Respirators are designed for different types of breathing gas sources depending on their field of use. Stationary respirators in hospitals are usually designed for being connected to a central gas supply system. If such a gas supply is not available, pressurized gas cylinders are used. Respirators that are designed mainly for mobile use make use of a blower, which draws in room air and feeds it directly to the patient while oxygen is possibly added.
A gas mixer for a respirator intended to be connected to pressurized gas sources is known from DE 24 55 751 B. Two pressurized gas sources are connected in the prior-art gas mixer to a storage tank via two feed lines and corresponding dispensing valves. The gas mixture is sent from the storage tank to the patient by means of a mixed gas line, which originates from the storage tank and likewise has a dispensing valve. To set a predetermined gas mixture, the dispensing valve is at first opened in one of the feed lines until the outlet pressure in the storage tank has increased to a first predetermined pressure value. The dispensing valve is then closed and the dispensing valve in the second feed line is opened until a second pressure value is reached. A defined volume of gas mixture is then removed via the mixed gas line until the outlet pressure in the storage tank has again become established. The prior-art gas mixture is suitable for use as long as a sufficient pressurized gas supply pressure can be made available.
DE 197 08 094 C2 discloses a respirator, in which ambient air is drawn in with a blower to supply the patient with gas and is compressed until the inspiration pressure necessary for respirating a patient becomes established. Oxygen can be added into a storage tank, which receives the ambient air drawn in, so that different oxygen concentrations can be set in the breathing gas. No provisions are made for operation with pressurized gases alone from a pressurized gas supply system in the case of this respirator.