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The Laryngeal Mask Airway

The First Supraglottic

An informative graphic detailing the Laryngeal Mask Airway (LMA), including its components and size guide for different patient weights with labeled parts.

Background

The laryngeal mask airway (LMA) was the first supraglottic device. It was discovered by Dr. Archibald Brain in 1981 as an alternative to FMV & ETT.

It is designed to sit over the laryngeal inlet and provide a hands-free conduit for oxygenation and ventilation without passing through the vocal cords. It occupies the middle ground between face-mask ventilation, basic airway adjuncts (OPA/NPA) and endotracheal intubation.

It is widely used in anesthesia, emergency airway management, and resuscitation as both a primary airway device and a rescue option when face mask ventilation or intubation is unsuccessful.

Here is a quick overview from ABCs of Anesthesia:

Description

The LMA Classic consists of:

  • Airway tube: Connects to a bag-valve device or ventilator.
  • Elliptical mask/cuff: Inflatable (in many models) and designed to seat over the glottic opening.
  • Pilot balloon (inflatable types): Indicates cuff inflation status.
  • 15 mm connector: Standard airway circuit connection.
Diagram and description of a Laryngeal Mask Airway (LMA) showing its components including the airway aperture, inflatable cuff, tube shaft, syringe port, 15mm connector, and pilot balloon with explanations of their functions.

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Modern generations of the LMA vary significantly and may include:

  • Second-generation designs with gastric drainage channels
  • Improved seal pressures
  • Preformed or anatomically curved shafts
  • Disposable and reusable options
  • Wide, patent ventilation channels without bars to allow for inline ETT delivery,

Because performance characteristics vary, clinicians should be familiar with the specific device used in their institution.

Infographic titled 'Evolution of the Laryngeal Mask Airway' detailing the development of laryngeal mask devices through different generations from 1981 to 2015. It includes images and descriptions of first and second generation models, their materials, functionality, and additional features.

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Second-generation LMAs with gastric access improve aspiration risk mitigation but do not eliminate it. Clinical judgment is essential.

Sizing

LMA size selection is generally based on patient weight (check manufacturer guidance). Typical adult ranges:

  • Size 3: small adults (~30–50 kg)
  • Size 4: average adults (~50–70 kg)
  • Size 5: large adults (~70–100 kg)
  • Size 6: very large adults (>100 kg)

Using too small a device results in poor seal and leak. Too large increases trauma risk and insertion difficulty.

Always confirm the specific sizing table for the device you are using.

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Infographic detailing the King Airway, a supraglottic airway device, with labeled parts and a size chart for patient criteria.

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