A small unit dedicated to the measurement of cardiac output (the volume of blood pumped by the heart per minute) obtained through a pressure transducer/catheter introduced into a blood vessel. It is designed to operate as part of a patient monitoring system enhancing the function of this system (the parent device). The module automatically plugs into the parent device when the user places it into a standardized slot in the parent device or a connected module rack. The parent device operates as a mainframe computer displaying the cardiac output parameter/information measured and provided by this module.