A ventilator includes electronic control circuitry configured to control a supply of breathing gas for a plurality of respiratory cycles, measure a volume received by the patient in each of the plurality of respiratory cycles, and determine, for each cycle of the plurality of respiratory cycles, a cycle score corresponding to a deviation between the volume of the cycle and a predetermined target volume. The determined cycle score can be selected from a predetermined number of cycle scores that span positive and negative numbers based on the deviation. A pressure step value can be determined based on a plurality of cycle scores corresponding to the plurality of respiratory cycles, and a current pressure of the breathing gas is adjusted by an amount corresponding to the determined pressure step value. The pressure step value may be generated by dividing a sum of the plurality of cycle scores by a sample size.