Methods and apparatuses for central venous pressure measurement status

Inventors

Robinson, Mark Ries • Allen, Elena A • Salehpour, Fahimeh

Assignees

Medici Technologies LLC

Abstract

Method and systems are provided for reliable, convenient, self-administered, and cost-effective determination of central venous pressure. The noninvasive method and apparatus use changes in transmural pressure to create detectable changes in peripheral venous vascular volume for the determination of central venous pressure. Transmural pressure changes can be manifested by intravascular or extravascular pressure changes. The system is noninvasive and uses optical measurements of venous volume in the presence of transmural pressure changes. The relationship between the transmural pressure change and the change in vascular venous volume is combined with anatomical measurements to determine the central venous pressure of the subject. Central venous pressure can be used to determine hemodynamic status of the subject to include fluid overload in the heart failure patient.

Core Innovation

The disclosed invention provides an apparatus for determining central venous pressure (CVP) of an individual by varying transmural pressure in the veins of a limb and using an optical measurement system that determines a measure of blood volume at each of a plurality of transmural pressures. The approach relies on identifying venous collapse and determining how blood volume changes versus applied transmural pressure to obtain a relationship usable for CVP determination.

A height determination device determines the height of the measurement region relative to an anatomical reference point, and an analysis system determines central venous pressure from the determined height and from the relationship between transmural pressure and blood volume. The physiological basis described includes venous distensibility in a low-pressure range and coupling between peripheral venous pressure and central venous pressure, while addressing measurement challenges related to arterial versus venous optical components, autonomic changes, time-delay and asymmetry in venous emptying versus filling, and contact-pressure artifacts.

The document describes multiple embodiments for varying transmural pressure, including mechanically changing hydrostatic conditions such as arm elevation, applying intravascular proximal pressure via an external cuff, applying intrathoracic pressure using resistance breathing, and using extravascular noncontact dynamic and static air pressure tonometry with pressure ramps, steps, or periodic modulations. It further describes optical venous sensing using wrist, bracelet, or ring imaging and direct vein imaging at specified wavelengths, including multispectral imaging and polarized reflectance to mitigate unwanted components.

Claims Coverage

The only independent claim explicitly provided covers the full apparatus for determining central venous pressure using a transmural-pressure varying mechanism in a limb, optical blood-volume determination at multiple transmural pressures, and height determination relative to an anatomical reference to compute CVP from an inferred relationship between transmural pressure and blood volume. The inventive features are supplemented by dependent-claim notes including pressure modulation scheme constraints, optical measurement specifics, and height and condition constraints.

Independent claim defines an apparatus combining transmural-pressure variation in limb veins, optical determination of blood volume across multiple transmural pressures, and height-based anatomical referencing, with an analysis system computing central venous pressure from the height and the transmural pressure versus blood-volume relationship. The provided dependent-claim notes indicate further narrowing in pressure modulation, optical sensing, and measurement conditions, including an inference condition linking transmural pressure at zero blood volume to the CVP calculation.

Stated Advantages

Documented Applications