Abstract: In a method and arrangement for evaluating effective flow resistance of a patient breathing circuit connected to a mechanical breathing assist device, a flow controller is operable to temporarily introduce an occlusion to the gas flow within the breathing circuit at a time after the end of an inspiration phase of a breathing cycle provided by the breathing assist device. A sensor unit 34 has a flow sensor for measuring gas flow within the circuit and a pressure sensor for measuring gas pressures within the circuit. An evaluating unit receives measurements from the sensor unit, to determine for a measured gas flow a value of a pressure drop within the breathing circuit after the introduction of the occlusion, and establishes a relationship between the calculated pressure drop and the measured gas flow, such as based on the known Blasius formula.

Abstract: A valve for regulating a gas flow has a valve seat and a valve body, movable against the valve seat. The valve achieves high accuracy, a wide dynamic range and high operating reliability by causing the valve body substantially only to move axially against the valve seat and by using a stepper motor to actuate the valve body's axial movement against the valve seat with a non-linearly threaded engagement between the stepper motor and valve body so that the valve body performs continuous, non-linear, axial movement against the valve seat.