Noninvasive method and apparatus for measuring blood pressure by determining a maximum frequency of spectral content of the second heart sound
First Claim
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1. A method for noninvasively estimating a blood pressure, the method comprising:
- a) applying a bandpass filter to a second heart sound (S2) component to generate a filtered S2 component, the bandpass filter having a lower cutoff frequency greater than a maximum frequency of the S2 component;
b) estimating the maximum frequency of the S2 component using the filtered S2 component;
c) applying a predetermined relationship between the estimated maximum frequency and blood pressure to generate a blood pressure estimate; and
d) displaying the blood pressure estimate,wherein step (b) includes;
(b1) calculating a ratio between the S2 component and the filtered S2 component;
(b2) decreasing the lower cutoff frequency and repeating steps (a) and (b1) with the decreased lower cutoff frequency to calculate the ratio, the lower cutoff frequency being decreased until the calculated ratio is less than or equal to a predetermined threshold, andwherein the decreased lower cutoff frequency is used to define the estimated maximum frequency.
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Abstract
Methods and apparatus for noninvasively estimating a blood pressure are provided. A bandpass filter is applied to a second heart sound (S2) component to generate a filtered S2 component. The bandpass filter has a lower cutoff frequency greater than a maximum frequency of the S2 component. The maximum frequency of the S2 component is estimated using the filtered S2 component, a predetermined relationship is applied between the estimated maximum frequency and blood pressure to generate a blood pressure estimate and the blood pressure estimate is displayed.
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Citations
24 Claims
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1. A method for noninvasively estimating a blood pressure, the method comprising:
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a) applying a bandpass filter to a second heart sound (S2) component to generate a filtered S2 component, the bandpass filter having a lower cutoff frequency greater than a maximum frequency of the S2 component; b) estimating the maximum frequency of the S2 component using the filtered S2 component; c) applying a predetermined relationship between the estimated maximum frequency and blood pressure to generate a blood pressure estimate; and d) displaying the blood pressure estimate, wherein step (b) includes; (b1) calculating a ratio between the S2 component and the filtered S2 component; (b2) decreasing the lower cutoff frequency and repeating steps (a) and (b1) with the decreased lower cutoff frequency to calculate the ratio, the lower cutoff frequency being decreased until the calculated ratio is less than or equal to a predetermined threshold, and wherein the decreased lower cutoff frequency is used to define the estimated maximum frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. Apparatus for noninvasively estimating a blood pressure, the apparatus comprising:
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means for applying a bandpass filter to a second heart sound (S2) component to generate a filtered S2 component, the bandpass filter having a lower cutoff frequency greater than a maximum frequency of the S2 component; means for estimating the maximum frequency of the S2 component using the filtered S2 component; means for applying a predetermined relationship between the estimated maximum frequency and blood pressure to generate a blood pressure estimate; and means for displaying the blood pressure estimate, wherein the means for estimating the maximum frequency includes; means for calculating a ratio between the S2 component and the filtered S2 component; and means for decreasing the lower cutoff frequency of the bandpass filter responsive to the calculated ratio, wherein the lower cutoff frequency is decreased until the calculated ratio is less than or equal to a predetermined threshold, and wherein the decreased lower cutoff frequency is used to define the estimated maximum frequency. - View Dependent Claims (14, 15)
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16. A blood pressure analyzer for noninvasively estimating a blood pressure, the blood pressure analyzer comprising:
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a frequency estimator including; an estimator input port configured to receive a second heart sound (S2) component; a bandpass filter coupled to the estimator input port and configured to generate a filtered S2 component from the S2 component, the bandpass filter having a lower cutoff frequency greater than a maximum frequency of the S2 component, wherein the frequency estimator is configured to estimate the maximum frequency of the S2 component using the filtered S2 component; and a blood pressure estimator coupled to the frequency estimator and configured to apply a predetermined relationship between the estimated maximum frequency and blood pressure to generate a blood pressure estimate. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24)
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Specification