Blood Chamber for an Optical Blood Monitoring System

• US 20120059234A1
• Filed: 09/07/2010
• Published: 03/08/2012
• Est. Priority Date: 09/07/2010
• Status: Active Grant

• Current Assignee: Fresenius Medical Care Holdings Incorporated (Fresenius Medical Care AG)
• Original Assignee: Hema Metrics, LLC
• Inventors: Barrett, Louis L., Law, Perry N.
• Granted Patent: US 9,194,792 B2
• Time in Patent Office: Days
• US Class Current: 600/326
• CPC Class Codes: A61B 2562/185 Optical shielding, e.g. baffles
• CPC Class Codes: A61B 5/14535 for measuring haematocrit
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/14557 specially adapted to extracorporeal circuits
• CPC Class Codes: A61M 1/367 Circuit parts not covered by the preceding subgroups of group A61M1/3621
• CPC Class Codes: A61M 2205/3306 Optical measuring means
• CPC Class Codes: A61M 2205/3313 used specific wavelengths
• CPC Class Codes: G01N 2021/058 Flat flow cell
• CPC Class Codes: G01N 2021/3144 for oxymetry
• CPC Class Codes: G01N 2021/3148 using three or more wavelengths
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10
• CPC Class Codes: G01N 21/314 with comparison of measurements at specific and non-specific wavelengths dual wavelength spectrometry G01J3/427
• CPC Class Codes: G01N 21/3151 using two sources of radiation of different wavelengths G01N21/33 - G01N21/39 take precedence

Abstract

An extracorporeal blood chamber for an optical blood monitoring system includes an opaque chamber body in order to prevent inaccuracies when measuring oxygen saturation levels due to light ducting, which can occur at low oxygen saturation levels and low hematocrit levels. In one embodiment, the blood chamber need not include a moat as is present in conventional blood chambers.

Claims

1. A blood chamber for optically monitoring blood flowing through an extracorporeal tube, the blood chamber defining a flow path through an internal blood flow cavity which provides a flat viewing area for optical monitoring of the blood, the blood chamber comprising:

a chamber body having a flat internal wall and a peripheral wall extending around the flat internal wall, the flat internal wall and peripheral wall forming part of an internal blood flow cavity,

a first port and channel in fluid communication through a first opening in the peripheral wall with the internal blood flow cavity,

second port and channel in fluid communication through a second opening in the peripheral wall with the internal blood flow cavity,

and a viewing lens made of a clear material commensurate with at least a portion of the flat internal wall on the chamber body to provide viewing access of blood flowing through the internal blood flow cavity,

wherein at least a portion of the chamber body is made of a material that is opaque to red light having a wavelength defined as a third wavelength (λ

₃); and

a lens body having a flat internal wall that is attached to the chamber body to form the internal blood flow cavity along with the flat internal wall and peripheral wall of the chamber body, wherein the lens body is attached to the chamber body with the flat internal wall on the lens being substantially parallel to the flat internal wall on the chamber body and also being separated from the flat internal wall on the chamber body by a predetermined fixed distance, and further wherein the lens body comprises a viewing lens made of a clear material commensurate with at least a portion of the flat internal wall on the lens body to provide viewing access of blood flowing through the internal blood flow cavity;

wherein the opaque portion of the blood chamber attenuates light at the third wavelength (λ

₃) ducting through the chamber body and isolates the lenses from ducted light at the third wavelength (λ

₃).

2. A blood chamber as recited in claim 1 wherein the third wavelength (λ

₃) is about 660 nm.

3. A blood chamber as recited in claim 1 wherein the viewing lens of the chamber body is molded from clear polycarbonate material and the remaining portion of the chamber body is molded from a blue-tinted polycarbonate material.

4. A blood chamber as recited in claim 3 wherein the opaque polycarbonate portion of the chamber body is over molded to the clear polycarbonate viewing lens of the chamber body during the manufacturing process.

5. A blood chamber as recited in claim 1 wherein the opaque portion of the chamber body is made of a material that is opaque to a full spectrum of red light.

6. A blood chamber as recited in claim 1 wherein the entire lens body is molded from clear polycarbonate material.

7. A blood chamber as recited in claim 1 wherein the internal flow cavity includes a moat around a viewing area between the lenses.

8. A blood chamber as recited in claim 1 wherein the second port and channel are in axial alignment with the first port and channel along an axis across the blood chamber.

9. An optical blood monitoring system comprising:

extracorporeal tubing for passing blood drawn from a patient;

a blood chamber receiving blood flowing through the extracorporeal tubing, the blood chamber defining a flow path through an internal blood flow cavity and providing a viewing area for optical monitoring of the blood, the blood chamber including a flat internal wall and a peripheral wall extending around the flat internal wall, the flat internal wall and the peripheral wall forming part of the internal blood flow cavity, a first port and channel in fluid communication through a first opening in the peripheral wall with the internal blood flow cavity, a second port and channel in fluid communication through second opening in the peripheral wall with the internal blood flow cavity, and a viewing lens made of a clear material commensurate with at least a portion of the flat internal wall on the chamber body to provide viewing access of blood flowing through the internal blood flow cavity, wherein at least a portion of the chamber body is made of a material that is opaque to red light having a wavelength defined as a third wavelength (λ

₃), and

a lens body having a flat internal wall that is attached to or formed integrally with the chamber body to form the internal blood flow cavity along with the flat internal wall and peripheral wall of the chamber body, wherein the lens body is attached to the chamber body with the flat internal wall on the lens being substantially parallel to the flat internal wall on the chamber body and also being separated from the flat internal wall on the chamber body by a predetermined fixed instance, and the lens body comprises a viewing lens made of a clear material commensurate with at least a portion of the flat internal wall on the lens body to provide viewing access of blood flowing through the internal blood flow cavity;

a sensor assembly that monitors the patient'"'"'s blood flowing through the blood chamber, the sensor assembly comprising a third photoemitter for emitting red light resolution at the third wavelength (λ

₃) through the viewing lenses and blood flowing through the internal blood flow cavity of the blood chamber, a first photoemitter for emitting infrared light at a first wavelength (λ

₁) through the viewing lenses and the blood flowing through the internal blood flow cavity of the blood chamber, and at least one photodetector for detecting the intensity of the light at each of the third (λ

₃) and first (λ

₁) wavelengths after the light passes through the viewing lenses and blood flowing through the internal blood flow cavity of the blood chamber, wherein the opaque portion of the blood chamber attenuates light at the third wavelength (λ

₃) from ducting through the chamber body and isolates the lenses from ducted light at the third wavelength (λ

₃); and

a controller that comprises a ratiometric model that calculates an oxygen saturation level of the patient as a function of at least a detected value of intensity at the third wavelength (λ

₃) and a detected value of intensity at the first wavelength (λ

₁).

10. The invention as recited in claim 9 wherein the viewing lens of the chamber body is molded from clear polycarbonate material and the remaining portion of the chamber body is molded from an opaque polycarbonate material, and further wherein the opaque portion of the chamber body is overmolded over the clear viewing lens of the chamber body during the manufacturing process.

11. The invention as recited in claim 9 wherein the third wavelength (λ

₃) is about 660 nm and the first wavelength (λ

₁) is about 810 nm.

12. The invention as recited in claim 9 wherein the ratiometric model that calculates the oxygen saturation level of the patient is of the following form:

13. The invention as recited in claim 12 wherein the function g is a second order polynomial defined by the following equation:

14. The invention as recited in claim 9 wherein the sensor assembly further comprises a second photoemitter for emitting light at a second wavelength (λ

₂) through the viewing lenses and the blood flowing through the internal blood cavity of the blood chamber and at least one photodetector for detecting the intensity of light at the second wavelength (λ

₂) after the radiation passes through the viewing lenses in the blood flowing through the internal blood flow cavity of the blood chamber, and wherein the controller further comprises a ratiometric model for calculating a hematocrit value of the patient as a function of at least a detected value of intensity of the first wavelength (λ

₁) and the detected intensity of the second wavelength (λ

₂).

15. The invention as recited in claim 14 wherein the first wavelength (λ

₁) is about 829 nm and the second wavelength (λ

₂) is about 1300 nm.

16. An optical blood monitor as recited in claim 14 wherein the ratiometric model for determining hematocrit of the patient is of the following form:

17. An optical blood monitor as recited in claim 16 wherein the function f is a second order polynomial defined by the following equation: