US4774960A — Method and apparatus for measuring blood pressure

Claim 1

Independent Claim 139 words

In an oscillometric blood pressure measuring apparatus of the type measuring pulsatile perturbations in a patient's blood pressure at a plurality of different measurement pressures of a sphygmomanometer cuff, to derive a blood pressure model for the patient, the model being stored in the apparatus as a series of pulsatile perturbations together with the associated cuff pressures, the improvement comprising: means operative on the stored model for generating a characteristic curve approximating the stored model in the vicinity of a predefined index value of cuff pressure; means for maintaining the pressure of said cuff within a predetermined range, r, of said index value; and means jointly responsive to said characteristic curve and to the magnitude of sensed pulsatile perturbations in said cuff pressure for tracking changes in said index value, to estimate a new value for said index value.

Claim 2

Dependent Claim 139 words

In an oscillometric blood pressure measuring apparatus of the type measuring pulsatile perturbations in a patient's blood pressure at a plurality of different measurement pressures of a sphygmomanometer cuff, to derive a blood pressure model for the patient, the model being stored in the apparatus as a series of pulsatile perturbations together with the associated cuff pressures, the improvement comprising: means operative on the stored model for generating a characteristic curve approximating the stored model in the vicinity of a predefined index value of cuff pressure; means for maintaining the pressure of said cuff within a predetermined range, r, of said index value; and means jointly responsive to said characteristic curve and to the magnitude of sensed pulsatile perturbations in said cuff pressure for tracking changes in said index value, to estimate a new value for said index value.

Claim 3

Dependent Claim 45 words

Apparatus in accordance with claim 1, wherein said generating means includes means for measuring the amount of time since the derivation of the blood pressure model and means for causing the derivation of a new model when said amount of time exceeds a predetermined value.

Claim 4

Dependent Claim 39 words

Apparatus in accordance with claim 1, wherein said generating means includes means for testing the accuracy of a newly generated characteristic curve, the newly generated curve being adopted as the characteristic curve only if it passes the accuracy test.

Claim 5

Dependent Claim 56 words

Apparatus in accordance with claim 3, wherein said means for testing includes means for producing a smoothed blood pressure model, and means jointly responsive to said smoothed blood pressure model and said characteristic curve for comparing the same and rejecting the characteristic curve when it differs from the smoothed blood pressure model to a predefined extent.

Claim 6

Dependent Claim 45 words

Apparatus in accordance with claim 4 wherein said means for producing a smoothed blood pressure model includes means for averaging each measured pulsatile perturbation of a blood pressure model with the perturbations stored immediately prior and subsequent thereto to derive said smoothed blood pressure model.

Claim 7

Dependent Claim 52 words

Apparatus in accordance with claim 1, wherein the index value is the systolic value and said generating means produces a curve which is a straight line providing a least-squares fit to those points in the blood pressure model which correspond to a cuff pressure between the systolic value and the means pressure.

Claim 8

Dependent Claim 80 words

Apparatus in accordance with claim 6, wherein said generating means generates said characteristic curve as a straight line defined by the following formula: H=LSTSLP * (P.sub.CUFF -P.sub.REF)+LSTINT where H is the height of the pulsatile perturbation, LSTSLP is the slope of the characteristic curve, P CUFF is the pressure of the cuff, P REF is the cuff pressure corresponding to the index value, and LSTINT is the intercept of the characteristic curve with the line defined by the equation: pressure=systolic-5.

Claim 9

Dependent Claim 30 words

Apparatus in accordance with claim 7, wherein said tracking means estimates the current pressure corresponding to the systolic value by means of a variable TEMP determined by the equation: ##EQU2##

Claim 10

Dependent Claim 115 words

Apparatus in accordance with claim 7, wherein said generating means includes means for testing the accuracy of a newly generated characteristic curve, the newly generated curve being adopted as the characteristic curve only if it passes the accuracy test, a prior characteristic curve being adopted otherwise, said means for testing including means for averaging each measured pulsatile perturbation of a blood pressure model with the perturbations stored immediately prior and subsequent thereto to derive a smoothed blood pressure model, and means jointly responsive to said smoothed blood pressure model and said characteristic curve for comparing the same and rejecting the characteristic curve when it differs from the smoothed blood pressure model to a predefined extent.

Claim 11

Dependent Claim 29 words

Apparatus in accordance with claim 1, wherein said maintaining means maintains said cuff pressure within a range, r, of a pressure which is 5 mmHg below the index value.

Claim 12

Dependent Claim 15 words

Apparatus in accordance with claim 10, wherein said range is plus or minus 5 mmHg.

Claim 13

Dependent Claim 18 words

Apparatus in accordance with claim 1, further comprising means for periodically deflating said cuff to substantially zero pressure.

Claim 14

Dependent Claim 34 words

Apparatus in accordance with claim 12, further comprising means for retaining said cuff in its deflated condition for a predetermined period of time, and means for thereafter restoring said cuff to its inflated condition.

Claim 15

Dependent Claim 32 words

Apparatus in accordance with claim 1, wherein said tracking means produces estimates of the index value by applying a value corresponding to the height of sensed pulsatile perturbations to the characteristic curve.

Claim 16

Dependent Claim 34 words

Apparatus in accordance with claim 14, wherein said tracking means produces a new estimate for the pressure corresponding to the systolic value by averaging the variable TEMP with at least one previous estimate therefor.

Claim 17

Dependent Claim 59 words

Apparatus in accordance with claim 15, further comprising means for displaying at least the pressure corresponding to the index characteristic value, first disabling means for disabling updating of said display means until at least two estimates of TEMP have been derived subsequent to deflation of said cuff in the process of maintaining the pressure thereof within said predetermined range.

Claim 18

Dependent Claim 46 words

Apparatus in accordance with claim 16, further comprising second disabling means for disabling updating of said display means until at least three estimates of TEMP have been derived subsequent to inflation of said cuff in the process of maintaining the pressure thereof within said predetermined range.

Claim 19

Dependent Claim 59 words

Apparatus in accordance with claim 15, further comprising means for displaying at least the pressure corresponding to the index characteristic value, and disabling means for disabling updating of said display means until at least three estimates of TEMP have been derived subsequent to inflation of said cuff in the process of maintaining the pressure thereof within said predetermined range.

Claim 20

Independent Claim 140 words

A method for use in an oscillometric blood pressure measuring apparatus of the type measuring pulsatile perturbations in a patient's blood pressure at a plurality of different measurement pressures of a sphygmomanometer cuff, to derive a blood pressure model for the patient, the model being stored in the apparatus as a series of pulsatile perturbations and the associated cuff pressures, the method comprising the steps of: generating a characteristic curve approximating the stored model in the vicinity of a predefined index value of cuff pressure; maintaining the pressure of said cuff within a predetermined range, r, of said index value; and tracking changes in said index value by sensing a pulsatile perturbation in said cuff pressure, deriving the corresponding value for cuff pressure from said characteristic curve, and utilizing the derived pressure as a new estimate for the index value.

Claim 21

Independent Claim 140 words

A method for use in an oscillometric blood pressure measuring apparatus of the type measuring pulsatile perturbations in a patient's blood pressure at a plurality of different measurement pressures of a sphygmomanometer cuff, to derive a blood pressure model for the patient, the model being stored in the apparatus as a series of pulsatile perturbations and the associated cuff pressures, the method comprising the steps of: generating a characteristic curve approximating the stored model in the vicinity of a predefined index value of cuff pressure; maintaining the pressure of said cuff within a predetermined range, r, of said index value; and tracking changes in said index value by sensing a pulsatile perturbation in said cuff pressure, deriving the corresponding value for cuff pressure from said characteristic curve, and utilizing the derived pressure as a new estimate for the index value.

Claim 22

Dependent Claim 40 words

The method of claim 19, wherein said generating step includes measuring the amount of time since the derivation of the blood pressure model and initiating the derivation of a new model when said amount of time exceeds a predetermined value.

Claim 23

Dependent Claim 36 words

The method of claim 19, wherein said generating step includes testing the accuracy of a newly generated characteristic curve, and adopting the newly generated curve as the characteristic curve only if it passes the accuracy test.

Claim 24

Dependent Claim 45 words

The method of claim 21, wherein said testing step includes producing a smoothed blood pressure model, and comparing said smoothed blood pressure model and said characteristic curve and rejecting the characteristic curve when it differs from the smoothed blood pressure model to a predefined extent.

Claim 25

Dependent Claim 44 words

The method of claim 22, wherein said step of producing a smoothed blood pressure model includes the steps of averaging each measured pulsatile perturbation of a blood pressure model with the perturbations immediately prior and subsequent thereto to derive said smoothed blood pressure model.

Claim 26

Dependent Claim 47 words

The method of claim 19, wherein the index value is the systolic value and said generating step produces a straight line providing a least-squares fit to those points in the blood pressure model which correspond to a cuff pressure between the systolic value and the mean pressure.

Claim 27

Dependent Claim 74 words

The method of claim 24, wherein said generating step utilizes the following formula for the characteristic curve: H=LSTSLP * (P.sub.CUFF -P.sub.REF)+LSTINT where H is the height of a pulsatile perturbation, LSTSLP is the slope of the characteristic curve, P CUFF is the pressure of the cuff, P REF is the cuff pressure corresponding to the index value, and LSTINT is the intercept of the characteristic curve with the line defined by the equation: pressure=systolic-5.

Claim 28

Dependent Claim 30 words

The method of claim 25, wherein said tracking step comprises estimating the current pressure corresponding to the systolic value by means of a variable TEMP determined by the equation: ##EQU3##

Claim 29

Dependent Claim 34 words

The method of claim 26, wherein said tracking step comprises producing a new estimate for the pressure corresponding to the systolic value by averaging the variable TEMP with at least one previous estimate therefor.

Claim 30

Dependent Claim 100 words

The method of claim 19, wherein said generating step includes testing the accuracy of a newly generated characteristic curve, and adopting the newly generated curve as the characteristic curve only if it passes the accuracy test, a prior characteristic curve being adopted otherwise, said testing step including averaging each measured pulsatile perturbation of a blood pressure model with the perturbations immediately prior and subsequent thereto to derive a smoothed blood pressure model, comparing said smoothed blood pressure model and said characteristic curve and rejecting the characteristic curve when it differs from the smoothed blood pressure model to a predefined extent.

Claim 31

Dependent Claim 26 words

The method of claim 19, wherein said cuff pressure is maintained within a range, r, of a pressure which is 5 mmHg below the index value.

Claim 32

Dependent Claim 14 words

The method of claim 29, wherein said range is plus or minus 5 mmHg.

Claim 33

Dependent Claim 15 words

The method of claim 19, further comprising periodically deflating said cuff to substantially zero pressure.

Claim 34

Dependent Claim 29 words

The method of claim 31, further comprising retaining said cuff in its deflated condition for a predetermined period of time, and thereafter restoring said cuff to its inflated condition.

Claim 35

Dependent Claim 35 words

The method of claim 19, wherein said tracking step comprises applying a value corresponding to the height of sensed pulsatile perturbations to the characteristic curve and deriving thereform a new estimate for the index value.

Claim 36

Dependent Claim 63 words

The method of claim 19, performed in an apparatus including means for displaying at least the pressure corresponding to the index value, said method further comprising the step of disabling updating of said display means until at least two estimates of TEMP have been derived subsequent to deflation of said cuff in the process of maintaining the pressure thereof within said predetermined range.

Claim 37

Dependent Claim 41 words

The method of claim 34, further comprising disabling updating of said display means until at least three estimates of TEMP have been derived subsequent to inflation of said cuff in the process of maintaining the pressure thereof within said predetermined range.

Claim 38

Dependent Claim 63 words

The method of claim 19, performed in an apparatus including means for displaying at least the pressure corresponding to the index value, said method further comprising the step of disabling updating of said display means until at least three estimates of TEMP have been derived subsequent to inflation of said cuff in the process of maintaining the pressure thereof within said predetermined range.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1991-10-04	1992-04-04	1992-10-04	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1995-10-04	1996-04-04	1996-10-04	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1999-10-04	2000-04-04	2000-10-04	$7700.00	Window Closed / Lapsed

Method and apparatus for measuring blood pressure

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