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Claims  |
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What is claimed is:
1. For use in a non-invasive blood pressure monitoring system, a method of
estimating optimum arterial compression by measuring the stress of tissue
overlying an artery of interest, said system of the type including a
tissue stress sensor having a stress sensitive element, said stress
sensitive element having a length that exceeds the lumen of said artery of
interest, said method including the steps of:
(A) placing said stress sensitive element of said tissue stress sensor in
communication with said tissue overlying said artery of interest,
(B) orienting said stress sensitive element such that said length spans
beyond the lumen of said artery of interest,
(C) using said stress sensitive element to varyingly compress said artery
of interest thereby applanating said artery of interest through a
plurality of stages, and at each said applanation stage,
(D) obtaining from said tissue stress sensor at least one electrical signal
representing stress data across the length of said stress sensitive
element, said stress data including a plurality of stress datum, each
stress datum representing stress communicated to a predetermined portion
of said stress sensitive element from said tissue overlying said artery of
interest, each said predetermined portion of said stress sensitive element
lying along said length of said stress sensitive element, and for each
applanation stage, using said data for,
(E) computing a pulse parameter and an applanation state parameter,
(F) relating said pulse parameter to said applanation state parameter,
(G) determining the value of said applanation state parameter which
corresponds to a predetermined percentage of a maximum value of said pulse
parameter,
(H) estimating the optimum arterial compression to be that degree of artery
applanation which produces the applanation state parameter value of step
(G).
2. The method of claim 1, wherein step (E) includes computing said pulse
parameter as follows:
##EQU53##
where: b,c=limits of integration
.sigma..sub.PCS (x)=pulsatile contact stress as a function of x
x=distance along the stress sensitive diaphragm.
3. The method of claim 1, wherein said applanation state parameter is
computed as follows:
##EQU54##
where: .sigma..sub.DCSAVG =average diastolic stress across the length of
the stress sensitive element
L=length of stress sensitive element
.sigma..sub.DCS (x)=diastolic stress as a function of x
x=location along the stress sensitive element.
4. The method of claim 1, wherein said predetermined percentage is equal to
generally 95 percent.
5. The method of claim 1, wherein step (G) further includes the sub-steps
of,
(i) increasing arterial applanation until said pulse parameter reaches a
first maximum value, and then diminishes by a predetermined fraction of
said first maximum value, then
(ii) decreasing arterial applanation until said pulse parameter reaches a
second maximum value, then
(iii) continuing decreasing said arterial applanation until said pulsatile
parameter reaches generally 95 percent of said second maximum value.
6. The method of claim 2, wherein said limits of integration b,c are
computed by determining which portion of the stress sensitive element is
in receipt of a predetermined quantity of the stress energy imparted to
the stress sensitive element from said tissue overlying said artery of
interest.
7. For use in a non-invasive blood pressure monitoring system, a method of
estimating optimum arterial compression by measuring the stress of tissue
overlying an artery of interest, said system of the type including a
tissue stress sensor having a stress sensitive element, said stress
sensitive element having a length that exceeds the lumen of said artery of
interest, said method including the steps of:
(A) placing said stress sensitive element of said tissue stress sensor in
communication with said tissue overlying said artery of interest,
(B) orienting said stress sensitive element such that said length spans
beyond the lumen of said artery of interest,
(C) using said stress sensitive element to varyingly compress said artery
of interest thereby applanating said artery of interest through a
plurality of stages, and at each said applanation stage,
(D) obtaining from said tissue stress sensor at least one electrical signal
representing stress data across the length of said stress sensitive
element, said stress data including a plurality of stress datum, each
stress datum representing stress communicated to a predetermined portion
of said stress sensitive element from said tissue overlying said artery of
interest, each said predetermined portion of said stress sensitive element
lying along said length of said stress sensitive element, and for each
applanation stage, using said data for,
(E) computing a mean distribution breadth parameter and an applanation
state parameter,
(F) relating said mean distribution breadth parameter to said applanation
state parameter,
(G) determining the value of said applanation state parameter that
corresponds to a mean distribution breadth parameter approximately equal
to one,
(H) estimating the optimum arterial compression to be that degree of artery
applanation which produces the applanation state parameter value of step
(G).
8. The method of claim 7, wherein step (E) includes computing said mean
distribution breadth parameter as follows:
##EQU55##
where: L=length of stress sensitive element
b,c=limits of integration
.sigma..sub.MCS (x)=mean contact stress as a function of x
x=distance along length of stress sensitive element.
9. The method of claim 8, wherein said mean contact stress is computed as
follows:
##EQU56##
where: .tau.=time period of one heartbeat
n=the number of heartbeats selected for time averaging.
10. The method of claim 7, wherein said applanation state parameter is
computed as follows:
##EQU57##
where: .sigma..sub.DCSAVG =average diastolic stress across the length of
the stress sensitive element
L=length of stress sensitive element
.sigma..sub.DCS (x)=diastolic stress as a function of x
x=location along the stress sensitive element.
11. The method of claim 8, wherein said limits of integration b,c are
computed by determining which portion of the stress sensitive element is
in receipt of a predetermined quantity of the stress energy imparted to
the stress sensitive element from said tissue overlying said artery of
interest.
12. For use in a non-invasive blood pressure monitoring system, a method of
estimating optimum arterial compression by measuring the stress of tissue
overlying an artery of interest, said system of the type including a
tissue stress sensor having a stress sensitive element, said stress
sensitive element having a length that exceeds the lumen of said artery of
interest, said method including the steps of:
(A) placing said stress sensitive element of said tissue stress sensor in
communication with said tissue overlying said artery of interest,
(B) orienting said stress sensitive element such that said length spans
beyond the lumen of said artery of interest,
(C) using said stress sensitive element to varyingly compress said artery
of interest thereby applanating said artery of interest through a
plurality of stages, and at each said applanation stage,
(D) obtaining from said tissue stress sensor at least one electrical signal
representing stress data across the length of said stress sensitive
element, said stress data including a plurality of stress datum, each
stress datum representing stress communicated to a predetermined portion
of said stress sensitive element from said tissue overlying said artery of
interest, each said predetermined portion of said stress sensitive element
lying along said length of said stress sensitive element, and for each
applanation stage, using said data for,
(E) computing a diastolic distribution breadth parameter and an applanation
state parameter,
(F) relating said diastolic distribution breadth parameter to said
applanation state parameter,
(G) determining the value of said applanation state parameter that
corresponds to a diastolic distribution breadth parameter value
approximately equal to 1.05,
(H) estimating the optimal arterial compression to be that degree of artery
applanation which produces the applanation state parameter value of step
(G).
13. The method of claim 12, wherein step (E) includes computing said
diastolic distribution breadth parameter as follows:
##EQU58##
where: L=length of stress sensitive element
b,c=limits of integration
.sigma..sub.DCS (x)=mean contact stress as a function of x
x=distance along length of stress sensitive element.
14. The method of claim 12, wherein said applanation state parameter is
computed as follows:
##EQU59##
where: .sigma..sub.DCSAVG =average diastolic stress across the length of
the stress sensitive element
L=length of stress sensitive element
.sigma..sub.DCS (x)=diastolic stress as a function of x
x=location along the stress sensitive element.
15. The method of claim 13, wherein said limits of integration b,c are
computed by determining which portion of the stress sensitive element is
in receipt of a predetermined quantity of the stress energy imparted to
the stress sensitive element from said tissue overlying said artery of
interest.
16. For use in a non-invasive blood pressure monitoring system, a method of
estimating optimum arterial compression by measuring the stress of tissue
overlying an artery of interest, said system of the type including a
tissue stress sensor having a stress sensitive element, said stress
sensitive element having a length that exceeds the lumen of said artery of
interest, said method including the steps of:
(A) placing said stress sensitive element of said tissue stress sensor in
communication with said tissue overlying said artery of interest,
(B) orienting said stress sensitive element such that said length spans
beyond the lumen of said artery of interest,
(C) using said stress sensitive element to varyingly compress said artery
of interest thereby applanating said artery of interest through a
plurality of stages, and at each said applanation stage,
(D) obtaining from said tissue stress sensor at least one electrical signal
representing stress data across the length of said stress sensitive
element, said stress data including a plurality of stress datum, each
stress datum representing stress communicated to a predetermined portion
of said stress sensitive element from said tissue overlying said artery of
interest, each said predetermined portion of said stress sensitive element
lying along said length of said stress sensitive element, and for each
applanation stage, using said data for,
(E) computing a pulse distribution breadth parameter and an applanation
state parameter,
(F) relating said pulse distribution breadth parameter to said applanation
state parameter,
(G) determining a maximum value of said pulse distribution breadth
parameter and the corresponding applanation state parameter value,
(H) selecting a range of applanation state parameter values occurring at
applanation stages of less applanation than the applanation state
corresponding to the maximum pulse distribution breadth parameter value of
step (G),
(I) determining a mid-point value in the range selected in step (H),
(J) determining the optimum arterial compression to be that degree of
arterial applanation which produces the applanation state parameter
mid-point value of step (I).
17. The method of claim 16, wherein step (E) includes computing said pulse
distribution breadth parameter as follows:
##EQU60##
where: W.sub.TH =cumulative width at .sigma..sub.PCSTHR
.sigma..sub.PCSTHR =predetermined threshold value of pulsatile contact
stress
b,c=limits of integration.
18. The method of claim 17, wherein two or more pulse distribution breadth
parameter values are computed using respectively associated predetermined
threshold values of pulsatile contact stress, wherein an overall pulse
distribution breadth parameter value is derived by mathematically
combining said two or more pulse distribution breadth parameter values.
19. The method of claim 16, wherein said applanation state parameter is
computed as follows:
##EQU61##
where: .sigma..sub.DCSAVG =average diastolic stress across the length of
the stress sensitive element
L=length of stress sensitive element
.sigma..sub.DCS (x)=diastolic stress as a function of x
x=location along the stress sensitive element.
20. The method of claim 17, wherein said limits of integration b,c are
computed by determining which portion of the stress sensitive element is
in receipt of a predetermined quantity of the stress energy imparted to
the stress sensitive element from said tissue overlying said artery of
interest.
21. For use in a non-invasive blood pressure monitoring system, a method of
estimating optimum arterial compression by measuring the stress of tissue
overlying an artery of interest, said system of the type including a
tissue stress sensor having a stress sensitive element, said stress
sensitive element having a length that exceeds the lumen of said artery of
interest, said method including the steps of:
(A) placing said stress sensitive element of said tissue stress sensor in
communication with said tissue overlying said artery of interest,
(B) orienting said stress sensitive element such that said length spans
beyond the lumen of said artery of interest,
(C) using said stress sensitive element to varyingly compress said artery
of interest thereby applanating said artery of interest through a
plurality of stages, and at each said applanation stage,
(D) obtaining from said tissue stress sensor at least one electrical signal
representing stress data across the length of said stress sensitive
element, said stress data including a plurality of stress datum, each
stress datum representing stress communicated to a predetermined portion
of said stress sensitive element from said tissue overlying said artery of
interest, each said predetermined portion of said stress sensitive element
lying along said length of said stress sensitive element, and for each
applanation stage, using said data for,
(E) computing a pulse distribution breadth parameter, an applanation state
parameter, and a change in pulse distribution breadth parameter with
respect to the applanation state parameter,
(F) relating said change in said pulse distribution breadth parameter to
said applanation state parameter,
(G) determining the value of said applanation state parameter that
corresponds to a maximum value of said pulse distribution breadth
parameter,
(H) estimating the optimum arterial compression to be that degree of
arterial applanation which produces the applanation state parameter value
of step (G).
22. The method of claim 21, wherein step (E) includes computing said pulse
distribution breadth parameter as follows:
##EQU62##
where: W.sub.TH =cumulative width at .sigma..sub.PCSTHR
.sigma..sub.PCSTHR =predetermined threshold value of pulsatile contact
stress
b,c limits of integration.
23. The method of claim 22, wherein step (E) includes computing said change
in said pulse distribution breadth parameter as follows:
.DELTA.PDBP(i)=W.sub.TH (i)-W.sub.TH (i+1)
where:
.DELTA.PDBP(i)=change in pulse distribution breadth parameter for the ith
applanation state
W.sub.TH (i)=cumulative width at .sigma..sub.PCSTHR for the ith applanation
state
W.sub.TH (i+1)=cumulative width at .sigma..sub.PCSTHR for the i+1
applanation state
i=a given applanation state.
24. The method of claim 21, wherein said applanation state parameter is
computed as follows:
##EQU63##
where: .sigma..sub.DCSAVG =average diastolic stress across the length of
the stress sensitive element
L=length of stress sensitive element
.sigma..sub.DCS (x)=diastolic stress as a function of x
x=location along the stress sensitive element.
25. The method of claim 22, wherein said limits of integration b,c are
computed by determining which portion of the stress sensitive element is
in receipt of a predetermined quantity of the stress energy imparted to
the stress sensitive element from said tissue overlying said artery of
interest.
26. For use in a non-invasive blood pressure monitoring system, a method of
estimating optimum arterial compression by measuring the stress of tissue
overlying an artery of interest, said system of the type including a
tissue stress sensor having a stress sensitive element, said stress
sensitive element having a length that exceeds the lumen of said artery of
interest, said method including the steps of:
(A) placing said stress sensitive element of said tissue stress sensor in
communication with said tissue overlying said artery of interest,
(B) orienting said stress sensitive element such that said length spans
beyond the lumen of said artery of interest,
(C) using said stress sensitive element to varyingly compress said artery
of interest thereby applanating said artery of interest through a
plurality of stages, and at each said applanation stage,
(D) obtaining from said tissue stress sensor at least one electrical signal
representing stress data across the length of said stress sensitive
element, said stress data including a plurality of stress datum, each
stress datum representing stress communicated to a predetermined portion
of said stress sensitive element from said tissue overlying said artery of
interest, each said predetermined portion of said stress sensitive element
lying along said length of said stress sensitive element, and for each
applanation stage, using said data for,
(E) computing a pulse spread parameter, an applanation state parameter, and
the derivative of the pulse spread parameter with respect to the
applanation state parameter,
(F) relating said derivative of said pulse spread parameter to said
applanation state parameter,
(G) determining the value of said applanation state parameter that
corresponds to a maximum value of said derivative of said pulse spread
parameter,
(H) estimating the optimum arterial compression to be that degree of
arterial applanation which produces the applanation state parameter of
step (G).
27. The method of claim 26, wherein step (E) includes computing said pulse
spread parameter as follows:
PSP=.sigma..sub.PCSMAX -.sigma..sub.PCSENG
where:
.sigma..sub.PCSENG =.sigma..sub.PCSB or .sigma..sub.PCSc, which ever is the
lesser
.sigma..sub.PCSMAX =Maximum pulsatile contact stress value for a given
applanation state
.sigma..sub.PCSb, .sigma..sub.PCSc =points along .sigma..sub.PCS (x) which
intersect region bounded by b,c.
28. The method of claim 26, wherein said applanation state parameter is
computed as follows:
##EQU64##
where: .sigma..sub.DCSAVG =average diastolic stress across the length of
the stress sensitive element
L=length of stress sensitive element
.sigma..sub.DCS (x)=diastolic stress as a function of x
x=location along the stress sensitive element.
29. The method of claim 27, wherein said limits of integration b,c are
computed by determining which portion of the stress sensitive element is
in receipt of a predetermined quantity of the stress energy imparted to
the stress sensitive element from said tissue overlying said artery of
interest.
30. For use in a non-invasive blood pressure monitoring system, a method of
estimating optimum arterial compression by measuring the stress of tissue
overlying an artery of interest, said system of the type including a
tissue stress sensor having a stress sensitive element, said stress
sensitive element having a length that exceeds the lumen of said artery of
interest, said method including the steps of:
(A) placing said stress sensitive element of said tissue stress sensor in
communication with said tissue overlying said artery of interest,
(B) orienting said stress sensitive element such that said length spans
beyond the lumen of said artery of interest,
(C) using said stress sensitive element to varyingly compress said artery
of interest thereby applanating said artery of interest through a
plurality of stages, and at each said applanation stage,
(D) obtaining from said tissue stress sensor at least one electrical signal
representing stress data across the length of said stress sensitive
element, said stress data including a plurality of stress datum, each
stress datum representing stress communicated to a predetermined portion
of said stress sensitive element from said tissue overlying said artery of
interest, each said predetermined portion of said stress sensitive element
lying along said length of said stress sensitive element, and for each
applanation stage, using said data for,
(E) computing a pulse distribution breadth parameter, an applanation state
parameter, and a derivative of said pulse distribution breadth parameter
with respect to said applanation state parameter,
(F) relating said derivative of said pulse distribution breadth parameter
to said applanation state parameter,
(G) determining the value of said applanation state parameter that
corresponds to a maximum value of said derivative of said pulse
distribution breadth parameter,
(H) estimating the optimum arterial compression to be that degree of
arterial applanation which produces the applanation state parameter value
of step (G).
31. The method of claim 30, wherein step (E) includes computing said pulse
spread parameter as follows:
##EQU65##
where: W.sub.TH =cumulative width at threshold .sigma..sub.PCSTHR along
normalized plot of pulsatile contact stress .sigma..sub.PCSNOR (x)
b,c=limits of integration defined by 60 percent of .sigma..sub.PCSMAX.
32. The method of claim 30, wherein said applanation state parameter is
computed as follows:
##EQU66##
where: .sigma..sub.DCSAVG =average diastolic stress across the length of
the stress sensitive element
L=length of stress sensitive element
.sigma..sub.DCS (x)=diastolic stress as a function of x
x=location along the stress sensitive element.
33. For use in a non-invasive blood pressure monitoring system, a method of
estimating optimum arterial compression by measuring the stress of tissue
overlying an artery of interest, said system of the type including a
tissue stress sensor having a stress sensitive element, said stress
sensitive element having a length that exceeds the lumen of said artery of
interest, said method including the steps of:
(A) placing said stress sensitive element of said tissue stress sensor in
communication with said tissue overlying said artery of interest,
(B) orienting said stress sensitive element such that said length spans
beyond the lumen of said artery of interest,
(C) using said stress sensitive element to varyingly compress said artery
of interest thereby applanating said artery of interest through a
plurality of stages, and at each said applanation stage,
(D) obtaining from said tissue stress sensor at least one electrical signal
representing stress data across the length of said stress sensitive
element, said stress data including a plurality of stress datum, each
stress datum representing stress communicated to a predetermined portion
of said stress sensitive element from said tissue overlying said artery of
interest, each said predetermined portion of said stress sensitive element
lying along said length of said stress sensitive element, and for each
applanation stage, using said data for,
(E) computing a diastolic distribution breadth parameter, an applanation
state parameter, and a derivative of said diastolic distribution breadth
parameter with respect to the applanation state parameter,
(F) relating a derivative of the diastolic distribution breadth parameter
to the applanation state parameter,
(G) determining the value of said applanation state parameter that
corresponds to a maximum of said derivative of said diastolic distribution
breadth parameter,
(H) estimating the optimum arterial compression to be that degree of artery
applanation which produces the applanation state parameter value of step
(G).
34. The method of claim 33, wherein step (E) includes computing said
diastolic distribution breadth parameter as follows:
##EQU67##
where: L=length of stress sensitive element
b,c=limits of integration
.sigma..sub.DCS (x)=mean contact stress as a function of x
x=distance along length of stress sensitive element.
35. The method of claim 33, wherein said applanation state parameter is
computed as follows:
##EQU68##
where: .sigma..sub.DCSAVG =average diastolic stress across the length of
the stress sensitive element
L=length of stress sensitive element
.sigma..sub.DCS (x)=diastolic stress as a function of x
x=location along the stress sensitive element.
36. The method of claim 34, wherein said limits of integration b,c are
computed by determining which portion of the stress sensitive element is
in receipt of a predetermined quantity of the stress energy imparted to
the stress sensitive element from said tissue overlying said artery of
interest.
37. For use in a non-invasive blood pressure monitoring system, a method of
estimating optimum arterial compression by measuring the stress of tissue
overlying an artery of interest, said system of the type including a
tissue stress sensor having a stress sensitive element, said stress
sensitive element having a length that exceeds the lumen of said artery of
interest, said method including the steps of:
(A) placing said stress sensitive element of said tissue stress sensor in
communication with said tissue overlying said artery of interest,
(B) orienting said stress sensitive element such that said length spans
beyond the lumen of said artery of interest,
(C) using said stress sensitive element to varyingly compress said artery
of interest thereby applanating said artery of interest through a
plurality of stages, and at each said applanation stage,
(D) obtaining from said tissue stress sensor at least one electrical signal
representing stress data across the length of said stress sensitive
element, said stress data including a plurality of stress datum, each
stress datum representing stress communicated to a predetermined portion
of said stress sensitive element from said tissue overlying said artery of
interest, each said predetermined portion of said stress sensitive element
lying along said length of said stress sensitive element, and for each
applanation stage, using said data for,
(E) computing a spatially averaged stress parameter, an applanation state
parameter, and a second derivative of said spatially averaged stress
parameter with respect to the applanation state parameter,
(F) relating the second derivative of the spatially averaged stress
parameter to the applanation state parameter,
(G) determining the value of said applanation state parameter that
corresponds to a minimum value of said second derivative of said spatially
averaged stress parameter,
(H) estimating the optimum arterial compression to be that degree of artery
applanation which produces the applanation state parameter value of step
(G).
38. The method of claim 37, wherein step (E) includes computing said
spatially averaged stress parameter as follows:
##EQU69##
where: b,c=limits of integration
x=distance along the stress sensitive diaphragm
.sigma.(x)=stress sensed along stress sensitive element as a function of x.
39. The method of claim 38, wherein .sigma.(x) is selected from the group
of .sigma..sub.DCS (x), .sigma..sub.SCS (x), .sigma..sub.MCS (x), and
.sigma..sub.PCS (x) where:
.sigma..sub.DCS (x)=diastolic contact stress as a function of x,
.sigma..sub.SCS (x)=systolic contact stress as a function of x,
.sigma..sub.MCS (x)=mean contact stress as a function of x,
.sigma..sub.PCS (x)=pulsatile contact stress as a function of x.
40. The method of claim 38, wherein .sigma.(x) is selected from the group
of F(.sigma..sub.DCS (x)), F(.sigma..sub.SCS (x)), F(.sigma..sub.MCS (x)),
and F(.sigma..sub.PCS (x)) where:
F(.sigma..sub.DCS (x))=weighted function of diastolic contact stress,
F(.sigma..sub.SCS (x))=weighted function of systolic contact stress,
F(.sigma..sub.MCS (x))=weighted function of mean contact stress,
F(.sigma..sub.PCS (x))=weighted function of pulsatile contact stress.
41. The method of claim 37, wherein said applanation state parameter is
computed as follows:
##EQU70##
where: .sigma..sub.DCSAVG =average diastolic stress across the length of
the stress sensitive element
L=length of stress sensitive element
.sigma..sub.DCS (x)=diastolic stress as a function of x
x=location along the stress sensitive element.
42. The method of claim 38, wherein said limits of integration b,c are
computed by determining which portion of the stress sensitive element is
in receipt of a predetermined quantity of the stress energy imparted to
the stress sensitive element from said tissue overlying said artery of
interest.
43. For use in a non-invasive blood pressure monitoring system, a method of
estimating optimum arterial compression by measuring the stress of tissue
overlying an artery of interest, said system of the type including a
tissue stress sensor having a stress sensitive element, said stress
sensitive element having a length that exceeds the lumen of said artery of
interest, said method including the steps of:
(A) placing said stress sensitive element of said tissue stress sensor in
communication with said tissue overlying said artery of interest,
(B) orienting said stress sensitive element such that said length spans
beyond the lumen of said artery of interest,
(C) using said stress sensitive element to varyingly compress said artery
of interest thereby applanating said artery of interest through a
plurality of stages, and at each said applanation stage,
(D) obtaining from said tissue stress sensor at least one electrical signal
representing stress data across the length of said stress sensitive
element, said stress data including a plurality of stress datum, each
stress datum representing stress communicated to a predetermined portion
of said stress sensitive element from said tissue overlying said artery of
interest, each said predetermined portion of said stress sensitive element
lying along said length of said stress sensitive element, and for each
applanation stage, using said data for,
(E) computing a stress spatial curvature parameter, an applanation state
parameter, and a derivative of said stress spatial curvature parameter
with respect to the applanation state parameter,
(F) relating the derivative of the stress spatial curvature parameter to
the applanation state parameter,
(G) determining a maximum of said derivative of said stress spatial
curvature parameter,
(H) estimating the optimum arterial compression to be that degree of artery
applanation which produces the applanation state parameter value of step
(G).
44. The method of claim 43, wherein step (E) includes computing said stress
spatial curvature parameter as follows: where:
##EQU71##
x=center of pulsatily active region of stress sensitive element x=distance
along length of stress sensitive element
.sigma.(x)=stress sensed along stress sensitive element as a function of x.
45. The method of claim 44, wherein .sigma.(x) is selected from the group
of .sigma..sub.DCS (x), .sigma..sub.SCS (x), .sigma..sub.MCS (x), and
.sigma..sub.PCS (x) where:
.sigma..sub.DCS (x)=diastolic contact stress as a function of x,
.sigma..sub.SCS (x)=systolic contact stress as a function of x,
.sigma..sub.MCS (x)=mean contact stress as a function of x,
.sigma..sub.PCS (x)=pulsatile contact stress as a function of x.
46. The method of claim 44, wherein .sigma.(x) is selected from the groups
of F(.sigma..sub.DCS (x)), F(.sigma..sub.SCS (x)), F(.sigma..sub.MCS (x)),
and F(.sigma..sub.PCS (x)) where:
F(.sigma..sub.DCS (x))=weighted function of diastolic contact stress,
F(.sigma..sub.SCS (x))=weighted function of systolic contact stress,
F(.sigma..sub.MCS (x))=weighted function of mean contact stress,
F(.sigma..sub.PCS (x))=weighted function of pulsatile contact stress.
47. The method of claim 44, wherein step (E) includes computing x as
follows:
##EQU72##
where: b,c=limits of integration
x=distance along the stress sensitive diaphragm
.sigma.(x)=stress sensed along stress sensitive element as a function of x.
48. The method of claim 47, wherein said limits of integration b,c are
computed by determining which portion of the stress sensitive element is
in receipt of a predetermined quantity of the stress energy imparted to
the stress sensitive element from said tissue overlying said artery of
interest.
49. The method of claim 43, wherein said applanation state parameter is
computed as follows:
##EQU73##
where: .sigma..sub.DCSAVG =average diastolic stress across the length of
the stress sensitive element
L=length of stress sensitive element
.sigma..sub.DCS (x)=diastolic stress as a function of x
x=location along the stress sensitive element.
50. For use in a non-invasive blood pressure monitoring system, a method of
estimating optimum arterial compression by measuring the stress of tissue
overlying an artery of interest, said system of the type including a
tissue stress sensor having a stress sensitive element, said stress
sensitive element having a length that exceeds the lumen of said artery of
interest, said method including the steps of:
(A) placing said stress sensitive element of said tissue stress sensor in
communication with said tissue overlying said artery of interest,
(B) orienting said stress sensitive element such that said length spans
beyond the lumen of said artery of interest,
(C) using said stress sensitive element to varyingly compress said artery
of interest thereby applanating said artery of interest through a
plurality of stages, and at each said applanation stage,
(D) obtaining from said tissue stress sensor at least one electrical signal
representing stress data across the length of said stress sensitive
element, said stress data including a plurality of stress datum, each
stress datum representing stress communicated to a predetermined portion
of said stress sensitive element from said tissue overlying said artery of
interest, each said predetermined portion of said stress sensitive element
lying along said length of said stress sensitive element, and for each
applanation stage, using said data for,
(E) computing a stress variation parameter, an applanation state parameter,
and a derivative of said stress variation parameter with respect to the
applanation state parameter,
(F) relating the derivative of the stress variation parameter to the
applanation state parameter,
(G) determining a minimum of said derivative stress variation parameter,
(H) estimating the optimum arterial compression to be that degree of artery
applanation which produces the applanation state parameter value of step
(G).
51. The method of claim 50, wherein step (E) includes computing said stress
variation parameter as follows:
SVPAR=.sigma..sub.MAX -.sigma..sub.MIN
where:
.sigma..sub.MAX =maximum stress occurring along .sigma.(x) in region of
stress sensitive element receiving highest pulse energy
.sigma..sub.MIN =minimum stress occurring along .sigma.(x) in region of
stress sensitive element receiving highest pulse energy
x=distance along length of stress sensitive element
.sigma.(x)=stress sensed along stress sensitive element as a function of x.
52. The method of claim 51, wherein .sigma.(x) is selected from the groups
of .sigma..sub.DCS (x), .sigma..sub.SCS (x), .sigma..sub.MCS (x), and
.sigma..sub.PCS (x) where:
.sigma..sub.DCS (x)=diastolic contact stress as a function of x,
.sigma..sub.SCS (x)=systolic contact stress as a function of x,
.sigma..sub.MCS (x)=mean contact stress as a function of x,
.sigma..sub.PCS (x)=pulsatile contact stress as a function of x.
53. The method of claim 50, wherein step (E) includes computing said stress
variation parameter as follows:
SVPAR=SD(.sigma.(x))
where:
SD=standard deviation operation
.sigma.(x)=contact stress occurring in region of stress sensitive element
receiving highest pulse energy
x=distance along length of stress sensitive element.
54. The method of claim 53, wherein .sigma.(x) is selected from the groups
of .sigma..sub.DCS (x), .sigma..sub.SCS (x), .sigma..sub.MCS (x), and
.sigma..sub.PCS (x) where:
.sigma..sub.DCS (x)=diastolic contact stress as a function of x,
.sigma..sub.SCS (x)=systolic contact stress as a function of x,
.sigma..sub.MCS (x)=mean contact stress as a function of x,
.sigma..sub.PCS (x)=pulsatile contact stress as a function of x.
55. The method of claim 51, wherein said region of said stress sensitive
element receiving the highest pulse energy is defined by bounding limits
b,c, and wherein bounding limits b,c are computed by determining which
portion of the stress sensitive element is in receipt of a predetermined
quantity of the stress energy imparted to the stress sensitive element
from said tissue overlying said artery of interest.
56. The method of claim 50, wherein said applanation state parameter is
computed as follows:
##EQU74##
where: .sigma..sub.DCSAVG =average diastolic stress across the length of
the stress sensitive element
L=length of stress sensitive element
.sigma..sub.DCS (x)=diastolic stress as a function of x
x=location along the stress sensitive element.
57. For use in a non-invasive blood pressure monitoring system, a method of
estimating optimum arterial compression by measuring the stress of tissue
overlying an artery of interest, said system of the type including a
tissue stress sensor having a stress sensitive element, said stress
sensitive element having a length that exceeds the lumen of said artery of
interest, said method including the steps of:
(A) placing said stress sensitive element of said tissue stress sensor in
communication with said tissue overlying said artery of interest,
(B) orienting said stress sensitive element such that said length spans
beyond the lumen of said artery of interest,
(C) using said stress sensitive element to varyingly compress said artery
of interest thereby applanating said artery of interest through a
plurality of stages, and at each said applanation stage,
(D) obtaining from said tissue stress sensor at least one electrical signal
representing stress data across the length of said stress sensitive
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