Page 47 - JSOM Fall 2021

Studies on the Correct Length

of Nasopharyngeal Airways in Adults
A Literature Review

Catharina Scheuermann-Poley, MD*; André Lieber, MD

ABSTRACT
The use of a nasopharyngeal airway (NPA) as an adjunct air- of consciousness, maintained gag reflex, or limited mouth
way device can be critically important in emergency medicine. opening). 3
When placed correctly, the device can prevent upper airway
obstruction. The goal of our review was to learn whether Multiple advantages are associated with the use of NPA tubes.
there is scientific evidence about the correct length and the They can quickly provide airway proficiency thought to be
insertion depth, and also possible facial landmarks, that can better tolerated than oral airways or oral endotracheal tube
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predict the appropriate length of the NPA. There has been no intubation, and the nasal placement of an NPA tube seems
real consensus on how to measure the appropriate tube length to minimize gagging. It can be applied without the use of any
for the NPA. Several studies have been able to demonstrate further device, and the nasal route is also preferred during fi-
correlations between facial landmarks and body dimensions; beroptic intubation. Despite these advantages, however, the
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however, we did not find any scientific evidence on this mat- NPA appears to be used less frequently than needed, possibly
ter. The reviewed studies do not indicate evidence to support because of reports of intracranial misplacement, specifically
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current recommended guidelines. This could potentially lead in basal skull fractures. There have been at least two case-
to both military and civilian emergency training programs not study reports from the US military of intracranial placement
having the most accurate scientific information for training of NPAs because of craniofacial trauma. 6,7
on anatomic structures and also not having a better overall
understanding of intraoral dimensions. Emergency personnel Early NPA tubes were plain, uncuffed rubber tubes; these have
should be taught validated scientific knowledge of NPAs so been replaced with tubes made of better materials (e.g., latex,
as to quickly determine the correct tube length and how to soft polyvinyl chloride, silicone), while potential displacement
use anatomic correlations. This might require further studies into the pharynx is prevented by a flange at the proximal end. 8
on the correlations and perhaps radiographic measurements. The correct and effective NPA tube has an optimal position
A further approach includes adjusting the tube to its correct with the proximal end fully inserted up to the flange at the
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length according to the sufficient assessment and management nostril opening and the distal end protruding beyond the pha-
of the airway problem. ryngeal edge of the soft palate, not extending over the epi-
glottis. 4,8,10 Some studies and guidelines have established that
Keywords: airway; nasopharyngeal; tubes; emergency; trauma the best position for the distal NPA tip is 1cm above the epi-
glottis 2,3,8,9 (Figure 1). Malpositioning of the NPA tube may
cause oxygen deprivation, with such serious consequences as
hypoxia, hypercapnia, gastric acid reflux, aspiration, neuro-
Introduction
logical impairment, or death. 2,3,8
The NPA is an important airway management device used in
military and civilian first-line emergency medicine and in rou- Several studies have examined the correlation between the
tine anesthesiology. This simple airway adjunct can prevent NPA and various body measures, such as height, weight, and
upper airway obstruction caused by the tongue to maintain a arm length, as well as correlating the NPA to other external
clear airway and facilitate nasotracheal suctioning. The cor- body measurements. An accurate prediction of the optimal
1,2
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rect use, placement, and length of the tube are crucial for its length and insertion depth of the NPA tube is critical in pro-
effective application. viding an effective adjunct for airway management. Because it
is performed without visualization of nasopharyngeal struc-
To maintain a stable airway, the NPA is commonly used espe- tures, when NPA insertion is required, it is essential to have
cially when the oropharyngeal airway is not suitable because certain landmarks that predetermine the optimal length of the
of oral trauma (e.g., bleeding, swelling, disruption of the roof NPA, especially in emergency situations.
of the mouth) or facial trauma (e.g., Le Fort fractures) or for
a surgical procedure requiring access to the mouth or tongue. Frequently taught methods of sizing an NPA are based on the
Another reason might be with patients who cannot tolerate an width of the patient’s nostril or little finger. Magnetic reso-
oropharyngeal airway (e.g., a patient with an elevated level nance imaging (MRI) data demonstrate that these methods are
*Correspondence to cathipoley@web.de
Major Scheuermann-Poley and Colonel Lieber are affiliated with the Department of Orthopedic, Septic and Reconstructive, and Thoracic Sur-
gery, Military Hospital Berlin, Germany.

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