U.S. patent application number 14/466570 was filed with the patent office on 2015-03-12 for method for determining glucose concentration in human blood.
The applicant listed for this patent is Healbe Corporation. Invention is credited to Andrey A. CHECHIK, Vladimir Y. ELOKHOVSKIY, Evgeniy L. SOKOLOV.
Application Number | 20150073242 14/466570 |
Document ID | / |
Family ID | 49006041 |
Filed Date | 2015-03-12 |
United States Patent
Application |
20150073242 |
Kind Code |
A1 |
SOKOLOV; Evgeniy L. ; et
al. |
March 12, 2015 |
METHOD FOR DETERMINING GLUCOSE CONCENTRATION IN HUMAN BLOOD
Abstract
Measuring the impedance of a human body region at a high
frequency (Z.sub.HF) and a low frequency (Z.sub.LF). Z.sub.HF is
used to obtain the value of the volume of fluid in the tissues of
the region. Z.sub.LF is used to obtain the value of the volume of
extracellular fluid in the tissues. The increase in the metabolic
component in the volume of extracellular fluid is determined by the
increase of the volume of all of the fluid in comparison with the
previous measurement, determining the increase in the volume of
extracellular fluid in comparison with the previous measurement and
subsequently calculating the difference between the increases in
the volume of all of the fluid and the volume of extracellular
fluid. The glucose concentration G(t.sub.k) is determined by adding
the amount of increase in the glucose concentration and the value
of the glucose concentration determined at the previous measuring
stage.
Inventors: |
SOKOLOV; Evgeniy L.;
(Gatchina, RU) ; CHECHIK; Andrey A.; (St.
Petersburg, RU) ; ELOKHOVSKIY; Vladimir Y.; (St.
Petersburg, RU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Healbe Corporation |
Redwood City |
CA |
US |
|
|
Family ID: |
49006041 |
Appl. No.: |
14/466570 |
Filed: |
August 22, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/RU2013/000144 |
Feb 22, 2013 |
|
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14466570 |
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Current U.S.
Class: |
600/347 |
Current CPC
Class: |
A61B 5/053 20130101;
A61B 5/14532 20130101; G01N 27/02 20130101 |
Class at
Publication: |
600/347 |
International
Class: |
A61B 5/145 20060101
A61B005/145; G01N 27/02 20060101 G01N027/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 24, 2012 |
RU |
2012106461 |
Claims
1. A method of measuring of a concentration of blood glucose in a
human, the method comprising: using spaced apart electrodes
attached to a region of a body of the human to successively measure
values of high frequency impedance and low frequency impedance of
the region at predetermined time intervals; using a measured value
of the high frequency impedance to determine an estimate of a
volume of fluid in tissue of the region between the electrodes;
using a measured value of the low frequency impedance to determine
an estimate of a volume of an extracellular fluid in the tissue in
the region between the electrodes; determining an increment of a
metabolic component of the volume of the extracellular fluid by:
determining an increment of the estimate of the volume of the fluid
relative to a previously measured value of the volume of the fluid;
determining an increment of the estimate of the volume of the
extracellular fluid relative to a previously measured value of the
volume of the extracellular fluid; determining a difference between
the increment of the estimate of the volume of the fluid and the
increment of the estimate of the volume of the extracellular fluid;
determining an increment of the concentration of the blood glucose
by normalizing the increment of the metabolic component of the
volume of the extracellular fluid; and determining the
concentration of the blood glucose by adding up the increment of
the concentration of the blood glucose and a previously determined
concentration of the blood; wherein determining a concentration of
the blood glucose at a first time interval comprises adding up an
increment of the concentration at the first interval of time and an
initial blood glucose concentration.
2. The method according to claim 1, wherein the initial blood
glucose concentration is determined invasively.
3. The method according to claim 1, wherein at least two spaced
apart electrodes attached to the region of the body of the human
are used.
4. The method according to claim 3, wherein the at least two spaced
apart electrodes are attached to the peripheral body regions as an
arm or a finger.
5. The method according to claim 1, wherein the predetermined time
intervals range from 1 s to 10 min.
6. The method according to claim 1, wherein: W.sub.sum (t.sub.k) is
the volume of fluid in tissue of the region between the electrodes,
determined according to the following equation:
W.sub.sum(t.sub.k)=AL.sup.2/Z.sub.HF(t.sub.k), wherein: L--is a
distance between the two electrodes; Z.sub.HF(t.sub.k) is the high
frequency HF impedance measured at time t.sub.k; A--is a
calibration factor determined as A=V.sub.sumZ.sub.HF/L.sup.2;
wherein V.sub.sum--is a preliminary determined value of the volume
of fluid in the tissue in the region between the electrodes;
Z.sub.HF--preliminary determined high frequency HF impedance;
W.sub.out(t.sub.k) is the volume of the extracellular fluid in the
tissue of the region, between the electrodes determined according
to the following equation:
W.sub.out(t.sub.k)=BL.sup.2/Z.sub.LF(t.sub.k), wherein
Z.sub.LF(t.sub.k)--is the low frequency LF impedance measured at
time t.sub.k; B--is a calibration factor, calculated as
B=V.sub.outZ.sub.LF/L.sup.2; wherein V.sub.out--preliminary
determined volume of the extracellular fluid in region;
Z.sub.LF--preliminary determined low-frequency LF impedance;
.DELTA.W.sub.osm(t.sub.k) is the increment of the metabolic
component determined as:
.DELTA.W.sub.osm(t.sub.k)=[W.sub.sum(t.sub.k-1)-W.sub.sum(t.sub.k)]-K.sub-
.a[W.sub.out(t.sub.k-1)-W.sub.out(t.sub.k)], wherein
W.sub.sum(t.sub.k-1) is the volume of the fluid in the tissue
measured at time t.sub.k-1; W.sub.out(t.sub.k-1) is the volume of
the extracellular fluid measured at time t.sub.k-1; K.sub.a is a
factor dependent on a human hematocrit volume selected from a range
from 1.2 to 2.1; .DELTA.G(t.sub.k)is the increment of the
concentration of the blood glucose determined as:
.DELTA.G(t.sub.k)=.DELTA.W.sub.osm(t.sub.k)K.sub.EK.sub.PR/K.sub.g,
wherein K.sub.g is a normalizing factor ranging from 0.005
l.sup.2millimole.sup.-1 to 0.006 l.sup.2millimole.sup.-1; K.sub.E
is a factor selected from a range of 0.23 to 0.4 before a meal
intake, and selected from a range of 0.6 to 1.0 after the meal;
K.sub.PR is a factor corresponding to measuring the concentration
of the glucose in blood from 20 min to 45 min after the meal intake
and wherein: K.sub.PR=1 if .DELTA.W.sub.osm(t.sub.k)is more than 0;
and K.sub.PR=-1 if .DELTA.W.sub.osm(t.sub.k) is less than 0.
Description
RELATED APPLICATIONS
[0001] This Application is a Continuation application of
International Application PCT/RU2013/000144, filed on Feb. 22,
2013, which in turn claims priority to Russian Patent Applications
No. RU2012106461, filed Feb. 24, 2012, both of which are
incorporated herein by reference in their entirety.
FIELD OF THE INVENTION
[0002] The invention refers to non-surgical methods for medical
examination of human health, namely, to methods for determining
glucose concentration in human blood as a result of measuring the
impedance of human body part.
BACKGROUND OF THE INVENTION
[0003] Non-invasive methods for determining glucose concentration
in human blood based on measuring the electrical impedance of a
human body part or impedance components are known.
[0004] For example, a method for the indication of sugar content in
human blood is known [RU Pat. No. 2073242, G01N33/4, 1997], with
which sugar content level is determined based on variation of
dielectric permeability of a finger placed in the electrical field
of transducer.
[0005] A method for monitoring the amount of sugar in human blood
is also known [RU Pat. No. 2088927, G01N33/49, 1997], with which
the measurement is taken by changing the reactance of oscillating
circuits included in the secondary circuits of high-frequency
generator via direct action of human upon oscillating circuits
elements. With this method, the amount of sugar in blood is
determined based on variation of current in the secondary circuits
of high-frequency generator.
[0006] Another method is known [U.S. Pat. No. 5,792,668, G01N27/00,
1998], with which spectral analysis of high-frequency radiation
reflected by human body or passing through the human body is
conducted. The phase shift between direct and reflected (or
transmitted) waves, which characterizes the reactive component of
electrical impedance, represents a parameter to be measured by this
method. The concentration of substances contained in the blood (in
particular, glucose concentration) is determined based on measured
parameters of phase spectrum.
[0007] Another method is known, which was embodied in a device
described in the RU Pat. No. 9703U1, A61B5/00, 1999. Glucose
concentration is determined by this device based on measurement of
human body region impedance at two frequencies, determining
capacitive component of impedance and converting the obtained value
of capacitive component into glucose concentration in patient's
blood.
[0008] A method for measuring glucose concentration in human blood
non-invasively is known [U.S. Pat. No. 6,517,482, A61B5/00, 2003].
The method is based on measuring impedance between two electrodes
at a number of frequencies and deriving the value of glucose
concentration on the basis of measured values.
[0009] Another method for determining glucose concentration in
blood non-invasively is known, which involves measuring electric
transfer functions by means of two pairs of four-electrode sensors
[RU Pat. No. 2342071, A61B5/053, 2008]. The concentration of
glucose in blood is determined based mathematical model specified
in advance.
[0010] Another method for determining glucose concentration in
human blood is also known [U.S. Pat. No. 7,050,847, A61B5/00,
2006], with which impedance of a human body area is measured at
different frequencies by means of sensors. Impedance value at high
frequencies is related to fluid volume in body tissues, while
impedance value at low frequencies--to volume of extracellular
fluid. Parameters of biological fluids in the human body are
determined based on the measured values, and then glucose
concentration in human blood is derived from these parameters.
[0011] However, the above-described methods are characterized by
one common disadvantage--namely, the values of glucose
concentration in human blood obtained through the use of these
methods rank below the values obtained using direct invasive
methods in terms of measurement accuracy. At the same time,
invasive methods, which require taking samples of blood, rank below
non-invasive ones in terms of convenience and safety.
[0012] An engineering problem to be solved by the present invention
consists in working out a non-invasive method for continuous
determination of glucose concentration in human blood that is
characterized by higher accuracy as compared to currently known
non-invasive methods.
SUMMARY OF THE INVENTION
[0013] A method of measuring of a concentration of blood glucose in
a human, the method comprising:
[0014] using spaced apart electrodes attached to a region of a body
of the human to successively measure values of high frequency
impedance and low frequency impedance of the region at
predetermined time intervals;
[0015] using a measured value of the high frequency impedance to
determine an estimate of a volume of fluid in tissue of the region
between the electrodes;
[0016] using a measured value of the low frequency impedance to
determine an estimate of a volume of an extracellular fluid in the
tissue in the region between the electrodes;
[0017] determining an increment of a metabolic component of the
volume of the extracellular fluid by:
[0018] determining an increment of the estimate of the volume of
the fluid relative to a previously measured value of the volume of
the fluid;
[0019] determining an increment of the estimate of the volume of
the extracellular fluid relative to a previously measured value of
the volume of the extracellular fluid;
[0020] determining a difference between the increment of the
estimate of the volume of the fluid and the increment of the
estimate of the volume of the extracellular fluid;
[0021] determining an increment of the concentration of the blood
glucose by normalizing the increment of the metabolic component of
the volume of the extracellular fluid; and
[0022] determining the concentration of the blood glucose by adding
up the increment of the concentration of the blood glucose and a
previously determined concentration of the blood;
[0023] wherein determining a concentration of the blood glucose at
a first time interval comprises adding up an increment of the
concentration at the first interval of time and an initial blood
glucose concentration.
[0024] The principal physics of the method consists in measuring
the volume of fluid in a human body region. The water in human body
accounts for 70% of body weight, and it is not present in the human
body as a single space, but distributed among body tissues.
Vascular walls and cell membranes (out of which consist all tissues
of human body) serve as boundaries for fluids. It is generally
accepted to distinguish three water spaces: intracellular fluid,
intravascular fluid (blood plasma fluid) and intercellular fluid
(fluid that fills the intercellular space).
[0025] The intracellular fluid or fluid contained within tissue
cells and red blood cells accounts for approximately 30-40% of
human body weight.
[0026] Intravascular fluid and intercellular fluid form the space
of extracellular fluid, which accounts for about 20% of human body
weight.
[0027] Substances intended for sustaining the life of cells or
products of their vital activity that are to be disposed of or
reprocessed inside human body are present in each type of fluid.
These substances move through cell membranes from one space to
another in the process of vital activity of the human body. Osmotic
pressure that depends upon difference in concentration
(concentration gradient) of substances on different sides of the
membrane represents one of the driving forces for this motion.
[0028] A dynamic equilibrium of metabolic processes is observed in
the state of rest. The appearance of concentration gradient of
osmotic pressure (e.g., together with glucose inflow from
gastrointestinal tract after food intake) forces water to move
though cell membrane in the direction of space characterized by
higher concentration of solids dissolved in it. The volumes of
water sectors are changed as a result of this process. But then
regulatory mechanisms striving to restore the disturbed equilibrium
of these spaces come into action. In other words, changes of water
spaces volumes of human body have characteristic (cyclic) specific
features. These specific features can be used as indicators of the
character of metabolic processes in the human body, e.g. increase
of glucose concentration in human blood after food intake.
[0029] The basis of the method consists in estimating an increase
or decrease of glucose concentration in the blood based on changes
of water spaces in the human body in time, which is determined in
the course of periodic measurements of impedance of a human body
region.
[0030] The following steps are performed in particular embodiments
of the method.
[0031] Initial value of glucose concentration in human blood is
determined in the beginning of measurements (using an alternative
method--either invasive or non-invasive one). This absolute value
is individual for every human being and it determines not only the
nature of dynamics of glucose concentration changes, but also its
absolute values during different periods of life activity of human
being.
[0032] In particular, at least two electrodes installed at a
certain distance from one another (preferably on peripheral body
regions--e.g. a finger or an arm) can be used for measuring the
impedance of a human body region.
[0033] Measurements of impedance of a human body region at high and
low frequencies are taken with a predetermined time interval from 1
sec to 10 min. For the sake of convenience of hardware
implementation of the method these time interval should be
equal.
[0034] The moment of food intake is recorded during measurement
taking, and this fact is used to adjust the indicators of dynamics
of glucose supply into the human body.
[0035] Specifically, the following parameters are determined when
implementing the method based on values of human body region
impedance measured at high and low frequencies at points in time
t.sub.k:
[0036] 1) Volume of fluid contained in the tissues of the human
body region between electrodes W.sub.sum(t.sub.k) is calculated
from the equation:
W.sub.sum(t.sub.k)=AL.sup.2/Z.sub.HF(t.sub.k),
[0037] where: L--the distance between two electrodes;
[0038] Z.sub.HF(t.sub.k) is the high frequency HF impedance
measured at time t.sub.k;
[0039] A is a calibration factor determined as:
A=V.sub.sumZ.sub.HF/L.sup.2,
[0040] where: V.sub.sum is a preliminary determined value of the
volume of fluid in the tissue in the region between the
electrodes;
[0041] Z.sub.HF--preliminary determined high frequency HF
impedance;
[0042] 2) W.sub.out(t.sub.k) is the volume of the extracellular
fluid in the tissue of the region between the electrodes determined
according to the following equation:
W.sub.out(t.sub.k)=BL.sup.2/Z.sub.LF(t.sub.k),
[0043] where: Z.sub.LF(t.sub.k) is the low frequency LF impedance
measured at time t.sub.k;
[0044] B is a calibration factor, calculated as:
B=V.sub.outZ.sub.LF/L.sup.2;
[0045] where: V.sub.out--preliminary determined volume of the
extracellular fluid in region between the electrodes;
[0046] Z.sub.LF--preliminary determined low-frequency LF
impedance;
[0047] 3) .DELTA.W.sub.osm(t.sub.k) is the increment of the
metabolic component determined as:
.DELTA.W.sub.osm(t.sub.k)=[W.sub.sum(t.sub.k-1)-W.sub.sum(t.sub.k)]-K.su-
b.a[W.sub.out(t.sub.k-1)-W.sub.out(t.sub.k)],
[0048] where: W.sub.sum(t.sub.k-1)--volume of fluid in the tissues
of the human body region between the electrodes measured at time
t.sub.k-1;
[0049] W.sub.out (t.sub.k-1)--volume of extracellular fluid in the
tissues of the human body region between the electrodes measured at
time t.sub.k-1;
[0050] K.sub.a is a factor dependent on a human hematocrit volume
selected from a range from 1.2 to 2.1;
[0051] 4) .DELTA.G(t.sub.k) is the increment of the concentration
of the blood glucose determined as:
.DELTA.G(t.sub.k)=.DELTA.W.sub.osm(t.sub.k)K.sub.EK.sub.PR/K.sub.g,
[0052] where: K.sub.g is a normalizing factor ranging from 0.005
l.sup.2millimole.sup.-1 to 0.006 l.sup.2millimole.sup.-1;
[0053] K.sub.E is a factor selected from a range of 0.23 to 0.4
before a meal intake, and selected from a range of 0.6 to 1.0 after
the meal;
[0054] K.sub.PR is a factor corresponding to measuring the
concentration of the glucose in blood from 20 min to 45 min after
the meal intake and wherein:
[0055] K.sub.PR=1, if .DELTA.W.sub.osm(t.sub.k)is more than 0;
[0056] K.sub.PR=-1, if .DELTA.W.sub.osm(t.sub.k) is less than
0.
BRIEF DESCRIPTION OF THE DRAWINGS
[0057] The invention is illustrated with the following graphic
drawings.
[0058] FIG. 1A is a graph showing variation of shows the results of
determining glucose concentration in the blood for the first
volunteer.
[0059] FIG. 1B is a graph showing measured values of impedance and
temperature for the first volunteer.
[0060] FIG. 2A is a graph showing variation of shows the results of
determining glucose concentration in the blood for the second
volunteer.
[0061] FIG. 2B is a graph showing measured values of impedance and
temperature for the second volunteer.
[0062] FIG. 3A is a graph showing variation of shows the results of
determining glucose concentration in the blood for the third
volunteer.
[0063] FIG. 3B is a graph showing measured values of impedance and
temperature for the third volunteer.
[0064] FIGS. 1a, 2a and 3a show the graphs of variation of glucose
concentration determined through the use of different methods,
including the method of the present invention, while FIGS. 1b, 2b
and 3b show graphs of measured values of impedance and
temperature.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0065] The method is implemented in the following way.
[0066] Two electrodes are secured on a human body region apart from
one another--at distance L . It is preferable to secure electrodes
on peripheral body regions--e.g. on an arm, specifically, on
forearm or finger. The best result will be obtained in the case of
using annular electrodes embracing forearm or a finger
[0067] Since the method according to the invention claimed herein
is based on calculating the values of the increment of glucose
concentration in human blood followed by summing up the calculated
values, prior to taking measurements of impedance, blood glucose
concentration should be measured (using any other method--invasive
or non-invasive one), and the value of thus measured impedance is
taken as the initial one.
[0068] Impedance of a human body region is measured between
electrodes at two frequencies: high frequency HF and low frequency
LF. High frequency HF is chosen from the range from 200 kHz to 2
MHz; low frequency LF is chosen from the range from 20 kHz to 80
kHz. Electrical impedance of components of electrical impedance of
body region tissues can be measured using one of the known methods,
specifically, by radiating high-frequency oscillations and
subsequent measuring the impedance by means of capacitive sensors.
Impedance of a human body region is measured at time intervals
chosen from the range from 1 sec to 10 min.
[0069] A moment of food intake (characterizing glucose supply into
the human body from the outside) is recorded in the course of
measurements. This is done to derive the increment of metabolic
component of the volume of extracellular fluid related to glucose,
taking into account the time that have elapsed since the recorded
moment of food intake beginning.
[0070] Based on the initial glucose concentration volume in human
blood, current successive measurements of impedance of a human body
region at high and low frequencies, and taking into account the
time moment of food intake, glucose concentration in human blood is
derived as follows.
[0071] 1. The volume of fluid contained in a human body region
between the electrodes W.sub.sum(t.sup.k) is derived based on
impedance value for human body region measured at high frequency HF
at point in time t.sub.k-Z.sub.HF(t.sub.k) , taking into account
distance L between the electrodes, as follows:
W.sub.sum(t.sub.k)=AL.sup.2/Z.sub.HF(t.sub.k),
[0072] where: A--calibration factor, calculated from the
formula:
A=V.sub.sumZ.sub.HF/L.sup.2.
[0073] Here, V.sub.sum--value (obtained in advance) of the volume
of fluid contained in the tissues of human body region between the
electrodes. This value can be, for instance, calculated using
anatomical relationships of the human body region chosen for
impedance measuring. Also, the value of impedance of a human body
region measured at high frequency Z.sub.HF (and obtained in advance
prior to the beginning of measurements intended for determining
glucose concentration in human blood according to the invention
claimed herein) is used for deriving calibration factor A.
[0074] 2. The volume of extracellular fluid contained in the
tissues of a human body region between the electrodes
W.sub.out(t.sub.k) is derived based on impedance value for human
body region measured at low frequency LF at point in time
t.sub.k--Z.sub.LF(t.sub.k), taking into account distance L between
the electrodes, as follows:
W.sub.out(t.sub.k)=BL.sup.2/Z.sub.LF(t.sub.k),
[0075] where: B--calibration factor, calculated from the
formula:
B=V.sub.outZ.sub.LF/L.sup.2.
[0076] Here, V.sub.out--value (obtained in advance) of the volume
of extracellular fluid contained in the human body region between
the electrodes. This value can be, for instance, calculated using
anatomical relationships of the human body region chosen for
impedance measuring. Also, the value of impedance of a human body
region measured at low frequency Z.sub.LF is used for determining
the calibration factor B. This impedance value is determined in
advance prior to measurements of glucose concentration in human
blood according to the present invention.
[0077] 3. Then obtained value of volume of fluid contained in the
tissues of the human body region between electrodes, and volume of
extracellular fluid contained in the tissues of the human body
region between electrodes, are used for calculating the increment
of metabolic component of the extracellular fluid volume
.DELTA.W.sub.osm(t.sub.k). The values of fluid volumes obtained for
measurements of impedance at point in time t.sub.k and for the
previous measurement at point in time t.sub.k-1 are used for this
calculation. The increment of metabolic component of extracellular
fluid volume is calculated from the formula:
.DELTA.W.sub.osm(t.sub.k)=[W.sub.sum(t.sub.k-1)-W.sub.sum(t.sub.k)]-K.su-
b.a[W.sub.out(t.sub.k-1)-W.sub.out(t.sub.k)],
[0078] where: W.sub.sum(t.sub.k)--volume of fluid contained in the
tissues of the human body region between the electrodes, for the
current measurement taken at point in time t.sub.k;
[0079] W.sub.sum(t.sub.k-1)--volume of fluid contained in the
tissues of the human body region between the electrodes, for the
previous measurement taken at point in time t.sub.k-1;
[0080] W.sub.out(t.sub.k)--volume of extracellular fluid contained
in the tissues of the human body region between the electrodes, for
the current measurement taken at point in time t.sub.k;
[0081] W.sub.out(t.sub.k-1)--volume of extracellular fluid
contained in the tissues of the human body region between the
electrodes, for the previous measurement taken at point in time
t.sub.k-1;
[0082] K.sub.a--factor dependent on the value of human hematocrit
(this factor is chosen from the range from 1.2 to 2.1).
[0083] 4. The value of the increment of glucose concentration in
human blood is determined based on the obtained value of
.DELTA.W.sub.osm(t.sub.k) taking into account the moment of food
intake:
.DELTA.G(t.sub.k)=.DELTA.W.sub.osm(t.sub.k)K.sub.EK.sub.PR/K.sub.g,
[0084] where: K.sub.g--the normalizing factor chosen from the range
from 0.005 l.sup.2millimole.sup.-1 to 0.006
l.sup.2millimole.sup.-1.
[0085] K.sub.E--factor dependent on food intake; when determining
glucose concentration in human blood prior to food intake, K.sub.E
value is chosen from the range from 0.23 to 0.4, and when
determining glucose concentration in human blood after food intake,
K.sub.E value is chosen from the range from 0.6 to 1.0;
[0086] K.sub.PR--factor used for determining glucose concentration
in human blood in the time period from 20 to 45 minutes after food
intake, with this factor taking the value either 1 or -1 depending
on the sign of the said increment of metabolic component of the
extracellular fluid volume according to the following rule:
[0087] K.sub.PR=1, if the said increment of metabolic component of
the extracellular fluid volume .DELTA.W.sub.osm(t.sub.k) is greater
than 0,
[0088] K.sub.PR=-1, if the said increment of metabolic component of
the extracellular fluid volume .DELTA.W.sub.osm(t.sub.k) is less
than 0.
[0089] 5. The final value of glucose concentration in human blood
by point in time t.sub.k is derived as follows:
G ( t k ) = G 0 + i = 1 k .DELTA. G ( t i ) , ##EQU00001##
[0090] where: G.sub.0--initial value of glucose concentration in
human blood;
[0091] .DELTA.G(t.sub.i)--values of all increments of glucose
concentration in human blood obtained from the beginning of
measurements till point in time t.sub.k , where i={1,k}.
[0092] Thus, knowing the initial value of glucose concentration in
human blood G.sub.0 and periodically taking measurements of
impedance of the human body region at high and low
frequencies--Z.sub.HF(t.sub.k) and Z.sub.LF(t.sub.k), one can
derive the current value of glucose concentration in human blood.
The present invention can be embodied as quite simple measuring
device capable of calculating of the above-indicated parameters
characterizing changes in volumes of water spaces in human tissues,
and finally, the current value of glucose concentration in human
blood, including the option of taking into account the individual
physiological features of human being and moments of food
intake.
EXAMPLES
Example 1
Processing of Measurement Data for Healthy Volunteer #1
[0093] A 38-year-old healthy male, took a meal (food load) of 300 g
of sweet beverage (Pepsi Cola). FIG. 1b shows the graphs of
impedance value variation Z.sub.HF and Z.sub.LF and temperature
T.degree. C. recorded by the sensor located on the forearm, while
FIG. 1a shows the graph of variation of glucose concentration in
the blood of Volunteer #1. Dots indicate values of blood sample
taken during the measurements (Roche Accu-Chek Active glucometer
was used). The mean error for the measurement interval of 150
minutes was equal to 6.8%.
Example 2
Processing of Measurement Data for Healthy Volunteer #2
[0094] A 45-year-old healthy male, took a meal (food load) of two
200 g glasses of sweet beverage (Pepsi Cola). FIG. 2b shows the
graphs of impedance value variation Z.sub.HF and Z.sub.LF and
temperature T.degree. C. recorded by the sensor located on the
forearm, while FIG. 2a shows the graph of variation of glucose
concentration in the blood of Volunteer #2. Dots indicate values of
blood sample taken during the measurements (Roche Accu-Chek Active
glucometer was used). The mean error for the measurement interval
of 140 minutes was equal to 7.2%.
Example 3
Processing of Measurement Data for Healthy Volunteer #3
[0095] A 42-year-old healthy male, took a combined meal (food load)
of 200 g of sweet beverage (Pepsi Cola) and banana. FIG. 3b shows
the graphs of impedance value variation Z.sub.HF and Z.sub.LF and
temperature T.degree. C. recorded by the sensor located on the
forearm, while FIG. 3a shows the graph of variation of glucose
concentration in the blood of Volunteer #3. Dots indicate values of
blood sample taken during the measurements (Roche Accu-Chek Active
glucometer was used). The mean error for the measurement interval
of 150 minutes was equal to 9.5%.
[0096] The conducted tests showed that the method claimed herein is
characterized by lesser error when determining the value of glucose
concentration in human blood as compared to the known non-invasive
methods.
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