Apparatus for determining an indicator representative for a fluid responsiveness parameter

An apparatus for determining an indicator representative of a fluid responsiveness during a blood pressure test, the apparatus comprising:

• a non-invasive pulse measurement device comprising a pressure cuff and a pressure sensor configured to detect a blood pressure from a patient and generate corresponding pulse signals over a time period corresponding to multiple respiratory cycles, and
• a processor operatively coupled to a memory storing instructions which, when executed by the processor, cause the processor to:
• (i) generate first data values corresponding to an envelope signal curve, the envelope signal curve representing amplitude variations of the pulse signals over time;
• (ii) generate second data values corresponding to respiratory pulse variation signals, the respiratory pulse variation signals determined as differences between the envelope signal curve and a first fitted envelope function;
• (iii) perform a fitting operation including:
• down-sampling first data values and/or second data values in accordance with a Shannon-Nyquist criterion;
• determining initial fit parameter values for a functional prototype based on characteristics of the down-sampled first data values and/or second data values;
• fitting the functional prototype, having the initial fit parameters, to the first data values to generate the first fitted envelope function;
• fitting the functional prototype to the second data values to generate a respiration-based fitted function;
• and
• (iv) determine the fluid responsiveness indicator based on at least one parameter of the first fitted envelope function and at least one parameter of the respiration-based fitted function.