Nasopharyngeal, oropharyngeal airways and the laryngeal mask airway

23.3 Nasopharyngeal, oropharyngeal airways and the laryngeal mask airway



Michelle Lin, Conor Deasy



Background


Children have relatively large tongues, which may fall back and cause airway obstruction when there is loss of nasopharyngeal muscle tone, for instance, in patients who are post-ictal or overly sedated by drugs. Hypoxia and hypercarbia may develop. Non-invasive airway adjuncts, such as nasopharyngeal (NP) and oropharyngeal (OP) airways, can maintain a patent airway even when the tongue falls back against the posterior pharyngeal wall. The laryngeal mask airway (LMA) is designed to provide a seal around the laryngeal inlet when inserted and the cuff inflated and is used in situations involving a difficult bag valve mask fit in an unconscious patient and as a back-up device where endotracheal intubation is not successful.


Structurally, an NP airway is hollow, made of latex or a latex-like substance, and has a slight curvature to approximate the curvature of the nasopharynx. The distal end has a bevel, which helps to tunnel through the nasopharyngeal soft tissue, but which may also cause inadvertent shearing trauma to the nasal septum. The proximal end of the NP airway has a wide flange to anchor the tube in place at the nostril orifice. Patients tolerate this airway adjunct better than an OP airway because it does not trigger the gag reflex.


The OP airway is hollow, made of plastic, and has a slight curvature to approximate the curvature of the oropharynx. The distal end rests along the posterior tongue, which would trigger the gag reflex in an awake patient, and the proximal end has a wide flange to anchor the tube in place at the lips.


Airway adjuncts may allow adequate spontaneous ventilation and avert the need for bag–valve–mask ventilation or the more invasive technique of tracheal intubation.



Indications for OP or NP



• Airway obstruction.

• Respiratory decompensation.

• Seizures.


Contraindications



NP airway



• Age less than 1 year old – the nares diameter is too small to introduce an NP airway.

• Nasal obstruction – attempting to introduce an NP airway into a nasal passage that is obstructed will be unsuccessful and may cause traumatic epistaxis.

• Severe facial injury or suspicion for basilar skull fracture – a fractured cribriform plate may allow an NP airway to traverse incorrectly into the intracranial space rather than into the posterior oropharynx.


OP airway


Intact gag reflex – because the OP airway tip rests on the posterior tongue, a patient with an intact gag reflex will likely vomit and aspirate gastric contents.



Equipment



Lubricating jelly (for NP airway).

Tongue blade (optional for OP airway).

NP airway (Fig. 23.3.1).

OP airway (Fig. 23.3.2).

image

Fig. 23.3.1 Nasopharyngeal airway.


image

Fig. 23.3.2 Oropharyngeal airway.



Preparation



NP airway


Determine the correct NP airway size by one of three methods:


Follow the recommendations on a length-based resuscitation tape.

Choose an NP airway the length of which is equivalent to the distance from the patient’s nasal tip to the tragus of the ear (Fig. 23.3.3).

Choose an NP airway the outer diameter of which is equivalent to the nostril’s inner diameter. Cut the length of the tube according to the length-measurement guide in Method 2.

image

Fig. 23.3.3 Sizing the NP airway: nasal tip to tragus of ear.



OP airway


Determine the correct OP airway size by one of two methods:


Follow the recommendations on a length-based resuscitation tape.

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Sep 7, 2016 | Posted by in EMERGENCY MEDICINE | Comments Off on Nasopharyngeal, oropharyngeal airways and the laryngeal mask airway

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