US2003100040A1PendingUtilityA1
Blood analyte monitoring through subcutaneous measurement
Est. expiryDec 5, 2017(expired)· nominal 20-yr term from priority
A61B 5/145A61B 5/0031A61B 5/14514Y10S435/817A61B 5/4839A61B 5/14532A61B 5/746A61B 5/1486A61B 5/7203
38
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Claims
Abstract
A method for obtaining an estimate of an analyte concentration in a first fluid from an analyte concentration in a second fluid is disclosed. The method includes obtaining measurements of an analyte concentration in a second fluid by using a sensing device. The analyte concentration estimate in the first fluid is determined from these measurements. Also disclosed is a sensing device for obtaining the measurements of an analyte concentration in the first fluid and a processor configured and arranged to determine the analyte concentration in the first body fluid according to this method. This method and device can be used, for example, to determine blood glucose concentration from measurements of the glucose concentration in subcutaneous tissue. These measurements may be made using in vitro or in vivo samples. In some instances, a subcutaneously implanted sensing device, such as electrochemical sensor, is used to make the measurements.
Claims
exact text as granted — not AI-modifiedWe claim:
1 . A method for determining analyte concentration in blood, comprising:
determining a subcutaneous analyte concentration from a subcutaneous region using a sensing device; determining an analyte concentration in blood from the subcutaneous analyte concentration based on mass transfer of the analyte from blood to the subcutaneous region and on uptake of the analyte by subcutaneous cells surrounding the sensing region.
2 . The method of claim 1 , wherein the sensing device comprises an electrochemical sensor having a working electrode.
3 . The method of claim 2 , further comprising subcutaneously implanting the working electrode to generate a signal related to the subcutaneous analyte concentration.
4 . The method of claim 1 , wherein the analyte is glucose.
5 . The method of claim 4 , wherein the blood glucose concentration is determined from the subcutaneous glucose concentration using the relationship:
V
S
t
=
k
m
A
(
B
-
S
)
-
Vk
r
S
K
m
+
S
(
1
)
where V is the volume of the sensor, S is the subcutaneous glucose concentration, B is the blood glucose concentration, A is the surface area of the region surrounding the sensor, k m is a mass transfer coefficient, K m is a Michaelis-Menten constant, and k r ′ is the reaction rate constant for uptake of glucose by the subcutaneous tissue.
6 . The method of claim 5 , wherein the subcutaneous glucose concentration is determined from the blood glucose concentration according to the relationship:
S
(
t
)
=
S
(
θ
)
-
β
(
i
-
θ
)
+
∫
θ
t
B
(
τ
)
-
β
(
i
-
τ
)
τ
.
where
β
=
[
1
+
k
r
K
m
B
0
+
S
]
,
B 0 is a normalizing constant, θ is the initial time and t is the final time for a window of computation.
7 . The method of claim 6 , wherein the subcutaneous glucose concentration is determined from the blood glucose concentration using:
∫
θ
t
B
(
τ
)
-
β
(
i
-
τ
)
τ
=
∑
i
=
1
N
B
(
t
i
)
-
β
(
i
-
t
i
)
Δ
t
×
W
i
where W i is a weighting factor.
8 . The method of claim 6 , wherein the subcutaneous glucose concentration is determined from the blood glucose concentration by minimizing:
f[b]=χ
2
[b]+λΨ[b],
where
χ
2
[
b
]
=
∑
μ
=
i
i
+
N
(
∫
θ
t
μ
B
(
τ
)
-
β
i
(
t
μ
-
τ
)
τ
-
S
(
t
μ
)
+
S
(
θ
)
-
β
i
(
t
μ
-
θ
)
)
2
.
and Ψ[b] is a smoothness function.
9 . The method of claim 8 , wherein Ψ[b] is selected to provide first-order regularization.
10 . The method of claim 8 , wherein Ψ[b] is selected to provide second-order regularization.
11 . An analyte measurement system comprising:
a sensing device; and a processor coupled to the sensing device and configured and arranged to determine an analyte level in blood, from signals generated by the sensing device, based on mass transfer of the analyte from blood to a subcutaneous region and on uptake of the analyte by subcutaneous cells surrounding the subcutaneous region.
12 . The analyte measurement system of claim 11 , wherein the sensing device comprises an electrochemical sensor having a working electrode.
13 . The analyte measurement system of claim 12 , wherein the working electrode is adapted for subcutaneous implantation in an animal.
14 . The analyte measurement system of claim 11 , wherein the analyte is glucose.
15 . The analyte measurement system of claim 14 , wherein the processor is configured and arranged to determine the blood glucose concentration from a subcutaneous glucose concentration using the relationship:
V
S
t
=
k
m
A
(
B
-
S
)
-
Vk
r
S
K
m
+
S
where V is the volume of the sensor, S is the subcutaneous glucose concentration, B is the blood glucose concentration, A is the surface area of the region surrounding the sensor, k m is a mass transfer coefficient, K m is a Michaelis-Menten constant, and k r ′ is the reaction rate constant for uptake of glucose by the subcutaneous tissue.
16 . The analyte measurement system of claim 15 , wherein the processor is configured and arranged to determine the blood glucose concentration from a subcutaneous glucose concentration using the relationship:
S
(
t
)
=
S
(
θ
)
-
β
(
i
-
θ
)
∫
θ
t
B
(
τ
)
-
β
(
i
-
τ
)
τ
.
where
β
=
[
1
+
k
r
K
m
B
0
+
S
]
,
B 0 is a normalizing constant, θ is the initial time and t is the final time for a window of computation.
17 . The analyte measurement system of claim 16 , wherein the processor is configured and arranged to determine the blood glucose concentration from a subcutaneous glucose concentration using the relationship:
∫
θ
t
B
(
τ
)
-
β
(
i
-
τ
)
τ
=
∑
i
=
1
N
B
(
t
i
)
-
β
(
i
-
t
i
)
Δ
t
×
W
i
where W i is a weighting factor.
18 . The analyte measurement system of claim 16 , wherein the processor is configured and arranged to determine the blood glucose concentration from a subcutaneous glucose concentration by minimizing:
f[b]=χ
2
[b]+λΨ[b],
where
χ
2
[
b
]
=
∑
μ
=
i
i
+
N
(
∫
θ
t
μ
B
(
τ
)
-
β
i
(
t
μ
-
τ
)
τ
-
S
(
t
μ
)
+
S
(
θ
)
-
β
i
(
t
μ
-
θ
)
)
2
.
and Ψ[b] is a smoothness function.
19 . The analyte measurement system of claim 18 , wherein Ψ[b] is selected to provide first-order regularization.
20 . The analyte measurement system of claim 18 , wherein Ψ[b] is selected to provide second-order regularization.
21 . The analyte measurement system of claim 11 , further comprising a display coupled to the processor for displaying the analyte concentration in the blood.
22 . The analyte measurement system of claim 11 , further comprising an alarm coupled to the processor for alerting a user based on the analyte concentration.
23 . The analyte measurement system of claim 11 , wherein the processor is disposed in a housing adapted for placement on the skin of an animal.
24 . The analyte measurement system of claim 23 , further comprising a transmitter coupled to the electrochemical sensor and a receiver coupled to the processor, wherein the processor and receiver are disposed in a housing adapted for remote reception of signals from the electrochemical sensor via the transmitter.
25 . An apparatus for determining analyte concentration in blood based on measurements of analyte concentration determined using a sensing device, comprising:
a processor configured and arranged to determine analyte concentration in the blood from a measured subcutaneous analyte concentration based on mass transfer of the analyte from blood to a subcutaneous region and on uptake of the analyte by subcutaneous cells surrounding the subcutaneous region.
26 . The apparatus of claim 25 , wherein the analyte is glucose.
27 . A method for determining analyte-concentration in a first body fluid, comprising:
obtaining measurements of an analyte concentration in a second body fluid, different from the first body fluid, from a sensing device; and determining an analyte concentration estimate in the first fluid from the measurements by minimizing the relation: f[b]=χ 2 [b]+λΨ[b], wherein b is a vector representing analyte concentration in the first body fluid, χ 2 [b] is a function representing a fit between the estimates and the measurements, λ is a weighting function, and Ψ[b] is a function indicating smoothness of the analyte concentration estimates in the first body fluid.
28 . The method of claim 27 , wherein the analyte is glucose.
29 . The method of claim 28 , wherein the first body fluid is blood and the second body fluid is subcutaneous fluid.
30 . The method of claim 28 , wherein the model is based on the relationship:
V
S
t
=
k
m
A
(
B
-
S
)
-
Vk
r
S
K
m
+
S
where V is the volume of the sensor, S is the subcutaneous glucose concentration, B is the blood glucose concentration, A is the surface area of the region surrounding the sensor, k m is a mass transfer coefficient, K m is a Michaelis-Menten constant, and k r ′ is the reaction rate constant for uptake of glucose by the subcutaneous tissue.
31 . The method of claim 27 , wherein Ψ[b] is selected to provide first-order regularization.
32 . The method of claim 27 , wherein Ψ[b] is selected to provides second-order regularization.
33 . The method of claim 29 , wherein obtaining subcutaneous glucose measurements comprises
subcutaneously implanting a working electrode of a glucose sensor into an animal; and determining a subcutaneous glucose concentration from a signal generated at the working electrode.
34 . An analyte measurement system, comprising:
a sensing device; and a processor, coupled to the sensing device, that is configured and arranged to determine an analyte concentration estimate in a first fluid from measurements of analyte concentration in a second body fluid by minimizing the relation: f[b]=χ 2 [b]+Ψ[b], wherein b is a vector representing analyte concentration in the first body fluid, χ 2 [b] is a function representing a fit between the estimates and the measurements, λ is a weighting function, and Ψ[b] is a function indicating smoothness of the analyte concentration estimates in the first body fluid.
35 . The analyte measurement system of claim 34 , wherein the analyte is glucose.
36 . The analyte measurement system of claim 35 , wherein the first body fluid is blood and the second body fluid is subcutaneous fluid.
37 . The analyte measurement system of claim 36 , wherein the sensing device comprises a working electrode adapted for subcutaneous implantation into an animal.Join the waitlist — get patent alerts
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