The invention relates to an apparatus for monitoring of physiological parameters at mechanical ventilation. The objective is to identify beneficial and injurious effects of ventilator resetting within few breaths while the operator remains at bedside. Monitored parameters include e.g. tidal volume, airway pressures, end tidal CO2, haemodynamics and volume of CO2 eliminated per minute, VMINCO2. Data sets of each signal before and after resetting are statistically analyzed to reduce noise and to allow accurate presentation of changes in conjunction with resetting. The quotient between VMINCO2 after and before resetting is used to illustrate the effect on alveolar ventilation and thereby effects on arterial partial pressure of CO2. The course of VMINCO2 after resetting is analyzed to get an accurate value of VMINCO2 after resetting. The invention can be used at different modes of ventilation because of noise reducing strategies, which are of particular importance at supported and irregular ventilation.
