System for measuring pulsatile vascular resistance

• US 7,794,403 B2
• Filed: 04/21/2005
• Issued: 09/14/2010
• Est. Priority Date: 04/21/2004
• Status: Active Grant

• Current Assignee: MEAR Holding BV
• Original Assignee: MEAR Holding BV
• Inventors: Schaafsma, Arjen
• Primary Examiner(s): Nasser; Robert L
• Application Number:
  US11/587,021
• Publication Number:
  US 20070293760A1
• Time in Patent Office: 1,972 Days
• Field of Search: None
• US Class Current: 600/485
• 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 5/4884 inducing physiological or psychological stress, e.g. applications for stress testing
• 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

The invention relates to acquiring information concerning the hemodynamic status of the brain (or any other organ) by measuring and analysing the pulsatile properties of blood flow (velocities) in the organ'"'"'s feeding vessels in relation to the pulsatile properties of the systemic arterial blood pressure. Provided is a system for the analysis of arterial blood flow velocity measurements, comprising means for receiving input signals delivered by an arterial blood flow velocity (FV) sensor and by an arterial blood pressure (BP) sensor, wherein said FV and BP signals are recorded simulataneously and continuously, further comprising means for processing and outputting signals, wherein said processing comprises calculating the pulsatile apparent resistance (PaR) or the Pulse Flow Velocity Mismatch (PFVM). Plotting PAR or PVFM against mean arterial blood pressure and/or end tidal CO2 levels can serve as an indicator for the effectiveness of imposed therapy.

Claims

1. A system for the analysis of arterial blood flow velocity measurements comprising means for receiving input signals delivered by an arterial blood flow velocity (FV) sensor and by an arterial blood pressure (BP) sensor, wherein said FV and BP signals are recorded simultaneously and continuously, further comprising means for processing and outputting signals, wherein said processing comprises:

synchronization of both signals at start upstroke,

a beat-to-beat analysis of the signals, whereby the pulsatile vascular resistance is calculated from the difference in relationship between FV and BP signals during systole compared to diastole.

2. A system according to claim 1 which further optionally comprises averaging to avoid respiratory effects;

and wherein the calculated pulsatile vascular resistance is the Pulsatile apparent Resistance (PaR).

3. A system according to claim 2, which comprises:

averaging the values for FV and BP over the systolic part or diastolic part of each heart cycle;

calculating the difference between the diastolic vascular resistance and the systolic vascular resistance;

determining the mean vascular resistance over a number of successive heartbeats, preferably ten or more; and

determining the PaR as the ratio between this difference and the mean vascular resistance.

4. A system according claim 1 wherein the calculated pulsatile vascular resistance is the Pulse Flow Velocity Mismatch (PFVM).

5. A system according to claim 4 which comprises:

normalizing said FV and BP signal with the minimal diastolic flow velocity or blood pressure set at 0 and the maximal systolic flow velocity or blood pressure set at 1;

calculating the mean normalized FV and the mean normalized BP over a time period in between two successive heart beats; and

determining the ratio between the mean normalized FV signal and the mean normalized BP signal (=PFVM).

6. A system according to claim 1, further comprising means for displaying input and processed signals and/or means for storing recorded or displayed input or processed signals.

7. A system according to claim 1, wherein said arterial blood flow velocity (FV) sensor detects the middle cerebral artery (MCA) flow velocity, preferably using transcranial Doppler technology.

8. A system according to claim 1, wherein said BP sensor comprises an intravascular catheter.

9. A system according to claim 1, wherein said BP sensor comprises a non-invasive sensor, preferably a non-invasive continuous finger blood pressure monitor.

10. Method for determining pulsatile vascular resistance (PVR), preferably pulsatile vascular cerebrovascular resistance, said method comprising the steps of:

recording an arterial blood flow velocity (FV) signal and an arterial blood pressure (BP) signal, wherein said FV and BP signals are recorded simultaneously and continuously;

synchronizing said FV and BP signal at start-upstroke;

optionally averaging said signals to avoid respiratory effects; and

calculating with a processing device the pulsatile vascular resistance in a beat-to-beat analysis of the signals, from the difference in relationship between FV and BP signals during systole compared to diastole.

11. Method according to claim 10 further comprising, diagnosing or monitoring a subject using the pulsatile vascular resistance.

12. Method according to claim 10 further comprising, diagnosing or monitoring a vascular disease or malfunction related to abnormal vascular resistance, preferably cerebrovascular resistance, or of elevated intracranial pressure using the pulsatile vascular resistance.

13. Method according to claim 10 in which the pulsatile apparent resistance (PaR), preferably cerebrovascular PaR, is calculated, said method comprising the steps of:

averaging the values for FV and BP over the systolic part or diastolic part of each heart cycle;

calculating the difference between the diastolic vascular resistance and the systolic vascular resistance;

determining the mean vascular resistance over a number of successive heartbeats, preferably ten or more; and

determining the PaR as the ratio between this difference and the mean vascular resistance.

14. Method according to claim 10, in which the Pulse Flow Velocity Mismatch (PFVM), preferably cerebrovascular PFVM, is calculated, said method comprising the steps of:

normalizing said FV and BP signal with the minimal diastolic flow velocity or blood pressure set at 0 and the maximal systolic flow velocity or blood pressure set at 1;

calculating the mean normalized FV and the mean normalized BP per time unit; and

determining the ratio between the mean normalized FV signal and the mean normalized BP signal.

15. Apparatus for performing the method of claim 10, comprising a sensor for continuously recording an arterial blood flow velocity (FV) signal and a sensor for continuously recording an arterial blood pressure (BP) signal, the sensors being connected to means for receiving input signals, further comprising a separate amplifier for FV and BP, which amplifiers generate signals which can be displayed on a display unit or recorded on a recording unit, said amplifiers both connected to a processor for performing signal analysis and calculation of the Pulsatile apparent Resistance (PaR) or Pulse Flow Velocity Mismatch (PFVM), said amplifiers and said processor being connected to a display unit or a recording unit or both.

16. Apparatus according to claim 15, comprising a transcranial Doppler ultrasound device and/or a non-invasive continuous finger blood pressure monitor.

17. Method according to claim 10, wherein the calculation is performed by a module for calculation of the pulsatile vascular resistance, said module being connected to apparatuses that measure blood flow velocity and blood pressure.