Method and apparatus for measuring blood volume, and vital sign monitor using the same

• US 20050222514A1
• Filed: 03/31/2005
• Published: 10/06/2005
• Est. Priority Date: 03/31/2004
• Status: Active Grant

• Current Assignee: Nihon Kohden Corporation
• Original Assignee: Nihon Kohden Corporation
• Inventors: Akiyama, Takeshi, Uchida, Keisuke, Sugo, Yoshihiro, Takeda, Sunao
• Granted Patent: US 7,402,138 B2
• Time in Patent Office: Days
• US Class Current: 600/526
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/0285 Measuring or recording phase velocity of blood waves
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence

Abstract

A first member is adapted to measure an electrocardiogram of a patient. A second member is adapted to measure a peripheral pulse wave of the patient. A first calculator calculates a pulse wave propagation time (PWTT) and a heart rate (HR) of the patient based on the electrocardiogram and the peripheral pulse wave. A second calculator calculates a cardiac output (CO) of the patient with an equation of CO=(αK·PWTT+βK)·HR, where α, β and K are coefficients inherent to the patient.

Claims

1. A method of measuring a blood volume, comprising steps of:

obtaining a pulse wave propagation time (PWTT) of a patient;

obtaining a heart rate (HR) of the patient;

obtaining a cardiac output (CO) of the patient with an equation of CO=(α

K·

PWTT+β

K)·

HR, where α

, β and

K are coefficients inherent to the patient.

2. The measuring method as set forth in claim 1, wherein at least one of the coefficients is calibrated with a value obtained by a blood pressure measurement.

3. The measuring method as set forth in claim 1, wherein the pulse wave propagation time is defined as a sum of a pre-ejection period of a heart of the patient, a time period during which a pulse wave generated in an aorta of the patient reaches a peripheral blood vessel where a plethysmogram is measured.

4. The measuring method as set forth in claim 1, further comprising a step of administrating a vasoconstrictor.

5. The measuring method as set forth in claim 4, wherein the vasoconstrictor is phynylephine.

6. An apparatus for measuring a blood volume, comprising:

a first member, adapted to measure an electrocardiogram of a patient;

a second member, adapted to measure a peripheral pulse wave of the patient;

a first calculator, which calculates a pulse wave propagation time (PWTT) and a heart rate (HR) of the patient based on the electrocardiogram and the peripheral pulse wave; and

a second calculator, which calculates a cardiac output (CO) of the patient with an equation of CO=(α

K·

PWTT+β

K)·

HR, where α

, β and

K are coefficients inherent to the patient.

7. The measuring apparatus as set forth in claim 6, further comprising a third member, adapted to measure a blood pressure of the patient,

wherein at least one of the coefficients is calibrated with a value obtained by the third member.

8. A vital sign monitor incorporating the measuring apparatus as set forth in claim 6, the vital sign monitor comprising a display showing at least the cardiac output.