A New Schema for Extraglottic Devices

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This study had two main objectives.  The first was to create a novel extraglottic airway device misplacement classification system, and the second was to then retrospectively review a cohort of deceased patients and apply this classification system.

 For the purposes of this discussion, we will use the term “extraglottic airway device” (EGD) as a general term to encapsulate devices such as the LMA, King-LT, and i-gel.  These EGDs are typically further subclassified into either “supraglottic” (ex: LMA, i-gel) or “retroglottic” (King-LT) devices.  Over the last 3-4 decades, the use of these devices has increased exponentially in the field of Emergency Airway Management.  In particular, the newer devices have seen a significant increase in their use in the prehospital arena and with EMS services.  As some of the potential complications and downsides of endotracheal intubation have become more studied and well-known, the prevalence of EGD usage has increased in response.  EGDs have even become the preferred airway device in some services and situations, particularly in Out-Of-Hospital Cardiac Arrest (OOHCA).

One of the main benefits of these devices is that they can be placed quickly and “blindly” – meaning that you don’t need a laryngoscope or other device to place them.  This makes them well-suited for rescue airways or for time-sensitive airway interventions (such as when active CPR is in progress).

Despite how effective these devices are, and the tremendous benefit they have brought to our practice – it’s important to remember that nothing in medicine is a panacea.  This is the first published study looking at how often these devices are misplaced and what potential consequences this might have on patient care.  

Multiple previous studies have described and categorized endotracheal tube misplacement, and so the team was able to review and adapt these prior classifications to the specifics of EGD placement.  The device misplacement classification system created by this team had 6 categories – depth, size, rotation, device kinking, mechanical blockage of ventilation opening, and injury.  These then each had varying degrees of error within those categories. The team used a retrospective review of postmortem CT-scans to both derive and validate the system, as well as to apply the individual scores for the cases involved in the research study.  There were no exclusion criteria. 

The primary outcome of the study was to create this EGD misplacement classification system.  The second outcome was the description of the type and frequency of misplacement, using this system.

Results

They reviewed 341 patients/decedents.  The median age was 47.0 years.  65.1% were men.  The most common cause of death was suspected to be cardiovascular disease, followed by overdose and then trauma.  77.7% of the patients had their deaths pronounced in the field, whereas the remained 22.3% were pronounced in the hospital.  The most common devices were supraglottic devices with inflatable cuffs (such as the LMA), followed by the i-gel and then the King-LT.  

  • 14.4% of the cases were found to have definite misplacement that would have required immediate repositioning in order to properly function.  14 of these cases met 2 of the misplacement criteria, while 35 met 1 of the criteria – with the most common being incorrect depth.

  • 19.6% of cases were found to have an inappropriate depth, although the majority of those were felt to be “shallow but possibly still ventilating.”

  • 9.1% of cases had a mechanical blockage of the ventilation opening, with the majority of those being an obvious mechanical blockage which was later found to be a large foreign body (such as food) obstructing the ventilatory outlet.

  • 6.2% of cases showed an injury that was likely caused by EGD placement.  5 of those cases were categorized as a major injury, with pharyngeal or esophageal perforations noted.  Other cases had hyoid bone fractures.  All of the cases involving major injuries were involving the King-LT device.  

Limitations

By use of postmortem CT’s, this study is obviously limited only to patients who did not survive.  And so this study does not provide any insight to the incidence of misplacement or complications in patients who survived.  They were also unable to identify any cases where an EGD was removed before death was pronounced or removed and then replaced with an ETT – therefore the incidence of misplacement or injury may have been underestimated.  Another limitation was that it was not recorded who placed the EGD, and so it is not known if the EGD was placed incorrectly by EMS and then unrecognized in the hospital, or it was placed incorrectly in the hospital.  It is also certainly possible that some of the misplacement occurred after the patient’s death, in transport or during handling of the body.

Finally, the study was limited geographically, as it only reviewed cases in New Mexico.  Therefore, the results may not be exactly generalizable to other EMS and hospital systems.

Discussion

There is obviously a lot that could be discussed, and many possible take-aways from this study.  As we discussed earlier, use of EGDs has increased exponentially over the last several decades.  As some of the complications from endotracheal intubation and bag-valve-mask ventilation have been increasingly studied, EGDs have become the default intervention.  As with most new treatments in medicine – the potential benefits are often recognized before potential harms.  This study does an excellent job to show that placement of EGDs is not necessarily an easy process without any potential harms.

Having said that – EGDs are still the best option for many patients.  Where I think this study really shines is that it helps highlight the different ways in which EGDs can be misplaced, and we can use that in training and in practice to lessen the chance of it occurring in the future.  For instance – we now know that some of the most common issues with EGD placement are too shallow of a depth, kinking of the device, as well as foreign body obstruction.  We can use this information to better understand how to place these devices as well as the complications to look for.

In Critical Care Transport in particular, it is not uncommon that we arrive to find patients with an EGD placed by our EMS or hospital colleagues.  My personal practice is to have a bias towards continue to use that EGD – provided that it is functioning correctly.  This is of course a bit of a subjective/gestalt judgement, but there are multiple data points we can collate to make a judgement of its effectiveness.  Chest rise, oxygenation, and EtCO2 waveforms can all help give us a sense of the ventilation and oxygenation being achieved.  In particular, I always try to also assess the EGD itself for depth and rotation.  I will also evaluate the oropharynx and elicit if there is any known history of vomiting or possibility of a foreign body.

If we feel the EGD is not functioning properly, then there are three main courses of action.  The first is to remove the EGD, perform corrective maneuvers (suction the airway, reposition the airway, etc.), and then replace the EGD and then reassess for function.  The second would be to remove the EGD and perform endotracheal intubation (with a caveat being that there are some methods to intubate alongside or through some of the EGDs which we won’t discuss here).  If intubation is chosen, it is important to recognize that multiple studies show that EGD placement is a good predictor for a difficult airway, not only due to pre-existing factors but because many EGDs can cause tongue swelling and airway edema with placement and prolonged use.  Finally, one could consider performing a surgical airway “over” the EGD.

Overall, EGDs are still an excellent option for many patients.  However, as with all interventions, they need to be educated, trained with, and closely monitored during their use.  This paper goes a long way to helping us understand the potential pitfalls of EGD use, and will definitely lead to further research and improvements in Emergency Airway Management.

 

As Cal Newport said – “Do less.Do better.Know why.”

Authorship

Andrew Cathers, MD - Dr. Cathers is an Emergency Medicine Physician as well as Flight Physician, and Assistant Medical Director of University of Wisconsin Med Flight with a focus on Education and Training in their Program. He is kind enough to share recaps of recently published HEMS literature which should be posted quarterly here on TamingtheSRU