jcl5m1 / ventilator

Low-Cost Open Source Ventilator or PAPR

Last updated 2020/04/19

Low-Cost Open-Source Ventilator-ish Device or PAPR

NOTE: This is currently an independent project not affiliated with any commercial institution.

• In the event that COVID-19 hospitalizations exhaust the availability of FDA approved ventilators. This project documents the process of converting a low-cost CPAP (Continuous Positive Airway Pressure) blower into a rudimentary non-invasive pressure support ventilator that could help with breathing during respiratory distress. It's an evolving project, but in it's current form, it most aligned with the definition of a non-invasive pressure support BiPAP ventilator.
• This same project can also be used to create a reasonable low-cost Powered Air Purifying Respirator (PAPR) with filter adapter and mask. PAPRs are effective pieces of Personal Protective Equipment (PPE) that could be helpful to caregivers. PAPRs will also be in extremely short supply and are much less risky and controversial than a DIY ventilator. You may be able to save many more lives by building a PAPR that protects a caregiver than a mediocre ventilator for one patient. Unless you are able to participate in the detailed engineering and medical discussions regarding mitigating the risks of high pressure ventilation, I would highly recommend focusing on the PAPR version of this build.

WARNING/DISCLAIMER: Whenever possible, please seek professional medical care with proper equipment setup by trained individuals. Do not use random information you found on the internet. I am not a medical professional, just a random person putting information on the internet. There are significant risks associated with using a high pressure BiPAP as a DIY ventilator without medical supervision.

What are the primary risks of a DIY ventilator?

• Being viewed as a viable alternative to available professional care or delaying seeking professional care. This should be viewed as an educational resource or a last resort option only. Community driven engineering efforts like this run the risk of making it "too easy to be harmful" which would be a bad outcome.
• Using non-invasive interfaces (such as masks and mouth pieces) can create aerosolized virus infecting many others in clean environments. Infecing yourself or other healthy individuals multiplies the problem. Usage should be restricted to places where aerosolized viruses are already abundant (lots of unmasked symptomatic individuals), COVID wards, or in isolation. NOTE: Self-quarantine in an apartment or multi-unit residence is NOT proper isolation due to potential shared ventilation and sewage.
• Giving too high a pressure (such as 20cmh2o and up) without observing lung compliance can cause rupture of infected lung tissue. This design currently lacks several features that provide enough feedback to a caregiver to monitor that risk.
• See more detailed discussion of these risks and potential engineering/administrative controls to address them.

Too risky? Build a low-cost PAPR!

One more time, a low-cost Powered Air Purifying Respirator (PAPR) is highly valuable for caregivers, and may have much more positive impact than bulding a mediocre ventilator.

Want to build something without electronics? Consider building PPE

• There are many efforts making DIY face shields
• There are many efforts making face masks from home materials. We've also posted some of our results of testing filter performance of different materials.

Hardware Requirements and Medical/Government Request for proposals:

• Requirements doc from Code Life Ventilator Challenge - Montreal General Hospital Foundation (Canada)

• Requirements from Gov.UK - Rapidly Manufactured Ventilator System (UK)

Current Hardware Capabilities

• This rudimentary design can have a programmable breathing rate (ex: 10-16/min)
• It can have a programmed Positive End-Expiratory Pressure (PEEP)
• The blower is physicially able to hit a peak airway pressure of up to 45cmh2o. However, going above 20cmh2o can be DANGEROUS.
• It cannot yet hit a target tidal volume. What level of accuracy in volume would be sufficient? 100mL? 10mL?
• It does not regulate fractional oxygen (FiO2). But, a down stream connection to an O2 tank is possible to boost O2 concentration with manual flow adjustment. I could use a pointer to a low cost O2 sensor.
• It is lacking in many other ways, but it is possible that this limited functionality could be helpful when better care is not available. It is also a starting point for making progress. Critical features can be added over time.

Here's a youtube video walking through the components as of 2020/03/17:

There are also many other efforts in this direction. Here's a short list of them Thanks! discussion

To Do's - aka Things I could use help with

I've moved the To Do's to a Wiki so it is easier to update. Please check there if you are interested in helping. Thanks to those that already have!

To provide comments/feedback/offer help, create a new issue on the project. Thanks!

Useful References/Docs about the supply shortages, and guidance around unapproved devices:

There is a growing list of useful documents around guidance for use of unapproved equipment, and information around estimated shortages of both ventilators and personal protective equipment. We have moved them to References Wiki to enable better updates to make it easier to maintain.

Materials

1. Continuous Positive Airway Pressure (CPAP) devices are commonly used by individuals to treat sleep apnea. As a result, CPAP blower components are fairly abundant. Used ones are available on eBay and new ones on Alibaba. In many of these devices, the blower is a simple BLDC motor that can be driven with an Electronics Speed Controller (ESC) used by quadrotors and RC cars. The one I used is pulled from a Respironics REMStar. In volume, these blower components can be under $20.

• Alternative: test a 12v inflator pump which is even more abundant.
• Alternative: print a blower [discussion]

2. Arduino Compatible Nano/Clone to control the motor speed, breathing cycles, and handle user input. Download the Arduino IDE to program the microcontroller software.

3. Brushless DC Motor Electronic Speed Controller capable of at least 10A.

4. Button or switch for input control. The code cycles through 5 levels of pressure. Double click to switch between CPAP and BiPAP/Fixed PEEP mode.

5. 12v DC power supply that can handle at least 5A. The blower works pretty hard, and the breathing cycles can create voltage drops which will reset the Arduino if the supply is not strong enough.

6. Tubing and face mask. If you search for CPAP face mask, you'll find many options/suppliers. A full face mask that covers both the mouth and nose will enable pressure buildup in the lungs. As an alternative, see below for draft 3D printable parts.

7. Optional inline 12v battery backup.

Building

This is the full system with mask, tubing, pump, 12v battery, and switch for input. However, I would strongly recommend running this with a DC power supply since the battery will only last about 3-4 hours. Wearing the mask with a dead battery could cause dangerous CO2 build up. This particular battery can charge and supply power at the same time, acting as an inline battery backup to wall power.

Below is a close up of the extracted blower. It is simply a BLDC motor driving a blower fan. A small ESC and Arduino are attached (technically a Teensy2.0++, but the code has now been changed to an Arduino Nano). It has a 3d printed tapered hose adpater on it to fit in the hose. The microcontroller software can be programmed with the Arduino IDE. The software goes through a short initialization sequence to configure the ESC; it then starts at the lowest CPAP setting. You can use the switch to cycle through pressure levels, and double click to cycle through operating modes.

Here is the schematic for the electronics. As you can see, it is very simple with only a few parts. A slightly modifed version that is able to sense the blower current is here.

Face mask / Tube Adapter

Since I have a CPAP, I happen to have a Resmed AitFit F20 mask that I can use. This is quite comfortable and covers both the nose and mouth to make a good seal. However, if you can't get a mask, below is a prototype mouthguard that fits in the category of not-so-great-but-usable-if-you-have-a-lot-of-tape. I am using some elastic straps as head gear. However, in order to get a good air seal to get enough positive pressure, this would require some tape. A little bit of leakage is actually desirable to allow CO2 to escape near the mouth and nose to flush out the air over time; this prevents CO2 from being stuck in the tube. WARNING: wearing this sealed to the mouth with tape without power may cause dangerous CO2 build up.

Download the [3D model] [Fusion 360 link].

Pressure Testing

This is a picture of my test rig to measure the output pressure. It is a U-shaped tube with an attached measuring tape to check displacement of water. The actual liquid displacement is 2x the measured line since liquid is being pushed downwards an equal amount on the other side of the U, doubling the displacement. (I think this is the correct way to measure). At full blast at 12v, it is achieving 45cmh2o. WARNING: Going above 20cmh2o can be DANGEROUS. So, these blowers are plently powerful.

Here are some images showing the dislacement of the liquid at different speeds. I happen to have Diet Dr. Pepper on hand which makes it easier to see the liquid level rather than just plain water.

Here's a video of the blower pushing a breathing cycle of 16 cycles/min oscilating between 12 and 22cmh2o.

Air Filtration - PAPR Option

An open air blower into someone's airway isn't great. If possible, some filtration is preferred. These parts were originally used for a DIY Powered Air Purifying Respriator (PAPR). However, adding a filter will definitely affect the output pressure. It will depend on the blower you have if the motor can handle the additional load. Given the headroom of the blower I tested, these CPAP blowers can probably handle the filter and still hit the target pressure. However, I haven't done long term thermal testing at high pressure and with a strong filter. These adapter plates can be attached with liberal amounts of hot glue and wrapping the unit in vinyl tape to get a reasonably airtight seal. My blower's enclosure was not air-tight, so it is difficult to guarantee that 100% of the air is coming only through the filter. Setting the blower to a low CPAP pressure, and leaving the face mask vent holes open will allow it to function reasonably as a PAPR.

• This is an adapter plate for a 3M P100 or N95 face mask filter cartridge. Download [3D model] [Fusion 360 link]

• This is an adapter plate for a NATO 40mm gas mask filter cartridge. These fitlers are available with CBRN ratings which are needed for viral and bacterial defense similar to those approved by the CDC/NIOSH. Download [3D model] [Fusion 360 link]

• This is an option for an inline filter [discussion] that looks easy to install, and would be helpful for non-CPAP blowers.

Update Log

Click here to see updates.

ventilator's Issues

Professional Insight?

So I hit up a friend with connections to people who actually make ventilators and these are some areas of concern they brought up.

• "This seems like a very very dangerous endeavor"
• Inflating patient’s lungs correctly (including being in sync with their respiratory drive)
• Weaning the patient off support later is a super complex thing with no room for error.
  Though I believe this really only becomes an issue after ~24 - 72 hrs of use, (Needs confirmation)
• They also pointed out that this wouldn't be a true ventilator as you usually sedate and intubate patients in that case.
• They were also concerned with the potential for the positive pressure gas exiting the patient to contain aerosolized virus.

Build a PAPR!

As I've learned more about the risk of high pressure care, it's definitely not for the faint of heart and can continue as an engineering thread.

I wanted share a much lower risk, less controversial application of the same parts - which is a Powered Air Purifying Respirator (PAPR).

https://github.com/jcl5m1/ventilator/wiki/Build-a-Low-Cost-PAPR

CAD Interoperability Formats

I wanted to know if we can include some non-tessellated (Parasolid, Step, ACIS) CAD formats for the files so that people coming into the project don't have to remodel based on an STL master. I think this would help everyone get moving on the project, and speed up cooperation.

I recommend Parasolid, as it is the native format for many CAD systems, including Inventor, SolidWorks, and NX to name a few.

If this is not possible, I would recommend STEP files, as they are the international standard for CAD Interoperability, as codified in ISO 10303-21.

EUREKA! We discovered the at-home treatment for coronavirus that works! PLEASE READ CAREFULLY AND WATCH THE VIDEO

How to Kill the Virus With Hot Air.zip

I have recommended for decades that anyone feeling the first sign of a cold or flu, to take an immediate hot bath to kill the virus and many of the symptoms diminish much more rapidly. This has proven to be very effective in many research studies.

The problem is that the coronavirus can withstand temperatures that are too hot for the normal person's body. The coronavirus dies at a temperature of 130F to 133 F (56C). At hot bath, will not get the body to that temperature inside.

It turns out that the coronavirus lodges in the sinus cavities before the pneumonia starts. This is why the test for the coronavirus is done by sticking a swab up your nose and you can be without symptoms for up to five days after infection. Once it infects your lungs, you are likely to get extremely ill.

HOT AIR will kill the coronavirus. We can safely breathe in hot air that is a temperature of 130F (56C). People who live in desert environments, where it gets really hot, do this all the time. People who sit in a dry sauna regularly breathe in air that is 140F+. If you have a dry sauna at home you can use it. If you do not have a dry sauna, you can use a simple hairdryer, IF you use it carefully.

I heard about using a hairdryer to make hot air, but my concern was that people would burn their faces. Now, we have a SAFE technique that can be done at home with just water, a clean water spray bottle, and a hairdryer.

1. Use the water spray to moisten the face.
2. Then, use the hairdryer on the lowest setting and use one hand to block some, not all, of the air coming in the back of the hairdryer to reduce the volume of air.
3. Wave the hairdryer in front of your face but do not let it blow directly in one place to burn you. You can feel the air get hot.
4. Breathe in the dry, hot air for five minutes through the nose with the mouth closed.
5. Close your eyes as much as possible during the procedure (peeking only if you need to) to keep them from drying out. Use eye drops afterward, if your eyes become dry.

Attached is a video showing the safe technique. Please watch it carefully, to the end, to learn how to do this properly.

If you experience fever, headache, dry cough, or shortness of breath, these are the signs of the coronavirus infection. Fever is usually the first sign. Take your temperature regularly, and take the temperature of the ones at home with you as well. If you do not have a thermometer, use your hand to touch your forehead. You can easily feel a strong fever this way.

Use this breathing dry hot air technique the moment you notice a fever beginning. Continue to use it as described in the video.

You will not kill all the virus and you will still be infected, and you still may get sick. However, you will lower the viral load as it enters the body through the nose. This will help your immune system withstand the viral attack.

I have verified the information in this video by reading the scientific research papers (published and peer-reviewed) and it is 100% accurate.

Precautions:

If you are sick, always consult with a health practitioner over the telephone. This is not a substitute for receiving adequate medical care and not medical advice, only a healthy defensive technique that you must do properly, to do it safely. YOU CAN BURN YOUR FACE IF YOU DO THIS INCORRECTLY! Use caution and follow the instructions in the video. If you feel discomfort STOP! Wave the hairdryer to have it create hot air in front of your nose that you can breathe in. Do NOT hold the hairdryer still, while it is pointed at your face. Elderly people and children need assistance to perform this technique correctly.

Sources:
Elevated body temperature helps certain types of immune cells to work better, evidence suggests
https://www.sciencedaily.com/releases/2011/11/111101130200.htm

Heat at 56°C kills the SARS coronavirus at around 10000 units per 15 min
https://www.who.int/csr/sars/survival_2003_05_04/en/

Thanks to Robert in Romania for finding this video for us.

PLEASE PASS THIS INFORMATION ON TO OTHERS
We can defeat this virus with accurate information.

Request for 3D models

I've added a section on the wiki that contains a list of 3D printable parts that are already available, or models that I have received to design. Please take a look if you can help. The wiki page will likely get updated as requests come in.

https://github.com/jcl5m1/ventilator/wiki/3D-Printable-Parts

Contact request: Dr. Sidney Merritt UCSD - endotracheal tube

Don't use this site often, looked hard for any other means to contact other than issue requests but a Dr. Merritt at UCSD is looking to speak with the Creator of this device as it's being discussed in med communities across the net regarding the addition of an endotracheal tube

619-543-6240
Email: [email protected]

Facebook group

Awesome project. I'm particularly interested in the PAPR application.

I created a Facebook group focusing specifically on PAPR design: Open Source PAPR. Feel free to add a link in the README or wiki. Possibly easier to bring healthcare people into the discussion through Facebook rather than Github.

3d Printed PEEP Valve

YouTuber: CAMERADACTYL Cameras

Is posting #Projectopenair: https://www.projectopenair.org/ ventilator videos

3D printed PEEP Valve
Ventilator Check Valve
Ventilator Design Overview

Construction with homemade elements.

Hi from Spain
Many people do not have and may not be able to purchase any CPAP units, but they do have mat inflation pumps. Is it possible to use it to breathe and expel air into the lungs?

Type:
https://www.jardinitis.com/bomba-electrica-quick-fill-220-240v-invertible-bec83/?otcountry=ES&gclid=EAIaIQobChMIhKeZ0vqo6AIVSFXTCh1KFQPbEAYYAyABEgLKUfD_BwE

Thanks all the people

Code Life Ventilator Challenge - relevant info

Saw this challenge from:
https://www.agorize.com/en/challenges/code-life-challenge?lang=en

You covered many of these topics in the readme (great job btw!!), posting here for reference..

Ventilation performance

• Pressure controlled
• Inspiratory pressure up to 40cmH2O
• Expiratory pressure up to 20cm H2O
• Respiratory rate from 5-40 breaths a minute
• Measurement of tidal volume at the Y piece
• FiO2 from 20% to 100% in discreet steps of 10%
• Triggering—timed or patient-effort triggered
• Connect to standard masks and tubes
• Connect to standard oxygen connectors
• Accuracy (<10% for volumes and pressure, to 1 breath a minute for rate
• Can work on internal battery for >180 min
• Oxygen concentration NOT mandatory, recommended

Patient safety

• Alarms or limits
• Minute Ventilation (low/High) alarm
• Peak pressure, Low expiratory pressure and/or disconnection alarm
• Low expiratory pressure
• Oxygen concentration
  -Non-rebreathing valves

Device safety

• Electrical safety requirements
• Fire safety (i.e., pure O2 flowing)

Infection control

• HEPA filtered inlet and outlet
• Easy-to-clean surfaces

Design Requirements

User Interaction

• Simple to use--must not require specialized training
• Modular, with known failure potential for each component
• Easy to maintain (related to modularity)
• Settings legible from 1m
• Clear flow directions

Material and Manufacturability

• Widely available material (e.g. 3D printable filaments, plastic/metal sheets)
• Can be built locally using either simple tools or rapid prototyping (i.e. 3D printing, CNC, etc.)
• Only eligible material allowed (see list to exclude)
• Operational requirements
• Both 110V and 220V

IMHO

ventilators = lives

is there enough participation in the community to rapidly build a low cost (~$200-$300 USD) high quality ventilator system with reusable/replaceable parts that can be sourced from local hardware stores that meets these standards?

Question: What are you using to make the models?

.stl files are great for being ready-to-print, but hard to edit. Would it be possible to get the original files so we can work on them?

Question: Have you considered biphasic cuirass ventilation?

I wonder if biphasic cuirass ventilation might be a practical solution to this problem? These systems are external to the abdominal cavity and use both negative and positive air pressure to assist breathing (think wearable iron lung) http://www.ventusers.org/edu/Call-HaytekBCV.pdf

Benefits:

1. No risk of barotrauma
2. Can be administered with less medical knowledge
3. May be better for co2 retention issues
4. Air doesn't need to be humidified, filtered or purified.

Major downsides:

1. I feel like it could be challenging to get both negative and positive pressure from a cpap? I haven’t tried working with one yet.

2. Need to create the cuirass (abdominal shell).

PID Controller

Hi!!
I love your initiative, a humanitarian gesture <3
I would like to add something to your project, it's a PID controller
this controller which will be implemented in the arduino program will simply keep a constant pressure while playing on the variation of the speed you motor.
You can read some documentation to do it or i'll help you to do it.

Collaboration

Hi Johnny. My name is Doug Burke and I run a healthcare IT company called Cognitive Medical Systems (www.cognitivemedicine.com). Two things:

1. We might be able to help with the arduino request and software needed to run the ventilator at different setting and for different patients and/or diseases. My co-founder is a neonatologist and our CMIO is an anesthesiologist. We work a lot with the DoD and VA and so some work in this area around automation and decision support in anesthesia and ventilation.

2. The DoD is about to release a "challenge" grant/competition where, from what I understand, the challenge will be to create a ventilator from common off the shelf parts for less than $200. You should enter. Send me an e-mail and I can let you know when the competition is live.

My e-mail address is: [email protected]

Thanks for doing this work! Lots of interesting challenges at a critical time in healthcare delivery for the world.

Cheers - Doug

Alarms display

Hi! I'm Arysson Oliveira, an electronic engineer with some experience in firmware developement.

I'd like to help your project developing an software interface, that will show in a LCD display(16x2) some informations to the operator, because i think that should have any human-machine interface.

So, how could i help you?

TODOs?

This looks like a great project. I wanted to know if there was anything that needs work on this?

Other Similar Projects

A quick run around the internet yielded that other people are working along similar designs.

Seems hackday has some good insights as usual
https://hackaday.com/2020/03/12/ultimate-medical-hackathon-how-fast-can-we-design-and-deploy-an-open-source-ventilator/

https://hackaday.com/2015/09/25/hackaday-prize-semifinalist-individualized-breathing-apparatus/

Some other top links:
https://www.instructables.com/id/The-Pandemic-Ventilator/

https://innovationmanagement.se/2020/03/15/open-source-respirator-and-low-cost-ventilator-efforts-to-fight-coronavirus-covid-19/

http://letmegooglethat.com/?q=open+source+ventilator+projects (its a more concise link than a search result)

How can I help?

@jcl5m1 I would like to contribute to the project. We need to rump up these ventilators. How can I help?

Hairdryer + Arduino with a relay

I attached a tube to a hairdryer (with heating off) –– it seemed to work, meaning it blows really well. Planning to buy a relay for automation with Arduino.
Do you think this kind of build would be more accessible to a broader audience?
Also, I'll make the air go through a container with warm water to humidify it.

I'll be happy to hear back!

error when double click to enter peep mode (arduino restart) any help ?

i test the code on arduino and work motors esc arduino

5 speeds worked with clicks

but when i double click to enter peep mode arduino restart

can any one help with code ?

Device does not blow off CO2

Has anyone done a study on the failure mode of Covid-19 patients with acute respiratory distress? Is the problem that the SPO2 (oxygen) is too low, or is the problem that the pCO2 (carbon dioxide) is too high? (It's possible to have an acceptable SPO2 while at the same time having a harmful amount of CO2 in the blood- my first wife passed due to a complication from pneumonia with that exact issue.) Could this device be engineered to blow off the CO2 as well as increasing SPO2? Can that even be done without tracheoscopy or intubation?

Discussing sleep cycle detection using only the motor's current

Hello,
I will try to provide the beginning of an answer to that question. I am not intimate with Arduino nor the exact functionning of the human breathing apparatus, but I'll do my best.

When I first pictured it, it didn't seem feasible, because I didn't know if the motor would be directly affected by the process of exhalation. Turn on a servo motor, and rub your thumb in a way that it opposes resistance to its movement. Increased resistance will increase power consumption, within the servo motor's parameters of course. But it has been increasing because you have opposed effective resistance. In the case of a servo motor, an increase in air pressure would not change power consumption (its profile has barely any air resistance), but we'll come back to this later.

I assume the fan is a simplified DC motor with blades hooked onto it, which it probably is. The air flow we're creating goes directly in a tube connected to the patient's breathing apparatus with a mask that has a decent seal. Now, that's where I might be wrong, but that's how I picture it :

• When the patient exhales, pressure temporarily increases in the mask : that's how the air is getting out through the fins in the mask (pressure differential)
• Increased pressure in the mask makes it harder for the fan to pump air in, as there is resistance to the air getting into the mask, therefore pressure also increases in the tube, all the way down to the fan.
• Increased pressure around the blades increases air resistance, therefore the energy required to spin the blades at the same speed is now higher than it was when pressure was normal.

Now, I assume that the Arduino can detect these subtle changes in energy consumption by the motor. Therefore, I think it's theoretically possible to detect the different steps of the breathing cycle. Now a lot of what I've said is based on my own recollection of my engineering and physics classes. I might have got some things wrong, but I'm convinced this is more or less how it works. I'm waiting for people who might be slightly more qualified to confirm or infirm what I just said.

Sum-up : We should be able to detect the steps of the breathing cycle by measuring the fan's power consumption, higher consumption means exhaling, lower consumption means inhaling.

digital manometer

I made a digital manometer project which may help for breathing back pressure data collection and regulate the patients breath cycle. I'm thinking integrate the air pressure sensor to your circuit. The project is is documented at

https://www.hackster.io/binsun148/digital-manometer-cpap-machine-monitor-c1620a

Taking a stab at the To-Do's

I'm a programmer and a rookie on the hardware side, but I took a stab at some of the todo's from a product design perspective related to volume, pressure alarms, etc. The product is different after that and certainly no longer portable... however, it may steer someone smarter than me in the right direction and the pieces that were added are definitely low cost and readily available. I'd love to hear feedback!

Low Cost Ventilator Design.docx

Consider to use aquarium aerator?

I'm not sure that inflator blower is designed to operate in longtime continously.

I think Aquarium Aerator is better in mater of endurance.
10 L/Min flow is commonly market available.

I'm not sure about the pressure problem.

cmmiw

Offering help with the TO-DOs

Hello Johnny,

Very inspiring what you are doing, myself and a team of Biomedical Engineering Senior year Students would like to help with the TO-DOs, we have a pretty good background with both the Medical and the Engineering aspects of the electro-mechanical ventilation systems and would gladly invest our times in such project.

Email me if possible at [email protected]

DIY CPAP Style BLDC

In addition to exploring off the shelf 12VDC pump motors, it seems worth recreating a CPAP setup with 3D printed/off the shelf parts. Mark Rehorst's printable blower (specifically v2) + a cheap BLDC looks like a good option.

Basic pump / inflator use :why not?

What about using a basic pump like the one on amazon proposed in the read me ? Has someone tried ?
Any help with which Arduino extension card to purchase to pilot such a motor?

Economical Oxygen Sensor

An ultrasonic style oxygen sensor is readily available from numerous ebay sellers (mostly shipping from China). They generally have a detection range of 20-100% O2 concentration with an error of about 2% FS. This sensor can also measure flow from 0-10L/min with an accuracy of 0.3L/min.

Example: https://www.ebay.com/itm/Oxygen-Sensor-20-100-Oxygen-Gas-Concentration-High-Accuracy-9600bps-Industrial/372878328511?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Airbox Filter

Hi,
We are a group of 3 students of Mechanical Engineering of Sapienza University of Rome (Italy), we would like to help you to design and simulate (CFD simulations) of the airbox.
If you are intrested contact us!

Fine until intubatin

I suspect most ARDS cases will require intubation, which necessitates sedation, and features suction, CO2 removal, and a lot of autonomous monitoring. This might be good for emergency home care, provided other therapeutics are in place and continuous patient monitoring is employed.

Over pressurization

I don't think that 20cm h2o is very high, nor would cause any lung trauma. My personal NIV mask setup tops out at 25cm and isn't even fully inflating my lungs. Cough assist machines go into the 60s-70s of pressure, even if it is for brief periods.

All this to say, we likely will have problems getting high enough pressures, don't need to really worry about over pressurization. As a FYI, I'm from Washington State where Covid-19 is out of control. My pulmonologist is one of the top in the nation (Dr. Joshua Benditt) and we talked about too high of pressures on my ventilator. He wasn't concerned.

RFI and EMI testing

Some diagnostic hospital equipment (especially imaging) is especially susceptible to radio frequency interference. Brushless motors are known to create AM noise, and some inexpensive power supplies also emit quite a lot of RFI. I'm not skilled enough to propose exact solutions, but it seems typical remedies are often a capacitor here, an added ground there, and some ferrites chokes to eliminate common mode current. This device should be tested for excessive RFI to ensure many of them can get along with other equipment in hospital wards.

There are also EMI considerations for Arduino boards. This linked article explains some challenges in Arduino controllers hanging during specific EMI generating events, and some general suggestions to help.
https://forum.arduino.cc/index.php?topic=199671.0

If one of these devices becomes available in the Seattle area, I have software defined ham radio equipment and a small Faraday cage at work to observe a device in the 30kHz-77MHz range, and I know friends with access to larger cages as well as more specific equipment such as spectrum analyzers. I also have a solder workstation and a fair bit of surface mount experience.

A requirement definition would be needed: the RFI thresholds that hospital devices must not exceed, across the usable frequency spectrum. If this device can't be completely RFI-quiet, the effort should be focused on which frequency ranges are most sensitive to other life-saving equipment this device might encounter as it is wheeled with a patient through (I guess to be mainly ICU and medical imaging environments?).

Supply of Nano V3 Module

As a biologist, it is amazing to see how doable this is. My question is how quickly could the Nano modules be acquired. The demand for a million is going to hit like a freight train possibly as soon as two to three weeks. Is there any way that these could be sourced or scavenged locally? https://sccm.org/Blog/March-2020/United-States-Resource-Availability-for-COVID-19?_zs=jxpjd1&_zl=w9pb6

We could easily need a million more after that with a month because the projection in the attached article is with only 20 million infected. I will try to dumb this down so a biologist like me can understand it and so Joe the plumbers can start to build them in their garages. But it looks brilliant to me.

Alarms: low airflow

Not sure how easy - but you'd need an alarm when the airflow decreases (such as when the mask comes off the patient). Please add to your "to do list".
And yes, (1) last effort, and (2) probably best for PROVIDERS, not patients. GREAT idea, though - I am ripping an old CPAP apart right now

Use arduino quadcopter controller boards with barometric pressure sensor and/or quadcopter motors/ESCs

Many flight control boards intended chiefly for quadcopters (such as the atmega-based APM 2.5 and 32-bit boards similar to the pixhawk) have absolute pressure barometers that, with some tubing, could be used to sense pressure to help sense and control the cyclical breathing process. This hardware is already in the hands of many with the aptitude for DIY respirator construction.

Additionally, air pumps/turbines/compressors/fans can be made from quadcopter speed controls and standard-sized quadcopter motors with 3D-printed mechanical parts.

Project Clearification

I'm a little confused on what the goal is. Are we trying to turn CPAP machines into respirators or are we making respirators from scratch?

Further development

Hello. I really think it's really neat how you got a system up and working quickly. Do you have plans to refine and improve the system? For example, I could suggest:

-- Adding pressure and airflow sensors. Purchase a few and evaluate performance.
-- Creating a 3d-printed turbine design with a quadcopter brushless motor.
-- Consider redundancy to improve reliabilty. Adding redundant turbines, power supplies etc.
-- Adding pressure relief valves to limit the maximum/minimum pressure in the pipe (to prevent lung damage in the event of firmware error).
-- Creating a custom motor control board based on STSPIN32F0 reference design, or perhaps something like: http://www.electronoobs.com/eng_arduino_tut91.php (there are many designs online). This could be more predictable that an hobby esc, that might have some odd modes (overheat shutdown or something), and could do better self-test routines (monitoring motor current etc.)
-- Creating a standard protocol for the motor control board, main control board, (perhaps sensors), and PC-based diagnostics software to communicate, over UART or perhaps something like CAN. These packets could perhaps optionally be relayed over a network to a central location, using an esp32 with wired or wireless connection. I am thinking something like mavproxy/wiimote protocol/AT commands.
-- Creating diagnostics software with Qt that show pretty graphs of pressure, airflow, motor current and rpm etc., useful for developping control algorithms and perhaps showing useful info for the doctor.
-- Develop improved methods to verify pressure and airflow.

Any of these could be investigated and developped by small teams of 2-3 people.

Manufacturability

Would appreciate a community opinion on this thought.

It appears as though 99% of the complexity would reside within a few components:

• control unit
• interface
• flow sensor (for Tidal Volume control)
• pressure sensors

All of those components are available in the hundreds of thousands on digikey right now. A build-your-own-kit seems manufacturable en-mass permitting doctors to utilize whatever pumps and filters and hoses happen to be on-hand.

• Control Unit: The software could be theorem-proven and verified. It could include necessary calibration routines, and calibration kits would be needed in much smaller quantities.

• Interface: The single interface would permit improvised ventilators the world around to share an interface, making training easier.

• Flow Sensor: There's probably a reasonable way to rig up a hot-wire anemometer with appropriate sensitivity within the necessary flow-rate ranges to be useful (haven't one the math on that one yet)

• Pressure Sensor: Available on digikey

If all items were combined within a single control unit that triggered external relays for pumps and valves, then it might empower groups to build their own using supply-chain segments that are unlikely to be affected. For example, several impeller-style bilge pumps for marine pleasure-craft can produce the necessary pressure gradient, work on 12 volts, and are unlikely to be otherwise necessary for the pandemic. Diesel fuel filters may not stop virus particles (they are 2 micron), but would catch many droplets.

This entire concept, of course, is predicated upon the concept that availability of physical pieces such as pumps and control units, are the limiting factors.

open-ventilator

I made a proposal for further developent of your project. Readme copied below.
https://github.com/hobodrifterdavid/open-ventilator

open-ventilator

Please see Johnny Lee’s ventilator project (the video gives a great overview): https://github.com/jcl5m1/ventilator).
It's a working starting point. The idea here is to create a more flexible and robust device that could be suitable for production in quantity. A ventilator with a microcontroller, airflow and pressure sensors, and a digitally controlled blower, can potentially perform any ventilation ‘mode’.

There are plenty of good ventilator designs. There are many manufacturers of simpler ventilators (still $thousands) that could increase their output for a couple of weeks. (ICU ventilators probably have complex supply chains, and the tooling may not be set up for high-rate production.)

Consider Egypt, 100m people living on a thin strip of land by the Nile, the Philippines, rural Ukraine, India. A yearly salary wouldn’t cover a Chinese ventilator. This design has potentially few parts. Tooling up means machining a few molds. Email gerbers to a PCB house. Get a few automatic screwdriver machines etc.

This Google doc (https://docs.google.com/document/d/1KpPWYRb1A637Cp5KIhhKtuGFS8Cdm5fGra3TTwwrBKo/edit#) is a proposal for progressive further development of Johnny's design, component by component. There's also some useful resources and information that I have collected from the last couple of days of discussion on helpfulengineering.slack.com , and elsewhere.

Global Map for Startup Innovations - Get Funding for this Awesome Project

Invitation to submit this project to STARTUPBLINK’S CORONAVIRUS (COVID-19) INNOVATION MAP
Get money for this project and colloborate globally
https://www.startupblink.com/blog/coronavirus-innovation-map

With the emergence and clear effect of the Coronavirus (COVID-19), people around the world are dramatically changing all aspects of life. This is an unfortunate circumstance that no one can escape, but as human beings are resilient creatures, we survive, and most importantly, we innovate.

No matter who you are, one of the things we need more than ever is to stay well-informed and to be aware of not only the bad but the good that is happening in the world. It is also important to know that public institutions, corporations, and startups around the globe have been working tirelessly since the emergence of the coronavirus in hopes to find a solution or contain this virus.

We at StartupBlink recognize this change, and we decided to do something about it. We are proud to announce the launch of our contribution to help the global crisis, the Coronavirus Innovation Map.

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Our goal with the Coronavirus Innovation Map is to build a platform with a map of hundreds of innovations and solutions that help people cope and adapt to life amid the coronavirus, and to connect innovators.

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In order to create an innovation directory, we at StartupBlink have developed a technology to research and map innovation around the world since 2014. We know that curating all relevant data in a short amount of time is not achievable by a single person or company, this why we will need everyone’s help. Through crowdsourcing and the help of the community, we will be able to cover the gaps and have as much information as possible. As a community, we will be able to reach this ambitious goal of connecting innovators and people with solutions.

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Love to connect and collaborate from Cleveland

Hello Johnny,

This is amazing work you've done on this thus far, and I woke up this weekend from my own CPAP wondering the same questions and started making calls.

I've also been in touch with Matt Hearn who has written a great medium article himself on the topic and has referenced your work, but yours has been the most comprehensive effort compiling facts and feedback that corroborates with many of my conversations today about the core issues around adapting CPAP's purposefully.

I'm working on getting a hold of Robert Chatman, whose book on fundamentals of ventilation mechanics you linked, who is from Cleveland. I also have medical industry design firm interested and reaching out to their respiratory industry contacts. BioEnterprise in Cleveland has also expressed interest and support, and there may be a proposal to Vulcan (US Govt) due this Wednesday that might be worth entering.

What is the best way to be in touch?

All the best,
JT Tan
JT at Case dot edu

Efficient No Power Airway Shunt

I think with respect to task (6) it is easy to have some-kind of spring loaded shunt, the problem would be making it power efficient. A potentially efficient way to do this would be a small servo which opens a hatch on the airway, that triggers when the power level reaches a certain "low" point. The issue with this is that it functionally decreases the power that can be run from any one-battery, as the "low" power point needs to be still above the complete discharge point of the battery, such that sufficient power remains to trigger and operate the airway shunt fail safe. It might be possible to create a pneumatic hatch, which opens when the flow rate drops below a certain rate, but these typically only work in continuous flow systems, which I am not sure we have here. Also, when starting the system, this hatch would need to be manually shut until steady state conditions are met.

Pressure relief valve

Any ideas on how to add a pressure relief valve?

https://mfimedical.com/products/allied-healthcare-omni-vent-transport-ventilator-pressure-relief-valve?gclid=EAIaIQobChMIr6P2kLCs6AIVBKrsCh0Pqw9IEAsYAiABEgIHp_D_BwE

any one can help how can connect wires to arduino and esc ?

via whatsapp [phone]

Percussive Ventilation

Consider looking at Percussive Ventilation. All you need is a pressure regulator and a valve to turn on and off flow. The handset uses entrainment via a venturi.

Non Invasive Bubble Helmet

Here is an article from Respiratory Therapy Magazine in 2016 highlighting a study where positive pressure bubble helmets reduced intubation rates of ARDS patients.

The intubation rate was 61.5% for the face mask group and 18.2% for the helmet group. The median number of ventilator-free days was significantly higher in the helmet group (28 vs 12.5). At 90 days, 15 patients (34%) in the helmet group died compared with 22 patients (56%) in the face mask group. Adverse events included three interface-related skin ulcers for each group.

2020 JAMA Demostration with vent settings
Original Medical Article
2013 Meta Study

This is the same style seen in the Italian hospitals. If the results are being replicated, an open source bubble helmet seems to be an appreciable public health goal.

Test Lung Research

In regards to Test lung research, what needed to be done. I'm a biomedical equipment tester at a hospital with access to many different types of TMDE (Testing Measuring and Diagnostic equipment) and we frequently test ventilators and Cpaps. Are there specific tests that need to be ran?

I'm going to try building this in our facility and once it's made I can test it using the same test setups we use for normal ventilators, even "dumb" ventilators. Once made i'll post what models and results i got.

Filtration for Intake

This is a great project, and I am really excited to help. One thing I note is that it is likely we would need some kind of filter on the respirator intake, so that any kinds of allergens or other harmful particles in the environment are not transferred to the patients lungs. Just a thought.

Power Supply - Redundancy

With regards to the desire to have this unit operate in the event of a mains power outage.

12v Car Battery

• Car Battery Trickle Charger
• Solar Charger

As I understand it, a car battery has a capacity of >45ah. In the event of a lockdown, sourcing a battery from a vehicle shouldn’t be too difficult.

Car battery chargers are a little more challenging to source than a USB power supply, but worst case scenario, the battery could be recharged from a vehicle (either just leaching power from the fitted battery, or connecting the CPAP battery back to the car and running it for a period of time, letting the alternator charge it back up).

Just an idea. Smarter people might refine it from here.