Page 50 - JSOM Fall 2021

nose tip and earlobe or to compare the tube diameter to the an adjustable flange are more expensive, which also needs to
patient’s nostril or little finger. However, none of the included be taken into consideration.
study findings demonstrated these specific calculations. Any
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relation between the little finger or nostril and NPA tube sizing According to Sareen et al., the ability of the NPA to main-
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was ruled out by Roberts and Porter. Therefore, the currently tain a patent airway is dependent on the internal diameter of
taught methods of sizing NPAs are possibly incorrect. 2 the tube and the correct distal positioning. However, it is our
belief, and that of many study authors, that the length of the
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Considering both US national and international accepted pro- tube is more important than the diameter. 2,3,8,9 Stoneham spe-
tocols, the two most-followed professional guidelines in the cifically postulated in 1993 that the airway length should be
use of NPA tubes are those provided by the Tactical Combat independent of the internal diameter.
Casualty Care (TCCC) and the Advanced Cardiac Life Sup-
port (ACLS) guidelines. It is important to note that both mili- This literature review was undertaken in reference to tube
tary and civilian use of the NPA is of critical life-saving value. length and not to external or internal tube diameter. However,
recognizing the importance of understanding both the exter-
TCCC is the responsibility of the US Department of Defense. nal/internal diameter, we are including the following informa-
These are evidence-based guidelines and considered to be best- tion. Manufacturers of NPA tubes most often relate the length
practice guidelines specifically customized for the battlefield. to the external diameter. It would then be supposed that the
First published in 1996, they are typically updated annually. internal diameter should be based on the external diameter.
These guidelines identify three phases: (1) Care Under Fire, However, according to technical data from Rüsch/Teleflex,
(2) Tactical Field Care, and (3) Tactical Evacuation. The use there is a relationship variant decrease of 2.3 to 3.0mm, based
of NPA tubes is recognized under the Airway Management on respective external diameter size of 7.3 to 10.0mm. The
section of the TCCC guidelines in phases 2 and 3. The online external diameter of 7.3 to 10.0mm corresponds with Char-
training video specifies measuring the NPA length from the tip rière sizes 22 to 30. This relationship between external and
of the nose to the bottom of the ear. 15 inrternal diameter also can vary based on two other important
parameters: the material used to manufacture NPAs (e.g., la-
The ACLS online homepage provides information on position- tex-free, silicon/latex, polyvinyl chloride, silicon/rubber) and
ing both oropharyngeal airway and NPA tubes. To determine the availability of products within one’s country.
the correct NPA tube length according to ACLS statements,
the nose tip-to-earlobe distance is measured. The diameter of The NPA tube should be neither too short nor too long to pro-
the NPA should be a little smaller than the diameter of the vide sufficient oxygenation. If it is too long, accidental esoph-
nostril. 9 ageal intubation might occur, with the consequent problems
of hypoxia and gastric inflation; or the tip of a long NPA tube
The articles we reviewed had an equal number of studies could irritate the epiglottis, which would cause a cough reflex.
that focused on the nares-to-vocal cords distance and the If the NPA is too short, the tip of the tube might end in the
nares-to-epiglottis distance. The data indicated that the na- vallecula, causing airway obstruction and possibly stimulating
res-to-vocal cords and nares-to-epiglottis distances are cor- cough or gag reflexes or perhaps laryngospasms. 8
related with external body measurements, such as body
height. Also, other distances between certain facial landmarks In all emergency training, the focus in teaching must be to con-
could be useful to determine the correct tube length, such as tinuously observe the clinical condition of the patient after in-
the nose tip-to-mandible distance and the nose tip-to-ear tra- serting an NPA: (1) The device is inserted beyond the tongue
gus distance. base to stabilize the airway. This may mean inserting the tube
up to the flange. (2) If a cough reflex results, that is, if the tip
Patient gender must also be considered, as well as the fact that of the tube touches the epiglottis (too deep insertion), the place-
many of the studies were conducted among Asian and Indian ment of the tube must be corrected, that is, pulled back in possi-
populations. Because of ethnic variations, facial landmarks bly 5-mm steps. Millimeter or centimeter markings on the tubes
may differ. Asian patients usually have a more bulbous nose, would be helpful for this maneuver. Also, the emergency staff
with the lack of a defined nasal tip compared with Caucasian needs significant clinical training in detecting incorrect tube po-
noses. Therefore, when studies used the lateral border of the sitioning (e.g., insufficient breathing/breath sounds, cough or
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nares as a reference point, as opposed to the nose tip, it be- gag reflex). (3) Upon correct placement, an adjustable flange
comes more difficult to compare the exact length of certain may be positioned at the nostrils and fastened to minimize the
facial landmark distances. possibility of displacement. Doing this can also provide the
emergency technician with visual evidence of NPA movement.
The referenced distances from the nares-to-epiglottis and na- (The best training must resemble real-life situations; therefore,
res-to-vocal cords varied widely in our reviewed studies. This more sophisticated training devices need to be developed.)
may be because of gender and ethnicity, but it eliminates a
general “one-size-fits-all” perception of the optimal NPA Another critical aspect is the possible displacement of the NPA
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tube length. According to Stoneham, one solution would be resulting from movement of the head and neck, leading to ac-
to manufacture standardized NPA tubes of the same length cidental extubation, especially if the tube is too short. Stone-
with different diameters and then apply the correct length by ham concluded that the relation between laryngeal structures
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changing the safety pin or adjusting the flange. Newer tubes and the airway is influenced by the head position. This needs
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provide an adjustable flange ring. However, in an emergency to be taken into account in further studies.
situation, it might be easier to choose from a variety of dif-
ferent tube lengths and then insert the tube up to the flange Specifically, regarding military members, every soldier could
instead of dealing with adjustable parts. Also, NPA tubes with have an NPA tube in their emergency kit, cut to length to meet

48 | JSOM Volume 21, Edition 3 / Fall 2021