Abstract: A method for determining a respiratory-gas content in a respiratory tract, which content is present in the respiratory tract of an at least partially artificially ventilated patient following a plurality of breaths performed with the involvement of a ventilation apparatus, wherein the plurality of breaths include at least one earlier number of breaths and at least one follow-up breath following the earlier number of breaths; wherein the earlier number of breaths include an earlier breath or a plurality of successive earlier breaths; wherein the method comprises quantitative detection of inspiratory and expiratory respiratory-gas flows by at least one respiratory-gas flow sensor and summation of detected inspiratory and expiratory flow values to form the respiratory-gas content in the respiratory tract; wherein a respiratory tract content starting value, at which the determination of the respiratory-gas content in the respiratory tract for the follow-up breath starts, depending on a difference in respiratory-g