|Publication number||USRE33834 E|
|Application number||US 07/556,101|
|Publication date||Mar 3, 1992|
|Filing date||Jul 20, 1990|
|Priority date||May 10, 1984|
|Publication number||07556101, 556101, US RE33834 E, US RE33834E, US-E-RE33834, USRE33834 E, USRE33834E|
|Original Assignee||Sylvia Warner, Priyamvada Sankar|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (3), Referenced by (8), Classifications (14), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
P.sub.si =P.sub.mi +(1-g.sub.0)P.sub. pi
P.sub.si =P.sub.mi +(1-g.sub.i)P.sub. pi
P.sub.si =P.sub.mi +(1-g.sub.0)P.sub. pi
P.sub.si =P.sub.mi +(1-g.sub.i)P.sub. pi
This .Iadd.application is a reissue of application Ser. No. 105,803, filed Oct. 8, 1987, now U.S. Pat. No. 4,834,107, which .Iaddend.application is a continuation-in-part application Ser. No. 059,520, filed June 8, .Iadd.now abandoned .Iaddend. which is a continuation-in-part application Ser. No. 807,693, filed Dec. 11, 1985, now abandoned which is a continuation-in-part of parent application Ser. No. 608,955, filed May 10, 1984, now all abandoned.
1. Field of the Invention
The invention relates to a non-invasive method of measuring arterial blood pressure and cardiac output. The invention also relates to an apparatus for carrying out the method.
2. Description of Prior Art
Non-invasive methods and apparatus for measuring arterial blood pressure and cardiac output are known in the art. Once such method and apparatus is illustrated in U.S. Pat. No. 4,030,485, Warner, issued June 21, 1977. A second such method and apparatus is taught in U.S. Pat. No. 4,418,700, Warner, issued Dec. 6, 1983. The present invention constitutes an improvement and refinement of the method and apparatus as taught in the latter patent.
The invention relates to a non-invasive method, and an apparatus for determining heart-related parameters in patients. The method and apparatus determine pulse pressure, time constant of the arterial system, systolic and diastolic pressure, peripheral resistance, and cardiac output and means arterial blood pressure.
The invention will be better understood by an examination of the following description together with the accompanying drawings in which:
FIG. 1 is a block diagram of the apparatus for carrying out the inventive method;
FIG. 2 is a typical sensor output of the system as illustrated in FIG. 1;
FIG. 3 illustrates arterial blood pressure pulses;
FIGS. 4, 4a and 4b illustrate a blood volume pulse;
FIG. 5 illustrates a blood volume pulse and a blood pressure pulse to illustrate the ratio g; and
FIG. 6 is a simplified flowchart for a computer program for performing calculations in accordance with the invention.
As seen in FIG. 1, an apparatus in accordance with the invention comprises a volume sensor such as a photo-electric plethysmograph S, an amplifier A1, an analog to digital converter A2, a microcomputer M and a display device D. The plethysmograph sensor S is attached to, for example, the earlobe of a subject. The sensor could also be attached to other suitable parts of the body such as the forehead, fingertips or toes.
As is known, the plethysmograph, detects changes in blood volume of the region to which it is attached. A typical sensor output signal is shown in FIG. 2. As seen in FIG. 2, the output signal has a pulsating component and a DC component.
The output of the sensor is applied to the plethysmograph amplifier A1 where it is amplified and filtered and the DC component is discarded. The output of A1 has a DC component, but this is not directly related to the sensor DC component.
The output of A1 is fed to the analog to digital (A/D) converter A2 which digitizes the signal. In a preferred embodiment, the sampling rate is 100 per second.
Microcomputer M accepts signals from A2 and processes them according to the instructions it contains. These instructions are schematically represented in the simplified flowchart of FIG. 6.
The computer quantities are then displayed on a CRT monitor D or other suitable display means.
Arterial blood pressure pulses are shown in FIG. 3. The shape of these curves vary according to the site where they are measured. The highest pressure reached during a cycle i is called the arterial systolic blood pressure, Psi. The lowest pressure reached during the same cycle is called the arterial diastolic blood pressure, Pdi. The pressure rise from Pdi to psi in the same cycle is the pulse pressure, ppi.
p.sub.si -p.sub.di =p.sub.pi (1)
To find Ppi
A plethysmographic pulse is shown in FIG. 4. The minimum value at the beginning of the pulse is Vimin. The maximum value of the pulse is Vimax. As the pulse volume rises from Vimin to Vimax, the time rate of volume change reaches a maximum Vimax at time tiVm. The pulse volume at time tiVm is ViVm.
In addition to finding the values of ViVm corresponding to Vimax, see U.S. Pat. No. 4,418,700, Warner, values of ViVm are also found corresponding to Vimax -1, Vimax -2, . . . Vimax -k, where k is a function of Vimax.
All of the values of ViVm corresponding to the time rates of volume change lying between and including Vimax and vimax -k are averaged and used to compute ΔViVm.
The average value of ViV m is ##EQU2## where n0=number of values of ViV.sbsb.0 m corresponding to Vimax ##EQU3## nk=number of values of ViV.sbsb.k m corresponding to Vimax -k
k=(Vimax/m) (integral values only)+1
m=constant . . . a preferred value of m=20
l=constant . . . a preferred value of l=1 ##EQU4## Kpp =constant determined by a first calibration r1 =constant . . . preferably equal to 0
r2 =constant . . . preferably equal to 0
Ri1 can now be defined, as per equation (2) above, but using the average value of ViVm so that equation (2) can be rewritten ##EQU5##
From FIG. 4 ##EQU6## wherein
No other calibration should be required with different subjects. However, if desired, Kpp can be determined for each subject.
To find mean blood pressure
The mean blood pressure Pmi during a cycle i is given by ##EQU7## b3 =exponent . . . the preferred value of b3 is equal to 0.5 K4 =constant determined at calibration for each subject. It is only necessary to find this constant once for each subject. The measurements carried out at different times on the same subject do not require separate calibration
P0 =constant . . . preferred 25 mmHg ##EQU8## where gi =(ΔViAV /ΔVi)
ΔViAV =average value of ΔVi over the time interval Ti
P.sub.di =P.sub.si -P.sub.pi (8)
The variable gi can take on a constant value g0 whose preferred value is 0.333.
Alternatively, mean blood pressure can be determined using the following expression: ##EQU9## (for definition of ri see Equation 10 below); where
G(t)=a function of t, in a particular case,
.[.Tc =T at calibration.]. .Iadd.Δtc =Δt at calibration Δt'iφ (see FIG. 4B) .Iaddend.
.[.tc =t at calibration Δt'iφ.sbsb.c (see FIG. 4B).].
.[.φc =(Tc /tc)=(T/t) at calibration.]. .Iadd.φc =(1/Δt)y at calibration.Iaddend.
The remainder of the terms in equation 5' are the same as similar terms in equation 5.
Determination of ratio R (FIG. 4b)
From FIG. 4b, the ratio R is
Ri =(ΔVit /ΔVi)
ΔVit =change in volume at predetermined time ti
ΔVi =total volume change during cycle i
ti =time such that Δti =KT Δt'iφ
Estimation of pulse pressure, PP ##EQU10## where PPi =pulse pressure=ps -Pd
Ps =systolic blood pressure
Pd =diastolic blood pressure
K'T =constant ≃ KT
In FIG. 4B
Δ V'.sub.i =ΔV.sub.i -ΔV.sub.it ##EQU11## wherein from the above equation: ##EQU12## multiply numerator and denominator by e.sup.kPP i ##EQU13##
Determination of r
From FIG. 4
r.sub.i = (V.sub.imax /ΔV.sub.i)G(t)
Vimax =maximum time rate of volume increase in cycle i
ΔVi =total volume increase during cycle i
From FIG. 4b
.[.r.sub.i = (V.sub.it ΔV.sub.i)G(t).].
.Iadd.ri =(Vit /Vi)G(t) .Iaddend.
Vit =time rate of increase of volume Vi(t) at time ti
.[.ΔVi =total volume increase of volume during.]. .Iadd.ΔVi =total increase of volume during time interval Δtiφ.Iaddend.
Estimation of Mean Blood Pressure
(1) Pmi '=K1 ric a
K1 =calibration constant
Pmi '=(P.sub. s +Pd)/2-Po
Psi =systolic blood pressure, in cycle i
Pmi =(P.sub. s +Pd)/2
Pdi =diastolic blood pressure, in cycle i
.[.(2) ekp mi=K2 Ric b.]. (2) .Iadd.ekp mi=K2 ric b .Iaddend.
K2 =constant (calibration)
b=constant ##EQU14## where Pmo =constant at calibration
φ1i +φ2i =PPi =pulse pressure during cycle i
solve equation by making LHS=RHS by varying φ1i and φ2i (φ2i =PPi -φ1i)
Psi =Pmo +φ2i +P0
Pdi =Pmo -φ1i +Po
Pmi =(P.sub. si +Pdi)/2
ri =ratio of exponentials
K3 =coefficient (variable or constant)
Correction for ri
ri (corrected)=ric =ri em(φ.sbsp.o-φ.sbsp.i)
φ0 =PPi at calibration
φi =current value of PPi.
Equation (9) above is only one form which this particular equation can take. By simple mathematical manipulations, the invention may take two other forms as per (10) and (11) below. What follows is the manipulations as well as the two other forms of the equation:
As above noted
φ.sub.2i +φ.sub.1i =PP.sub.i =P.sub.si -P.sub.di
φ.sub.2i +φ.sub.1i =(P.sub. si -P.sub.o)-(P.sub. di -P.sub.o)
P'si =Psi -Po
p'di =Pdi -P0
φ2i +φ1i =P'si -P'di
add and subtract Pmo on RHS above
φ.sub.2i +φ.sub.1i =P'.sub.si -P.sub.mo +P.sub.mo -P'.sub.di (A)
φ2i and φ1i can take on any values in satisfying the above equation (A)
Put φ2i =P'si -Pmo
and φ1i =Pmo -P'di in equation (9)
then ##EQU15## simplifying the denominator ##EQU16##
To solve equation 11:
(1) Set P'di =P'si -PPi and solve for P'si
.Iadd.P'mi =(Psi +Pdi)/2-Po .Iaddend.
(2) Set P'si =P'di -PPi and solve for P'di
Although particular embodiments have been illustrated, this was for the purpose of describing, but not limiting, the invention. Various modifications, which will come readily to the mind of one skilled in the art, are within the scope of the invention as defined in the appended claims.
.Iadd.Pmi =(Psi +Pdi)/2 .Iaddend.
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|WO2010072416A1 *||Dec 23, 2009||Jul 1, 2010||Charite-Universitätsmedizin Berlin||Method and device for monitoring and improving arteriogenesis|
|U.S. Classification||600/481, 600/507, 600/504, 600/531, 600/479|
|International Classification||A61B5/029, G06F17/00, A61B5/021|
|Cooperative Classification||A61B5/029, A61B5/021, A61B5/02007|
|European Classification||A61B5/02D, A61B5/021, A61B5/029|
|Nov 23, 1992||FPAY||Fee payment|
Year of fee payment: 4
|Nov 12, 1996||FPAY||Fee payment|
Year of fee payment: 8