The invention relates to a cardiac monitoring device (1) for a patient, in particular a patient undergoing cardiopulmonary arrest (CPR) during cardiopulmonary resuscitation (CPR), comprising means for measuring activity. cardiac (4, 8, 9) of the patient, in particular several electrodes (8, 9) placed on the patient's body, at least one graphical user interface (2), means for measuring CO content <；sub>； 2 <；/sub>； (3), like a capnometer, for measuring the CO <；sub>； 2 <；/sub>； concentration produced by said patient and providing signals for measuring the CO content <；sub>； 2 <；/sub>； signal processing means (5) configured to process the CO content measurement signals <；sub>； 2 <；/sub>；, in particular a microprocessor, and storage means (15) for recording the CO values <；sub >； 2 <；/sub>； processed. The signal processing means (5) are configured to select a maximum value (Vmax) of CO content <；sub>； 2 <；/sub>； from among a plurality of CO content values <；sub>； 2 <；/sub>； measured during a given period of time (dt), and recorded in the storage means (15). Several successive maximum values (Vmax) of CO <；sub>； 2 <；/sub>； content are used to calculate average CO <；sub>； 2 <；/sub>； contents over a sliding time window. These mean values (Vmoy) of CO content <；sub>； 2 <；/sub>； are displayed on the graphical user interface (2), for example in the form of a graph, such as a trend line.L'invention concerne un appareil de monitorage (1) cardiaque d'un patient, en particulier d'un patient en arrêt cardio-respiratoire (ACR) pendant une réanimation cardio-pulmonaire (RCP), comprenant des moyens de mesure de l'activité cardiaque (4, 8, 9) du patient, notamment plusieurs électrodes (8, 9) venant se placer sur le corps du patient, au moins une interface graphique utilisateur (2), des moyens de mesure de teneur en CO2 (3), tel un capnomètre, pour opérer des mesures de concentration en CO2 produit par led
