A system for delivering oxygen, comprising: an oxygen source; a ventilator operatively connected to the oxygen source to receive a supply of oxygen therefrom, the ventilator configured to provide gas including a mixture of the supply of oxygen and air to a patient through a breathing circuit; a valve operatively connected to the ventilator and the oxygen source, the valve having a) an open position in which the ventilator receives the supply of oxygen from the oxygen source and b) a closed position in which the ventilator is not in fluid communication with the oxygen source; a sensor configured to measure breath flow information for the patient; and a computer system that comprises one or more physical processors operatively connected with the sensor and the valve, characterized by the one or more physical processors being programmed with computer program instructions which, when executed cause the computer system to: determine a volume of gas delivered to the patient during a breath cycle of the patient and an inspiratory volume of gas delivered to the patient during an inspiration phase of the breath cycle by using the breath flow information; and provide input to the valve based on the determined volumes, the provided input causing a movement of the valve between the open and the closed positions. an oxygen source; a ventilator operatively connected to the oxygen source to receive a supply of oxygen therefrom, the ventilator configured to provide gas including a mixture of the supply of oxygen and air to a patient through a breathing circuit; a valve operatively connected to the ventilator and the oxygen source, the valve having a) an open position in which the ventilator receives the supply of oxygen from the oxygen source and b) a closed position in which the ventilator is not in fluid communication with the oxygen source; a sensor configured to measure breath flow information for the patient; and a computer system that comprises one or more physical processors operatively connected with the sensor and the valve, a ventilator operatively connected to the oxygen source to receive a supply of oxygen therefrom, the ventilator configured to provide gas including a mixture of the supply of oxygen and air to a patient through a breathing circuit; a valve operatively connected to the ventilator and the oxygen source, the valve having a) an open position in which the ventilator receives the supply of oxygen from the oxygen source and b) a closed position in which the ventilator is not in fluid communication with the oxygen source; a sensor configured to measure breath flow information for the patient; and a computer system that comprises one or more physical processors operatively connected with the sensor and the valve, characterized by the one or more physical processors being programmed with computer program instructions which, when executed cause the computer system to: determine a volume of gas delivered to the patient during a breath cycle of the patient and an inspiratory volume of gas delivered to the patient during an inspiration phase of the breath cycle by using the breath flow information; and provide input to the valve based on the determined volumes, the provided input causing a movement of the valve between the open and the closed positions. determine a volume of gas delivered to the patient during a breath cycle of the patient and an inspiratory volume of gas delivered to the patient during an inspiration phase of the breath cycle by using the breath flow information; and provide input to the valve based on the determined volumes, the provided input causing a movement of the valve between the open and the closed positions.