Self calibrating blood chamber

• US 9,308,306 B2
• Filed: 02/24/2014
• Issued: 04/12/2016
• Est. Priority Date: 02/24/2014
• Status: Active Grant

• Current Assignee: Fresenius Medical Care Holdings Incorporated (Fresenius SE & Co. KGaA)
• Original Assignee: Fresenius Medical Care Holdings Incorporated (Fresenius SE & Co. KGaA)
• Inventors: Barrett, Louis Lee, Law, Perry N.
• Primary Examiner(s): Amara, Mohamed K
• Application Number:
  US14/188,193
• Publication Number:
  US 20150238672A1
• Time in Patent Office: 778 Days
• Field of Search: 356/40, 356/432, 356/436, 356/39, 356/440, 356/437, 356/73, 356/246, 356/72, 356/433, 356/435, 356/317, 356/442, 356/341, 356/632, 356/239.2, 356/356, 356/70, 356/28, 436/66, 436/164, 436/805, 422/82.05, 422/82.09, 422/82.08, 250/216, 250/372, 250/343, 250/373
• US Class Current: 1/1
• CPC Class Codes: A61B 5/14535 for measuring haematocrit
• CPC Class Codes: A61B 5/14557 specially adapted to extracorporeal circuits
• CPC Class Codes: A61M 1/14 Dialysis systems; Artificial kidneys; Blood oxygenators semi-permeable membranes characterised by the material, manufacturing processes therefor B01D71/00; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis
• CPC Class Codes: A61M 1/3609 Physical characteristics of the blood, e.g. haematocrit, urea
• CPC Class Codes: A61M 1/3621 Extra-corporeal blood circuits single-needle circuits A61M1/30
• CPC Class Codes: A61M 1/367 Circuit parts not covered by the preceding subgroups of group A61M1/3621
• CPC Class Codes: A61M 2202/0413 Blood
• CPC Class Codes: A61M 2205/3306 Optical measuring means
• CPC Class Codes: A61M 2205/3313 used specific wavelengths
• CPC Class Codes: A61M 2205/50 with microprocessors or computers
• CPC Class Codes: A61M 2205/70 with testing or calibration facilities
• CPC Class Codes: A61M 2205/702 automatically during use
• CPC Class Codes: A61M 2230/20 Blood composition characteristics
• CPC Class Codes: A61M 2230/205 partial oxygen pressure (P-O2)
• CPC Class Codes: A61M 2230/207 hematocrit
• CPC Class Codes: G01N 21/0303 Optical path conditioning in cuvettes, e.g. windows; adapted optical elements or systems; path modifying or adjustment G01N21/031 - G01N21/15 take precedence
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10
• CPC Class Codes: G01N 21/59 Transmissivity G01N21/25 takes precedence
• CPC Class Codes: G01N 2201/062 LED's
• CPC Class Codes: G01N 2201/0668 Multiple paths; optimisable path length
• CPC Class Codes: G01N 33/4925 : measuring blood gas content, e.g. O2, CO2 , HCO3
• CPC Class Codes: G01N 33/721 : Haemoglobin

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.

Claims

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.