Page 26 - Journal of Special Operations Medicine - Fall 2015

of 5mm, has an outer diameter of 9.4mm. Nonsurgeons places an already potentially seriously ill patient at risk
may have a difficult time inserting a tracheostomy tube for aspiration. The Melker cuff diameter, when inflated
into the CTM, as this may require significant force. 32 with 10mL of air is up to 29mm in diameter compared
with the 23mm diameter for a typical 6.0 ETT.
Endotracheal Tubes
When used for SC, the endotracheal tube (ETT) is being The Melker tube has flexible arms that extend laterally
used in an improvised fashion. The distance from the (Figure 1) along the patient’s neck. These have loops
CTM to the carina is approximately 10cm to 12cm in used to secure the airway in place with a cloth ribbon or
the adult. Using an ETT also has some inherent poten- tape. Thus, the Melker is much easier to rapidly secure
tial drawbacks. A cuffed 6.0 ETT is commonly recom- compared with an ETT, which decreases the risk for dis-
mended for SC. The outer diameter of a Mallinckrodt lodgement or migration into the main-stem bronchus
6.0 cuffed ETT is 8.2mm. The pilot balloon inserts onto during patient transport or movement.
the ETT at the 16-cm mark. After inserting the ETT
through the CTM, particular attention should be given
to avoiding advancing the ETT too far into the trachea,
which could result in a main-stem bronchial intubation.
Conversely, an adequate length of the airway cannula
should be advanced into the trachea to prevent acciden-
tal extubation. The overall length of the Mallinckrodt
6.0 ETT is 26cm to the 15mm adapter. Because of its
excess length, compared to the distance from the CTM
to the carina, main-stem intubation rates of up to 15% Figure 1 CricKey
have been documented in the prehospital setting. 36

The 6.0 ETT, even when “cut down” to the pilot balloon
tubing insertion at the 15cm mark leaves approximately
10cm to 12cm of excess ETT length that extends outside
of the incision. While this excessive length has little ef-
fect on manual ventilation of the casualty, this long sec-
tion of tubing is difficult to secure to the patient’s neck
and is prone to either dislodgement, tube kinking, or Training Methods
migration into the main-stem bronchus, especially dur-
ing patient movement and transport, when loss of the There is no accepted standard for patient models. Sev-
airway may not be readily apparent. eral different patient models have been described. These
include human cadavers, 10,19,20 animal models, plas-
32
tic manikins, 5,17 lung models, and preserved pig lar-
30
Melker Airway
ynxes. 14,35 Comparisons of SC speed and success rates
We recommend a cuffed Melker or similar airway will likely vary across different training models. A
(Cook Critical Care; www.cookmedical.com) designed plastic manikin will not likely perform the same as an
for insertion into the CTM. When tracheotomy or ETTs animal model or cadaver. Likewise, a caprine (goat) ani-
are used for SC, they are being used in an improvised mal model will present training variables different than
fashion. Unlike a conventional ETT, which has a bev- an ovine (sheep) model or a porcine (pig) model. Each
eled tip but blunt edges at the lumen, the Melker has a model has different airway anatomy, skin thickness,
circumferentially tapered end that, when combined with and the like. Cadaver models, likewise, will have some
the dilator, inserts much more smoothly than an ETT or differences. The tissue elasticity of fresh cadavers has
a tracheostomy tube. The Melker 5.0 tube has an outer a different feel than embalmed or preserved cadavers.
diameter of 7.4mm and is, therefore, more easily placed Animal models and infused cadavers can bleed during
through the CTM, compared with the 8.2mm outer di- the procedure, while manikins and noninfused cadav-
ameter for a 6.0 ETT or 9.4mm outer diameter for a 4.0 ers do not. Cadaver models are also most often elderly
Shiley. The Melker’s total length is 9cm, so main-stem patients who may have little subcutaneous tissue and
intubation is not likely. easily discernible anatomy, while a pig model will have
a thick neck and challenging anatomy. 18
A cuffed tube reduces the potential for aspiration of
blood, secretions, or vomitus. The average diameter of CricKey Technique
the adult male trachea is 25mm. Using an airway with a The CricKey (CK) is a curvilinear, round introducer
cuff that is less than the tracheal diameter when inflated with an overall length of 19cm, an upturned distal tip,

14 Journal of Special Operations Medicine Volume 15, Edition 3/Fall 2015