A computer system for medical monitoring of a patient using one or more physiological models (MOD1, MOD2) implemented on the computer system, the system being arranged for: - receiving first data indicative of characteristics in the inspired gas of the patient, - receiving second data indicative of characteristics in the respiratory feedback in expired gas of the patient, and - receiving third data indicative of the acid/base status and oxygenation level in the blood of the patient, the computer system being arranged for: i. performing a mathematical physiological modelling of the patient using said first, second and third data as a function of time, wherein the one or more physiological models (MOD1, MOD2) is/are capable of modelling the patient over time by outputting a plurality of corresponding physiological parameters derivable from said first, said second and said third data describing the functioning of at least two organ systems and/or physiological systems simultaneously, ii. performing a monitoring process wherein - if one, or more, of the physiological parameters describing the functioning of at least two organ systems and/or physiological systems have a deviation (DEV_P) compared to a related threshold level, the computer system outputs: • an indication of the one or more organ systems, and/or one or more physiological systems causing said deviation; and • optionally, an alarm signal, thereby indicating an underlying cause for a change in the first, second and third data or an underlying physiological change of the patient. - receiving first data indicative of characteristics in the inspired gas of the patient, - receiving second data indicative of characteristics in the respiratory feedback in expired gas of the patient, and - receiving third data indicative of the acid/base status and oxygenation level in the blood of the patient, i. performing a mathematical physiological modelling of the patient using said first, second and third data as a function of time, wherein the one or more physiological models (MOD1, MOD2) is/are capable of modelling the patient over time by outputting a plurality of corresponding physiological parameters derivable from said first, said second and said third data describing the functioning of at least two organ systems and/or physiological systems simultaneously, ii. performing a monitoring process wherein - if one, or more, of the physiological parameters describing the functioning of at least two organ systems and/or physiological systems have a deviation (DEV_P) compared to a related threshold level, the computer system outputs: • an indication of the one or more organ systems, and/or one or more physiological systems causing said deviation; and • optionally, an alarm signal, - if one, or more, of the physiological parameters describing the functioning of at least two organ systems and/or physiological systems have a deviation (DEV_P) compared to a related threshold level, the computer system outputs: • an indication of the one or more organ systems, and/or one or more physiological systems causing said deviation; and • optionally, an alarm signal, • an indication of the one or more organ systems, and/or one or more physiological systems causing said deviation; and • optionally, an alarm signal,