Laryngeal Mask Airway (LMA)
OVERVIEW
- LMA is an acronym for Laryngeal Mask Airway
- a type of extraglottic airway device aka supraglottic airway device (SAD)
USES
- rescue airway in a failed intubation
- facilitate blind insertion of bougie or ETT into trachea
- facilitate blind insertion of bronchscopic assisted airway control
- improve oxygenation as part of rapid sequence airway approach
- ventilation during elective anaesthesia to fasted patients with low risks of regurgitation
DESCRIPTION
Parts:
- shaft (tube)
- proximal 15 mm connector
- distal end with broad elliptical inflatable cuff — upper smooth surface to prevent pharyngeal secretions entering the larynx and an under surface with an orifice with linear bars that sits over the larynx to create a seal
- pilot balloon
Types:
- Reusable (silicon)
- Intubating LMA with endotracheal tube (e.g. FastTrackTM) (disposable)
- LMA with gastric suction channel (e.g. ProSealTM) (disposable)
Sizes:
- 0 (infant) to 6 (large adult)
- size 3 (females) or 4 (males) commonly used in adults
| Mask Size | Weight (kg) | Age (yr) | LMA length (cm) | LMA Cuff Vol (mL) | Largest ETT^ (mm) |
| 1 | <5 | <0.5 | 10 | 4 | 3.5 |
| 1.5 | 5-10 | <1 | 10 | 5-7 | 4 |
| 2 | 6.5-20 | 1-5 | 11.5 | 7-10 | 4.5 |
| 2.5 | 20-30 | 5-10 | 12.5 | 14 | 5 |
| 3 | 30-60 | 10-15 | 19 | 15-20 | 6 |
| 4 | 60-80 | >15 | 19 | 25-30 | 6.5 |
| 5 | >80 | >15 | 19 | 30-40 | 7 |
METHOD OF INSERTION/ USE
- blindly inserted to form a low pressure seal over the laryngeal inlet
LMA
- sniffing position
- partially inflated cuff
- lubricate mask surface
- aperture facing towards laryngeal inlet or posteriorly with a 180 degrees twist once behind tongue
- inflate cuff with 20-40mL of air
Standard LMA insertion
ILMA
- insert with aperture facing laryngeal inlet
- test ventilate
- feed ETT through inlet followed by obturator
- slide LMA while ensuring ETT stays in trachea
- confirm position with ETCO2
- LMA can either be left in situ stabilising the ETT, or can be removed leaving just the ETT in situ
CONTRAINDICATIONS
- poor mouth opening
- potential pharyngeal/laryngeal pathology
- poor pulmonary compliance
- high airway resistance
RODS predicts difficulty with extra-glottic airway use
- Restricted mouth opening
- Obstruction
- Distorted airway
- Stiff lungs or c-spine
COMPLICATIONS
- inability to achieve a seal and ventilate (can be assisted by deepening the level of anaesthesia, inserting under direct vision with a laryngoscope, partially inflating the cuff, flexing the lower spine with chin lift)
- regurgitation and aspiration
- gas insufflation
- partial airway obstruction (mask misplacement)
- shaft kinking
- malposition
- dislodgement
- laryngospasm
- cough
- trauma to the upper airway (e.g. bleeding, dislodgement of teeth)
OTHER INFORMATION
- Invented by Archie Brain (1942 – ), a British Anaesthetist in 1983
- LMA works best with an under-inflated mask
Advantages
- provide rapid protection of airway in the field
- technically easier to insert than ETT
- some models provide a gastric port
Disadvantages
- non-definitive airway protection and patency
- difficult ventilation if high airway pressures
References and Links
Journal articles
- Cook T, Howes B. Supraglottic airway devices: recent advances. Continuing Education in Anaesthesia, Critical Care & Pain. 2010; 11(2): 56-61
- Ramaiah R, Das D, Bhananker SM, Joffe AM. Extraglottic airway devices: A review. Int J Crit Illn Inj Sci [serial online] 2014
FOAM and web resources
- AirwayCam.com — Laryngeal Masks
- AirwayCam.com — Other Supraglottic Devices
- EMCrit Podcast 43 – Laryngeal Airways with Daniel Cook, MD (Part I)
- EMCrit — Video for Podcast 43 – Inserting the Air-Q
- EMI — Anatomy for Emergency Medicine #16 – The LMA as a murder weapon?
- EP Monthly — Second Gen. Laryngeal Mask Airway (LMA): Is It Time For You to Upgrade? (by Rich Levitan)
- ScanCrit.com — LMA in Neonate Resus
- Archie Ian Jeremy Brain (1942 – )
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Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.
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