Method and apparatus for measuring blood volume

• US 9,591,976 B2
• Filed: 10/22/2013
• Issued: 03/14/2017
• Est. Priority Date: 10/30/2012
• Status: Active Grant

• Current Assignee: Nihon Kohden Corporation
• Original Assignee: Nihon Kohden Corporation
• Inventors: Terao, Mami, Sugo, Yoshihiro, Sakai, Tomoyuki
• Primary Examiner(s): Cheng, Jacqueline
• Assistant Examiner(s): PREMRAJ, ANGELINE L
• Application Number:
  US14/059,579
• Publication Number:
  US 20140121544A1
• Time in Patent Office: 1,239 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/02108 from analysis of pulse wave characteristics
• CPC Class Codes: A61B 5/02125 of pulse wave propagation time
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• 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 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00

Abstract

Method for measuring a blood volume is provided. At least two types of respiratory variation data; for instance, data pertinent to respiratory variations in stroke volume (SVV) data, data pertinent to respiratory variations in an amplitude of a pulse wave (PAV), a pulse wave transit time (PWTT) in a respiratory cycle, and a heart rate (HR) in a predetermined time, are measured, and patient'"'"'s inherent coefficients α, β, and K are calculated, whereby a cardiac output can be determined by an equation CO=K (α*PWTT+β)*HR.

Claims

1. A blood volume measurement method for calculating a cardiac output (CO) from a pulse wave transit time, the method comprising the steps of:

measuring respiratory variations of at least two types of parameters;

measuring a pulse wave transit time (PWTT) in a respiratory cycle;

measuring a heart rate (HR) in a predetermined time; and

calculating and outputting, by a computer, a cardiac output (CO) by use of the respiratory variations of at least the two types of parameters, the pulse wave transit time, and the heart rate; and

wherein patient'"'"'s inherent coefficients α

, β

, and K are calculated by use of the respiratory variations of at least the two types of parameters and the pulse wave transit time, and the cardiac output is determined by an equation

CO=K(α

*PWTT+β

)*HR; and

wherein the patient'"'"'s inherent coefficient α

is determined by an equation

α

=−

(PAV*PP1)/(PAV*(PWTTavg−

PWTT1)+PWTTmax−

PWTTmin), where

PAV is an amplitude of a pulse wave;

PP1 is actually measured pulse pressure;

PWTTavg is an average pulse wave transit time in a respiratory cycle;

PWTT1 is an actually measured pulse wave transit time;

PWTTmax is a maximum value of pulse wave transit time in the respiratory cycle; and

PWTTmin is a minimum value of pulse wave transit time in the respiratory cycle.

2. The blood volume measurement method according to claim 1, wherein the respiratory variations of at least the two types of parameters comprise respiratory variations in stroke volume (SVV) and respiratory variations in an amplitude of a pulse wave (PAV).

3. The blood volume measurement method according to claim 1, wherein the respiratory variations of at least the two types of parameters comprise respiratory variations in stroke volume (SVV) and respiratory variations in pulse pressure (PPV).

4. A blood volume measurement apparatus that calculates a cardiac output (CO) from a pulse wave transit time, comprising:

a processor configured to;

determine respiratory variations of at least two types of parameters;

detect a pulse wave transit time (PWTT) in a respiratory cycle;

calculate a heart rate (HR) in a predetermined time; and

calculate and output a cardiac output (CO) with use of the respiratory variations of at least the two types of parameters, the pulse wave transit time, and the heart rate; and

wherein patient'"'"'s inherent coefficients α

, β

, and K are calculated by use of the respiratory variations of at least the two types of parameters and the pulse wave transit time, and the cardiac output is determined by an equation

CO=K(α

*PWTT+β

)*HR; and

wherein the patient'"'"'s inherent coefficient α

is determined by an equation

α

=−

(PAV*PP1)/(PAV*(PWTTavg−

PWTT1)+PWTTmax−

PWTTmin), where

PAV is an amplitude of a pulse wave;

PP1 is actually measured pulse pressure;

PWTTavg is an average pulse wave transit time in a respiratory cycle;

PWTT1 is an actually measured pulse wave transit time;

PWTTmax is a maximum value of pulse wave transit time in the respiratory cycle; and

PWTTmin is a minimum value of pulse wave transit time in the respiratory cycle.

5. The blood volume measurement method according to claim 4, wherein the respiratory variations of at least the two types of parameters comprise respiratory variations in stroke volume (SVV) and respiratory variations in an amplitude of a pulse wave (PAV).

6. The blood volume measurement method according to claim 4, wherein the respiratory variations of at least the two types of parameters comprise respiratory variations in stroke volume (SVV) and respiratory variations in pulse pressure (PPV).