The Nasopharyngeal Airway
This is a narrow flanged tube which is passed through the nasal cavity and into the posterior nasopharynx.
Anatomy of the nasopharyngeal airway
The tube is made of polyethylene furanoate (PEF) and is pretty well inert, from the point of view of biology. The internal surface of the tube is striated longitudinally, which is supposed to enhance the passage of the suction catheter in and out of the tube.
Details of function
A correctly sized nasopharyngeal airway lifts the soft palate off the back of the nasopharynx. It acts as an airway in situations where the posterior palate collapses and blocks airflow from the nasal cavity to the pharynx. If the mouth is closed, the patient will either obstruct silently, or make a horrific snoring sound.
The nasopharyngeal airway makes this sound go away.
Indications for use
- To ensure airway patency:
- Semi-conscious patient with loss of upper airway muscle tone, but with an intact gag reflex
- Semi-conscious patient with difficult bag/mask seal and with an intact gag reflex
- To improve airway hygiene:
- Suctioning a patient with poor secretion clearance
An of course, if one digs deep enough, one finds that there are other, weirder indications.
Contraindications for use
- Awake patient: the process of inserting this thing is uncomfortable, even with local anaesthetic spray
- Base of skull fracture: you could insert it into the brain. Sounds implausible, but its probably more common than you think. That also means nasal fractures.
- Coagulopathy: though soft and rubbery, this object still tends to cause enough trauma to result in clinically significant epistaxis.
Methods of use/insertion
- The airway is sized by placing it vertically along the patients face, with the flange at the level of the nares, and the tip at the external auditory meatus (practically, the tragus will suffice). No other sizing method is satisfactory. Ideal position is about 10mm above the epiglottis.
- Spray nose with local anesthetic
- Lubricate the tube
- Insert at a 90 degree angle to the face, along the septum.
- The tip, if properly sized, should be visible just behind the uvula.
- Internal diameter of the tube is marked on the flange, to assist with size selection
- The flange limits the depth of insertion - so you cant accidentally lose the tube in somebody's airway
- Atraumatic bevelled tip; prevents mucosal injury
- PEF composition is biologically inert and nonimmunogenic
- Soft rubbery construction - prevents mucosal injury
- Available as a sterile product for single use
Complications of use
- Epistaxis from the violence of its insertion
- Gagging, vomiting, aspiration - particularly if the nasopharyngeal tube is too long - it will protrude too far into the posterior pharynx and the result will be the stimulation of the gag reflex.
- Intracranial insertion: no, really.
- Failure of airway - it may not be obvious externally, but the undersized tube may not be long enough to function normally. Or, it may be clogged with snot. Or, the too-long airway can get lodged in the vallecula, and be completely useless or counterproductive. In either case, casual inspection would not betray the fact that the airway is useless.
- Ulceration: because these things are so well tolerated, there exists a temptation to leave them in situ in patients who are chronically semiconscious. This is wrong. The pressure put on the mucosa by such a foreign device can lead to ulceration and pressure-area-like necrosis.
In this excellent article, I have found records of unusual practice from days gone by. There was apparently a time during which people believed that various non-facial anatomical landmarks could be used to size the tube properly. Of course, as a product of more recent airway training, I found this quite bizarre, but in the late 20th century it was quite common for critical care doctors to estimate the tube size according to the width of the nostril, or to the thickness of the little finger. Naturally, by bronchoscopic examination of tube placement, we have now discovered that all those methods were total bullshit.
Tragus to nostril, people.