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Claims  |
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What is claimed is:
1. A method of monitoring certain blood pressure parameters of a patient
including his systolic and diastolic pressures over an extended period of
time by taking successive measurements at closely spaced intervals
throughout said period, said method comprising the steps of:
(a) Taking an initial measurement at the beginning of said period by
(i) positioning a pressurizable blood pressure cuff or pad at the
appropriate location adjacent a suitable artery of the patient,
(ii) maintaining said cuff or pad at different pressure levels including
levels at and above the anticipated diastolic and systolic pressures of
the patient,
(iii) producing cuff pulses corresponding to said different pressure
levels,
(iv) from said cuff pulses, determining the diastolic and systolic
pressures of the patient, and
(v) from said cuff pulses and the diastolic and systolic pressures of the
patient, generating a transformation curve unique to the patient; and
(b) taking at least one subsequent measurement during said extended period
while said cuff or pad is still in position adjacent said artery by
(i) maintaining said cuff or pad at different pressure levels including
levels at and above the anticipated diastolic pressure of the patient but
below the patient's systolic pressure, as determined by said initial
measurement,
(ii) producing cuff pulses corresponding to these last mentioned pressure
levels,
(iii) from said last mentioned cuff pulses, determining the patient's
diastolic pressure, and
(iv) from said last mentioned cuff pulses, the patient's diastolic pressure
and from his transformation curve generated during said initial
measurement, determining the patient's systolic pressure.
2. A method according to claim 1 wherein said subsequent measurement is
successively repeated a plurality of times after said initial measurement
is taken at spaced intervals throughout said extended period, whereby the
systolic pressure of the patient is monitored throughout said period
without having to pressurize the blood pressure cuff or pad to a level at
or above the patient's systolic pressure except during said initial
measurement.
3. A method according to claim 2 wherein, during each of said subsequent
measurements, said cuff or pad is maintained at an uppermost level which
is only somewhat greater than the patient's diastolic level, whereby to
minimize the pressure the patient is subjected to.
4. A method according to claim 3 wherein, during each of said initial and
subsequent measurements, said cuff or pad is successively maintained at
increasing ones of said different pressure levels as the cuff or pad is
pressurized from ambient pressure and then depressurized to ambient
pressure upon reaching the highest pressure level required by the
particular measurement.
5. A method according to claim 4 wherein, during each of said measurement,
said cuff or pad is pressurized from ambient pressure to its highest level
in a linear manner.
6. A method according to claim 3 wherein, during each of said initial and
subsequent measurements, said cuff or pad means is first pressurized to
the highest pressure level required by that particular measurement and
then depressurized toward ambient pressure during which the cuff or pad is
successively maintained at decreasing ones of said different pressure
levels.
7. A method according to claim 6 wherein, during each of said measurements,
said cuff or pad is depressurizing from said highest level to a level just
below the diastolic pressure of the patient in a linear manner.
8. A method according to claim 2 wherein each of said measurements includes
generating a blood pressure-like curve corresponding to the patient's
actual blood pressure versus time curve from the diastolic and systolic
pressures of the patient and his initially generated transformation curve
and thereafter calculating the patient's mean pressure from his blood
pressure-like curve during that measurement.
9. A method according to claim 8 including the step of recording, either
temporarily or permanently, the diastolic, mean and systolic pressures of
the patient during each of said measurements.
10. A method according to claim 1 wherein the patient's systolic pressure
is determined during said subsequent measurement by (i) selecting at least
one cuff pulse produced during said subsequent measurement, (ii) using the
diastolic pressure of the patient determined during said subsequent
measurement, locating the base and peak of said selected cuff pulse on the
vertical axis of the patient's transformation curve, and (iii) from the
peak point of said selected cuff pulse on the vertical axis of said
transformation curve, using the latter curve, locating the systolic
pressure of said patient.
11. An apparatus for monitoring certain blood pressure parameters of a
patient including his systolic and diastolic pressures over an extended
period of time by taking successive measurements at closely spaced
intervals throughout said period, said apparatus comprising:
(a) means for taking an initial measurement at the beginning of said
period, said initial measurement taking means including
(i) a pressurizable blood pressure cuff or pad positionable at the
appropriate location adjacent a suitable artery of the patient,
(ii) means for maintaining said cuff or pad at different pressure levels
including levels at and above the anticipated diastolic and systolic
pressures of the patient,
(iii) means of producing cuff pulses corresponding to said different
pressure levels,
(iv) means for determining the diastolic and systolic pressures of the
patient from said cuff pulses, and
(v) means for generating a transformation curve unique to the patient from
said cuff pulses and the diastolic and systolic pressures of the patient;
and
(b) means for taking at least one subsequent measurement during said
extended period while said cuff or pad is still in position adjacent said
artery, said subsequent measurement taking means including
(i) means for maintaining said cuff or pad at different pressure levels
including levels at and above the anticipated diastolic pressure of the
patient but below the patient's systolic pressure, as determined by said
initial measurement,
(ii) means for producing cuff pulses corresponding to these last mentioned
pressure levels,
(iii) means for determining the patient's diastolic pressure from said last
mentioned cuff pulses, and
(iv) means for determining the patient's systolic pressure from said last
mentioned cuff pulses, the patient's diastolic pressure and from his
transformation curve, generated during said initial measurement.
12. An apparatus according to claim 11 wherein said subsequent measurement
taking means successively repeats said subsequent measurements a plurality
of times after said initial measurement is taken at spaced intervals
throughout said extended period, whereby the systolic pressure of the
patient is monitored throughout said period without having to pressurize
the blood pressure cuff or pad to a level at or above the patient's
systolic pressure except during said initial measurement.
13. An apparatus according to claim 12 including means for generating a
blood pressure-like curve corresponding to the patient's actual blood
pressure versus time curve from the diastolic and systolic pressures of
the patient and his initially generated transformation curve during each
of said measurements and thereafter calculating the patient's means
pressure from his blood pressure-like curve during that measurement.
14. An apparatus according to claim 13 including means for recording,
either temporarily or permanently, the diastolic, mean and systolic
pressures of the patient during each of said measurements.
15. A method of monitoring certain blood pressure parameters of a patient
including his systolic and diastolic pressures over an extended period of
time by taking successive measurements at closely spaced intervals
throughout said period, said method comprising the steps of:
(a) taking an initial measurement in which cuff pulses of the patient are
generated at different pressure levels including levels at and above the
anticipated diastolic and systolic levels of the patient and, from these
cuff pulses, the patient's diastolic and systolic pressures are determined
and, from these diastolic and systolic pressures and cuff pulses, a
transformation curve unique to the patient is generated; and
(b) taking at least one subsequent measurement during said period in which
cuff pulses of the patient are generated at different pressure levels
including levels at and above the anticipated diastolic level of the
patient but always below the systolic pressure of the patient as
determined by the initial measurement and, from these latter cuff pulses,
the patient's diastolic pressure is determined and, from this latter
pressure, these latter cuff pulses and the transformation curve generated
by the initial measurement, determining the systolic pressure of the
patient.
16. A method according to claim 15 wherein said subsequent measurement is
successively repeated a plurality of times after said initial measurement
is taken at spaced intervals throughout said extended period, whereby the
systolic pressure of the patient is monitored throughout said period
without having to generate cuff pulses at levels at or above the patient's
systolic pressure except during said initial measurement.
17. An apparatus for monitoring certain blood pressure parameters of a
patient including his systolic and diastolic pressures over an extended
period of time by taking successive measurements at closely spaced
intervals throughout said period, said apparatus comprising: means for
taking an initial measurement in which cuff pulses of the patient are
generated at different pressure levels including levels at and above the
anticipated diastolic and systolic levels of the patient and, from these
cuff pulses, the patient's diastolic and systolic pressures are determined
and, from these diastolic and systolic pressures and cuff pulses, a
transformation curve unique to the patient is generated and for taking at
least one subsequent measurement during said period in which cuff pulses
of the patient are generated at different pressure levels including levels
at and above the anticipated diastolic level of the patient but always
below the systolic pressure o the patient as determined by the initial
measurement and, from these latter cuff pulses, the patient's diastolic
pressure is determined and, from this latter pressure, these latter cuff
pulses and the transformation curve generated by the initial measurement,
determining the systolic pressure of the patient.
18. A method of obtaining certain blood pressure parameters of a given
patient including his systolic and diastolic pressures, comprising the
steps of:
(a) positioning a blood pressure cuff or pad at the appropriate location
adjacent a suitable artery of the patient,
(b) selecting first and second points in time t.sub.1 and t.sub.2 on the
diastolic decline or systolic rise of the patient's actual blood pressure
waveform below the patient's anticipated systolic pressure;
(c) placing said cuff or pad at different pressure levels including levels
above and below the anticipated blood pressures of the patient at the
selected points in time t.sub.1 and t.sub.2 on his actual waveform; and
thereby producing cuff pulses at said different pressure levels;
(d) from said cuff pulses, measuring the change in cuff pressure .DELTA.P
at each of said different levels of cuff pressure for relatively narrow
first and second intervals of time .DELTA.t.sub.1 and .DELTA.t.sub.2
containing times t.sub.1 and t.sub.2, respectively, on the patient's
actual blood pressure waveform;
(e) generating a transformation curve unique to said patient from at least
some of said measurements;
(f) determining the actual blood pressures D.sub.1 and D.sub.2 of the
patient at times t.sub.1 and t.sub.2, respectively, on the patient's
waveform from said measurements;
(g) selecting a cuff pulse at one of said different levels of cuff pressure
and, using said transformation curve and said actual blood pressures,
D.sub.1 and D.sub.2, establishing the positional relationship between said
transformation curve and selected cuff pulse and the correct scaling of
the latter relative to said transformation curve; and
(h) from said correctly scaled cuff pulse and from its positional
relationship with said transformation curve, determining the systolic
pressure of the patient and his diastolic pressure, if the latter is not
blood pressure D.sub.1 or D.sub.2.
19. A method according to claim 18 wherein the first point in time t.sub.1
is selected to be in close proximity to the beginning of the systolic rise
portion of the patient's actual blood pressure waveform, whereby D.sub.1
corresponds nearly to the patient's diastolic pressure.
20. A method according to claim 18 wherein said transformation curve is
generated by integrating over time the measurements .DELTA.P at each of
said different levels of cuff pressure for only one of said intervals of
time .DELTA.t.sub.1 and .DELTA.t.sub.2.
21. A method according to claim 18 wherein said transformation curve is
generated by integrating over time the measurements .DELTA.P at each of
said different levels of cuff pressure for each of said intervals of time
.DELTA.t.sub.1 and .DELTA.t.sub.2 and averaging the integrated
measurements at each pressure level to produce an averaged transformation
curve.
22. A method according to claim 18 including the step of determining the
blood pressures of said patient at a sufficient number of points in time
other than t.sub.1 and t.sub.2 from said correctly scaled cuff pulse and
from its positional relationship with said transformation curve to
reproduce the actual blood pressure waveform of said patient.
23. A method according to claim 18 wherein said steps (a)-(h) are repeated
at spaced-apart intervals over an extended period of time whereby to
monitor the patient's diastolic and systolic blood pressures over said
period of time.
24. An apparatus for obtaining certain blood pressure parameters of a given
patient including his systolic and diastolic pressures, comprising:
(a) a blood pressure cuff or pad positioned at the appropriate location
adjacent a suitable artery of the patient,
(b) means for placing said cuff at different pressure levels including
levels below the anticipated systolic pressure of the patient but
including levels above and below the anticipated blood pressures of the
patient at selected first and second points in time t.sub.1 and t.sub.2 on
the diastolic decline or systolic rise of his actual blood pressure
waveform; and thereby producing cuff pulses at said different pressure
levels;
(c) means responsive to said cuff pulse for measuring the change in cuff
pressure .DELTA.P at each of said different levels of cuff pressure for
relatively narrow first and second intervals of time .DELTA.t.sub.1 and
.DELTA.t.sub.2 containing times t.sub.1 and t.sub.2, respectively, on the
diastolic decline of the patient's actual blood pressure waveform;
(d) means for generating a transformation curve unique to said patient from
at least some of said measurements;
(e) means of determining the actual blood pressures D.sub.1 and D.sub.2 of
the patient at times t.sub.1 and t.sub.2, respectively, on the patient's
waveform from said measurements;
(f) means responsive to a selected one of said cuff pulses, said
transformation curve and said actual blood pressures, D.sub.1 and D.sub.2
for establishing the positional relationship between said transformation
curve and selected cuff pulse and the correct scaling of the latter
relative to said transformation curve; and
(g) means responsive to said correctly scaled cuff pulse and its positional
relationship with said transformation curve for determining the systolic
pressure of the patient and his diastolic pressure if the latter is not
blood pressure D.sub.1 or D.sub.2.
25. An apparatus according to claim 24 wherein the first point in time
t.sub.1 is selected to be in close proximity to the beginning of the
systolic rise portion of the patient's actual blood pressure waveform,
whereby D.sub.1 corresponds nearly to the patient's diastolic pressure.
26. An apparatus according to claim 24 wherein said transformation curve
generating means includes means for integrating over time the measurements
.DELTA.P at each of said different levels of cuff pressure for only one of
said intervals of time .DELTA.t.sub.1 and .DELTA.t.sub.2.
27. An apparatus according to claim 24 wherein said transformation curve
generating means includes means for integrating over time the measurements
.DELTA.P at each of said different levels of cuff pressure for each of
said intervals of time .DELTA.t.sub.1 and .DELTA.t.sub.2 and means for
averaging the integrated measurements at each pressure level to produce an
averaged transformation curve.
28. An apparatus according to claim 24 including means for determining the
blood pressures of said patient at a sufficient number of points in time
other than t.sub.1 and t.sub.2 from said correctly scaled cuff pulse and
from its positional relationship with said transformation curve to
reproduce the actual blood pressure waveform of said patient.
29. A method of obtaining certain blood pressure parameters of a given
patient including his systolic and diastolic pressures, comprising the
steps of:
(a) positioning a blood pressure cuff or pad at the appropriate location
adjacent a suitable artery of the patient;
(b) selecting first and second points in time t.sub.1 and t.sub.2 on the
patient's actual blood pressure waveform below the patient's anticipated
systolic pressure;
(c) placing said cuff or pad at different pressure levels including levels
above and below the anticipated blood pressures of the patient at the
selected points in time t.sub.1 and t.sub.2 on his actual waveform, and
thereby producing cuff pulses at said different pressure levels;
(d) from said cuff pulses, measuring the change in cuff pressure .DELTA.P
at each of said different levels of cuff pressure for relatively narrow
first and second intervals of time .DELTA.t.sub.1 and .DELTA.t.sub.2
containing times t.sub.1 and t.sub.2, respectively, on the patient's
actual blood pressure waveform;
(e) generating a transformation curve unique to said patient at least some
of said measurements;
(f) determining the actual blood pressures D.sub.1 and D.sub.2 of the
patient at times t.sub.1 and t.sub.2, respectively, on the patient's
waveform from said measurements;
(g) selecting a cuff pulse at one of said different levels of cuff pressure
and, using said transformation curve and said actual blood pressures,
D.sub.1 and D.sub.2, establishing the positional relationship between said
transformation curve and selected cuff pulse and the correct scaling of
the latter relative to said transformation curve; and
(h) from said correctly scaled cuff pulse and from its positional
relationship with said transformation curve, determining the systolic
pressure of the patient and his diastolic pressure, if the latter is not
blood pressure D.sub.1 or D.sub.2.
30. A method according to claim 29 wherein said points in time t.sub.1 and
t.sub.2 lie on the diastolic decline of said patient's blood pressure
waveform.
31. A method according to claim 29 wherein said points in time t.sub.1 and
t.sub.2 lie on the systolic rise of said patient's waveform.
32. An apparatus for obtaining certain blood pressure parameters of a given
patient including his systolic and diastolic pressures, comprising:
(a) a blood pressure cuff or pad positioned at the appropriate location
adjacent a suitable artery of the patient,
(b) means for placing said cuff at different pressure levels below the
anticipated systolic pressure of the patient but including levels above
and below the anticipated blood pressures of that patient at selected
first and second points in time t.sub.1 and t.sub.2 on his actual blood
pressure waveform, and thereby producing cuff pulses at said different
pressure levels;
(c) means responsive to said cuff pulses for measuring the change in cuff
pressure .DELTA.P at each of said different levels of cuff pressure for
relatively narrow first and second intervals of time .DELTA.t.sub.1 and
.DELTA.t.sub.2 containing times t.sub.1 and t.sub.2, respectively, on the
diastolic decline of the patient's actual blood pressure waveform;
(d) means for generating a transformation curve unique to said patient from
at least some of said measurements;
(e) means of determining the actual blood pressures D.sub.1 and D.sub.2 of
the patient at times from said measurements;
(f) means responsive to a selected one of said cuff pulses, said
transformation curve and said actual blood pressures D.sub.1 and D.sub.2
for establishing the positional relationship between said transformation
curve and selected cuff pulse and the correct scaling of the latter
relative to said transformation curve; and
(g) means responsive to said correctly scaled cuff pulse and its positional
relationship with said transformation curve for determining the systolic
pressure of the patient and his diastolic pressure if the latter is not
blood pressure D.sub.1 or D.sub.2 1.
33. A method of obtaining certain blood pressure parameters of a given
patient including his systolic and diastolic pressures, comprising the
steps of:
(a) positioning a blood pressure cuff or pad at the appropriate location
adjacent a suitable artery of the patient,
(b) selecting first and second points in time t.sub.1 and t.sub.2 on the
patient's actual blood pressure waveform below the patient's anticipated
systolic pressure;
(c) placing said cuff or pad at different pressure levels including levels
above and below the anticipated blood pressures of the patient at the
selected points in time t.sub.1 and t.sub.2 on his actual waveform, and
thereby producing cuff pulses at said different pressure levels,
(d) from said cuff pulses, measuring the change in cuff pressure .DELTA.P
at each of said different levels of cuff pressure for relatively narrow
first and second intervals of time .DELTA.t.sub.1 and .DELTA.t.sub.2
containing times t.sub.1 and t.sub.2, respectively, on the patient's
actual blood pressure waveform;
(e) from said cuff pulses and cuff pressures .DELTA.P, generating
information sufficient to provide the patient's systolic pressure; and
(f) from said information determining the patient's systolic pressure.
34. An apparatus for obtaining certain blood pressure parameters of a given
patient including his systolic and diastolic pressures, comprising:
(a) a blood pressure cuff or pad positioned at the appropriate location
adjacent a suitable artery of the patient;
(b) means for placing said cuff at different pressure levels below the
anticipated systolic pressure of the patient but including levels above
and below the anticipated blood pressures of the patient at selected first
and second points in time t.sub.1 and t.sub.2 on his actual blood pressure
waveform, and thereby producing cuff pulses at said different pressure
levels;
(c) means responsive to said cuff pulses for measuring the change in cuff
pressure .DELTA.P at each of said different levels of cuff pressure for
relatively narrow first and second intervals of time .DELTA.t.sub.1 and
.DELTA.t.sub.2 containing times t.sub.1 and t.sub.2, respectively, on the
diastolic decline of the patient's actual blood pressure waveform;
(d) means responsive to said cuff pulses and said cuff pressures .DELTA.P
for generating information sufficient to provide the patient's systolic
pressure; and
(e) means responsive to said information to determine the patient's
systolic pressure. |
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Claims |
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Description |
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The present invention relates generally to blood pressure evaluation
procedures and more particularly to non-invasive techniques for
determining certain information associated with blood pressure.
The most reliable ways presently known for obtaining information relating
to an individual's blood pressure require invasive procedures. Such
procedures are not carried out routinely but only under extreme
circumstances, for example during heart surgery. Under less critical
conditions, blood pressure information including specifically an
individual's systolic (maximum) and diastolic (minimum) blood pressures is
obtained non-invasively. There are two well known non-invasive techniques
presently being used today, one is commonly referred to as auscultation
and the other is based on oscillometry. Both of these non-invasive
techniques use the standard arm cuff which most people are familiar with.
However, in the auscultatory method, the systolic and diastolic pressures
are determined by listening to certain sounds (Korotkoff sounds) which
occur as a result of the cuff first being pressurized and then
depressurized whereas oscillometry actually measures changes in pressure
in the cuff as a result of changes in blood pressure as the cuff is first
pressurized and then depressurized.
As will be seen hereinafter, the various embodiments of the present
invention are based on oscillometry. In order to more fully appreciate
these embodiments, reference is made to applicant's own U.S. Pat. No.
3,903,872 (the Link patent) for obtaining blood pressure information
non-invasively. This patent which is incorporated herein by reference
describes, among other things, a way of obtaining the diastolic pressure
of an individual in accordance with a technique which will be discussed in
more detail hereinafter. In U.S. Pat. Nos. 4,009,709 and 4,074,711 (Link
et al) which are also incorporated herein by reference, non-invasive
techniques using oscillometry are disclosed for obtaining the systolic
pressure of an individual. These techniques will also be discussed
hereinafter.
While the various procedures described in the Link and Link et al patents
just recited and other patents held by applicant are satisfactory for
their intended purposes, it is an object of the present invention to
provide additional uncomplicated and yet reliable techniques for obtaining
different types of information relating to an individual's blood pressure.
A more specific object of the present invention is to provide a different
uncomplicated and yet reliable technique for generating non-invasively a
waveform closely approximating an individual's true blood pressure
waveform which, heretofore, has been obtainable by invasive means only.
Another particular object of the present invention is to provide a new way
for measuring and calculating the mean arterial pressure of an individual.
Another specific object of the present invention is to provide a new,
uncomplicated and yet reliable technique for generating a transformation
curve unique to a given patient.
Still another specific object of the present invention is to provide a
technique for successively monitoring certain parameters of a patient's
blood pressure including his systolic and diastolic pressures over closely
spaced intervals of time without having to subject the patient to cuff
pressures much greater than his diastolic pressure, other than initially
(for purposes of calibration).
Yet another specific object of the present invention is to provide a
technique for measuring a patient's diastolic and systolic blood pressures
at any given instance without ever having to subject the patient to cuff
pressures much greater than his diastolic pressure.
As will be described in more detail hereinafter, the objects just recited
are achieved by means of oscillometry. In accordance with this technique,
a suitably sized cuff, for example one which is 20 inches long and 5
inches wide, is positioned around the upper arm of an individual, a human
being specifically or a mammal in general (hereinafter referred to as the
patient) and initially pressurized to a certain minimum level. As will be
seen hereinafter in accordance with one aspect of the present invention,
this minimum level need not be much greater than the patient's diastolic
pressure to obtain certain information about the patient's blood pressure
including his diastolic and systolic pressures. However, heretofore, in
order to measure these pressure values and obtain other information, it
was necessary to subject the patient to a minimum cuff pressure greater
than the patient's systolic pressure, for example 180 Torr. It is assumed
that this latter cuff pressure will cause the patient's artery within the
sleeve to completely collapse. Thereafter, the cuff pressure is gradually
reduced toward zero during which time the cuff continuously changes in
pressure in an oscillating fashion due to the combination of (1) the
internal blood pressure changes in the patient's artery and (2) changes in
cuff pressure. The latter at any given time in the procedure is known and
oscillatory changes in cuff pressure can be readily measured, for example
with an oscilloscope. By using these two parameters in conjunction with
information which may be made available from methods disclosed in the
above-recited U.S. patents and the techniques of the present invention to
be described hereinafter, it is possible to achieve the foregoing
objectives in uncomplicated and reliable ways.
It should be noted at the outset that the typical 5" wide pressure cuff
entirely surrounds a corresponding 5" length of artery. The tissue of the
arm is for the most part incompressible, and therefore any change in the
volume of the artery, caused for example by pulsations of blood, results
in a corresponding change in the volume of air in the air bladder which is
within the cuff and therefore adjacent to the arm. This change in air
volume produces a small but accurately measurable pressure change in the
air. This equivalence of pressure pulsations in the cuff bladder to volume
pulsations of the artery is the essence of oscillometry.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to more fully appreciate the various techniques of the present
invention, the following more detailed background information is provided
in conjunction with FIGS. 1-5 of the drawings where:
FIG. 1 (corresponding to FIG. 6 in U.S. Pat. No. 3,903,872)
diagrammatically illustrates the shapes of successive cuff pressure versus
time pulses (cuff pulses) as the measured cuff pressure changes from 90
Torr to 80 Torr to 70 Torr, assuming the patient has a diastolic pressure
of 80 Torr.
FIG. 1A diagrammatically illustrates a full series of cuff pulses
corresponding to those in FIG. 1 from a cuff pressure of 160 Torr to a
cuff pressure of zero.
FIG. 2 diagrammatically illustrates what may be best referred to as a
"transformation" curve or a volume/pressure (V/P) curve corresponding to
the patient's arterial volume (V), that is, the volume of the patient's
artery within the cuff (as measured by cuff volume) versus wall pressure
(P.sub.w) across the artery wall within the cuff and, superimposed on this
curve, a curve which is intended to correspond to the actual blood
pressure waveform of a patient, the two curves being provided together in
order to illustrate the principles of oscillometry, as relied upon in the
above-recited patents. As will be described below, arterial volume changes
.DELTA.V produce cuff pulses P.sub.c (ac) and so FIG. 2 also represents a
curve which "transforms" blood pressure pulses into cuff pulses.
FIGS. 3 and 4 diagrammatically illustrate the transformation curve of FIG.
2 in ways which display techniques for obtaining a given patient's
systolic and diastolic blood pressures in accordance with the Link and
Link et al patents recieted above.
FIG. 5 diagrammatically illustrates a curve corresponding to the compliance
of the patient's artery, that is, a curve which displays the ratio
.DELTA.V/.DELTA.P.sub.w against the arterial wall pressure P.sub.w, where
.DELTA.V is the incremental change in the arterial volume corresponding to
a preselected change in wall pressure .DELTA.P.sub.w for different cuff
pressures, this latter curve being initially determined in order to
provide the transformation curve (V/P curve) of FIG. 2 by means of
integration, as will be seen. Because arterial volume changes produce cuff
pulses, FIG. 5 also represents the relationship .sup..DELTA. P.sub.c
(ac)/.sup..DELTA. P.sub.w.
FIG. 6 diagrammatically illustrates an actual blood pressure pulse for a
given patient.
FIG. 7 diagrammatically illustrates a plotted wavefrom which approximates
the actual blood pressure pulse of FIG. 6 and which is generated
non-invasively in accordance with the present invention.
FIG. 8 diagrammatically illustrates a transformation curve similar to the
one illustrated in FIGS. 2-4 but exaggerated along the vertical slope with
enlarged portions of the diastolic decline forming part of an actual blood
pressure waveform superimposed thereon.
FIGS. 9(a)-(d) diagrammatically illustrates four blood pressure waveforms
having different blood pressure constants K.
FIG. 10 is a functional illustration of an arrangement for providing a
curve which clearly approximates a patient's actual blood pressure
waveform and also provides the patients mean pressure and blood pressure
constant.
FIG. 11 graphically displays the peak to peak amplitude A of various cuff
pulses of FIG. 1A against cuff pressur | | |
