Estimate NPA size
Classic teaching is to estimate the nasopharyngeal airway (NPA) size as the length from the patient’s nares to tragus of the ear, and the oropharyngeal airway (OPA) from the maxillary incisors to the angle of the mandible. However, a few recent studies found that (nares to tragus minus 10mm) more accurately predicted the correct size NPA in children: Johnson et. al. and Nemeth et. al.