Device and method for monitoring body fluid and electrolyte disorders
View Patent ↗Devices and methods for measuring body fluid-related metric using spectrophotometry that may be used to facilitate diagnosis and therapeutic interventions aimed at restoring body fluid balance. In one embodiment, the present invention provides a device for measuring a body-tissue water content metric as a fraction of the fat-free tissue content of a patient using optical spectrophotometry. The device includes a probe housing configured to be placed near a tissue location which is being monitored; light emission optics connected to the housing and configured to direct radiation at the tissue location; light detection optics connected to the housing and configured to receive radiation from the tissue location; and a processing device configured to process radiation from the light emission optics and the light detection optics to compute the metric where the metric includes a ratio of the water content of a portion of patient's tissue in relation to the lean or fat-free content of a portion of patient's tissue.
1. A method of assessing changes in volume and osmolarity of body fluids in a body tissue, comprising:
using a sensor:
emitting radiation at a tissue location using light emission optics configured to direct radiation of a given wavelength at the tissue location;
detecting radiation using light detection optics configured to receive radiation from the tissue location;
converting the detected radiation to an electrical signal indicative of the radiation received by the light detection optics;
using a processor:
processing the electrical signal to determine a water balance index and a tissue water concentration, wherein the water balance index comprises a difference between a water fraction in blood and a water fraction in extravascular tissue; and
analyzing in combination the water balance index and the tissue water concentration to assess the changes in volume and osmolarity of body fluids near the tissue location.
2. The method of claim 1 wherein the water balance index comprises a ratio of a difference between the water fraction in the blood and the water fraction in the extravascular tissue over a fractional volume concentration of hemoglobin in the blood.
3. The method of claim 1 wherein the tissue water concentration comprises a volume fractional water concentration.
4. The method of claim 1 wherein analyzing in combination the water balance index and the tissue water concentration to assess the changes in volume and osmolarity of body fluids near the tissue location comprises integrating over time the difference between a water fraction in the blood and a water fraction in the extravascular tissue.
5. The method of claim 1 wherein determining the water balance index, Q, comprises:
Q
=
f
w
IV
-
f
w
EV
f
h
IV
=
a
1
(
Δ
R
/
R
)
λ
1
(
Δ
R
/
R
)
λ
2
+
a
0
where f w IV and f w EV are fractional volume concentrations of water in blood and tissue, respectively, f h IV is a fractional volume concentration of hemoglobin in the blood, (ΔR/R) λ is a fractional change in reflectance at wavelength λ due to a blood volume change in the tissue, and a 0 and a 1 are calibration coefficients.
6. The method of claim 1 comprising combining the water balance index with a separate clinical measurement of fractional volume concentration of hemoglobin in the blood to provide for a measure of the difference between intravascular and extravascular water content.
7. A method of processing changes in volume and osmolarity of body fluids in a body tissue, comprising:
using a processor:
processing electrical signals indicative of radiation received from the body tissue to determine a water balance index and determine a tissue water concentration, wherein the water balance index comprises a difference between a water fraction in blood and a water fraction in extravascular tissue; and
analyzing the water balance index and the tissue water concentration to assess the changes in volume and osmolarity of body fluids in the body tissue.
8. The method of claim 7 wherein the water balance index comprises a ratio of a difference between the water fraction in the blood and the water fraction in the extravascular tissue over a fractional volume concentration of hemoglobin in the blood.
9. The method of claim 7 wherein the tissue water concentration comprises a volume fractional water concentration.
10. The method of claim 7 wherein analyzing the water balance index and the tissue water concentration to assess the changes in volume and osmolarity of body fluids in the body tissue comprises integrating over time the difference between the water fraction in the blood and the water fraction in the extravascular tissue.
11. The method of claim 7 wherein determining the water balance index, Q, comprises:
Q
=
f
w
IV
-
f
w
EV
f
h
IV
=
a
1
(
Δ
R
/
R
)
λ
1
(
Δ
R
/
R
)
λ
2
+
a
0
where f w IV and f w EV are fractional volume concentrations of water in blood and tissue, respectively, f h IV is a fractional volume concentration of hemoglobin in the blood, (ΔR/R) λ is a fractional change in reflectance at wavelength λ due to a blood volume change in the tissue, and a 0 and a 1 are calibration coefficients.
12. The method of claim 7 comprising combining the water balance index with a separate clinical measurement of fractional volume concentration of hemoglobin in the blood to provide for a measure of the difference between intravascular and extravascular water content.
13. A device for assessing changes in volume and osmolarity of body fluids in a body tissue, comprising:
means for emitting radiation at a tissue location using light emission optics configured to direct radiation of a given wavelength at the tissue location;
means for detecting radiation using light detection optics configured to receive radiation from the tissue location;
means for converting the detected radiation to an electrical signal indicative of the radiation received by the light detection optics;
means for processing the electrical signal to determine a water balance index and a tissue water concentration, wherein the water balance index comprises a difference between a water fraction in blood and a water fraction in extravascular tissue; and
means for analyzing in combination the water balance index and the tissue water concentration to assess the changes in volume and osmolarity of body fluids near the tissue location.
14. The device of claim 13 wherein the water balance index comprises a ratio of a difference between the water fraction in the blood and the water fraction in the extravascular tissue over a fractional volume concentration of hemoglobin in the blood.
15. The device of claim 13 wherein the tissue water concentration comprises a volume fractional water concentration.
16. The device of claim 13 wherein the means for analyzing in combination the water balance index and the tissue water concentration to assess the changes in volume and osmolarity of body fluids near the tissue location comprises means for integrating over time the difference between a water fraction in the blood and a water fraction in the extravascular tissue.
17. The device of claim 13 wherein determining the water balance index, Q, comprises:
Q
=
f
w
IV
-
f
w
EV
f
h
IV
=
a
1
(
Δ
R
/
R
)
λ
1
(
Δ
R
/
R
)
λ
2
+
a
0
where f w IV and f w EV are fractional volume concentrations of water in blood and tissue, respectively, f h IV is a fractional volume concentration of hemoglobin in the blood, (ΔR/R) λ is a fractional change in reflectance at wavelength λ due to a blood volume change in the tissue, and a 0 and a 1 are calibration coefficients.
18. The device of claim 13 comprising means for combining the water balance index with a separate clinical measurement of fractional volume concentration of hemoglobin in the blood to provide for a measure of the difference between intravascular and extravascular water content.
19. A device for processing changes in volume and osmolarity of body fluids in a body tissue, comprising:
means for processing electrical signals indicative of radiation received from the body tissue to determine a water balance index and determine a tissue water concentration, wherein the water balance index comprises a difference between a water fraction in blood and a water fraction in extravascular tissue; and
means for analyzing the water balance index and the tissue water concentration to assess the changes in volume and osmolarity of body fluids in the body tissue.
20. The device of claim 19 wherein the water balance index comprises a ratio of a difference between the water fraction in the blood and the water fraction in extravascular tissue over a fractional volume concentration of hemoglobin in the blood.
21. The device of claim 19 wherein the tissue water concentration comprises a volume fractional water concentration.
22. The device of claim 19 wherein the means for analyzing the water balance index and the tissue water concentration to assess the changes in volume and osmolarity of body fluids in the body tissue comprises means for integrating over time the difference between the water fraction in the blood and the water fraction in the extravascular tissue.
23. The device of claim 7 wherein determining the water balance index, Q, comprises:
Q
=
f
w
IV
-
f
w
EV
f
h
IV
=
a
1
(
Δ
R
/
R
)
λ
1
(
Δ
R
/
R
)
λ
2
+
a
0
where f w IV and f w EV are fractional volume concentrations of water in blood and tissue, respectively, f h IV is a fractional volume concentration of hemoglobin in the blood, (ΔR/R) λ is a fractional change in reflectance at wavelength λ due to a blood volume change in the tissue, and a 0 and a 1 are calibration coefficients.
24. The device of claim 19 comprising means for combining the water balance index with a separate clinical measurement of fractional volume concentration of hemoglobin in the blood to provide for a measure of the difference between intravascular and extravascular water content.