APPARATUS FOR DETERMINING AN INDICATOR REPRESENTATIVE FOR A FLUID RESPONSIVENESS PARAMETER

The invention relates to an apparatus for determining an indicator that is representative of a physiological parameter like a fluid responsiveness parameter. The indicator is determined based on a fitting of a functional prototype to data values (sO) determined from pulse signals measured over subsequent respiratory cycles. The fitting process is accelerated by a) reducing the number of data values before fitting, b) determining an initial fit parameter value for the functional prototype based on characteristics of the data values and/or a fit parameter value known from a previous fitting, and/or c) carrying out the fitting in several stages, wherein the number of data values used is increased from stage to stage and a fit parameter value determined in a previous stage is used as initial fit parameter value in a current stage. This allows for a faster determination of, for instance, a fluid responsiveness parameter.