Abstract: A multiple functionality pneumatically controlled medical ventilator provides precision regulation of tidal/forced breathing, and continuous positive airway pressure (CPAP)-based spontaneous breathing capability. The ventilator includes a patient breathing gas coupler that is adapted to be coupled to a patient airway breathing interface, and an input port to which a pressurized breathing gas is coupled, A pressure regulator supplies breathing gas at a positive pressure sufficiently higher than nominal lung pressure to prevent collapse of the patient's lungs. A tidal breathing gas supply unit periodically generates a volume-regulated tidal breathing gas for application to the patient airway breathing interface, while the CPAP valve supplies a pressure-regulated breathing gas to the patient airway breathing interface, in response to a patient demand for breathing gas that is exclusive of the tidal breathing supply.