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Open Source Ventilator
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pipe2null:
@Enginerding:  Aw maaaaan.... But I'm so comfy here!  Hehe.  Sounds great, thank you for lending your medical experience!


--- Quote from: jogri on March 31, 2020, 11:20:48 am ---
--- Quote from: pipe2null on March 31, 2020, 08:10:42 am ---On the UVC side of things, if I'm reading the numbers right from the study, it might be completely feasible to stick an off the shelf UVC lamp in an opaque can and pipe exhaled air through it without much need of anything else.  Geometries and seals will be important, but need to figure out the UVC source first.  Even if the can is 3d printed or made from chunks of PVC pipe, the plastic should probably hold up against photo degradation long enough for short term use.  I haven't found any good source of info on how long it takes UVC to kill plastic.  Also, from looking at other info, 254nm UV-C apparently eliminates ozone and does not actually create it (lower nm UV generates ozone).  I'm currently trying to find UVC lamps that might work for an in-line virus killer for CPAP/BiPAP/etc exhaled air exhaust.

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Let's say we have a system of two bags where each bag can contain the exhaled air of 15min ventilation (that's roughly 20l). When a bag is full the UVC source kicks in for 15min, disinfecting the contaminated air while the other bag fills up. We could either use fully collapsable bags to use their full capacity (bag gets squeezed->no remaining air) or we have to apply some sort of pressure to get the 20l of air into a container that is already filled with air at ambient pressure (having a pressurized container of airborne viruses kinda sounds like a bad idea).
A 20l cylinder (20cm diameter, 65cm height) has a surface area of 0.4m^2 (or 4000cm^2), that means we would need a 16W UVC source if we assume that the intensity for UV radiation of water samples is also viable for an aerosol (probably not). Yeah, that could work. I'd use a 50W source just to be on the safe side and some bigger containers to minimize the required pressure (a 20l canister would sit at 2bar when loaded with the 20l of residual air+ 20l of exhaled air), but it sounds feasible.

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Here goes my current thought:
(Potentially dangerous) Assumption #1:  The study only used a single intensity level "4016 μW/cm2 (where μW = 10−6 J/s)" which resulted in "400-fold decrease in infectious virus" in 6 min, and total eradication to detectable limit in 15min.  There is no data on the relationship between UVC intensity and required exposure time in this specific study.  If someone knows, please provide info!   ;D  Using the study's exposure intensity as the MINIMUM and if we (potentially dangerously) assume the relationship between intensity and required exposure time is somewhat linear, then increasing UVC intensity to somewhere around 900x (into the W/cm2 range, which is still do-able), the required exposure time would reduce to around 1 second compared to 15 minutes.

(Potentially dangerous) Assumption #2:  The whole "social distancing" recommendation of 6ft/2 meters (please correct if better rec's available) is because of gravity's affect on virus transmission.  If the output port of a virus killing device is piped down to the floor where a mop and bucket can periodically finish the job, then the targeted virus killing result could potentially get moved to a less conservative ~99% instead of 100% reduction in detectable virus infectivity.  So, if we went with this (potentially dangerous) assumption, then the targeted exposure time required for the lower intensity UVC used in the study reduces to their 6 minute value.

(Potentially dangerous) Combination of both assumptions:  You might be able to make an in-line virus killer that maintains enough UVC intensity for the designed geometry of the "can" to kill viruses at or above the peak air-flow rate of a patient's exhale.  Basically, kill the suckers in real-time.  You probably won't kill every single one of them, but depositing a few active viruses under a massive pile of dead virus carcasses on the floor is a major reduction in risk for anyone around a patient, whether at a hospital or at home.

Big open ended question of the unknown: Is UVC more/less/same as effective on water/air/aerosol/surface dwelling viruses?
jogri:

--- Quote from: pipe2null on March 31, 2020, 06:37:57 pm ---
(Potentially dangerous) Assumption #1:  The study only used a single intensity level "4016 μW/cm2 (where μW = 10−6 J/s)" which resulted in "400-fold decrease in infectious virus" in 6 min, and total eradication to detectable limit in 15min.  There is no data on the relationship between UVC intensity and required exposure time in this specific study.  If someone knows, please provide info!   ;D  Using the study's exposure intensity as the MINIMUM and if we (potentially dangerously) assume the relationship between intensity and required exposure time is somewhat linear, then increasing UVC intensity to somewhere around 900x (into the W/cm2 range, which is still do-able), the required exposure time would reduce to around 1 second compared to 15 minutes.

--- End quote ---

Well, seems like 30.000 uJ/cm2 is the required dose to kill spores (or anything else that could be a biohazard) that are sitting on a surface. If you want to disinfect a surface in 1 sec that would be 30 mW/cm2... Yeah, doable, but i wouldn't trust that number when it comes to airborne organisms as it comes down to statistics when you are using UV: You need to hit every organism with at least one photon (realistically 2-10 as not every impact induces an reaction). You can either drastically increase the number of photons or wait a bit.

And no, i don't recommend using UV sources in the W/cm2 range at all. Been there, done that. The problem with such light sources is that you don't know how bright they are as you just can't see them and you risk permanent eye damage when you look at them without proper eye protection (although you can feel your face getting hot which is quite scary when you realise that a skin cancer ray is warming you).

About your second point: Could be done as they need to wipe down the rooms anyway after any invasive procedure.

Effectiveness at different conditions: Water is the worst as the UV needs to penetrate it and gets attenuated (Beer-Lambert law).  Aerosol/Air: Dunno, but i'd guess that an aerosol is marginally worse as the light can also get absorbed by the water. A surface is the best option as the virus is stationary and you can control which area has gotten what amount of radiation. I could be wrong, that's just my 2ct on this topic.
bluey:
https://iit.it/iit-vs-covid-19/fi5-ventilator

https://multimedia.iit.it/asset-bank/assetfile/15783.pdf

Still trying to find completed price...
Lord of nothing:

--- Quote ---http://www.medtronic.com/openventilator
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When I rember right there was a Topic about them here in the Forum and I guess dave did make a Video to.
donotdespisethesnake:

--- Quote from: bluey on May 14, 2020, 10:06:22 am ---https://iit.it/iit-vs-covid-19/fi5-ventilator

https://multimedia.iit.it/asset-bank/assetfile/15783.pdf

Still trying to find completed price...

--- End quote ---

At least they have used an Open Source license, which is good. But they have based the design on an STM32F746 Discovery Evaluation Board. The terms of that board do not allow commercial use, nor use in a safety critical environment. https://www.st.com/resource/en/license_agreement/evaluationproductlicenseagreement.pdf


--- Quote ---The Evaluation Board shall not be, in any case, directly or indirectly assembled as a part in any production of Yours as it is solely developed to serve evaluation and testing purposes and has no direct function and is not a finished product. 
 
If the Evaluation Board is incorporated in an evaluation system, the evaluation system may be used by You solely for Your evaluation and testing purposes. Such evaluation system may not be offered for sale or lease or sold, leased or otherwise distributed for commercial purposes and must be accompanied by a conspicuous notice as follows: “This device is not, and may not be, offered for sale or lease, or sold or leased or otherwise distributed for commercial purposes”.
 
You shall not use the Evaluation Board in any safety critical or functional safety testing, including but not limited to testing of life supporting, military or nuclear applications. ST expressly disclaims any responsibility for such usage which shall be made at Your sole risk, even if ST has been informed in writing of such usage. Unless expressly designated in writing by ST as suitable for use in testing automotive or aerospace applications, You shall not use the Evaluation Board in such testing.
--- End quote ---

The NHS has rejected PPE from Turkey, because it did not meet requirements. I mean, that is just cloth and plastic, hardly anything to go wrong. They have also rejected Chinese made ventilators as sub standard. Ventilators operate with oxygen, the last thing you want is for them to catch fire.

I very much doubt they are ever going to risk untested or unapproved ventilators. I still feel confident in saying that none of these "open source" ventilators will ever get used in a real hospital environment.
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