A computerized method for monitoring cardiac output of a subject by a processor executing the method, the method comprising the steps of: determining first values of cardiac output of the subject for a first period of time using respective different cardiac output measurement methods having respective first measurement errors; and combining the determined first values of cardiac output to determine a second value of cardiac output of the subject for the first period of time, such that the second value of cardiac output has a second measurement error that is less than any of the first measurement errors; and at least one of storing, outputting, and displaying data representing the determined second value of cardiac output of the subject.