Selecting an Appropriately Sized Oropharyngeal Airway
The most reliable method for selecting an appropriately sized oropharyngeal airway (OPA) is to measure the distance from the patient's maxillary incisors (or corner of the mouth) to the angle of the mandible, with the maxillary incisors-to-angle measurement providing superior ventilation outcomes. 1, 2
Recommended Measurement Technique
Measure from the maxillary incisors to the angle of the mandible as this technique consistently provides:
- Clear manual ventilation in 100% of patients 2
- Adequate mechanical ventilation in 100% of patients 2
- No complete tongue obstruction on endoscopic evaluation 2
The alternative measurement from the corner of the mouth to the angle of the mandible is less reliable, resulting in:
- Partially obstructed ventilation in 6% of patients 2
- Inadequate mechanical ventilation in 7% of patients 2
- Complete tongue obstruction in 40% of patients on endoscopy 2
Size Selection by Sex
When using standardized sizing, the following provides optimal ventilation with acceptable endoscopic positioning:
- Men: Size 9 OPA provides clear manual and adequate mechanical ventilation without causing epiglottic trauma 3
- Women: Size 8 OPA provides clear manual and adequate mechanical ventilation without causing epiglottic trauma 3
Sizes 7 and smaller cause tongue obstruction, while sizes 10-11 risk touching or passing beyond the epiglottis tip 3
Critical Caveats
Avoid measurement techniques using the little finger or anterior nares, as these do not correlate with airway anatomy and are unreliable 1
The ISA (Initial Size Approximation) approach should be followed, recognizing that different measurement techniques can yield differences of 2-3 cm in the same patient, creating potentially dangerous sizing errors 4
Clinical Application
OPAs should only be used in unconscious (unresponsive) patients with no cough or gag reflex and should be inserted only by trained personnel 1
Incorrect insertion can displace the tongue into the hypopharynx, causing complete airway obstruction rather than relieving it 1
The airway facilitates bag-mask ventilation by preventing tongue obstruction, though no studies have specifically validated their use in cardiac arrest patients 1
Alternative Considerations
In patients where oral airway placement is contraindicated (clenched jaw, intact gag reflex), nasopharyngeal airways are better tolerated 1
However, in the presence of known or suspected basal skull fracture or severe coagulopathy, an oral airway is strongly preferred over nasopharyngeal routes 1