Process for changing the concentration in an anesthesia apparatus

A process for changing the concentration in an anesthesia apparatus with a breathing circuit, the process comprising the steps of:

• providing the breathing circuit with an inspiration branch and an expiration branch, with a fresh gas metering unit connected to the breathing circuit and a pressure sensor in the breathing circuit, with a volume displacement device having an expansible chamber connected in fluid communication with the inspiration branch for receiving gas from the inspiration branch and displacing gas to the inspiration branch and a Positive End Expiratory Pressure (PEEP)/maximum pressure (PMAX) valve in the expiration branch;
• connecting an evaluating and control unit to the fresh gas metering unit, the pressure sensor, the volume displacement device and the PEEP/PMAX valve;
• setting the fresh gas supply from the fresh gas metering unit at the maximum amount that can be metered, and controlling the volume displacement device with the evaluating and control unit to receive gas from the inspiration line at the same time at a speed that an amount of fresh gas fed by the fresh gas metering unit is taken up by the volume displacement device;
• and
• moving the volume displacement device completely forward while not exceeding a pressure preset on the PEEP/PMAX valve in the breathing circuit.

An anesthesia apparatus, comprising:

• a breathing circuit with an inspiration branch and an expiration branch;
• a fresh gas metering unit connected to said breathing circuit;
• a pressure sensor in the breathing circuit;
• a volume displacement device having an expansible chamber connected in fluid communication with the inspiration branch for receiving gas from the inspiration branch and displacing gas to the inspiration branch;
• a positive end expiratory pressure (PEEP)/maximum pressure (PMAX) valve in the expiration branch;
• an evaluating and control unit connected to said gas metering unit, connected to said pressure sensor, connected to said volume displacement device and connected to said PEEP/PMAX valve, said evaluating and control unit controlling said volume displacement device and said gas supply to:
• completely return the volume displacement device to a start position while increasing the gas supply from the gas metering unit via the evaluating and control unit such that the volume displacement device is completely filled with the gas fed in or set the gas supply from the gas metering unit at the maximum amount that can be metered, and control the volume displacement device to receive gas from the inspiration branch at a rate that the gas fed by the gas metering unit is taken up by the volume displacement device;
• and
• move the volume displacement device to displace the gas completely while not exceeding a set pressure preset on the PEEP/PMAX valve in the breathing circuit.