• 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.

Pearls

• Insertion of the LMA cuff tip into the glottis may mimic laryngospasms with high airway pressures, slow expiration, and wheeze.

1. 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.

   
   

2. 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.

   
   

3. 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.

   
   

4. 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.