Considerations for using viral/bacterial filters during newborn resuscitation.
With the current COVID-19 crisis, the importance of correct PPE has quickly risen to the forefront of all governing health bodies new guidelines. While adequate PPE can greatly reduce the risk of transmission of the virus, stopping it from aerosolizing in the first place provides an extra layer of protection that could be invaluable.
As such, many government health departments have released statements advising on the best course of action to avoid further spread of the virus through aerosolization. On the 25th of March, NSW health advised that healthcare workers stop and first “make sure that non-invasive ventilation is the most appropriate intervention” as CPAP/BIPAP have been found to generate high levels of aerosolised droplets. QLD health subsequently released a document titled “Maternity care for mothers and babies during COVID-19 pandemic” to further address these issues in cases specific to maternal and newborn care. In this document, it is recommended that all mechanical and manual ventilation devices use a viral/bacterial filter.
While this sounds like a good idea, there are multiple things that need to be considered, especially when dealing with the fragile physiology of a premature baby:
Dead Space
Dead space is a large factor when it comes to newborn resuscitation. It is the amount of air in the ventilation circuit that is not involved in the gas-exchange in the lungs. Adding extra items, such as viral filters, in between the ventilation device and the patient increases the dead space in the circuit and this can have various repercussions. An increase in dead space means the pressures delivered by the ventilation device need to be larger in order to drive the right amount of flow, and thus volume, to the baby’s lungs. Traditionally, there has been no clinically viable way to measure the volume being delivered to the lungs during resuscitation and thus small pressure manometers (if available) and ‘perceived’ chest movement have been the only way to see any quantifiable measurement of what is going on in the babies airways. This combined with the fact that healthcare workers are taught to adhere to pressure guidelines when delivering resuscitation means that the pressures that they are trying to target may no longer deliver the needed volume to the lungs when a viral filter is in place.
Humidity & Work of Breathing
When using a manual resuscitation device such as a self-inflating bag or t-piece resuscitator, a viral filter is recommended to be inserted directly between the resuscitation device and patient (as recommended by QLD health). As such, whether using a humidified circuit or not, the filter will come into contact with moist, humid air exhaled by the patient. Some filters are rated for use with humidified air, but for others, this can be a large issue.
As the filter saturates, there is the concern that this will affect the mechanics of the system. For a mechanically ventilated newborn, one concern is that when the filter is saturated, the resistance in the ventilator circuit increases. When the resistance increases during pressure-assisted ventilation (where the ventilator does not completely breath for the patient but rather helps them) this means that the patient must work harder to breathe, potentially leading to respiratory failure (read more here).
Device Compatibility
This is another issue that has come up multiple times, especially during the COVID-19 crisis. I mentioned in a previous write-up about how some self-inflating bags are not rated to have both a PEEP valve and viral filter simultaneously and the same applies to other devices and add-ons. One of the most common manual resuscitation devices after the self-inflating bag is the t-piece resuscitator. One model, the Fisher & Paykel ‘Neopuff’, is commonly used in neonatal intensive care units throughout all of Australia, and it is one example of a device for which the manufacturers does not recommend the use of a viral filter with their device.
Another device that has had a large impact in the neonatal intensive care unit is the end-tidal CO2 monitor/detector. This particularly applies to small colourimetric models such as the Nellcor. These devices allow clinicians to see when there is gas-exchange in the lungs by a simple colour change when there is CO2 in the expiratory gas flow. But you guessed it! Devices like this are also not recommended for use with a viral filter.
Respiratory Time Constant
The final consideration I will touch on is the effect of adding a filter on the respiratory time constant. This is getting a little bit deep into spirometry and pulmonary mechanics but it is important to understand that newborn lungs are dynamic. From the moment a baby is born, to the time they are happily breathing on their own, their lungs undergo a number of changes. This dynamic system is incredibly complex and quite fragile, changing the way the air flows and adding in extra dead-space and resistance can thus have a dramatic effect. This increases the time it takes to fill the patient’s lungs with air, and when clinicians resuscitating are working on guidelines to provide ventilation at a certain rate, issues such as auto-peep become even more prevalent.
Conclusion
COVID-19 has brought many issues with resuscitation devices into the spotlight and highlighted the importance of understanding the way resuscitation devices work and how we can best use them. This is why our team at ResusRight is working to provide quality research, carefully inspecting and testing resuscitation devices (such as the self-inflating bag and mask and the t-piece resuscitator) and translating that into better education of healthcare professionals through devices such as the Resuscitation Training Monitor. It is crucially important that our frontline workers are as best equipped as possible when a pandemic like COVID-19 comes along and that includes ensuring that the tools they need can be relied upon and the training they have received is as efficacious as possible.
