An Infusion device (1) for administering a medical fluid to a patient (P), comprises: a receptacle (12) for receiving a syringe (2) having a tube (20) containing a medical fluid and a piston (21) movable with respect to the tube (20)； a pusher device (11) for acting onto the piston (21) for pumping the medical fluid from the tube (20) towards a patient (P) at a set flow rate； a sensor device (14) for measuring a force acting in between the pusher device (11) and the piston (21) of the syringe (2)； and a processor device (15) for deriving, from the force measured by the sensor device (14), a pressure value indicative of the pressure in the delivery line (3), wherein the processor device (15) is constituted to compare the pressure value to a threshold value (Pthres) for determining whether an occlusion (O) in the delivery line (3) is present. Herein, the processor device (15) is constituted to determine the threshold value (Pthres) from a first threshold value candidate computed based on a desired time between the time (t0) of an occurrence of an occlusion (O) in the delivery line (3) and the time (t1) at which the pressure value exceeds the threshold value (Pthres), and a second threshold value candidate based on a force error estimate of a possible deviation between an expected frictional force and a true frictional force occurring when moving the piston (21) relative to the tube (20).Un dispositif de perfusion (1) destiné à administrer un fluide médical à un patient (P) comprend : un réceptacle (12) pour recevoir une seringue (2) comportant un tube (20) contenant un fluide médical et un piston (21) mobile par rapport au tube (20)； un dispositif poussoir (11) destiné à agir sur le piston (21) pour pomper le fluide médical du tube (20) vers un patient (P) à un débit défini； un dispositif capteur (14) pour mesurer une force agissant entre le dispositif poussoir (11) et le piston (21) de la seringue (2)； et un dispositif processeur (15) pour dériver, à partir de la for
