Process for changing the concentration in an anesthesia apparatus

The present invention pertains to a process for changing the concentration in an anesthesia apparatus with a breathing circuit with an inspiration branch and an expiration branch, with a fresh gas metering unit and a pressure sensor in the breathing circuit, with a volume displacement means in the inspiration branch and a PEEP/P valve in the expiration branch, wherein the fresh gas metering unit, the pressure sensor, the volume displacement means and the PEEP/P valve are connected to an evaluating and control unit. A process, system and apparatus for changing the concentration in an anesthesia apparatus with a fresh gas metering unit () and a pressure sensor () in the breathing circuit, with a volume displacement device () in the inspiration branch and a PEEP/Pvalve () in the expiration branch. The fresh gas metering unit (), the pressure sensor (), the volume displacement unit () and the PEEP/Pvalve () are connected to an evaluating and control unit (). To bring about a rapid change in the concentration of the anesthetic or fresh gas supplied in the breathing circuit without additional design effort on the anesthesia apparatus the volume displacement device () is rinsed, either under the control of the fresh gas supply or under the control of the speed at which the volume displacement device () is returned. The rinsing takes place simultaneously with the regular respiration operation of the anesthesia apparatus, which may take place in a volume-controlled or pressure-controlled manner.