COVID-19 Printable PAPR (Powered Air Purifying Respirator)  

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

Here it is in operation....

Positive pressure, virus filtered air within.

PAPR provides both airborne and direct splash protection. Anesthesia filter is higher grade filtering than N95 mask.

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

A bit easier to understand on Dozuki

https://bunnyscience.dozuki.com/Guide/HALO+Respirator+(Buildable+PAPR)/4?lang=en

Why a medical doctor designs this instead of a mask or face shield

To help the lay 3D printer understand why a medical doctor who works with ventilators and airway management designed this instead of a mask or face shield, here are what drove the final design.

* Supply virus free breathing gas as clean O2 or filtered through standard ventilator circuit virus filter.
* Use non-permeable, yet readily available barrier (plastic bag) as air tight hood protecting entire user head.
* Use positive pressure gradient rather than printed material perfection to exclude contaminated room air.
* Unlike a completely 3D printed mask, does NOT rely on printing perfection to create safety barrier.
* Preserve cleanliness of 3D parts inside HALO to facilitate re-use and extended life.

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

My hospital despite taking care of the largest number of COVID+ patients in the Seattle area, has not received a shipment of masks nor gloves in two weeks. Supplies are running low and requirements for PPE protection are rising.

We're going to deploy the Halo respirator in O2 supplied configuration this week. That will protect us and the SINGLE N95 mask the hospital can issue. That N95 has to be reused until it is obviously soiled or damaged.

My partners perform intubation and other airway manipulations multiple times/day. Each time, we're just a foot away from aerosolized particles generated by the airway manipulation. Fully filtered or clean air is needed in addition to eye protection. We just don't have enough PPE equipment. We're being forced to use the HALO. At least, I'll know every HALO bag will be clean and under positive pressure seal. I don't know how good our reused N95's will remain.

Deploying Now

Here are the Halo kits in oxygen source configuration for distribution to my anesthesia partners. These are going to provide the aerosol and splash protection needed for intubation and extubation. Both exciting and sad to be in this situation.

The kits for this config are only the halo, flutter valve, and valve deflector. Still, it's a lot to print for 60+ docs. We'll need a LOT more before we're done. 

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

The transmissibility of this virus via micro-aerosolization is real. Anything below N95 level filtration is probably ineffective. .

Recent change to 51 mm blower fan has been a huge step forward for the BS HALO's fan PAPR configuration. It now provides virus filtered air in more at adequate rate for larger users. This system uses a known medically effective, regulatory approved, viral filter to do its filtering. Combined with positive pressure enclosure of entire head, it is intended to be actually protective against micro aerosolized risks. By using positive pressure, the system achieves full seal without parts perfection.

I'll be presenting the Bunny Science Halo PAPR for a COVID-19 Technology medical conference later today. This is a chance to rapidly get more functional PAPR's into provider's hands. 

Guy Kuo, MD

Matrix Anesthesiology PS

Bellevue, WA USA

aka Bunny Science / guy. k2

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

Kia ora Guy,

congratulations on your excellent work! I am just in the process of getting my fellow intensivists interested here in the south of Aotearoa/New Zealand.

A few questions though:

Doesn't get the whole assembly a bit top heavy when used in the powered fan configuration?

Do you have any suggestions on how to manage the fresh gas supply when entering a room? Do you hold your breath until you connect to a wall supply? Do you use a small gas cylinder in a SCUBA or firefighter configuration? Our common small O2 cylinders would last about 45 mins @ 10l/min (2.9l WC/150bar).

I guess it would become a bit awkward trundling a D size air cylinder around with you and that wouldn't solve any cleaning problems when entering/exiting isolation areas.

Kia kaha!

Hansjoerg

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

Kia Orana!

Doesn't get the whole assembly a bit top heavy when used in the powered fan configuration?

It's not too bad. Total mass in 51 mm fan configuration including bag and filter is 200 gm. I gone about  for hours from building to building wearing the Halo in fan PAPR mode.

Do you have any suggestions on how to manage the fresh gas supply when entering a room? Do you hold your breath until you connect to a wall supply? Do you use a small gas cylinder in a SCUBA or firefighter configuration? Our common small O2 cylinders would last about 45 mins @ 10l/min (2.9l WC/150bar).

Flow rate requirements are indeed pretty high if using a gas supplied configuration. I would actually expect to be 12 L/min for adult male. SCBA is actually how I first tested the Halo. Mobility would require a tank or fan config. Tank is obviously obnoxiously limiting.

If at all possible, I would build with the blower fan config. It is much nicer in terms of mobility. Battery pack fits in rear pocket of my scrubs and will charge from AC adapter even as the AC adapter charges the pack. 6000 MAH 12 volt lithium pack is what I'm using. Gets about 3 hours run time, but I would not want to use more than half of its charge/cycle. It's fine going from OR to PACU.

If forced to use tank due to lack of ventilator filters or fans, you're right in that a small tank is only option.

BTW, DO wear at least a surgical mask under HALO PAPR. It does not filter expired air.

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

BTW, one incidental finding during testing with O2 fed configuration is that the FiO2 is actually 95 to 97%. Beats a non-rebreather in FiO2, but must have enough flow for Co2 clearance. Obviously would need to be in negative flow room, but Halo can also be used to neatly replicate the head in a jar oxygen deliver method.

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

One more tip. Because there is always the risk that the 3d maker is themselves shedding virus but is asymptomatic, I have been sealing the printed parts in a bag and keeping them at 65C in my filament dehydrator (a repurposed food dehydrator) x 4 hours before distribution to my partners.

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

Thank you so much for your quick replies!

Gas supplied config should be doable in an OT environment, at least for the Anaesthesiologist during airway management as long as she/he doesn't have to move too far away from the anaesthetic machine. Y-piece and separate flow regulator on the wall outlet with a few meters of tubing.

Will have to find a supply of fans, which could be a bit difficult as I guess electronic parts suppliers are not considered essential businesses at the moment. (NZ is in a relatively strict lockdown).

Will keep you and the community posted in case we use the device and have anything useful to add.

Currently running a print in ASA, that should be more resistant to disinfectants than PET(G) and could possibly be disinfected with UV(C).

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

I just uploaded versions of the Halo small and large with integrated 51 mm fan mounts. No O2 line clips. Basically, streamlined to avoid printing unneeded features for fan PAPR config.

Will upload std and small later tonight without fan mounts but including O2 line clips.

If looking for a blower fan, try to find one with 15o to 200 pas static pressure capability. I have spec for one I used in the instructional write up. I would not even bother with the tubaxial fans. Just not enough static pressure capability to be used comfortably.

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

Guy - Awesome stuff. As usual, you're miles ahead of where I am so I can only admire the stuff you put together!

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

Thank, Bob. In this case, I have and unfair advantage of actually being a critical care path doc who uses this type of equipment for work. I work with ventilators and airway equipment every day. I also have a good appreciation of disease process and spread. There are a lot of little behaviors we get engrained to avoid differing modes of contamination. It does not all come naturally. Watch most people and you'll see them self contaminate again and again.

Nice also hooking myself up to gas monitoring for a couple hours to test how the HALO's gas flow is affecting physiology.

I have a lot of "skin in the game." We're doing high risk aerosolizing airway procedures with barely adequate PPE supplies. Our professional society has determined our infection risk is so bad that we must treat EVERY patient as having COVID-19. That means using full PPE on every single interaction. That would burn through a lot of PPE doing it right. The hospital does not have enough PPE to support doing that. 

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

Guy, any thoughts on the community 3D printing efforts? I'm participating in Masks for Docs in MA. They're recommending the NIH shield, essentially the Prusa design with an angled top shield. Read some posts from nurses asking that we please stop printing anything without a top shield. Happy to print away and contribute, but want to ensure the stuff is actually usable and safe.

Also, thoughts on how durable the shield should be? I had one with a low perimeter count snap along the frame while cleaning, but another with 4 perimeters can be tied in a knot. I've been told that's overkill.

Thanks, and keep up your good work. Stay safe!

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

Face shields are an adjunctive protection for face against splash and large particle. Think of them as something that is to keep incoming spray from reaching your face. When you work around patients, you often lean forward and that places the top of your head in harm's way. Hence, their desire for more protection from above. That still leaves entry from below as an issue. So, more complete protection is via a hood rather than a face shield.

However, hoods are less convenient and harder to obtain. For lower to mid range exposure risks, an N95 mask (for airborne protection) and a face shield is a workable compromise. 

Durability isn't a huge issue. These are not meant to withstand impacting objects, just keeping splash and spray away. Whether the facility even wants to clean and reuse face shields depends on their level of desperation. If the shield is able to withstand a few cycles with cleaning solutions, it would be great, but reuse is a risk for any contaminated PPE. You clean and reuse if you have no other choice.

Best is to check with the facility and see what they actually want. 

For the above usage reasons, I designed the HALO PAPR to adequately defend user even in a higher risk contamination scenario. 

Omnidirectional splash protection + airborne micro-aerosol protection + disposable barrier is really we'd all love to be at. There simply is not enough high level PPE for everything. So, equipment gets triaged to place highest barriers in riskiest situations. Unfortunately, this virus is so contagious, going with lower level PPE in what seems a safer situation can still lead to exposure.

Hospitals also must withhold distribution of PPE now because we anticipate things to get much worse. No guarantee of more PPE will arrive, so they try to preserve stock for later. Which means right NOW, you get to work with less than ideal protection because those supplies are held back for things getting worse.

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

Good Morning,

I allow myself to chip in on the usefulness discussion here.

I tried to make that point elsewhere already. The "top mounted" shields are potentially useful splash protection when the splash comes from the direction of the shield. Depending on the relative position of the health care person and the patient. With a single mounting point, that is also the pivot point of the shield you will always generate a gap in the protection. If you're higher than the patient then the gap will be at the bottom of the shield. Taking into account our natural response of tilting the head backwards and away from the perceived danger the gap will widen.

Best protection is definitely guy's design or similar. I continue to propose an alternative design that provides protection in an upward direction. That would mean some type of collar that supports an upward shield. This would also stay between the user and the aerosol source if the user turns the head (another natural protection response in case of splash). The "top mounted" solution presents a huge gap directly into the spray in this scenario.

Just churning out things that give people a false sense of limited security gives everybody a nice fuzzy feeling of having made some contribution. But some people should actually pause and do some thinking (as you did splendidly guy!) before blindly rushing off into activism. The sense of urgency is a compelling driver and some help is better than nothing, I appreciate that. But there are enough really smart guys around here that could come up with something better than the "but we've always done it this way" approach.

End of rant!

RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)

Hansjoerg, thanks for expounding from the perspective of an intensivist who actually faces the risks at work. I think you conveyed some really important details that are easily lost.