During this covid-19, I was thinking about designing a low cost simple ventilator using a blower. There is a limit of the inspiratory and expiratory pressures, the inspiratory pressure being higher. Can anyone tell me how can I adjust the pressures? I also don't know how to control the fraction of the inhaled oxygen (FiO2). Will an oxygen concentrator work in this case? If anyone wishes to look into the plan, it is in this link.

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    $\begingroup$ I think you are out of your depth. Your best bet, if you want to help without killing somebody, is to join one of the thousands of projects already in progress. Pick a good one that has qualified people involved. $\endgroup$
    – Transistor
    Mar 28, 2020 at 9:42
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    $\begingroup$ Medical respirators are multi-tens-of-thousand dollars devices. You can come up with hundreds of ways to push air into someone's lungs via valves, dampers, etc., but none would meet the actual needs, unless your objective is to recreate a device from the 1700s. A forge-style bellows would work to move air (think Princess Bride Mighty Max); saving a life may be harder. $\endgroup$
    – Tiger Guy
    Mar 29, 2020 at 6:33
  • $\begingroup$ First, they are right. Second, all (great) inventors receive such comments and responses. That is because (great) inventors and innovators are a bit crazy. You have to determine if they are right or you can overcome, if you are crazy fail, or crazy succeed. $\endgroup$
    – Ack
    Mar 29, 2020 at 19:40

1 Answer 1


I am going to answer the question on lowering the pressure, but I will not encourage you to use it on any patient due to the fact that professional medical equipment requires rigorous tests, using a homemade medical device would pose a large hazard on the patient.

Since your goal is to build a low cost ventilator, I believe a simple adjustable valve can lower the pressure effectively by draining part of the supplied gas away.

  • $\begingroup$ That is generally true, but many (most?) such valves, especially inexpensive ones, use a spring to hold a plug onto the outlet. At the low pressures needed for medical ventilation (typically under 0.5 psi), such valves may have troublesome behaviors. For example, the weight of the plug itself becomes a much bigger factor, so the orientation of the valve starts to matter. If you make a ventilator that tests fine upright, but fails if someone tips it over, that's kind of a big problem. $\endgroup$
    – TextGeek
    Apr 23, 2020 at 19:14

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