Method of measuring vital function and measuring device

• US 6,282,439 B1
• Filed: 10/05/1999
• Issued: 08/28/2001
• Est. Priority Date: 10/08/1998
• Status: Expired due to Term

• Current Assignee: Polar Electro Oy
• Original Assignee: Polar Electro Oy
• Inventors: Ruha, Antti
• Primary Examiner(s): Lacyk, John P.
• Assistant Examiner(s): Natnithithadha, Navin
• Application Number:
  US09/412,485
• Time in Patent Office: 693 Days
• Field of Search: 600/509, 600/516, 600/517, 600/521, 600/508, 600/500, 600/300
• US Class Current: 600/509
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle

Abstract

The invention relates to a method of measuring a vital function and a measuring device implementing the method. The measuring device receives for example heart pulses as signal episodes. The measuring device calculates a coherent average of the signal episodes in an averaging unit to determine the wave form of the signal episode. The measuring device also preferably comprises an adapted filter the impulse response of which is based on the coherent average of the signal episode.

Claims

1. A method of measuring a recurrent signal episode of a vital function, the method employing an adapted filter for detecting the signal episode, the method comprising

weighting a single signal episode with a weighting value (μ

) which depends on the quality of the single signal episode, and

calculating a coherent average of single signal episodes to determine the wave form of the signal episode.

2. A method according to claim 1, wherein the signal episode is the QRS complex of the heart rate.

3. A method according to claim 1, wherein weighting is recursive.

4. A method according to claim 1, wherein the magnitude of the weighting value is a function of the signal-to-noise ratio or the like describing the quality of a single signal episode.

5. A method according to claim 4, wherein to determine the weighting value (μ

), the quality of a single signal episode is determined by means of a sample correlation coefficient or energy transmission of the adapted filter.

6. A method according to claim 1, wherein to determine the weighting value (μ

), the quality of a single signal episode is determined by comparing the single signal episode with the signal estimate calculated using coherent averaging.

7. A method according to claim 6, wherein averaging is finished when the similarity obtained as a result of the comparison is greater than the predetermined minimum value of the variable describing the signal quality.

8. A method according to claim 1, wherein to determine the weighting value (μ

), the quality of a single signal episode is determined by comparing the single signal episode with another single signal episode.

9. A method according to claim 1, wherein the signal episode is taken into account in calculation of the coherent average if the energy transmission of the signal episode in the adapted filter exceeds a preset minimum value.

10. A method according to claim 9, wherein the preset minimum value is adjusted adaptively according to the quality of the signal episode.

11. A method according to claim 9, wherein the poorer the quality of the signal episode, the higher the threshold value.

12. A method according to claim 1, wherein single signal episodes are classified into predetermined classes by comparing a single signal episode with a signal estimate determined by means of coherent averaging.

27. A method according to claim 8, wherein averaging is finished when the similarity obtained as a result of the comparison is greater than the predetermined minimum value of the variable describing the signal quality.

13. A method of determining the impulse response (H) of a recurrent signal episode of a vital function in a detector based on an adapted filter, the method comprising

calculating a coherent average of single signal episodes, the signal episodes being weighted for averaging with a weighting value (μ

) that depends on the quality of the single signal episodes, and

employing the coherent average of the signal episode for forming the impulse response of the adapted filter.

14. A method according to claim 13, wherein the signal episode is the QRS complex.

15. A method according to claim 13, wherein a single signal episode is weighted for averaging with a weighting value (μ

) which depends on the quality of the single signal episode, and a coherent average of the weighted signal episodes is calculated.

16. A method according to claim 13, wherein weighting is recursive.

17. A method according to claim 13, wherein the signal episode is taken into account in calculation of the coherent average if the energy transmission of the signal episode in the adapted filter exceeds a preset minimum value.

19. A measuring device according to claim 15, wherein

the signal episode is the QRS complex of the heart rate.

20. A measuring device according to claim 19, wherein

the weighting unit is arranged determine the weighting value (μ

) as the function of the signal-to-noise ratio or the like describing the quality of a single signal episode.

21. A measuring device according to claim 20, wherein the averaging unit does not perform averaging if the similarity obtained as a result of the comparison is greater than the predetermined threshold value.

22. A measuring device according to claim 19, wherein

the weighting unit is arranged to determine the quality of a single signal episode by comparing the single signal episode with the signal episode determined in the coherent averaging unit.

23. A measuring device according to claim 19, wherein

the weighting unit is arranged to determine the quality of a single signal episode by comparing the single signal episode with another signal episode.

24. A measuring device according to claim 22, wherein the averaging unit does not perform averaging if the similarity obtained as a result of the comparison is greater than the predetermined threshold value.

18. A measuring device for measuring a recurrent signal episode for a vital function, the measuring device comprising electrodes for receiving signal episodes generated by the vital function and an adapted filter for detecting the signal episodes received by the electrodes, the measuring device further comprising

a weighting unit which is arranged to weight a single signal episode with a weighting value which depends on the quality of the single signal episode;

and

a coherent averaging unit for determining the wave form of the signal episode received by the electrodes.

25. A measuring device according to claim 18, wherein

the weighting unit is arranged to determine the quality of a single signal episode by means of a sample correlation coefficient or energy transmission of the adapted filter.

26. A measuring device according to claim 25, wherein the measuring device is arranged to adjust the threshold value of energy transmission adaptively according to the quality of the signal episode.

28. A measuring device for measuring a recurrent signal episode of a vital function, the measuring device comprising electrodes for receiving signal episodes generated by the vital function, the measuring device further comprising:

a weighting unit arranged to weight a single signal episode with a weighting value which depends on the quality of the single signal episode;

a coherent averaging unit for calculating a coherent average of the signal episodes received by the electrodes, and

an adapted filter having an impulse response based on the coherent average of the signal episode.

29. A measuring device according to claim 28, wherein the adapted filter is arranged to determine energy transmission and the measuring device is arranged to take the signal episode into account if the energy transmission of the signal episode exceeds the threshold value.

30. A measuring device according to claim 29, wherein the poorer the quality of the signal episode, the higher the threshold value.

31. A measuring device according to claim 28, wherein the measuring device comprises a classifier which is arranged to classify single signal episodes into predetermined classes by comparing the single signal episode with the signal estimate determined by coherent averaging.

32. A measuring device according to claim 28, wherein the signal episode is the QRS complex.

33. A measuring device according to claim 28, wherein the measuring device comprises a weighting unit which is arranged to weight a single signal episode with a weighting value which depends on the quality of the single signal episode.

34. A method of determining the impulse response (H) of a recurrent signal episode of a vital function in a detector based on an adapted filter, the method comprising

weighting a single signal episode with a weighting value (μ

) which depends on the quality of the single signal episode;

calculating a coherent average of single signal episodes; and

employing the coherent average of the signal episode for forming the impulse response of the adapted filter.

35. A measuring device for measuring a recurrent signal episode of a vital function, the measuring device comprising electrodes for receiving signal episodes generated by the vital function, the measuring device further comprising

a weighting unit which is arranged to weight a single signal episode with a weighting value which depends on the quality of the single signal episode,

a coherent averaging unit for calculating a coherent average of the signal episodes received by the electrodes;

and

an adapted filter having an impulse response based on the coherent average of the signal episode.