EP-4739206-A1 - SYSTEM AND METHOD FOR CONTINUOUSLY MEASURING A POSTURE-COMPENSATED HYDRATION OF A SUBJECT

EP4739206A1EP 4739206 A1EP4739206 A1EP 4739206A1EP-4739206-A1

Abstract

A system and method for continuously measuring a posture-compensated hydration of a subject, the system comprising: an accelerometer for measuring raw posture data of the subject at incremental time intervals; an electrode arrangement for measuring a bioimpedance signal; at least one processor; and storage media with instructions that, when executed on the processor, perform the tasks of: at a first time interval: a) deriving a continuous single posture dependent signal from the raw posture data; b) applying a transformation filter to the single posture dependent signal to shift the posture signal to align with the time domain of the bioimpedance signal, said transformation filter imitating a response to posture change of a body; c) normalising the filtered posture signal using posture normalisation parameters; d) normalising the bioimpedance signal using bioimpedance normalisation parameters; e) subtracting the normalised filtered posture signal from the normalised impedance signal; and f) renormalising the resulting subtracted signal using the bioimpedance normalisation parameters to find a continuous posture-compensated hydration signal; and repeating steps a) to f) for each subsequent incremental time interval; wherein, at the first time interval, posture normalisation parameters are based on predetermined average parameters for a selected demographic in which the subject is represented; and wherein, at each subsequent incremental time interval, posture normalisation parameters are adjusted based on each new measurement.

Inventors

SAETHER, TERJE
NORHEIM, JØRN
CECCHINATO, Daniele
AAS, Sigve Nyvik
BREMNES, Frida
HOGSTAD, Signe
NORE, Anders

Assignees

MODE SENSORS AS

Dates

Publication Date: 20260513
Application Date: 20250625

Claims (16)

P A T E N T C L A I M S 1. A system for continuously measuring a posture-compensated hydration of a subject, the system comprising: an accelerometer for measuring raw posture data of the subject at incremental time intervals; an electrode arrangement for measuring a bioimpedance signal; at least one processor; and storage media with instructions that, when executed on the processor, perform the tasks of: at a first time interval: a) deriving a continuous single posture dependent signal from the raw posture data; b) applying a transformation filter to the single posture dependent signal to shift the posture signal to align with the time domain of the bioimpedance signal, said transformation filter imitating a response to posture change of a body of the subject; c) normalising the filtered posture signal using posture normalisation parameters; d) normalising the bioimpedance signal using bioimpedance normalisation parameters; e) subtracting the normalised filtered posture signal from the normalised impedance signal; and f) renormalising the resulting subtracted signal using the bioimpedance normalisation parameters to find a continuous posture- compensated hydration signal; and repeating steps a) to f) for each subsequent incremental time interval; wherein, at the first time interval, posture normalisation parameters are based on predetermined average parameters for a selected demographic in which the subject is represented; and wherein, at each subsequent incremental time interval, posture normalisation parameters are adjusted based on each new measurement.
2. The system of claim 1, wherein the accelerometer is of a two-angle type configured to measure three vector components, and wherein the storage media comprises instructions that, when executed on the processor, perform the tasks of deriving a continuous single posture dependent signal by mapping the three vector components of the raw posture data.
3. The system of claim 1 or claim 2, wherein at least the accelerometer and the electrode arrangement of the system are implemented into a skin-adhering patch device.
4. The system of claim 3, wherein the patch device is in data communication with the at least one processor and the storage media with instructions, said processor and said storage media with instructions supported externally to the patch device.
5. The system of any of claims 1 to 4, wherein the storage media further comprises instructions that, when executed on the processor, perform the tasks of: normalising the filtered posture signal and the bioimpedance signal to scale to one another using a standard score normalisation.
6. The system of any preceding claim, wherein the storage media further comprises instructions that, when executed on the processor, perform the tasks of: optimising the bioimpedance normalisation parameters via a feedback loop from the renormalised bioimpedance signal.
7. The system of any preceding claim, wherein the transformation filter is adaptive to learn the particular fluid equilibrate delay times after different posture changes and movements over time for a specific monitored subject to learn a subject-dependent time constant.
8. The system of claim 7, wherein the transformation filter employs machine learning to learn the particular fluid equilibrate delay times after different posture changes and movements over time for a specific monitored subject to learn a subject-dependent time constant.
9. The system of any preceding claim, wherein the duration of the incremental time intervals is between 1 seconds and 180 seconds.
10. A method for continuously measuring a posture-compensated hydration of a subject, the method comprising: simultaneously and continuously measuring: raw posture data of the subject using an accelerometer at incremental time intervals; and a bioimpedance signal of the subject at incremental time intervals; deriving a continuous single posture dependent signal using the raw posture data; applying a transformation filter to the single posture dependent signal to shift the posture signal to align with the time domain of the bioimpedance signal, said transformation filter imitating a response to posture change of a body of the subject; normalising the filtered posture signal using posture normalisation parameters based on the raw posture data, said posture normalisation parameters adjusted with each new incremental time interval measurement; normalising the bioimpedance signal using bioimpedance normalisation parameters based on the bioimpedance signal, said normalisation parameters adjusted with each new measurement; subtracting the normalised filtered posture signal from the normalised impedance signal; and renormalising the resulting subtracted signal using the bioimpedance normalisation parameters to find a continuous posture-compensated hydration signal; wherein, at the first time interval t0, posture normalisation parameters are based on predetermined average parameters for a selected demographic in which the subject is represented and, at each subsequent incremental time interval, posture normalisation parameters are adjusted based on each new measurement.
11. The method of claim 10, wherein normalising the filtered posture signal and the bioimpedance signal to scale to one another comprises using a standard score normalisation.
12. The method of claim 10 or claim 11, further comprising optimising the bioimpedance normalisation parameters via a feedback loop from the renormalised bioimpedance signal.
13. The method of any of claims 10 to 12, wherein the accelerometer measures on two angles which is combined into three vector components for the three dimensions of space and the continuous single posture dependent signal is derived by mapping the three vector components.
14. The method of any of claims 10 to 13, wherein the duration of the incremental time intervals is between 1 seconds and 180 seconds.
15. The method of any of claims 10 to 14, further comprising employing machine learning to learn the particular fluid equilibrate delay times after different posture changes and movements over time for a specific monitored subject to learn a subject-dependent time constant of the transformation filter.
16. Computer readable medium comprising instructions that, when executed on a processor, perform the method of any of claims 10 to 15.

Description

SYSTEM AND METHOD FOR CONTINUOUSLY MEASURING A POSTURE- COMPENSATED HYDRATION OF A SUBJECT Background Bioimpedance is a technique that measures the resistance of biological tissue through small electrical currents, providing valuable data on physiological attributes of a subject such as fluid status. Patch devices can be used to measure said bioimpedance and provide health and fitness monitoring. A particularly useful application for bioimpedance measuring is to monitor hydration levels of a subject to maintain a balanced hydration and prevent imbalanced hydration such as underhydration, dehydration, overhydration and hyperhydration. Posture influences a distribution of fluid within the body. Since bioimpedance measurements rely on the principle that the body's tissues conduct electrical currents differently based on their composition and hydration levels, posture can significantly impact the accuracy of hydration measurements. When a subject changes posture, particularly from lying down to standing or vice versa, there are significant shifts in fluid distribution throughout the body which can distort bioimpedance derived hydration monitoring. Most current hydration measurement systems require a subject to maintain a consistent posture during measurements such that the bioimpedance measurements are accurate and reproducible. Variations in posture between measurement sessions in these systems can lead to inconsistencies, potentially resulting in inaccurate assessments of the subject’s fluid status. Some bioimpedance hydration measuring systems may receive information about the subject's posture from sensors such as accelerometers or cameras. Said posture detection can be used to set parameters in data acquisition in a static manner. Some systems that measure bioimpedance may be designed for calibration to determine appropriate parameters for acquiring bioimpedance signals tailored to a subject. Calibration results may be stored in the system's memory, allowing retrieval of suitable parameters based on different postures. These systems are not suitable for monitoring subjects with irregular posture patterns. Problems in the above systems occur when ongoing, continuous, accurate hydration monitoring is desired for subjects with irregular posture patterns, and for which static parameter calibration is inadequate. It is an object of the present invention to address some of the above-described limitations in the previous hydration monitoring systems. DUTT A G et al., Wearable bioimpedance for continuous and context-aware clinical monitoring, 202042nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC), pp 3985 – 3988 teaches bioimpedance monitoring provides a non-invasive, safe and affordable opportunity to monitor total body water for a wide range of clinical applications. However, the measurement is susceptible to variations in posture and movement. Existing devices do not account for these variations and are therefore unsuitable to perform continuous measurements to depict trend changes. We developed a wearable bioimpedance monitoring system with embedded real-time posture detection using a distributed accelerometer network. We tested the device on 14 healthy volunteers following a standardized protocol of posture change and evaluated the agreement with a commercial device. The impedance showed a high correlation (r>0.98), a bias of -4.5 Ω, and limits of agreement of -30 and 21 Ω. Context- awareness was achieved with an accuracy of 94.6% by classifying data from two accelerometers placed at the upper and lower leg. The calculated current consumption of the system was as low as 10 mA during continuous measurement operation, suggesting that the system can be used for continuous measurements over multiple days without charging. The proposed motion-aware design will enable the measurement of relevant bioimpedance parameters over long periods and support informed clinical decision making. US2019104989A1 discloses a method of monitoring hydration including obtaining biological data for a given period of time, wherein the biological data includes measurements of one or more biological indicators; converting the biological data into a baseline value; obtaining real-time biological data from one or more biological sensors; performing a pre-processing analysis of the real-time biological data; comparing the real-time biological data with baseline value to create a hydration index. EP4299001A1 discloses a device comprising a bioimpedance unit configured to periodically or irregularly sense a bioimpedance of at least one part of the body of the user via electrodes that touch a portion of the body around a limb or/and a portion of the body between the limbs of the user, a processing unit that determines at least one physiological parameter of the user based on the bioimpedance and anthropometric data of the user and estimates, based on the at least one physiological parameter, a