Method and device for detecting and assessing reactive hyperemia using segmental plethysmography

• US 9,668,662 B2
• Filed: 03/11/2014
• Issued: 06/06/2017
• Est. Priority Date: 06/02/2009
• Status: Active Grant

• Current Assignee: Cordex Systems, Inc.
• Original Assignee: Cordex Systems, Inc.
• Inventors: Whitt, Michael David, Magliato, Kathy Elizabeth, Ritterbush, Stephen
• Primary Examiner(s): WEARE, MEREDITH H
• Application Number:
  US14/204,678
• Publication Number:
  US 20140194754A1
• Time in Patent Office: 1,183 Days
• 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 5/02255 the pressure being controlled by plethysmographic signals, e.g. derived from optical sensors
• 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

Abstract

A method for measuring reactive hyperemia in a subject is disclosed. The method includes performing a first segmental cuff plethysmography to generate a baseline arterial compliance curve and/or a baseline pressure-area (P-A) curve, performing a second segmental cuff plethysmography to generate a hyperemic arterial compliance curve and/or a hyperemic P-A curve, and calculating an area between the baseline and the hyperemic curves. The size of the area can be used as an indication of endothelial dysfunction (ED) and ED-related diseases.

Claims

1. A system for measuring arterial blood flow in a subject, comprising:

an inflatable cuff;

a low-frequency metering pump for inflating the cuff, wherein the metering pump operates at a frequency that is not higher than arterial cycle frequency of the subject;

a pressure transducer for measuring pressure inside the cuff; and

a computer configured to;

generate a pressure descent curve and a cuff compliance curve by directly measuring volume change in said cuff with said metering pump and pressure change inside the cuff with said pressure transducer;

generate an arterial compliance (dV/dP)_artery curve during inflation and deflation processes of the cuff that allows determination of (dV/dP)_artery values at any transmural pressure;

calculate a derivative of said pressure descent curve to obtain a (dP/dt)_artery curve; and

multiply (dP/dt)_artery by (dV/dP)_artery to obtain an arterial flow (dV/dt)_artery curve.

2. The apparatus of claim 1, further comprising an amplifier.

3. The apparatus of claim 2, further comprising means for band pass filtering data.

4. A method for measuring arterial blood flow in a subject, comprising:

performing a first segmental cuff plethysmography on a portion of the body of the subject with the system of claim 1, wherein said performing comprises;

increasing cuff pressure in the inflatable cuff to a peak cuff pressure and immediately reducing cuff pressure in the inflatable cuff from the peak cuff pressure;

generating, with the computer, a pressure descent curve based on change in cuff pressure and cuff volume;

generating, with the computer, an arterial compliance (dV/dP)_artery curve that allows determination of (dV/dP)_artery values at any transmural pressure;

calculating, with the computer, a derivative of said pressure descent curve to obtain a (dP/dt)_artery curve; and

multiplying, with the computer (dP/dt)_artery by (dV/dP)_artery to obtain an arterial flow curve (dV/dt)_artery .

5. The method of claim 4, wherein a cuff compliance curve is generated using the metering pump to measure the volume change in the cuff and the pressure transducer to measure pressure change for each known volume change.

6. The method of claim 4, wherein the peak cuff pressure is in the range of 150-180 mmHg.

7. The method of claim 4, wherein the arterial compliance (dV/dP)_artery is obtained via the following equation:

(dV/dP)_artery =(dP)_artery ×

(dV/dP)_cuff

[P_sys −

P_dia]

wherein (dP)_artery is the magnitude of pressure pulses that take place at each cuff pressure, P_sys is systolic blood pressure, and P_dia is diastolic blood pressure.

8. The method of claim 7, wherein a band pass filtering method is used on the pressure descent curve to obtain P_sys and P_dia.