Hardware is done until testing reveals issues with it.
So far you can use a BLDC gear motor, a small worm drive gear motor, or a Nema 23 stepper to drive this.
Torque requirement is 15-30 kg/cm and speed requirement is 22 to 30 rpm.
We need to deliver a faster inhale stroke than previously specified, so torque requirement is now 30 kg/cm and speed requirement is 48 rpm. This may put it beyond what our (cheap) Nema 23 can do and probably puts my first pick for the BLDC out of the running as well. The previous number for inhale time was 1.5s. I picked the parts based on 1s. The actual time from the UK document is now 0.3s. Ooof. Everything gets harder.
Pressure and volume delivered will be directly adjustable. Maximum pressure will be configurable. Maximum pressure should also likely be backed up by a physical pop-off valve. We have a reliable 3D printed valve already developed for us.