DIY ventilation design.

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Boustrophedon
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DIY ventilation design.

Post by Boustrophedon » Tue Mar 17, 2020 12:00 pm

I have a collection of motors, gears, sprockets and chain, wood, hoses etc, so how hard can it be to make a basic mechanical ventilator?
I have a few questions, basically I need a mechanical design brief. I'm talking basic 1950s tech here, no computers/embedded processors, just mechanical.

1) How many breaths per minute?
2) What volume?
3) What pressure?
4) How does the air get out of the patient's lungs again? Do I need a phased outlet valve or would a correctly size orifice do?
5) how does the tube "connect" to the patient?
...zoologically improbable and/or terrifying to small children.

Pishwish
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Re: DIY ventilation design.

Post by Pishwish » Tue Mar 17, 2020 12:40 pm

Someone more qualified than me will answer your questions. You probably know this, but here are some interesting resources: mit design hackaday
open source project
but
biocompatibility
twitter thread, with wood lung idea

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Bird on a Fire
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Re: DIY ventilation design.

Post by Bird on a Fire » Tue Mar 17, 2020 12:51 pm

I posted this on another thread: the Pandemic Ventilator Project https://panvent.blogspot.com/

I'd expect that the trickiest part might be making something that can be safely lodged down somebody's throat for weeks and sterilised effectively between patients (if necessary), but I'm not any sort of engineer (nor am I even that practical).

It's a good idea, though, if a lot of practically-minded tinkerers can be harnessed to help out with the shortage of PPE.
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Gentleman Jim
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Re: DIY ventilation design.

Post by Gentleman Jim » Tue Mar 17, 2020 1:08 pm

An endotracheal tube is a flexible plastic tube that is placed through the mouth into the trachea (windpipe) to help a patient breathe. The endotracheal tube is then connected to a ventilator, which delivers oxygen to the lungs.
This is the bit that is sterilised - most are PVC
https://www.verywellhealth.com/endotrac ... on-2249093
Last edited by Gentleman Jim on Tue Mar 17, 2020 1:19 pm, edited 1 time in total.
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lpm
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Re: DIY ventilation design.

Post by lpm » Tue Mar 17, 2020 1:17 pm

Serious suggestion: a TV show.

I think it's James May who does those "take it apart and see how it works" programme?

Give him one, he and a team takes it apart on camera, all live on TV or YouTube. People gather on a forum afterwards, saying my factory's shut down right now but I could open it up and make that bit, haven't a clue about anything else.

Or do a hospital bed, showing all the components - one small company says it can make the structure and wheels but nothing else, another says it can do the motor for the tilting mechanism but can't do a controller, another says it saw the bit about how the controller was made and they already have every component in stock except for the plastic case, and so on.
I'll miss him after he's died in the pandemic

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Re: DIY ventilation design.

Post by raven » Tue Mar 17, 2020 1:47 pm

Bird on a Fire wrote:
Tue Mar 17, 2020 12:51 pm
I'd expect that the trickiest part might be making something that can be safely lodged down somebody's throat for weeks and sterilised effectively between patients (if necessary), but I'm not any sort of engineer (nor am I even that practical).
I think those bits get thrown away between patients rather than sterilised, and I thought that the valve? connector? whatever it is they were 3D printing in Italy was in short supply because they can only use it for 8 hours at a time even with the same patient.

Some devices create aerosols too* which you definitely want to avoid like the, er *winces*, plague right now, so you'll have to make sure what you're knocking up in the garage doesn't do that or you'll be making things worse for NHS workers.

*Hence a statement from the Royal College of Obstetricians and Gynaecologists statement saying "... the use of Entonox (gas and air) may increase aerosolisation and spread of the virus, so your maternity team will discuss all the options with you in early labour to ensure you are aware of the pain relief options available to you."

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Gentleman Jim
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Re: DIY ventilation design.

Post by Gentleman Jim » Tue Mar 17, 2020 2:30 pm

raven wrote:
Tue Mar 17, 2020 1:47 pm
... the use of Entonox (gas and air)

bl..dy dangerous stuff anyway*

Spoiler:
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Gfamily
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Re: DIY ventilation design.

Post by Gfamily » Tue Mar 17, 2020 2:50 pm

Gentleman Jim wrote:
Tue Mar 17, 2020 2:30 pm
raven wrote:
Tue Mar 17, 2020 1:47 pm
... the use of Entonox (gas and air)

bl..dy dangerous stuff anyway*

Spoiler:
Spoiler:
My avatar was a scientific result that was later found to be 'mistaken' - I rarely claim to be 100% correct

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nekomatic
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Re: DIY ventilation design.

Post by nekomatic » Tue Mar 17, 2020 4:48 pm

For anyone with ideas or resources to contribute, not just on ventilators:

https://twitter.com/jimbethell/status/1 ... 73698?s=21

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Re: DIY ventilation design.

Post by EACLucifer » Tue Mar 17, 2020 6:19 pm

Guardian with quite a bit more detail than the BBC

Realistically, I do not think amateurs are going to accomplish a damn thing except perhaps clogging communications.

Given we knew this was coming, why the f.ck were blueprints sent out now, not months ago? Why are they talking about plans for a basic ventilator now, not paying to have one developed months ago, or better yet, having a plan on the books for whenever it is needed as a long term measure?

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Re: DIY ventilation design.

Post by dyqik » Wed Mar 18, 2020 1:08 am

EACLucifer wrote:
Tue Mar 17, 2020 6:19 pm
Guardian with quite a bit more detail than the BBC

Realistically, I do not think amateurs are going to accomplish a damn thing except perhaps clogging communications.
Unless you have industry standard CAD and CAM software and are familiar with the available production facilities, you're likely just clogging channels. IME of designing stuff for research (and this part likely carries over to any prototype) there are usually bottlenecks in turning designs into manufacturable and assemblable models using appropriate materials, obtaining raw materials and standard parts, and in programming the available production machine tools.

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Re: DIY ventilation design.

Post by raven » Wed Mar 18, 2020 12:15 pm

It occurs to me that DIY masks are probably a lot easier to make than DIY ventilators. Are we asking manufacturers to switch to making masks and gloves and other items for personal protection or do we have enough of those?

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Re: DIY ventilation design.

Post by Pucksoppet » Wed Mar 18, 2020 1:37 pm


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Re: DIY ventilation design.

Post by Pucksoppet » Wed Mar 18, 2020 4:40 pm

There is probably a good reason, but I could not find an answer by a swift Internet-search.

What are the reasons that an Iron Lung couldn't be used for ventilation?

My guess is that they could be simpler to manufacture than a 'down-the-trachea' positive-pressure ventilator, and likely easier to sterilise.

But they might be useless.

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Re: DIY ventilation design.

Post by JQH » Wed Mar 18, 2020 5:37 pm

Iron lungs were used for patients whose chest muscles didn't work due to polio. Their lungs were fine and they breathed ordinary air. In the case of Covid and similar diseases patients lungs are damaged and they need oxygen enriched air.
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