A device for ventilating a patient intubated with a tube, comprising: - a breathing gas source, - at least one sensor, - a control unit, wherein the control unit is connected to the at least one sensor for detecting a measurement value, - an apparatus (4, 5, 6) for connecting to the tube, and - an analyzer, wherein the control unit has a pressure generator for specifying at least two pressure levels generated by the breathing gas source, and wherein the device is designed such that a breathing gas flow from the breathing gas source is fed to the patient with the pressure specified by the pressure generator for ventilation by means of the apparatus and the tube, and wherein the pressure generator is designed to carry out the following method steps: - in a first, initial breathing cycle, specifying the pressure initially to an expiratory level Pe1 and then to a higher inspiratory level Pi1, and - in a second, subsequent cycle, raising the pressure from the expiratory level Pe1 ' to an inspiratory level Pi2 with a first specifiable pressure curve, and wherein the pressure Pi2 is higher than the pressure Pi1 and wherein the control unit has a memory for measurement values, and wherein the sensor is designed to measure and determine a breathing gas flow, and wherein the sensor is coupled with the analyzer, and wherein the analyzer is coupled with the pressure generator, and wherein the analyzer has an integrator function and is designed to determine a volume by integration of the breathing gas flow detected with the sensor, and the analyzer is designed to carry out the following method steps: - determining the resulting volume V1 in a first breathing cycle by integration of the breathing gas flow detected with the sensor in the first breathing cycle, and - storing the determined volume V1 in the memory, and - determining the volume V2 in the second breathing cycle by integration of the breathing gas flow detected with the sensor in the second breathing gas cycle, and wherein the pressure generator is further designed to carry out the following method steps: - lowering, during the second breathing cycle, the pressure with a second pressure curve from the pressure of the inspiratory level Pi2 to the pressure of the lower inspiratory level Pi1 only when the determined volume V2 has reached a predefined proportion of the stored volume V1, so that the further inspiration takes place in the second breathing cycle under the pressure Pi1. - a breathing gas source, - at least one sensor, - a control unit, wherein the control unit is connected to the at least one sensor for detecting a measurement value, - an apparatus (4, 5, 6) for connecting to the tube, and - an analyzer, - in a first, initial breathing cycle, specifying the pressure initially to an expiratory level Pe1 and then to a higher inspiratory level Pi1, and - in a second, subsequent cycle, raising the pressure from the expiratory level Pe1 ' to an inspiratory level Pi2 with a first specifiable pressure curve, and wherein the pressure Pi2 is higher than the pressure Pi1 and wherein the control unit has a memory for measurement values, and wherein the sensor is designed to measure and determine a breathing gas flow, and wherein the sensor is coupled with the analyzer, and wherein the analyzer is coupled with the pressure generator, and wherein the analyzer has an integrator function and is designed to determine a volume by integration of the breathing gas flow detected with the sensor, and the analyzer is designed to carry out the following method steps: - determining the resulting volume V1 in a first breathing cycle by integration of the breathing gas flow detected with the sensor in the first breathing cycle, and - storing the determined volume V1 in the memory, and - determining the resulting volume V1 in a first breathing cycle by integration of the breathing gas flow detected with the sensor in the first breathing cycle, and - storing the determined volume V1 in the memory, and - determining the volume V2 in the second breathing cycle by integration of the breathing gas flow detected with the sensor in the second breathing gas cycle, and wherein the pressure generator is further designed to carry out the following method steps: - lowering, during the second breathing cycle, the pressure with a second pressure curve from the pressure of the inspiratory level Pi2 to the pressure of the lower inspiratory level Pi1 only when the determined volume V2 has reached a predefined proportion of the stored volume V1, so that the further inspiration takes place in the second breathing cycle under the pressure Pi1. - lowering, during the second breathing cycle, the pressure with a second pressure curve from the pressure of the inspiratory level Pi2 to the pressure of the lower inspiratory level Pi1 only when the determined volume V2 has reached a predefined proportion of the stored volume V1, so that the further inspiration takes place in the second breathing cycle under the pressure Pi1.