Patent ID: 8257273
Filing Date: 2012-09-04
Classification: A61B

Abstract:
1. Method of determining at least one hemodynamic parameter of a living being, which comprises: introducing via an extracardial effect unit into the cardiovascular system of the living being, by means of a defined effect on venous blood, a disruption that can be characterized by means of a disruption function, acquiring a measurement signal produced by a sensor as a function of a physical variable of arterial blood, which characterizes a system response of the cardiovascular system brought about by the disruption function, and calculating via an evaluation unit the hemodynamic parameter from a dilution curve y that corresponds to the time progression of the measurement signal and, in this connection, taking into consideration at least one of a possible short-circuit current from the right to the left half of the heart (RL shunt) and a possible short-circuit current from the left to the right half of the heart (LR shunt) of the living being, wherein a model for the cardiovascular and pulmonary circulation system of the living being is used as a basis for calculating the hemodynamic parameter, wherein the model comprises a serial circuit of several system elements and at least one system element connected in parallel for taking the short-circuit current into consideration and a program technology set-up of the evaluation unit comprises calculation operations that can be derived from a model function for a system response that corresponds to this model, wherein the model function comprises a mathematical convolution of terms that incorporate the system elements connected in series and the disruption function, wherein the terms each have a respective characteristic time as a model parameter, and wherein the serial circuit of several system elements is modeled as a serial circuit comprising: a first ideally mixed volume for the right atrium RA of the living being, a second ideally mixed volume for the right ventricle RV of the living being, a third ideally mixed volume for the totality of pulmonary blood volume PBV and extravasal thermal volume ETV of the living being and a delay element, and a fourth ideally mixed volume for the totality of the left atrium and the left ventricle LV of the living being assumed as system elements of the serial circuit.