A breathing device comprises a respiratory gas source for generating a gas pressure for a patient, delivered by a respiratory mask, a measuring unit for measuring a measurement quantity characteristic of inhalation or exhalation, and a control unit which determines the patient's tidal volume from the measurement quantity and compares this with a setpoint value of the tidal volume. The control unit regulates the respiratory gas source such that the generated gas pressure is made available until the setpoint value of the tidal volume is reached. In addition, further regulation of a parameter characteristic of the patient's breathing is carried out. The method for controlling a respiratory gas source with a control unit for a patient's breathing comprises regulation of the patient's tidal volume by providing and applying inspiratory pressure and simultaneous regulation of a further breathing parameter.
