Oropharyngeal (or Guedel) tubes are a type of airway adjunct. The correct size is selected by measuring the airway against the patient’s head, either between the corner of the mouth (labial commissure) and the external auditory meatus, or from the angle of the jaw to the incisors. A nasopharyngeal tube is sized by approximating the diameter of the patient’s little finger. Laryngeal mask airways (LMAs) are sized according to the approximate patient size and sex, as follows:

LMA size 3: small women

LMA size 4: large women or small man

LMA size 5: large man