Normally, the idea of DIY medical equipment would be inadvisable, to say the least, but as Johnny Lee outlines — with a healthy disclaimer — on his GitHub page, we are potentially facing a critical worldwide shortage of ventilators due the COVID-19 pandemic. To that end, while hopefully a homemade solution won’t be necessary, this project outlines some ideas on how to construct a makeshift ventilator out of readily available parts.
The idea here is that a fairly common continuous positive airway pressure (CPAP) machine could be converted into a ventilator in order to force air directly into a patient’s lungs. It’s designed to be controlled with an Arduino Nano, though a Teensy2.0++ was used during testing, and presumably any microcontroller could be implemented. The function of the Arduino here is simply to drive the machine’s brushless DC motor (BLDC) via an electronic speed controller (ESC) to push air in and out at the proper rate. This setup would provide more than enough pressure to theoretically match ventilator recommendations for COVID-19 patients.
There are also resources for an adapter to use with an air filter, as well as a mouthguard to supply air to someone’s mouth if another option is not accessible. It’s even possible such a device could be constructed with a simple inflator/air compressor pump. Like the rest of the article, work here is highly untested, and should be used as a last resort, but at least if it comes to that we'll have a place to start.