Respirators

=== diy solutions ===
https://hackaday.io/project/170507-cosv-cam-open-source-ventilator
https://hackaday.io/project/170622-visp-ventilator-inline-sensor-package/discussion-142566
https://www.instructables.com/id/The-Pandemic-Ventilator/
https://archive.org/stream/PopularMechanics1952/Popular_Mechanics_01_1952#page/n259/mode/2up emergency wooden respirator, old pop.mechanics article(iron lung) p.260 of pdf. 
https://panvent.blogspot.com/
DIY respirator Vietnam Several times in the care of a loved one who was treated in a hospital, "amateur engineers" found that squeezing air bubbles with their hands to aid breathing was extremely difficult and costly. Determined to create a machine to work instead of people, he has successfully created a personal breathing machine "made in Vietnam".
https://hackaday.com/2020/03/12/ultimate-medical-hackathon-how-fast-can-we-design-and-deploy-an-open-source-ventilator/
https://www.youtube.com/watch?v=xVNsE405UWI scuba rebreather 
* https://www.crappie.com/crappie/live-bait/349144-homemade-oxygen-generator-cost-8-a/ 
* https://www.youtube.com/watch?v=jHg4Dx3rPSo homemade o2 generator
https://rebelem.com/high-flow-nasal-cannula-hfnc-part-1-how-it-works/
https://chemistry.stackexchange.com/questions/59305/production-of-hexavalent-chromium-during-electrolysis-using-a-stainless-steel-as
=== commentators ===
Measuring the pressure of the air might be challenging. Industrial/automotive pressure sensors are, most of them, for much higher pressures and are not sensitive enough for this application. But building a vertical transparent water tube would do the trick (communicating vessels). To measure the water high a simple UV led+receiver would tell the system “this pressure (water height) has been reached”. Add 2 or 3 led+sensors and you can effectively control the pressure with less than 10US$ in material. Aim for 30cm of water. Normal CPAP devices operate between 6 and 15 cmWater pressure.
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As a backup to an automated vent there is always a bag valve mask(BVM) available in the ICU/OR/ambulance to manually ventilate an anaesthetized or intubated patient.
After thinking of designs along the lines of a modern vent I decided for this situation an old school iron lung would be most reliable. There is a reason that they went with that design in the old days and kept it for so long, it is very reliable and safe considering how simple and cheap it is, it is also easy to manually pump in a power failure, way easier than a BVM and there is not risk of extubation and maybe tubing the esophagous(patient dies in ~4-5min) when a human ventilator gets tired and maybe yanks on the tube. The only big downside is mobility, but we are not talking about a life sentence in the ‘lung’ in this case.
It is really important though for a high patient to care ratio operation that alarming be based on capnometry(exhaled co2) as o2 sat can stay near 100% for so long in an insufficiently vented patient while their blood co2 acidity pickles and kills everything except a slowly dying brainstem.
As for oxygen, yes any airgas operation can produce plenty for any medical need but probably not certified, so a cheap way to verify purity and safety would make things better.
So if there is a mass need for ventilation I suggest
-DIY design for iron lungs for ventilation(a simple Sten gun engineering; from standard parts design)
-industrial oxygen supply
-shotgun airway tech courses(1-2 days) for EMT basics and other first responders or medical workers to manage a large number of people on vent
Important to rotate the emergency airway techs every hour or two and have a good strict oversight so they can’t easily space out.
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So about the iron lung: was invented originally to treat patients with polio-induced paralysis of phrenic nerves (these control the diaphragm). These patients breathed ambient air, and their pulmonary function was intact (compliance, oxygen diffusion etc)
I don’t think an iron-lung type device would benefit a patient in a COVID-19 setting. COVID-19 patients have severely compromised pulmonary function due to massive infection (COVID-19 virus + bacterial superinfection) with concomitant edema. Both of which cause reduced O2 diffusion and pulmonary compliance. I imagine most die in ARDS and multi organ failure.
We therefore need high oxygen concentrations (up to 100%) and high ventilation pressures (up to 30mmHg, maybe higher for a short time only) to the keep all lung segments open and press oxygen through the pulmonary edema to the red blood cell.
In the COVID-19 setting the proper cascade of respiratory treatment, in my opinion, is as follows:
conventional o2 nasal cannula (up to 6 liters air per Minute)>
mask and reservior (up to 15 liter air per Minute)>
high flow nasal cannula (20-60 liter O2 per Minute, adjustable FiO2)>
intermittent CPAP mask>
respirator on CPAP setting (PEEP 5mmHg, adjustable FiO2)>
respirator on BIPAP setting (max pressure 30mmHg, PEEP 5mmHg, adjustable FiO2)>
ECMO
please advise if I missed important points or if you would change the escalation cascade.
Concerning the project I suggest dividing it up into several groups (high flow nasal cannula group, CPAP group, BIPAP group, etc) according to the cascade. There may be several projects within each goup depending on the approach taken (repurposing existing products vs constructing / hacking a new machine), as well as the use case (out-of-hospital vs. in-hospital).
A big concern in my opinion is sourcing oxygen and power in an out-of-hospital setting
=== 4 ===
In terms of practical short-term usage, the main concern would be contamination of airflow from the passage through the warm water bath. The water would need to be acceptably sterile: straight municipal tap water for first-world countries is likely acceptable, using total-loss circulation (water flows in from tap, passes through the heater to warm it, passes through the chamber where the airflow bubbles through, is dumped out). In the event a constant clean water supply is unavailable, things become trickier. And chemical sterilisation methods for recirculating water would need to not offgas into the airflow (or any offgassing must be at worst unpleasant but not actually harmful). Either passage through a boiling stage or an extremely high intensity UV treatment with sufficient dwell time could work. Design of the bubbling chamber would be tricky, it would need to be sized to avoid aspirating water into the air stream but not so large that a stagnant film could build up in the warm humid environment.
=== 5 ===
concerning the non-sterile water:
Use sterile 0.9 % saline solution instead (if it’s not corroding your machine). This should still be available in a hospital. I’ve used this as a medium for inhaling horses while testing drugs in my doctoral thesis (I’m a veterinarian). At least it is sterile and because the electrolyte concentration is the same as in the body it is less irritating than (more or less) pure water.
And to all McGyvers out there:
One thing you should all be aware of: We are talking about highly critical human patients whose lungs are already under outmost stress. Every little mistake like
– a certain number of pathogens / particles in the air (filtering ?)
– the pressure being minimal too high for a certain amount of time (can you regulate exactly?)
– other volatile substances in the air (from rubber or plastic) inducing additional inflammation in the lower airways
– accumulating CO2 (dissolves to HCO3- and H+ which changes pH in lungs and in the blood!)
can be the difference between life and death.
Are you aware that maybe you make things worse than without your device?
Just a comment. I’m not talking about regulations but I have ventilated > 2000 horses undergoing general anaesthesia and horses are even more critical than humans considering their pulmonary function. 
=== 6 ===
Hydrogen as a medical gas to treat respiratory illness is fairly new. It was used in Hubei China to help treat ARDS. Perhaps it would be good to integrate its use along with regular oxygen with the ventilator and add its settings. Hydrogen gas has been shown to suppress Cytokines. Here is the literature on hydrogen as a medical gas – https://www.frontiersin.org/articles/10.3389/fonc.2019.00696/full
=== 7 ===
Finally, another approach:
4) Get at-home or in-patient oxygen concentrators to people to decrease the number who ever end up requiring ventilation. Supplemental oxygen, especially at home, is dramatically simpler, cheaper, and safer. Other approaches can decrease the likelihood that people ever need a ventilator.
Question to appropriate specialists on the thread: to what extent do you believe that early administration of oxygen would decrease the incidence of patients presenting who ultimately require ICU care, ventilation, etc? Would this be an appropriate way to take the burden off of downstream systems?
=== 8 ===
Alright. Think outside the box with me. We modify 3 axis 3d printers with heated build plates. Use the x axis as a breath bellow, the Y axis as an exhale bellow, the heated build plate as a water warmer for a humidifier, and presto. After designing the bellows and routing the tubing you have it. All temp, speed, volume can be controlled with a modified slicer program. Add a ozone generator for the exhaled and contaminated air and you can keep the infection from spreading to everyone else.
Hacked Jacobs ladder for ozone generation. 
All the objections here are easy to overcome – Doctors define the parameters, engineers and hackers find the hardware to meet those standards. You don’t have to be both. Teamwork.
The Bird ventilator was the industry standard for years, and the first items -delivered- to hospitals were made with bakery tins and a repurposed doorknob. They replaced a British unit using a car wiper motor with the arm inflating and deflating a bellows.
It does not have to be complex, but it does need to be defined by medical personnel. Only once defined can we see the challenge we have to meet.
Organizing that team is the first imperative.
=== air compressor ===
:If you’re thinking of hospitals full of these, I’m, thinking of a regular industrial compressor and a bunch of PVC pipes. It would need some extra plumbing and safety stuff of course, but that’s much easier on a large scale. So if you’re serious about this, then skip the usual suspects and put some doctors who know what they need together with engineers which have experience in industrial equipment. 
You can not use a regular piston based air compressor because of issues with airsole oil droplets. You could use a [cleaned] diagram based hardware-store compressor, but these are less common. I am onboard with your PVC plumbing ideas, that part is fine :)
=== specs ===
o design we need technical details:
1. Max flow rate 6lpm
2. Max allowed pressure???
3. Desired humidity level???
4. Oxygen mix range???
This is what I’m wondering about as well. I’ve got a working prototype made from a high-volume manual pump typically used for inflatable mattresses and inflatable rafts, driven by a simple “piston”(a spinning wheel with a rotatable elbow, like a steam engine) that is powered by a geared DC-motor from a drill which is being water-cooled. By NO means is it a perfect device, but in an emergency I would prefer it over having nothing.Currently, I’m working on adding a way to humidify the air and a way to set a pressure range/breathing speed.
=== patents ===
https://patents.google.com/patent/US3191596 from 1960
=== links ===
RoboTics
Category:Robotics