Page 24 - JSOM Winter 2017

surgical procedure in which an LMA was used. That paper cuff pressures below those associated with tracheal damage at
noted that “the most widely accepted mechanism of recurrent altitude or above pressures associated with secretion aspira-
laryngeal nerve injury is pressure neuropraxia secondary to ni- tion during descent. Saline inflation minimizes altitude-related
trous oxide diffusion into the cuff.” Although most of these alteration in cuff pressure but creates excessive pressures at sea
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incidents of EGA-induced neuropraxia are temporary, vocal level. New techniques need to be developed.” 35
cord paralysis from recurrent laryngeal nerve damage may be
permanent. 58 The i-gel as the EGA of Choice in TCCC
There are now approximately 30 EGAs available in the mar-
The decrease in atmospheric pressure associated with helicop- ketplace. The i-gel has a soft gel-filled, noninflatable cuff that
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ter transport of combat casualties results in increasing pressure provides an anatomical impression fit over the laryngeal inlet.
inside the volume-limited EGA cuff and an increased risk of The shape and softness of the i-gel accurately mirror the peri-
barotraumatic neuropraxia. Studies of air-filled endotracheal laryngeal anatomy and thus eliminate the need for an air-filled
tube (ETT) cuffs have found that cuffs inflated before air trans- cuff. The i-gel comes in seven sizes for both adult and pediatric
port are likely to exceed critical pressure levels rapidly during usage and has gastric access and oxygen delivery components.
flight. 59,60 Further, if the EGA is inserted at altitude, there will The emerging literature has shown the i-gel EGA to be a good
be a loss of cuff pressure during descent, with a resultant loss option for managing the airway, both when studied alone or
of good seal. This results in recommendations for frequent in comparison to other EGAs. 5,10,13,16,24–30,64
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monitoring and management of air-filled cuff pressures dur-
ing ascent and decent. 59,60 The need for repeated checks of cuff In evaluating the various EGA devices, the New Technology
pressure is eliminated if the EGA used has a cuff filled with a Subcommittee of the CoTCCC took into account a number of
liquid such as water or saline rather than air, since liquids do additional qualities that were believed to be relevant to battle-
not expand at reduced ambient pressures, but using water or field use of an EGA. These included size and weight, training
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saline solution to fill airway cuffs designed to be inflated with for entry level medics, sustainment of skills, environmental
air is not allowed by the Air Force Instruction that provides engineering factors, cost, and durability. The device must be
guidance for care provided at altitude. US Air Force guidance robust and easy to use in any weather conditions as well as at
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for managing endotracheal and tracheostomy tubes states that various altitudes and temperatures. The device must be simple,
“8.4.8.3.1: Cuff pressure is usually maintained between 15– small, lightweight, inexpensive, and easy to train. In addition,
20 cm, and will be checked preflight, at cruise altitude, hourly, to address various battlefield contingencies, the EGA should
on descent, and prior to deplaning. Document cuff pressures be able to be inserted in both the supine and the prone posi-
on patient’s medical record.” This Air Force Instruction also tions as well as other casualty positions. 25,65
states that: “8.4.8.3.2: If an ERCC team is unavailable and an
ETT or tracheostomy tube cuff requires inflation for flight, In an Armed Forces Medical Examiner System (AFMES)
ensure it is inflated with air. Use minimal occlusion volume/ “Feedback to the Field” case series, of seven military postmor-
minimal leak technique in an effort to permit adequate ven- tem cases in whom the King-LT was used, four were incor-
tilation and avoid tissue trauma. WARNING: Excessive pres- rectly positioned. It is important to note that the position
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sure in the endotracheal or tracheostomy cuffs may decrease of the device as noted at autopsy may have been affected by
blood flow to tissue causing airway damage, while underinfla- post-mortem handling. The i-gel is associated with a very low
tion may permit air leak/ineffective ventilation and increased rate of dislodgement, and is easy to position correctly.
potential for aspiration of upper airway secretions.” EGAs
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are not specifically addressed in this instruction, but air-filled To summarize, favorable aspects of the i-gel include:
EGA cuffs would pre sumably require similar cuff pressure o Has a gastric tube port
monitoring as air-filled endotracheal tube cuffs. o Has an oxygen port
o Provides easy access for fiberoptic intubation
One study done by the Center for the Sustainment of Trauma o Is associated with very little aspiration
and Readiness Skills (C-STARS) in Cincinatti monitored ETT o Is popular with civilian anesthesiologists, paramed-
cuff pressures during a CCATT training flight to 8000 ft cabin ics, and emergency physicians
pressure to study the issue of overinflation in ETT cuffs at o Is widely used in European ambulance services
altitude in order to help prevent mucosal injury. The ETTs o Has a gel-filled cuff, not an air-filled one
were placed in a tracheal model while mechanical ventilation o Is simpler to use than other EGAs
was being performed. The control ETT cuff was inflated to o Can be inserted with the patient in prone position
20–22mmHg and was not manipulated. Another cuff was o Is easily trained
managed manually using a pressure manometer to adjust o Can be used in any environment or altitude
pressure varying altitudes. For the third tube, a “Pressure- o Costs about half of what other EGAs cost
Easy” device was used and set to a pressure of 20–22mmHg. o Has a 3-year shelf life
The fourth cuff was filled with 10mL of saline. The study o Comes in a smaller package than other EGAs
found that, in the control ETT tube cuff, pressure exceeded o Does not require in-flight monitoring of cuff
70mmHg at 8000 ft. The cuff managed manually was cor- pressure 7,18,36,44,46,54,55,66
rected for pressure at altitude but recorded low cuff pressures
at landing (<10mmHg). The PressureEasy device reduced the There is increasing evidence in the medical literature that the i-gel
pressure at altitude to a maximum of 36mmHg, but cuff pres- performs well in comparison to other EGAs. 4,5,10,13,17,25,26,29,30,64–
sure was less than 15mmHg at landing. The saline inflation 66,68 The i-gel has been found to perform well as an airway op-
eliminated cuff pressure changes at altitude, but the initial cuff tion in elective surgery patients. 2,5,6,16,24,27,68,69 The i-gel was also
pressure was 40mmHg. The authors concluded that “None found to be easily inserted in manikins who were in the prone
of the three methods using air inflation managed to maintain position. 25,65 The i-gel was found to be a suitable alternative

22 | JSOM Volume 17, Edition 4/Winter 2017