Method of determining an indicator that is representative for a patient's volume responsiveness, comprising the following steps: (i) measuring a sequence of pulse signals of a patient over a time period corresponding to a plurality of subsequent respiratory cycles of the patient, wherein the sequence of measured pulse signals is detected by an oscillometric non-invasive pulse measurement method using a pressure cuff, wherein the pressure applied in the pressure cuff is continuously increased or decreased in the course of a measurement period; (ii) representing the measured pulse signals as pulse signals oscillating around an average value thereof, and determining an envelope(signal)-curve for the pulse signals; (iii) determining a fit(envelope(signal))-function based on the previously determined envelope(signal)-curve, wherein the fit(envelope(signal))-function is determined based on a predetermined first functional prototype, and wherein the fit(envelope(signal))-function represents an idealised curve progression of the envelope(signal)-curve over the plurality of respiratory cycles without comprising pulse variations caused by ventilation or respiration induced heart-lung interaction; (iv) determining respiratory pulse variation signals corresponding to the pulse variations caused by ventilation or respiration induced heart-lung interaction over the plurality of respiratory cycles, wherein the determined respiratory pulse variation signals correspond to a difference between the envelope(signal)-curve and the fit(envelope(signal))-function; (v) determining an envelope(respiration)-curve for the previously determined respiratory pulse variation signals; (vi) determining a fit(envelope(respiration))-function based on the previously determined envelope(respiration)-curve, wherein the fit(envelope(respiration))-function is determined based on a predetermined second functional prototype, and wherein the fit(envelope(respiration))-function represents an idealised curve progression of the envelope(respiration)-curve over the plurality of respiratory cycles; (vii) determining the indicator that is representative for the patient's volume responsiveness based on the fit(envelope(signal))-function and the fit(envelope(respiration))-function. (i) measuring a sequence of pulse signals of a patient over a time period corresponding to a plurality of subsequent respiratory cycles of the patient, wherein the sequence of measured pulse signals is detected by an oscillometric non-invasive pulse measurement method using a pressure cuff, wherein the pressure applied in the pressure cuff is continuously increased or decreased in the course of a measurement period; (ii) representing the measured pulse signals as pulse signals oscillating around an average value thereof, and determining an envelope(signal)-curve for the pulse signals; (iii) determining a fit(envelope(signal))-function based on the previously determined envelope(signal)-curve, wherein the fit(envelope(signal))-function is determined based on a predetermined first functional prototype, and wherein the fit(envelope(signal))-function represents an idealised curve progression of the envelope(signal)-curve over the plurality of respiratory cycles without comprising pulse variations caused by ventilation or respiration induced heart-lung interaction; (iv) determining respiratory pulse variation signals corresponding to the pulse variations caused by ventilation or respiration induced heart-lung interaction over the plurality of respiratory cycles, wherein the determined respiratory pulse variation signals correspond to a difference between the envelope(signal)-curve and the fit(envelope(signal))-function; (v) determining an envelope(respiration)-curve for the previously determined respiratory pulse variation signals; (vi) determining a fit(envelope(respiration))-function based on the previously determined envelope(respiration)-curve, wherein the fit(envelope(respiration))-function is determined based on a predetermined second functional prototype, and wherein the fit(envelope(respiration))-function represents an idealised curve progression of the envelope(respiration)-curve over the plurality of respiratory cycles; (vii) determining the indicator that is representative for the patient's volume responsiveness based on the fit(envelope(signal))-function and the fit(envelope(respiration))-function.