Medical treatment apparatus with overpressure in the port

A medical treatment apparatus comprising:

• at least one port for establishing fluid communication between at least one fluid line of the medical treatment apparatus assigned to an interior of the medical treatment apparatus and a connector of a fluid line of a disposable assigned to an exterior of the medical treatment apparatus, wherein the at least one port comprises:
• a first lumen fluidly connected to a fluid line of the at least one fluid line, the first lumen having a first end opening;
• and
• a second lumen having a second end opening, wherein the first lumen is located further inside the at least one port than the second lumen in a radial and axial direction;
• a sealing device for sealing an interior of the port from the exterior of the treatment apparatus;
• a compressed-air source for introducing air or sterile-air into the port along at least one sterile-air line;
• and
• a control device programmed to cause the compressed-air source to build-up and maintain a predetermined minimum overpressure in the sterile-air line, in the compressed-air source and/or inside the port.