This invention provides ventilators that provide superior air-oxygen mixing and gas delivery. The ventilators that supply a gas mixture to the lungs of a subject. The gas mixture comprises a first gas (e.g. oxygen) and a second gas (e.g. ambient air). The ventilators comprise a first gas inlet, a second gas inlet, flow modulator of the first gas, a flow modulator of the second gas, a junction configured to mix the first gas and the second gas, a patient interface configured to deliver the gas mixture to a subject, a pressure sensor, a plurality of flow sensors comprising at least a first flow sensor and a second flow sensor, and at least one controller configured for obtaining data from the pressure sensor and flow sensors and controlling the flow modulators to provide a gas mixture having a target pressure and a target oxygen content.
