Sensor in vivo measurement of osmotic changes

• US 20060173252A1
• Filed: 06/09/2004
• Published: 08/03/2006
• Est. Priority Date: 06/10/2003
• Status: Active Grant

• Current Assignee: Lifecare Holdings Incorporated (Hospital Acquisition LLC)
• Original Assignee: Lifecare Holdings Incorporated (Hospital Acquisition LLC)
• Inventors: Kulseng, Bard Erik, Ellingsen, Olav, Kristiansen, Helge
• Granted Patent: US 7,276,028 B2
• Time in Patent Office: Days
• US Class Current: 600/309
• CPC Class Codes: A61B 2560/0219 of externally powered implanted units
• CPC Class Codes: A61B 2562/028 Microscale sensors, e.g. electromechanical sensors [MEMS]
• CPC Class Codes: A61B 5/0031 Implanted circuitry
• CPC Class Codes: A61B 5/076 Permanent implantations telemetry using implanted circuitry A61B5/0031; implanted stimulators for therapy A61N1/3605, A61N1/362, A61N1/372
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes

Abstract

The present invention teaches a method, system and units for measuring changes in blood during a longer period of time in vivo with a patient by measuring diffusivity of solvent. A differential pressure sensor is arranged on a silicon wafer or beam comprising resistors being in communication with fluids in two chambers via semipermable membranes enabling measuring of two components in said blood by tracking changes over time.

Claims

1. Sensor for measuring a condition of body fluids comprising a sensor element implanted in said body being in radio communication with a receiver unit outside said body, wherein said sensor element implanted in said body comprises at least one differential pressure sensor arranged with at least two chambers on each side of said pressure sensor, where each chamber is confined, in one end by one side of said pressure sensor each, and on the other end by a semipermiable membrane each towards the surroundings.

2. Sensor according to claim 1, wherein said pressure sensor is arranged with piezo-electric resistor elements buried in a silicon wafer or beam.

3. Sensor according to claim 1, wherein said piezo-electric resistor elements are connected as a Wheatstone bridge.

4. Sensor according to claim 1, wherein a depth for a chamber defined as the distance between said pressure sensor and said semipermiable membrane is arranged such that a gradient of a concentration of a solvent in said chamber is small.

5. Sensor according to one of the preceding claims, wherein said membranes in said sensor element are arranged sufficient stiff to inhibit displacement of said membrane when there are changes in osmotic pressure.

6. Sensor according to one of the preceding claims, wherein said membranes are provided by anisotropic etching of a silicon wafer or a glass wafer.