A proposal for updating the classification of SADs and a new scoring system

The scoring and classification of supraglottic airways (SADs) is an interesting topic and currently the subject of much debate.

In 2011, a paper by Cook and Howes entitled, Recent developments in efficacy and safety of supraglottic airway devices, published in Continuing Education in Anaesthesia, Critical Care and Pain, described a classification of SADs into 1st and 2nd generation devices. The simplicity of this classification had immediate appeal and it quickly became established as the most widely used method for classifying SADs.

In A critique of elective pediatric supraglottic airway devices by White, Cook and Stoddart, a 1st generation device was described as asimple airway tube’ and 2nd generation as a device that ‘incorporates specific design features to improve safety by protecting against regurgitation and aspiration’.

Numerous publications, presentations and reviews subsequently utilised this classification, including the seminal  NAP4 report, the 4th National Audit Project of the Royal College of Anaesthetists (RCoA) and the Difficult Airway Society (DAS) on ‘Major Complications of Airway Management in the United Kingdom’, which made a number of recommendations regarding the use of SADs, and in particular the use of 2nd generation devices.

Its use has not been confined to the UK. The term is widely understood, accepted and used internationally. However, the classification of SADs as either 1st or 2nd generation was not the first classification.

In 2004, A Proposed Classification and Scoring System for Supraglottic Sealing Airways: A Brief Review by Miller was published in Anesthesia & Analgesia. This categorised SADs by the sealing mechanism. Three primary groups were identified:

  • Cuffed perilaryngeal sealers – such as the laryngeal mask airway
  • Cuffed pharyngeal sealers – such as the Cuffed Oropharyngeal Airway (COPA™)
  • Uncuffed anatomically preshaped sealers – such as i-gel®

This classification was further subdivided, so cuffless perilaryngeal sealers could be either ‘directional’ or ‘non-directional’, and cuffed pharyngeal sealers could be designated as ‘with’ or ‘without’ oesophageal sealing. The sealing mechanisms were described in detail, in conjunction with force vectors, frictional force and whether a device was reusable or single-use; or incorporated a mechanism to provide additional protection against aspiration.

In 2009, five years after Miller’s paper, the International standard, ISO 11712:2009(E) Anaesthetic and respiratory equipment – Supralaryngeal airways and connectors was published. This standard included five classifications of supralaryngeal designs. Further details can be obtained from my 2012 blog post on the classification of SADs.

Whatever their merits or limitations, neither the classification in the international standard or Miller’s classification from 2004 ever enjoyed the same measure of popularity or widespread use currently evident for the categorisation in to 1st and 2nd generation. It is therefore particularly interesting to note a proposal by the originator of the 1st/2nd generation classification, Professor Cook, for an update in correspondence to the editor of the British Journal of Anaesthesia (BJA).

The proposal is to add the suffix ‘i’ to 1st or 2nd generation to indicate those devices which enable intubation (eg with success >50%) and then include ‘d’ for direct intubation and ‘g’ for guided intubation. The correspondence provides three examples of SADs classified in this manner, as follows:

  • cLMA – 1st generation ‘ig’
  • Intubating LMA – 1st generation ‘id, ig’
  • i-gel® – 2nd generation ‘ig’

Further discussion regarding an updated classification can be seen on the BJA Out of the blue E-letters archive. Alternative classifications have been proposed, including one by Michalek and Miller in, ‘Airway Management Evolution – In a search for an ideal extraglottic airway device.

The scoring, as opposed to the classification of SADs, also has an interesting history. Miller proposed a ‘provisional scoring of airways’ in his 2003 paper already discussed above. This identified desirable features of airways for routine use and then for each variable (easy insertion, seal for IPPV etc) assigned a score to each device. An updated version, also by Miller, along similar lines, appeared in the second chapter of the book, The i-gel supraglottic airway, edited by Michalek and Donaldson.

The most recent scoring of SADs appeared in a particularly interesting editorial entitled, ‘Time to abandon the ‘vintage’ laryngeal mask airway and adopt second-generation supraglottic devices as first choice’ by Cook and Kelly.

This editorial notes that SADs now have important roles beyond airway maintenance during routine low-risk surgery, including airway maintenance in obese and higher risk patients and airway management outside the operating theatre by experts and novices, most especially during cardiac arrest. Other examples are also provided.

As a result, the authors state it is worth considering ‘whether one device can be the best device for all such functions and perhaps considering whether some devices might no longer be needed. This discussion raises the question as to whether the cLMA (and equivalent SADs) have any role in modern airway practice or whether it is time to move on.’

The editorial discusses a number of interesting and important issues related to the use of SADs, including the question of safety and efficacy, what sort of evidence should be sought when deciding which SAD to select – particularly if safety is the major concern – and the value and limitations of randomised controlled trials in answering safety related questions. Other issues of importance are also discussed, so it is critical the editorial is read in its entirety to fully appreciate the context in which the scoring system included in the paper is provided.

The scoring system itself lists the desirable features of a SAD (airway seal, overall insertion success, aspiration protection, avoiding sore throat etc) for a specific application (routine use during elective anaesthesia, use by a novice at a cardiac arrest etc), provides a maximal score for each parameter according to its importance and then allocates a score for each parameter for each device.

The authors confirm the ranking and allocated scores are based on their judgement, clinical experience and knowledge of the literature and also acknowledge that others may allocate maximal and relative scores differently.

I will not spoil your enjoyment of this editorial by revealing the results here, except to say the authors comment that, in the tables provided, it is notable that different circumstances lead to different SADs ranking highest and that ‘the cLMA rarely ranks highly in such analyses.’

The four scoring tables provided are as follows:

  • Table One: Choice of airway for routine use during elective anaesthesia
  • Table Two: Choice of airway for use by a novice at a cardiac arrest
  • Table Three: Choice of airway for expert rescue after failed intubation during rapid sequence induction
  • Table Four: Choice of airway for rescue after failed intubation followed by intubation through the SAD

In summary, a number of methods for classifying and scoring SADs have been proposed over the years. The most popular and widely used classification remains the categorisation of SADs as either 1st or 2nd generation. An update to this classification has been proposed to indicate those devices which enable intubation and a new scoring system has been published as part of an editorial in the BJA.

i-gel is a registered trademark of Intersurgical Ltd. cLMA is an abbreviation for the LMA Classic. LMA and LMA Classic are registered trademarks of Teleflex Incorporated or its affiliates. COPA is a trademark of Mallinckrodt Medical, Inc.

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Pre-hospital airway management – the debate continues

 In a recent editorial published in Resuscitation, entitled ‘Pre-hospital airway management: The data grows rapidly but controversy remains’, David Lockey and Hans Morten Lossius discuss the results from three studies published in the same issue:

1. An update of out of hospital airway management practices in the United States.

2. Higher insertion success with the i-gel supraglottic airway in out-of-hospital cardiac arrest: A randomised controlled trial.

3. The impact of airway management on quality of cardiopulmonary resuscitation: an observational study in patients during cardiac arrest.

An update of out of hospital airway management practices in the United States

Digges et al utilised the 2012 National Emergency Medical Services Information System (NEMSIS) Public-Release Research Data Set to examine over 19 million EMS activations. This included 74,993 intubations, 21,990 alternate airway patient care events (confirmed as either a Combitube®, Esophageal Obturator, Laryngeal Mask Airway or King LT®) and 1,332 Cricothyroidotomys. BVM ventilation was undertaken on 56,025 occassions and there were 54,241 oropharyngeal airway (OPA) and 404,828 nasopharyngeal airway (NPA) interventions.

Overall intubation success was 85.3%. Alternate airway success rates were 79.6% overall. The most successful of these was was the King LT® (89.7%) and the least successful the Esophageal Obturator (38.0%).

It is interesting to make some comparison of these results to an earlier examination of the same database for EMS activations four years earlier in 2008. The earlier study included fewer states, so any comparison must be undertaken with caution, but the alternate airway devices recorded as having been used were the same in both reports.

This is worth noting, as the alternate airway devices used are quite different from those used in some other markets such as the UK. As reported in a previous blog post, in the Adult ALS chapter of the Resuscitation Council (UK) 2010 Resuscitation Guidelines, it is confirmed that ‘The Combitube® is rarely, if ever, used in the UK and is no longer included in these guidelines’, and in addition that the Laryngeal Tube (LT) ‘is not in common use in the UK’. What about the rest of Europe? In the 2010 European Resuscitation Council (ERC) Guidelines for Resuscitation, it is stated that ‘Use of the Combitube® is waning and in many parts of the world is being replaced by other devices such as the LT’. In the two papers utilising the NEMSIS data discussed in this blog post, there is no mention of the newer 2nd generation SADs such as the i-gel® and LMA Supreme® which are in regular use in many countries.

In an editorial published in 2009 in Resuscitation, the official journal of the European Resuscitation Council, entitled, ‘Airway management for out-of-hospital cardiac arrest – More data required’, Nolan and Lockey concluded that ‘New airway devices appear frequently but, in our opinion, the three currently available disposable SADs that need to be studied for use during CPR are the i-gel®, the LMA Supreme® and the disposable LT’. Only one of these devices, the LT, was used in the Diggs update of out-of-hospital airway management practices in the United States.

This is significant, as the authors of the update of out of hospital airway management practices in the U.S. state that, ‘This study and many others show that there are problems with out-of-hospital ETI. The results of this study show that alternate airways are not the answer’. As Lockey and Lossius comment, the latter point is a ‘strong and controversial statement’. The latter also make a number of additional important points, including confirmation that ‘although supraglottic devices are clearly not all equal, the highest performing devices have similar success to intubation without the high training burden and risks of oesophageal intubation’.

This leads in nicely to the second study discussed in their editorial:

Higher insertion success with the i-gel® supraglottic airway in out-of-hospital cardiac arrest: A randomised controlled trial.

 Lockey and Lossius introduce the study as follows:

‘Confirming the major difference between the performance of different supraglottic devices, and also published in this issue, is a pre-hospital randomised trial of the second generation i-gel™ device vs an LMA™. Significantly different success rates were demonstrated and the second generation device clearly outperformed the LMA™.’ The laryngeal mask compared to i-gel® in this study was the Portex® Soft Seal® device.

A first generation SAD has been described as a ‘simple airway tube’ and a second generation SAD as ‘incorporating specific design features to improve safety by protecting against regurgitation and aspiration’ (White, Cook and Stoddart)

The paper Lockey and Lossius refer to is a single centre, prospective parallel-group ‘open label’ randomised controlled trial (RCT) in which patients in cardiac arrest were allocated to either the Intersurgical i-gel® supraglottic airway or the Portex® Soft Seal® Laryngeal Mask. The primary outcome was successful insertion as determined by the paramedic who inserted the device.

Fifty-one patients were randomised. Three were not in cardiac arrest, so the final analysis reports on data from forty-eight patients. The Intersurgical i-gel® had an insertion success rate of 90% (18/20) compared to 57% (16/28) with the Portex® Soft Seal® (p=0.023). The authors concluded that:

‘The i-gel® supraglottic airway was associated with higher successful insertion rates in subjects with out-of-hospital cardiac arrest. The i-gel® supraglottic appears easier for paramedics to use and appears a suitable first line supraglottic airway for out-of-hospital cardiac arrest’.

As confirmed earlier, there was no data for i-gel® or a number of the other newer 2nd generation supraglotic airways in ‘An update of out of hospital airway management practices in the United States’ by Diggs et al. Evidence for one supraglottic airway should not be extrapolated to another device with different design characteristics, so their data is only relevant to those devices included.

The impact of airway management on quality of cardiopulmonary resuscitation: an observational study in patients during cardiac arrest

The third paper discussed by Lockey and Lossius is, ‘ The impact of airway management on quality of cardiopulmonary resuscitation: an observational study in patients during cardiac arrest’. This prospective observational study by Yeung et al enrolled 100 consecutive patients between 2008 and 2011 with the aim of determining the effect of advanced airway use, either an endotracheal tube (ET) or laryngeal mask airway (LMA) on the no flow ratio (NFR) and other measures of CPR quality. The control cohort was patients receiving only bag-mask ventilation. The results showed use of an advanced airway during in-hospital cardiac arrest was associated with improved no flow ratios. The primary reason for the improvement appears to be switching from a compression to ventilation ratio of 30:2 to continuous chest compressions and asynchronous ventilation. Further details can be accessed with the earlier link.

A particularly interesting aspect of this paper is the discussion section, where the uncertainties about the role of advanced airways in cardiac arrest are examined. Firstly there is uncertainty about whether ventilation is required at all in the early stages of cardiac arrest (the Yeung et al paper examined patients in the later stage of out-of-hospital or in-hospital cardiac arrest where some form of ventilation is required). They mention the studies from Arizona prioritising Cardio-Cerebral Resuscitation (CCR) over ventilation in the early stages of cardiac arrest.

The timing of airway intervention and any impact on interruptions in chest compressions are also likely to be important. There is discussion regarding interruptions in CPR and the link to reductions in coronary perfusion pressure and development of ventricular fibrillation (VF). The potential impact of supraglottic airways on carotid blood flow, dislodgement of LMAs and aspiration risk are also discussed. All important subjects.

In their editorial, Lockey and Lossius comment that, ‘This study is one of several that demonstrate potential improvements in quality indicators in resuscitation which may be in conflict with large studies with undifferentiated casemix and resuscitation techniques which generally question the value of advanced life support techniques in cardiac arrest or trauma patients.’

Conclusion

So where does all this new data leave us? Lockey and Lossius conclude that ‘Our interpretation of the currently available data on pre-hospital advanced airway management is that the risks and benefits need to be considered for every patient on scene with airway compromise. The management that results from this analysis will depend on the indications and condition of the patient as well as the skills and available interventions on scene.’ This is not entirely dissimilar to the statement in the European Resuscitation Council (ERC) guidelines for resuscitation 2010 in relation to airway management during cardiac arrest, which state that ‘There are no data supporting the routine use of any specific approach to airway management during cardiac arrest. The best technique is dependent on the precise circumstances of the cardiac arrest and the competence of the rescuer.’

With regard to SADs, Lockey and Lossius conclude:

‘The constant evolution of existing supraglottic airways and the introduction of new devices makes generalisation and performance assessment of these devices difficult, but the expanding dataset will hopefully ensure that only the highly performing devices will be used in future studies, thus making interpretation more straightforward’.

No doubt REVIVE#2 will provide some useful additional data in this regard and it is to be hoped that additional randomised controlled trials, similar to the study published by Middleton et al discussed here, will be conducted so the dataset continues to expand.

Arthur Guedel and the oropharyngeal airway

One-piece Guedel

Any definitive history of the development of the oropharyngeal airway (OPA) is likely to include reference to Arthur Guedel and the OPA he described in a short article entitled, ‘A nontraumatic pharyngeal airway’ published in the Journal of the American Medical Association (JAMA) in 1933. In little more than a dozen lines he described a device which today is almost synonymous with the term oropharyngeal airway.

Although Joseph Thomas Clover (1825-1882) is credited with first use of an artificial airway, as this was a nasopharnygeal device, it is Sir Frederic William Hewitt (1857-1916) who is usually acknowledged as being first to describe the use of an oropharyngeal airway, in an article entitled ‘An artificial air-way for use during anaesthetisation’, published in The Lancet in 1908.

Hewitt was appointed as anaesthetist to King Edward VII in 1901. He was also a founding member of the Society of Anaesthetists in London and was made a member of the Royal Victorian Order (4th class) in 1902 for personal service to the King. The Frederick Hewitt Lecture was inaugurated by the Royal College of Surgeons (now the Royal College of Anaesthetists), in 1950. Fittingly, the lecture is now given biennially with the Joseph Clover Lecture – two pioneers of airway management appropriately acknowledged for their contribution to anaesthesia and airway management. The names of those anaesthetists who have delivered a Hewitt or Clover lecture reads like a roll call of anaesthetic icons, and includes Sir Ivan Magill, Sir Robert Macintosh, Gordon Jackson Rees and Brian Sellick.

Hewitt and the airway he designed are discussed in a historical note published in Anaesthesia by RP Haridas entitled, ‘The Hewitt airway – the first known artificial oral ‘air-way’ 101 years since its description’. The original airway incorporated a straight rubber tube, but a curved version was later developed. Brimacombe described the Hewitt airway as the forerunner to many modern oropharyngeal airways (Laryngeal Mask Anesthesia. Principles & Practice. Elsevier Ltd. 2nd edition. 2005).

Hewitt was undoubtedly an anaesthetic giant of the late nineteenth and early twentieth century, yet his contribution to anaesthesia and airway management may be less immediately well known than that of Arthur Guedel.

Maltby confirms in ‘Notable Names in Anaesthesia’ that Arthur Guedel was born in Cambridge City, Indiana in 1883. Despite losing three fingers when he was a teenager, Guedel still managed to become an accomplished pianist and composer! His medical career started at the Medical College of Indiana in 1903. After graduating in 1908, he was interned at the City Hospital in Indianapolis where he was required to administer ether and chloroform. He eventually served as an anaesthetist in the American Expeditionary Forces in France in World War One, where the challenges faced by inexperienced personnel from the army medical corps provided the impetus to develop a classification of the stages of anaesthesia.

Guedel also created the first inflatable cuffs for ET tubes, experimenting with location, above, below or at the vocal cords, cuff pressures and possible inflation techniques. Around this time, Guedel would often use his own pet dog, appropriately named ‘Airway’, as part of his lecture demonstrations. Maltby confirms that Airway survived to enjoy ‘an honourable retirement with the Waters family in Madison, Wisconsin.’ A glance at the content of Guedel’s lecture demonstrations from the 1920s suggests that Airway’s survival to retirement was by no means a foregone conclusion and can itself be considered an achievement.

The recipient of the dog, Ralph Waters, wrote a personal tribute to his friend Arthur Guedel in the BJA in 1953 as part of the ‘Eminent Anaesthetists’ series. He confirmed that the saying, ‘If a man loves dogs he will love mankind’ was true of Guedel. He discusses their correspondence, at its most prolific between 1925 to 1945, his athleticism, and his motto for many years, ‘Maintain Flying Speed’, taken from the pilot of the time whose altitude began to fail as his forward progress diminished. Interestingly, he makes no mention of the oropharyngeal airway for which Guedel is perhaps most often remembered today.

Guedel originally described his oropharyngeal airway in JAMA as follows: ‘The airway herewith depicted is made of rubber and is sufficiently soft and flexible not to traumatize yet amply rigid to maintain an open oropharyngeal air passage under all conditions.’ He also confirmed that ‘the metal insert extends into the airway for about 2cm from the oral opening and prevents collapse of the rubber between the teeth’.

Thomas Baskett, in his 2004 article on Guedel published in Resuscitation, quoted Guedel’s own 1937 publication, ‘Inhalational Anesthesia: A Fundamental Guide’, describing use of the oropharyngeal airway during anaesthesia when ‘there is sufficient muscular relaxation to permit the lower jaw to fall backward allowing the base of the tongue to lie against the posterior wall of the pharynx. Depending upon the anatomical structure of the pharynx, this may partially or completely obstruct inspiration. It is usually remedied at once by the insertion of a pharyngeal airway which will hold the tongue forward from the pharyngeal wall.’

Dorsch and Dorsch in ‘Understanding Anesthesia Equipment (5th edition)’, describe an oropharyngeal airway as follows ‘…..may be made of elastomeric material or plastic. It has a flange at the buccal end to prevent it from moving deeper into the mouth. The flange may also serve as a means to fix the airway in place. The bite portion is straight and fits between the teeth or gums. It must be firm enough that the patient cannot close the lumen by biting. The curved portion extends backward to correspond to the shape of the tongue and palate.’

The International Standard ISO 5364: 2008 ‘Anaesthetic and respiratory equipment – oropharyngeal airways’ describes an oropharyngeal airway as a ‘device intended to maintain a gas pathway through the oral cavity and pharynx’. It confirms the size should be designated by the nominal length expressed in centimetres and provides a table to show how the length should be calculated. A table is provided confirming designated size (nominal length) , as well as tolerances and minimum inside dimensions. The latter is relevant to the ability to pass other devices, such as a suction catheter, through the airway.

The European Resuscitation Council (ERC) Guidelines for Resuscitation 2010 confirm that ‘An estimate of the size required is obtained by selecting an airway with a length corresponding to the vertical distance between the patient’s incisors and the angle of the jaw.’

The original Guedel airway was made of rubber with a metal insert. Most modern Guedel airways are made of plastic. Dorsch and Dorsch confirm that modifications to aid flexible fibreoptic intubation have been described and Guedel airways with the bite block incorporated into one moulding, thereby eliminating the danger of loose or detached bite blocks, are also available.

The Guedel airway has endured the test of time and remains one of most widely known and used airway adjuncts eighty years after it was first described. It is of simple design, but many of the best inventions often are.

 

Paediatric Intersurgical i-gel® – is it an advance over other SADs?

8201_i-gel_1_side_on_white
In 2009, Pediatric Anesthesia published a paper by White, Cook and Stoddart, entitled, ‘A critique of elective pediatric supraglottic airway devices’, which aimed to present the evidence surrounding the use of currently available supraglottic airways (SADs) in routine anaesthetic practice. It was one of the first papers to divide SADs in to first and second generation devices. First generation devices were described as simple airway tubes, and second generation devices, such as i-gel®, as incorporating ‘specific design features to improve safety by protecting against regurgitation and aspiration’.

The review highlighted that, apart from the LMA Classic® (cLMA) and LMA Proseal® (pLMA), there was a lack of high quality data of efficacy for SADs, stating that, ‘The best evidence requires a randomized controlled trial comparing a new device against an established alternative, properly powered to detect clinically relevant differences in clinically important outcomes. Such studies in children are rare. Safety data is even harder to establish, particularly for rare events such as aspiration’.

Whilst the authors did comment on the i-gel, at the time of their review paediatric sizes of the device were not available. However, they did note the i-gel offers, ‘the possibility of a genuine improvement on the pLMA’, based on the stability provided in adult sizes by the elliptoid shape of the device, but that it remained to be seen whether this stability would be retained in the paediatric sizes. The review concluded that ‘The pLMA has yet to be outperformed by any other SAD, making it the premier SAD in children and the benchmark by which newer second generation devices should now be compared’.

(fig 1)

(fig 1)

Paediatric sizes of i-gel (fig 1) became available in the latter half of 2009, extending the lower weight range from 30kg to 2kg. As with the adult sizes, the paediatric sizes have a non-inflatable cuff, a gastric channel (except size 1), an integral bite block and a buccal cavity stabiliser. Details of the applicable weight range for each size are shown below (fig 2).

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(fig 2)

The first independent data on the use of the new paediatric sizes came from the Hautepierre University Hospital of Strasbourg, who presented an abstract on the device at the SFAR Congress in Paris in September 2009 and at the Amercian Society of Anesthesiologists (ASA) Annual Meeting in October 2009, entitled, ‘The i-gel in paediatric surgery: Initial series’. This abstract reported on 50 insertions of the device in patients between 6 months and 14 years. Stability of the device and avoidance of intubation were seen as advantages. An interview with Professor Pierre Diemunsch, Consultant at the Hautepierre University Hospital, discussing their findings is available on YouTube.

A number of observational/cohort studies followed. Beringer et al studied the i-gel in 120 anaesthetised patients to assess efficacy and usability. First time insertion success was 92%, overall insertion success was 99% and the median leak (seal) pressure was 20cm H2O. One child regurgitated without aspirating. 16 manipulations were required in 11 children to improve the airway. The authors concluded that, ‘other complications and side effects were infrequent. The i-gel was inserted without complications, establishing a clear airway and enabling spontaneous and controlled ventilation in 113 (94%) children.’

Hughes et al studied the device in 154 children. First time insertion success was 93.5%, overall insertion success was 99.3%. The median leak (seal) pressure was 20cm H2O. The authors concluded that i-gel provided a satisfactory airway during anesthesia for spontaneously breathing infants and children, but felt that to ensure a clear airway, considerable vigilance is required when fixing the device in the mouth.

Fixation is important. The instructions for use for the paediatric i-gel make it clear that as soon as insertion has been successfully completed, the i-gel should be held in place until and whilst the device is secured in place with tape maxilla to maxilla.

Randomised comparative studies followed. The first by Theiler et al, compared i-gel to the Ambu® AuraOnce. This was followed by comparisons to the cLMA . Lee et al found a similar leak pressure between i-gel and the cLMA, but a shorter insertion time for i-gel – 17 secs median (IQR 13.8 – 20.0) v 21.0 secs median (IQR 17.5 – 25.0) and an improved glottic view.

A summary of seal pressures from published clinical studies for the paediatric sizes of i-gel is shown below (fig 3)

Paediatric i-gel seal pressures

(fig 3 ) Paediatric i-gel seal pressures

Considering the conclusion made by White, Cook and Stoddart, perhaps the most interesting comparisons are those to the pLMA.

Two such comparative studies have so far been published. The first was a randomised prospective study entitled, ‘Comparison of size 2 i-gel supraglottic airway with LMA-ProSeal and LMA-Classic in spontaneously breathing children undergoing elective surgery’, which compared the devices in 120 children aged 2-5 years scheduled for surgery of <1 hour duration. The oropharyngeal seal pressure for i-gel was higher than both the cLMA and the pLMA: 26, 22 and 23 cmH20 respectively. First time insertion success was also higher for the i-gel than both the cLMA and the pLMA, 95%, 90% and 90% respectively. The authors concluded that ‘Pediatric size 2 i-gel is easy to insert and provides higher OSP compared with the same size pLMA and cLMA in spontaneously breathing children undergoing elective surgery. It may be a safe alternative to LMA in day care surgeries.

In November 2012, Acta Anaesthesiologica Scandinavica, published a crossover design study by Gasteiger, Brimacombe, Oswald, Perkhofer, Tonin, Keller and Tiefenthaler, entitled ‘LMA ProSeal® vs i-gel in ventilated children: a randomised, crossover study using the size 2 mask‘. The paper studied fifty one children aged 1.5 – 6 years. Leak pressure for both devices was similar, as was fibreoptic position, with the vocal cords visible from the distal airway tube in 94% and 96% respectively. The authors concluded that ‘oropharyngeal leak pressure and fibreoptic position of the airway tube are similar for the size 2 LMA ProSeal® and i-gel in non-paralysed ventilated children’

Clinical evidence takes time to build, and some of the studies looked at one size only and all studies have limitations. However, the above evidence suggests i-gel may yet prove to be ‘a genuine improvement on the pLMA‘, as thought possible by White, Cook and Stoddart back in 2009.

Interestingly, a number of other studies on paediatric i-gel have recently been published, including, ‘A randomised equivalence trial comparing the i-gel and the laryngeal mask airway Supreme in children‘, in which i-gel had a higher seal pressure than the sLMA, 20 (IQR 18-25) v 17 (14-22) cm H20 respectively.

A comparison of three supraglottic airway devices used by healthcare professionals during paediatric resuscitation simulation‘ compared the i-gel to the Laryngeal Tube (LTS) and the LMA Unique® (uLMA) in manikins. A total of 66 healthcare providers, 22 paramedics, 22 nurse anaesthetists and 22 anaesthesia residents participated in the study. The authors concluded that ‘In terms of both the time required for successful placement and the rate of successful placement, the i-gel is superior to the laryngeal mask and tube in paediatric resuscitation simulations by healthcare workers with different levels of experience with paediatric airway management‘.

More data is awaited.

Note:
i-gel is a registered trademark of Intersurgical Ltd. Continue reading

REVIVE airway study

The European Resuscitation Council (ERC) guidelines state that ‘There are no data supporting the routine use of any specific approach to airway management during cardiac arrest. The best technique is dependent on the precise circumstances of the cardiac arrest and the competence of the rescuer.’

In an editorial published in Resuscitation in 2009, entitled, ‘Airway Management for out-of-hospital cardiac arrest – more data required’, Nolan and Lockey confirmed that whilst tracheal intubation has been considered the gold standard for airway management during cardiac arrest, there is no high level evidence proving that tracheal intubation improves outcome. They also highlighted that virtually all data relating to the use of supraglottic airway devices (SADs) in cardiac arrest derive from low level studies, and concluded there is an urgent need for high-quality randomised controlled trials of the use of SADs for cardiopulmonary resuscitation (CPR).

The Airway Management Feasibility Study (REVIVE – Airways) is an attempt to start the process of providing just such evidence, by conducting a randomised comparison of the ventilation success of two 2nd generation supraglottic airways, i-gel® and the LMA Supreme®, in the initial airway management of out-of-hospital cardiac arrest (OHCA) compared to current practice, which is expected to be tracheal intubation. Clinical research in OHCA can be particularly difficult and is often an ethical challenge. Randomisation is not straightforward, so this study is of a cluster randomised design, whereby the randomisation is of the paramedic (as opposed to the patient) to one of the SADs or to ‘current practice’. This is a feasibility study, so the focus is on assessing how easy it is to recruit paramedics, and whether the study design will allow effective comparison of each of the three study arms. Secondary objectives include survival to hospital discharge. If the study does produce useful data, it is hoped this will lead to a national trial.

At the recent International Conference on Emergency Medicine (ICEM) in Dublin, the REVIVE Airway Working Group presented a poster confirming successful recruitment of 184 paramedics employed by Great Western Ambulance Service (GWAS) to the study. This exceeded their target of 150 – a recruitment of 35% of those eligible. The study is expected to end in February 2013. If the methodology proves successful, perhaps there is a chance we might see published data from a national study by 2016. That may seem a long time away, but it should be worth the wait.