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
CCC Airway Series
Emergencies: Can’t Intubate, Can’t Intubate, Can’t Oxygenate (CICO), Laryngospasm, Surgical Cricothyroidotomy
Conditions: Airway Obstruction, Airway in C-Spine Injury, Airway mgmt in major trauma, Airway in Maxillofacial Trauma, Airway in Neck Trauma, Angioedema, Coroner’s Clot, Intubation of the GI Bleeder, Intubation in GIH, Intubation, hypotension and shock, Peri-intubation life threats, Stridor, Post-Extubation Stridor, Tracheo-esophageal fistula, Trismus and Restricted Mouth Opening
Pre-Intubation: Airway Assessment, Apnoeic Oxygenation, Pre-oxygenation
Paediatric: Paediatric Airway, Paeds Anaesthetic Equipment, Upper airway obstruction in a child
Airway adjuncts: Intubating LMA, Laryngeal Mask Airway (LMA)
Intubation Aids: Bougie, Stylet, Airway Exchange Catheter
Intubation Pharmacology: Paralytics for intubation of the critically ill, Pre-treatment for RSI
Laryngoscopy: Bimanual laryngoscopy, Direct Laryngoscopy, Suction Assisted Laryngoscopy Airway Decontamination (SALAD), Three Axis Alignment vs Two Curve Theory, Video Laryngoscopy, Video Laryngoscopy vs. Direct
Intubation: Adverse effects of endotracheal intubation, Awake Intubation, Blind Digital Intubation, Cricoid Pressure, Delayed sequence intubation (DSI), Nasal intubation, Pre-hospital RSI, Rapid Sequence Intubation (RSI), RSI and PALM
Post-intubation: ETT Cuff Leak, Hypoxia, Post-intubation Care, Unplanned Extubation
Tracheostomy: Anatomy, Assessment of swallow, Bleeding trache, Complications, Insertion, Insertion timing, Literature summary, Perc. Trache, Perc. vs surgical trache, Respiratory distress in a trache patient, Trache Adv. and Disadv., Trache summary
Misc: Airway literature summaries, Bronchoscopic Anatomy, Cuff Leak Test, Difficult airway algorithms, Phases of Swallowing
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 – )
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the Clinician Educator Incubator programme, and a CICM First Part Examiner.
He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.
His one great achievement is being the father of three amazing children.
On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.
| INTENSIVE | RAGE | Resuscitology | SMACC