CPAP/BiPAP negative pressure tent/enclosure
I just had a call with Eric Goralnick, director of emergency preparedness at BWH, about testing our folded isolation box in the ED. They're interested in testing the box, but he suggested we also consider an upgraded version designed to eliminate aerosol spread from patients on nebulizers or CPAP/BiPAP machines. Briefly, hospitals have updated protocols to essentially ban these common respiratory interventions on any patient that presents with COVID-19 symptoms to avoid putting hospital staff at risk. Eric said that currently ~10% of these patients end up testing positive; the remaining 90% are thus being deprived critical treatment for COPD, congestive heart failure, and many other ailments. He believes in the short and long-term such a design could be a game-changer, since it frees up PPE, reduces caregiver risk, and opens up mid-range treatment options prior to pushing doctors to rely on invasive ventilation.
A few design notes from the call and an earlier discussion I had with a friend about a similar idea:
- a clear (or mostly clear) enclosure sits on top of patient's head and upper torso, kind of like the isolation box
- an air outlet connects to a suitable filter and a blower to constantly evacuate ambient air and any aerosols from around the patient
- make-up air is provided by poor sealing around the enclosure's base and (potentially) vents or flap valves in the enclosure
- bonus points for a folded design that avoids the need for complex fabrication/framework and keeps the system cheap/lightweight
- for CPAP and BiPAP, the patient is sitting up at an 80-90 degree angle, but the design should also accommodate prone patients
- does not require online caregiver access -- i.e. it's okay to need to shut down the blower and remove the enclosure to access the patient, but this process should be easy
- does not require modification to bed, bedding, etc -- should be as universal as possible
- need some way to demonstrate that it is safe and effective
- some patients get claustrophobic so it should be spacious, and not too noisy
Recently trained Simulia folks (@erik @amiraa @Tourlomousis) I think this is a case where good simulation is the key and should drive the design. This is analogous to a fume hood which is only effective when you don't block the inlet louvers and the sash is kept below a certain height. We'll need to dial in air flow rates, and potentially build in a mechanism to adjust the blower velocity to maintain good aerosol scavenging since the seal between the bed and the box is uncertain and highly variable. Let me know if you're interested and have time to help.
Other thoughts? I've got more ideas but want to know what folks think.