Sealed Supraglottic Airways – A concept to improve the safety of laryngeal mask airways amidst the COVID-19 pandemic

With the current impact of the COVID-19 pandemic being felt around the world, there has been an explosion of ingenuity and practical solutions to otherwise longstanding issues experienced by frontline emergency care providers. Aside from the crowdsourced PPE revolution, perhaps the most radical ideas have aimed to address issues relating to airway management in the face of a threatening respiratory virus. With numerous specialty groups and inter-professional agencies stating that the majority of airway protection and ventilation procedures expose healthcare providers to increased risk through the generation of aerosols from the patient’s respiratory tract, the importance of searching for ways to improve safety in airway management can’t be understated.

To generalise a number of current guidelines, the placement of a cuffed endotracheal tube with the immediate attachment of a viral filter appears to provide the best protection against the ongoing generation of respiratory aerosols. However, all relevant guidance acknowledges that the process of inserting an endotracheal tube is one of the areas where clinicians are at the highest risk due to exposure. To address this issue, many departments are producing and refining their own COVID specific procedures to guide safe intubation (my own included).

While these procedures are essential in keeping clinicians safe, many fixate on the safe delivery of the tracheal tube with relatively little modification to the use of rescue devices such as the laryngeal mask airway (LMA). Perhaps more importantly, a number of similar guidelines are being produced focusing on the management of cardiac arrest in the COVID era with an enduring focus on the use of cuffed tracheal tubes as the go to airway. This is an important shift in practice for a number of areas where LMAs are routinely used as first line temporising airways both in the context of cardiac arrest and more broadly as airway rescue devices.

While the suggestion that LMAs should be replaced wherever possible by endotracheal tubes in the current climate (April 2020) is sensible, there are some important complicating factors. While cuffed tracheal tubes invariably reduce the risk of aerosol generation if used correctly, they are significantly more challenging to insert requiring a high degree of technical skill (even before the COVID checklist makes an appearance). They also require at least two healthcare providers to be present in the immediate vicinity of the patient’s airway for a number of minutes to insert and secure the tube. An LMA by comparison is nearly a complete inversion of these factors. An LMA can be rapidly and reliably inserted by a single operator in most settings, however, its supraglottic positioning renders it less protective against aerosols. These factors are important to balance, especially in the context of a high-risk scenario such as a cardiac arrest where confounding variables such as external chest compressions further increase the risk of exposure to those involved in managing the airway.

While the end result of a cuffed endotracheal tube correctly sited appears superior to the application of positive pressure ventilation to even a well-positioned LMA, the opportunity cost and potential risk to additional airway providers makes it well worth exploring alternative options for improving the safety profile of a rapidly inserted second generation LMA (like the Intersurgical I-gel).

The major logistic difference between a cuffed tube and an LMA is the presence of a complete occlusion of the passage of air around the internal lumen of the device. Therefore, one theoretical way to improve user safety of a supraglottic airway in the context of aerosol generation would be to somehow seal the upper airway around the LMA to prevent expulsion of aerosolised virus particles via the nose and mouth.

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If not for the presence of the large plastic device in the patients mouth, the easiest way to prevent the expulsion of germs from a patients airway is through the application of a simple face mask. This concept can be extrapolated for use in conjunction with an LMA by cutting a small slit in the middle of a surgical mask and applying over the top of the tube, however the seal would remain inferior to that of an endotracheal tube.

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A potentially viable solution to improve the safety of a simple LMA can be achieved by using simple occlusive dressings (such as large tegaderms) to form an occlusive seal AROUND the body of the LMA, covering the patients nose and mouth. This can be achieved quickly and easily with equipment readily available in almost all emergency departments.

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Procedure

  1. Don Appropriate Airborne PPE
  2. Pre-attach a viral filter to the LMA
  3. Pre-load a gastric tube into the gastric port of the LMA (this allows for rapid gastric decompression and additionally seals the gastric port to prevent aerosol escape).
  4. Insert LMA as usual
  5. Seal the nose and mouth with tegaderms:
    1. one over the chin covering the bottom lip
    2. one from the nose down covering the nares and upper lip
    3. be careful not to occlude the internal lumen of the LMA
  6. Commence Ventilation as required
  7. Advance the gastric tube and confirm placement (suction as required)

When compared to a simple surgical mask applied over an LMA, an occlusive seal using transparent dressings has a number of hypothetical advantages. The first and most important benefit relates to the security of the seal. While a surgical mask is designed to stop the projection of large droplets, it is not intended to prevent movement of finer particles such as those related to respiratory aerosols. While it should be noted that occlusive dressings are not specifically designed to protect against the movement of airborne viruses, the seal produced using adherent dressings with good coverage appears in theory to be superior to that of a simple surgical mask.

Additionally, the occlusive dressings have the added benefit of visibility. Where the airway operator is essentially blinded to the patients mouth and nose using a surgical mask, occlusive dressings are transparent allowing of visualisation of complications such as vomit in the upper airway. Potentially a rigid suction catheter may be delivered through the dressing to clear debris with minimal disruption to the integrity of the seal.

In many second generation supraglottic airways including the I-gel, a gastric port is included to allow access to the stomach for gastric decompression. In the context of a high-risk respiratory virus, this gastric port provides an additional point of egress for aerosolised particles. To mitigate this risk, I would advise preloading a gastric tube into the gastric port to the point where the tip of the tube is just about to exit the distal end of the LMA). This allows you to prevent gas from exiting through the gastric post whilst additionally streamlining the process of gastric decompression to both improve ventilation and prevent vomiting. The process of pre-loading the gastric tube has a negligible impact on the handling of the LMA and would be unlikely to negatively impact successful insertion or ventilation, provided the gastric tube remains inside the LMA until the airway is fully inserted.

While a suitable seal at the level of the nose / mouth may be easily achieved in a clean shaven patient, the presence of facial hair will make occlusion of the airway around the tube impossible. Shaving facial hair would improve the potential viability of this technique (as well as the viability of other airway / breathing adjuncts such as face mask and non-invasive ventilation).

One additional challenge associated with the use of occlusive dressings to seal around an LMA is the potential for user contamination when removing the device. While this should be considered, with careful removal of the outer margins of the dressings from the patients skin the tegaderms would ideally cause minimal interruption to the standard removal procedure of an LMA. In most cases where an LMA is used in the emergency setting (i.e. cardiac arrest, failed laryngoscopy etc), the device will be used temporarily until it can be removed to facilitate further attempted insertion of a tracheal tube under more controlled circumstances. Tegaderms or no tegaderms, in each of these cases the LMA will need to be removed from the airway which is a significantly more worrisome prospect in terms of user contamination. For this reason, where an LMA is indicated, the use of occlusive dressings to enhance aerosol protection does not appear to pose significantly increased risk compared to the simple process of LMA use in isolation.

While I feel slightly ridiculous writing this down, it is absolutely essential to note that under no circumstances should occlusive dressings be used to fully occlude a patient’s airway (i.e. completely covering the nose and mouth without an established airway being inserted prior). In very real terms this would cause a person to suffocate and die – do not do this. In this example tegaderms are only used to cover the nose and mouth AROUND an LMA (which maintains the flow of air to the lungs through the internal lumen of the tube – like a snorkel). This post is only intended as a concept for interpretation by healthcare professionals with a high degree of skill / training in airway management. If that isn’t you, thank you for taking the time to read this and I hope it was informative – but don’t stick anything over your mouth or anyone else’s mouth that wasn’t designed to be there (like a surgical mask or a cool bandana).

Please note, like many novel concepts that have emerged during these challenging times, there is no immediately available evidence to support this concept – it is merely an idea shared for the potential benefit of our fellow clinicians. Always follow your institutional policies and procedures and exercise your professional judgement where considering any novel processes.

Special thanks to Tye Parker for knowledge and imagination in helping to design this concept.

Stay Safe

Jeremy

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