Device for measuring physiological state

• US 6,171,242 B1
• Filed: 07/24/1997
• Issued: 01/09/2001
• Est. Priority Date: 11/01/1995
• Status: Expired due to Term

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Amano, Kazuhiko, Ishiyama, Hitoshi, Uebaba, Kazuo
• Primary Examiner(s): O'Connor, Cary
• Assistant Examiner(s): ASTORINO, MICHAEL C
• Application Number:
  US08/860,579
• Time in Patent Office: 1,265 Days
• Field of Search: 600/300-301, 600/481-485, 600/500-503, 128/897-899, 128/920-925, 128/900
• US Class Current: 600/423
• CPC Class Codes: A61B 5/02 Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02108 from analysis of pulse wave characteristics
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61B 5/681 Wristwatch-type devices

Abstract

A non-invasive device for evaluating circulatory state parameters, and specifically, a pulsewave analysis device capable of evaluation by separating blood vessel compliance and blood vessel resistance into central and peripheral components of the arterial system is provided. Microcomputer 4 detects the waveform at a test subject'"'"'s radius artery via pulsewave detector 1, and uptakes the stroke volume in the test subject which is measured by a stroke-volume measurer. Next, based on the measured stroke volume, microcomputer 4 adjusts the values of each element in a lumped five parameter model made up of an electrical circuit which models the arterial system from the center to the periphery of the body, so that the response waveform obtained when an electric signal corresponding to the pressure waveform at the proximal portion of the aorta in a test subject is provided to the electric circuit coincides with the waveform at the radius artery. Microcomputer 4 then outputs the thus-obtained values of each element as circulatory state parameters. In addition, microcomputer 4 calculates the diastolic pressure value, systolic pressure value and pulse waveform at the proximal portion of the aorta from the values of each element, and outputs the calculated result to output device 6.

Claims

1. 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; and

analysis 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; and

a 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.

2. A device according to claim 1, wherein the physiological state is represented by the pulse wave detected at the periphery of the arterial system, and the analysis means determines values of each of the circuit elements in the lumped five parameter model so that an output electric signal corresponding to a waveform of the pulse wave is obtained from the output terminals when an input electric signal corresponding to pressure in a left cardiac ventricle in the organism'"'"'s body is applied to the input terminals.

3. A device according to claim 2, wherein the input electric signal e is defined approximately by a sinusoidal wave as follows:

4. 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;

analysis 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 and

blood pressure calculating means for calculating a pressure waveform at the aorta based on the calculated circulatory state parameters

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 viscoelasticitv 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; and

a 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; and

wherein a voltage waveform across the first capacitor corresponds to the pressure waveform at the aorta.

5. A device according to claim 4, wherein the physiological state is represented by the pulse wave detected at the periphery of the arterial system, and wherein said device further comprises blood calculating means which determines values of each of the circuit elements in the lumped five-parameter model so that an output electric signal corresponding to a waveform of the pulse wave is obtained from the output terminals when an input electric signal corresponding to pressure in a left cardiac ventricle in the organism'"'"'s body is applied to the input terminals.

6. 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;

analysis 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 pressure calculating means for calculating a pressure waveform at the aorta based on the calculated circulatory state parameters; and

a stroke-volume detector which detects a stroke volume which is the amount of blood that circulates through the organism'"'"'s body during one stroke, and a stroke-volume measurer which measures the stoke volume on the basis of the detected stroke volume, and blood calculating means which adjusts a value of the circulatory state parameters so that a calculated value of the stroke volume obtained from the pressure waveform at the aorta and an actual measured value of the stroke volume measured by the stroke-volume measurer are equivalent.

7. A device for measuring a physioloical 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;

analysis 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 pressure calculating means for calculating a pressure waveform at the aorta based on the calculated circulatory state parameters; and

a workload calculating means for calculating workload on the organism'"'"'s heart based on the pressure waveform at the aorta.

8. 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;

analysis 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; and

blood pressure calculating means for calculating a pressure waveform at the aorta based on the calculated circulatory state parameters;

wherein the physiological state is represented by the pulse wave detected at the periphery, and wherein said device further comprises distortion calculating means for calculating any distortion in the pulse wave from the corresponding waveform, and blood calculating means which determines the circulatory state parameters based on the correlation between the circulatory state parameters and the distortion in the pulse wave.

9. 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;

analysis 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; and

blood pressure calculating means for calculating a pressure waveform at the aorta based on the calculated circulatory state parameters;

wherein the measuring means measures a pressure waveform of the pulse at the periphery of the arterial system, and wherein said device further comprises comparing means for comparing the pressure waveform of the pulse at the periphery of the arterial system and the pressure waveform at the aorta, and diagnosing means for carrying out a diagnosis based on comparison results obtained by the comparing means.

10. A device according to claim 9, wherein the measuring means measures a waveform at a radius artery of the organism'"'"'s body, the comparing means determines differences in maximum value, minimum value and average value between the waveform at the radius artery and the pressure waveform at the aorta, and the diagnosing means issues a warning when the difference obtained is within a specified range.

11. 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 at the periphery of the arterial system;

blood pressure calculating means for determining circulatory state parameters, which are indicative of the circulatory state of the arterial system, based on the measured physiological state, and calculating a pressure waveform at an aorta of the arterial system based on the determined circulatory state parameters; and

ventricle state calculating means for calculating a ventricular contraction phase, a ventricular expansion phase, and a time during which pressure in a ventricle of the arterial system rises.