Device and method for monitoring body fluid and electrolyte disorders

• US 20070129614A1
• Filed: 01/26/2007
• Published: 06/07/2007
• Est. Priority Date: 03/16/2001
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett Incorporated (Medtronic Plc)
• Inventors: Debreczeny, Martin, Schmitt, Joseph
• Granted Patent: US 8,509,866 B2
• Time in Patent Office: Days
• US Class Current: 600/310
• CPC Class Codes: A61B 5/0053 by applying pressure, e.g. compression, indentation, palpation, grasping, gauging
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: G01N 2021/3181 using LEDs
• CPC Class Codes: G01N 21/3554 for determining moisture content
• CPC Class Codes: G01N 21/359 using near infrared light

Abstract

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.

Claims

1-43. -43. (canceled)

44. A method of assessing changes in volume and osmolarity of body fluids in a body tissue, comprising:

emitting radiation at a tissue location using light emission optics configured to direct radiation of 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;

processing the electrical signal to determine;

a water balance index;

and a tissue water concentration; 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.

45. The method of claim 44 wherein the water balance index comprises a ratio of a difference between a water fraction in the blood and a water in the blood.

46. The method of claim 44 wherein the water balance index comprises a difference between a water fraction in the blood and a water fraction in the extravascular tissue.

47. The method of claim 44 wherein the tissue water concentration comprises a volume fractional water concentration.

48. The method of claim 44 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.

49. The method of claim 44 wherein determining the water balance index, Q, comprises:

$Q=\frac{f_w^{\mathrm{IV}}-f_w^{\mathrm{EV}}}{f_h^{\mathrm{IV}}}=a_1<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{{\left(\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>R/R\right)}_{{\mathrm{\lambda <br><br>}}_1}}{{\left(\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>R/R\right)}_{{\mathrm{\lambda <br><br>}}_2}}+a_0$

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, (Δ

R/R)_λ

is a fractional change in reflectance at wavelength λ

due to a blood volume change in the tissue, and a₀ and a₁ are calibration coefficients.

50. The method of claim 44 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.

51. A method of processing changes in volume and osmolarity of body fluids in a body tissue, comprising:

processing electrical signals indicative of radiation received from the body tissue to determine a water balance index and determine a tissue water concentration; 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.

52. The method of claim 51 wherein the water balance index comprises a ratio of a difference between a water fraction in the blood and a water fraction in extravascular tissue over a fractional volume concentration of hemoglobin in the blood.

53. The method of claim 51 wherein the water balance index comprises a difference between a water fraction in the blood and a water fraction in extravascular tissue.

54. The method of claim 51 wherein the tissue water concentration comprises a volume fractional water concentration.

55. The method of claim 51 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.

56. The method of claim 51 wherein determining the water balance index, Q, comprises:

$Q=\frac{f_w^{\mathrm{IV}}-f_w^{\mathrm{EV}}}{f_h^{\mathrm{IV}}}=a_1<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{{\left(\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>R/R\right)}_{{\mathrm{\lambda <br><br>}}_1}}{{\left(\mathrm{\Delta <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>R/R\right)}_{{\mathrm{\lambda <br><br>}}_2}}+a_0$

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, (Δ

R/R)_λ

is a fractional change in reflectance at wavelength λ

due to a blood volume change in the tissue, and a₀ and a₁ are calibration coefficients.

57. The method of claim 51 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.