A computer program for determining positive end expiratory pressure comprising instructions to cause a ventilation device to execute the steps comprising: controlling a ventilation control module for stepwise changing a PEEP value for ventilation of the ventilation device to a patient; controlling a physiological parameter monitoring module for monitoring at least one physiological parameter of the patient; controlling a calculation module for calculating a change in the at least one physiological parameter every time the PEEP value is changed; and determining a preferred PEEP value for ventilation to the patient according to the change in the at least one physiological parameter; characterized in that, the at least one physiological parameter comprises at least two of a driving pressure, a compliance, a dead space ratio and an oxygenation index, and determining a preferred PEEP value for ventilation to the patient according to the change in the at least one physiological parameter comprises: determining respective candidate PEEP values according to the changes in the respective at least two physiological parameters; and determining the preferred PEEP value for ventilation to the patient according to the respective candidate PEEP values; the candidate PEEP values comprise any one of the PEEP value corresponding to a minimum value of the driving pressure and the PEEP value corresponding to a maximum value of the compliance, and at least one of the PEEP value corresponding to a minimum value of the dead space ratio and the PEEP value corresponding to a maximum point of a change rate of the oxygenation index; wherein determining the preferred PEEP value for ventilation to the patient according to the respective candidate PEEP values comprises: determining the preferred PEEP value according to the PEEP value corresponding to the minimum value of the dead space ratio and any one of the PEEP value corresponding to the minimum value of the driving pressure and the PEEP value corresponding to the maximum value of the compliance; or, determining the preferred PEEP value according to the PEEP value corresponding to the maximum point of the change rate of the oxygenation index and any one of the PEEP value corresponding to the minimum value of the driving pressure and the PEEP value corresponding to the maximum value of the compliance; or, determining the preferred PEEP value according to the PEEP value corresponding to the minimum value of the dead space ratio, the PEEP value corresponding to the maximum point of the change rate of the oxygenation index and any one of the PEEP value corresponding to the minimum value of the driving pressure and the PEEP value corresponding to the maximum value of the compliance. controlling a ventilation control module for stepwise changing a PEEP value for ventilation of the ventilation device to a patient; controlling a physiological parameter monitoring module for monitoring at least one physiological parameter of the patient; controlling a calculation module for calculating a change in the at least one physiological parameter every time the PEEP value is changed; and determining a preferred PEEP value for ventilation to the patient according to the change in the at least one physiological parameter; characterized in that, the at least one physiological parameter comprises at least two of a driving pressure, a compliance, a dead space ratio and an oxygenation index, and determining a preferred PEEP value for ventilation to the patient according to the change in the at least one physiological parameter comprises: determining respective candidate PEEP values according to the changes in the respective at least two physiological parameters; and determining the preferred PEEP value for ventilation to the patient according to the respective candidate PEEP values; the candidate PEEP values comprise any one of the PEEP value corresponding to a minimum value of the driving pressure and the PEEP value corresponding to a maximum value of the compliance, and at least one of the PEEP value corresponding to a minimum value of the dead space ratio and the PEEP value corresponding to a maximum point of a change rate of the oxygenation index; wherein determining the preferred PEEP value for ventilation to the patient according to the respective candidate PEEP values comprises: determining the preferred PEEP value according to the PEEP value corresponding to the minimum value of the dead space ratio and any one of the PEEP value corresponding to the minimum value of the driving pressure and the PEEP value corresponding to the maximum value of the compliance; or, determining the preferred PEEP value according to the PEEP value corresponding to the maximum point of the change rate of the oxygenation index and any one of the PEEP value corresponding to the minimum value of the driving pressure and the PEEP value corresponding to the maximum value of the compliance; or, determining the preferred PEEP value according to the PEEP value corresponding to the minimum value of the dead space ratio, the PEEP value corresponding to the maximum point of the change rate of the oxygenation index and any one of the PEEP value corresponding to the minimum value of the driving pressure and the PEEP value corresponding to the maximum value of the compliance.