Use of the frequency spectrum of artifact in oscillometry
First Claim
1. A method of computing an oscillometric envelope for use in determining the blood pressure of a patient, the method comprising the steps of:
- receiving an oscillometric signal from a blood pressure cuff positioned on the patient;
receiving an indication of the heart rate of the patient;
computing a fundamental frequency of the heart rate;
converting the oscillometric signal to the frequency domain;
filtering the frequency domain oscillometric signal using a band pass filter having a first pass band centered around the fundamental frequency;
calculating the energy of the frequency domain oscillometric signal in a first noise band having a defined first frequency range having an upper limit and a lower limit below the first pass band;
calculating the energy of the frequency domain oscillometric signal in a second noise band having a defined second frequency range having an upper limit and a lower limit above the first pass band;
combining the calculated energy in the first and second noise bands to define the energy within the defined noise bands;
calculating the energy of the frequency domain oscillometric signal in the first pass band centered around the fundamental frequency;
calculating a ratio of the energy of the frequency domain oscillometric signal within the defined noise bands to the energy of the frequency domain oscillometric signal within the first pass band;
reconstructing the oscillometric signal from the filtered frequency domain signal in the first pass band only when the calculated ratio is below a threshold; and
computing an oscillometric envelope data point from the reconstructed oscillometric signal only when the calculated ratio is below the threshold.
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Abstract
A system and method for processing oscillometric data from a plurality of pressure steps to determine the blood pressure of a patient. A heart rate monitor connected to the patient acquires the patient'"'"'s heart rate. A time-to-frequency domain converter receives oscillometric data and converts the oscillometric data into the frequency domain. Based upon the calculated heart rate, the system and method filters the frequency domain oscillometric signal with pass bands centered at the fundamental frequency and at least one fundamental frequency. The energy of the frequency domain signal within the pass bands is compared to at least a portion of the energy of the frequency domain oscillometric signal outside of the pass bands. Based upon the comparison, the signal determines whether the signal at the current pressure step should be utilized in calculating the blood pressure of the patient.
10 Citations
13 Claims
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1. A method of computing an oscillometric envelope for use in determining the blood pressure of a patient, the method comprising the steps of:
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receiving an oscillometric signal from a blood pressure cuff positioned on the patient; receiving an indication of the heart rate of the patient; computing a fundamental frequency of the heart rate; converting the oscillometric signal to the frequency domain; filtering the frequency domain oscillometric signal using a band pass filter having a first pass band centered around the fundamental frequency; calculating the energy of the frequency domain oscillometric signal in a first noise band having a defined first frequency range having an upper limit and a lower limit below the first pass band; calculating the energy of the frequency domain oscillometric signal in a second noise band having a defined second frequency range having an upper limit and a lower limit above the first pass band; combining the calculated energy in the first and second noise bands to define the energy within the defined noise bands; calculating the energy of the frequency domain oscillometric signal in the first pass band centered around the fundamental frequency; calculating a ratio of the energy of the frequency domain oscillometric signal within the defined noise bands to the energy of the frequency domain oscillometric signal within the first pass band; reconstructing the oscillometric signal from the filtered frequency domain signal in the first pass band only when the calculated ratio is below a threshold; and computing an oscillometric envelope data point from the reconstructed oscillometric signal only when the calculated ratio is below the threshold. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of processing oscillometric data for use in determining the blood pressure of a patient, the method comprising:
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receiving an oscillometric signal from a blood pressure cuff connected to the patient; receiving an indication of the heart rate of the patient; computing a fundamental frequency and at least one harmonic frequency of the heart rate; converting the oscillometric signal to the frequency domain; filtering the frequency domain signal with a first pass band centered at the fundamental frequency and a second pass and centered at the at least one harmonic frequency; determining the energy of the frequency domain oscillometric signal in the combination of the first and second pass bands; calculating the energy of the frequency domain oscillometric signal in a first noise band having a defined first frequency range having an upper limit and a lower limit below the first pass band and in a second noise band having a defined second frequency range having an upper limit and a lower limit above the first pass band; calculating the energy of the frequency domain oscillometric signal in a third noise band having a defined third frequency range having an upper limit and a lower limit below the second pass band and in a fourth noise band having a defined fourth frequency range having an upper limit and a lower limit above the second pass band; combining the calculated energy in the first, second, third and fourth noise bands to define the energy within the defined noise bands; calculating a ratio of the energy of the frequency domain oscillometric signal within the defined noise bands to the energy of the frequency domain oscillometric signal within the first and second pass bands; reconstructing the oscillation signal from the filtered frequency domain signal in the pass bands when the calculated ratio is below a threshold; and computing an oscillometric envelope data point for the current pressure within the blood pressure cuff based upon the reconstructed oscillometric signal. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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Specification