Abstract: A volume ventilator having a plurality of integrated modes of operation for providing a patient with a flow of breathing gas under pressure. A plurality of adjustable setting devices each producing an individual threshold signal related to a parameter of the gas flow. Mode switching means provides for the selection of at least one mode signal. Each threshold signal is compared with a common variable signal for producing a plurality of control signals. At least one of the control signals is selected in accordance with the selected mode signal and that control signal is applied to a valve system for controlling flow of gas to the patient. In this manner, the setting devices may be continuously adjusted to change one or more of the threshold signals without varying any of the other threshold signals. There is further provided a comprehensive system of alarms.