Also, during anaesthesia upper airway collapse associated with the loss of muscle tone is a distinct possibility. The operator must simultaneously elevate the jaw while pressing backwards against the face. Usually insertion of a Guedel airway is required to bypass obstruction of the airway by the tongue.

To achieve a good seal with an endotracheal tube, pressure is applied to the epithelial surface. Important and highly specified functions are thus somewhat compromised by the penetration of the vocal cords: effective coughing and swallowing are rendered impossible. The upper airway structure is distorted and an unwanted reflex response is provoked.

According to Dr. Brain, and other leading anesthesiologists, an artificial airway should have the following fundamental characteristics:

It should overcome airway obstruction rapidly and easily.
It should be atraumatic, even when used by the unskilled.

Clearly, neither the facemask nor the endotracheal tube can meet these simple yet vital criteria.

Early development work on the laryngeal mask airway

Dr. Brain carried out early work on the laryngeal mask airway in 1981 while he was a lecturer at the London Hospital of Anaesthetics. Part of Dr. Brain`s clinical commitment included giving dental anesthetics to outpatients. The method of choice at this institution for simple extractions was to administer a volatile aesthetic gas through a McGill circuit attached to a Goldman dental mask. A Goldman dental mask is a nasal mask made with a detachable, black rubber cuff.

Dr. Brain`s interest in the human airway led him to make plaster of Paris casts of a cadaver pharynx, in order to explore the actual and potential space in the glottic area.

Dr. Brain noticed the similarity between the general size and shape of the detached Goldman mask cuff and the available size and space in the pharynx as defined by his plaster of Paris moulds. The next step, which resulted in Dr. Brain`s first prototype of the laryngeal mask airway, was to incorporate a 10 mm plastic tube into the floor of the mask in such a way that the tube emerged behind the wider posterior end of the mask.

As a result of a first, successful experience in a male patient with his initial prototype in 1981, Dr. Brain proceeded to assemble three more prototypes in order to set up his first pilot study. This pilot study was carried out at the London Hospital after obtaining ethical committee approval. The results convinced Dr. Brain that considerable further work was justified. In this first study, Dr. Brain obtained a clear airway in all 23 patients he studied, and positive pressure ventilation was successful in 100% of the 16 female patients in whom it was used to facilitate laparoscopy. Although the mask appeared to work better in females than male patients, this came as no surprise to Dr. Brain, since at this stage only one size could be manufactured for use in this initial study. Through his study with cadavers, Dr. Brain knew that the physiology of male and female patients varied a great deal, and he surmised that either obstructions or leaks were occurring with certain patients.

Dr. Brain concluded that the smaller size would be more suitable for female patients than for male. Indeed, both obstructions and leaks occurred more frequently with the male patients in this first study. It took some time for Dr. Brain to find the correct size larynx to use in developing a larger laryngeal mask airway for the male patient.

Commercial work on the laryngeal mask airway

By the end of 1985 it was clear that no further progress could be made without obtaining a more appropriate mask design than was currently being used. Over 70 laryngeal masks had been made from a Goldman cuff. However, manufacture of the Goldman dental mask had been discontinued. At this time, commercial interest was aroused and the Dunlop Rubber Co. made some silicone mask prototypes. Dr. Brain noted that in the course of cutting apertures in the silicone mask to attach the tube, it was easy to incorporate a central or a double bar in the lumen - an imitation of a previous design in which a bar had been welded across the aperture of a Goldman mask.

The purpose of these aperture bars was to prevent a large epiglottis from falling into the aperture, blocking it and occluding the airway. The aperture bars needed to be flexible enough so an endotracheal tube could pass through them and push them aside and yet they needed to be firm enough to withstand the pressure of an epiglottis.

Using the Dunlop mask immediately improved the smoothness of insertion and as experience was gained, it became clear that there was another advantage – the cuff could be deflated to form a wafer-thin leading edge making collision with the epiglottis less likely. Gradually, the use of the introducer tool was discontinued as Dr. Brain realized that the insertion technique was more critical to success than insertion equipment.

The Dunlop cuff was greatly superior to previous prototypes with regard to insertion, but it could not be easily inflated to an adequate size for adults. This encouraged the use in children for the first time and it proved possible to obtain a clear airway without trauma in children above 24 kg.

The desire to make different sizes would involve making molds. Dr. Brain completed over 60 different designs and tested them clinically. By September of 1986 extensive testing of latex and silicone variance had shown that Dr. Brain had made much progress in the design and development of the laryngeal mask.

Commercial introduction of the LMA Classic™

Work and experimentation with the laryngeal mask continued through 1986 and into 1987. New developments and prototypes were being refined and trials were ongoing during this period of time. By December of 1987 the first commercially made laryngeal mask, the LMA Classic™, was ready for trial, and the initial results exceeded expectations. The silicone cuff was slightly larger than the improved Dunlop cuff, but was more elastic, making it softer and providing a more extensive contact with the laryngeal perimeter.

By January of 1988 it was possible to finalise the design and order three other sizes, the dimensions of which were based on prototypes made in either latex or silicone by Dr. Brain. The first hospital to purchase the LMA Classic™ was the Royal East Sussex Hospital, Hastings, where it has been in use from mid-1988. Twelve months later more than 500 other U.K. hospitals were using the device. Currently, the LMA™ airway product range is available throughout the world and has been used in over 300 million surgeries.

In the United States, the FDA cleared the LMA Classic™ for marketing in February 1991. By that time many forward-thinking anesthesiologists had become aware of the device and its use in Europe and around the world. Before it was cleared for marketing by the FDA, several U.S. pioneering anesthesiologists acquired the LMA Classic™ either through their contacts in the U.K. or through colleagues in Canada.

In 1992, The Laryngeal Mask Company concluded arrangements for the commercial sale of the LMA Classic™ in the United States.

LMA Protector Airway with Cuff Pilot Technology - Fact Sheet

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