The laryngeal mask airway (LMA) was first developed in the 1980s by Dr Archie Brain as an alternative device to endotracheal intubation, and was known as the LMA-Classic (cLMA). Cook (2006) reports an estimated 2 million patient uses worldwide, with minimal complication rates reported. However, the author does acknowledge that these figures are now outdated and the increased use of LMAs both in and out of hospital will have seen this figure climb sharply. A prototype of the cLMA was developed and patented, with additional patents secured for component parts to the cLMA by Dr Brain. However, the original patent expired in the early 2000s, and since a number of other devices have been developed, based on the concept of the original LMA (Cook, 2006) and these devices are now grouped together as supraglottic airway devices (SGAs). This article aims to critically analyse the literature surrounding a range of SGA’s that are now available on the market since Dr Brain's original development, whilst considering anecdotal experiences of the author. Consideration will be given to the various reusable and disposable devices for cost effectiveness, speed of insertion, ease of use, durability and cross contamination.
The author acknowledges the wide range of SGAs that are available, and as such not all can be considered in this article. Particular attention has been drawn to the I-Gel, conventional LMA, intubating LMAs and pro-seal LMAs, based upon anecdotal uses by the author both in and out of hospital. The I-Gel is a semi rigid single use device, with a non-inflatable mask made from a soft jelly like material, with the added benefit of a gastric port, through which gastric aspiration can be undertaken. The gel-based mask will conform to the patient's anatomy once cited in the larynx. A range of sizes are available, with a cost of around £10 per device. The pro-seal (also known as LMA-supreme) is similar to the I-Gel in containing a gastric port which, when inserted sits directly in the oesophagus allowing gastric aspiration and decompression. These devices contain an integral bite block and inflatable cuff, and again are available in a range of sizes. The average cost of a single use pro-seal LMA is £15. Various names now exist for what is referred to as the original LMA, such as LMA-classic, LMA-unique and conventional LMA. These devices are based upon the original design by Dr Brain, incorporating an inflatable cuff, which sits in the larynx, and an airway port. These devices have no gastric port, although some types contain an integral intubation tube, which allows the LMA to be cited, followed by an endotracheal tube being passed through the vocal cords, without the need for direct laryngoscopy. The average price for single patient use LMAs is similar to that of the I-Gel, at £10. The author has not been able to find a public sector supplier of reusable LMA’s, despite devices such as the pro-seal and cLMA being available and used within UK healthcare systems, and as such no price comparison between single patient use and reusable devices can be made.
The difference between ease and speed of insertion has been the subject of scrutiny throughout the literature for some time. A number of studies identify that there is no comparable difference for ease of use and the speed of insertion between single patient use and reusable SGAs (Shafik et al, 2006; Teoh and Lim, 2007; Bell et al, 2012). However, these particular studies are all centred on devices such as the cLMA and LMA-unique, where the main difference is the material used to construct the device (reusable silicone versus disposable PVC). In a study of nonexperienced operators, Ragazzi et al (2012) found that there was little difference for ease of use and speed of insertion between the I-Gel and LMA-supreme. In contrast to this, Castle et al (2010) report significantly different findings for speed of insertion between the I-Gel and two other single patient use SGAs. The average time taken to insert the I-Gel was 12.3 seconds, compared to 22.4 seconds and 33.8 seconds for the other SGAs (Castle et al, 2010). When analysing this data, it must be considered that Castle et al (2010) were limited to an airway mannequin, which due to materials used, can cause an element of friction when inserting a silicone or PVC-based airway, thus potentially prolonging time to insertion. Between all of the identified studies, there is no mention of insertion method, which from anecdotal experience can significantly impact the time taken. For example, SGA insertion is often aided by the use of a jaw thrust, or in certain patients, a laryngoscope. Evidence suggests that all of the devices remain easy to use despite the extent of airway management experience (Castel et al, 2006).
Woods and Meek (2005) report a case of failure when using a single patient use LMA during routine anaesthesia. It was found that the adhesion between the mask portion and tube had become damaged, leading to a leak of air during the ventilation cycle (Woods and Meek, 2005). This appeared to be an isolated case in the single patient use devices, and improvements in bond strength testing have been implemented as a precautionary measure. However, the bond strengths, adhesive seals and overall durability of reusable devices are also questioned and subjected to rigorous testing. In general, manufacturer guidelines stipulate that reusable devices should be used no more than 40 times, which includes the cleaning and sterilisation phases (LMA North America Inc, 2004). This is primarily due to the degradation that can occur, affecting the integrity of the product and component parts such as structural and tear strength, adhesive seals and cuff inflation. However, Goodman et al (2008) report similar findings to manufacturers, such as decreasing tear strength and elongation of the device. Despite these findings, the authors conclude that the materials were suitable for over 100 patient uses, and as such can be considered safe (Goodman et al, 2008). Manufacturers still advocate the 40 use principal, but consideration should be given to the findings reported above. The cost implications must also be considered here. For example, in an acute hospital setting, a reusable device with over 100 uses would be more cost effective than purchasing 100 single patient use devices.
There is an inherent risk associated with any reusable medical product, which is also apparent in airway devices, thus being cross contamination. Lu (2004) identifies that due to the nature of reusable products, blood and protein particulate matter readily adheres to the silicone surfaces, thus creating potential for cross contamination between patients. Manufacture guidelines stipulate stringent cleaning procedures, with sterilisation by autoclave at 134 °C (Richards et al, 2006) to eliminate the risks of cross contamination. Despite such processes, both Lu (2004) and Richards et al (2006) have identified several cases of reusable LMA devices taken from hospital store rooms to be protein stained. Richards et al (2006) go on to identify that cross contamination is likely to occur where batches of LMAs are cleaned together, with a reduction in protein staining when cleaning in isolation. However, it can be argued that any degree of protein staining, no matter how devices are cleaned, poses a varying degree of risk to the patient. Despite this, there is no documented evidence of infection/cross contamination as a direct result from the use of an SGA, and more research is required to establish the degree of risk to patients (Richards et al, 2006). The recommendations made by Lu (2004) for the increased use of single patient use devices are supported by the author, thus reducing the risk of cross contamination. Anecdotal evidence suggests that ambulance services in the UK only stock and utilise single patient use SGAs.
To conclude, the author has found varying advantages and disadvantages of both reusable and single patient use supraglottic airway devices, whilst exploring a number of types of devices that are available on the market. Through anecdotal experience of using the various types of SGAs, the author does not advocate one particular device over another, and is of the belief that airway practitioners should consider the evidence available and follow local guidelines when using such devices. Those purchasing SGAs should liaise with the practitioners who are using the devices, whilst considering cost implications and other evidence available surrounding the impact of cross contamination. The SGA airway remains an effective airway device, and should continue to be used both in and out of hospital.