Novel Airway Devices: Spoilt for Choice?

Authors


Fourteen years ago, the options for maintaining the airway during anaesthesia were limited to the tracheal tube or the face mask combined with an oropharyngeal airway. As a new anaesthetic SHO, I recall seeing the laryngeal mask airway (LMA™; Intavent Orthofix, Maidenhead, UK) for the first time in 1989. Consultants looked askance at it, as they reached with their hypertropied forearms for the facemask or tracheal tube. However, despite initial scepticism, many ‘gave it a go’ and it was soon firmly established in anaesthetic practice. In the last 14 years, the LMA has been used in ≈ 150 million anaesthetics and there are over 2400 studies published on the device (Intavent Orthofix, personal communication).

The market for supraglottic airways is extensive. Five million general anaesthetics are administered each year in this country alone. The LMA is used for ≈ 65%, or 3.5 million cases (Intavent Orthofix, personal communication). At ≈ £2 per use this translates to a market for supraglottic airways in excess of £8 million per year. Of course, the UK represents only a fraction of the global market.

Today, the variety of supraglottic airways is bewildering (Fig. 1). There are currently five variations on the LMA and at least five other distinct supraglottic airways available [the Airway Management Device, AMD™, Nagor Ltd, Douglas, Isle of Man; the Combitube™, Tyco Healthcare Ltd, Gosport, UK; the Cuffed Oropharyngeal Airway, COPA™, Tyco Healthcare Ltd (production of the COPA has recently stopped and when remaining stocks are exhausted it will no longer be available); the Laryngeal Tube, LT®, VBM GmBH, Sulz, Germany; and the Pax™ oropharyngeal airway, Paxpress™, Vital Signs, Ltd, Barnham, UK]. At least four more supraglottic airways are in development and are likely to appear in the near future (the Laryngeal Tube Sonda, LTS®, VBM GmBH; the Streamlined Liner of the Pharynx Airway, SLIPA™, SLIPAmed UK, London, UK [1]; the Soft Seal Laryngeal Mask, Portex Ltd, Hythe, UK; and perhaps a new device from the manufacturers of the laryngeal mask airway). If all variants are included, there will soon be an array of 14 airways available for nonintubated patients. Eight of these devices have been introduced to the UK in the last three years, or are soon to be released. It is likely that several of these new devices will offer benefits over the classic laryngeal mask airway in certain clinical conditions; but which devices and when?

Figure 1.

Selection of airway devices.

How does the anaesthetist choose which device to use? Should it be the single-use device, the device that can be reused most often, the device that is cheapest, or the device that causes least trauma?

More fundamental questions also need addressing. Do all devices reliably maintain the airway? Do any of them protect the airway from regurgitated matter? Which devices allow safe and effective positive-pressure ventilation? What are the results of direct comparisons between the various devices? Unfortunately, in the majority of cases remarkably few data are available. The manner in which new medical devices are regulated in the UK may contribute to this.

The use of medical devices is controlled in European law by three European Directives [2]. The directive applicable to airway devices is the Medical Devices Directive (93/42/ EEC), implemented in 1994 and updated in 1998. The responsibility for ensuring medical devices do not threaten patients' health and safety is the responsibility of a ‘competent authority’. In the UK, this is the Secretary of State for Health [3]. The day-to-day running of this authority is delegated, in the UK, to the Medical Devices Agency (MDA). The MDA acts to ensure that devices sold in the UK satisfy the Medical Devices Directives. Its roles include giving advice, monitoring compliance with the regulations and, where necessary, enforcing them [3]. The MDA has the authority to insist on withdrawal of devices if it deems this appropriate [3]. The directives contain ‘Essential Requirements’ which manufacturers must fulfil before they can place a product on the European market. The MDA acts to ensure that devices sold in the UK comply with the Essential Requirements and thereby the Medical Devices Directives [3].

The CE mark is pivotal to marketing a device in the UK, and with European harmonisation, CE marking means the device may be marketed throughout the European Union without the need to meet additional national or local requirements [4,5]. The Essential Requirements laid out in the Medical Devices Directives must be fulfilled, in law, in order for a manufacturer to affix the CE mark to a device. Compliance with the regulations is the responsibility of the manufacturer; a manufacturer must sign a declaration of conformity before affixing the CE mark to the device. Affixing the CE mark means that ‘the manufacturer is satisfied that his product conforms with the relevant Essential Requirements for the Directives and that it is fit for its intended purpose’[5]. Furthermore, the CE mark is a statement by the manufacturer that the device satisfies ‘all the relevant legislation…including those relating to safety’[5].

There are four classes of medical device according to expected/potential risk to patients from the device. These range from class I (low risk) to class III (high risk) [6]. The requirements for testing before affixing the CE mark vary according to the class of the device. Supraglottic airway devices are class I or IIa. For low-risk (nonsterile class I) devices the manufacturer may make a self-assessment and declaration of complying with Essential Requirements. Once the device is registered with the MDA, the manufacturer can affix the CE mark. At a later stage, after going to market, the MDA may require the manufacturer to demonstrate compliance with the Essential Requirements. For medium- and high-risk devices (class IIa – most supraglottic airways, IIb and III) compliance must be demonstrated before the device is released to the marketplace. The certification process requires involvement of an independent assessor, a ‘notified body’, as a necessary part of the manufacturer's declaration of conformity to the MDA. The MDA designates notified bodies in the UK. The notified body performs a ‘conformity assessment’ which may involve determination as to whether the device satisfies relevant ‘standards’[5]. Standards may be ‘in house’, national, European or international. Through the process of harmonisation, European standards incorporate the Essential Requirements of the Directives. Therefore, products manufactured in line with harmonised European standards are assumed to meet the Essential Requirements [4]. For supraglottic airway devices, the relevant standards are those for the tracheal tube (BS EN 1782 ‘tracheal tubes and connectors’).

Do these assessments assess clinical effectiveness? The Medical Devices Directives aim to ensure that devices are manufactured to an acceptable standard of safety and quality and perform as intended by the manufacturer. However, the assessment process appears to focus more on the quality of the manufacturing process and product quality control, than on clinical effectiveness of the device. Although the affixing of a CE mark implies that the device is ‘fit for its intended purpose’[5], assessment of this appears to be left to the manufacturers, distributors and end users in the postproduction phase rather than the notified bodies.

Post-production obligations to the manufacturer include postproduction monitoring and reporting of adverse incidents. Manufacturers are legally bound to report ‘serious or potentially serious’ adverse incidents to the MDA through the ‘vigilance system’[7]. Such incidents include ‘malfunction of or deterioration in the characteristics and performance of a device…which might lead to death of a patient or deterioration in health’[7]. A voluntary scheme also operates under which users of a device may report problems to the Adverse Incident Centre (AIC). Surveillance after marketing is therefore formalised but how well this works is unclear.

Are there other agencies that might have a role? The Safety and Efficacy Register of New Interventional Procedures (SERNIP) was superceded by the Interventional Procedures Program of the National Institute for Clinical Excellence (NICE) in 1999. However, its remit is to evaluate new procedures, not new devices involving the same procedure (in this case, airway maintenance). Therefore, evaluation of supraglottic airways does not fall under its remit. (Dr Tom Dent, NICE, personal communication).

I contacted the companies involved in the manufacturing and distribution of all the devices mentioned above and asked for information regarding the number of patients on whom their device had been used prior to marketing, the number of papers on their product that had been published in peer-reviewed journals at the time of marketing and what was their method of postmarketing surveillance. Responses were provided by four of seven manufacturers.

The devices had been used in between 60 and 600 patients prior to marketing. The number of trials published in peer-reviewed journals at the time of launching the product varied from 0 to 12. One device launched in 2001 remains without published data. Only two of the seven devices currently available underwent comparison with the LMA in randomised controlled trials before marketing, and the largest of these involved just 60 patients [8].

Even when trials are available that inform clinicians of the devices, their interpretation is complicated by modifications of the devices after launch. The PAx, AMD and LT have all been modified in the last 18 months and the Combitube has also been altered in the last 5 years. Unless clinicians are experts in the field they may be unaware of changes when reading the literature. Although this does not make trials performed with the previous version of each device completely redundant, it does make interpretation of the limited data even more difficult. For one of the devices currently on the market, none of the three papers available relates to the device in its current form.

So how are devices evaluated at present? Typically, a representative provides a few consultants with samples of the new device. They ‘give it a go’ on a small number of patients and form an opinion. Throughout the country many hundreds of anaesthetists may go through this process, exposing perhaps thousands of patients to relatively untested devices, before a consensus is slowly reached. The quality of each evaluation will vary with the individual's practice and experience, and also random chance. Individuals may be swayed considerably by limited personal experience and new devices may be introduced without adequate evaluation of efficacy or safety, or conversely, rejected without due cause.

Is it still acceptable to evaluate new devices in such an ad hoc manner? Contrast this process with the introduction of a new drug which must pass through preclinical, phase I, phase II and phase III studies before being considered for release to the marketplace.

I have evaluated several new airway devices in the last year. The initial approach was to perform an extended pilot study of 100 patients to determine whether the device met the simple tests of efficacy and safety. A broad range of data was collected during device insertion, maintenance of anaesthesia, emergence and recovery. In one case [9], the initial results were published and the device performed well enough for us to initiate a randomised controlled trial compared with the laryngeal mask airway; between the trials, the device was modified. A second such airway evaluation was not published because of concerns by the Editorial Board of Anaesthesia about the ethics of the evaluation [10, 11]. Clearly ethical standards change over time as recently published guidance from the GMC makes clear [12]. Perhaps new airway devices and similar equipment should be subjected to a more formalised evaluation process, more akin to the development of drugs.

I would suggest that new devices should go through a three-stage process. Stage 1: devices are evaluated ‘on the bench’ and in specifically designed manikins. Stage 2: a rigorous pilot study takes place to determine whether the device is effective and safe. Stage 3: the device is compared in a randomised controlled trial against the current gold standard for the procedure it is expected to be used for (in the case of supraglottic airways, the ‘classic’ LMA™). Any alteration in the design of the device would entail restarting the process. CE marking might occur after stage 2 with marketing after stage 3. With the evolving changes in ethics, it is now clear that stages 2 and 3 require local ethics committee approval and written patient consent.

Although this editorial focuses on the introduction of new supraglottic airways, it might equally apply to other devices such as disposable laryngoscopes. It is ironic that the Department of Health has reacted to the potential risk of CJD by dictating to anaesthetists that they should use previously little-used disposable equipment [13]. The market appears to have been flooded with disposable laryngoscopes with negligible evidence of their safety [14]. The performance of several of the devices is less good than standard equipment [14] and this reflex reaction may have led to a tiny potential risk being replaced by an actual demonstrable risk. ENT surgeons know this to their cost [15].

As anaesthetists, we, and our patients, rely on our equipment. Progress in patient care will only be made through the development of new equipment, which relies on investment and innovation from manufacturers. Patients must be protected from untested devices that do not perform to an acceptable standard, but any evaluation programme should encourage and support equipment manufacturers. Any formal programme will need be carefully balanced to achieve both these goals.

Conflict of interest

Dr Cook has received an honorarium for presenting research to Intavent Orthofix Ltd, the manufacturers of the laryngeal mask airway and related devices.

Acknowledgements

I am grateful to the Medical Devices Agency, the Interventional Procedures Program of the National Institute for Clinical Excellence and the manufacturers of the supraglottic airways for their assistance during preparing this article. The Medical Device Agency wish me to state that this article represents my views and not those of the MDA.

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