COVID-19 Printable PAPR (Powered Air Purifying Respirator)
Guy, have you considered replacing the ear pieces on the stethoscope for flat slightly conical discs similar to the drum or bell of the chest piece which, if resting on the airbag, would amplify the sound waves coming up and negating the need for a breach in the seal? Or maybe someone could come up with a simple wifi connected system that could be monitored remotely as well as locally?
There is an impedance issue with having the sound go through multiple material/air transitions. It's not much sound energy to work with in a stethoscope. There are commercial, electronic scopes, but you really see one of them.
In my specialty, anesthesia, I rarely use a stethoscope because I have so many other, more sensitive instruments. Gold standard for confirming endotracheal placement is sustained CO2 return. A lot of other diagnostic and monitoring equipment is attached to my patients. I can even see the start of asthma episodes or COPD issues on my CO2 waveform and lung compliance curves. For someone in internal medicine who uses less equipment, the stethoscope is more important.
Thanks for your job man! Gonna try it when I'll have my new Prusa! 🙂
Prusa MK3's create good quality prints in PETG. You will find a BunnyPAPR quite doable.
Latest design testing has been regarding the outflow filters. User buildable flutter valves on elliptical valve fittings do work well, but they need to be constructed with some care. The glove fingers need to be fairly unwrinkled and the amount that is cut off the end also affects system performance. Cutting off enough to get a slit length (while flat) of 12 to 13 mm gets near ideal flow resistance (to maintain positive pressure) and adequate total air flow to clear CO2. Cutting too much of the tip off drops bag pressure too much. Cutting off too little reduces total airflow and limits user activity level.
A mechanically defined valve is desirable to get consistent results, but is not field buildable. As the BunnyPAPR moves towards having a mass production variant, investigation of premade valves has been undertaken. We'll always have a field buildable option, but this is an alternative design direction.
Testing with modified CPR valves https://www.amazon.com/gp/product/B07NQ7GDKH shows they care nearly equivalent in total flow rate to two elliptical flutter valves. The valve closure velocity is very fast - even faster than the flutter valves. However, they arrive with a filter disc that must be removed. Otherwise, their flow resistance is too low. The filter disc can be removed by reaching in with fine tweezers and pulling them out through the valve's plastic grating. Once they are partially, a tug with needle nose pliers removes the filter disc leaving only the flap valve. A special adapter is needed to fit the CPR valves onto the BunnyPAPR output ports.
Unfortunately, CPR valves are limited availability, expensive pieces.
Today's testing is in regard to adding silicone valves as part of the BunnyPAPR's outflow ports. This would eliminate the need for valves in the bag penetrating outflow piece, but would only be doable with manufactured valve discs. In other words, not field buildable. Keeping both user options of either manufactured disc valve at bottom of output port vs user built flutter valve would be ideal. I'm working hard to make that possible.
Here are some test fittings/valve bodies being printed for M17 mask discs vs MiniValve Umbrella discs. Both are going to be tested for flow resistance and valve function.
Note also see my rightward positioned intro line on the print plate. That reduces continual wear on same section of print plate with the standard Prusa intro line.
The MacGyver team has found a VBMAX48 PFT filter that is rated for 99.99% viral reduction. It's much larger and has a much lower flow resistance than the anesthesia circuit filters. I'm printing fittings for formal measurements, but on first trial I see nearly double the flow as the Viromax anesthesia filters. More flow means better CO2 clearance and activity level.
Decided to stress test the Mosquito Magnum and dialed nozzle temp up to 300C for the 2nd half of print job. That should grow the melt zone if the heat break or airflow are a problem.
MacGuyver team completed their final UCSF COVID-19 Hackathon video
MacGyver team won the UCSF COVID Hackathon with BunnyPAPR! 😀
They are also shipping BunnyPAPR's to India and Brazil.
Current preferred configuration uses two VB48Max filters. One filter for inflow. One filter for outflow (on just single output port). The AM-Systems viral rated VB84Max filter allows nearly double the air flow of anesthesia circuit filters. Also, double direction filtering means no surgical mask is needed to protect surroundings from wearer. It's super comfortable without a mask and feeling the cooling airflow across entire face.
Also, no more valves are needed.
STL for loop changed and added new filter adapter to accommodate larger VB48Max filters.
Is this really helpful ?
Yes. 99.9% bidirectional viral filtering and fully enclosed head protection in current version. It's more protection than N95 masks + face shield.
Considering the predicament that many of our healthcare workers found themselves in -- @guy-k2 included -- this is beyond helpful. These sorts of solutions kept healthcare workers in the fight so the rest of us could sit back and post unhelpful comments minimizing their efforts. I sincerely hope that we're beyond needing PPE produced by hobbyists at this point, but I also know things may get much, much worse than we've seen so far. What @guy-k2 developed, tested (on himself, no less) and made freely available is beyond merely "useful", but shows the best of what people can do at the worst of times.
So yes, it is really helpful.