RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Steady state seated with PAPR on
Nearly two hours later with intervening emergency surgical case. This is near end of case with me standing.
The BFB0512HHA-CZMQ Delta fan is working adequately by objective measurement.
It helps if one breaths steadily. Stay calm. Breath easy.
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Thank you for this feedback. My grandfather is in a nursing home setting so he would be monitored and the risk of fire would be low.
If you wanted to put a viral filter on the exhaust instead of a flutter valve (to help prevent aerosalized virus from spreading outside of the Helmut) would that change anything about the setup?
Do the viral filters have more or less resistance than a flutter valve? I saw in some of the build photos it looked like there were dual viral filters on the exhaust. Was there a reason for that?
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
The viral filters are more flow resistance than the flutter valves. You're right that the flutter valves do not protect the environment from the wearer.
You probably saw picts from my various configuration experiments. I can tolerate the inflow + outflow filter configuration. I don't know if a 95 year old can work against that much PEEP (positive end expiratory pressure). If they can't, the solution is a negative pressure airflow room. That keeps the nasties from spreading beyond the person's room. Kind of doubt they can do that in a nursing home.
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
A few changes in the STL's. Deflector is shorter and smaller overhang angle to make easier to print. Fan flange taller to reduce noise. Halo loops now with click-in slots instead of hooks.
I'm also informed that 100 are being printed in India
HMEF with only 22 mm and 17 mm OD connectors
Added a 22 mm inner diameter bag penetrator because some HMEF's lack a 22 mm OUTER diameter end.
This is from another facility showing their HMEF has only a 17 mm OD (left in pict) and 22 mm OD (right in pict) ends. These cannot fit over the Halo PAPR's usual 22 mm OD adapter.
New, alternate Inner diameter 22 mm filter adapter accepts 22 mm OD end of anesthesia viral filter.
No more zip ties
Continuing to reduce the amount of extra materials needed to secure wiring.
Now printing up a test Halo with a sinuous wire channel in which to place the main power cable. Channel is widest at its middle depth.
If this works as planned, no zip nor twist ties are needed to secure fan wiring. All the wiring will be secured in channel or fringes.
Update Video
Update video is now online
Action Shot
We currently have the operating room crew evacuate the room while we do the higher risk, aerosol generating steps of intubation and extubation. One of my crew took a nice pict through the door of me about to extubate.
I can just do my work without even thinking about my BS Halo PAPR. The full hood and filtering protect me from generated aerosols. That lets me be safe in the room with my patient while everyone else is outside.
15 minutes later, the OR room air handler has removed 4 to 5 times the total room air volume and it is considered safe for my crew to re-enter the room.
Why Not a Face Shield and N95 Mask?
Why not a face shield and N95 Mask?
COVID-19's corona virus is different from the usual infective risk. It is able to spread via aerosolized particles, not just droplets. Droplets are the larger than spray that people envision as coming out. Aerosol are MUCH finer. It's more accurate to think of aerosolized risk like fog. When we place or remove airway instrumentation, aerosols are generated. Most pathogens we just need to protect against droplets. This Wuhan coronovirus is able to spread via aerosols generated by even talking or singing.
Think about how well a face shield protects you against fog touching your face. It really doesn't because fog (aerosol) readily travels around the face shield. It's better than nothing, because face shields do protect against droplets, but ultimately your only protection against the aerosols is your N95 perfectly sealing your nose and mouth. Your eyes remain vulnerable to the aerosol, but at least you are not breathing into your eyes.
A hooded PAPR is preferred (if available) because it completely excludes aerosols from reaching anywhere on your head. Eyes, nose, mouth, everything. PAPR hood isolates via positive pressure, so you don't have to worry whether you have a perfect face seal. Is there a small leak around my N95? Have I created a leak the mask by talking? Are my straps tight enough? Those worries go away.
There are also non-hooded PAPR's. Those don't give as complete protection as hooded PAPR's. Some PAPR's have very large hoods that extend below your shoulders.
For lower risk, non-aerosol generating procedures, lesser protection is adequate. For what I routinely do in the operating room, aerosols are likely product. Hence, a hooded PAPR is desirable. In most facilities, you don't get to use a PAPR despite the elevated risk. There are not enough PAPR's and they are too expensive. Risk management and economics force hospitals and facilities to strictly limit access to their small supply of PAPR's.
The Bunny Science Halo PAPR completely alters the supply and cost issue. It makes deployment of a hooded PAPR easier to base on desired level of protection rather than economics and limited supply.
22 mm filter adapter
More HMEF's are appearing with 17 mm / 22 mm OD ends. B5 onward STL for the bag filter adapter have been changed to make the 22 mm internal diameter adapter standard. This will fit both styles of HMEF's and has nice side effect that enhances safety. Previously, failure to close the sampling port would bypass the filter. With filter flipped 180 degrees, the sampling port is now on top side of filter. Accidentally leaving sampling port open no longer bypasses the filter.
Seam positions
I should have earlier pointed out the importance of your slicer seam position setting for the 22 mm filter adapter. We don't want the seam to be a micro-channel leading between the filter and adapter. It's particularly an issue if your k-factor isn't accurately calibrated leading to larger seams.
For the 22 mm filter adapters, adjust your slicer print settings to have random seam positions. This pictures shows why....
Mass
Here is the effective worn mass. Low 200 gms is benefit when your work shifts are 12, 18 or 24 hours long.
Yes, I sometimes get to see three shifts of RN's come through before I'm done.
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Found a commercial product named "Halo PAPR"
To avoid confusion, I have remove Halo from my project name.
Main project page address is now https://bunnyscience.dozuki.com/Guide/Bunny+Science+PAPR/4
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Original NMB fan is sold out.
Alternative fans to use....
San-Ace 109BC12GC7-1 https://www.digikey.com/product-detail/en/sanyo-denki-america-inc/109BC12GC7-1/1688-1035-ND/6191751 is good alternative if user needs higher flow (33 L/min, 60 dBA against HMEF)
A lower noise, but lower flow fan that I have worn for 11 hours is
Delta BFB0512HHA-CZMQ http://d.digikey.com/HS000xU3ppttIK40NAX00T7 This measures at 20 L/min 55 dBA against HMEF resistance.
I have worn the Delta fan while working in the OR for 11 hours. My EtCO2 at 2 hours was 40 with this Delta fan. Its mounting holes must be slightly enlarged to fit 3 mm bolts.
I would consider the Delta fan the lowest flow rate (with HMEF resistance) that is acceptable. The higher flow rate San Ace gives more headroom and would be easier for a new user to learn to use.
For comparison, original NMB fan was 30 L/min, 64 dBA with HMEF resistance.
Some Niceties
The AC charger that comes with the Tenergy battery pack has a very short lead. If plugged in to charge during work, you can't move around. Adding a DC extension cable lets me do 90% of my operating room work without unplugging.
This 10 foot extension works well
https://www.amazon.com/gp/product/B01J5RYSI8
If you need more length, there is also a 20 foot version
https://www.amazon.com/gp/product/B01J5RYSI8
If you are using a louder fan like the original NMB or the newly specified San-Ace 109BC12GC7-1, prolonged wear may be a bit hard on your ears. This Vibes concert attenuator brings down the noise 19 dB, but still lets me hear conversations and monitors in the operating room.
https://www.amazon.com/gp/product/B018WPOQSG
Regular foam ear plugs are too much attenuation at 32-33 dB. Can't reliably hear conversation or monitors with 33 dB attenuation, but 19 dB is a good balance that protects my ears and allows adequate hearing.
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
I meant Talentcell, not Tenergy for the battery pack
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
hello
is it okay to use masks?
tindungnong
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Bot?
Comparing Fan Performance
Here is a cheap means of measuring fan performance under HMEF load. This gets good relative flow and noise data for comparing fans. The absolute flow rate figure has limited precision due to way NMB 30 L/min flow rate was calibrated. Fortunately, we already know from EtCO2 and real life usage experience that the Delta HHA fan is at lower end of acceptable flow rate and NMB is yields a good flow rate.
Airflow from fan and HMEF combination is directed into sealed filament box. Outflow is not in direct line of airflow so we minimize jetting effects. I then measure outflow velocity and noise level of each fan while they are running against same HMEF resistance. None of the equipment is expensive, but this obtains objective fan performance comparison data. Basically, I use the known good NMB as the standard.
The NMB fan output rate had previously been independently measured by air displacement to be 30L/min
That was used to calculate a corrected plenum area that combined with the measured NMB velocity to yield 30 L/min.
The same corrected plenum area was then used to compute L/min based on meter/sec velocity for each fan.
I would stay away from the Mechatronix fan. It performs very badly with HMEF load despite being one of the loudest fans.
Delta BFB0512HHA-CZMQ is definitely not the same fan as Delta BFB0512HA-CZMQ despite their identical form factor.
The HHA version has better performance working against an HMEF load.
San Ace B52 109BC12GC7-1 and Sunon MF50151VX-B00U-A99 have similar performance with the San Ace being slightly quieter for same output.
RE: COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Received a desperate plea for two Bunny PAPR's from a local dentist. He can't get PPE, but really needs it to work safely.
I'll get him set up, but it illustrates the ongoing shortage for this level of PPE.
I had not thought about dentists before this. What they do is probably higher risk than my airway instrumentations.