Method and apparatus for non-invasive continuous monitoring of cerebrovascular autoregulation state

• US 20060094964A1
• Filed: 10/27/2005
• Published: 05/04/2006
• Est. Priority Date: 10/28/2004
• Status: Active Grant

• Current Assignee: Scienceforbrain UAB
• Original Assignee: Uab Vittamed
• Inventors: Ragauskas, Arminas, Daubaris, Gediminas
• Granted Patent: US 8,062,224 B2
• Time in Patent Office: Days
• US Class Current: 600/454
• CPC Class Codes: A61B 5/08 Detecting, measuring or recording devices for evaluating the respiratory organs A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/4064 Evaluating the brain A61B5/031, A61B5/369, A61B5/14553 take precedence
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00

Abstract

A non-invasive method for continuous real-time monitoring of cerebrovascular blood flow autoregulation state includes simultaneous non-invasive monitoring of intracranial blood volume respiratory waves and lung volume respiratory waves, real-time decomposition of intracranial blood volume respiratory waves and lung volume respiratory waves into narrowband sinewave first harmonic components, determination therefrom of the phase shift between intracranial blood volume respiratory wave and lung volume respiratory wave first harmonics'"'"' and derivation of cerebrovascular autoregulation state from that phase shift value.

Claims

1. A method for continuous real-time cerebrovascular autoregulation state monitoring comprising the steps of:

monitoring intracranial blood volume respiratory waves to generate an information signal;

simultaneously monitoring lung volume respiratory waves to generate a reference signal;

generating an information signal;

generating a reference signal;

filtering said information signal into a first wave component;

filtering said reference signal into a second wave component;

determining the phase shift between said first signal wave component and said second wave component;

assigning a value to said phase shift; and

comparing the assigned phase shift value to a predetermined phase shift threshold value to determine the cerebrovascular autoregulation state.

2. The method of claim 1 wherein said first wave component and said second wave component are both first harmonic wave components.

3. The method of claim 1 wherein said phase shift threshold value is approximately 30 to 40 degrees.

4. The method of claim 3 including the step of determining said cerebrovascular autoregulation state is intact when said assigned phase shift value is equal or more than the threshold value.

5. The method of claim 3 including the step of determining said cerebrovascular autoregulation state is impaired when said assigned phase shift value is less than the threshold value.

6. The method of claim 1 further including displaying the cerebrovascular autoregulation state on a monitor.

7. The method of claim 5 further including activating an alarm when said cerebrovascular autoregulation state is determined to be impaired.

8. A method for continuous real-time cerebrovascular autoregulation state monitoring comprising the steps of:

non-invasively monitoring intracranial blood volume respiratory waves to create an information signal;

simultaneously non-invasively monitoring lung volume respiratory waves to create a reference signal;

filtering said intracranial blood volume respiratory waves and said lung volume respiratory waves into narrowband sine-wave first harmonic components;

determining the phase shift between the filtered intracranial blood volume respiratory wave and the filtered lung volume respiratory wave;

assigning a value to said phase shift;

predetermining a phase shift threshold value and storing said threshold value in a processor;

comparing the assigned phase shift value to the predetermined phase shift threshold value in a processor; and

activating an alarm when the assigned phase shift value is less than the phase shift threshold value.

9. An apparatus for continuous real-time cerebrovascular autoregulation state monitoring comprising:

a first sensor for measuring intracranial blood volume respiratory waves and generating a blood volume output measurement in the form of a wave;

a second sensor for measuring lung volume respiratory waves and generating a lung volume output measurement in the form of a wave;

a first filter connected to said first sensor for receiving the blood volume output wave measurement from the first sensor, filtering the blood volume output wave measurement and generating a first filter output;

a second filter connected to said second sensor for receiving the lung volume output wave measurement from the second sensor, filtering the lung volume output wave measurement and generating a second filter output;

a phase shift monitor connected to both the first filter and the second filter that receives the first filter output and second filter output and that compares the first filter output to the second filter output to determine the phase shift between the first filter output and second filter output, said phase shift monitor then generates a phase shift value output;

a processor for receiving the phase shift value output from the phase shift monitor, said processor also having a stored predetermined threshold value, and comparing said phase shift value output with said threshold value to determine the status of the cerebrovascular autoregulation state; and

a display connected to said processor for displaying information related to the status of the cerebrovascular autoregulation state.

10. The apparatus of claim 9 wherein said first sensor is a non-invasive sensor.

11. The apparatus of claim 9 wherein said second sensor is a non-invasive sensor.

12. The apparatus of claim 11 wherein said second sensor is a belt type lung respiratory wave transducer.

13. The apparatus of claim 9 wherein said first filter output comprises a component of the blood volume respiratory wave and said second filter output comprises a component of the lung volume respiratory wave.

14. The apparatus of claim 13 wherein said component of the blood volume respiratory wave and said components of the lung volume respiratory wave are sine wave first harmonic components.

15. The apparatus of claim 14 wherein the sine wave first harmonic component of the blood volume respiratory wave is derived from the formula A sin(ω

₁t−

Δ

φ

(t)).

16. The apparatus of claim 14 wherein the sine wave first harmonic component of the lung volume respiratory wave is derived from the formula Bsin(ω

₁t−

φ

₀(t))

17. The apparatus of claim 9 wherein said first and second filter are both adaptive band-pass filters.

18. The apparatus of claim 17 wherein said first and second filters are adaptive band-pass filters of the first harmonic of respiratory wave.

19. The apparatus of claim 9 wherein said first and second filters are connected to and controlled by a controller of adaptive filters.

20. The apparatus of claim 9 including a monitor connected to said phase shift monitor for visually displaying the phase shift value determined by the phase shift monitor.

21. The apparatus of claim 9 including an alarm connected to said processor for receiving a signal from said processor to activate said alarm if the processor determines the phase shift value falls below the threshold value indicating an impaired cerebrovascular autoregulation state.