The laryngeal mask airway is a supraglottic airway device invented by Archie Brain

Archie Brain

Archie Brain is a British anesthetist best known as the inventor of the laryngeal mask airway or LMA. The LMA is used worldwide in elective anesthesia and emergency airway management.-Biography:...

, a British anaesthetist.

Description

Laryngeal masks consist of a tube with an inflatable cuff that is inserted into the pharynx

Human pharynx

The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...

. Laryngeal mask airways come in a variety of sizes ranging from large adult (size 5) to infant (size 1). The laryngeal mask 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

Combitube

The Combitube is a blind insertion airway device often used in the pre-hospital, emergency setting. It is designed to facilitate the tracheal intubation of a patient in respiratory distress. It consists of a cuffed, double-lumen tube that is inserted into a the patient's airway facilitating...

 and the King Laryngeal tube (LT). A newer generation of the laryngeal mask 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. 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 is seated over the pyriform fossae

Piriform sinus

On either side of the laryngeal orifice is a recess, termed the piriform sinus , which is bounded medially by the aryepiglottic fold, laterally by the thyroid cartilage and hyothyroid membrane...

. 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

Stethoscope

The stethoscope is an acoustic medical device for auscultation, or listening to the internal sounds of an animal body. It is often used to listen to lung and heart sounds. It is also used to listen to intestines and blood flow in arteries and veins...

, by presence of end tidal carbon dioxide

Capnography

Capnography is the monitoring of the concentration or partial pressure of carbon dioxide in the respiratory gases. Its main development has been as a monitoring tool for use during anaesthesia and intensive care. It is usually presented as a graph of expiratory plotted against time, or, less...

 and by monitoring the degree and pressure at which the air leaks around the mask in the oropharynx.

Indications

Laryngeal masks are used in anesthesia

Anesthesia

Anesthesia, or anaesthesia , traditionally meant the condition of having sensation blocked or temporarily taken away...

 and in emergency medicine

Emergency medicine

Emergency medicine is a medical specialty in which physicians care for patients with acute illnesses or injuries which require immediate medical attention. While not usually providing long-term or continuing care, emergency medicine physicians diagnose a variety of illnesses and undertake acute...

 for airway management

Airway management

In cardiopulmonary resuscitation, anaesthesia, emergency medicine, intensive care medicine and first aid, airway management is the process of ensuring that:# there is an open pathway between a patient’s lungs and the outside world, and...

. The main use of the laryngeal mask is in elective anaesthesia, however it is also useful in situations where manipulation of the head or neck to facilitate endotracheal intubation

Tracheal intubation

Tracheal intubation, usually simply referred to as intubation, is the placement of a flexible plastic or rubber tube into the trachea to maintain an open airway or to serve as a conduit through which to administer certain drugs...

 is difficult (e.g.: 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. The laryngeal mask may be used for surgical procedures in any position, including supine

Supine position

The supine position is a position of the body: lying down with the face up, as opposed to the prone position, which is face down, sometimes with the hands behind the head or neck. When used in surgical procedures, it allows access to the peritoneal, thoracic and pericardial regions; as well as the...

, decubitus

Decubitus

Commonly used in medicine, the word decubitus is used to mean "lying down". It is derived from the Latin verb “decumbere” meaning "to lie down"....

, sitting

Sitting

Sitting is a rest position supported by the buttocks or thighs where the torso is more or less upright.- Sitting on the floor :The most common way of sitting on the floor involves bending the knees...

, Trendelenburg

Trendelenburg position

In the Trendelenburg position the body is laid flat on the back with the feet higher than the head by 15-30 degrees, in contrast to the reverse Trendelenburg position, where the body is tilted in the opposite direction. This is a standard position used in abdominal and gynecological surgery...

, lithotomy

Lithotomy position

The lithotomy position is a medical term referring to a common position for surgical procedures and medical examinations involving the pelvis and lower abdomen, as well as a common position for childbirth in Western nations...

, or prone

Prone position

The term means to lie on bed or ground in a position with chest downwards and back upwards.-Etymology :The word "prone," meaning "naturally inclined to something, apt, liable," has been recorded in English since 1382; the meaning "lying face-down" was first recorded in 1578, but is also referred to...

 positions. However, anesthetic practice in the United States has largely limited its use to the supine position, whilst European anesthesiologists report its common use in lateral and even prone position cases.

Contraindications

The laryngeal mask airway does not protect the lungs from aspiration

Pulmonary aspiration

Pulmonary aspiration is the entry of material from the oropharynx or gastrointestinal tract into the larynx and lower respiratory tract...

, making them unsuitable for patients at risk for this complication.

Adverse effects

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 have included recent improvements such as channels for gastric suction (LMA ProSeal(tm), LMA Supreme(tm)), and modification to the laryngeal mask to allow it to guide endotracheal tubes through its respiratory gas tubing into the larynx (ILMA(R) - Intubating Laryngeal Mask Airway), thus protecting the patient against aspiration of gastric contents with the balloon on the end of the endotracheal tube (LMA Fastrach(tm), Cookgas Air-Q).

Further reading

• Brain AIJ, Denman WT, Goudsouzian NG (1999). Laryngeal Mask Airway Instruction Manual. San Diego, Calif: LMA North America Inc.
• Brimacombe R, Brain AIJ, Berry A (1997). Nonanesthetic uses. In: The Laryngeal Mask Airway: A Review and Practice Guide. Philadelphia, Pa: Saunders; pp. 216–77.
• Rothrock J. Alexander's - Care of the Patient. Missouri; Saunders; 2003; 236.
• Complications: p316-7 http://medind.nic.in/iad/t05/i4/iadt05i4p308.pdf
• Guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2000; 102 (suppl 1): I95–I104.[Medline]

External links