Method and device for noise detection in physiological signals
First Claim
1. A method for determination of noise in a sampled physiological signal, the sampled physiological signal including a consecutive sequence of samples, each sample having a signal amplitude, the method including the steps of:
- a. providing a signal quality check window that includes a number of consecutive samples;
b. providing an upper noise threshold and a lower noise threshold, wherein the upper noise threshold and the lower noise threshold define at least three amplitude ranges;
(1) a high range for signal amplitudes exceeding the upper noise threshold,(2) a medium range for signal amplitudes between the upper noise threshold and the lower noise threshold, and(3) a low range for signal amplitudes below the lower noise threshold;
c. comparing each sample within the quality check window with the upper noise threshold and with the lower noise threshold;
d. determining any changes between amplitude ranges between each two adjacent sample pairs within the quality check window;
e. determining a supra-threshold sample sum corresponding to the number of samples outside the medium range; and
f. generating a low signal quality indication signal if the supra-threshold sample sum exceeds a predefined threshold.
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Abstract
A method for determining the signal quality of samples in a physiological signal, in particular an electrocardiogram (ECG) signal, is provided. A supra-threshold sample sum, a noise threshold crossing sum, or both are calculated in a noise detection window including the sample to be evaluated, and low signal quality is indicated if either or both of the sums exceed respective values. ECG beat detections can then be labeled as unreliable based on the determination of low signal quality for one or more samples between the detections.
25 Citations
25 Claims
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1. A method for determination of noise in a sampled physiological signal, the sampled physiological signal including a consecutive sequence of samples, each sample having a signal amplitude, the method including the steps of:
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a. providing a signal quality check window that includes a number of consecutive samples; b. providing an upper noise threshold and a lower noise threshold, wherein the upper noise threshold and the lower noise threshold define at least three amplitude ranges; (1) a high range for signal amplitudes exceeding the upper noise threshold, (2) a medium range for signal amplitudes between the upper noise threshold and the lower noise threshold, and (3) a low range for signal amplitudes below the lower noise threshold; c. comparing each sample within the quality check window with the upper noise threshold and with the lower noise threshold; d. determining any changes between amplitude ranges between each two adjacent sample pairs within the quality check window; e. determining a supra-threshold sample sum corresponding to the number of samples outside the medium range; and f. generating a low signal quality indication signal if the supra-threshold sample sum exceeds a predefined threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for determination of noise in a sampled physiological signal, the sampled physiological signal including a consecutive sequence of samples, each sample having a signal amplitude, the method including the steps of:
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a. providing a signal quality check window that includes a number of consecutive samples; b. providing; (1) an upper noise threshold at a signal amplitude greater than the average signal amplitude of the samples, and (2) a lower noise threshold at a signal amplitude less than the average signal amplitude of the samples, with a noise tolerance zone being defined between the upper and lower noise thresholds; c. identifying one or more of the samples outside the noise tolerance zone as having low signal quality; d. detecting an ECG beat at one or more samples having a signal amplitude exceeding a beat detection threshold, e. following the ECG beat, adjusting one or more of the upper and lower noise thresholds in dependence on the amplitudes of the ECG beat and one or more prior ECG beats. - View Dependent Claims (17, 18, 19, 20)
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21. A method for determination of noise in a sampled physiological signal, the sampled physiological signal including a consecutive sequence of samples, each sample having a signal amplitude, the method including the steps of
a. defining a quality check window including a number (NZDW) of samples, b. determining a supra-threshold sample sum (STS_SUM) corresponding to the number of samples in the quality check window having an amplitude that either: -
(1) exceeds an upper noise threshold (NZTHRESH), or (2) falls below a lower noise threshold (−
NZTHRESH),c. determining a noise threshold crossing sum (NZX_SUM) corresponding to the sum of the number of noise threshold crossings between each two consecutive samples in the quality check window, d. indicating a low signal quality for at least one of the samples within the quality check window if; (1) the noise threshold crossing sum (NZX_SUM) exceeds a first predefined value (TX1), or (2) the supra-threshold sample sum (STS_SUM) exceeds a second predefined value (ST1). - View Dependent Claims (22, 23, 24, 25)
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Specification