Pulse rate monitor

• US 5,697,374 A
• Filed: 12/14/1994
• Issued: 12/16/1997
• Est. Priority Date: 12/20/1993
• Status: Expired due to Term

• Current Assignee: Seiko Instruments Incorporated (Seiko Group)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Sakumoto, Kazumi, Tsubata, Keisuke, Hayakawa, Motomu, Odagiri, Hiroshi, Nakamura, Chiaki, Nosaka, Naokatsu
• Primary Examiner(s): NASSER, ROBERT L
• Application Number:
  US08/355,503
• Time in Patent Office: 1,098 Days
• Field of Search: 128/672, 128/687-690, 128/696, 128/706, 128/707, 128/713
• US Class Current: 600/500
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/1104 induced by stimuli or drugs; A61B5/1102 takes precedence; investigating medicinal preparations G01N33/15
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/6826 Finger
• 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 5/7253 characterised by using transforms
• CPC Class Codes: A61B 5/7257 using Fourier transforms

Abstract

A pulse rate monitor having an enhanced accuracy, reduced power consumption and reduced calculation time comprises a pulse wave extraction circuitry for extracting pulse wave frequency components from a power spectrum output of a pulse wave sensor and a movement sensor, and a pulse rate calculation circuit for calculating a pulse rate in accordance with the extracted pulse wave frequency components. A display device may be included to display the calculated pulse rate. In order to reduce power consumption, unnecessary circuitry may be deactivated and unnecessary operations may be avoided by use of a changing circuit which changes the method of calculation when movement of the user is not detected. Accordingly, when no movement has been detected for a predetermined period of time, the pulse rate may be calculated based upon a direct output of the pulse rate sensor, while the frequency analysis circuitry and calculation circuitry may remain deactivated.

Claims

1. A pulse rate monitor comprising:

pulse wave detecting means for detecting a pulse from a biological body and outputting a pulse wave signal in accordance therewith;

movement detecting means for detecting physical movement of the biological body and for outputting a corresponding movement signal in response thereto;

frequency analyzing means for resolving the pulse wave signal and the movement signal into frequency components including pulse wave components and movement components;

pulse wave component extracting means for extracting a selected pulse wave component from the pulse wave components and the movement components;

pulse rate calculating means for calculating a pulse rate; and

timer means for measuring a time duration during which no physical movement of the biological body is detected and for outputting a changeover signal to the pulse rate calculating means when the duration exceeds a predetermined time period;

wherein the pulse rate calculating means includes means for calculating the pulse rate based on the selected pulse wave component extracted by the pulse wave component extracting means when movement of the biological body is detected and for calculating the pulse rate in accordance with the pulse wave signal when the changeover signal is received.

2. A pulse rate monitor according to claim 1;

wherein the pulse wave component extracting means includes means for extracting the pulse wave component having a maximum power as the selected pulse wave component.

3. A pulse rate monitor according to claim 1;

wherein the frequency analyzing means comprises a first analog to digital converter for converting the pulse wave signal into a first digital signal;

a second analog to digital converter for converting the movement signal into a second digital signal;

a memory for storing the first and second digital signals;

pulse wave signal frequency analyzing means for analyzing the first digital signal to obtain a power spectrum of the pulse wave signal; and

movement signal frequency analyzing means for analyzing the second digital signal to obtain a power spectrum of the movement signal;

wherein said pulse wave component extracting means includes means for receiving pulse wave components of the power spectrum of the pulse wave signal and movement components of the power spectrum of the movement signal.

4. A pulse rate monitor according to claim 3;

wherein the pulse wave component extracting means comprises movement component eliminating means for eliminating the movement components from the pulse wave components outputted by the pulse wave signal frequency analyzing means; and

pulse wave maximum component extracting means for extracting a pulse wave component having the maximum power from pulse wave components obtained by the movement component eliminating means.

5. A pulse rate monitor according to claim 3;

wherein the pulse wave component extracting means comprises movement maximum component extracting means for extracting a movement component having a maximum power from the power spectrum of the movement signal obtained by the movement signal frequency analyzing means;

harmonic specifying means for deriving the harmonic order of the movement component having the maximum power and for deriving other harmonic components of the movement therefrom;

movement component eliminating means for eliminating all of the harmonic components specified by the harmonic specifying means from the pulse wave components obtained by the pulse wave signal frequency analyzing means; and

pulse wave maximum component extracting means for extracting a pulse wave component having a maximum power from the pulse wave components obtained by the movement component eliminating means.

6. A pulse rate monitor according to claim 3;

wherein the pulse wave component extracting means comprises movement maximum component extracting means for extracting a movement component having a maximum power from the power spectrum of the movement signal obtained by the movement signal frequency analyzing means;

harmonic specifying means for identifying the extracted movement component obtained by the movement maximum component extracting means as a second order harmonic, and for specifying other harmonic components, including a fundamental harmonic component, of the movement signal;

movement component eliminating means for eliminating all of the harmonic components specified by the harmonic specifying means from the pulse wave components obtained by the pulse wave signal frequency analyzing means; and

pulse wave maximum component extracting means for extracting a pulse wave component having a maximum power from the pulse wave components obtained by the movement component eliminating means.

7. A pulse rate monitor according to claim 3;

wherein the pulse wave signal frequency analyzing means and the movement signal frequency analyzing means each perform a Fast Fourier Transform operation.

8. A pulse rate monitor as claimed in claim 1;

further comprising calculation changing means for changing an input signal to the pulse rate calculating means from the selected pulse wave component to the pulse wave signal output by the pulse wave detecting means in response to the changeover signal output by the timer means.

9. A pulse rate monitor according to claim 1;

wherein the pulse wave component extracting means includes means for eliminating the movement components by determining a specific movement component and deriving the frequency of other movement components in accordance therewith.

10. A pulse rate monitor according to claim 1;

further comprising means responsive to the changeover signal for deactivating the frequency analyzing means and the pulse wave component extracting means and responsive to a movement signal for reactivating the frequency analyzing means and the pulse wave component extracting means.

11. A pulse rate monitor comprising:

pulse wave detecting means for detecting a pulse from a biological body and outputting a corresponding pulse wave signal;

movement detecting means for detecting a movement of the biological body and outputting a corresponding movement signal;

frequency analyzing means for converting the pulse wave signal and the movement signal into frequency components consisting of pulse wave components and movement components;

frequency specifying means for specifying the movement components as a fundamental harmonic component of the movement and at least one non-fundamental harmonic component of the movement;

eliminating means for eliminating the harmonic components specified by the frequency specifying means and outputting a corresponding signal; and

pulse rate calculating means for calculating a pulse rate in accordance with the output signal of the eliminating means.

12. A pulse rate monitor according to claim 11;

wherein the eliminating means further comprises subtracting means for performing a subtraction between the pulse wave components and the movement components, and extracting means for extracting a component having the maximum power from pulse wave components obtained by the subtracting means.

13. A pulse rate monitor according to claim 11;

wherein the frequency specifying means comprises harmonic specifying means for specifying movement components corresponding to at least one harmonic order, and fundamental calculating means for calculating a fundamental harmonic of the movement components based upon a specified movement component.

14. A pulse rate monitor according to claim 13;

wherein the specified movement component is the second harmonic component of the movement components.

15. A pulse rate monitor according to claim 11;

wherein the pulse rate calculating means includes means for calculating the pulse rate in accordance with a component having the maximum power from the output signal of the eliminating means.

16. A pulse rate monitor according to claim 11;

wherein the frequency analyzing means comprises a first analog to digital converter for converting the pulse wave signal into a first digital signal;

a second analog to digital converter for converting the movement signal into a second digital signal;

a memory for storing the first and second digital signals;

pulse wave signal frequency analyzing means for analyzing the first digital signal to obtain a power spectrum of the pulse wave signal;

movement signal frequency analyzing means for analyzing the second digital signal to obtain a power spectrum of the movement signal; and

wherein the eliminating means includes means for receiving pulse wave components of the power spectrum of the pulse wave signal and movement components of the power spectrum of the movement signal.

17. A pulse rate monitor according to claim 16;

wherein the eliminating means includes means for extracting the pulse wave component having the maximum power from the pulse wave components.

18. A pulse rate monitor according to claim 16;

wherein the frequency specifying means includes means for specifying the movement component having the maximum power among the movement components, means for deriving the harmonic order of the movement component having the maximum power, and means for deriving other harmonic components of the movement therefrom; and

the eliminating means includes means for eliminating all harmonic components specified by the frequency specifying means from the pulse wave components obtained by the pulse wave signal frequency analyzing means.

19. A pulse rate monitor according to claim 16;

wherein the frequency specifying means comprises means for determining the movement component having a maximum power from the movement components obtained by the movement signal frequency analyzing means, for specifying the movement component obtained by the movement maximum component determining means as a second order harmonic component of the movement, and for specifying other harmonic components of the movement in accordance therewith; and

the eliminating means comprises means for eliminating all harmonic components specified by the frequency specifying means from the pulse wave components obtained by the pulse wave signal frequency analyzing means.

20. A pulse rate monitor according to claim 16;

wherein the pulse wave signal frequency analyzing means and the movement signal frequency analyzing means both perform a Fast Fourier Transform to calculate the power spectrum of the pulse wave signal and the power spectrum of the movement signal.

21. A pulse rate monitor according to claim 11;

further comprising a timer for timing a duration during which no movement is detected and outputting a changeover signal when the duration exceeds a predetermined period of time; and

means for controlling the pulse rate calculating means to calculate the pulse rate based upon the output of the pulse wave detecting means in response to the changeover signal.