CARDIAC SIGNAL PROCESSING APPARATUS AND CARDIAC SIGNAL PROCESSING METHOD

• US 20130197377A1
• Filed: 12/28/2012
• Published: 08/01/2013
• Est. Priority Date: 01/26/2012
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Jun-Ichi Takada, Satoshi Suzuki, Takahiko Kishi, Tomoyoshi Yasue
• Inventors: KISHI, Takahiko, TAKADA, Jun-ichi, SUZUKI, Satoshi, YASUE, Tomoyoshi
• Granted Patent: US 8,597,196 B2
• Time in Patent Office: Days
• US Class Current: 600/508
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/0507 using microwaves or terahertz waves
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence

Abstract

A cardiac signal processing apparatus includes: a unit for acquiring, from a heartbeat sensor, cardiac signals relating to heartbeats of a subject; a low-pass filter for allowing passage of those cardiac signals having a first predetermined frequency or lower, among the cardiac signals; higher harmonic noise acquisition unit for acquiring harmonic signals of low-frequency noise by performing high frequency extrapolation on the signals output from the low-pass filter; a high-pass filter for allowing passage of those cardiac signals having a second predetermined frequency or higher, among the cardiac signals; and higher harmonic noise removal unit for removing the harmonic signals of low-frequency noise from the signals output from the high-pass filter. It is thus made possible to remove noise from the cardiac signals and to obtain desirable heartbeat detection characteristics.

Claims

1. A cardiac signal processing apparatus comprising:

a cardiac signal acquisition unit configured to acquire cardiac signals relating to heartbeats of a subject;

a low-pass filter configured to allow passage of those cardiac signals having a first predetermined frequency or lower, among the cardiac signals;

a higher harmonic noise acquisition unit configured to acquire harmonic signals of low-frequency noise by performing high frequency extrapolation on the signals output from the low-pass filter unit;

a high-pass filter configured to allow passage of those cardiac signals having a second predetermined frequency or higher, among the cardiac signals; and

a higher harmonic noise removal unit configured to remove the harmonic signals of low-frequency noise from the signals output from the high-pass filter.

2. The cardiac signal processing apparatus according to claim 1, wherein the cardiac signal is a signal obtained by measurement based on displacement on a body surface around the chest or displacement in the body of the subject.

3. The cardiac signal processing apparatus according to claim 1, wherein the first and second predetermined frequencies are lower than a cardiac fundamental frequency and higher than a respiratory fundamental frequency.

4. The cardiac signal processing apparatus according to claim 1, wherein:

the first predetermined frequency is lower than a cardiac fundamental frequency and higher than a respiratory fundamental frequency; and

the second predetermined frequency is higher than the cardiac fundamental frequency.

5. The cardiac signal processing apparatus according to claim 1, wherein the higher harmonic noise removal unit is an adaptive filter which uses the harmonic signal of low-frequency noise as a reference signal.

6. The cardiac signal processing apparatus according to claim 1, further comprising:

a sensor configured to acquire an extraneous vibration signal relating to extraneous vibration applied to a body surface of the subject during measurement of the cardiac signal; and

a unit for removing the extraneous vibration signal from the cardiac signal,

wherein the cardiac signal from which the extraneous vibration signal has been removed is input to the low-pass filter and the high-pass filter.

7. A cardiac signal processing method comprising:

a cardiac signal acquisition step of acquiring cardiac signals relating to heartbeats of a subject;

a low-pass filtering step of allowing passage of those cardiac signals having a first predetermined frequency or lower, among the cardiac signals;

a higher harmonic noise acquisition step of acquiring harmonic signals of low-frequency noise by performing high frequency extrapolation on the signals output in the low-pass filtering step;

a high-pass filtering step of allowing passage of those cardiac signals having a second predetermined frequency or higher, among the cardiac signals; and

a higher harmonic noise removal step of removing the harmonic signals of low-frequency noise from the signals output in the high-pass filtering step.