A filtering device receives a signal from a pressure sensor in an extracorporeal fluid circuit connected to a subject and processes the signal to separate physiological pulses, e.g. from the subjects heart, from interference pulses, e.g. from a pump in the fluid circuit. The device repeatedly (iteratively) processes a signal segment by alternately subtracting (S3) a template signal from the signal segment, and applying a refinement processing (S6) to the resulting difference signal to generate a new template signal. By proper selection (S2) of the initial template signal, consecutive difference signals will alternately approximate the sequence of interference pulses in the signal segment and the sequence of physiological pulses in the signal segment. The refinement processing (S6) aims at alternately cleaning up unwanted residuals from interference pulses and physiological pulses, respectively, in the respective difference signal, so as to improve the accuracy of the template signal between the subtractions.
