Pulse signal extraction apparatus for an automatic blood pressure gauge
First Claim
1. A signal processing system suitable for use in an automatic blood pressure gauge which generates at least one blood pressure measurement value and which includes a pressurized cuff and a pressure transducer that generates a cuff pressure signal representing pressure levels in the cuff including blood pressure pulse signal components, the signal processing system comprising:
- digitizing means adopted to be direct-current (DC) coupled to receive the cuff pressure signal for developing a sampled data digital cuff pressure signal;
means for filtering the sampled data digital cuff pressure signal to produce an auxiliary signal which identifies samples of the sampled data digital cuff pressure signal that correspond to a start of successive ones of the blood pressure pulse signal components;
pulse signal extraction means, including, a first means responsive to at least two samples of the sampled data digital cuff pressure signal which were identified by the auxiliary signal for generating a base pressure signal by interpolating new pressure signal samples between said at least two samples, which base pressure signal approximates the cuff pressure signal without the blood pressure pulse signal components, and a second means for subtracting the base pressure signal from the sampled data digital cuff pressure signal to produce a separated blood pressure pulse signal; and
means for processing the separated blood pressure pulse signal to determine said at least one blood pressure measurement value.
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Accused Products
Abstract
An automatic blood pressure gauge generates a signal representing the instantaneous pressure levels in a blood pressure cuff. This pressure signal includes a slowly changing component representing a deflating cuff and a more rapidly changing component representing blood pressure pulses that are mechanically coupled to the cuff. The pressure signal is DC coupled to a microprocessor. The microprocessor filters the pressure signal using a minimum order-statistic filter coupled in cascade with a median order-statistic filter to generate an auxiliary signal having peaks at the starting points of the pulses. This auxiliary signal is used to generate a signal representing the slowly changing component of the pressure signal. The slowly changing component of the pressure signal is subtracted from the pressure signal, leaving only the blood pressure pulse signal. The microprocessor then generates a function representing peaks of the blood pressure pulses versus a corresponding cuff pressure at which they occur. From this function, the microprocessor calculates mean, systolic and diastolic pressures using extrapolation and/or interpolation.
35 Citations
19 Claims
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1. A signal processing system suitable for use in an automatic blood pressure gauge which generates at least one blood pressure measurement value and which includes a pressurized cuff and a pressure transducer that generates a cuff pressure signal representing pressure levels in the cuff including blood pressure pulse signal components, the signal processing system comprising:
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digitizing means adopted to be direct-current (DC) coupled to receive the cuff pressure signal for developing a sampled data digital cuff pressure signal; means for filtering the sampled data digital cuff pressure signal to produce an auxiliary signal which identifies samples of the sampled data digital cuff pressure signal that correspond to a start of successive ones of the blood pressure pulse signal components; pulse signal extraction means, including, a first means responsive to at least two samples of the sampled data digital cuff pressure signal which were identified by the auxiliary signal for generating a base pressure signal by interpolating new pressure signal samples between said at least two samples, which base pressure signal approximates the cuff pressure signal without the blood pressure pulse signal components, and a second means for subtracting the base pressure signal from the sampled data digital cuff pressure signal to produce a separated blood pressure pulse signal; and means for processing the separated blood pressure pulse signal to determine said at least one blood pressure measurement value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. Apparatus suitable for use in an automatic blood pressure gauge which generates at least one blood pressure measurement value and which includes a pressurized cuff and a pressure transducer which generates a pressure signal representing pressure levels in the cuff resulting from blood pressure pulses, the apparatus comprising:
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sampling means responsive to said pressure signal for generating a sampled data pressure signal; order-statistic filtering means for processing the sampled data pressure signal to enhance the blood pressure pulse signal components thereof as compared to the remainder of the pressure signal, and including a series combination of two ranked-order filters, each filter providing a differently ranked sample of said pressure signal applied to its input, as its output; pulse signal extraction means, coupled to receive an output of the order-statistic filtering means and coupled to receive the sampled data pressure signal, for generating a function representing respective peak amplitudes of successive ones of said blood pressure pulses and respective cuff pressure levels at which the peak amplitudes occur; and means for calculating said at least one blood pressure measurement value using the determined function. - View Dependent Claims (10, 11, 12, 13)
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14. Apparatus suitable for use in an automatic blood pressure gauge which generates at least one blood pressure measurement value and which includes a pressurized cuff and a pressure transducer which generates a digital sampled data pressure signal representing pressure levels in the cuff resulting from blood pressure pulses, the apparatus comprising:
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minimum order-statistic filtering means for processing the pressure signal to produce an output signal in which blood pressure pulse signal components of the sampled data pressure signal are enhanced; median order-statistic filtering means, coupled in cascade with the minimum order-statistic filtering means for processing the output signal provided thereby to further enhance the blood pressure pulse signal components; pulse signal extraction means, coupled to receive an output signal of the median order-statistic filtering means for separating the blood pressure pulse signal components from the pressure signal and for generating a function representing peak amplitudes of successive ones of said blood pressure pulse signal components versus cuff pressure levels corresponding to the occurrence of the peak amplitudes, respectively; and means for calculating, from the function, said at least one blood pressure measurement value. - View Dependent Claims (15)
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16. A signal processing apparatus suitable for use in an automatic patient monitor which generates at least one physiological signal having a relatively slowly varying base component and a more rapidly varying pulsatile information component representative of a physiological condition of the patient being monitored, the signal processing apparatus comprising:
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sampling means responsive to said physiological signal for generating a sampled data signal; order-statistic filtering means for processing the physiological signal to enhance the pulsitile information signal component thereof as compared to the base component, and includes a series combination of two ranked-order filters, each providing a differently ranked sample of said physiological signal applied to its input as its output; pulse signal extraction means, coupled to receive an output signal of the order-statistic filtering means and coupled to receive the physiological signal, for separating the pulsatile information signal component from the more slowly varying base component of the physiological signal; and means for processing the separated pulse signal component to determine the current condition of the patient represented by said pulsatile information component of the physiological signal. - View Dependent Claims (17, 18, 19)
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Specification