Group Design

Sounds like fun, but why a ventilator? Is the ventilator shortage still happening and are there more urgent shortages? I thought there were already a bunch of ventilator projects.

What is the software going to be like, and is it being taken care of? This sounds like a good opportunity to write some Ada code.

Yeah, that was one of my first observations that there are tons of ventilat or projects. They nearly all are based on squeezing an Ambu-bag to push ai r into the patient. The details of not harming the patient are tricky. Ve ntilating a patient while conscious is harder and very few are doing that. They seem to be having problems with the plumbing at the moment, getting a ll the right valves in the right places to do the right things. At the mom ent there is a lot of hardware right at the patient's mouth. I'm working t o understand what is needed and what isn't.

There's a valve called a Ruben valve which allows the patient to be connect ed to the inspiratory limb (branch from the ventilator) or to the expirator y limb (the path for exhaling) without a leak to the outside via a straight through path. It's not entirely clear just how the details of this valve work. I have concerns that the valve can be stuck in the inhale position b y the pressure in the line. It doesn't seem to have a way to leak out once pressurized.

I'm not sure the software is too hard at the higher levels, but there are i nterface procedures that have to convert differential pressure to flow rate and monitor other marginal sensors. The O2 sensor is only ~18% accurate. The guy running the project doesn't seem to understand the difference betw een accuracy, resolution and noise when we were talking about increasing th e resolution of a reading by averaging many samples. Not that this was a b ig deal. The real issue is I'm not sure improving the resolution of the me asurement will give him what he wants. The airflow measurement is very sen sitive at the low end. I'm wondering if there is an issue with the flow be ing more or less laminar at the low end so that it is not going to be an ac curate reading. The interesting part is they verified the home brew flow rate sensor by using a commercial flow rate sensor that uses the same techn ique.

Whatever. I'm trying to help without being a drag. I think sometimes my q uestions are not what they want to hear. Maybe I'm too pessimistic.

The software is C I believe. I don't think anyone in this crowd is going t o use Ada.

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  Rick C. 

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It sounds like this group is opportunist (I don't mean that in a bad way) - they see a potential market for a device, with a short time frame, and they are trying to get something working as fast as possible before the window closes. So they grab the first off-the-shelf "rapid" development kit they can find - an Arduino - and start banging out code before they've even figured out what they want to do.

For some products, that's fine. For something medical related, it is not. They appear (from your description) to be missing a fundamental understanding of the task, and haven't got in experts to cover that base. And without paperwork covering everything from research, design calculations, specifications (hardware and software), reviews, project management, issue tracking, personnel qualifications, development, testing, certification, production qualification, and a dozen other topics, there is no way they can get any kind of approval.

I would guess that the group is used to small systems for small customers who are happy with a demonstration that shows the device works. That's great for many things, and gives people solutions that work when a serious high-level development process would be orders of magnitude too expensive.

But making things that are relevant to life and death is a different world entirely. Some people think that the current Covid situation is so desperate that /anything/ is better than nothing, so throwing together a cheap and simple ventilator is helpful - that is very far from true.

So I hope you get paid up-front, and keep your distance from the group - be an external consultant, but don't take responsibility for anything other than your reviews.

(And the choice of language for the software is the least of their concerns!)

On 2020-07-08 Rick C wrote in comp.arch.embedded:

That is the good part of designing with a group. You can have many more talents and skills than can be combined in a single person. For a medical product like this you need medical, software, hardware, mechanical and lots more skills. Not something that can be found in one person very often.

This is very worrying. As David already explained, documentation and approval is a very large part of medical device development. There is this famous Boeing quote about the weight of the paperwork required for a plane. I think you can extend this to medical devices as well.

Did they at least have a look at some standards that apply to ventilators to check what will be required? I would start off with IEC 60601-1, IEC 62304 and ISO 80601-2-12, make sure you use the latest versions. But there will be more.

And this should have been done before the first schematic was drawn or line of code was written. Some standards put requirements on the development process and you can not comply with those if you start your certification efforts after the development is completed.

If there has indeed been done nothing on the certification side, my feeling would be to step away as well.

Yes, than all is in your own hands. ;-)

But the advantage of a team is that you can concentrate on what you are good at and let others do what they are good at. And if the team is diverse and skilled enough (and properly led) the end result will be better that that of a single developer.

And I think a lot of medical device stuff can not be done by a single person. There are many cases where you need an (expert) reviewer in the process. Reviewing your own work is less than optimal. ;-)

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Stef    (remove caps, dashes and .invalid from e-mail address to reply by mail) 

It seems that more and more mathematicians are using a new, high level 
language named "research student".

Pay??? This is open source, volunteer labor. They have a few companies donating fabrication services. A sheet metal shop fabricated a few chassis. I think they may even have a Chinese assembly house donating some board assembly work.

I started on a different project which was doing a very similar thing and I questioned the need for yet another project. In the end the guy leading that effort bailed and the group decided to merge with this project that was further along.

I think I feel awkward because I don't have a defined roll. It is hard for me to tell if/when my comments are welcome and when they are kibitzing.

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a ventilator and it is a unique experience. We have people of many skill l evels and talents, many I don't even know.

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any sort of approval process. No one working on the project even seems to understand what is required.

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step away, but the person acting as a leader seems to want me in the group.

get to rev 2 of the board and then step out.

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It seems the UK has an abbreviated set of requirements for response to COVI D-19 and that is what they are mostly working with. I forget the name of i t.

They do get advice from time to time from professionals in the field. My m ain concern is a direction they are currently going in where more and more valves, pressure relief, etc. is being added to the tubing right at the pat ient. I'm not sure how it all will be held in place. That and how they pl an to get this through the approval process.

I had a friend who worked on medical devices for a while before getting out . He said they required that you "prove" your design will not hurt the pat ient in any way. Hard to do with a ventilator.

I don't mind working on the team. It's seeing them go in odd directions th at bugs me. This thing will probably cost hundreds of dollars in the final BOM without anything like profit or overhead added in. People were arguin g against adding $0.10 for more pins on a processor. Then later they decid ed to not only go with the larger pin count, but bump from an 8 bit AVR to an ARM CM4F adding several dollars. That sort of inconsistency drives me n uts. "Every dollar counts!" Yes it does, so you need to justify the cost

*rationally*.

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  Rick C. 

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[...] [Is there a way you could limit your line length to a more usenet friendly number?]

How long will this last? If you look at the new cases curves, the UK is well over the initial peak.

has nice graphs of world cases on the front page.

Sounds like they are moving to more and more features instead of sticking to a simple emergency use device. Feature creep is not uncommon when getting advise from several medical professionals. ;-)

That is not entirely true, it is more a risk/benefit analysis. Otherwise you could not even get a scalpel approved, it will always hurt the patient.

Does every dollar count in this case? If this is for solving short term ventilator shortages, should development speed not count more than dollars?

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Stef    (remove caps, dashes and .invalid from e-mail address to reply by mail) 

A national debt, if it is not excessive, will be to us a national blessing. 
		-- Alexander Hamilton

I think the UK competition is over:

Demand from the rest of the world is a different, unclear, question...

Theo

of a ventilator and it is a unique experience. We have people of many skil l levels and talents, many I don't even know.

y

Not without copying messages to some other editor and then pasting back int o Google groups. I know there is a spec for this, but I've switched newsre aders several times over the years and I'm just tired of trying to find too ls that last the test of time. So I've settled for ease of use over strict adherence to the spec.

Why is your newsreader intolerant of longer line length?

COVID-19 and that is what they are mostly working with. I forget the name of it.

ell

As was the case for much of the US... until they started to open things up again. My crystal ball is not working so well these days. Seems it needs a lubricant that is also used in making protective gear and is in short sup ply.

My main concern is a direction they are currently going in where more and m ore valves, pressure relief, etc. is being added to the tubing right at the patient. I'm not sure how it all will be held in place. That and how the y plan to get this through the approval process.

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Don't know about "more and more" or "feature creep". They are responding t o the issue that virtually every other piece of gear is doing the same limi ted job of ventilating an unconscious patient because it is easier. Kenned y promoted the space race to the moon "not because it is easy, but because it is hard". So why not take on the harder task of being not just more use ful, but safer. I don't recall all the terms, but when the patient is only assisted in breathing there is less risk of harm from use of the machine. So this is not just a less often implemented feature, it is an important f eature.

In particular, it was in a conversation with a medical professional that th is need was pointed out.

out. He said they required that you "prove" your design will not hurt the patient in any way. Hard to do with a ventilator.

you

That is a bogus comparison. So nothing to discuss there.

s that bugs me. This thing will probably cost hundreds of dollars in the f inal BOM without anything like profit or overhead added in. People were ar guing against adding $0.10 for more pins on a processor. Then later they d ecided to not only go with the larger pin count, but bump from an 8 bit AVR to an ARM CM4F adding several dollars. That sort of inconsistency drives me nuts. "Every dollar counts!" Yes it does, so you need to justify the c ost *rationally*.

s?

It's not about rushing to the finish line for sure. None of the goals are clearly stated. That's my point.

We meet using video tools and Zoom seems to work the best. I have various latency and bandwidth issues and was not able to participate yesterday. Th at's really frustrating, especially when everyone is missing an important p oint. Today we had a one on one to test Google Meet and compare to Zoom (G oogle was a second runner). So I had a chance to make clear what is and is not a problem in the plumbing. Understanding what I was saying he agreed so the plumbing next to the patient is less cumbersome now.

Maybe more 1 on 1s will help.

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  Rick C. 

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There are different levels of approval for medical devices in the US. The lowest level would be for something like crutches, which can't really hurt the patient unless you do something really dumb, so you basically prove that you followed established practices instead of doing something dumb. More invasive devices like pacemakers or ventilators need much more intense testing and approval. One thing I remember being told was that you have to document the design and development (including the software) every step of the way. There was a guy here on c.a.e. some years ago who did that stuff and I learned some things from him. It is one of the reasons I got interested in Ada.

Slrn may be a bit ancient, but so is usenet. ;-) Slrn can handle long lines, but after quoting it does not wrap them anymore, so I need to shift the screen to view the entire line. Luckily the editor for replying does still wrap those. But hey, it's a minor inconvenience, just asking.

So the aim is to create a new type of ventilator, not to cope with immediate shortages? This is very big task indeed. This sort of thing usually takes years of development and and clinical testing. They have certainly gone for "not easy, but hard".

I don't agree. ;-) The scalpel example is a bit extreme of course. But for every medical device there wil be a risk/benefit analysis. There are medical devices that do some harm to a patient, but as long as the benefits outweigh the harm it may still be a good thing to use those devices.

A ventilator is never good for your lungs, so it will do some damage, the aim is to keep the damage as minimal as possible and as short term as possible.

Well, get that point across and try to get the goals clear before proceeding.

Good luck.

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Stef    (remove caps, dashes and .invalid from e-mail address to reply by mail) 

root rot

gn of a ventilator and it is a unique experience. We have people of many s kill levels and talents, many I don't even know.

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into Google groups. I know there is a spec for this, but I've switched ne wsreaders several times over the years and I'm just tired of trying to find tools that last the test of time. So I've settled for ease of use over st rict adherence to the spec.

re,

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I wish Google was amenable to requests regarding their software. As far as I can tell they ignore any feedback and happily ignore rules for newsgroup s as if they invented them. I think it was Al Gore who invented the Intern et, no? So we can blame him perhaps for giving Google a license to drive o n the cyber-highway.

Thanks for understanding.

to COVID-19 and that is what they are mostly working with. I forget the na me of it.

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up again. My crystal ball is not working so well these days. Seems it ne eds a lubricant that is also used in making protective gear and is in short supply.

. My main concern is a direction they are currently going in where more an d more valves, pressure relief, etc. is being added to the tubing right at the patient. I'm not sure how it all will be held in place. That and how they plan to get this through the approval process.

ing to a

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ng to the issue that virtually every other piece of gear is doing the same limited job of ventilating an unconscious patient because it is easier. Ke nnedy promoted the space race to the moon "not because it is easy, but beca use it is hard". So why not take on the harder task of being not just more useful, but safer. I don't recall all the terms, but when the patient is only assisted in breathing there is less risk of harm from use of the machi ne. So this is not just a less often implemented feature, it is an importa nt feature.

t this need was pointed out.

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I would not say "a new type". This is what commercial vents do. But being the hard part, most of the quick turn projects leave it out. I expect it will be the hardest to get approvals for too.

ing out. He said they required that you "prove" your design will not hurt the patient in any way. Hard to do with a ventilator.

se you

.

The trade off issues for a ventilator are well known, not something to be n egotiated. So there is no point in comparing to scalpels. The rules are t he rules and it will be hard to get approvals. I'm sure it costs lots of m oney, not unlike FCC approval. I believe the plan is to find a manufacturi ng partner to turn this design over to who will bear the brunt of approvals .

This is not impossible, but I think that should be one of the early steps s o they have some input to the process, guiding what comes out at the end ra ther than simply having to redesign it all over again potentially.

ions that bugs me. This thing will probably cost hundreds of dollars in th e final BOM without anything like profit or overhead added in. People were arguing against adding $0.10 for more pins on a processor. Then later the y decided to not only go with the larger pin count, but bump from an 8 bit AVR to an ARM CM4F adding several dollars. That sort of inconsistency driv es me nuts. "Every dollar counts!" Yes it does, so you need to justify th e cost *rationally*.

m

lars?

are clearly stated. That's my point.

I have provided my input and the project moves forward. The rev 1 of the m ain board is full of issues mostly because the guy doing it is donating his time while continuing to work full time. There was no design review I ass ume because there was no one to conduct it with but also I think because no one recognizes the need. "It's just an Arduino" plus some interfacing cir cuitry.

The design includes window comparators for alarm settings. I found that ac cording to the labels and the polarity of the outputs the alarms will be gu aranteed to be on all the time. Fortunately the prototype uses pots for th e set points so the max can be set to the min value and vice versa.

I'm also concerned about the board layout. The board is not at all dense b ut there are several parts that need copper area for heat sinking. They ar e using a linear regulator to drop 12+ volts to 5V and 3.3V. The back ligh

C!!! There is a motor controller that has to handle several amps of curren t. Both of these parts had thermal breaks on the thermal pads on the rev 1 board. So virtually no heat sinking.

ous latency and bandwidth issues and was not able to participate yesterday. That's really frustrating, especially when everyone is missing an importa nt point. Today we had a one on one to test Google Meet and compare to Zoo m (Google was a second runner). So I had a chance to make clear what is an d is not a problem in the plumbing. Understanding what I was saying he agr eed so the plumbing next to the patient is less cumbersome now.

Thanks.

No small part of the problem is I don't have a defined roll. Someone is do ing the electronic design part time and I get to figure out what is wrong o nce in a while. Not enjoyable really.

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  Rick C. 

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Frankly this project sounds like amateur hour. If US FDA approval works the way it's been explained to me, there is no chance of the device ever getting it. Other countries' mileage may vary.

There are other devices that they could build that would be much less dangerous (therefore easier to get approval for), but that fill a need. For example, polysomnography machines for sleep studies, or other diagnostic equipment. Compared to a vent, they are pretty safe, since they only measure your body functions (heart and breathing rate, etc.) rather than being an invasive intervention. But having more of them available could help people with underdiagnosed conditions like sleep apnea.

IANAL, but the liability implications of that would be interfering with my sleep.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

I have worked on the side-lines of a few medical-related devices. The requirements and approval process is hard. On a board I worked with, the prime function - the top priority function that must not fail - was to turn off all outputs and make sure it did not interfere with manual use of the system when auto mode was not enabled. Running the motor was a secondary function that could be done if enabled and all is well, but having everything off was still classified as "working correctly". It's a weird way to think about things.

That all sounds frustrating. For sale to the US, you'll need to satisfy some specific FDA requirements and be prepared to prove it, including dotting Is/crossing Ts in just the right way. You have an international crew so you'll probably have to satisfy certain other international requirements. I'd float the idea of getting an FDA expert on your team as soon as possible. You'll need that kind of talent, otherwise your efforts will be wasted.

JJS

I guess you don't sleep well very often. There will be no liability issues . This group is not going to produce the machines. They will hand the des ign off to a manufacturer who will produce, market and obtain approvals for the machine. Liability will be all theirs.

Most likely the machine will be totally redesigned anyway for cost reductio n and to obtain approvals. As a group this is not a highly knowledgeable d esign group. I can't imagine this design will fly without rework.

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  Rick C. 

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It's a medical device, so I think you mean cost enlargement rather than reduction ;-). But, if the design group doesn't know what it's doing and is producing something that can't be used, then why are they bothering in the first place? What do they hope to contribute, and what do they hope to gain?

That doesn't make sense on so many levels that it isn't even worth refuting it!