Systems and Methods Utilizing Plethysmographic Data
First Claim
1. A method for facilitating detection of changes in blood volume, said method comprising steps of:
- sampling a plethysmograph (PG) waveform;
calculating a spectrum for the PG waveform having a cardiac signal and at least one blood volume indicator;
detecting the cardiac signal or a harmonic thereof within normal cardiac frequencies of the PG waveform spectrum;
detecting the blood volume indicator;
determining a signal strength for each of the cardiac signal or the harmonic thereof and the blood volume indicator, wherein at least one of the determined signal strengths is calculated over a range of characteristic frequencies;
calculating a normalized value for the blood volume indicator by dividing the signal strength of the blood volume indicator by the signal strength of the cardiac signal or the harmonic thereof.
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Accused Products
Abstract
Disclosed are apparatus, systems and methods utilizing attributes of the cardiac signal to calibrate/normalize components of the plethysmographic (PG) waveform indicating changes in venous and arterial blood volume. In the time-domain, amplitudes of respiratory-induced variations of the DC and AC components of the PG waveform may be calibrated/normalized based on an average amplitude of the PG waveform, e.g., over a respiratory cycle. Similarly, in the frequency domain, respiratory signal strength and side-band signal strength may be advantageously calibrated/normalized based on the strength of the cardiac signal or a harmonic thereof.
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Citations
34 Claims
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1. A method for facilitating detection of changes in blood volume, said method comprising steps of:
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sampling a plethysmograph (PG) waveform; calculating a spectrum for the PG waveform having a cardiac signal and at least one blood volume indicator; detecting the cardiac signal or a harmonic thereof within normal cardiac frequencies of the PG waveform spectrum; detecting the blood volume indicator; determining a signal strength for each of the cardiac signal or the harmonic thereof and the blood volume indicator, wherein at least one of the determined signal strengths is calculated over a range of characteristic frequencies; calculating a normalized value for the blood volume indicator by dividing the signal strength of the blood volume indicator by the signal strength of the cardiac signal or the harmonic thereof. - View Dependent Claims (2, 3, 6, 9, 10, 11, 12, 14, 16)
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29. A method for facilitating detection of changes in blood volume, said method comprising steps of:
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sampling a plethysmograph (PG) waveform; detecting an average amplitude of the PG waveform over a period of time; detecting a blood volume indicator; calculating a normalized value for the blood volume indicator by dividing the amplitude of the blood volume indicator by the average amplitude of the PG waveform. - View Dependent Claims (30, 31)
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32. A system for facilitating detecting changes in blood volume, said system comprising a plethysmorgraphic device coupled with a processing unit said processing unit further including:
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means for sampling a plethysmograph (PG) waveform; means for detecting an average amplitude of the PG waveform over a period of time; means for detecting a blood volume indicator; means for calculating a normalized value for the blood volume indicator by dividing the amplitude of the blood volume indicator by the average amplitude of the PG waveform. - View Dependent Claims (18, 21, 26, 27, 33, 34)
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Specification