI)

• The most sensitive examination finding for predicting difficult ETI varies across studies, but some common factors include:
  • Mouth opening: found to be one of the most sensitive criteria in a study by 2 with a sensitivity of 43%
  • Mallampati classification: found to have a sensitivity of 43% in a study by 3 and 35% in a study by 2
  • Sternomental distance: found to have the highest sensitivity of 76% in a study by 4
  • Neck circumference: found to have a sensitivity of 74% when the critical value is set to 35 cm and above in a study by 4
• Combination of tests:
  • A study by 2 found that combining tests did not improve the results
  • A study by 4 found that the combination of sternomental distance and neck circumference had a sensitivity of 62% and a positive predictive value of 42%
• Other factors associated with difficult intubation include:
  • Limited extension and flexion of the head and neck: found to have a high specificity of 99% in a study by 5
  • Micrognathia: found to be associated with difficult intubation in a study by 5
  • Limited mouth opening and teeth with anatomic abnormalities: found to be associated with difficult intubation in a study by 5
  • ULBT (class III): found to be a useful factor in predicting difficult intubation in a study by 6