Airways-2

CPR2As we wait for the new 2015 guidelines for resuscitation later this year, the protocol for a major study which should be completed in time for inclusion in the evidence review for the 2020 guidelines is now available on-line.

‘Project portfolio HTA 12/167/102, Cluster randomised trial of the clinical and cost effectiveness of the i-gel supraglottic airway device versus tracheal intubation in the initial airway management of out of hospital cardiac arrest (Airways-2)’

Just over a year ago I uploaded a blog post entitled, REVIVE airway study – clinical outcomes and future plans. As well as reviewing REVIVE 1, the article discussed the future plans for REVIVE 2, now called AIRWAYS-2. Publication is expected in 2019, which if realised, will allow the study to be considered as part of the 2020 ILCOR Scientific Evidence Evaluation and Review System (SEERS) process.

Why is this trial important? Well, AIRWAYS-2 is an attempt to provide the type of high quality evidence called for back in 2009 by Nolan and Lockey in an editorial entitled, ‘Airway management for OHCA – more data required’. In this editorial, the authors commented that, ‘Virtually all the existing data relating to the use of SADs in cardiac arrest are derived from low-level studies. There is an urgent need for high-quality randomised controlled trials of the use of SADs for CPR.’ However, such studies are not easy to perform in the pre-hospital setting.

The AIRWAYS-2 trial summary confirms that:

 ‘There is real uncertainty amongst paramedics and experts in the field about the best method to ensure a clear airway during the early stages of OHCA. We therefore propose to undertake a large research study to determine whether intubation or the best available SAD (called the i‐gel) gives the best chance of recovery following OHCA.’

Paramedics from the following four English NHS ambulance services will participate:

  • South Western Ambulance Service NHS Foundation Trust (SWAST)
  • East of England Ambulance Service NHS Trust
  • East Midlands Ambulance Service NHS Trust
  • Yorkshire Ambulance Service NHS Trust

 As randomisation by patient is impractical in the pre-hospital emergency setting, randomisation will be by paramedic. The trial population will include adults who have suffered an OHCA that is not due to trauma. Patient exclusion criteria includes an estimated weight <50kg and a mouth opening of <2cm.

The trial intervention control group is the current standard care pathway: Tracheal intubation. The Intervention group (i-gel) is referred to as follows:

 ‘Because of its speed and ease of insertion, and the fact that it does not require a cuff to be inflated, the i‐gel has emerged as the preferred SAD for use during OHCA in Europe.’

 The aim and objectives of the study are confirmed as follows:

 Aim:

  • To determine whether the i‐gel, a second‐generation SAD, is superior to tracheal intubation in non-traumatic OHCA in adults, in terms of both clinical and cost effectiveness.

 Objectives:

  1. To estimate the difference in the primary outcome of modified Rankin Scale (mRS) at hospital discharge between groups of patients managed by paramedics randomised to use either the i‐gel or intubation as their initial airway management strategy following OHCA.
  2. To estimate differences in secondary outcome measures relating to airway management, hospital stay and recovery at 3 and 6 months (see section 4.6.2) between groups of patients managed by paramedics randomised to use either the i‐gel or intubation.
  3. To estimate the comparative cost effectiveness of the i‐gel and intubation, including estimating major in hospital resources and subsequent costs (length of stay, days of intensive and high dependency care, etc.) in each group.

The secondary outcomes include initial ventilation success, regurgitation/aspiration, the sequence of airway ventilations delivered and return of spontaneous circulation (ROSC). Additional secondary outcomes will be recorded for patients who survive to hospital and to hospital discharge, including for the latter, Modified Rankin scale and quality of life at 3 and 6 months following OHCA.

It is stated that a 2% improvement in the proportion of patients achieving a good clinical outcome would be clinically significant. This study will also include an economic evaluation. It is estmated that 1,300 paramedics will participate and the cost will be over £2 million.

An Airways-2 web-site is now up and running, and includes an overview of the trial, details regarding the study team and an FAQ page.

Four years may seem a long time to wait and there is always the risk that by the time the results are ready to be published, the landscape of airway management during cardiac arrest has changed. However, it would be difficult to factor out such a risk, and AIRWAYS-2 can be seen as a significant attempt to provide the high level data regarding management of the airway during the initial stages of cardiac arrest we all want to see.

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ILCOR, 2015 and the countdown to new guidelines

8704-000_i-gel_resus_mainAs 2014 draws to a close, it seems a good opportunity to look forward to 2015 and consider what the new year may bring. It does look set to be an interesting year. The inaugural European Games will be held in Baku in June, the 7th Rugby World Cup will take place in England in September and Resuscitation 2015 – The Guidelines Congress, will be held in Prague in October!

Sport can be unpredictable, but the winners of the 2015 Rugby World Cup will almost certainly come from one of just five or six nations. I doubt the new 2015 ERC Resuscitation guidelines will provide us with too many surprises either, and neither should they. The ILCOR Scientific Evidence Evaluation and Review System (SEERS) and Consensus on Resuscitation Science and Treatment Recommendations (CoSTR), from which new guidelines are eventually developed, is a process that should ensure the right questions are asked, the relevant evidence is gathered and reviewed and a consensus on the science is obtained before any treatment recommendations are made. New guidelines then follow.

The ILCOR web-site provides the opportunity to review the current status of the PICO questions. In the Advanced Life Support (ALS) section, two questions in particular caught my attention:

Advanced airway placement (ETT v SGA)

Among adults who are in cardiac arrest in any setting  (P), does tracheal tube insertion as first advanced airway  (I), compared with insertion of a supraglottic airway as first advanced airway  (C), change ROSC, CPR parameters, development of aspiration pneumonia, Survival with Favourable neurological/functional outcome at discharge, 30 days, 60 days, 180 days AND/OR 1 year, Survival only at discharge, 30 days, 60 days, 180 days AND/OR 1 year (O)?

Airway placement (Basic vs Advanced)

Among adults who are in cardiac arrest in any setting (P), does insertion of an advanced airway (ETT or supraglottic airway) (I), compared with basic airway (bag mask +/- oropharyngeal airway) (C), change Survival with Favourable neurological/functional outcome at discharge, 30 days, 60 days, 180 days AND/OR 1 year, Survival only at discharge, 30 days, 60 days, 180 days AND/OR 1 year, ROSC, CPR parameters, development of aspiration pneumonia (O)?

Both of the above subjects have been discussed in previous blog posts. The subject of ETT v SGA was covered in a post from October 2012 entitled, ‘Supraglottic airways versus tracheal intubation for OHCA’ and the latter in a post from February 2013 entitled, ‘Pre-hospital airway management for patients with OHCA’.

Since these blog posts were written, additional evidence has been published and it will be interesting to see what conclusions there are from the SEERS/CoSTR process.

In the Basic Life Support (BLS) section, one question stood out as of particular interest:

 Passive ventilation techniques

Among adults and children who are in cardiac arrest in any setting (P), does addition of any passive ventilation technique (eg positioning the body, opening the airway, passive oxygen administration) to chest compression-only CPR (I), compared with just chest compression-only CPR (C), change Survival with Favourable neurological/functional outcome at discharge, 30 days, 60 days, 180 days AND/OR 1 year, Survival only at discharge, 30 days, 60 days, 180 days AND/OR 1 year, ROSC, bystander initiated CPR, oxygenation (O)?

The subject of passive oxygenation has been covered in two blog posts on this site. The first, published in April 2012, asked the question, ‘Should we be passive about oxygenation?’ and the second, in October 2013, entitled, ‘Passive oxygenation – the jury is still out’, concluded that,

‘…whilst there appears to be very little new published data, passive oxygenation remains a subject of lively debate in resuscitation circles and is often mentioned in articles reviewing ventilation strategies and airway management in cardiac arrest. Before it slips from view due to a lack of new evidence, it is hoped a new wave of studies are already in progress and will soon emerge as peer reviewed published studies in the near future, enabling a more conclusive assessment to be made as to whether passive oxygenation has a useful role to play during CPR. Without doubt, at the present time, the jury remains out.’

I will be interested to see the conclusions  from the SEERS/CoSTR process on this very interesting subject.

There are many other questions of interest in the ALS and BLS sections, as well as in the Neonatal, Paediatric and Education sections, including use of Impedance Threshold Devices, Induced Hypothermia and Exhaled CO2 detection and esophageal detection devices.

As a big sports fan, I am looking forward to both the European Games and the Rugby World Cup, as well as the Cricket World Cup. However, even these major upcoming sporting events are not anticipated with quite the same excitement as Resuscitation 2015 – The Guidelines Conference! I just can’t wait!

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.

REVIVE airway study – clinical outcomes and future plans

Since plans were first announced to conduct a randomised comparison of two second generation SADs to current practice in the initial airway management of out-of-hospital cardiac arrest (OHCA) in a UK ambulance service, the results have been eagerly anticipated. This can be no surprise given the paucity of high level evidence to confirm the best technique for maintaining an airway and providing ventilation in adults with cardiopulmonary arrest.

However, the primary objective of REVIVE was not to provide a definitive answer to the above question, but to assess the feasibility of the study design. If REVIVE proved the design was feasible, capable of establishing whether ventilation success can be achieved, and of measuring other key outcomes such as return of spontaneous ventilation and survival to hospital, then it would lay the foundation for a future full-scale study which might just provide us with the answer to the above question.

The REVIVE airway working group presented a poster at the International Conference on Emergency Medicine (ICEM) in Dublin in June last year entitled, ‘Early report of paramedic recruitment in the REVIVE-Airways study’. This confirmed the target of recruiting 150 randomised paramedics and stratification by experience and base station location had been successfully achieved.

Last month, in an abstract presented at the American Heart Association Resuscitation Science Symposium in Dallas, we had our first glimpse of the data related to the clinical outcomes. As this was a feasibility trial and not designed or powered to show clinically significant differences between each device or study arm, there was some discussion as to whether the clinical data should be released. However, the protocol published in the British Medical Journal (BMJ), suggests the original intention had always been to disseminate the clincial data to participants in the study and to the wider public via an open access web-site, appropriate conferences and medical journals.

A more comprehensive overview of the study results was presented at the UWE Conference & Exhibition Centre in Bristol on the 29th November. Speakers included Dr Jerry Nolan, Dr Jas Soar, Prof Jonathan Benger, Dr Matt Thomas, Dr Janet Brandling, Dr Sarah Voss and Mr Dave Coates.

The results showed no significant differences in important clinical outcomes between the use of a supraglottic airway (SAD) and usual practice (principally tracheal intubation) during OHCA. However, the trial was insufficiently powered to detect small differences in mortality. The i-gel® was superior to the LMA Supreme® on several measures, including compliance, adverse events and staff feedback. The investigators are proceeding to a large-scale trial of i-gel® versus tracheal intubation in OHCA.

For the record, the survival to hospital discharge was as follows:

     • i-gel® 10.3%
     • LMA Supreme® 8.0%
     • Usual practice 9.1%

     (p=0.73)

Survival to 90 days is shown below:

     • i-gel® 9.5%
     • LMA Supreme® 6.9%
     • Usual practice 8.6%

     (p=0.65)

Data was also presented on neurocognitive and quality of life outcomes, as well as successful device placement. There was also interesting data regarding the number of arrests attended by each paramedic (March 2012 to February 2013), which ranged from 0-11, with a mean of 3.6 arrests per paramedic. 15 paramedics did not attend any arrest during the study period. There were presentations confirming how the airway was actually managed in practice and feedback from the paramedics that participated in the study.

Successful aspects of REVIVE included proof of the feasibility of a cluster randomised trial of airway intervention in OHCA and the collection of valuable data to inform a full trial. It also demonstrated the strong support of paramedics and informed statistical calculations for a larger study. So, what next?

REVIVE 2

Professor Jonathan Benger, in a presentation entitled, ‘Further research: REVIVE 2’, confirmed the aims of REVIVE 2 as identifying differences in the primary outcome of modified Rankin Scale (mRS) at hospital discharge: good recovery (0-3) versus poor recovery/death (4-6) and differences in:

• mRS at 3 and 6 months following OHCA
• Quality of life at discharge, 3 months and 6 months
• Cognitive function at 3 and 6 months
• ROSC
• Length of stay
• Ventilation success, regurgitation and aspiration
• Loss of a previously established airway

Comparative cost effectiveness of the i-gel® and intubation, as well as the views and preferences of paramedics is also to be assessed.

It is intended the design will be a cluster randomised trial (by paramedic), with an airway algorithm for each arm. Clinical need will always take precedence and there will be an economic analysis, as well as patient and public involvement. An outline bid has been successful, and a full proposal is to follow (5th February 2014). It is intended for the trial to run for 45 months, from October 2014 to June 2018.

REVIVE 2 will need approximately 1,300 paramedics. This will probably require the inclusion of three or four large UK ambulance trusts. It is estimated the cost for REVIVE 2 will be £2 million. The investigators are ready to begin.

Four and a half years (probably 5 years before the results are reported) may seem a long time to wait for the conclusion of REVIVE 2, but given the lack of high level data currently available regarding the best airway device to use during the initial phase of OHCA, it will be worth the wait.

Use of SADs in the prehospital setting – a new review

Ostermayer and Gausche-Hill, in their review paper, ‘Supraglottic airways: The history and current state of prehospital airway adjuncts’, to be published in Prehospital Emergency Care, provide a much welcome overview on the use of supraglottic airways (SADs) in what can often be a difficult and challenging setting.

The paper begins by confirming that the widespread adoption of SADs in prehospital care ‘directly stems from their ease of use, simplicity of training, predictability, and speed of insertion’. It continues with a brief history of the use of SADs, particularly the Laryngeal Mask Airway, in the prehospital setting and includes individual overviews of a number of devices, including the Combitube®, King LT®, LMA Fastrach® and Intersurgical i-gel®.

There is acknowledgement that whilst SADs do not, in the words of the authors, provide ‘definitive airway management’, some of the newer devices do incorporate higher seal pressures than earlier options and the ability for gastric decompression, which ‘may significantly decrease aspiration risk’.

In anaesthesia circles in particular, a new classification of SADs into 1st and 2nd generation devices has gained considerable popularity and helped to highlight important differences between devices. In a review article by White et al, entitled, ‘A critique of elective pediatric supraglottic airway devices’, a 1st generation device was described as a ‘simple airway tube’ and 2nd generation as a device that ‘incorporates specific design features to improve safety by protecting against regurgitation and aspiration.’

Of course, as mentioned in an earlier blog post on the classification of supraglottic airways, designation as a 2nd generation device does not in itself confirm superiority of performance, but the classification does provide useful information about basic product design characteristics, such as whether the device incorporates a mechanism for the management of regurgitant fluid. These are important considerations when deciding the most appropriate SAD to use in the pre-hospital setting.

Discussion on the use of airway devices in the austere environment states that data collection from Combat Support Hospitals in 2008 demonstrated that 86.3% of prehospital managed airways were managed with an Endotracheal tube (ETT), 7.2% with an Esophageal Tracheal Combitube (ETC) and 0.7% with an LMA, and that, ‘although the ETC is the standard rescue airway device for the U.S. Army, poor skill retention has been demonstrated with the device among medics.’

RSA or Rapid Sequence Airway placement, the insertion of an alternative airway, such as a SAD, after pharmacological treatment with a paralytic and sedative is discussed. This is an important subject and Ostermayer and Gausche-Hill confirm that no trials have yet compared the risks and benefits of drug-assisted SAD placement to non-drug-assisted placement.

The final section of the review takes a look at airway management in Out-of-Hospital Cardiac Arrest (OHCA). Of particular interest is a reference to a Japanese study which looked at neurological outcomes in patients where an ETT was used, compared to either a SAD or Bag Valve Mask (BVM). The results are interesting, but it is important when reviewing such studies to consider the SADs that were used. Results are likely to be quite different for 2nd generation SADs such as the i-gel, compared to a 1st generation device such as a standard Laryngeal Mask Airway. In some countries like the UK, devices such as the Combitube® are now rarely, if ever used. This issue is discussed in more depth in my blog post, ‘Pre-hospital airway management for patients with OHCA’.

There are a couple of small errors in the ‘early view’ version of this paper. For example, in Table 1, the i-gel® is designated as reusable, whereas the device is in fact single use. No doubt these errors will be corrected in the final published version.

In summary, this review paper provides an interesting overview of the history and current state of prehospital airway adjuncts. The conclusion will reflect the thoughts of many with regard to this subject:

‘Since prehospital airway management devices largely evolve from the field of anesthesia, much of the medical literature regarding new devices focuses on the operating room. With the many obvious practical and clinical differences between these clinical settings, further studies in the prehospital environment are needed, specifically trials correlating neurologic outcome to supraglottic device’

Equally important will be to ensure that results for one type of SAD are not extrapolated to another with quite different design characteristics. Tempting as it may be to discuss SADs as if they are one homogenous group of devices, the reality, as this paper helps to highlight, is that the performance of each device can and will be quite different. One SAD is most definitely not the same as another. Further data regarding the use of SADs in the prehospital setting is eagerly awaited.

Pre-hospital airway management for patients with OHCA

An interesting study was published in the January 2013 issue of The Journal of the American Medical Association (JAMA), by Hasegawa et al from Japan, entitled, ‘Association of Prehospital Advanced Airway Management with Neurologic Outcome and Survival in Patients with Out-of-Hospital Cardiac Arrest’. This prospective, nationwide population based study examined data from over 649,000 adult patients in Japan who had an OHCA in whom resuscitation was attempted by emergency responders from January 2005 to December 2010.

The study was designed to test the hypothesis that prehospital advanced airway management (AAM) is associated with favourable outcome after OHCA. Advanced airway management (AAM) is defined as Endotracheal Intubation (ETT) or use of a supraglottic airway (SAD). AAM was compared to conventional bag-mask-valve (BVM) ventilation for neurologically favourable survival. The results for each group were as follows:

Endotracheal Intubation 1.0% (95%CI, 0.9% – 1.1%)
Supraglottic Airway 1.1% (95% CI, 1.1% – 1.2%)
Bag-valve-mask 2.9% (95% CI, 2.9% – 3.0%)

Return of spontaneous circulation (ROSC) and one-month survival were also assessed.

The results of this study show that among adult patients with OHCA CPR, any type of AAM (ETT and/or SAD) is associated with decreased odds of neurologically favourable survival compared with conventional BVM ventilation. The authors conclude that their observations, ‘contradict the assumption that aggressive airway intervention is associated with improved outcomes and provide an opportunity to reconsider the approach to prehospital airway management in this population’. Of course, Hasegawa et al are also careful to confirm their study has several limitations, and outline each in detail.

In an editorial in the same issue of JAMA, ‘Managing the Airway During Cardiac Arrest’, Wang and Yealy provide context for this study by discussing the reservations and potential limitations of use of a BVM during OHCA and the reasons why use of more advanced airways has been prioritised in most emergency medical services systems in North America. They also discuss the questions that have been raised regarding the wisdom of the wide use of ETT out-of-hospital. They conclude that although this study from Japan is not the first report to suggest higher survival rates with BVM ventilation, ‘the study is large, methodologically rigorous and compelling’.

In recent years, the discussion regarding the optimal technique for airway management during OHCA has generally focused on the use of SADs versus ETT, so this study certainly broadens the debate. What interested me when reading this paper was the three SADs listed as being permitted for use from 1991 onwards by emergency life-saving technicians in Japan. These were The Laryngeal Mask Airway, Laryngeal Tube and Oesophageal-Tracheal Twin Lumen Device (Combitube®). It is not entirely clear to me whether these three devices were simply referenced as examples of SADs, or whether these were the only SADs used. I presume the latter. It is a point of interest, as each of these SADs have quite different design and performance characteristics, as do other more recently developed devices, so it is quite possible that if the results for each SAD had been included individually as well as collectively, a difference in outcome between them may have been evident, and this would have been interesting to reference in the results.

Interestingly, in a study published last year in Resuscitation by Wang et al, entitled, ‘Endotracheal intubation versus supraglottic airway insertion in out-of-hospital cardiac arrest’, among the 1968 SADs used, the type of device reported for 1444 cases included 909 (63%) Laryngeal Tube, 296 (20.5%) Combitube® and 239 (16.6%) Laryngeal Mask Airway. Exactly the same three devices listed in the Japanese study.

In the UK, the picture is quite different. In the 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’. So of the three devices referred to in both the study from Japan and the study last year from Wang regarding North America, only one of them, the Laryngeal Mask Airway, is in common use.

As for second generation devices in the UK, such as the Intersurgical i-gel®, these are increasingly being considered and used for OHCA. Second generation SADs can be defined as a device that ‘incorporates specific design features to improve safety by protecting against regurgitation and aspiration’. This improved safety is usually provided by the incorporation of a gastric channel or drain tube. In addition, second generation SADs usually provide higher seal pressures than first generation devices and often incorporate an integral bite block (see my earlier blog post on November 12 regarding the classification of supraglottic airways for more details). 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 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 two studies referred to here from Japan and North America.

So what might we conclude from this? Well, firstly there appears to be a significant difference between the types of SAD in common use for OHCA in Japan and North America to the SADs in common use for OHCA in the UK and Europe. Secondly, that we should be cautious when considering the results and clinical relevance of data provided for a group of SADs, if the data for the individual devices as a sub-set is also not available. Finally, and perhaps most importantly, that we should resist the temptation to extrapolate the results for one type of SAD to another with quite different design characteristics. All supraglottic airways are not the same. No doubt the debate about the optimal technique to maintain an airway and provide ventilation during OHCA will continue.

Supraglottic airways versus tracheal intubation for OHCA

Whilst the 2010 European Resusciation Council (ERC) guidelines confirm ‘There is insufficient evidence to support or refute the use of any specific technique to maintain an airway and provide ventilation in adults with cardiopulmonary arrest.’ They go on to confirm that despite this ‘tracheal intubation is perceived as the optimal method of providing and maintaining a clear and secure airway.’ However, they also point out that without adequate training and experience, the incidence of complications with tracheal intubation can be unacceptably high.

As a result, in some countries, such as the UK, there has been a general move towards the use of supraglottic airway devices in the pre-hospital setting. This has been supported by the Joint Royal Colleges Ambulance Liaison Committee (JRCALC) Airway Working Group, who in 2008 published ‘A Critical Reassessment of Ambulance Service Airway Management in Pre-Hospital Care’, which recommended that ‘The majority of those managing patients’ airways in the pre-hospital setting should be trained to insert a supraglottic airway device instead of a tracheal tube’. The College of Paramedics outlined a number of concerns and reservations with this approach, but despite this, the use of supraglottic airways for OHCA has increased in the UK.

It was therefore interesting to read the recent clinical study published in Resuscitation, entitled ‘Endotracheal intubation versus supraglottic airway insertion in out-of-hospital cardiac arrest’, by Wang et al. The study is a secondary analysis of data from the multi-centre ‘Resuscitation Outcomes Consortium (ROC) PRIMED trial, looking at adult non-traumatic out-of-hospital cardiac arrest (OHCA) receiving successful supraglottic airway (SGA) insertion of the King Laryngeal TubeTM, Combitube®, and Laryngeal Mask Airway, or successful intubation with an endotracheal tube (ETI). It included 10,455 adult OHCA. 8,487 of these received ETI and 1,968 an SGA. The survival to hospital discharge was 4.7% for ETI and 3.9% for SGA.

The results are interesting, but as the authors themselves acknowledge, there are limitations and confounders, including the order of airway device insertion, and the number and duration of insertion attempts. The data was not intended for primary evaluation of airway management techniques, and information regarding interruptions to compressions during insertion of the airway device, ventilation rates or tidal volumes could not be accounted for or was not regarded as reliable. Despite this, the results from this paper are certainly worth further consideration and it is likely will be the subject of significant discussion amongst the Emergency Medicine fraternity and beyond.

Of course, the absolute difference in survival rates in this study was small, and whilst confirming that observational data are clearly of value, an editorial published in the same issue of Resuscitation as this study, ‘ROC, paper, scissors: Tracheal intubation or supraglottic airway for OHCA?’ pointed out that ‘randomised trials are still widely considered to be the gold standard for addressing focused clinical questions’. Indeed, Wang et al themselves confirmed that ‘prospective randomised assignment may represent an optimal strategy for comparing OHCA outcomes between ETI and SGA’.

As reported in an earlier blog post, a randomised trial comparing two SGAs (LMA Supreme® and i-gel®) to ‘current practice’ which it is believed will usually be ETI, is underway in the UK, called the ‘Airway Management Feasibility Study (REVIVE – Airways)’. It is also interesting to note that neither of the two SGAs in the REVIVE study were included in the US study being discussed here. Clearly, results for one SGA cannot be extrapolated to another, so these results are only relevant for the devices studied. Given the considerable differences in design and performance characteristics between the CombiTube®, King Laryngeal TubeTM, standard Laryngeal Mask Airway and the LMA Supreme® and i-gel®, it is possible, perhaps likely, results for the latter two devices would have been quite different.

Whilst we await the results of high quality randomised controlled trials of the use of SGAs for CPR, the conclusion given in the study by Wang et al seems entirely reasonable ‘EMS medical directors must consider patient characteristics, device efficacy and practitioner skill and training when selecting OHCA airway management strategies.’ This approach is echoed by the ERC in their 2010 guidelines ‘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’. Now you can’t really argue with that.