Laryngeal Mask Airway – Indications, Contraindications, and Insertion Technique
- LMA is a supraglottic airway device which is simple and rapid to use, for oxygenation and ventilation.
- The major disadvantage to LMA devices is that it does not protect the airway from aspiration.
- Given that most patients in the ED will have full stomachs, LMAs are considered only a temporizing measure until a definitive airway is secured (i.e cuffed ETT in trachea).
Indications for LMA insertion
- Airway rescue device when bag mask ventilation is difficult, and intubation has failed.
- Resource limited settings – pre-hospital care, cardiac arrest.
Predictors for difficulty with LMA usage
- Distorted airway anatomy.
- Poor mouth opening, oropharyngeal pathology.
- Restricted cervical spine.
- Increased risk of gastric insufflation and aspiration.
- Full stomach.
- Increased airway pressure requirements for adequate ventilation: reduced lung compliance (obesity, pulmonary edema, restrictive lung disease) or high airway resistance (asthma, COPD).
There are many commercially available LMAs which are classified based on presence of a gastric drainage lumen. Newer generations also have intubating channels that allow easier conversion to ETT.
- First generation – no gastric drainage lumen (e.g. classic LMA).
- Second generation – gastric drainage lumen (e.g. iGel).
Insertion of LMA
- Select size of LMA based on weight. In general, use a size 4 for adult women and size 5 for adult men.
- Prepare the LMA by deflating and lubricating the cuff.
- Place patient in sniffing position and ensure patient will tolerate the device (no gag reflex, no response to jaw thrust).
- Neuromuscular blocking agents are not needed.
- Insert LMA pressing the cuff against the hard palate. Advance LMA until definite resistance felt.
- Inflate cuff to achieve adequate seal (no audible leak with bag ventilation).
- 20cc for size 3, 30cc for size 4, 40cc for size 5.
- Maintain peak airway pressures less than 20cm H2O (otherwise you risk gastric insufflation).
- Secure the LMA with tape.
- Devise an airway plan for a definitive secured airway (i.e cuffed ETT in the trachea).
Troubleshooting insufficient LMA seal/persistent leak
- Ensure LMA is midline and head/neck is in neutral position.
- Move LMA up and down to free trapped or folded epiglottis.
- Re-insert device.
- Use a larger LMA.
- Insertion of the LMA cuff tip into the glottis may mimic laryngospasms with high airway pressures, slow expiration, and wheeze.
Quality Of Evidence?
We are highly confident that the true effect lies close to that of the estimate of the effect. There is a wide range of studies included in the analyses with no major limitations, there is little variation between studies, and the summary estimate has a narrow confidence interval.
We consider that the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different. There are only a few studies and some have limitations but not major flaws, there are some variations between studies, or the confidence interval of the summary estimate is wide.
When the true effect may be substantially different from the estimate of the effect. The studies have major flaws, there is important variations between studies, of the confidence interval of the summary estimate is very wide.
LMA as a rescue device – Moderate quality evidence. Expert consensus and observational studies.
Wetsch WA, Schneider A, Schier R, et al. In a difficult access scenario, supraglottic airway devices improve success and time to ventilation. Eur J Emerg Med. 2015;22(5):374–376.
Benoit JL, Gerecht RB, Steuerwald MT, et al. Endotracheal intubation versus supraglottic airway placement in out-of-hospital cardiac arrest: a meta-analysis. Resuscitation. 2015;93:20–26.
Keller C, Brimacombe J, Bittersohl J, Lirk P, von Goedecke A . Aspiration and the laryngeal mask airway: three cases and a review of the literature. Br J Anaesth. 2004;93 (4) : 579-582.
Difficult Airway Society 2015 guidelines for management of unanticipated difficult intubation in adults. C. Frerk, V. S. Mitchell, A. F. McNarry, C. Mendonca, R. Bhagrath, A. Patel, E. P. O’Sullivan, N. M. Woodall and I. Ahmad, Difficult Airway Society intubation guidelines working group British Journal of Anaesthesia, 115 (6): 827–848 (2015) doi:10.1093/bja/aev371.
The purpose of this document is to provide health care professionals with key facts and recommendations for the diagnosis and treatment of patients in the emergency department. This summary was produced by the BC Emergency Medicine Network and uses the best available knowledge at the time of publication. However, healthcare professionals should continue to use their own judgment and take into consideration context, resources and other relevant factors. The BC Emergency Medicine Network is not liable for any damages, claims, liabilities, costs or obligations arising from the use of this document including loss or damages arising from any claims made by a third party. The BC Emergency Medicine Network also assumes no responsibility or liability for changes made to this document without its consent.
Last Updated Jan 19, 2022
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