Pressure signal processing apparatus and method for an automatic blood pressure gauge

Claim 2

Apparatus suitable for use in an automatic blood pressure gauge having a fluid pressurized cuff, comprising: valve means, responsive to a periodic valve control signal having a predetermined nominal frequency, for controllably releasing the fluid from the pressurized cuff in accordance with a predetermined pressure reduction function; pressure measuring means, coupled to the pressurized cuff, for measuring the instantaneous pressure level of the fluid in the cuff, as the fluid is released from the cuff, to provide a pressure signal which includes a blood pressure pulse signal component; filtering means, having a notch filter frequency response characteristic, for filtering said pressure signal to selectively attenuate signals approximately equal in frequency to said periodic valve control signal to produce a filtered pressure signal; and means for processing the filtered pressure signal to separate the blood pressure pulse signal component therefrom.

Claim 3

The apparatus of claim 1 further including: a single timing source for providing both a sampling clock signal having a predetermined frequency and said periodic valve control signal; and means for sampling said pressure signal at instants determined by the sampling clock signal to generate a sampled data pressure signal for application to the filtering means; wherein said the frequency of said sampling clock signal is greater than twice the nominal frequency of the periodic valve control signal, wherein the sampled data pressure signal is substantially free of any aliasing components related to the periodic valve control signal.

Claim 4

The apparatus of claim 2 wherein the filtering means and the periodic valve control signal are both realized using a program that runs on a microprocessor which microprocessor is responsive to said single timing source and to said sampled data pressure signal.

Claim 5

The apparatus of claim 1 wherein the valve means includes first and second solenoid valves, wherein the first solenoid valve exhibits a rate of flow less than said second solenoid valve.

Claim 6

The apparatus of claim 4 wherein said valve means further includes means for selectively applying the periodic valve control signal to one of said first and second solenoid valves to achieve a rate of flow of fluid from the cuff which produces a reduction in the pressure of the cuff consistent with the predetermined pressure reduction function.

Claim 7

The apparatus of claim 5 wherein said means for selectively applying applies the periodic valve control signal to the first valve when a relatively low deflation flow is required and applies the periodic valve control signal to the second valve when a relatively high deflation flow is required.

Claim 8

Apparatus suitable for use in an automatic blood pressure gauge having a fluid pressurized cuff, comprising: valve means, responsive to a periodic valve control signal having a predetermined nominal frequency, for controllable releasing the fluid from the pressurized cuff in accordance with a predetermined pressure reduction function; pressure measuring means, coupled to the pressurized cuff, for measuring the instantaneous pressure level of the fluid in the cuff, as the fluid is released from the cuff, to provide a pressure signal which includes a blood pressure pulse signal component; a single timing source for providing both a sampling clock signal having a predetermined frequency and a periodic valve control signal having a predetermined frequency, wherein the frequency of the sampling clock signal is more than twice the frequency of the periodic valve control signal; means for sampling said pressure signal at instants determined by the sampling clock signal to generate a sampled data pressure signal, wherein said means for sampling said pressure signal includes a sigma-delta analog to digital converter having a low-pass filter characteristic that attenuates signals at the nominal frequency of the periodic valve control signal relative to signals in the band of frequencies occupied by the blood pressure pulse signal; filtering means for filtering said sampled data pressure signal to selectively attenuate signals approximately equal in frequency to said periodic valve control signal to produce a filtered pressure signal; and means for processing the filtered pressure signal to separate the blood pressure pulse signal component therefrom.

Claim 9

Apparatus suitable for use in an automatic blood pressure gauge having a fluid pressurized cuff, comprising: valve means, responsive to a periodic valve control signal having a predetermined nominal frequency, for controllable releasing the fluid from the pressurized cuff in accordance with a predetermined pressure reduction function; pressure measuring means, coupled to the pressurized cuff, for measuring the instantaneous pressure level of the fluid in the cuff, as the fluid is released from the cuff, to provide a pressure signal which includes a blood pressure pulse signal component; a single timing source for providing both a sampling clock signal having a predetermined frequency and a periodic valve control signal having a predetermined frequency, wherein the frequency of the sampling clock signal is more than twice the frequency of the periodic valve control signal; means for sampling said pressure signal at instants determined by the sampling clock signal to generate a sampled data pressure signal, wherein said means for sampling said pressure signal includes a sigma-delta analog to digital converter having a low-pass filter characteristic that attenuates signals at the nominal frequency of the periodic valve control signal relative to signals in the band of frequencies occupied by the blood pressure pulse signal; filtering means for filtering said sampled data pressure signal to selectively attenuate signals approximately equal in frequency to said periodic valve control signal to produce a filtered pressure signal; and means for processing the filtered pressure signal to separate the blood pressure pulse signal component therefrom.

Claim 10

Apparatus suitable for use in an automatic blood pressure gauge having a fluid pressurized cuff, comprising: valve means, responsive to a periodic valve control signal having a predetermined nominal frequency, for controllably releasing the fluid from the pressurized cuff in accordance with a predetermined pressure reduction function; pressure measuring means, coupled to the pressurized cuff, for measuring the instantaneous pressure level of the fluid in the cuff, as the fluid is released from the cuff, to provide a pressure signal which includes a blood pressure pulse signal component; a programmed microprocessor; a single timing source, including said programmed microprocessor, for providing both a sampling clock signal having a predetermined frequency and a periodic valve control signal having a predetermined nominal frequency, wherein the frequency of the sampling clock signal is more than twice the nominal frequency of the periodic valve control signal; means for sampling said pressure signal at instants determined by the sampling clock signal to generate a sampled data pressure signal; filtering means, including a third-order Chebychev-2 filter having a frequency response characteristic which has a zero at the nominal frequency of the periodic valve control signal implemented as a program that runs on the microprocessor, for filtering said sampled data pressure signal to selectively attenuate signals approximately equal in frequency to said periodic valve control signal to produce a filtered pressure signal; and means for processing the filtered pressure signal to separate the blood pressure pulse signal component therefrom.

Claim 11

Apparatus suitable for use in an automatic blood pressure gauge having a fluid pressurized cuff, comprising: valve means, responsive to a periodic valve control signal having a predetermined nominal frequency, for controllably releasing the fluid from the pressurized cuff in accordance with a predetermined pressure reduction function; pressure measuring means, coupled to the pressurized cuff, for measuring the instantaneous pressure level of the fluid in the cuff, as the fluid is released from the cuff, to provide a pressure signal which includes a blood pressure pulse signal component; a programmed microprocessor; a single timing source, including said programmed microprocessor, for providing both a sampling clock signal having a predetermined frequency and a periodic valve control signal having a predetermined nominal frequency, wherein the frequency of the sampling clock signal is more than twice the nominal frequency of the periodic valve control signal; means for sampling said pressure signal at instants determined by the sampling clock signal to generate a sampled data pressure signal; filtering means, including a third-order Chebychev-2 filter having a frequency response characteristic which has a zero at the nominal frequency of the periodic valve control signal implemented as a program that runs on the microprocessor, for filtering said sampled data pressure signal to selectively attenuate signals approximately equal in frequency to said periodic valve control signal to produce a filtered pressure signal; and means for processing the filtered pressure signal to separate the blood pressure pulse signal component therefrom.

Claim 14

The method of claim 9 further including the steps of: both sampling said pressure signal at instants determined by a sampling clock signal to generate a sampled data pressure signal prior to filtering the pressure signal and developing said periodic valve control signal, in response to a common clock signal source; wherein the frequency of the sampling clock signal is greater than twice the nominal frequency of the periodic valve control signal, wherein the sampled data pressure signal is substantially free of any aliasing components related to the periodic valve control signal.