Method of determining the stroke volume and the cardiac output of the human heart

Abstract

Method of determining the stroke volume of the human heart from the pulse-type blood-stream pressure signal derived from the aorta and consisting in each case of a systolic and a diastolic period. The method comprises calculating the flow q(t) from the pressure p(t) and integrating the flow over the systolic period, the aorta being regarded as a transmission line supplemented with a windkessel compliance and the pressure/volume relationship in the aorta as an arctangent relationship. The pressure represented by the pressure signal--for each stroke prior to the calculation of the flow--is linearized by the arctangent relationship, for fixed aorta length, or the aorta pressure/cross section, the values, associated with the final diastolic pressure, of the characteristic impedance of the transmission line and windkessel compliance being adhered to or is used without modification. The characteristic impedance of the transmission line and the windkessel compliance are continuously adapted to the pressure of the windkessel compliance for each stroke concerned. Additionally, to calculate the flow, the flow through the peripheral resistance is added.

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