Method for evaluating skin hydration and fluid compartmentalization

• US 7,713,196 B2
• Filed: 03/09/2007
• Issued: 05/11/2010
• Est. Priority Date: 03/09/2007
• Status: Expired due to Fees

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Baker, Clark R. Jr.
• Primary Examiner(s): Sirmons; Kevin C
• Assistant Examiner(s): Anderson; Michael J
• Application Number:
  US11/716,481
• Publication Number:
  US 20080221407A1
• Time in Patent Office: 1,159 Days
• Field of Search: 604/506, 604/19, 604/48, 604/500, 604/22, 604/4.01, 604/272, 604/505, 600/311, 600/346, 600/390
• US Class Current: 600/309
• CPC Class Codes: A61B 10/0045 Devices for taking samples of body liquids devices for taking blood samples A61B5/15
• CPC Class Codes: A61B 17/205 Vaccinating by means of needles or other puncturing devices
• CPC Class Codes: A61B 2010/008 Interstitial fluid
• CPC Class Codes: A61B 5/14514 using means for aiding extraction of interstitial fluid, e.g. microneedles or suction
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/441 Skin evaluation, e.g. for skin disorder diagnosis
• CPC Class Codes: A61B 5/445 Evaluating skin irritation or skin trauma, e.g. rash, eczema, wound, bed sore

Abstract

There is provided a system and method for evaluating skin hydration and fluid compartmentalization. The system includes a microneedle array configured to extract fluid from an interstitial space and a pressure sensor configured to measure a pressure differential between the interstitial space and ambient pressure during extraction of the fluid. A processor coupled to the pressure sensor is configured to compute a hydration index based on the pressure differential. A display coupled to the processor is configured to display the hydration index.

Claims

1. A method for determining hydration comprising:

extracting fluid through microneedles inserted into skin;

determining the pressure gradient required to extract the fluid; and

determining a hydration index based on the pressure gradient.

2. The method of claim 1, wherein the hydration index is representative of the hydration of the skin.

3. The method of claim 1, wherein the hydration index is representative of the hydration of the body.

4. The method of claim 1 comprising combining a skin thickness value with the pressure gradient to determine the volume of a compartment of the skin.

5. The method of claim 1 comprising measuring blood specific analytes in the fluid to determine leakage from a vascular compartment.

6. The method of claim 5 wherein the blood specific analytes comprise albumin or other plasma proteins.

7. The method of claim 1 comprising measuring inflammation-specific analyte concentration.

8. The method of claim 1 comprising measuring intracellular-specific analyte concentrations to assess the contribution of intercellular fluid.

9. The method of claim 8 wherein the measuring intracellular-specific analyte concentration comprises measuring potassium concentration.

10. The method of claim 8 comprising quantifying the extent of cellular trauma in response to insertion of microneedles based on the contribution of intercellular fluid.

11. The method of claim 1, wherein determining the hydration index based on the pressure gradient comprises determining whether the fluid has a positive pressure differential relative to ambient pressure.

12. The method of claim 1, wherein determining the pressure gradient required to extract the fluid comprises measuring the amount of pressure required to extract the interstitial fluid.

13. The method of claim 12, wherein determining the hydration index comprises correlating the measured pressure required to extract the interstitial fluid with a volume of free fluid in an interstitial space.

14. The method of claim 1, wherein determining the pressure gradient required to extract the fluid comprises using a calibration factor to compensate for resistance of fluid flow caused by the microneedles.