Early during the 2020 pandemic there were concerns about the limited availability of ventilator machines and I asssisted with a project to reverse engineer the inexpensive and readily available ResMed CPAP machines to see if it was possible to turn them into ventilators.
It turns out that the CPAP, BiPAP, and iVAPS models all have the same firmware and functionally the same hardware. Flipping a few bits in the firmware image enables the additional modes that were already present. This meant that it was possible to use an STlink programmer to modify those configuration bits and turn the cheap machines into the more capable ones needed by the hospitals.
The other major contribution was reverse engineering the GUI libraries and code, making it possible to write new firmware extensions, similar to Magic Lantern. One of the demos draws a chart of patient lung pressure and the assisted boost from the machine, allowing clinicians to see how patients are doing without having to go through multiple menus.
More information about the projects is at https://airbreak.dev/