Abstract: A respiratory flow sensor is provided with two identical or substantially identical first and second wires arranged at spaced locations from one another in a housing through which the respiratory flow flows. The first and second wires can be heated by a respective associated power source. An air resistance body is arranged in the vicinity of the second wire. A third wire is arranged in the housing at a spaced location from the first and second wires and is used to determine the temperature of the respiratory flow via an associated measuring device for the temperature-dependent electric resistor. A central control and evaluating unit is connected to the power sources and to the measuring device and compensates a temperature change of the respiratory flow. The change is detected with the third wire by a change in the heating current flowing through the first and second wires, so that these wires have an operating temperature that is above the temperature of the respiratory flow by a defined amount.