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E-letters: Electronic letters published:
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Difficulty with the use of the disposable Ambu LMA
- NAMITA ARORA, B T AYORINDE (2 May 2006)
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Re: Re-usable or single use laryngeal masks?
- Tim M Cook (26 March 2006)
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Re-usable or single use laryngeal masks?
- Baha Al-Shaikh, Andre van Zundert (21 March 2006)
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Patient safety and the introduction of regulations for supraglottic airways.
- Donald M Miller (20 March 2006)
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The classic laryngeal mask airway: a tried and tested airway. What now?
- Tim M Cook (1 March 2006)
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The classic laryngeal mask airway: a tried and tested airway. What now?
- Donald M Miller (21 February 2006)
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NAMITA ARORA , B T AYORINDE
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Editor-We read with interest the editorial by Cook on classic laryngeal mask airway 1 and wish to report our experience following the introduction of the disposable AMBU Laryngeal Mask Airway ( Ambu Laryngeal Mask, Ambu Inc, linthicum, USA) in our hospital. According to the manufacturer, the Ambu Laryngeal Mask Airway (LMA) features a special curve that replicates human anatomy. The unusual shape of this LMA is meant to aid insertion and give flexibility needed to adapt to individual anatomical variance and a wide range of head positions. As a part of our drive to use disposable LMAs in our hospital, we evaluated the AMBU LMA in July 2005. Over the next three to four months, we commonly faced problems with difficulty in maintaining good placement and obtaining adequate seal, especially if the patient’s anatomy was slightly deviant from standard anatomy. On several occasions during surgery, the anaesthetist had to re-site the LMA with the aim of getting better position or had to try different sizes in order to get an adequate seal. On few occasions, we even had to revert back to endotracheal intubation. We found that a majority of the anaesthetists in our hospitals had problems with positioning and flexibility with Ambu LMA as compared to the classic LMA (cLMA) (LMA Classic TM , Intavent, Orthofix, Maidenhead, UK). The consensus was that the product was not living up to the claimed efficacy and ease of use as proposed by the manufacturer and was not acceptable for regular use as a standard LMA in our hospital. We therefore had to abandon the use of this product. A review of literature found a multicentre study on the Ambu LMA carried out on 180 patients which concluded that the device was easy to insert and provided safe and efficient seal during positive pressure ventilation in non-paralyzed patients scheduled for elective surgery 2. Another unpublished study concluded that the Ambu LMA had an equivalent efficacy when compared with the cLMA in patients with immobilized cervical spine 3. The editorial by Cook noted that there is an increasing recent trend towards the introduction of inexpensive competitors to the cLMA with the decision as which LMA to use being taken out of hands of anaesthetists by managers and purchasers in many hospitals. This editorial also noted that there is paucity of evidence evaluating the efficacy and safety of these new laryngeal masks before their introduction into clinical practice. Our experience with Ambu LMA supports this view that further studies are necessary to evaluate the place of Ambu LMA and similar devices in the management of airway. N Arora* B T Ayorinde Leicester, UK E-mail: namitaarora@hotmail.co.uk References: 1. Cook TM. The classic laryngeal mask airway: a tried and tested airway. What now? British Journal of Anaesthesia. 2006 Feb; 96(2): 149-152 2. Carin A, Hagberg, Frank Samsoe Jensen et al. A Multicenter Study of the Ambu Laryngeal Mask in Non-paralysed Anaesthetized Patients. Anesth Analg. 2005 Dec; 101(6):1862-6. 3. Gernoth C, Jandewerth O, Contzen M, Hinkelbein J, Genzwurker H. Comparison of two different laryngeal mask models for airway management in patients with immobilization of cervical spine.. Anaesthetist 2005 Nov; (Epub ahead of print). Conflict of Interest:None declared |
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Tim M Cook, Consultant Anaesthetist Royal United Hospital, Bath
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Dear Editor I am grateful to Dr Al-Shaikh for his interest in my Editorial. My article was intended to stimulate discussion on this subject and clearly there are arguments on either side of the debate that can be used to support each opposing view. I have expressed one side of the debate in the editorial and it is not necessary to repeat it here. Dr Al-Shaikh’s letter counters some of the illustrative arguments I made. My main contentions however were that 1. the cLMA is proven to be an extremely effective and safe device and 2. the risk of contracting vCJD is many many-fold lower then was projected 8 years ago. As a result the potential benefits of introducing the less well evaluated single use LMAs is far less than was calculated at that time and may well increase risk rather than decrease it. There is little in Dr Al- Shaikh’s letter to counter this view. Nothing in life is risk free and it is unrealistic to try to eliminate risk. While it seems logical that ‘avoidable risks’ should be avoided, it must be recognised that this may introduce new unpredicted risks. This is precisely what happened with single use surgical equipment for tonsillectomies. A balance of risks should be considered and the acceptable risks accepted! Dr Al-Shaikh closes by commenting that he would not like a previously use LMA to be use on him. I would counter that I would not like my airway to be managed with a largely unevaluated device when one of proven safety is available. Finally I do hope Dr Al-Shaikh’s meals are no less appetising as a result of the single-use plastic cutlery which, on the basis of his arguments, I assume he is using for all his meals. Tim Cook Conflict of Interest:I have been paid by Intavent orthofix and the LMA company, who manufacture LMAs, for lecturing. |
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Baha Al-Shaikh, consultant anaesthetist William Harvey Hospital, Andre van Zundert
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Editor, we read with interest the editorial by TM Cook about the
Classic Laryngeal Mask (1). We agree with him that certain standards for
the supraglottic devices should be set before clinical use. We agree that
CE marking doesn't necessarily ensure safe clinical use. We also agree
that C-LMA™ is an extraordinary device in establishing reliable airway in
a variety of clinical situations. However, we would like to raise the
following points:
1. It has been shown that the presence or absence of the epiglottic bars has no effect at all on the clinical performance of the C-LMA™ (2). Unfortunately, currently, the bars are being used as a marketing tool for C-LMA™! 2. Despite being 'cleaned', protein deposits can still be found on virtually all ready for use C-LMA™ (3). Using a brush as recommended by the manufacture can put staff under potential risk of exposure to potentially hazardous material. 3. The use of C-LMA™ requires recording and keeping a data base of uses and sterilizations for each single device to comply with the manufacturer's recommendations. This puts an extra burden on the clinical and administrative staff in the operating theatre and might introduce the risk of using devices beyond the manufacturer’s recommendations. This will be made much worse in UK, as the author correctly states, with the introduction of Super CSSD regarding storage and supply line reliability. 4. Phthalates are compounds used in the manufacturing of plastic devices including single use laryngeal masks and tracheal tubes. The latter have been in routine clinical use for a more than 30 years including paediatric practice. Tracheal tubes tend to be used for much longer durations than LM including paediatric ICM and in much sicker patients. To our knowledge, no reports of adverse effects have been reported due the phthalates in tracheal tubes. 5. It has been shown that incinerating PVC has no or very small effect on the levels of dioxin produced (4, 5). The American Society of Mechanical Engineers found that it was the operating conditions of an incineration plant that was the key factor in determining dioxin production and emissions, rather than the quantity or source of the chlorine entering the incinerator (6). Laryngeal masks made from PVC have different tactile properties during insertion from the silicone rubber ones. We believe that a short learning curve might be needed to get used to them. We achieved ours in less than 25 insertions (7, 8). We support the AAGBI recommendation for the use of disposable laryngeal masks (9). We personally wouldn't like to have a laryngeal mask used on us after being inserted in 39 other people before. References 1. TM Cook. The classic laryngeal mask airway: a tried and tested airway. What now? British Journal of Anaesthesia 2006: 96 (2);149-52. 2. B Al-Shaikh, D Pilcher. Is there a need for the epiglottic bars in the laryngeal mask airway? Canadian Journal of Anesthesia 2003:50; 203-04. 3. G Clery , J Brimacombe, T Stone, C Keller, S Curtis. Routine cleaning and autoclaving does not remove protein deposits from re-usable laryngeal mask devices. Anesth Analg 2003; 97:1189-91 4. Association of Plastics Manufacturers in Europe. Energy Recovery - through co-combustion of mixed plastics waste and municipal solid waste, APME Publication, 1994. 5. BPF Energy Recovery Task Force. Energy Recovery from Plastics Waste British Plastics Federation publication, 1995. 6. HG Rigo. Relationship between chlorine in waste streams and dioxin emissions from combustors of the ASME. ASME 1995. 7. AAJ Van Zundert, Fonck K, B Al-Shaikh, E Mortier A comparison of the LMA-Classic with the new disposable LM-Softseal in spontaneously breathing patients.. Anesthesiology 2003;99:1066-71. 8. AAJ Van Zundert, B Al-Shaikh, J Brimacombe, J Koste, D Koning, E Mortier Comparison of three disposable extraglottic airway devices in spontaneously breathing adults: the LMA-UniqueTM, the Soft SealTM laryngeal mask and the CobraTM perilaryngeal airway. Anesthesiology (in press). 9. AAGBI. Infection control in anaesthesia. London: AAGBI, 2002. Conflict of Interest:None declared |
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Donald M Miller, Anaesthetist Guys and St Thomas Hospital
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I am grateful for the kind things Dr Cook had to say about my response to his editorial and I think we are in agreement about most of the issues with regard to the use of supraglottic airways. For instance, we are both concerned with safety. I entirely agree with his view that supraglottic airways are not intrinsically safe and that safety issues are important. The laryngeal mask is not intrinsically safe and neither is any airway device. The motive for designing the SLIPA™ was precisely to address one of the most important safety issues that is not addressed adequately by the laryngeal mask. That issue is the aspiration risk that is now addressed by the ProSeal LMA™ and SLIPA™ [1,2]. I had no intention of implying that supraglottic airways are intrinsically safe. However, it is because anaesthetists are normally well trained, very skilled in the area of airway management and competent in coping with difficulties, when they arise, that makes the risks in evaluating new devices small. This is the reason that in his reply to my response, Dr Cook refers to the present circumstances as "the currently acceptably safe environment." This needs to be considered when considering what is appropriate regulation. Unlike with drugs, it is not as if we need that kind of backing and surveillance that is outside our every day sphere of influence. That serious things can go wrong with airway management, is a well accepted fact that no anaesthetist should argue with. In reality, the most serious things that have gone wrong, have been with the current devices on the market and in the hands of experienced users. It is an extraordinary observation that the introduction of new devices, that have come and gone, have not been associated with as serious complications. Does that not bear witness to the fact that we, as anaesthetists who investigate new devices, are conservative and well trained and we do not take unreasonable risks? Trying out a new device is undertaken with great care and our ethics committees do carefully examine any new proposal responsibly. I have argued the case very briefly in my first response as to why supraglottic airways do not fall into the same category as drugs and there appears to be no disagreement there. We are also in agreement that regulation needs to be appropriate and the fact that it should not be biased to favour one class of airways. I have already given one example in my reply to Dr Cook’s editorial how proposed regulations using the drug model as an example may achieve the exact opposite to the objectives of improved patient safety. We also both agree that regulation should not thwart future development. Dr Cook makes the excellent point that “Brain's attempts to produce the device that finally became the cLMA began in 1981 and evolved slowly, requiring several materials, more than 200 prototypes and 7000 patient studies before the design was finalized and the product launched in 1988. Since then the cLMA design has remained unaltered.”[4] Some questions that should be asked when introducing new regulations is, would this regulation have thwarted the development of the cLMA? Was there any significant morbidity and how many patients suffered during the developmental phase before its introduction? In what way is the proposed regulation that is to be introduced likely to prevent patient morbidity? Is it necessary? Is current regulation that pertains to manufacturing standards combined with ethics committee approval for clinical evaluations and peer reviewed clinical reports serving the purpose adequately? What evidence is there that it is failing? The issue of managers deciding what laryngeal masks to order (an issue we would all be strongly opposed to) is entirely another issue and should not feature in this argument. When I said market forces, I had no intention of considering managers featuring anywhere in the market place but I meant us anaesthetists as the decision making end users in the market, as opposed to some small select body of researchers deciding what we may or may not use. 1. www.slipa.com 2. Miller DM, Light D. Laboratory and clinical comparisons of the Streamlined Liner of the Pharynx Airway (SLIPA™) with the laryngeal mask airway. Anaesthesia 2003; 58: 136-142. 3. Cook TM. Novel Airway Devices: Spoilt for Choice? Anaesthesia 2003; 58: 107-110. 4. Cook TM. Editorial I: The classic laryngeal mask airway: a tried and tested airway. What now? British Journal of Anaesthesia 2006 96(2):149- 152 Conflict of Interest:I am the inventor of the SLIPA airway and may possibly benefit indirectly from its sale. |
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Tim M Cook, consultant anaesthetist department of anaesthesia, royal united hospital, bath
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Dear Editor I thank Dr Miller for his interest in my editorial. His comments about the difficulties of licensing a new airway device are illuminating. As Dr Miller is the inventor of the SLIPA I assume he has been directly involved in this process and therefore he will have a greater depth of knowledge of this area than I do. In this context his warnings should be listened to, and I agree that we do not wish to replace under legislation with over legislation. However I would like to respond to a couple of his comments. First he suggests that the current process that the United State FDA is going through, of establishing standards for supraglottic airway, is flawed by both influence from commercial interests and by illogical/excluding process. If this is true such commercial interests should be resisted and the processes improved: but poor legislation does not obviate the necessity for the legislation in the first place. I also take issue with Dr Millers implication that supraglottic airways are intrinsically safe and that the ‘safety issue’ is not important. I do not consider this an acceptable stance. I have evaluated almost all of the currently marketed airway devices and have seen airway trauma, airway obstruction and pulmonary aspiration. All these complications are potentially dangerous and it seems wise to exclude from use those devices that increase this risk, so that the currently acceptably safe environment may continue. I finished a previous editorial by stating that my comments were not meant to stifle innovation and the co-operation between innovators and manufacturers were to be encouraged1. This remains my view. The balance is difficult. The current evidence from the UK market is that many decisions about which airway to use for routine airway management are now being made on the basis of cost rather than efficacy or safety and that these decisions may be taken out of the hands of clinicians and given to managers. This is the reality of the free market that Miller advocates and I, in common with many clinicians, have concern over this both for the present and the future of our specialty. Yours sincerely Tim Cook Consultant Anaesthetist Royal United hospital Bath In view of Dr Miller's comments it is perhaps worth stating that while I have been paid by the manufacturers of the laryngeal mask airway for lecturing, the ‘benefit’ has been modest and I have no direct interest or benefit from any airway device of any nature. Conflict of interest I have been paid by the LMA company and Intavent Orthofix, distributors of the classic LMA and other laryngeal mask airways, for lecturing. Reference Cook TM. Novel Airway Devices: Spoilt for Choice? Anaesthesia 2003; 58: 107-110. Conflict of Interest:I have been paid by the LMA company and Intavent Orthofix, distributors of the classic LMA and other laryngeal mask airways, for lecturing. |
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Donald M Miller, Anaesthetist Dept. Anaesthetics, Guys Hospital
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Editor- It is the answer to “What now?” in the title of Dr Cook’s editorial of the February edition of the BJA that needs to be addressed. With over 2500 publications supporting, no one would dispute the first part of the title stating that the classic laryngeal mask airway is a tried and tested airway. The plethora of single use laryngeal mask airways (LMA™) since the patent has expired is a testimony to what an influential development the classic LMA™ (cLMA) is. It is now proposed again by Dr Cook [1,2] that there should be a European/British Supraglottic or Supralaryngeal (SLA) airway standard as is being set up in the USA by the Food and Drug Administration (FDA). I would like to raise a warning about this. It is well known that commercial interests play a part in influencing the control of markets through the FDA. Do we as European anaesthetists not want to retain autonomy from commercial influences if at all possible? Is patient safety really the reason for the regulations that are being proposed? Dr Cook has always been open about declaring benefit from Intavent but that is not the case universally. For example, the session on Supraglottic airways at the recent difficult airways meeting in Lille, at which Dr Cook was one of the speakers on the panel, every speaker extolled at least one of the Intavent products and negative opinions were expressed concerning the most competitive of the competitors to the LMA™. So let us ask the question, what evidence is there that patient morbidity is a problem? Of the new Supraglottic airways that have been introduced and then taken off the market, there is no evidence that suggests that patient morbidity was the reason for their withdrawal. Rather, it was simply the product did not work as well as the LMA, so it was a market forces decision. The standard set by the marvellous cLMA is so high, it means that any new device does not see the light of day for any length of time unless it really has got something worthwhile to offer. As there is no evidence that patient safety in the use of routine airways is a serious risk, the interposition of a special body between manufacturer and specialist anaesthetist, supposedly to “protect patients” who will decide what is safe and not safe, begs the question as to what really is motivating this proposed move? I believe that to allow this to go unchallenged may severely harm development in this field. The current situation in USA will illustrate what I mean. Consider the ASTM draft standard (as yet unpublished). It is currently being drafted in a particular way to exclude certain potential competitors. For example, the first requirement in the supralaryngeal airway (SLA) standard restricts the standard by limiting the sizing criterion to follow the arbitrary sizing of the laryngeal mask and restricting the smallest increment to 0.5. Here is an example of the restrictions of the standard limiting safety by excluding products that have superior characteristics. How you may ask? Well, the laryngeal mask, as a cuff inflating device, is expandable and so can be provided with fewer choice of sizes than an un-cuffed device. By limiting the number of sizes to the minimum that is suitable for a laryngeal mask, the standard indicates indirectly, that only cuffed devices will be acceptable. This in turn may limit the development of certain additional safety features. For example the capability to trap regurgitated liquids within the device is either excluded or severely curtailed from the standard; for cuffs by necessity occupy a volume, a volume that could be used to trap liquids if it were not used for the purpose of producing a cuffed seal. The SLIPA™ airway is the prime example of an uncuffed SLA. As a result it has 15 times the capacity for storing liquids than the cLMA [3] and, therefore, is probably safer from an aspiration point of view. It is excluded from the ASTM draft standard in its current form because it has more sizes to cover the same range of airways, with additional sizes between the sizes of the cuffed laryngeal mask airways. The SLIPA™ sizing method has a more logical basis and relates directly to one anatomical feature of the patient. For example, the size 55 fits a person whose thyroid cartilage width is 55 mm between the left and right cornu (assessed clinically by palpation). A SLIPA™ with the same dimension across the sealing bridge as the palpated width is the correct one to choose. The equivalent laryngeal mask size is between 4.5 and 5.0. This is an example of how a standard can be used to protect an existing market and thwart development in the future. Greater regulation is advantageous if patient safety really is the issue. However, if other factors are driving this regulation, then it may have quite a negative impact upon innovation and development. We would do well to examine this issue a lot more carefully. Dr Cook argued [2] that SLAs should have a similar standard to that of drug evaluation. It is evident from experience with SLAs, that the incidence of serious side effects in routine airway applications is so low as to put these devices in a totally different category from drugs. Despite the endorsement of Cook’s view by Benumof [4], his comments about the introduction of the Glottic aperture seal airway (GO2) confirm the fact that no patient morbidity occurred despite there having been many patients who were subjected to a product that was withdrawn from the market. It being withdrawn voluntarily by the company demonstrates that the circumstances currently in place are working well without the need for additional regulation. Other SLAs (e.g. cuffed oropharyngeal airway {COPA})have come and gone with no recorded lasting serious patient morbidity. Furthermore, it is known that the adverse effects of drugs often do not become apparent until many hours, days, weeks or even years after the original prescription. In contrast, the side effects of SLAs are either immediate (e.g. loss of airway), or occur in the peri-operative period (e.g. sore throat or bruising of the uvula). These side effects will occur whilst the patient remains under the anaesthetists’ care, and a cause-effect relationship is easily established. This fact further decreases the risk of these devices and illustrates why it would be inappropriate to follow regulations similar to that of drugs. If patient safety is not really the issue, and I challenge anyone to show me that it is, then I believe that patients will not benefit from the new proposal. The current circumstance of relative openness to competition is more likely to benefit patients where peer review and market forces decide the future of any new innovation. Restricting these decisions to a small elite group, makes the process more vulnerable to manipulation by commercial interests. References: 1. Cook TM. Editorial I: The classic laryngeal mask airway: a tried and tested airway. What now? British Journal of Anaesthesia 2006 96(2):149-152 2. Cook TM. Novel Airway Devices: Spoilt for Choice? Anaesthesia 2003; 58: 107-110. 3. Miller DM, Light D. Laboratory and clinical comparisons of the Streamlined Liner of the Pharynx Airway (SLIPA) with the laryngeal mask airway. Anaesthesia 2003; 58: 136–42. 4. Benumof JL. New Airway Devices. Anaesthesia 2003; 58: 804. Conflict of Interest:Miller is the inventor of the SLIPA airway device and may indirectly benefit from its sale. |
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