It's just an air pump - a suitable fan would be sufficient. It just blows normal air through a tube in to a mask. There is a bit of control electronics to allow the appropriate air pressure to be achieved in the lungs. It's about as simple a "ventilator" as you can get - indeed it's not technically a ventilator at all.
I'd guess that Mercedes are just providing the manufacturing facilities as they can rapid prototype stuff etc. The actual device has been designed by the academics who reverse engineered an existing machine.