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Hi team, I'm an anaesthetist (in America you'd call me anesthesiologist) and a bit of a geek. Not a ventilator expert but I have a few thousand hours as a user. I love the simplicity and robustness of your design. I've been thinking about this challenge for about a week, and I've had many thoughts! So I wrote a document <https://docs.google.com/document/d/1sdrKYQ0mDOu4bJum6Fx6piRutIJovo7UqFKYHHxUD5A/edit?usp=sharing> which lays out what I believe engineers need to know about moder ICU ventilators capable them of treating COVID19 ARDS patients and getting them weaned. I really think what you have done is a very clever potential core of a high spec rapidly deployable ventilator. The the final features will be critical. I'm hoping to foster cross team cooperation and sharing, to this end I've tried to break down the overall project into a series of components and I've started to lay them out here <https://docs.google.com/document/d/1SBT8auegsJCKCVMBHFLWaVo8rKbs0zsJc3dDVAqeADE/edit?usp=sharing>. I'm hoping this document can evolve into a bit of component level index page pointing off to different resources. Hope these documents help your team, and I'd love your feedback. And happy to take questions (ideally as comments on these documents) best wishes Erich Erich Schulz, mbbs, mba, fanzca 0410 277 408

Despite the fact that CSSALT Ventilator uses an external positive pressure source I believe that there may be a point in having alternatives for a mechanic device to drive a bag squeezer, piston and etc. Following is a POC using our Controller for supporting that: https://youtu.be/u2GeKEEkZSk MV

All: Farhan has added code for what's called a Watchdog Timer (WDT). These timers are often added to mission-critical applications where, if events don't happen (like breathing!), a WDT can be used in an attempt to "fix things". I've attached a short PDF that explains what a WDT is and how they work. For anyone reading Farhan's code, it may help follow what his code is doing, too. Jack, W8TEE

OK all of you very bright people out there -- the team needs some more help. We need to know if we have RESPIPRATORY SENSITIZERS in the airway, and there are two main concerns on my mind -- 1. Is there LATEX in the diaphragm of the Rainbird or Orbit lawn sprinklers? [Latex is a bad word in hospitals, so many people are sensitive to it. And I don't even know exactly what it is....] 2. What is the BODY of the Rainbird and Orbit made out of? What is the type of plastic? If you can find the material safety data sheet, that is extra Brownie Points!! If anyone can figure out either or both of these, it will definiltely help our speeding our FDA Emergency Use Authorization submission! Some of you folks are REALLY BRIGHT and can probably figger this out for us lickety-split! THANKS--- Gordon Gibby MD KX4Z

I Need some help here, folks. Marcelo has pointed to a important isssue that the BMP280 might not return an answer and the program would then hang...... I have searched for a solution and this fellow seems to have a replacement Wire.h that may offer a solution: https://github.com/IanSC/Arduino-Wire.h Can others take a look at this and tell me if this is suitable and solves marcelo's concern? THANKS! Gordon.

Here is a link to most of my design work on air flow and pressure sensors (element selection criteria, flow meter design, and Arduino code to use them usefully). https://github.com/DRWJSCHMIDT/OSVentFLow I’ve been asked to do the same for an open design ventilator group in Europe. I’ll still stay in the group and still help out as requested. Dr. William J. Schmidt, Ph.D. Managing Partner & Chief Consultant Mountain Ridge Engineering, LLC 27472 Myrtle Lake Lane Katy, TX 77494 618-973-9438 Personal email: bill@... The information in this electronic message is confidential and is intended only for the use of the individual(s) and/or entity (entities) named above. If you are not the intended recipient or its authorized representative, you are on notice that any unauthorized use, disclosure, copying, distribution, or taking of any action in reliance on the contents of the electronically transmitted materials is prohibited. Please delete this message from your system permanently. Virus-free. www.avg.com

Topic about the Open Ventilator SW design Here the first "Dev Talks" video: https://youtu.be/YwuAGQwNAeo Have fun, MV

Folks, the effort has paid off. The lawyers at UF, once properly appraised of the NUMBER of volunteers working on this, have an extremely strong liability and legal defense coverage for any volunteers who are ACKNOWLEDGED FORMALLY AS VOLUNTEERS. The University of Florida is not a manufacturing facility; we are a healthcare medical school (Plus liberal arts, etc) -- and your expertise, incorporated into a ventilator, should it be used on patients at our hospital -- you will not onlly have coverage, you would have legal defense, and yoiu cannot even be sued individually THIS is the coveraaage that I *always* had as a physician working for them for 30 years, that ALL their employees have, and that now YOU will enjoy. If you are on the attached list of formal volunteers. ATTENTION SQUAGLE: We cannot provide coverage for you without your NAME and where you live. So please provide that or we can't provide coverage for you -- it is your choice, we can't FORCE you to identify yourself of course. ATTENTION THOSE REQUIRING INDEMNIFICATION: The University of Florida is prevented by law from providing you with Indemnification. So that will not happen for you. Just letting you know the message from the lawyer. The protection for acknowledged volunteers is EXTREMELY STRONG in my opinion --- it has many layers that are almost impenetrable. I never worried in my career when covered by that protection. NOW -- for the REST OF THE WORLD: There are carefully worded disclaimers on the University of florida CSSALT page on this design that explain to potential builders, manufacturers etc outside of University of Florida --- you are welcome to use the information; you have no warantee, no coverage, NOTHING from UF. And of course that is as it should be. IF we are successful (with the hellp of all these volunteers about to be acknolwedged, hopefully before NOON EDT today) at getting an FDA EUA -- *then* other manufacturers will likely have a TON EASIER TIME getting one for THEIR project as well. This is a very positive outcome, and I appreciate greatly Dan D'Alesio (UF Lawyer) who immediately recognized the concern and immediaately found ways to cover these volunters -- and also many of you who have proivately or publicly given me crucial advice to search for this coverage. So I expect to be fully operational again for UF within a couple of hours. See the attached document filed with Dr. Gravenstein of UF last night for the list of volunteers about to be acknowledged.

Very clever, but too simple? https://www.youtube.com/watch?v=JGRlC52Td7w -- Art Greenberg art@...

Daughter with two young ones passed this on to me from her mother's group. https://www.facebook.com/BreastPumpVent/ Bob Benedict KD8CGH

My wife sent me this. Excellent technical reading on a theory of how COVID-19 may cause mortality and how it may be tested for and prevented: https://drive.google.com/file/d/1KECWGIHYxPHCAIweX0JPeTm0aK6JcQXg/view Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com Like us on Facebook! Moderator – North American QRO Group at Groups.IO. email: bill@... Virus-free. www.avg.com

Gordon: Can you post a link to the UF professor's design for a N99 mask that uses a fabric normally used to protect surgical instruments and can be autoclaved? James

Ok I finished writing the code for the Flow calculations… both average flow rate and total volume for exhale and inhale cycle. NOW I NEED SOMEONE TO TEST IT. ANYONE? I got stuck in the Caribbean (J6, at our resort) after the ARRL DX SSB contest a few weeks back and I can’t get back to the USA so I don’t have access to Arduinos and hardware to test this out… If someone could test out this code it would be helpful. I’m really a crummy code writer so don’t expect much. Anyone able to test it our say so and I’ll walk you through how to test it. Ideally Gordon could do it but AFTER it gets integrated into the program. All of this ode could get integrated as a small subroutine. The whole thing is 943 bytes long. I’m sure I’ve got some broken types that need to be fixed. Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: www.VillaGrandPiton.com Like us on Facebook! Moderator – North American QRO Group at Groups.IO. email: bill@... Virus-free. www.avg.com

Marcello, Jack, and all other programmers. Time for you to be writing subroutines to deal with the available data from the BMP280/BME280, to create DISCONNECT and HIGH PRESSURE alarms. The specifications for alarms is here in the British standard: REFERENCE: See https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/876167/RMVS001_v3.1.pdf This document is also attached. 1. Must alarm at: a. Gas or electricity supply failure. b. Machine switched off while in mandatory ventilation mode. c. Inspiratory airway pressure exceeded. d. Inspiratory and PEEP pressure not achieved (equivalent to disconnection alarm). e. Tidal volume not achieved or exceeded Item (d) is the disconnect alarm in their standards --- so You have to be able to detect the inspiratory pressure and note that it has not been achieved. This is VERY VAGUE. I would suggest that you plan to alarm when the inspiratory pressure falls out of what "has been seen" by some amount -- say, it falls by 20% or so That means you probably have to measure ambient pressure to know what "0" is when the ventilator is turned on -- and have the user know to let it calibrate. Then you observe what the inspiratory pressure achieved is...and notify the user when you have selected what you think is normal -- you can smooth over some time perhaps -- print a note to them that you are automatically setting an alarm at XXX pressure. Then if there are two breaths sequentallly that fail to achieve your requirement, you initiate some sort of alarm sequence -- and provide a button that allows them to cancel the alarm (alarms drive you nuts while you are actually FIXING the issue). You can for example just instruct them which button to press to stop the alarm. I hope this is enough to get you going on that part of the design. Gordon Gibby KX4Z

I have done a second test with another PC PS found in my company's junkbox (older, not ATX) and results are consistent with the ATX one: 11.9 --> 11.6V. I have done no scope tests like ripple level, effects on the 5V line, etc. If these tests are needed I'll do them. Raf

All: I'm trying to compile Ashar's code and it has a line in it: #include <BMP180I2C.h> which is the BMP180 library for the I2C interface and I cannot find it anywhere. Does anyone have a URL where I can download this library? Adafruit says they have it, but I cannot find it. Also, and I've argued for this here and elsewhere, any time you use a non-standard library--that is, any library that is not distributed with the Arduino IDE--you need to have a comment on its include line that tells the rest of us where you got it. #include <BMP180I2C.h> // Dowload at: http...???? That way, we don't have to waste time trying find where to get the library. Jack, W8TEE