System for determining fluid level in a biological subject

Inventors

Kendall, Mark Anthony Fernance • Wilson, Stephen James • BREWER, Anthony Mark

Assignees

WearOptimo Pty Ltd

Abstract

A system for performing fluid level measurements on a biological subject, the system including at least one substrate including a plurality of microstructures configured to breach a stratum corneum of the subject, at least some microstructures including an electrode, a signal generator operatively connected to at least one microstructure to apply an electrical stimulatory signal to the at least one microstructure and at least one sensor operatively connected to at least one microstructure, the at least one sensor being configured to measure electrical response signals from at least one microstructure. The system also includes one or more electronic processing devices that determine measured response signals, the response signals being at least partially indicative of a bioimpedance and perform an analysis at least in part using the measured response signals to determine at least one indicator at least partially indicative of fluid levels in the subject.

Core Innovation

The disclosure describes a wearable system for performing fluid level measurements on a biological subject. The system includes a substrate having a plurality of conductive microstructures configured to breach a stratum corneum into the viable epidermis, where the microstructures act as electrodes. At least some microstructures include an insulating layer extending over an end proximate the substrate so that a tip portion remains uncoated and acts as the electrode, and at least some microstructures include a shoulder configured to abut against the stratum corneum to control depth of penetration.

The system applies an electrical stimulatory signal between microstructures in a microstructure pair, with respective electrodes in opposition from one microstructure and another microstructure so that the electrical stimulatory signal generates an electric field between the electrodes. A sensor measures electrical response signals between the microstructures in the pair, and the response signals are at least partially indicative of bioimpedance. Electronic processing devices determine measured electrical response signals and perform an analysis to determine at least one indicator at least partially indicative of fluid levels in the subject.

The disclosed analysis uses repeated measurements over a time period so that changes in impedance are used to track changes in fluid levels over time. The disclosure further characterizes measurement as being performed in the viable epidermis to derive indicators related to hydration and interstitial fluid and ion concentration conditions, including changes in those parameters and fluid volume and hydration levels. Experimental validation is described using impedance correlating with hydration in pig skin and human interstitial fluid measurements, including detection below clinical dehydration thresholds, together with tolerability and penetration confirmation.

Claims Coverage

The document provides two independent claims, each centered on using conductive microstructures that breach the stratum corneum to apply an electrical stimulatory signal and measure electrical response signals indicative of bioimpedance, followed by repeated time-series impedance analysis to determine indicators of fluid levels. Across both independent claims, the main inventive features are the microstructure/electrode architecture, opposed microstructure electrode pairing for electric field generation, sensor measurement of response signals, and impedance-based repeated tracking of fluid-level changes over time.

Across the independent claims, fluid-level measurement is achieved by controlled-depth microstructure electrodes that remain uncoated at the conductive tip, opposed microstructure pairing to generate an electric field, sensing of electrical response signals indicative of bioimpedance, and impedance-based analysis using repeated measurements over time to track changes in fluid levels.

Stated Advantages

Documented Applications