The laryngeal mask is a device for supporting and maintaining the airway without tracheal intubation. The laryngeal mask may be used as an aid to intubation; it is positioned in the normal fashion and used as a guide for blind intubation by passing an appropriately sized endotracheal tube (ETT) through the laryngeal mask (laryngeal mask/ETT sizes: 1/3.5; 2/4.5; 3/5.0; 4/6.0 cuffed; 5/7.5 cuffed). In some cases, the ETT will be guided directly into the trachea. Alternatively, the laryngeal mask may be used to guide passage of a fibreoptic bronchoscope into the trachea, thus allowing intubation of the trachea.
Points of note
- The distal end of the airway is lodged against the inferior constrictor of the pharynx
- Cricoid pressure may prevent correct placement
- Usage of a laryngeal mask is associated with a higher positive end-expiratory pressure than is present with an ETT
- The laryngeal mask was developed by Dr Archie Brain
Figure 1: Standard laryngeal mask airway (single-use)
Figure 2: MRI-compatible laryngeal mask (single-use)
1: Neonates <5 kg, <4 ml air
11/2: Children 5-10 kg, <7 ml air
2: Children 10-20 kg, <10 ml air
2 1/2: Children 20-30 kg, <14 ml air
3: Children 30-50 kg, <20 ml air
4: Small/normal adults <30 ml air
5: Normal/large adults <40 ml air
ST, if written on the tube, stands for short.
Uses of the laryngeal mask
1. Inhalational anaesthesia
2. Maintaining airway during difficult intubation
3. Emergency management of airway in failed intubation
The laryngeal mask is autoclaved between uses. A maximum of 40 uses is recommended (i.e. 39 re-uses). Single-use PVC versions are available, as shown above.
Reinforced laryngeal masks
Also available with reinforced tubes to prevent kinking.
[i] Laryngeal mask airway. Indications and contraindications. Benumof, JL. Anesthesiology 1992; 77(5): 843-6
[ii] Laryngeal mask airway and the ASA difficult airway algorithm. Benumof, JL. Anesthesiology 1996; 84(3): 686-99