A patient ventilator assembly for connection with an endotracheal tube, where said endotracheal tube is constructed and arranged to be installed through a patient's trachea below the patient's vocal cords so that an exterior open end of the endotracheal tube is exterior of the patient and an interior open end of the endotracheal tube communicates with the patient's airway and lungs, the ventilator assembly comprising: a conduit for connection with the exterior open end of the endotracheal tube and providing inhalation and exhalation passages communicating with one another; a pressure sensor (54, 58) to detect the phase of respiration that the patient is in; controllable inhalation and exhalation valves in the inhalation and exhalation passages, respectively; and in that the exhalation valve is capable of being controlled to move between fully closed and fully open and any position of partial opening therebetween, and characterized in that the ventilator assembly further comprises a controller adapted to control the inhalation valve and the exhalation valve so as to provide repetitive respiratory cycles, each including an inhalation phase and an exhalation phase, wherein during the inhalation phase the inhalation valve is open and the exhalation valve is partially closed and a flow of gas is allowed to pass through the inhalation passage and the endotracheal tube into the patient's airway and lungs, the controller being adapted, based on the data obtained from pressure sensor (54, 58), to control the exhalation valve for use in two exhalation phase modes, in which the inhalation valve is partially or fully closed during a second mode, and fully closed during a first mode, the two modes including: a first mode wherein the exhalation valve is open during the exhalation phase, allowing the gas in the patient's airway and lungs after the preceding inhalation phase to pass through the open exhalation valve and through an outlet of the ventilator assembly, and a second mode wherein the exhalation valve is maintained partially or fully closed so that the patient causes the gas in the patient's airway and lungs after the preceding inhalation phase to flow past the patient's vocal cords and out of the patient's mouth, thus facilitating the patient's ability to talk. a conduit for connection with the exterior open end of the endotracheal tube and providing inhalation and exhalation passages communicating with one another; a pressure sensor (54, 58) to detect the phase of respiration that the patient is in; controllable inhalation and exhalation valves in the inhalation and exhalation passages, respectively; and in that the exhalation valve is capable of being controlled to move between fully closed and fully open and any position of partial opening therebetween, and characterized in that the ventilator assembly further comprises a controller adapted to control the inhalation valve and the exhalation valve so as to provide repetitive respiratory cycles, each including an inhalation phase and an exhalation phase, wherein during the inhalation phase the inhalation valve is open and the exhalation valve is partially closed and a flow of gas is allowed to pass through the inhalation passage and the endotracheal tube into the patient's airway and lungs, the controller being adapted, based on the data obtained from pressure sensor (54, 58), to control the exhalation valve for use in two exhalation phase modes, in which the inhalation valve is partially or fully closed during a second mode, and fully closed during a first mode, the two modes including: a first mode wherein the exhalation valve is open during the exhalation phase, allowing the gas in the patient's airway and lungs after the preceding inhalation phase to pass through the open exhalation valve and through an outlet of the ventilator assembly, and a second mode wherein the exhalation valve is maintained partially or fully closed so that the patient causes the gas in the patient's airway and lungs after the preceding inhalation phase to flow past the patient's vocal cords and out of the patient's mouth, thus facilitating the patient's ability to talk. a first mode wherein the exhalation valve is open during the exhalation phase, allowing the gas in the patient's airway and lungs after the preceding inhalation phase to pass through the open exhalation valve and through an outlet of the ventilator assembly, and a second mode wherein the exhalation valve is maintained partially or fully closed so that the patient causes the gas in the patient's airway and lungs after the preceding inhalation phase to flow past the patient's vocal cords and out of the patient's mouth, thus facilitating the patient's ability to talk.