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.