Method and device for assessing the state of blood vessels

• US 5,715,826 A
• Filed: 03/08/1996
• Issued: 02/10/1998
• Est. Priority Date: 09/14/1993
• Status: Expired due to Term

• Current Assignee: Carefusion U.K. 232 Ltd. (Becton, Dickinson & Co)
• Original Assignee: British Technology Group Ltd.
• Inventors: Horrocks, Michael, Skidmore, Robert
• Primary Examiner(s): Bahr, Jennifer
• Assistant Examiner(s): YARNELL, BRYAN KEITH
• Application Number:
  US08/617,922
• Time in Patent Office: 704 Days
• Field of Search: 128/668, 128/672, 128/673, 128/675, 128/677-682, 128/687-690
• US Class Current: 600/485
• CPC Class Codes: A61B 5/02007 Evaluating blood vessel condition, e.g. elasticity, compliance
• CPC Class Codes: A61B 5/022 by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
• CPC Class Codes: A61B 5/7257 using Fourier transforms

Abstract

A method and device for use in assessing the state of blood vessels within the human or animal body is provided. A vessel segment is identified for investigation, and at least one blood pressure responsive device is used to obtain pulse volume recordings of different sites, representing pressure at sites proximal and distal to the vessel segment. From the waveform signals obtained, Fourier transform spectra are determined for the respective sites and the transfer function between them is calculated. This is then analyzed to determine a clinically significant parameter, such as the integral of the transfer function, and this can be compared with a predetermined value to provide an indication as to the state of the vessel segment.

Claims

1. A device suitable for use in an assessment of blood vessels within a human or animal body, comprising:

at least one blood pressure responsive device for application at different sites on the body;

pulse volume recorder means for coupling to the blood pressure responsive device or devices for producing waveform signals of pulsatile blood pressure at respective sites;

Fourier transform analyzing means for analyzing the waveform signals and obtaining Fourier transform spectra for respective sites;

transfer function computing means for determining a transfer function between respective sites;

transfer function analyzing means for directly extracting a clinically significant parameter of the transfer function;

a store of at least one predetermined value against which the transfer function parameter is compared; and

means for indicating a result of said comparison, indicative of the state of the blood vessel between the respective sites.

3. A device according to claim 1 or claim 2, including as a blood pressure responsive device a blood plethysmograph of inflatable cuff type.

2. A device suitable for use in an assessment of blood vessels within a human or animal body, comprising:

at least one blood pressure responsive device for application at different sites on the body;

pulse volume recorder means for coupling to the blood pressure responsive device or devices for producing waveform signals of pulsatile blood pressure at respective sites;

Fourier transform analyzing means for analyzing the waveform signals and obtaining Fourier transform spectra for respective sites;

transfer function computing means for determining a transfer function between respective sites;

transfer function analyzing means for directly extracting a clinically significant parameter of the transfer function;

a store of at least one predetermined value against which the transfer function parameter is compared; and

means for indicating a result of said comparison,

wherein said transfer function analyzing means is an integration means, the parameter being the integral of the transfer function.

4. A device according to claim 2, comprising at least two blood pressure responsive devices for simultaneous application at respective sites.

5. A device according to claim 2, including at least one selected from the group consisting of a display, printing and recording means.

6. A method for an assessment of blood vessels within a human or animal body comprising the steps of:

selecting a vessel segment for investigation;

obtaining pulse volume recordings (PVRs) representing pulsatile pressure at sites proximal and distal to the vessel segment;

performing Fourier transforms on the PVRs obtained at said proximal and distal sites, to obtain a proximal transform spectrum (FT_p) and a distal transform spectrum (FT_d);

determining a transfer function (TF) where

TF f!=FT_d f!/FT_p f!,

TF f!, FT_p f! and FT_d f! representing the respective values at frequency f;

extracting from TF a selected transfer function parameter;

comparing the selected transfer function parameter with a predetermined value; and

indicating a result of said comparison as representative of whether the vessel segment may be at risk.

7. A method according to claim 6, including the step of normalising FT_p and FT_d with respect to amplitude before determination of TF.

8. A method according to claim 6 or claim 7, wherein TF is integrated to obtain, as the selected parameter, a transfer function index n.

9. A method according to claim 6, wherein the PVR representing pulsatile pressure at one of the sites is obtained from an alternative reference site.

10. A method according to claim 9, wherein the sites selected are at a brachial position and a femoral position, representing respectively sites proximal and distal to an iliac arterial segment.

11. A method according to claim 6, wherein the PVRs are obtained simultaneously from said proximal and distal sites.

12. A method according to claim 6, wherein a number of selected transfer function parameters giving information of clinical significance are obtained from analyzing TF.