Sensor clip assembly for an optical monitoring system

• US 9,173,988 B2
• Filed: 02/18/2011
• Issued: 11/03/2015
• Est. Priority Date: 11/17/2010
• 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 L., Peterson, David W., Hudkins, N. Diane, Stowell, Matthew A., Sammann, Kristian A., Cox, Douglas L., Law, Perry N., Glaittli, Ronald S., Jensen, Bemjamin D.
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US13/030,212
• Publication Number:
  US 20120120384A1
• Time in Patent Office: 1,719 Days
• Field of Search: 600/310, 600/322, 600/323, 600/344
• US Class Current: 1/1
• 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 5/6866 Extracorporeal blood circuits, e.g. dialysis circuits
• CPC Class Codes: A61M 1/36 Other treatment of blood in a by-pass of the natural circulatory system, e.g. temperature adaptation, irradiation ; Extra-corporeal blood circuits
• CPC Class Codes: A61M 1/3609 Physical characteristics of the blood, e.g. haematocrit, urea
• 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: A61M 2230/207 hematocrit

Abstract

A sensor clip assembly for an optical blood monitoring system includes a circuit board with a microprocessor that is programmed with a ratiometric model to calculate hematocrit and/or oxygen saturation levels of a patient.

Claims

1. A sensor clip assembly for an optical monitoring system having a blood chamber with a viewing area for optically monitoring extracorporeal blood flow through the blood chamber, the sensor clip assembly comprising:

an emitter arm, comprising at least two light-emitting diode (LED) emitters;

a detector arm, comprising a silicon photodetector and an indium gallium arsenide photodetector, wherein the at least two LED emitters of the emitter arm and the photodetectors of the detector arm are disposed such that, with the sensor clip assembly attached to the blood chamber, the photodetectors are configured to detect light transmitted from the LED emitters that has passed through extracorporeal blood in the blood chamber under steady-state conditions of substantially steady pressure and substantially steady flow rate;

a processor, programmed with a ratiometric model, configured to determine a hematocrit (HCT) level corresponding to the steady-state extracorporeal blood in the blood chamber based on light intensity of the light transmitted through the extracorporeal blood and detected by the photodetectors; and

an output port, configured to provide an output data signal corresponding to the determined HCT level to an external computing device connected to the sensor clip assembly;

wherein the sensor clip assembly is pre-calibrated independent of the external computing device to which the sensor clip assembly is configured to be connected.

2. The sensor clip assembly as recited in claim 1, further comprising a power supply circuit board comprising a power supply circuit for regulating currents to be supplied to the at least two LED emitters.

3. The sensor clip assembly as recited in claim 1, wherein the processor is configured to output a digital signal corresponding to the determined HCT level at a programmable sampling rate.

4. The sensor clip assembly as recited in claim 1, wherein the output port is a Universal Serial Bus (USB) port.

5. The sensor clip assembly as recited in claim 1, wherein the sensor clip assembly further comprises a flexible conductor ribbon cable connecting at least one circuit board disposed within the emitter arm with at least one circuit board disposed within the detector arm.

6. The sensor clip assembly as recited in claim 1, further comprising:

a structural bridge between the emitter arm and the detector arm; and

a spring, biasing the emitter arm and the detector arm to close towards one another so as to facilitate attachment of the sensor clip assembly to the blood chamber.

7. The sensor clip assembly recited in claim 1, wherein a first LED emitter of the at least two LED emitters is configured to emit light at a first wavelength and a second LED emitter of the at least two LED emitters is configured to emit light at a second wavelength;

and

wherein processor is configured to apply the following formula to determine the HCT level corresponding to the extracorporeal blood in the blood chamber;

8. The sensor clip assembly as recited in claim 7, wherein the first wavelength is substantially isobestic for water and the second wavelength is substantially isobestic for hemoglobin.

9. The sensor clip assembly as recited in claim 7, wherein the function ƒ

is a second order polynomial defined by the following equation;

10. The sensor clip assembly recited in claim 7, wherein the emitter arm further comprises a third LED emitter for emitting light at a third wavelength.

11. The sensor clip assembly recited in claim 10,

wherein the processor is further configured to determine an oxygen saturation level (SAT) corresponding to the extracorporeal blood in the blood chamber based on light signals detected by the at least one photodetector;

and

wherein the processor is configured to apply the following formula;

12. The sensor clip assembly recited in claim 11, wherein the third wavelength is sensitive to signal changes due to oxygenation of hemoglobin.

13. The sensor clip assembly recited in claim 11, wherein the function g is a second order polynomial defined by the following equation:

14. The sensor clip assembly recited in claim 1, wherein the processor is disposed on a circuit board, and wherein the sensor clip assembly further comprises:

an emitter housing;

wherein the circuit board is mounted within the emitter housing without directly contacting the emitter housing so as to isolate the circuit board from vibration.

15. The sensor clip assembly recited in claim 14, wherein the circuit board is mounted within the emitter housing using a ribbon cable and a jumper.

16. The sensor clip assembly recited in claim 1, further comprising:

a detector housing;

a power supply board; and

a receiver and communications board;

wherein the power supply board and the receiver and communications board are mounted within the detector housing without directly contacting the detector housing so as to isolate the power supply board and the receiver and communications board from vibration.

17. The sensor clip assembly recited in claim 16, wherein the power supply board and the receiver and communications board are mounted within the detector housing using a strain relief for a serial cable, a ribbon cable and a jumper.

18. The sensor clip assembly recited in claim 1, wherein the photodetectors are each configured to output an analog current signal corresponding to the detected light intensity;

wherein the sensor clip assembly further comprises;

a transimpedance amplifer for converting the analog current signal to an analog voltage signal;

signal filtering hardware for filtering noise from the analog voltage signal; and

an analog-to-digital converter for converting the filtered analog voltage signal to a digital signal corresponding to the detected light intensity, wherein the processor is configured to utilize the digital signal in determining the hematocrit level.