A device is arranged to detect a configuration of withdrawal and return devices (1, 14, 111, 112, 211, 212, 702, 703, 802, 803) coupling an extracorporeal blood flow circuit (20) to a cardiovascular system of a subject. The device comprises a signal processor (29), which is configured to receive a primary measurement signal obtained by a primary pressure sensor (4a, 4b, 4c) in the extracorporeal blood flow circuit (20). The device is further configured to process the primary measurement signal for extraction of primary pressure data originating from a subject pulse generator (3′) in the cardiovascular system or extracorporeal blood flow circuit (20), the primary pressure data comprising at least a part of a first pulse from the subject pulse generator (3′). The device is also configured to calculate a parameter value from the primary pressure data and to determine the configuration based at least partly on the parameter value.
