Patent ID: 6171242
Filing Date: 2001-01-09
Classification: A61B

Abstract:
A device for measuring a physiological state in an organism having an arterial system extending from a center portion of the organism's body to a periphery thereof, said device comprising:measuring means for measuring the physiological state on the basis of a pulse wave detected at a periphery of the arterial system; andanalysis means for calculating circulatory state parameters, including viscoelasticity of an aorta of the arterial system, based on the measured physiological state, to show a circulatory state of the arterial system from the center to the periphery, blood vessel resistance at the center of the arterial system due to blood viscosity, blood inertia at the center of the arterial system, blood vessel resistance at the periphery of the arterial system due to blood viscosity, and blood vessel viscoelasticity at the periphery of the arterial system,wherein the circulatory state of the arterial system is modeled using a lumped five-parameter model and the circulatory state parameters are determined on the basis of the model, wherein the model includes the following circuit elements:a diode corresponding to the aortic valve;a first resistor corresponding to blood vessel resistance at the center of the arterial system due to blood viscosity;an inductor corresponding to blood inertia at the center of the arterial system;a first capacitor corresponding to viscoelasticity of the aorta;a second resistor corresponding to blood vessel resistance at the periphery of the arterial system;a second capacitor corresponding to blood vessel viscoelasticity at the periphery of the arterial system;a pair of input terminals, one of which is defined by a first node that includes one end of the diode and the other of which is defined by a second node that includes one end of the first capacitor; anda pair of output terminals, one of which is defined by a third node that includes one end of the inductor, one end of the second capacitor and one end of the second resistor and a second of which is defined by the second node.