Problem with vent bag is that you cannot maintain a positive expiratory pressure (around 10mmHg of pressure during the expiration to prevent lung to collapse alveoli). For Covid-19, all the projects based on mechanized vent bag where useless because of the type of disease.
There are several companies behind the project. The company who makes the electronics is Tronico (https://www.tronico-alcen.com/en/markets/medical). It has all the medical certifications needed.
We are currently going on with ANSM certification (equivalent of US FDA). It is a long 2 years way, with lots of papers and tests... If it is approved, sure it can save life everywhere in the world. If it is not, it was a project where we learned a lot.
By the way, ambulance ventilators are harder to develop and to approve. Hardware must resist huge shocks and accelerations.
> If it is approved, sure it can save life everywhere in the world.
It's worth noting that mostly regulatory approval is jurisdiction specific, so the device will need to be separately approved by a bunch of different bodies. ANSM is the french local body, but it is EU MDR you probably have to meet; this at least gets you the EU countries but for example will allow your device to be used in the USA, you would still need FDA there. Some jurisdictions, particularly smaller ones, will rubber stamp things if you have the right approvals but it's still finicky and of course with a physical device you have to deal with things like different power standards.
The approaches are similar but annoyingly different enough that this isn't easy. Luckily they are both reliant on ISO13485 at core, so there is overlap. It's not just paperwork either, you can definitely design something that will not pass in another jurisdiction if you aren't careful (e.g. due to materials used). Further, you need separate certification to a standard as both a manufacturer and developer, and these don't carry over automatically either.
People are working on making this easier to do worldwide, but it still isn't easy. For example you can use MDSAP to get a regulatory audit that meets multiple countries requirements at once.
How big portion of these approvals is to have right people to get paid and to actually make sure the product is safe? We're the any "blunders" like with Boeing?
As far as I understood doctors, in march there was no guidelines for the disease. It was considered as a respiratory disease.
Later on, it was requalified as a vascular disease, scientists looked at cytokines / interleukin (I AM A ELECTRONIC ENGINEER, please correct me doctors).
Short answer is no, I don't trust Rpi for vital tasks.
Long answer :
In this project, Raspberry is used to display curves and set some parameters. The core (ventilator algorithm) is implemented on the STM32F411, there is just a serial link in-between.
The STM32 also monitor the Raspberry... If there is no heartbeat on the serial link, the STM32 shuts down the power supply of the raspberry, and ventilation goes on.
The fact is that it never happens yet during our tests (4 months uptime now for some devices). The ArchLinux is restricted to the bare minimum, and the Rust app do not overheat the CPU. Is it by chance, or not ? Before any MTBF conclusion, you need thousands of units running during months...
On another project of medical datalogger, I also put a little arduino as hardware watchdog. If no heartbeat of the main application, it just resets the Rpi.
I assume when you refer to 'serial link' you mean that you are using Rpi UART interface to communicate with the STM32.
I can see the convenience of using UART but as a very cautionary advice, hospital environments are electrically quite harsh in terms of EM noise. A serial line even a short one can absolutely suffer from interference.
You already made it relatively fail-safe with the heartbeat/watchdog but please consider upgrading your design to use comms with a differential signal, anything like CAN or even RS-485 in that Rpi/STM32 link would be a significant improvement.
I'll be very happy for my industrial projects if BCM2711 come with CAN or RS485 built-in, but for the moment, there is nothing planned by Raspberry...
A low speed 115200 baud link does the job, with applicative CRC on both side to be sure there is no corruption.
My method to test communication robustness: I inject pulses through a capacitor directly on the UART lines. I did it on this project, no problem. The four bytes CRC32 prevents random EM noise errors.
I think the problem OP is referring to is that if you were proposing this design for a approved medical device for use in say US & EU, you might have trouble passing e.g. 60601 because of the communication channel. I haven't looked over the design in detail but EMI etc. can be quite tricky to manage in this sort of device.
Yes we are :)
The first days were fun. Then the french government pushed the project. Challenging, crazy, but exhausting. 25 days without coming back home!
Then the lockdown did the job, and the project was not so urgent, so the ANSM (french equivalent of US FDA) was not so in a hurry. And now it seems to take ages for us between two administrative steps, but it is still fast for ANSM. Development of a ventilator take normally a few years!
Good stuff! Device projects typically take a while. Industry average for a device like this is something like 3-5 years start to finish, so you are right it's pretty quick (although other ventilator efforts have been similarly fast - it's almost like there was extraordinary motivation).
I've seen 18 months before, but that was primarily software. I think the FDA clock on evaluation is 120 days now, that's after all the i's are dotted and t's crossed. EU MDD/MDR is similar, iirc.
This is good systems design. I've made a system with a similar design (RPI for display and UI, one STM32 for hardware control, another as watchdog) for an industrial marking system, and it's run almost daily for 3 years without any issues.
The great thing about the Pi in this case is that it's non-critical, and if it ever does die, you spend $35 and put in a new SD card.
As soon as ANSM (french equivalent of US FDA) hears "linux", "wifi", "connected", they see a scary green monster...
And to be honnest, I understand their point. How can you certify Linux ? So much code behind... It is not a car multimedia center, it is a ventilator, a class III vital device.
In this project, what was really impressive is the gap between the bare minimum (a 4 lines lcd screen + a few buttons + a pressure sensor, and you can make people breath), and the doctors expectations (curves, flow meters, statistics, O2 sensors...).
This is the same for lots of activity: experts cannot work with basic tools anymore. Only High level experts still can.
Conclusion: do not work with high level experts to build your specifications. Also listen to normal experts and doctors that needs more UX assistance.
Do you think relying on something like a hospital-provided tablet would have worked? Was this considered?
I mean, having that many screens may be a bit redundant, if you can have a single high-quality one. That said, I understand it introduces some complexity due to wireless protocols, paring with the right ventilator, etc.
In our initial requirement list, it was designed to be used in temporary hospitals (any public hall for example).
Screen convergence is not for now in hospitals. Behind one sensor, there is one company that sells its monitor with the sensor. Some old well known sensors now converge to one monitor (philips, edwards life science...), but there is a still one screen for every other functions.
Gathering data (when the constructor made it available) is a mess... look at HL7 specs! To build a medical datalogger, you sometimes must interface to an analog output (it is part of my job).
Why use the Rpi at all (Nothing against them, I have a few)?
If the Pi is just writing graphics to a screen, why not handle that directly with the STM32? Running an RTOS, it should be able to manage a low priority GUI task along with the real-time ventilator tasks.
If you're in the middle of a world crisis, and you need a small computer + touch screen, Rpi is THE solution. Farnell and radiospares have tons of stocks.
We planned to develop a small gateway to gather all the devices alarms, linked to bed number. It was not developed, but hardware has the feature.
The LoRa fairness will allow very few data to come up, but high level alarms vital could be transmitted several times in a second if needed.
We know we cannot use it to transfer waveforms of course.