Systems and methods for varying blood flow to identify autoregulatory ranges in a patient

• US 9,474,451 B2
• Filed: 03/29/2012
• Issued: 10/25/2016
• Est. Priority Date: 04/01/2011
• Status: Active Grant

• Current Assignee: Raba Equity Partners II, LLC
• Original Assignee: Raba Equity Partners II, LLC
• Inventors: Brady, Ken M., Baruch, Robert A.
• Primary Examiner(s): Cheng, Jacqueline
• Assistant Examiner(s): Agahi, Puya
• Application Number:
  US13/433,348
• Publication Number:
  US 20120253211A1
• Time in Patent Office: 1,671 Days
• Field of Search: 600/300, 600/301, 600/481, 600/483, 600/504, 600/505, 600/507
• US Class Current: 1/1
• CPC Class Codes: A61B 5/02028 Determining haemodynamic parameters not otherwise provided for, e.g. cardiac contractility or left ventricular ejection fraction
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/026 Measuring blood flow A61B3/1233, A61B3/1241 take precedence
• CPC Class Codes: A61B 5/031 Intracranial pressure
• CPC Class Codes: A61B 5/14553 specially adapted for cerebral tissue
• CPC Class Codes: A61M 1/3666 Cardiac or cardiopulmonary bypass, e.g. heart-lung machines
• CPC Class Codes: A61M 1/3667 with assisted venous return
• CPC Class Codes: A61M 2205/33 Controlling, regulating or measuring
• CPC Class Codes: A61M 2205/3303 Using a biosensor
• CPC Class Codes: A61M 2205/3334 Measuring or controlling the flow rate
• CPC Class Codes: A61M 60/109 incorporated within extracorporeal blood circuits or systems
• CPC Class Codes: A61M 60/31 for enhancement of in vivo organ perfusion, e.g. retroperfusion
• CPC Class Codes: A61M 60/523 using blood flow data, e.g. from blood flow transducers
• CPC Class Codes: A61M 60/531 using blood pressure data, e.g. from blood pressure sensors
• CPC Class Codes: A61M 60/562 for making blood flow pulsatile in blood pumps that do not intrinsically create pulsatile flow
• CPC Class Codes: A61M 60/585 User interfaces

Abstract

A method may include controlling a bypass pump to introduce blood flow variations to a patient. The method may also include analyzing blood volume in the brain of the patient with respect to the blood flow variations and determining, based on the analyzing, whether an autoregulatory mechanism associated with the brain is operating properly.

Claims

1. A method, comprising:

setting a cardiopulmonary bypass pump to alternate output of the cardiopulmonary bypass pump between a first flow rate and a second flow rate to induce generation of a slow wave in a brain of a patient via blood flow variations provided to the patient by the alternating output of the cardiopulmonary bypass pump;

analyzing, via a monitoring device, a response waveform via blood volume in the brain of the patient with respect to the slow wave; and

determining, by the monitoring device and based on the analyzing, whether an autoregulatory mechanism associated with the brain is operating properly.

2. The method of claim 1, wherein the analyzing is performed in a frequency domain.

3. The method of claim 2, wherein the determining comprises:

determining whether peak blood volume in the brain, measured at a frequency corresponding to an input frequency of the blood flow variations, is phase shifted with respect to the peak blood volume provided by the cardiopulmonary bypass pump.

4. The method of claim 1, further comprising:

setting a third flow rate of the cardiopulmonary bypass pump based on determining that the autoregulatory mechanism is operating properly.

5. The method of claim 1, wherein the alternating output of the cardiopulmonary bypass pump introduces blood flow variations that are of fixed amplitude and duration and induce the generation of the slow wave corresponding to a sinusoidally varying slow wave.

6. The method of claim 5, wherein a frequency of input associated with the blood flow variations is set to a value ranging from 0.05 hertz (Hz) to about 0.2 Hz.

7. The method of claim 1, wherein the alternating output of the cardiopulmonary bypass pump introduces blood flow variations that induce the generation of the slow wave corresponding to a parametrically varying slow wave.

8. A system, comprising:

a pump controller configured to set flow rates of a cardiopulmonary bypass pump to vary output of the cardiopulmonary bypass pump between a first flow rate and a second flow rate to introduce blood flow variations to a patient corresponding to an input wave having a first frequency; and

at least one monitoring device configured to;

analyze blood volume in a brain of the patient with respect to the blood flow variations, and

determine, based on the analyzed blood volume, whether an autoregulatory mechanism associated with the brain is operating properly.

9. The system of claim 8, wherein the at least one monitoring device is further configured to:

determine whether peak blood volume in the brain, measured at the first frequency, is phase shifted with respect to peak blood flow or pressure provided by the cardiopulmonary bypass pump, and

determine that the autoregulatory mechanism is working properly, in response to determining that peak blood volume, measured at the first frequency, is phase shifted with respect to the peak blood flow or pressure provided by the cardiopulmonary bypass pump.

10. The system of claim 8, wherein the pump controller is further configured to:

set a third flow rate of the cardiopulmonary bypass pump based on information provided by the at least one monitoring device indicating that the autoregulatory mechanism is operating properly.

11. The system of claim 8, wherein the pump controller is configured to:

automatically set a third flow rate or pressure of the cardiopulmonary bypass pump based on information provided by the at least one monitoring device.

12. The system of claim 8, wherein the first frequency is set to a value ranging from 0.05 hertz (Hz) to about 0.2 Hz.

13. The system of claim 8, wherein the pump controller is configured to introduce blood flow variations having a fixed amplitude and duration to generate a sinusoidal input wave.

14. The system of claim 8, wherein the pump controller is configured to introduce blood flow variations corresponding to a parametric waveform.

15. A non-transitory computer-readable medium having stored thereon sequences of instructions which, when executed by at least one processor, cause the at least one processor to:

set flow rates of a cardiopulmonary bypass pump to vary output of the cardiopulmonary bypass pump between a first flow rate and a second flow rate to introduce blood flow variations to a patient;

analyze blood volume in a brain of the patient with respect to the blood flow variations; and

determine whether an autoregulatory mechanism associated with the brain is functioning properly based on the analyzing.

16. The non-transitory computer-readable medium of claim 15, wherein when determining whether an autoregulatory mechanism associated with the brain is functioning properly, the instructions cause the at least one processor to:

determine whether peak blood volume in the brain, measured at a first frequency, is negative phase shifted with respect to peak blood flow rate or pressure provided by the cardiopulmonary bypass pump, and

determine that the autoregulatory mechanism is working properly, in response to determining that the peak blood volume, measured at the first frequency, is negative phase shifted with respect to the peak blood flow rate or pressure provided by the cardiopulmonary bypass pump.

17. The non-transitory computer-readable medium of claim 15, further including instructions for causing the at least one processor to:

automatically adjust the cardiopulmonary bypass pump to provide a first third flow rate or pressure in which the autoregulatory mechanism is working properly.

18. The non-transitory computer-readable medium of claim 15, wherein when setting the flow rates of the cardiopulmonary bypass pump, the instructions cause the at least one processor to:

introduce blood flow variations to produce an input wave in the patient'"'"'s brain.

19. The non-transitory computer-readable medium of claim 18, wherein when setting the flow rates of the cardiopulmonary bypass pump, the instructions cause the at least one processor to generate the input wave having a frequency ranging from 0.05 hertz (Hz) to about 0.2 Hz.

20. The non-transitory computer-readable medium of claim 18, wherein when analyzing the blood volume in the brain, the instructions cause the at least one processor to:

analyze the blood volume at a frequency corresponding to the frequency of the input wave.