METHOD FOR USING PHOTOPLETHYSMOGRAPHY TO OPTIMIZE FLUID REMOVAL DURING RENAL REPLACEMENT THERAPY BY HEMODIALYSIS OR HEMOFILTRATION

• US 20080067132A1
• Filed: 09/15/2006
• Published: 03/20/2008
• Est. Priority Date: 09/15/2006
• Status: Active Grant

• Current Assignee: University of Florida Research Foundation, Incorporated (State University System of Florida)
• Original Assignee: University of Florida Research Foundation, Incorporated (State University System of Florida)
• Inventors: Melker, Richard J., Ross, Edward Allan
• Granted Patent: US 7,887,502 B2
• Time in Patent Office: Days
• US Class Current: 210/739
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/0261 using optical means, e.g. infrared light
• CPC Class Codes: A61B 5/0295 using plethysmography, i.e. measuring the variations in the volume of a body part as modified by the circulation of blood therethrough, e.g. impedance plethysmography
• CPC Class Codes: A61B 5/6819 Nose
• CPC Class Codes: A61M 1/34 Filtering material out of the blood by passing it through a membrane, i.e. hemofiltration or diafiltration
• CPC Class Codes: A61M 1/3403 Regulation parameters
• CPC Class Codes: A61M 1/341 by measuring the filtrate rate or volume
• CPC Class Codes: A61M 1/3609 Physical characteristics of the blood, e.g. haematocrit, urea
• CPC Class Codes: A61M 2205/3306 Optical measuring means
• CPC Class Codes: A61M 2205/50 with microprocessors or computers

Abstract

Disclosed herein are methods, systems and devices to monitor vascular volume status during renal replacement therapy utilizing at least one oximetry/photoplethysmography sensor. The methods, systems and devices provide an alternative to conventional vascular volume monitoring methods during renal replacement therapy while enabling reliable, non-invasive, and automatic monitoring of vascular volume to avert patient hypotension. The methods, systems and devices may be employed in the context of both inpatient and outpatient dialysis facilities and may also be incorporated into conventional hemodialysis and hemofiltration techniques and equipment.

Claims

1. A method of optimizing fluid removal during renal replacement therapy, said method comprising the steps of:

securing a first oximetry/photoplethysmography sensor to a central source site of a patient wherein said first sensor is configured to generate a photoplethysmography signal stream from said central source site;

processing said photoplethysmography signal stream to determine blood flow and/or volume status;

monitoring said blood flow and/or volume status; and

adjusting the ultrafiltration rate of said renal replacement therapy responsive to a change in said blood flow and/or volume status.

2. The method of claim 1, wherein processing said photoplethysmography signal stream comprises identifying peaks and troughs of said signal stream;

identifying midpoints or minimum values between said peaks and troughs, wherein the interpolated line connecting said midpoints or minimum values represents the venous capacitance component;

extracting said venous capacitance component from said signal stream thereby obtaining the separate arterial component signal and separate said venous capacitance component signal.

3. The method of claim 1, wherein said central source site is selected from the group consisting of cheek, nasal septum, alar nares, and tongue.

4. The method of claim 1, wherein said monitoring comprises analyzing two or more datasets of signal information obtained at separate time periods.

5. The method of claim 1, wherein adjusting the ultrafiltration rate comprises decreasing the ultrafiltration rate of said renal replacement therapy responsive to a drop in said blood flow and/or volume status.

6. The method of claim 1, further comprising the step of securing a second oximetry/photoplethysmography sensor to a peripheral source site of a patient wherein said second sensor is configured to generate a photoplethysmography signal stream from said peripheral source site.

7. The method of claim 6, wherein said peripheral source site is selected from the group consisting of a finger and a toe.

8. The method of claim 1, wherein said adjusting the ultrafiltration rate is performed by a closed loop system wherein the separate arterial component signal and/or the separate venous capacitance component signal are monitored and said ultrafiltration rate is automatically adjusted responsive to said separate arterial component signal and/or said venous capacitance component signal information so as to stabilize said arterial component signal and/or said venous capacitance component signal to a target level without the need for user input.

9. A system for optimizing fluid removal during renal replacement therapy comprising:

at least one pulse oximeter/photoplethysmography probe configured for securing to a central source site of a patient and effective to generate a photoplethysmography signal stream; and

a computer communicatingly connected to said at least one pulse oximeter/photoplethysmography probe, said computer comprising at least one processing module, a first computer-readable program code module for causing said computer to process signals of said at least one pulse oximeter/photoplethysmography probe to obtain an arterial component signal or a venous capacitance component signal, or both, and a second computer-readable program code module for causing said computer to analyze said arterial component signal or venous capacitance component signal, or both to determine a change in blood flow and/or volume status.

10. The system of claim 9, wherein said computer further comprises a display screen.

11. A computer program product for use with a computer comprising at least one processing module, said product comprising:

a computer-usable medium comprising computer readable program code modules embodied in said computer-usable medium;

computer readable first program code module for causing said computer to process plethysmography signals obtained from a pulse oximeter probe by separating out an arterial component signal stream and a venous capacitance component signal stream; and

computer-readable second program code module for causing said computer to analyze said arterial component signal stream or said venous capacitance signal stream, or both, to determine a change in blood flow and/or volume status.

12. A device useful for determining a change in blood flow and/or volume status, said device comprising a computer configured to communicate with at least one pulse oximeter/photoplethysmography probe,

said computer comprising at least one processing module;

a first computer-readable program code module for causing said computer to process signals of said at least one pulse oximeter/photoplethysmography probe to obtain an arterial component signal or a venous capacitance component signal, or both, and a second computer-readable program code module for causing said computer to analyze said arterial component signal or venous capacitance component signal, or both, to determine when a change to said blood flow and/or volume status occurs.

13. The device of claim 12, further comprising a display screen effective to display information to a user of said device.

14. A method of optimizing fluid removal for a patient undergoing renal replacement therapy comprising:

determining the arterial component signal and/or the venous capacitance component signal in said patient utilizing photoplethysmography; and

adjusting the ultrafiltration rate so as to modulate said arterial component signal and/or said venous capacitance component signal to a target level.

15. The method of claim 14, wherein said adjusting the ultrafiltration rate is performed by a closed loop system wherein said arterial component signal and/or said venous capacitance component signal are monitored and said ultrafiltration rate is automatically adjusted responsive to said arterial component signal and/or said venous capacitance component signal information so as to stabilize said arterial component signal and/or said venous capacitance component signal to a target level without the need for user input.

16. A system for optimizing fluid removal for a patient undergoing renal replacement therapy comprising:

at least one pulse oximeter/photoplethysmography probe configured for securing to a central source site of said patient and effective to generate a photoplethysmography signal stream; and

a computer communicatingly connected to said at least one pulse oximeter/photoplethysmography probe, said computer comprising at least one processing module, and at least two computer-readable program code modules;

a first computer-readable program code module for causing said computer to process signals of said at least one pulse oximeter/photoplethysmography probe to obtain an arterial component signal or a venous capacitance component signal, or both; and

a second computer-readable program code module for causing said computer to adjust the ultrafiltration rate during said renal replacement therapy in response to said arterial component signal and/or said venous capacitance component signal so as obtain target arterial component signal and/or target venous capacitance component signal levels.

17. A method of optimizing fluid removal during renal replacement therapy, said method comprising the steps of:

securing a first photoplethysmography sensor to a central source site of a patient wherein said sensor is configured to generate a photoplethysmography signal stream from said central source site;

processing said signal streams received from said first sensor to obtain a separate arterial component signal and a separate venous capacitance component signal, wherein processing said signal stream information comprises processing photoplethysmography signal information;

evaluating said arterial component signal, or said venous capacitance component signal, or both, to determine when the blood flow and/or volume status changes; and

adjusting the ultrafiltration rate of said renal replacement therapy responsive to said blood flow and/or volume status change.

18. The method of claim 17, wherein said processing said signal stream comprises identifying peaks and troughs of said signal stream;

identifying midpoints or minimum values between said peaks and troughs, wherein the interpolated line connecting said midpoints or minimum values represents said separate venous capacitance component signal;

extracting said separate venous capacitance component signal from said signal stream thereby obtaining said separate arterial component signal and said separate venous capacitance component signal.

19. The method of claim 17, further comprising the step of monitoring blood flow and/or volume by analyzing two or more datasets of said signal stream information obtained at separate time periods.

20. The method of claim 17, wherein said central source site is selected from the group consisting of cheek, nasal septum, alar nares, and tongue.

21. The method of claim 17, wherein said evaluating comprises analyzing two or more datasets of signal information obtained at separate time periods.

22. The method of claim 17, wherein said adjusting the ultrafiltration rate comprises decreasing the ultrafiltration rate of said renal replacement therapy responsive to a drop in said blood flow and/or volume status.

23. The method of claim 17, further comprising the step of securing a second photoplethysmography sensor to a peripheral source site of a patient wherein said second sensor is configured to generate a photoplethysmography signal stream from said peripheral source site.

24. The method of claim 23, wherein said peripheral source site is selected from the group consisting of a finger and a toe.

25. The method of claim 17, wherein said adjusting the ultrafiltration rate is performed by a closed loop system wherein said separate arterial component signal and/or said separate venous capacitance component signal are monitored and said ultrafiltration rate is automatically adjusted responsive to said separate arterial component signal and/or separate venous capacitance component signal information so as to stabilize said separate arterial component signal and/or separate venous capacitance component signal to a target level without the need for user input.

26. A method of evaluating the strength of a patient'"'"'s compensatory mechanism, said method comprising perturbing a patient'"'"'s vascular system and monitoring the amplitude of a photoplethysmography signal stream from a central source site of said patient upon said perturbing step.

27. The method of claim 26, wherein less than a predetermined change in amplitude is indicative of a compromised compensatory mechanism.

28. The method of claim 26, wherein said perturbing comprises an intentional or incidental loss of fluid and/or blood.

29. The method of claim 26, wherein said perturbing occurs during a surgical procedure on said patient.

30. The method of claim 26, wherein said perturbing occurs by an extracorporeal therapy.

31. The method of claim 26, wherein said perturbing occurs by hemodialysis.

32. The method of claim 26, wherein said perturbing occurs by a noninvasive maneuver.