Heart rate variability measurement
First Claim
1. Apparatus for measuring heart rate variability comprisingmeans for receiving periodic voltage signals each having a characteristic with a magnitude proportional to a subject'"'"'s heart rate,means for storing a first voltage having a characteristic with a magnitude proportional to the previous maximum heart rate of the subject,means for storing a second voltage having a characteristic with a magnitude proportional to the previous minimum heart rate of the subject,first means for comparing the magnitude of said characteristic of said received voltage with the magnitude of said characteristic of said first voltage,means responsive to said first comparing means for storing said received voltage in said first voltage storing means only when the magnitude of said characteristic of said received voltage exceeds the magnitude of said characteristic of said stored first voltage,second means for comparing the magnitude of said characteristic of said received voltage with the magnitude of said characteristic of said second voltage,means responsive to said second comparing means for storing said received voltage in said second voltage storing means only when the magnitude of said characteristic of said received voltage is less than the magnitude of said characteristic of said second voltage, andmeans for determining the difference between the magnitudes of said characteristics of said first and second voltages respectively.
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Abstract
A method and apparatus for quantitative measurement of the long-term and short-term variability of a subject'"'"'s heart rate. Long-term variability is measured by apparatus which receives a signal having a magnitude proportional to a subject'"'"'s instantaneous heart rate with each successive heart beat during a measuring interval consisting of a fixed number of heartbeats. Each heart rate signal magnitude is compared with the previous maximum and minimum heart rate signal magnitudes in the measuring interval and the sampled heart rate magnitude is substituted for the previous maximum signal magnitude if the maximum is exceeded and for the previous minimum signal magnitude if it exceeds the magnitude of the instant sampled heart rate signal. The difference between the maximum and minimum heart rate signal magnitudes, after occurrence of the predetermined number of heartbeats, is a measure of long-term heart rate variability. To measure short-term variability the apparatus determines the average of the differences in time between successive heart beats for the predetermined number of heartbeats by comparing each latest time difference with the previous time difference and incrementing or decrementing the previous time difference until it equals the latest time difference. The number of increments or decrements are counted and divided by the predetermined number of heartbeats comprising the measuring interval to yield a measure of short-term variability.
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Citations
15 Claims
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1. Apparatus for measuring heart rate variability comprising
means for receiving periodic voltage signals each having a characteristic with a magnitude proportional to a subject'"'"'s heart rate, means for storing a first voltage having a characteristic with a magnitude proportional to the previous maximum heart rate of the subject, means for storing a second voltage having a characteristic with a magnitude proportional to the previous minimum heart rate of the subject, first means for comparing the magnitude of said characteristic of said received voltage with the magnitude of said characteristic of said first voltage, means responsive to said first comparing means for storing said received voltage in said first voltage storing means only when the magnitude of said characteristic of said received voltage exceeds the magnitude of said characteristic of said stored first voltage, second means for comparing the magnitude of said characteristic of said received voltage with the magnitude of said characteristic of said second voltage, means responsive to said second comparing means for storing said received voltage in said second voltage storing means only when the magnitude of said characteristic of said received voltage is less than the magnitude of said characteristic of said second voltage, and means for determining the difference between the magnitudes of said characteristics of said first and second voltages respectively.
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5. Apparatus for measuring heart rate variability comprising
means for storing a first count indicative of the most recent measured beat-to-beat time between successive heartbeats of a subject, means for storing a second count indicative of a previous measured beat-to-beat time of the subject, first means for comparing said first and second counts, means responsive to said comparing means for providing sequential signals to said second storage means for increasing the count in said second storage means when said first count is greater than said second count until said second count is equal to said first count, second means responsive to said comparing means for providing sequential signals to said second storage means for decreasing the count in said second storage means when said first count is less than second count until said second count is equal to said first count, and means responsive to said first and second sequential signal means for cumulatively counting the number of signals required to equalize the counts in said means for storing said first and second counts respectively.
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9. A method of measuring heart rate variability comprising
a. periodically receiving voltage signals each having a characteristic with a magnitude proportional to the subject'"'"'s heart rate, b. storing a first voltage having a characteristic with a magnitude equal to that of the first received voltage signal, said first voltage to be maintained with the magnitude of its characteristic proportional to the maximum heart rate of the subject, c. storing a second voltage having a characteristic with a magnitude equal to that of the first received voltage signal, said second voltage to be maintained with the magnitude of its characteristic proportional to the previous minimum heart rate of the subject, d. comparing the magnitude of a characteristic of each subsequent received voltage signal with the magnitude of said characteristic of said first voltage, e. equalizing the magnitude of said characteristic of said first voltage with that of said received voltage only when the magnitude of said characteristic of said received voltage exceeds the magnitude of said characteristic of said first voltage, f. comparing the magnitude of said characteristic of said received voltage with the magnitude of said characteristic of said second voltage, g. equalizing the magnitude of said characteristic of said second voltage with that of said received voltage only when the magnitude of said characteristic of said received voltage is less than the magnitude of said characteristic of said second voltage, and h. determining the difference between the magnitude of said characteristics of said first and second voltages respectively.
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14. A method of measuring heart rate variability comprising
storing a first count indicative of the most recent measured heart beat-to-beat time between successive heartbeats of a subject, storing a second count indicative of a previous measured beat-to-beat time of the subject, comparing said first and second counts, providing sequential signals for increasing said second count when said first count is greater than said second count until said second count is equal to said first count, providing sequential signals count for decreasing said second when said first count is less than said second count until second count is equal to said first count, and cumulatively counting the number of signals requied to equalize said first and second counts.
Specification