A monitoring device for monitoring a blood path that extends from an access to a blood vessel (3) of a human subject through an extracorporeal blood processing apparatus (80) and back to the access to a blood vessel ( 3), in which the bloodstream comprises a blood collection device (2 ') and a blood return device (2 ") for connection to access to a blood vessel (3), and a pumping device (4 ) operable to pump blood through the bloodstream from the blood collection device (2 ') to the blood return device (2 "), said monitoring device comprising: an input for obtaining pressure data from a pressure sensor (6a) disposed upstream of the pumping device (4) in the bloodstream to detect pressure pulses in the blood pumped through the bloodstream； and a signal processor (8) connected to said input and which is configured to generate, based on the pressure data, a time-dependent monitoring signal comprising diaphonic pulses originating from one or more pulse generators in the extracorporeal blood processing apparatus (80) and they have spread in a direction downstream of the pumping device (4) through the blood return device (2 "), access to a blood vessel (3) and the blood collection device (2 ') to the pressure sensor (6a), characterized in that the signal processor (8) is further configured to: process the monitoring signal for the calculation of a parameter value indicating a presence or absence of diaphonic pulses, and detecting, at least partially based on the parameter value, an interruption of the bloodstream downstream of the pumping device (4).Un dispositivo de monitorización para monitorizar una vía sanguínea que se extiende desde un acceso a un vaso sanguíneo (3) de un sujeto humano a través de un aparato de procesamiento extracorpóreo de la sangre (80) y de vuelta al acceso a un vaso sanguíneo (3), en el que la vía sanguínea comprende un dispositivo de extracción de sangre (2') y un dispositivo de retorno de sangre (2") para conexión al acceso a un vaso sanguíneo
