Laryngeal mask airway

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The laryngeal mask airway is a supraglottic airway device invented in 1983 by the British anaesthetist, Dr. Archie Brain.

[edit] Use

Laryngeal masks are used in anesthesia and in emergency medicine for airway management. They consist of a tube with an inflatable cuff that is inserted into the pharynx. They cause less pain and coughing than an endotracheal tube, and are much easier to insert. However, a standard laryngeal mask airway does not protect the lungs from aspiration, making them unsuitable for patients at risk for this complication.

The main use of LMAs is in elective anaesthesia, however it is also useful in situations where manipulation of the head or neck to facilitate endotracheal intubation is difficult (eg: trapped patient or potential cervical spine injury) or when intubation is unsuccessful. It is not inserted as far as an endotracheal tube (it sits in the pharynx, and thus does not need to be inserted into the trachea), and supports both spontaneous and artificial ventilation. It is popular in day case surgery.

However, unlike an endotracheal tube, a laryngeal mask cannot protect the airway or lungs from aspiration of regurgitated material, and deep (subglottic) suctioning cannot be performed through the mask. Steps to improve the ability of the laryngeal mask airway (LMA) have included recent improvements such as channels for gastric suction (LMA Proseal, LMA Supreme), and modification to the LMA to allow it to guide endotracheal tubes through its respiratory gas tubing into the larynx (ILMA - Intubating Laryngeal Mask Airway), thus protecting the patient against aspiration of gastric contents with the balloon on the end of the endotracheal tube (LMA Fastrack, Cookgas Air-Q).

[edit] Guide to use

Laryngeal mask airways come in a variety of sizes ranging from large adult (LMA size 6) to infant (size 0). The LMA functions as a "peripharyngeal sealer," in contrast to another category of supraglottic airways which are "base on tongue sealers," such as the Esophageal-Tracheal Combitube and the King Laryngeal tube (LT). A newer generation of the LMA actually utilizes BOTH airway sealing mechanisms (peripharyngeal sealing and base of tongue sealing), and they result in higher average seal pressures during controlled and assisted ventilation of the patient. These models are the LMA Proseal/LMA Supreme and the Cookgas Air-Q.

The cuff of the mask is deflated before insertion and lubricated. The patient is sedated or fully anaesthetized if conscious, and their neck is extended and their mouth opened widely. The apex of the mask, with its open end pointing downwards toward the tongue, is pushed backwards towards the uvula. The cuff follows the natural bend of the oropharynx, and its long walls come to rest over the pyriform fossae. Once placed, the cuff around the mask is inflated with air to create a tight seal. Air entry is confirmed by listening for air entry into the lungs with a stethoscope, by presence of end tidal carbon dioxide and by monitoring the degree and pressure at which the air leaks around the mask in the oropharynx.

Besides from the supine, the laryngeal mask airway (as with an endotracheal tube) may be used for procedures in several surgical positions. However, anesthetic practice in the United States has largely limited its use to the suspine position, whilst European Anesthesiologists report its common use in lateral and even prone position cases.

The laryngeal mask airway should not be sterilised with glutaraldehyde (CIDEX) and can be reused up to 40 times with proper autoclaving. There is potential for transmission of slow viral diseases with LMA usage, and thus the use of disposable LMAs is strongly recommended.

[edit] References

• Guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2000; 102 (suppl 1): I95–I104.[Medline]
• Asai T, Morris S. The laryngeal mask airway: its features, effects and role. Can J Anesthesiol. 1994; 41: 930–960.[Abstract]
• Brain A, Denman WT, Goudsouzian NG. Laryngeal Mask Airway Instruction Manual. San Diego, Calif: LMA North America Inc; 1999.
• Brimacombe R, Brain AIJ, Berry A. Nonanesthetic uses. In: The Laryngeal Mask Airway: A Review and Practice Guide. Philadelphia, Pa: Saunders; 1997: 216–277.
• Rothrock J. Alexander's - Care of the Patient. Missouri; Saunders; 2003; 236.
• Complications: p316-7 http://medind.nic.in/iad/t05/i4/iadt05i4p308.pdf