Method and apparatus for measuring heart rate
First Claim
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1. A method for detecting a heart beat and calculating heart rate on the basis of the detected heart beats, the method comprising:
- forming an EKG signal on the basis of signals measured from the skin of a person, detecting from the EKG signal a heart beat candidate to which a rationality analysis is performed, in which rationality analysis;
the time difference between the heart beat candidate and the heart beat detection preceding it is calculated and on the basis of the time difference, a momentary heart rate value is calculated, the calculated momentary heart rate value is compared with a median value of the heart rate, which is a median of two or more earlier heart rate values, the heart beat candidate is accepted as a heart beat detection, if the momentary heart rate value calculated on the basis of the heart beat candidate is, when compared with the median value, within threshold values of the median value, and updating as the heart rate value the momentary heart rate value calculated on the basis of the accepted heart beat detection.
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Abstract
An arrangement for detecting a heart beat and calculating heart rate on the basis of the detected heart beats, comprising means for measuring an EKG signal from a person'"'"'s hands, a computer for detecting a heart beat from the measured signal and for performing a rationality analysis to verify a heart beat detection and for calculating the heart rate on the basis of the detected heart beats, the arrangement further comprising means for displaying the calculated heart rate and connected to the computer.
61 Citations
22 Claims
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1. A method for detecting a heart beat and calculating heart rate on the basis of the detected heart beats, the method comprising:
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forming an EKG signal on the basis of signals measured from the skin of a person, detecting from the EKG signal a heart beat candidate to which a rationality analysis is performed, in which rationality analysis;
the time difference between the heart beat candidate and the heart beat detection preceding it is calculated and on the basis of the time difference, a momentary heart rate value is calculated, the calculated momentary heart rate value is compared with a median value of the heart rate, which is a median of two or more earlier heart rate values, the heart beat candidate is accepted as a heart beat detection, if the momentary heart rate value calculated on the basis of the heart beat candidate is, when compared with the median value, within threshold values of the median value, and updating as the heart rate value the momentary heart rate value calculated on the basis of the accepted heart beat detection. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
a signal is measured from a person'"'"'s skin at a minimum of two measuring points, and an analog EKG signal is formed by means of the potential difference of said signals, the EKG signal is converted into digital format to be a sample signal containing samples, the sample signal is read one sample at a time until a first sample can be located from the sample signal, which exceeds a threshold value set to a first maximum value of the EKG signal and contains a local maximum, and until a second sample can be located from the sample signal, which is lower than a minimum value of the EKG signal and contains a local minimum, and until a third sample can be located from the sample signal, which exceeds a threshold value set to a second maximum value of the EKG signal and contains a second local maximum, the part of the sample signal formed by the first, second and third sample is accepted as the heart beat candidate. -
8. A method as claimed in claim 7, wherein a threshold value is used for the first maximum value, which is approximately 50% of the average R peak amplitude of the earlier accepted heart beat detections of the person.
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9. A method as claimed in claim 7, wherein the average noise level is calculated during the measurement of the EKG signal, and a threshold value is used for the first maximum value, which is approximately 150% with respect to the average of noise.
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10. A method as claimed in claim 7, wherein the same threshold value is used for the minimum value and the second maximum value as for the first maximum value.
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11. A method as claimed in claim 7, wherein the time difference between the first sample and the second sample is calculated, and a part of the sample signal is accepted as a heart beat only if the time difference is within the limits defined by the threshold values set for the time difference.
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12. An arrangement for detecting a heart beat and calculating heart rate on the basis of the detected heart beats, comprising:
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at least one measuring electrode for measuring a signal from the skin of one hand of a person, and at least one measuring electrode for measuring a signal from the skin of the other hand, an amplifier connected to said measuring electrodes for amplifying the potential difference of the signals measured by the measuring electrodes for the purpose of forming an EKG signal, an analog-to-digital converter for receiving the signal from the amplifier and for converting the signal into digital format to be a sample signal containing samples, and a computer which is arranged;
to read the digital signal and to detect from the sample signal a heart beat candidate, to perform a rationality analysis for the heart beat detection, in which the computer is arranged;
to calculate a time difference between the heart beat candidate and the heart beat detection preceding it, and to calculate on the basis of the time difference, a momentary heart rate value, to compare the calculated momentary heart rate value with a median value of the heart rate, which is a median of two or more earlier calculated heart rate values, to accept the heart beat candidate as a heart beat detection, if the momentary heart rate value calculated on the basis of the heart beat candidate is, when compared with the median value, within threshold values of the median value, and to update as the heart rate value the momentary heart rate value calculated on the basis of the accepted heart beat detection, the arrangement further comprising display means connected to the computer and displaying the calculated heart rate value on the basis of the accepted heart beat detections. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
to read the sample signal one sample at a time until a first sample can be located from the sample signal, which exceeds a threshold value set to a first maximum value of the EKG signal and contains a local maximum, and until a second sample can be located from the sample signal, which is lower than a minimum value of the EKG signal and contains a local minimum, and until a third sample can be located from the sample signal, which exceeds a threshold value set to a second maximum value of the EKG signal and contains a second local maximum, and to accept the part of the sample signal formed by the first, second and third sample as the heart beat candidate. -
19. An arrangement as claimed in claim 18, wherein the computer is arranged to use for the first maximum value a threshold value which is approximately 50% of the average R peak amplitude of the earlier accepted heart beat detections of the person.
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20. An arrangement as claimed in claim 18, wherein the computer is arranged to calculate the average noise level during the measurement of the EKG signal, and to use for the first maximum value a threshold value which is approximately 150% with respect to the average of noise.
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21. An arrangement as claimed in claim 18, wherein the computer is arranged to use the same threshold value for the minimum value and the second maximum value as for the first maximum value.
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22. An arrangement as claimed in claim 18, wherein the computer is arranged to calculate the time difference between the first sample and the second sample, and to accept a part of the sample signal as a heart beat detection only if the time difference is within the limits defined by the threshold values set for the time difference.
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Specification