A ventilator-resuscitator device comprising a mixing chamber, a compressor, a controllable pressure-relief vent, and a controller, is provided. The mixing chamber has air and oxygen inlets, and an outlet. The compressor is configured to operate crate at two or more power levels and to increase, by a different amount at each power level, the pressure of a gas flowing between a low-pressure side thereof and a high-pressure side thereof, thereby producing a pressurized gas, the low-pressure side being in fluid communication with the outlet of the mixing chamber. The vent comprises an orifice configured to bring the high-pressure side of the compressor into fluid communication with the atmosphere. The controller is configured to direct operation thereof and to regulate the pressure of the pressurized gas by selectively operating the compressor at one of its power levels.
