Self calibrating blood chamber

Patent metadata

Field	Value
Publication number	US-9308306-B2
Application number	US-201414188193-A
Country	US
Kind code	B2
Filing date	Feb 24, 2014
Priority date	Feb 24, 2014
Publication date	Apr 12, 2016
Grant date	Apr 12, 2016

Abstract

An optical blood monitoring system and corresponding method avoid the need to obtain a precise intensity value of the light impinging upon the measured blood layer during the analysis. The system is operated to determine at least two optical measurements through blood layers of different thickness but otherwise substantially identical systems. Due to the equivalence of the systems, the two measurements can be compared so that the bulk extinction coefficient of the blood can be calculated based only on the known blood layer thicknesses and the two measurements. Reliable measurements of various blood parameters can thereby be determined without certain calibration steps.

First claim

The invention claimed is:

1. A blood chamber for use in a hemodialysis system operable to monitor at least one blood constituent, the blood chamber comprising a body defining an internal volume for receiving blood to be monitored by the hemodialysis system, the body including:
a first wall, disposed on a light inlet side of the body, configured to pass light from a light source into the internal volume;
a second wall, disposed on a light outlet side of the body, configured to pass the light from the light source out of the internal volume towards light sensors;
an inlet for supplying blood to the internal volume; and
an outlet for withdrawing blood from the internal volume;

wherein the blood chamber provides a first optical path extending through the body for the light from the light source, the first optical path orthogonally traversing a region of the first wall, passing through a section of the internal volume that has a first thickness extending from the first wall to the second wall, and orthogonally traversing a section of the second wall;
wherein the blood chamber further provides a second optical path extending through the body for the light from the light source, the second optical path orthogonally traversing another region of the first wall, passing through a section of the internal volume that has a second thickness extending from the first wall to the second wall, and orthogonally traversing another region of the second wall, wherein the second thickness is substantially greater than the first thickness and the first and second optical paths are disposed at an angle;
wherein the region of the first wall that is traversed by the first optical path is disposed at a non-zero angle γ to the region of the first wall that is traversed by the second optical path, and wherein the region of the second wall that is traversed by the first optical path is disposed at the non-zero angle γ to the region of the second wall that is traversed by the second optical path; and
wherein the first and second optical paths are disposed on either side of an axis through the light source and pass through the internal volume where blood flows through the blood chamber.

2. The blood chamber recited in claim 1 , wherein the region of the first wall that is traversed by the first optical path has an equal thickness to the region of the first wall that is traversed by the second optical path.

3. The blood chamber recited in claim 1 , wherein the region of the second wall that is traversed by the first optical path has an equal thickness to the region of the second wall that is traversed by the second optical path.

Assignees

• Fresenius Med Care Hldg Inc

Inventors

• Barrett Louis Lee
• Law Perry N

Classifications

• A61B5/14557

  specially adapted to extracorporeal circuits · CPC title

• A61M2205/3313

  used specific wavelengths · CPC title

• A61M2230/207

  hematocrit · CPC title

• G01N21/05

  Flow-through cuvettes (G01N21/09 takes precedence; handling fluid samples G01N1/10) · CPC title

• G01N21/59

  Transmissivity (G01N21/25 takes precedence) · CPC title