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Hong Kong Journal of Emergency Medicine
Role of laryngeal mask airway in emergency department and pre-hospital
environment
FKC Chu
LMA and Intubating LMA (LMA-Fastrach) have been widely used by anesthesiologists in operation theaters
and have achieved great success. Its use in the emergency department and pre-hospital setting by EMS has
recently been proven to be very successful. It is also a very useful tool in providing a quick airway in case of
failed intubation and failed ventilation situations. In this article, some of its use in emergency departments
and pre-hospital setting are discussed. (Hong Kong j.emerg.med. 2003;10:57-62)
Keywords: Emergency department, laryngeal mask airway
Introduction pre-hospital setting.3 It is designed to provide a quick
airway and to assist intubation.
The Laryngeal Mask Airway (LMA) was introduced
by a British anesthesiologist Archie Brain in the 1980s.1 This article reviews the development, advantages and
However it has only been used in Emergency Medicine disadvantages of Laryngeal Mask Airway (LMA) and
and pre-hospital setting recently. It was initially Intubating LMA and particularly its role in the
designed to bridge the gap between facemask and emergency department and pre-hospital environment.
endotracheal tube. It provides a better airway than
the facemask with less dead space. On the other hand,
it does not require neuromuscular blockade or History
laryngoscopy for placement. It is also better tolerated
than intubation. Thus, it has gained widespread The LMA was invented by a British anesthesiologist
popularity and is being extensively used in patients Dr. A.I.J. Brain in London in 1981. By examining
undergoing general anesthesia. More recently, it has postmortem specimens of the larynx, Brain noted
become a tool for difficult or failed intubations in the that an airtight seal could be achieved around the
ASA (American Society of Anesthesiologists) Difficult laryngeal inlet by an inflated cuff in the
Airway Management Algorithm.2 hypopharynx. Prototype LMA was developed from
molds made from Plaster of Paris of cadaveric
With the modification of the usual Laryngeal Mask pharynx and the Goldman dental mask. After years
Airway, a new prototype of LMA-Intubating LMA of developments, the first LMA was commercially
(ILMA or LMA-Fastrach) was developed. It offers available in Britain in 1988 and was approved by
broader applications in the emergency department and the FDA in US by 1992. Nowadays, commercially
available LMA is manufactured from medical-grade
silicon and consists of an obliquely cut tube
Correspondence to: mounted into the concave central part of an oval
Chu Kin Chiu, Francis, MBBS(HK), MRCP(UK)
mask. (Figure 1) Also, different sizes and types of
Queen Elizabeth Hospital, Accident and Emergency Department,
30 Gascoigne Road, Kowloon, Hong Kong LMA, including the Classic and the intubating
Email: chu00338@i-cable.com LMA (Fastrach, as shown in Figure 2) are available.
58 Hong Kong j. emerg. med. Vol. 10(1) Jan 2003
Figure 1. Laryngeal mask airway. Figure 2. Intubating laryngeal mask airway.
Insertion of LMA patients, insertion of an LMA required a mean of 39s
with a mean of 1 attempt/patient success as compared
Preparation with 206s for an ETT with 2.2 attempts/patient
Before every use, the LMA should be checked for success. No one failed to insert an LMA but 10 out of
cracks and whether it has been sterilized as LMA is a 19 could not intubate.
reusable device. The cuff should be deflated so that
the tip forms a flat leading edge. Then the convex Proper insertion technique is necessary for optimal
surface, but not the concave side of the LMA should placement and poor technique may lead to the loss of
be lubricated. Lubricating the concave side may lead airway.
to aspiration of lubricant, resulting in coughing and
laryngospasm. Standard insertion technique is described in the LMA
instruction manual and is summarized below. Following
Although the LMA can be inserted under topical adequate amount of induction agent and narcotics until
anesthesia, it is normally inserted under general jaw relaxation is achieved, place the patient in the
anesthesia. Correct insertion requires an adequate level "sniffing the morning air position" with neck flexed and
of anesthesia to obtund pharyngeal reflexes. In contrast head extended if cervical spine immobilisation is not
to endotracheal intubation, muscle relaxants are required. Place the lubricated LMA into the mouth, press
unnecessary. Intravenous induction agents, together it back against the hard-palate with the index finger to
with opioids (such as fentanyl or alfentanyl) are flatten the LMA.
adequate for insertion in most circumstances.
Now, it is important to check that the rim of the
Among all the available induction agents, Propofol in LMA does not fold back on itself at this stage. Then
the dose of 2.0-2.5 mg/kg seems to be the best for slide the LMA behind the tongue and into the
insertion of LMA. pharynx until a definite resistance is felt to indicate
that it has reached its final location. The cuff
should then be inflated. During inflation, the LMA
Techniques of insertion should be free to move and it will invariably centre
itself over the laryngeal opening.
Unlike intubation, insertion of LMA can be achieved
in a high proportion of patients with little practice. Confirmation of proper position can be achieved by
Therefore LMA can be used widely in emergency and end-tidal CO2 detection, or by observing movement
pre-hospital setting. In one study,4 comparing success of reservoir bag. A black line printed along the
and time to airway management by paramedics and posterior surface of the LMA tube gives a visual
respiratory therapists in anesthetized and paralysed confirmation of the correct position.
Chu/Role of laryngeal mask airway 59
Clinical use of LMA valve mask often requires two hands to make a
tight seal and LMA, in this circumstance, can
(1) LMA as an airway for operation: free the resuscitator for injection or chest
It is primarily designed as an alternative to simple compression.
facemask for protected and assisted ventilation
i n c e r t a i n s u r g i c a l p ro c e d u re s i n w h i c h Literature review showed only one reported case
endotracheal intubation is not required. of failure to ventilate in a patient with LMA. 5
Some studies have shown that LMA has been
A further advantage is that the anesthesiologist used successfully by physicians, nurses and
can free his hand for other task, such as drug paramedics, regardless of patient's position.
administration.
The LMA can also be placed in patients with
fixed neck deformity and limited mouth opening
(2) LMA as an emergency airway: as a result of facial burn.6
Recently, in algorithms published by both the
American Society of Anesthesiologists and the (3) To facilitate intubation through LMA:
European Resuscitation Council, the LMA is A 6-mm internal diameter endotracheal tube
considered a primary option for the management (ETT) can be passed through the tube of size
of difficult airway and failed airway patients. 2 3 and 4 LMA. If the LMA is well lubricated and
(Figure 3) correctly positioned, the ETT can be inserted
blindly through the aperture into the larynx.
Although endotracheal intubation is the most Successful intubation rate can be up to 90%.
secure way to control and maintain the airway,
it can sometimes be very difficult, even in However, after introduction of the special
experienced hands. Maintaining ventilation with Intubating LMA, blind intubation through LMA
bag-valve mask can also become difficult becomes less common.
especially in edentulous or bearded patients.
Moreover, maintaining ventilation using bag- A size 6 ETT may be too small for an adult male,
the insertion of a larger ETT can be facilitated
by using the gum-elastic bougie. A gum-elastic
bougie is inserted through the LMA and act as a
guide-wire.7 With the removal of the LMA, larger
size ETT can be inserted into the larynx through
the bougie.
In order to improve accuracy, the ETT can be
mounted onto the fiberoptic brochoscope which
is then passed through the LMA.8 This technique
allows the vocal cord to be visualized. It avoids
blind intubation, and increases the success rate.
It is useful in paediatric patients since ILMA is
not available in paediatric patients.
(4) Resuscitation:
Figure 3. An algorithm showing the use of LMA in difficult Besides acting as an immediate airway, LMA can
and failed airway management. also be used as a conduit for administration of
60 Hong Kong j. emerg. med. Vol. 10(1) Jan 2003
medications during resuscitation. In one study, Complications of LMA
considerable amount of adrenaline was found in Complications are rare with its use in the
pulmonary tree after it is injected down a seated operation room. Unlike the ETT, it does not
LMA in cadaver.9 However, similar results are not protect from aspiration of gastric content and
demonstrated in other studies. 10 Thus, it is other secretion. Laryngospasm occurs when the
suggested that during resuscitation, in those patient is not deepened enough during insertion.
patients who have no airway nor venous access, These are not actually significant in patients
injection of medication down the LMA may be undergoing elective surgery since most of them
worth the attempt, but the outcome is not as have been fasted for an adequate period before
reliable as via the ETT. operation. Brimacombe conducted a meta-
analysis of the published literature in 1995 and
Advantages of using LMA in ED found that the incidence of aspiration was only
The LMA can be easily placed and provides a 2/10000 with LMA 12 which was similar to that
quick and adequate airway with relatively few recorded during general endotracheal anaesthesia.
complications. It is easy to learn. Thus it can be
used by physicians, nurses, and paramedics to However, it is a major problem in our patients
provide quick airway during resuscitation, in Emergency Department. Most of them have
especially for those who are inexperienced in not been fasted, thus regurgitation and aspiration
intubation or in cases of failed intubation. In a can be a serious problem. Like the rapid sequence
study concerning pre-hospital airway management induction, cricoid pressure should be exerted and
by ambulance officers in Australia, the overall maintained continuously after placement to
success rate of LMA insertion was 80%. 11 reduce regurgitation and aspiration of gastric
contents in patients who are at high risk of
It is better than bag-valve mask since one can aspiration like (1) those after prolonged bagging,
free his hand for other resuscitation process and (2) pregnancy, (3) morbid obesity, and (4) those
it is more secure than the bag-valve mask. with upper gastrointestinal bleeding.
In an unanticipated difficult intubation, LMA Positive pressure ventilation, although possible
can provide a temporary airway to prevent in LMA if the pressure does not exceed 20 cm
desaturation, while one can buy time to call for H2O, 13 is relatively contraindicated. It leads to
assistance, perform surgical airway or re-intubate air leak and promotes gastric distention and
through the LMA with or without gum-elastic aspiration. Therefore, it may not be suitable in
bougie or fiberoptic bronchoscope. situations of severe asthma or acute pulmonary
oedema.
LMA can be placed even if the patient has
fixed neck deformity, or needs cervical spine Misplacement of LMA will lead to obstruction.
immobilisation, or is in a prone or lateral Improper insertion of LMA may fold the
position. In trauma victims who are trapped, epiglottis and thus obstruct the airway. Over
and those who need to secure the air way inflation of the LMA cuff may impose pressure
quickly, LMA can provide a better airway than on the hypopharynx and could cause pressure
facial mask, and under this unfavourable necrosis. Compression on nerve can result in
occasion, it is rather difficult for paramedics dysarthria, which is usually transient. Tongue
or even emergency physicians to intubate the cyanosis has been reported due to occlusion of
victims. the lingual artery by LMA. 14
Chu/Role of laryngeal mask airway 61
The Intubating Laryngeal Mask Airway (ILMA) 4. Swing the entire device downward into place, then
Laryngeal Mask Airway has provided a quick inflate and secure. Indications that the ILMA is
airway for patients with difficult intubation with correctly positioned include (i) the ability to
great success. However, for patients seen in generate an airway pressure of 20 cm H 2O, and
emergency department (ED) and Emergency (ii) the ability to ventilate manually.
Medical Services (EMS), a definite airway is 5. Pass the appropriate-sized wire-reinforced tube
usually preferred. By modification of the LMA, through the ILMA with lubricants.
a new prototype has now been developed – the 6. If resistance is encountered, it is most likely due
Intubating LMA (ILMA). to the downfolding of the epiglottis or lodging of
the tube against the vestibular wall. Rotating the
ILMA consists of a short, anatomically curved, ETT bevel may solve the problem.
rigid, stainless steel shaft that follows the oral, 7. If difficulty is encountered, it is possible to try
pharyngeal, and laryngeal axes of the airway, smaller sized ETT or to guide the ETT with the
allowing facile alignment of the mask with the help of a fiber-optic bronchoscope.
glottis. It has a metal handle that aids in insertion 8. Finally, the ILMA can be removed or can be left
and manipulation of the device. There is a V- behind after the ETT is inserted.
shaped ramp that guides the ETT through the
mask aperture directly and a moveable but rigid A number of studies have shown that ILMA has a high
epiglottis elevating bar that lifts the epiglottis success rate but the learning curve is somewhat steeper
out of the way of the advancing ETT. than the usual LMA.16
It is particularly useful in the ED and EMS Case reports have also demonstrated the successful use
setting when compared to the standard LMA as of ILMA in patients with cervical spine injury
it can assist intubation, minimise head and neck undergoing rapid sequence induction.17
movement, and therefore particularly useful in
patients with cervical spine injury. Thus, for emergency department staff and emergency
medical service providers, Intubating LMA offers an
attractive option for emergency airway management
Insertion technique in the "cannot intubate and cannot ventilate scenario".
It can provide an emergency airway even though
The insertion of ILMA is different from that of the intubation may not be achieved.
usual LMA in several ways. 15 The technique involve
the following steps: The ILMA should not be used for a prolonged
1. Keep the patient's head in neutral position, rather period once a definite airway is achieved since it
than in slightly extension. may result in pressure necrosis of the pharyngeal
2. Hold the intubating LMA by its handle and mucosa.
position the mask tip flat against the hard palate
just inside the mouth and immediately posterior
to the upper central incisors. Then slide the mask Conclusion
tip slightly back and forth to coat the hard palate
with lubricant. The American Society of Anesthesiology has
3. Slide the mask backwards, following the curve of introduced the use of LMA and the ILMA as a tool
the tube with fingers of the other hand to open for emergency airway management in situations when
the mouth slightly. one "cannot intubate or cannot ventilate".
62 Hong Kong j. emerg. med. Vol. 10(1) Jan 2003
Both the LMA and the newer ILMA are easy to use aided by the laryngeal mask airway. Anaesthesia 1989;
44(12):1015.
and require only little training to master the technique.
8. Silk JM, Hill HM, Calder I. Difficult intubation and
They are ver y suitable for use in emergency the laryngeal mask. Eur J Anaesthesiol 1991;Suppl 4:
department and by pre-hospital medical service 47-51.
providers for patients with difficult airway. 9. Challiner A, Rochester S, Mason C, Anderson H,
Walmsley A. Spread of intrapulmonary adrenaline
administered via the laryngeal mask. Resuscitation
1997;34:193.
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