US20160022156A1

US20160022156A1 - Device and method having automatic user-responsive and user-specific physiological-meter platform

Info

Publication number: US20160022156A1
Application number: US14/806,430
Authority: US
Inventors: Gregory T. Kovacs; Laurent B. Giovangrandi; Robert Bruce Darling
Original assignee: PhysioWave Inc
Current assignee: PhysioWave Inc
Priority date: 2014-07-15
Filing date: 2015-07-22
Publication date: 2016-01-28
Also published as: EP3179903A1; WO2016014627A1; US10130273B2; US20150359486A1

Abstract

Aspects of the present disclosure are directed to a CPU and a memory circuit that has user-corresponding data stored on the memory circuit, and a platform over which a plurality of electrodes are interleaved, and configured for engaging the user. Based on a plurality of impedance-measurement signals being obtained from the electrodes, signals are generated that correspond to cardiovascular timings specific to the user. In such aspects of the present disclosure, pulse characteristic signals are determined based on the plurality of impedance-measurement signals and comparisons of user-obtained data are made relative to user-data profiles stored in the memory circuit.

Description

BACKGROUND

A variety of different physiological characteristics are monitored for many different applications. For instance, physiological monitoring instruments are often used to measure a number of patient vital signs, including blood oxygen level, body temperature, respiration rate and electrical activity for electrocardiogram (ECG) or electroencephalogram (EEG) measurements. For ECG measurements, a number of electrocardiograph leads may be connected to a patient's skin, and are used to obtain a signal from the patient.
Obtaining physiological signals can often require specialty equipment and intervention with medical professionals. For many applications, such requirements may be costly or burdensome. These and other matters have presented challenges to monitoring physiological characteristics.

SUMMARY OF THE DISCLOSURE

Various aspects of the present disclosure are directed toward methods, systems and apparatuses that are useful in making impedance-based measurements.
Various aspects of the present disclosure are directed toward multisensory user-specific biometric devices, systems and methods. Aspects of the present disclosure include user-interactive platforms, such as scales, large and/or full platform-area or dominating-area displays and related weighing devices, systems, and methods. Additionally, the present disclosure relates to electronic body scales that use impedance-based biometric measurements. Various other aspects of the present disclosure are directed to biometrics measurements such as body composition and cardiovascular information. Impedance measurements can be made through the feet to measure fat percentage, muscle mass percentage and body water percentage. Additionally, foot impedance-based cardiovascular measurements can be made for an ECG and sensing the properties of blood pulsations in the arteries, also known as impedance plethysmography (IPG), where both techniques can be used to quantify heart rate and/or pulse arrival timings (PAT). Cardiovascular IPG measures the change in impedance through the corresponding arteries between the sensing electrode pair segments synchronous to each heartbeat.
In certain embodiments, the present disclosure is directed to apparatuses and methods including a CPU and a memory circuit with user-corresponding data stored in the memory circuit, and a platform over which a plurality of electrodes are interleaved and configured and arranged for engaging a user. A plurality of measurement signals is obtained while a set of electrodes are concurrently contacting the user. While the plurality of electrodes is concurrently contacting a limb or other extremity of the user, a plurality of impendence-measurement signals is obtained from the plurality of electrodes. These impendence-measurement signals may (optionally) be the above-noted measurement signals. Based on biometrics of the user while approaching the platform, assessing who the user is while on the platform, and/or the plurality of measurement signals obtained from the plurality of electrodes, the CPU is used to access the user-corresponding data stored in the memory circuit, and thereby automatically recognize the user. This recognition is used for one or more of a variety of actions including, among others, transitioning from a low-power mode to a higher (power-up) mode, logging the user into the system and user-based logging of data and usages, and assessing which set of platform electrodes to use for obtaining the impendence-measurement signals. Based on a plurality of impedance-measurement signals being obtained from the electrodes while contacting the user, user-specific signals are generated and that correspond to the cardiovascular timings of the user.
In another embodiment, a plurality of impedance-measurement signals is obtained while a set of at least three electrodes are concurrently contacting a user. One of the plurality of impedance-measurement signals is obtained from two of the electrodes contacting one foot of the user with at least one other of the plurality of impedance-measurement signals being obtained between the one foot and a location of the user (e.g., along a lower limb, other foot, hand, shoulder) that does not include the one foot. A plurality of pulse characteristic signals are determined based on the plurality of impedance-measurement signals, with one of the pulse characteristic signals being extracted from one of the impedance-measurement signals and used as a timing reference to extract and process another of the pulse characteristic signals.
Another example embodiment is directed toward an apparatus that includes an impedance-measurement circuit that obtains a plurality of impedance-measurement signals via a set of electrodes while each of the electrodes is concurrently contacting a user. The set of electrodes includes a plurality of electrodes that contact one foot of the user, and includes at least one other electrode for contacting the user at a location that does not include the one foot (e.g., along a lower limb, other foot, hand, shoulder). The apparatus also includes a second circuit that determines a plurality of pulse characteristic signals based on the plurality of impedance-measurement signals. At least one of the impedance-measurement signals is obtained within the one foot and another of the impedance-measurement signals is obtained between the one foot and the other location. One of the pulse characteristic signals is extracted from one of the impedance-measurement signals and is used as a timing reference to extract and process another of the pulse characteristic signals.
In another embodiment, an apparatus includes a base unit including a platform area. The apparatus also includes a set of electrodes including a plurality of electrodes over the platform area for contacting one foot of a user and including at least one other electrode configured and arranged for contacting the user at a location along a lower limb (e.g., other foot) that does not include the one foot. Additionally, the apparatus includes pulse-processing circuitry communicatively coupled to, and configured with, the set of electrodes to obtain a plurality of (first and second) impedance-measurement signals while each of the electrodes is concurrently contacting the user and to determine a plurality of (first and second) pulse characteristic signals based on the plurality of (first and second) impedance-measurement signals. At least one of the (first) impedance-measurement signals is obtained within the one foot and another of the (second) impedance-measurement signals is obtained between the one foot and the other location. One of the (first and second) pulse characteristic signals is extracted from one of the impedance-measurement signals and is used as a timing reference to extract and process another of the pulse characteristic signals.
Another embodiment is directed to an apparatus having a base unit including a platform area, a set of electrodes and pulse-processing circuitry. The electrodes include a plurality of electrodes over the platform area for contacting a user at a limb extremity (being the hand or foot) and one or more other electrodes for contacting the user at a different location. The pulse-processing circuitry is communicatively coupled to, and configured with, the set of electrodes to obtain a plurality of (first and second) impedance-measurement signals while each of the electrodes is concurrently contacting the user and to determine a plurality of (first and second) pulse characteristic signals based on the plurality of (first and second) impedance-measurement signals. At least one of the (first) impedance-measurement signals is obtained within the limb extremity and another of the (second) impedance-measurement signals is obtained between the limb extremity and the other location. One of the (first and second) pulse characteristic signals is extracted from one of the impedance-measurement signals and is used as a timing reference to extract and process another of the pulse characteristic signals.
The above discussion/summary is not intended to describe each embodiment or every implementation of the present disclosure. The figures and detailed description that follow also exemplify various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Various example embodiments may be more completely understood in consideration of the following detailed description in connection with the accompanying drawings, in which:

FIG. 1 shows current paths through the body for the IPG trigger pulse and Foot IPG, consistent with various aspects of the present disclosure;

FIG. 1 a is a flow chart illustrating an example manner in which a user-specific physiologic meter/scale may be programmed to provide features consistent with aspects of the present disclosure;

FIG. 2 shows an example of the insensitivity to foot placement on scale electrodes with multiple excitation and sensing current paths, consistent with various aspects of the present disclosure;

FIGS. 3 a-3 b show example block diagrams depicting circuitry for sensing and measuring the cardiovascular time-varying IPG raw signals and steps to obtain a filtered IPG waveform, consistent with various aspects of the present disclosure;

FIG. 3 c depicts an example block diagram of circuitry for operating core circuits and modules, including for example those of FIGS. 3 a-3 b, used in various specific embodiments of the present disclosure;

FIG. 3 d shows an exemplary block diagram depicting the circuitry for interpreting signals received from electrodes.

FIG. 4 shows an example block diagram depicting signal processing steps to obtain fiducial references from the individual Leg IPG “beats,” which are subsequently used to obtain fiducials in the Foot IPG, consistent with various aspects of the present disclosure;

FIG. 5 shows an example flowchart depicting signal processing to segment individual Foot IPG “beats” to produce an averaged IPG waveform of improved SNR, which is subsequently used to determine the fiducial of the averaged Foot IPG, consistent with various aspects of the present disclosure;

FIG. 6 a shows examples of the Leg IPG signal with fiducials; the segmented Leg IPG into beats; and the ensemble-averaged Leg IPG beat with fiducials and calculated SNR, for an exemplary high-quality recording, consistent with various aspects of the present disclosure;

FIG. 6 b shows examples of the Foot IPG signal with fiducials derived from the Leg IPG fiducials; the segmented Foot IPG into beats; and the ensemble-averaged Foot IPG beat with fiducials and calculated SNR, for an exemplary high-quality recording, consistent with various aspects of the present disclosure;

FIG. 7 a shows examples of the Leg IPG signal with fiducials; the segmented Leg IPG into beats; and the ensemble averaged Leg IPG beat with fiducials and calculated SNR, for an exemplary low-quality recording, consistent with various aspects of the present disclosure;

FIG. 7 b shows examples of the Foot IPG signal with fiducials derived from the Leg IPG fiducials; the segmented Foot IPG into beats; and the ensemble-averaged Foot IPG beat with fiducials and calculated SNR, for an exemplary low-quality recording, consistent with various aspects of the present disclosure;

FIG. 8 shows an example correlation plot for the reliability in obtaining the low SNR Foot IPG pulse for a 30-second recording, using the first impedance signal as the trigger pulse, from a study including 61 test subjects with various heart rates, consistent with various aspects of the present disclosure;

FIGS. 9 a-b show an example configuration to obtain the pulse transit time (PTT), using the first IPG as the triggering pulse for the Foot IPG and ballistocardiogram (BCG), consistent with various aspects of the present disclosure;

FIG. 10 shows nomenclature and relationships of various cardiovascular timings, consistent with various aspects of the present disclosure;

FIG. 11 shows an example graph of PTT correlations for two detection methods (white dots) Foot IPG only, and (black dots) Dual-IPG method, consistent with various aspects of the present disclosure;

FIG. 12 shows an example graph of pulse wave velocity (PWV) obtained from the present disclosure compared to the ages of 61 human test subjects, consistent with various aspects of the present disclosure;

FIG. 13 shows another example of a scale with interleaved foot electrodes to inject and sense current from one foot to another foot, and within one foot, consistent with various aspects of the present disclosure;

FIG. 14 a shows another example of a scale with interleaved foot electrodes to inject and sense current from one foot to another foot, and measure Foot IPG signals in both feet, consistent with various aspects of the present disclosure;

FIG. 14 b shows another example of a scale with interleaved foot electrodes to inject and sense current from one foot to another foot, and measure Foot IPG signals in both feet, consistent with various aspects of the present disclosure;

FIG. 14 c shows another example approach to floating current sources is the use of transformer-coupled current sources, consistent with various aspects of the present disclosure;

FIGS. 15 a, 15 b, 15 c and 15 d show an example breakdown of a scale with and relevant to interleaved foot electrodes to inject and sense current from one foot to another foot, and within one foot, consistent with various aspects of the present disclosure, with FIG. 15 a showing a top view as in previous figures;

FIG. 16 shows an example block diagram of circuit-based building blocks, consistent with various aspects of the present disclosure;

FIG. 17 shows an example flow diagram, consistent with various aspects of the present disclosure;

FIG. 18 shows an example scale communicatively coupled to a wireless device, consistent with various aspects of the present disclosure; and

FIGS. 19 a-c show example impedance as measured through different parts of the foot based on the foot position, consistent with various aspects of the present disclosure.

While various embodiments discussed herein are amenable to modifications and alternative forms, aspects thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure including aspects defined in the claims. In addition, the term “example” as used throughout this application is only by way of illustration, and not limitation.

DESCRIPTION

Various aspects of the present disclosure relate to the sensing, detection, and quantification of at least two simultaneously acquired impedance-based signals. The simultaneously acquired impedance-based signals are associated with quasi-periodic electro-mechanical cardiovascular functions, and simultaneous cardiovascular signals measured by the impedance sensors, due to the beating of an individual's heart, where the measured signals are used to determine at least one cardiovascular related characteristic of the user for determining the heart activity, health, or abnormality associated with the user's cardiovascular system. The sensors can be embedded in a user platform, such as a weighing scale-based platform, where the user stands stationary on the platform, with the user's feet in contact with the platform, where the impedance measurements are obtained where the user is standing with bare feet.
Additionally, certain aspects of the present disclosure are directed toward methods that include obtaining a plurality of impedance-measurement signals while a set of electrodes are concurrently contacting a user. One of the plurality of impedance-measurement signals is obtained from two of the electrodes contacting one foot of the user and at least one other of the plurality of impedance-measurement signals being obtained between the one foot and a location of the user (e.g., along a lower limb, other foot, hand, shoulder) that does not include the one foot. Additionally, the method includes determining a plurality of pulse characteristic signals based on the plurality of impedance-measurement signals, wherein one of the pulse characteristic signals is extracted from one of the impedance-measurement signals and is used as a timing reference to extract and process another of the pulse characteristic signals.
In certain embodiments, the plurality of impedance-measurement signals includes at least two impedance-measurement signals between the one foot and the other location. The plurality of pulse characteristic signals are determined by assessing, as part of a signal optimization process, impedance-measurement signals including the at least two other impedance-measurement signals. Further, in certain embodiments, a signal is obtained, based on the timing reference, which is indicative of synchronous information and that corresponds to information in a BCG. Additionally, the methods can include conveying modulated current between selected ones of the electrodes. The plurality of impedance-measurement signals may, for example, be carried out in response to current conveyed between selected ones of the electrodes. Additionally, the methods, consistent with various aspects of the present disclosure, include a step of providing an IPG measurement within the one foot. Additionally, in certain embodiments, the two electrodes contacting one foot of the user are configured in an inter-digitated pattern of positions over a base unit that contains circuitry communicatively coupled to the inter-digitated pattern. The circuitry uses the inter-digitated pattern of positions for the step of determining a plurality of pulse characteristic signals based on the plurality of impedance-measurement signals, and for providing an IPG measurement within the one foot.
For embodiments involving a weighing scale or other platform that the user, and similarly-situated personnel (e.g., co-workers, friends, roommates, colleagues), would use in the home, office or other such venues on a regular and frequent basis, the present disclosure is directed to a substantially-enclosed apparatus, as would be a weighing scale, wherein the apparatus includes a platform which is part of a housing or enclosure. The platform includes a surface area with electrodes that are interleaved and configured and arranged for engaging a user as he or she steps onto the platform. Within the housing is a CPU (e.g., one or more computer processor circuits) and a memory circuit with user-corresponding data stored in the memory circuit. The platform, over which the electrodes are interleaved, are integrated and communicatively connected with the CPU. The CPU is programmed with modules as a set of integrated circuitry which is configured and arranged for automatically obtaining a plurality of measurement signals from the plurality of electrodes. As is advantageous for operation by a battery circuit (with a limited supply of energy), this integrated circuitry operates in a reduced power-consumption mode and at least one higher power-consumption mode of operation. The CPU and the memory circuit are configured and arrange with the electrodes to operate as follows: while the plurality of electrodes are concurrently contacting a limb of the user, operating the integrated circuitry and therefrom automatically obtaining the plurality of measurement signals from the plurality of electrodes; before obtaining a plurality of measurement signals by operating the circuitry, using a signal-sense circuit to sense wireless-signals indicative of the user approaching the platform and, in response, causing the circuitry to transition from the reduced power-consumption mode of operation and at least one higher power-consumption mode of operation; and after the circuitry is operating in the at least one higher power-consumption mode of operation, causing the CPU to access the user-corresponding data stored in the memory circuit and thereafter cause a plurality of impedance-measurement signals to be obtained by using the plurality of electrodes while they are contacting the user via the platform and, therefrom, generating signals corresponding to cardiovascular timings of the user.
The platform apparatus can also include a camera configured and arranged to be activated in response to a motion detection indication, such as from a PIR circuit and a responsive CPU module that evaluates the amount of radiation received by the PIR circuit. The camera is configured to capture at least one image of the user (whether still image(s) or a short video) while the user is on the platform or approaching the platform (as the user's motion is sensed and detected). The CPU then stores the user image(s) in the memory circuit for retrieval at a later time for verification (e.g., administrative, medical or security personnel) of correspondence between the user and biometric or physiological data stored as being specific to the user. The CPU can also be configured to permit remote access to the memory circuit by an authorized agent of medical or security personnel by using an authorized access protocol.
Consistent with some of the above aspects, in specific implementations, the platform apparatus has a signal-sense circuit configured with or as a passive infrared (PIR) circuit, and the CPU programmed to sense the user approaching the platform. The CPU wakes up in response to the signal-sense circuit and to the motion detection indication as provided and determined by the CPU. When equipped with a camera, the camera is activated in response to the motion detection and captures user images while the user is approaching the platform or while the user is on the platform. Further, a user-output device can be included in the form of one of a speaker, a display visible through the platform and/or a foot-tactile vibration circuit. The foot-tactile vibration circuit is responsive to the CPU and wherein the user-output device is configured and arranged to communicate with the user while the user is engaging the platform. Thus, in certain more-important applications such as those pertaining to provision of medical opinions or more critical bio-identification applications, the platform apparatus permits access to the user-specific data stored and logged in the memory circuit by an authorized agent of medical or security personnel by using an authorized access protocol; whereas other user-specific data pertinent to the user, such as impedance measurements performed while the user is on the platform apparatus, is provided as feedback to the user concurrent with the use.
In other related embodiments, the platform apparatus's signal-sense circuit is configured with the CPU to effect a learning of which user is about to step on, or has stepped on, the platform in preparation for selecting the appropriate electrodes for obtaining the plurality of impedance-measurement signals. These learnings, which can be stored in and retrieved from the memory circuit for comparison to previous logs or recordings. For example, selecting the appropriate electrodes can be based on user-recognition/identification and/or measurement results that indicate one or more of the following user-specific attributes: foot impedance, foot length, and type of arch. Any one or more of these can be used as an indication of a level of confidence of as identifying or corresponding to bio-metric attributes specific to the user.
In medical (and security) applications, for example, the impedance measurements obtained from the plurality of interleaved electrodes can then be used to provide various cardio-related information that is user-specific including, as non-limiting examples, synchronous information obtained from the user and that corresponds to information in a ballistocardiogram (BCG) and an impedance plethysmography (IPG) measurements. By ensuring that the user, for whom such data was obtained, matches other bio-metric data as obtained concurrently for the same user, medical (and security) personnel can then assess, diagnose and/or identify with high degrees of confidence and accuracy.
Other embodiments of the present disclosure are directed toward an apparatus that includes an impedance-measurement circuit that obtains a plurality of impedance-measurement signals via a set of electrodes while each of the electrodes is concurrently contacting a user (e.g., with the electrodes being part of the impedance-measurement circuit). The set of electrodes includes a plurality of electrodes for contacting one foot of the user and including at least another electrode for contacting the user at a location (e.g., along a lower limb, other foot, hand, shoulder) that does not include the one foot. The apparatus also includes a second circuit that determines a plurality of pulse characteristic signals based on the plurality of impedance-measurement signals. At least one of the impedance-measurement signals are obtained within the one foot and another of the impedance-measurement signals is obtained between the one foot and the other location. One of the pulse characteristic signals is extracted from one of the impedance-measurement signals and is used as a timing reference to extract and process another of the pulse characteristic signals.
In certain embodiments, the second circuit determines the pulse characteristic signals by comparing and assessing the impedance-measurement signals as part of a signal optimization process. The impedance-measurement signals include a foot impedance-measurement signal within the one foot, and at least two other impedance-measurement signals are measured between the one foot and the other location. The second circuit also determines the pulse characteristic signals by assessing, as part of a signal optimization process, each of the foot impedance-measurement signals and the at least two other impedance-measurement signals.
Other embodiments of the present disclosure are directed toward apparatuses that include a base unit including a platform area. The apparatus also includes a set of electrodes including a plurality of electrodes over the platform area for contacting one foot of a user, and at least one other electrode for contacting the user at a location along a lower limb that does not include the one foot (e.g., other foot). Additionally, the apparatus includes pulse-processing circuitry communicatively coupled to, and configured with, the set of electrodes to obtain a plurality of (first and second) impedance-measurement signals while each of the electrodes is concurrently contacting the user and. The pulse-processing circuity and electrodes also determine a plurality of (first and second) pulse characteristic signals based on the plurality of (first and second) impedance-measurement signals. At least one of the (first) impedance-measurement signals is obtained within the one foot and another of the (second) impedance-measurement signals is obtained between the one foot and the other location. One of the (first and second) pulse characteristic signals is extracted from one of the impedance-measurement signals and is used as a timing reference to extract and process another of the pulse characteristic signals.
In certain embodiments, the base unit houses the pulse-processing circuitry, and the lower limb location of the user is on the other foot. Further, the pulse characteristic signals can indicate pulse arrival times. Additionally, in certain embodiments, the set of electrodes includes at least four electrodes. In these embodiments, the pulse-processing circuitry is configured to obtain at least four impedance-measurement signals while each of the electrodes is concurrently contacting the user. The pulse-processing circuitry also determines the plurality of pulse characteristic signals by comparing at least two of the plurality of impedance-measurement signals and selecting one of the compared plurality of impedance-measurement signals over another of the compared plurality of impedance-measurement signals. Further, the pulse-processing circuitry can obtain a signal indicative of synchronous information based on the timing reference. Additionally, the pulse-processing circuitry can obtain a signal indicative of synchronous information based on the timing reference. The signal containing (or indicative of) synchronous information may correspond to information in a BCG or impedance cardiogram. Further, the pulse-processing circuitry and the set of electrodes can introduce an injection impedance signal to the user and to sense, in response, a return impedance signal.
Other embodiments of the present disclosure are directed to a plurality of electrodes that operate with pulse-processing circuitry to provide an IPG measurement within the one foot. The electrodes can be configured in an inter-digitated pattern of positions over the platform. The pulse-processing circuitry can use the inter-digitated pattern of positions to provide an IPG measurement within the one foot.
Certain embodiments of the present disclosure employ current-sourcing circuitry for presenting a plurality of current-injection signals to respective ones of the set of electrodes, with at least one of the current-injection signals modulated for current differentiation. Two injection electrodes impose current to the user from the current-sourcing circuitry. The pulse-processing circuitry senses the current-injection signals in two distinct body segments of the user. In certain more specific embodiments, the two distinct body segments respectively include a foot segment of the user and a segment including the legs of the user. The pulse-processing circuitry can provide leg and foot impedance measurements based on synchronous demodulation of the current-injection signals.
In some embodiments, the set of electrodes includes an electrode pattern element and are characterized as having a resistivity lower than 300 ohms/square and including at least one of indium tin oxide (ITO), stainless steel, aluminum and tantalum. Additionally, certain embodiments of the present disclosure employ a weighing scale, in which the base unit is integral with a housing that encloses the weighing scale and the pulse-processing circuitry. The platform area of the base unit provides a user-standing area sufficient for the user to stand with both of the feet on the platform area. The set of electrodes may include a pattern of interleaved Kelvin electrode pairs for the one foot. In certain more specific embodiments, the pattern of interleaved Kelvin electrode pairs mitigate sensitivity to foot placement on the platform area.
In certain embodiments, the electrodes include a pattern of at least two interleaved Kelvin electrode pairs for the one foot that mitigate sensitivity to foot placement on the platform area, thereby mitigating impedance-measurement interference caused by movements of the user. Certain embodiments of the present disclosure can include BCG sensing circuitry and an electrode pattern element that defines the plurality of electrodes for the one foot. The pulse-processing circuitry can be configured with the BCG sensing circuitry and the electrode pattern element to provide data for measuring arterial pulse wave velocity (“aPWV data”) and, in response, to augment the aPWV data with data obtained by BCG sensing.
In certain embodiments, the lower limb location is the other foot. In these such embodiments, the set of electrodes includes a pattern of at least two interleaved Kelvin electrode pairs for the one foot which are configured to mitigate sensitivity to foot placement on the platform area, thereby mitigating impedance-measurement interference caused by movements of the user. Additionally, in certain embodiments the pulse-processing circuitry determines the plurality of pulse characteristic signals within 60 seconds from when the user initially stands on the platform area.
Apparatuses, consistent with the present disclosure, can include a base unit having a platform area, a set of electrodes and pulse-processing circuitry. The electrodes include a plurality of electrodes configured over the platform area for contacting a user at a limb extremity, being the hand or foot, and at least one other electrode for contacting the user at a different location. The pulse-processing circuitry is communicatively coupled to, and configured with, the set of electrodes to obtain a plurality of (first and second) impedance-measurement signals while each of the electrodes is concurrently contacting the user and to determine a plurality of (first and second) pulse characteristic signals based on the plurality of (first and second) impedance-measurement signals. Additionally, at least one of the (first) impedance-measurement signals are obtained within the limb extremity and another of the (second) impedance-measurement signals are obtained between the limb extremity and the other location. One of the (first and second) pulse characteristic signals is extracted from one of the impedance-measurement signals and is used as a timing reference to extract and process another of the pulse characteristic signals.
In certain embodiments, the set of electrodes includes a pattern of interleaved Kelvin electrode pairs for the limb extremity. Further, the set of electrodes can include a pattern of at least two interleaved Kelvin electrode pairs for the limb extremity which are configured to mitigate sensitivity to placement of the limb extremity on the platform area, thereby mitigating impedance-measurement interference caused by movements of the user.
Additionally, certain embodiments use a 4-electrode bioelectronal impedance analysis (BIA) scale, where foot-to-foot IPG uses a Kelvin connection (as for standard BIA). Additionally, certain embodiments of the present disclosure use an impedance signal other than foot-to-foot as reference. It is possible to use the same approach using an impedance signal between the hand and the foot.
Turning now to the figures, FIG. 1 shows current paths 100 through the body of a user 105 standing on a scale 110 for the IPG trigger pulse and Foot IPG, consistent with various aspects of the present disclosure. Impedance measurements 115 are measured when the user 105 is standing and wearing clothing articles over the feet such as socks or shoes, within the practical limitations of capacitive-based impedance sensing, with energy limits considered safe for human use. The measurements 115 can also be made with non-clothing material placed between the user's bare feet and contact electrodes, such as thin films or sheets of plastic, glass, paper or wax paper, whereby the electrodes operate within energy limits considered safe for human use. The IPG measurements also can be sensed in the presence of callouses on the user's feet that normally diminish the quality of the signal.
As shown in FIG. 1, the user 105 is standing on a scale 110, where the tissues of the user's body will be modeled as a series of impedance elements, and where the time-varying impedance elements change in response to cardiovascular and non-cardiovascular movements of the user. ECG and IPG measurements can be sensed through the feet and can be challenging to take due to small impedance signals with (1) low SNR, and because they are (2) frequently masked or distorted by other electrical activity in the body such as the muscle firings in the legs to maintain balance. The human body is unsteady while standing still, and constant changes in weight distribution occur to maintain balance. As such, cardiovascular signals that are measured with weighing scale-based sensors typically yield signals with poor SNR, such as the Foot IPG and standing BCG. Thus, such scale-based signals require a stable and high quality synchronous timing reference, to segment individual heartbeat-related signals for signal averaging to yield an averaged signal with higher SNR versus respective individual measurements.
The ECG can be used as the reference (or trigger) signal to segment a series of heartbeat-related signals measured by secondary sensors (optical, electrical, magnetic, pressure, microwave, piezo, etc.) for averaging a series of heartbeat-related signals together, to improve the SNR of the secondary measurement. The ECG has an intrinsically high SNR when measured with body-worn gel electrodes, or via dry electrodes on handgrip sensors. In contrast, the ECG has a low SNR when measured using foot electrodes while standing on said scale platforms; unless the user is standing perfectly still to eliminate electrical noises from the leg muscles firing due to body motion. As such, ECG measurements at the feet while standing are considered to be an unreliable trigger signal (low SNR). Therefore, it is often difficult to obtain a reliable cardiovascular trigger reference timing when using ECG sensors incorporated in base scale platform devices. Both Inan, et al. (IEEE Transactions on Information Technology in Biomedicine, 14:5, 1188-1196, 2010) and Shin, et al. (Physiological Measurement, 30, 679-693, 2009) have shown that the ECG component of the electrical signal measured between the two feet while standing was rapidly overpowered by the electromyogram (EMG) signal resulting from the leg muscle activity involved in maintaining balance.
The accuracy of cardiovascular information obtained from weighing scale platforms is also influenced by measurement time. The number of beats obtained from heartbeat-related signals for signal averaging is a function of measurement time and heart rate. The Mayo Clinic cites that typical resting heart rates range from 60 to 100 beats per minute. Therefore, short signal acquisition periods may yield a low number of beats to average, which may cause measurement uncertainty, also known as the standard error in the mean (SEM). SEM is the standard deviation of the sample mean estimate of a population mean. Where, SE is the standard error in the samples N, which is related to the standard error or the population S.
$SES = \frac{S}{\sqrt{N}}$
For example, a five second signal acquisition period may yield a maximum of five to eight beats for ensemble averaging, while a 10 second signal acquisition could yield 10-16 beats. However, the number of beats available for averaging and SNR determination is usually reduced for the following factors; (1) truncation of the first and last ensemble beat in the recording by the algorithm, (2) triggering beats falsely missed by triggering algorithm, (3) cardiorespiratory variability, (4) excessive body motion corrupting the trigger and Foot IPG signal, and (5) loss of foot contact with the measurement electrodes.
Sources of noise can require multiple solutions for overall SNR improvements for the signal being averaged. Longer measurement times increase the number of beats lost to truncation, false missed triggering, and excessive motion. Longer measurement times also reduce variability from cardiorespiratory effects. Therefore, if shorter measurement times (e.g., less than 30 seconds) are desired for scale-based sensor platforms, sensing improvements need to tolerate body motion and loss of foot contact with the measurement electrodes.
The human cardiovascular system includes a heart with four chambers, separated by valves that return blood to the heart from the venous system into the right side of the heart, through the pulmonary circulation to oxygenate the blood, which then returns to the left side of the heart, where the oxygenated blood is pressurized by the left ventricles and is pumped into the arterial circulation, where blood is distributed to the organs and tissues to supply oxygen. The cardiovascular or circulatory system is designed to ensure maintenance of oxygen availability and is often the limiting factor for cell survival. The heart normally pumps five to six liters of blood every minute during rest and maximum cardiac output during exercise can increase up to seven-fold, by modulating heart rate and stroke volume. The factors that affect heart rate include the degree of autonomic innervation, fitness level, age and hormones. Factors affecting stroke volume include heart size, fitness level, contractility or pre-ejection period, ejection duration, preload or end-diastolic volume, afterload or systemic resistance. The cardiovascular system is constantly adapting to maintain a homeostasis (set point) that minimizes the work done by the heart to maintain cardiac output. As such, blood pressure is continually adjusting to minimize work demands during rest. Cardiovascular disease encompasses a variety of abnormalities in (or that affect) the cardiovascular system that degrade the efficiency of the system, which include but are not limited to chronically elevated blood pressure, elevated cholesterol levels, edema, endothelial dysfunction, arrhythmias, arterial stiffening, atherosclerosis, vascular wall thickening, stenosis, coronary artery disease, heart attack, stroke, renal dysfunction, enlarged heart, heart failure, diabetes, obesity and pulmonary disorders.
Each cardiac cycle results in a pulse of blood being delivered into the arterial tree. The heart completes cycles of atrial systole, delivering blood to the ventricles, followed by ventricular systole delivering blood into the lungs and the systemic arterial circulation, where the diastole cycle begins. In early diastole the ventricles relax and fill with blood, then in mid-diastole the atria and ventricles are relaxed and the ventricles continue to fill with blood. In late diastole, the sinoatrial node (the heart's pacemaker) depolarizes then contracting the atria, the ventricles are filled with more blood and the depolarization then reaches the atrioventricular node and enters the ventricular side beginning the systole phase. The ventricles contract and the blood is pumped from the ventricles to the arteries.
The ECG is the measurement of the heart's electrical activity and can be described in five phases. The P-wave represents atrial depolarization, the PR interval is the time between the P-wave and the start of the QRS complex. The QRS wave complex represents ventricular depolarization. The QRS complex is the strongest wave in the ECG and is frequently used as the de facto timing reference for the cardiovascular cycle. Atrial repolarization is masked by the QRS complex. The ST interval then follows which represents the period of zero potential between ventricular depolarization and repolarization. The cycle concludes with the T-wave representing ventricular repolarization.
The blood ejected into the arteries creates vascular movements due to the blood's momentum. The blood mass ejected by the heart first travels headward in the ascending aorta and travels around the aortic arch then travels down the descending aorta. The diameter of the aorta increases significantly during the systole phase due to the high compliance (low stiffness) of the aortic wall. Blood traveling in the descending aorta then bifurcates in the iliac branch which then transitions into a stiffer arterial region due to the muscular artery composition of the leg arteries. The blood pulsation continues down the leg and foot. All along the way, the arteries branch into arteries of smaller diameter until reaching the capillary beds where the pulsatile blood flow turns into steady blood flow, delivering oxygen to the tissues. The blood then returns to the venous system terminating in the vena cava, where blood returns to the right atrium of the heart for the subsequent cardiac cycle.
Surprisingly, high quality simultaneous recordings of the Leg IPG and Foot IPG are attainable in a practical manner (e.g., a user operating the device correctly simply by standing on the impedance body scale foot electrodes), and can be used to obtain reliable trigger fiducial timings from the Leg IPG signal. This acquisition can be far less sensitive to motion-induced noise from the Leg EMG that often compromises Leg ECG measurements. Furthermore, it has been discovered that interleaving the two Kelvin electrode pairs for a single foot, result in a design that is insensitive to foot placement within the boundaries of the overall electrode area. As such, the user is no longer constrained to comply with accurate foot placement on conventional single foot Kelvin arrangements, which are highly prone to introducing motion artifacts into the IPG signal, or result in a loss of contact if the foot is slightly misaligned. Interleaved designs begin when one or more electrode surfaces cross over a single imaginary boundary line separating an excitation and sensing electrode pair. The interleaving is configured to maintain uniform foot surface contact area on the excitation and sensing electrode pair, regardless of the positioning of the foot over the combined area of the electrode pair.
Various aspects of the present disclosure include a weighing scale platform (e.g., scale 110) of an area sufficient for an adult of average size to stand comfortably still and minimize postural swaying. The nominal scale length (same orientation as foot length) is 12 inches and the width is 12 inches. The width can be increased to be consistent with the feet at shoulder width or slightly broader (e.g., 14 to 18 inches, respectively).
FIG. 1 a is a flow chart depicting an example manner in which a user-specific physiologic meter or scale may be programmed in accordance with the present disclosure. This flow chart uses a computer processor circuit (or CPU) along with a memory circuit shown herein as user profile memory 146 a. The CPU operates in a low-power consumption mode, which may be in off mode or a low-power sleep mode, and at least one other higher power consumption mode of operation. As exemplary circuits for transitioning between such a low-power and higher power modes, the CPU can be integrated with presence and/or motion sense circuits, such as a PIR circuit and/or gyro PIR circuit. In a typical application, the PIR circuit provides a constant flow of data indicative of amounts of radiation sensed in a field of view directed by the PIR circuit. For instance, the PIR circuit can be installed behind a transparent upper surface of the platform (such as through the display screen of the platform apparatus) and installed at an angle so that the motion of the user, as the user approaches the platform apparatus, can be sensed. Radiation from the user, upon reaching a certain detectable level, wakes up the CPU which then transitions from the low-power mode, as depicted in block 140, to a regular mode of operation. In alternative embodiments, the low-power mode of operation is transitioned from a response to another remote/wireless input used as a presence to awaken the CPU. In other embodiments, motion can be sensed with a single integrated microphone or microphone array, to detect the sounds of a user approaching, or user motion can be detected by an accelerometer integrated in the scale.
Accordingly, from block 140, flow proceeds to block 142 where the user or other intrusion is sensed as data received at the platform apparatus. At block 144, the circuitry assesses whether the received data qualifies as requiring a wake up. If not, flow turns to block 140. If however, wake up is required, flow proceeds from block 144 to block 146 where the CPU assesses whether a possible previous user has approached the platform apparatus. This assessment is performed by the CPU accessing the user profile memory 146A and comparing data stored therein for one or more such previous users with criteria corresponding to the received data that caused the wake up. Such criteria might include, for example, the time of the day (early morning or late morning), the pace at which the user approached the platform apparatus as sensed by the motion detection circuitry, the height of the user as indicated by the motion sensing circuitry and/or a camera installed and integrated with the CPU, and/or more sophisticated bio-metric data provided by the user and/or automatically by the circuitry in the platform apparatus.
As discussed herein, such sophisticated circuitry can include one or more of the following user-specific attributes: foot length, type of foot arch, weight of user, and/or manner and speed at which the user steps onto the platform apparatus, or sounds made by the user's motion or by speech. As is also conventional, facial or body-feature recognition may also be used in connection with the camera and comparisons of images therefrom to images in the user profile memory.
From block 146, flow proceeds to block 148 where the CPU obtains and/or updates user corresponding data in the user profile memory. As a learning program is developed in the user profile memory, each access and use of the platform apparatus is used to expand on the data and profile for each such user. From block 148, flow proceeds to block 150 where a decision is made regarding whether the set of electrodes at the upper surface of the platform are ready for the user, such as may be based on the data obtained from the user profile memory. For example, delays may ensue from the user moving his or her feet about the upper surface of the platform apparatus, as may occur while certain data is being retrieved by the CPU (whether internally or from an external source such as a program or configuration data updates from the Internet cloud) or when the user has stepped over a certain area configured for providing display information back to the user. If the electrodes are not ready for the user, flow proceeds from block 150 to block 152 to accommodate this delay.
Once the CPU determines that the electrodes are ready for use while the user is standing on the platform surface, flow proceeds to block 160. Stabilization of the user on the platform surface may be ascertained by injecting current through the electrodes via the interleaved arrangement thereof. Where such current is returned via other electrodes for a particular foot and/or foot size, and is consistent for a relatively brief period of time, for example, a few seconds, the CPU can assume that the user is standing still and ready to use the electrodes and related circuitry.
At block 160, a decision is made that both the user and the platform apparatus are ready for measuring impedance and certain segments of the user's body, including at least one foot.
The remaining flow of FIG. 1 a includes the application and sensing of current through the electrodes for finding the optimal electrodes (162) and for performing impedance measurements (block 164). These measurements are continued until completed at block 166 and all such useful measurements are recorded and are logged in the user profile memory for this specific user, at block 168. At block 172, the CPU generates output data to provide feedback as to the completion of the measurements and, as can be indicated as a request via the user profile for this user, as an overall report on the progress for the user and relative to previous measurements made for this user has stored in the user profile memory. Such feedback may be shown on the display, through a speaker with co-located apertures in the platforms housing for audible reception by the user, and/or by vibration circuitry which, upon vibration under control of the CPU, the user can sense through one or both feet while standing on the scale. From this output at block 172, flow returns to the low power mode as indicated at block 174 with the return to the beginning of the flow at the block 140.
FIG. 2 shows an example of the insensitivity to foot placement 200 on scale electrode pairs 205/210 with multiple excitation paths 220 and sensing current paths 215, consistent with various aspects of the present disclosure. An aspect of the platform is that it has a thickness and strength to support a human adult of at least 200 pounds without fracturing, and another aspect of the device platform is comprised of at least six electrodes, where the first electrode pair 205 is solid and the second electrode pair 210 are interleaved. Another aspect is the first and second interleaved electrode pairs 205/210 are separated by a distance of at least 40+/−5 millimeters, where the nominal separation of less than 40 millimeters has been shown to degrade the single Foot IPG signal. Another key aspect is the electrode patterns are made from materials with low resistivity such as stainless steel, aluminum, hardened gold, ITO, index matched ITO (IMITO), carbon printed electrodes, conductive tapes, silver-impregnated carbon printed electrodes, conductive adhesives, and similar materials with resistivity lower than 300 ohms/sq. In the certain embodiments, the resistivity is below 150 ohms/sq. The electrodes are connected to the electronic circuitry in the scale by routing the electrodes around the edges of the scale to the surface below, or through at least one hole in the scale (e.g., a via hole).
Suitable electrode arrangements for dual Foot IPG measurements can be realized in other embodiments. In certain embodiments, the interleaved electrodes are patterned on the reverse side of a thin piece (e.g., less than 2 mm) of high-ion-exchange (HIE) glass, which is attached to a scale substrate and used in capacitive sensing mode. In certain embodiments, the interleaved electrodes are patterned onto a thin piece of paper or plastic which can be rolled up or folded for easy storage. In certain embodiments, the interleaved electrodes are integrated onto the surface of a tablet computer for portable IPG measurements. In certain embodiments, the interleaved electrodes are patterned onto a kapton substrate that is used as a flex circuit.
In certain embodiments, the scale area has a length of 10 inches with a width of eight inches for a miniature scale platform. Alternatively, the scale may be larger (up to 36 inches wide) for use in bariatric class scales. In certain embodiments, the scale platform with interleaved electrodes is incorporated into a floor tile that can be incorporated into a room such as a bathroom. In certain embodiments, the scale folds in half with a hinge for improved portability and storage. Alternatively, the scale platform is comprised of two separable halves, one half for the left foot and the other half for the right foot, for improved portability and storage. In certain embodiments for ambulatory measurements, the interleaved excitation and sensing electrode pairs are incorporated into a shoe insert for the detection of heart rate and a corresponding pulse arrival time (PAT). Alternatively, the interleaved excitation and sensing electrode pairs are incorporated into a pair of socks, to be worn for the detection of heart rate and a corresponding PAT.
In the present disclosure, the leg and foot impedance measurements can be simultaneously carried out using a multi-frequency approach, in which the leg and foot impedances are excited by currents modulated at two different frequencies, and the resulting voltages are selectively measured using a synchronous demodulator as shown in FIG. 3 a. This homodyning approach can be used to separate signals (in this case, the voltage drop due to the imposed current) with very high accuracy and selectivity.
This measurement configuration is based on a four-point configuration in order to minimize the impact of the contact resistance between the electrode and the foot, a practice well-known in the art of impedance measurement. In this configuration the current is injected from a set of two electrodes (the “injection” and “return” electrodes), and the voltage drop resulting from the passage of this current through the resistance is sensed by two separate electrodes (the “sense” electrodes), usually located in the path of the current. Since the sense electrodes are not carrying any current (by virtue of their connection to a high-impedance differential amplifier), the contact impedance does not significantly alter the sensed voltage.
In order to sense two distinct segments of the body (the legs and the foot), two separate current paths are defined by way of electrode positioning. Therefore two injection electrodes are used, each connected to a current source modulated at a different frequency. The injection electrode for leg impedance is located under the plantar region of the left foot, while the injection electrode for the Foot IPG is located under the heel of the right foot. Both current sources share the same return electrode located under the plantar region of the right foot. This is an illustrative example. Other configurations may be used.
The sensing electrodes can be localized so as to sense the corresponding segments. Leg IPG sensing electrodes are located under the heels of each foot, while the two foot sensing electrodes are located under the heel and plantar areas of the right foot. The inter-digitated nature of the right foot electrodes ensures a four-point contact for proper impedance measurement, irrespectively of the foot position, as already explained.
FIGS. 3 a-3 b show example block diagrams depicting the circuitry for sensing and measuring the cardiovascular time-varying IPG raw signals and steps to obtain a filtered IPG waveform, consistent with various aspects of the present disclosure. The example block diagrams shown in FIGS. 3 a-3 b are separated in to a leg impedance sub-circuit 300 and a foot impedance sub-circuit 305.
Excitation is provided by way of an excitation waveform circuit 310. The excitation waveform circuit 310 provides an excitation signal by way of a various types of frequency signals (as is shown in FIG. 3 a) or, more specifically, a square wave signal (as shown in FIG. 3 b). As is shown in FIG. 3 b, the square wave signal is a 5 V at a frequency between 15,625 Hz and 1 MHz is generated from a quartz oscillator (such as an ECS-100AC from ECS International, Inc.) divided down by a chain of toggle flip-flops (e.g. a CD4024 from Texas Instruments, Inc.), each dividing stage providing a frequency half of its input (i.e., 1 Mhz, 500 kHz, 250 kHz, 125 kHz, 62.5 kHz, 31.250 kHz and 15.625 kHz). This (square) wave is then AC-coupled, scaled down to the desired amplitude and fed to a voltage-controlled current source circuit 315. The generated current is passed through a decoupling capacitor (for safety) to the excitation electrode, and returned to ground through the return electrode (grounded-load configuration). Amplitudes of 1 and 4 mA peak-to-peak are typically used for Leg and Foot IPGs, respectively.
The voltage drop across the segment of interest (legs or foot) is sensed using an instrumentation differential amplifier (e.g., Analog Devices AD8421) 320. The sense electrodes on the scale are AC-coupled to the input of the differential amplifier 320 (configured for unity gain), and any residual DC offset is removed with a DC restoration circuit (as exemplified in Burr-Brown App Note Application Bulletin, SBOA003, 1991, or Burr-Brown/Texas Instruments INA118 datasheet).
The signal is then demodulated with a synchronous demodulator circuit 325. The demodulation is achieved in this example by multiplying the signal by 1 or −1 synchronously with the current excitation. Such alternating gain is provided by an operational amplifier and an analog switch (SPST), such as an ADG442 from Analog Devices). More specifically, the signal is connected to both positive and negative inputs through 10 kOhm resistors. The output is connected to the negative input with a 10 kOhm resistor as well, and the switch is connected between the ground and the positive input. When open, the gain of the stage is unity. When closed (positive input grounded), the stage acts as an inverting amplifier of the gain −1. Alternatively, other demodulators such as analog multipliers or mixers can be used.
Once demodulated, the signal is band-pass filtered (0.4-80 Hz) with a first-order band-pass filter circuit 330 before being amplified with a gain of 100 with a non-inverting amplifier circuit 335 (e.g., using an LT1058 operational amplifier from Linear Technologies). The amplified signal is further amplified by 10 and low-pass filtered (cut-off at 30 Hz) using a low-pass filter circuit 340 such as 2-pole Sallen-Key filter stage with gain. The signal is then ready for digitization and further processing. In certain embodiments, the amplified signal can be passed through an additional low-pass filter circuit 345 to determine body or foot impedance.
In certain embodiments, the generation of the excitation voltage signal, of appropriate frequency and amplitude, is carried out by a microcontroller, such as MSP430 (Texas Instruments, Inc.). The voltage waveform can be generated using the on-chip timers and digital input/outputs or pulse width modulation (PWM) peripherals, and scaled down to the appropriate voltage through fixed resistive dividers, active attenuators/amplifiers using on-chip or off-chip operational amplifiers, as well as programmable gain amplifiers or programmable resistors. Alternatively, the waveforms can be directly generated by on- or off-chip digital-to-analog converters (DACs).
In certain embodiments, the shape of the excitation is not square, but sinusoidal. Such configuration would reduce the requirements on bandwidth and slew rate for the current source and instrumentation amplifier. Harmonics, potentially leading to higher electromagnetic interference (EMI), would also be reduced. Such excitation may also reduce electronics noise on the circuit itself. Lastly, the lack of harmonics from sine wave excitation may provide a more flexible selection of frequencies in a multi-frequency impedance system, as excitation waveforms have fewer opportunities to interfere between each other. Due to the concentration of energy in the fundamental frequency, sine wave excitation could also be more power-efficient.
In certain embodiments, the shape of the excitation is not square, but trapezoidal. While not as optimal as a sinusoidal wave, trapezoidal waves (or square waves whose edges have been smoothed out by a limited bandwidth or slew rate) still provide an advantage in term of EMI and electronic noise due to the reduced harmonics.
To further reduce potential EMI, other strategies may be used, such as by dithering the square wave signal (i.e., introducing jitter in the edges following a fixed or random pattern) which leads to so-called spread spectrum signals, in which the energy is not localized at one specific frequency (or a set of harmonics), but rather distributed around a frequency (or a set of harmonics). An example of a spread-spectrum circuit suitable for Dual-IPG measurement is shown in FIG. 3 b. Because of the synchronous demodulation scheme, phase-to-phase variability introduced by spread-spectrum techniques will not affect the impedance measurement. Such a spread-spectrum signal can be generated by, but not limited to, specialized circuits (e.g., Maxim MAX31C80, SiTime SiT9001), or generic microcontrollers (see Application Report SLAA291, Texas Instruments, Inc.). These spread-spectrum techniques can be combined with clock dividers to generate lower frequencies as well.
As may be clear to one skilled in the art, these methods of simultaneous measurement of impedance in the leg and foot can be used for standard Body Impedance Analysis (BIA), aiming at extracting relative content of total water, free-water, fat mass and others. Impedance measurements for BIA are typically done at frequencies ranging from kilohertz up to several megahertz. The multi-frequency measurement methods described above can readily be used for such BIA, provided the circuit can be modified so that the DC component of the impedance is not canceled by the instrumentation amplifier (no DC restoration circuit used). The high-pass filter can be implemented after the instrumentation amplifier, enabling the measurement of the DC component used for BIA. This multi-frequency technique can also be combined with traditional sequential measurements often used for BIA, in which the impedance is measured at several frequencies sequentially. These measurements can be repeated in several body segments for segmental BIAs, using a switch matrix to drive the current into the desired body segments.
While FIG. 2 shows a circuit and electrode configuration suitable to measure two different segments (legs and one foot), this approach is not readily extendable to more segments due to the shared current return electrode (ground). To overcome this limitation, and in particular provide simultaneous measurements in both feet, the system can be augmented with analog switches to provide time-multiplexing of the impedance measurements in the different segments. This multiplexing can either be a one-time sequencing (each segment is measured once), or interleaved at a high-enough frequency that the signal can be simultaneously measured on each segment. The minimum multiplexing rate for proper reconstruction is twice the bandwidth of the measured signal, based on signal processing theory, which equals to about 100 Hz for the impedance signal considered here. The rate must also allow for the signal path to settle in between switching, usually limiting the maximum multiplexing rate. Referring to FIG. 14 a, one cycle might start the measurement of the leg impedance and left foot impedances (similarly to previously described, sharing a common return electrode), but then follow with a measurement of the right foot after reconfiguring the switches. Typical switch configurations for the various measurements are shown in the table below.


Switch #1	Switch #2	Switch #3	Switch #4
(Sw1)	(Sw2)	(Sw3)	(Sw4)

Legs	A	A or B	A or B	A
Right Foot	A	A or B	B	A
Left Foot	B	B	A or B	B

Since right and left feet are measured sequentially, one should note that a unique current source (at the same frequency) may be used to measure both, providing that the current source is not connected to the two feet simultaneously through the switches, in which case the current would be divided between two paths. One should also note that a fully-sequential measurement, using a single current source (at a single frequency) successively connected to the three different injection electrodes, could be used as well, with the proper switch configuration sequence (no split current path).
In certain embodiments, the measurement of various body segments, and in particular the legs, right foot and left foot, is achieved simultaneously due to as many floating current sources as segments to be measured, running at separate frequency so they can individually be demodulated. Such configuration is exemplified in FIG. 14 b for three segments (legs, right and left feet). Such configuration has the advantage to provide true simultaneous measurements without the added complexity of time-multiplexing/demultiplexing, and associated switching circuitry. An example of such floating current source can be found in Plickett, et al., Physiological Measurement, 32 (2011). Another approach to floating current sources is the use of transformer-coupled current sources (as depicted in FIG. 14 c). Using transformers to inject current into the electrodes enables the use of simpler, grounded-load current sources on the primary, while the electrodes are connected to the secondary. Turn ratio would typically be 1:1, and since frequencies of interest for impedance measurement are typically in the 10-1000 kHz (occasionally 1 kHz for BIA), relatively small transformers can be used. In order to limit the common mode voltage of the body, one of the electrodes in contact with the foot can be grounded.
While certain embodiments presented in the above specification have used current sources for excitation, it should be clear to a person skilled in the art that the excitation can also be performed by a voltage source, where the resulting injection current is monitored by a current sense circuit so that impedance can still be derived by the ratio of the sensed voltage (on the sense electrodes) over the sensed current (injected in the excitation electrodes).
It should be noted that broadband spectroscopy methods could also be used for measuring impedances at several frequencies. Such technique has the advantage of lower EMI and simultaneous measurement of impedances at numerous frequencies. These methods typically use a chirp signal, a noise signal or an impulse signal to excite the load (impedance) at many frequencies simultaneously, while sampling the resulting response at high frequency so as to allow the computation (usually in the frequency domain) of the impedance over the desired frequency range. Combined with time-multiplexing and current switching described above, multi-segment broadband spectroscopy can be readily achieved.
Various aspects of the present disclosure are directed toward robust timing extraction of the blood pressure pulse in the foot which is achieved by means of a two-step processing. In a first step, the usually high-SNR Leg IPG is used to derive a reference (trigger) timing for each heart pulse. In a second step, a specific timing in the lower-SNR Foot IPG is extracted by detecting its associated feature within a restricted window of time around the timing of the Leg IPG. Such guided detection leads to a naturally more robust detection of foot timings.
Consistent with yet further embodiments of the present disclosure, FIG. 3 c depicts an example block diagram of circuitry for operating core circuits and modules, including, for example, the operation of the CPU as in FIG. 1 a with the related more specific circuit blocks/modules in FIGS. 3A-3B. As shown in the center of FIG. 3 c, the main computer circuit 370 is shown with other previously-mentioned circuitry in a generalized manner without showing some of the detailed circuitry such as for amplification and current injection/sensing (372). The computer circuit 370 can be used as a control circuit with an internal memory circuit (or as integrated with the memory circuit for the user profile memory 146A of FIG. 1 a) for causing, processing and/or receiving sensed input signals as at block 372. As discussed, these sensed signals can be responsive to injection current and/or these signals can be sensed at least for initially locating positions of the foot or feet on the platform area, by less complex grid-based sense circuitry surrounding the platform area as is convention in capacitive touch-screen surfaces which, in certain embodiments, the platform area includes.
As noted, the memory circuit can be used not only for the user profile memory, but also as to provide configuration and/or program code and/or other data such as user-specific data from another authorized source such as from a user monitoring his/her logged data and/or profile from a remote desk-top. The remote device or desk-top can communicate with and access such data via a wireless communication circuit 376 via a wireless modem, router, ISDN channel, cellular systems, Bluetooth and/or other broadband pathway or private channel. For example, the wireless communication circuit 376 can provide an interface between an app on the user's cellular telephone/tablet (e.g., phablet, IPhone and/or IPad) and the platform apparatus, wherefrom the IPhone can be the output/input interface for the platform (scale) apparatus including, for example, an output display, speaker and/or microphone, and vibration circuitry; each of these I/O aspects and components being discussed herein in connection with other example embodiments.
A camera 378 and image encoder circuit 380 (with compression and related features) can also be incorporated as an option. As discussed above, the weighing scale components, as in block 382, are also optionally included in the housing which encloses and/or surrounds the platform apparatus.
For long-lasting battery life in the platform apparatus (batteries not shown), at least the CPU 370, the wireless communication circuit 376, and other current draining circuits are inactive unless and until activated in response to the intrusion/sense circuitry 388. As shown, one specific implementation employs a Conexant chip (e.g., CX93510) to assist in the low-power operation. This type of circuitry is specifically designed for motion sensors configured with a camera for visual verification and image and video monitoring applications (such as by supporting JPEG and MJPEG image compression and processing for both color and black and white images). When combined with an external CMOS sensor, the chip retrieves and stores compressed JPEG and audio data in an on-chip memory circuit (e.g., 256 KB/128 KB frame buffer) so as to alleviate the necessity of external memory. The chip uses a simple register set via the microprocessor interface and allows for wide flexibility in terms of compatible operation with another microprocessor.
In one specific embodiment, a method of using the platform with the plurality of electrodes are concurrently contacting a limb of the user, includes operating such to automatically obtain measurement signals from the plurality of electrodes. As noted above, these measurement signals might initially be through less complex (e.g., capacitive grid-type) sense circuitry. Before or while obtaining a plurality of measurement signals by operating the circuitry, the signal-sense circuitry 388 is used to sense wireless-signals indicative of the user approaching the platform and, in response, causing the CPU circuitry 370 to transition from a reduced power-consumption mode of operation and at least one higher power-consumption mode of operation. After the circuitry is operating in the higher power-consumption mode of operation, the CPU accesses the user-corresponding data stored in the memory circuit and thereafter causes a plurality of impedance-measurement signals to be obtained by using the plurality of electrodes while they are contacting the user via the platform; therefrom, the CPU generates signals corresponding to cardiovascular timings of the user.
This method can employ the signal-sense circuit as a passive infrared detector and with the CPU programmed (as a separate module) to evaluate whether radiation from the passive infrared detector is indicative of a human. For example, sensed levels of radiation that would correspond to a live being that has a size which is less than a person of a three-foot height, and/or not being sensed as moving for more than a couple seconds, can be assessed as being a non-human.
Accordingly, as the user is recognized as being human, the CPU is activated and begins to attempt the discernment process of which user might be approaching. This is performed by the CPU accessing the user-corresponding data stored in the memory circuit (the user profile memory). If the user is recognized based on parameters such as discussed above (e.g., time of morning, speed of approach, etc.), the CPU can also select one of a plurality of different types of user-discernible visual/audible/tactile information and for presenting the discerned user with visual/audible/tactile information that was retrieved from the memory as being specific to the user. For example, user-selected visual/audible data can be outputted for the user. Also, responsive to the motion detection indication, the camera can be activated to capture at least one image of the user while the user is approaching the platform (and/or while the user is on the platform to log confirmation of the same user with the measured impedance information). As shown in block 374 of FIG. 3 c, where a speaker is also integrated with the CPU, the user can simply command the platform apparatus to start the process and activation proceeds accordingly.
In another such method, the circuitry of FIG. 3 c is used with the plurality of electrodes being interleaved and engaging the user, as a combination weighing scale (via block 382) and a physiologic user-specific impedance-measurement device. By using the impedance-measurement signals and obtaining at least two impedance-measurement signals between one foot of the user and another location of the user, the interleaved electrodes assist the CPU in providing measurement results that indicate one or more of the following user-specific attributes as being indicative or common to the user: foot impedance, foot length, and type of arch, and wherein one or more of the user-specific attributes are accessed, by being read or stored, in the memory circuit and identified as being specific to the user. This information can be later retrieved by the user, medical and/or security personnel, according to a data-access authorization protocol as might be established upon initial configuration for the user.
FIG. 3 d shows an exemplary block diagram depicting the circuitry for interpreting signals received from electrodes (e.g., 372 of FIG. 3 c), and/or CPU 370 of FIG. 3 c. The input electrodes 375 transmit various electrical signals through the patient's body (depending on the desired biometric and physiological test to be conducted) and output electrodes 380 receive the modified signal as affected by a user's electrical impedance 385. Once received by the output electrodes 380, the modified signal is processed by processor circuitry 370 based on the selected test. Signal processing conducted by the processor circuitry 370 is discussed in more detail above (with regard to FIGS. 3 a-b). In certain embodiments of the present disclosure, the circuitry within 370 is provided by Texas Instruments part # AFE4300.
FIG. 4 shows an example block diagram depicting signal processing steps to obtain fiducial references from the individual Leg IPG “beats,” which are subsequently used to obtain fiducials in the Foot IPG, consistent with various aspects of the present disclosure. In the first step, as shown in block 400, the Leg IP and the Foot IPG are simultaneously measured. As shown at 405, the Leg IPG is low-pass filtered at 20 Hz with an 8-pole Butterworth filter, and inverted so that pulses have an upward peak. The location of the pulses is then determined by taking the derivative of this signal, integrating over a 100 ms moving window, zeroing the negative values, removing the large artifacts by zeroing values beyond 15× the median of the signal, zeroing the values below a threshold defined by the mean of the signal, and then searching for local maxima. Local maxima closer than a defined refractory period of 300 ms to the preceding ones are dismissed. The result is a time series of pulse reference timings.
As is shown in 410, the foot IPG is low-pass filtered at 25 Hz with an 8-pole Butterworth filter and inverted (so that pulses have an upward peak). Segments starting from the timings extracted (415) from the Leg IPG (reference timings) and extending to 80% of the previous pulse interval, but no longer than one second, are defined in the Foot IPG. This defines the time windows where the Foot IPG is expected to occur, avoiding misdetection outside of these windows. In each segment, the derivative of the signal is computed, and the point of maximum positive derivative (maximum acceleration) is extracted. The foot of the IPG signal is then computed using an intersecting tangent method, where the fiducial (420) is defined by the intersection between a first tangent to the IPG at the point of maximum positive derivative and a second tangent to the minimum of the IPG on the left of the maximum positive derivative within the segment.
The time series resulting from this two-step extraction is then used in conjunction with another signal to facilitate additional processing. In the present disclosure, these timings are used as reference timings to improve the SNR of BCG signals to subsequently extract intervals between a timing of the BCG (typically the I-wave) and the Foot IPG for the purpose of computing the PWV, as previously disclosed in U.S. 2013/0310700 (Wiard). In certain embodiments, the timings of the Leg IPG are used as reference timings to improve the SNR of BCG signals, and the foot IPG timings are used to extract intervals between timing fiducials of the improved BCG (typically the I-wave) and the Foot IPG for the purpose of computing the PTT and the (PWV).
In certain embodiments, the processing steps include an individual pulse SNR computation after individual timings have been extracted, either in Leg IPG or Foot IPG. Following the computation of the SNRs, pulses with a SNR below a threshold value are eliminated from the time series, in order to prevent propagating noise in subsequent processing steps. The individual SNRs may be computed in a variety of methods known to a person skilled in the art. For instance, an estimated pulse can be computed by ensemble averaging segments of signal around the pulse reference timing. The noise associated with each pulse is defined as the difference between the pulse and the estimated pulse. The SNR is then the ratio of the root-mean-square (RMS) value of the estimated pulse over the RMS value of the noise for that pulse.
In certain embodiments, the time interval between the Leg IPG pulses, (as detected by the above-mentioned methods), and the Foot IPG pulses, also detected by the above-mentioned methods, is extracted. The Leg IPG measuring a pulse occurring earlier in the legs compared to the pulse from the Foot IPG, the interval between these two is related to the propagation speed in the lower body, i.e., the peripheral vasculature. This provides complementary information to the interval extracted between the BCG and the Foot IPG for instance, and can be used to decouple central versus peripheral vascular properties. It is also complementary to information derived from timings between the BCG and the Leg ICG.
FIG. 5 shows an example flowchart depicting signal processing to segment individual Foot IPG “beats” to produce an averaged IPG waveform of improved SNR, which is subsequently used to determine the fiducial of the averaged Foot IPG, consistent with various aspects of the present disclosure. Similar to the method shown in FIG. 4, the Leg IP and the Foot IPG are simultaneously measured (500), the Leg IPG is low-pass filtered (505), the foot IPG is low-pass filtered (510), and segments starting from the timings extracted (515) from the Leg IPG (reference timings). The segments of the Foot IPG extracted based on the Leg IPG timings are ensemble-averaged (520) to produce a higher SNR Foot IPG pulse. From this ensemble-averaged signal, the start of the pulse is extracted using the same intersecting tangent approach as described earlier. This approach enables the extraction of accurate timings in the Foot IPG even if the impedance signal is dominated by noise, as shown in FIG. 7 b. These timings can then be used together with timings extracted from the BCG for the purpose of computing the PTT and (PWV). Timings derived from ensemble-averaged waveforms and individual waveforms can also be both extracted, for the purpose of comparison, averaging and error-detection.
Specific timings can be extracted from the IPG pulses (from either leg or foot) are related (but not limited) to the peak of the pulse, to the minimum preceding the peak, or to the maximum second derivative (maximum rate of acceleration) preceding the point of maximum derivative. An IPG pulse and the extraction of a fiducial (525) in the IPG can also be performed by several other signal processing methods, including (but not limited to) template matching, cross-correlation, wavelet-decomposition, or short window Fourier transform.
FIG. 6 a shows examples of the Leg IPG signal with fiducials (plot 600); the segmented Leg IPG into beats (plot 605); and the ensemble-averaged Leg IPG beat with fiducials and calculated SNR (plot 610), for an exemplary high-quality recording, consistent with various aspects of the present disclosure. Additionally, FIG. 6 b shows examples of the Foot IPG signal with fiducials derived from the Leg IPG fiducials (plot 600); the segmented Foot IPG into beats (plot 605); and the ensemble-averaged Foot IPG beat with fiducials and calculated SNR (plot 610), for an exemplary high-quality recording, consistent with various aspects of the present disclosure.
FIG. 7 a shows examples of the Leg IPG signal with fiducials (plot 700); the segmented Leg IPG into beats (plot 705); and the ensemble averaged Leg IPG beat with fiducials and calculated SNR (plot 710), for an exemplary low-quality recording, consistent with various aspects of the present disclosure. FIG. 7 b shows examples of the Foot IPG signal with fiducials derived from the Leg IPG fiducials (plot 700); the segmented Foot IPG into beats (plot 705); and the ensemble-averaged Foot IPG beat with fiducials and calculated SNR (plot 710), for an exemplary low-quality recording, consistent with various aspects of the present disclosure.
FIG. 8 shows an example correlation plot 800 for the reliability in obtaining the low SNR Foot IPG pulse for a 30-second recording, using the first impedance signal as the trigger pulse, from a study including 61 test subjects with various heart rates, consistent with various aspects of the present disclosure.
In certain embodiments, a dual-Foot IPG is measured, allowing the detection of blood pressure pulses in both feet. Such information can be used for diagnostic of peripheral arterial diseases (PAD) by comparing the relative PATs in both feet to look for asymmetries. It can also be used to increase the robustness of the measurement by allowing one foot to have poor contact with electrodes (or no contact at all). SNR measurements can be used to assess the quality of the signal in each foot, and to select the best one for downstream analysis. Timings extracted from each foot can be compared and set to flag potentially inaccurate PWV measurements due to arterial peripheral disease, in the event these timings are different by more than a defined threshold. Alternatively, timings from both feet can be pooled to increase the overall SNR if their difference is below a defined threshold.
In certain embodiments, the disclosure is used to measure a PWV, where the IPG is augmented by the addition of BCG sensing into the weighing scale to determine characteristic fiducials between the BCG and Leg IPG trigger, or the BCG and Foot IPG. The BCG sensors are comprised typically of the same strain gage set used to determine the bodyweight of the user. The load cells are typically wired into a bridge configuration to create a sensitive resistance change with small displacements due to the ejection of the blood into the aorta, where the circulatory or cardiovascular force produce movements within the body on the nominal order of 1-3 Newtons. BCG forces can be greater than or less than the nominal range in cases such as high or low cardiac output.
FIGS. 9 a-b show example configurations to obtain the PTT, using the first IPG as the triggering pulse for the Foot IPG and BCG, consistent with various aspects of the present disclosure. The I-wave of the BCG 900 as illustrated normally depicts the headward force due to cardiac ejection of blood into the ascending aorta which can be used as a timing fiducial indicative of the pressure pulse initiation of the user's proximal aorta relative to the user's heart. The J-wave is also indicative of timings in the systole phase and also incorporates information related to the strength of cardiac ejection and the ejection duration. The K-Wave also provides systolic and vascular information of the user's aorta. The characteristic timings of these and other BCG waves can be used as fiducials that can be related to fiducials of the IPG signals of the present disclosure. FIG. 10 shows nomenclature and relationships of various cardiovascular timings, consistent with various aspects of the present disclosure.
FIG. 11 shows an example graph 1100 of PTT correlations for two detection methods (white dots) Foot IPG only, and (black dots) Dual-IPG method, consistent with various aspects of the present disclosure.
FIG. 12 shows an example graph 1200 of PWV obtained from the present disclosure compared to the ages of 61 human test subjects, consistent with various aspects of the present disclosure.
FIG. 13 shows another example of a scale 1300 with interleaved foot electrodes 1305 to inject and sense current from one foot to another foot, and within one foot, consistent with various aspects of the present disclosure.
FIG. 14 a-c shows various examples of a scale 1400 with interleaved foot electrodes 1405 to inject and sense current from one foot to another foot, and measure Foot IPG signals in both feet, consistent with various aspects of the present disclosure.
FIGS. 15 a, 15 b, 15 c and 15 d show an example breakdown of a scale with interleaved foot electrodes to inject and sense current from one foot to another foot, and within one foot, consistent with various aspects of the present disclosure.
FIG. 16 shows an example block diagram of circuit-based building blocks, consistent with various aspects of the present disclosure. The various circuit-based building blocks shown in FIG. 16 can be implemented in connection with the various aspects discussed herein. In the example shown, the block diagram includes foot electrodes 1600 that can collect the IPG signals. Further, the block diagram includes strain gauges 1605, and an LED/photosensor 1610. The foot electrodes 1600 is configured with a leg impedance measurement circuit 1615, a foot impedance measurement circuit 1620, and an optional second foot impedance measurement circuit 1625. The leg impedance measurement circuit 1615, the foot impedance measurement circuit 1620, and the optional second foot impedance measurement circuit 1625 report the measurements collected to a processor circuit 1645.
The processor circuit 1645 also collects data from a weight measurement circuit 1630 and an option balance measurement circuit 1635 that are configured with the strain gauges 1605. Further, an optional photoplethysmogram (PPG) measurement circuit 1640, which collects data from the LED/photosensor 1610, can also provide data to the processor circuit 1645.
The processor circuit 1645 is powered via a power circuit 1650. Further, the processor circuit 1645 also collects user input data from a user interface 1655 that can include a touch screen and/or buttons. The data collected/measured by the processor circuit 1645 is shown to the user via a display 1660. Additionally, the data collected/measured by the processor circuit 1645 can be stored in a memory circuit 1680. Further, the processor circuit 1645 can optionally control a haptic feedback circuit 1665, a speaker or buzzer 1670, a wired/wireless interface 1675, and an auxiliary sensor 1685.
FIG. 17 shows an example flow diagram, consistent with various aspects of the present disclosure. As shown in block 1700, a PWV length is entered. As is shown in block 1705, a user's weight, balance, leg, and foot impedance are measured (as is consistent with various aspects of the present disclosure). As is shown at block 1710, the integrity of signals is checked (e.g., signal to noise ratio). If the signal integrity check is not met, the user's weight, balance, leg, and foot impedance are measured again (block 1705), if the signals integrity check is met, the leg impedance pulse timings are extracted (as is shown at block 1715). As is shown at block 1720, foot impedance and pulse timings are then extracted, and as is shown at block 1725, BCG timings are extracted. As is shown at block 1730, a timings quality check is performed. If the timings quality check is not validated, the user's weight, balance, leg and foot impedance are again measured (block 1705). If the timings quality check is validated, the PWV is calculated (as is shown at block 1735). Finally, as is shown at block 1740, the PWV is then displayed to the user.
FIG. 18 shows an example scale 1800 communicatively coupled to a wireless device, consistent with various aspects of the present disclosure. As described herein, a display 1805 displays the various aspects measured by the scale 1800. The scale can also wirelessly broadcast the measurements to a wireless device 1810.
FIGS. 19 a-c show example impedance as measured through different parts of the foot based on the foot position, consistent with various aspects of the present disclosure. For instance, example impedance measurement configurations may be implemented using a dynamic electrode configuration for measurement of foot impedance and related timings, consistent with various aspects of the present disclosure. Dynamic electrode configuration may be implemented using independently-configurable electrodes to optimize the impedance measurement. As shown in FIG. 19 a, interleaved electrodes 1900 are connected to an impedance processor circuit 1905 to determine foot length, foot position, and/or foot impedance. As is shown in FIG. 19 b, an impedance measurement is determined regardless of foot position 1910 based on measurement of the placement of the foot across the electrodes 1900. This is based in part in the electrodes 1900 that are engaged (blackened) and in contact with the foot (based on the foot position 1910), which is shown in FIG. 19 c.
More specifically regarding FIG. 19 a, configuration can include connection/de-connection of the individual electrodes 1900 to the impedance processor circuit 1905, their configuration as current-carrying electrodes (injection or return), sense electrodes (positive or negative), or both. The configuration can either be preset based on user information, or updated at each measurement (dynamic reconfiguration) to optimize a given parameter (impedance SNR, measurement location). The system may for instance algorithmically determine which electrodes under the foot to use in order to obtain the highest SNR in the pulse impedance signal. Such optimization algorithm may include iteratively switching configurations and measuring the resulting impedance, then selecting the best suited configuration. Alternatively, the system may first, through a sequential impedance measurement between each individual electrode 1900 and another electrode in contact with the body (such as an electrode in electrode pair 205 on the other foot), determine which electrodes are in contact with the foot. By determining the two most apart electrodes, the foot size is determined. Heel location can also be determined in this manner, as can other characteristics such as foot arch type. These parameters can then be used to determine programmatically (in an automated manner by CPU/logic circuitry) which electrodes should be selected for current injection and return (as well as sensing if a Kelvin connection issued) in order to obtain the best foot IPG.
In various embodiments involving the dynamically reconfigurable electrode array 1900/1905, an electrode array set is selected to measure the same portion (or segment) of the foot, irrespective of the foot location on the array. FIG. 19 b illustrates the case of several foot positions on a static array (a fixed set of electrodes are used for measurement at the heel and plantar/toe areas, with a fixed gap of an inactive electrode or insulating material between them). Depending on the position of the foot, the active electrodes are contacting the foot at different locations, thereby sensing a different volume (or segment) of the foot. If the IPG is used by itself (e.g., for heart measurement), such discrepancies may be non-consequential. However, if timings derived from the IPG are referred to other timings (e.g., R-wave from the ECG, or specific timing in the BCG), such as for the calculation of a PTT or PWV, the small shifts in IPG timings due to the sensing of slightly different volumes in the foot (e.g., if the foot is not always placed at the same position on the electrodes) can introduce an error in the calculation of the interval. Such location variations can readily occur in the day-to-day use of the scale. With respect to FIG. 19 b for instance, the timing of the peak of the IPG from the foot placement on the right (sensing the toe/plantar region) would be later than from the foot placement on the left, which senses more of the heel volume (the pulse reaches first the heel, then the plantar region). Factors influencing the magnitude of these discrepancies include foot shape (flat or not) and foot length.
Various embodiments address challenges relating to foot placement. FIG. 19 c shows an example embodiment involving dynamic reconfiguration of the electrodes to reduce such foot placement-induced variations. As an example, by sensing the location of the heel first (as described above), it is possible to activate only a subset of electrodes under the heel, and another subset of electrodes separated by a fixed distance (1900). The other electrodes (e.g., unused electrodes) are left disconnected. The sensed volume will therefore always be the same, producing consistent timings. The electrode configuration leading to the most consistent results may also be informed by the foot impedance, foot length, the type of arch (all of which can be measured by the electrode array as shown above), but also by the user ID (foot information can be stored for each user, then looked up based on automatic user recognition or manual selection (e.g., in a look-up-table stored for each user in a memory circuit accessible by the CPU circuit in the scale).
Accordingly, in certain embodiments, the impedance-measurement apparatus measures impedance using a plurality of electrodes contacting one foot and with at least one other electrode (typically many) at a location distal from the foot. The plurality of electrodes (contacting the one foot) is arranged on the platform and in a pattern configured to inject current signals and sense signals in response thereto, for the same segment of the foot so that the timing of the pulse-based measurements does not vary simply because the user placed the one foot at a slightly different position on the platform or scale. Thus, in FIG. 19 a, the foot-to-electrode locations for the heel are different locations than that shown in FIGS. 19 b and 19 c. As this different foot placement might occur from day to day for the user, the timing and related impedance measurements should be for the same (internal) segment of the foot. By having the computer processor circuit inject current and sense responsive signals to first locate the foot on the electrodes (e.g., sensing where positions of the foot's heel plantar regions and/or toes), the pattern of foot-to-electrode locations permits the foot to move laterally, horizontally and both laterally and horizontally via the different electrode locations, while collecting impedance measurements relative to the same segment of the foot.
The BCG/IPG system can be used to determine the PTT of the user, by identification of the average I-Wave or derivative timing near the I-Wave from a plurality of BCG heartbeat signals obtained simultaneously with the Dual-IPG measurements of the present disclosure to determine the relative PTT along an arterial segment between the ascending aortic arch and distal pulse timing of the user's lower extremity. In certain embodiments, the BCG/IPG system is used to determine the PWV of the user, by identification of the characteristic length representing the length of the user's arteries, and by identification of the average I-Wave or derivative timing near the I-Wave from a plurality of BCG heartbeat signals obtained simultaneously with the Dual-IPG measurements of the present disclosure to determine the relative PTT along an arterial segment between the ascending aortic arch and distal pulse timing of the user's lower extremity. The system of the present disclosure and alternate embodiments may be suitable for determining the arterial stiffness (or arterial compliance) and/or cardiovascular risk of the user regardless of the position of the user's feet within the bounds of the interleaved electrodes. In certain embodiments, the weighing scale system incorporated the use of strain gage load cells and six or eight electrodes to measure a plurality of signals including: bodyweight, BCG, body mass index, fat percentage, muscle mass percentage, and body water percentage, heart rate, heart rate variability, PTT, and PWV measured simultaneously or synchronously when the user stands on the scale to provide a comprehensive analysis of the health and wellness of the user.
In other certain embodiments, the PTT and PWV are computed using timings from the Leg IPG or Foot IPG for arrival times, and using timings from a sensor located on the upper body (as opposed to the scale measuring the BCG) to detect the start of the pulse. Such sensor may include an impedance sensor for impedance cardiography, a hand-to-hand impedance sensor, a photoplethysmogram on the chest, neck, head, arms or hands, or an accelerometer on the chest (seismocardiograph) or head.
Communication of the biometric information is another aspect of the present disclosure. The biometric results from the user are then stored in the memory on the scale and displayed to the user via a display on the scale, audible communication from the scale, and/or the data is communicated to a peripheral device such as a computer, smart phone, tablet computing device. The communication occurs directly to the peripheral device with a wired connection, or can be sent to the peripheral device through wireless communication protocols such as Bluetooth or WiFi. Computations such as signal analyses described therein may be carried out locally on the scale, in a smartphone or computer, or in a remote processor (cloud computing).
Other aspects of the present disclosure are directed toward apparatuses or methods that include the use of at least two electrodes that contacts feet of a user. Further, circuitry is provided to determine a pulse arrival time at the foot based on the recording of two or more impedance signals from the set of electrodes. Additionally, a second set of circuitry is provided to extract a first pulse arrival time from a first impedance signal and use the first pulse arrival time as a timing reference to extract and process a second pulse arrival time in a second impedance signal.
One or more or the above aspects of the described embodiments may be used in combination with the embodiments (or aspects thereof) as described in connection with the following patent documents:
U.S. patent application Ser. No. 14/500,111 filed on Sep. 29, 2014, entitled “Multifunction Scale with Large-Area Display” and claiming benefit of U.S. Provisional Application Ser. No. 62/027,724, filed on Jul. 22, 2014, entitled “Multifunction Scale with Large-Area Display”;
U.S. patent application Ser. No. 12/579,264 filed on Oct. 14, 2009 (U.S. Pat. No. 8,870,780), entitled “Systems and Methods for Monitoring Heart Functions” and claiming priority to U.S. Provisional Application Ser. No. 61/105,696, filed on Oct. 15, 2008, entitled “Systems and Methods for Monitoring Heart Functions”; and
U.S. patent application Ser. No. 13/982,185, filed on Jul. 26, 2013 (U.S. Pat. No. 9,011,346) entitled “Systems and Methods for Monitoring the Circulatory System” and claiming priority to U.S. Provisional Application Ser. No. 61/436,740, filed on Jan. 27, 2011, entitled “Systems and Methods for Assessment of Arterial Stiffness and Management of Hypertension” and to U.S. Provisional Application Ser. No. 61/475,887, filed on Apr. 15, 2011, and entitled “Systems and Methods for Monitoring the Circulatory System”.
For example, with reference to U.S. patent application Ser. No. 14/500,111, a weighing scale is described and illustrated by FIG. 1A. The weighing scale 100 includes a support structure 110 having a platform region 115 with sensor circuitry therein (e.g., electrodes). The platform region 115 engages a user with the sensor circuitry while the user stands on the platform region 115 and use the sensor circuitry to collect physiological data from the user. While the user stands on the scale 100, the display 120 displays data through and throughout the entire platform region. The scale 100 also includes circuitry 130 including user-targeted circuitry and a communication driver. The user-targeted circuitry receives the physiological data from the sensor circuitry and determines physiological parameters of the user, including a user-weight metric, while the user stands on and engages the sensor circuitry of the platform region 115. The communication driver provides information from the user-targeted circuitry to the display 120 for viewing by the user through the platform region 115. In some embodiments the circuitry 130 may also include a data-access circuit that provides access to user-specific data including stored physiological parameters of the user in response to or developed by the user-targeted circuitry and to store physiological parameters of the user determined by the user-targeted circuitry (in other embodiments, the data-access circuit may be external to the scale 100, and may be accessed by the circuitry 130 over a communication network). One or more of the scales illustrated by FIGS. 1 and 2 of the present disclosure can be combined with one or more of the scales or aspects thereof of the Application 2014/500,111, such as those illustrated by FIG. 1A and FIG. 3A-3B. The teachings of this reference is herein fully incorporated specifically and generally.
With reference to U.S. patent application Ser. No. 12/579,264, a weighing scale is described and illustrated by FIGS. 1A-1B. FIG. 1A shows a block diagram of a system and approach for determining cardiac function/characteristics of a patient, consistent with an example embodiment of the present invention. User 102 positions themselves on scale 100. Scale 100 includes a force/weight sensor 106. This sensor 106 is configured to detect weight variations that are converted to an electrical signal that is sent to processing arrangement 108, and can be further used to provide the weight of the user, such as that provided by a traditional scale. Secondary input(s) 104 provide information in addition to strict weight sensing. These inputs can include, for example, signals provided by heart-beat sensors, foot-to-foot impedance cardiogram sensors, user movement sensors and the like, which may further be incorporated into the system. In some implementations, impedance plethysmography or photo-plethysmography sensors, can be used to improve signal processing. As illustrated by FIG. 1B, A scale-type BCG sensor device 130 includes an ECG-type hand-held sensor 132 that detects ECG characteristics that are used in connection with BCG characteristics detected at the scale-type device 130. An output from the BCG sensor device 130 is passed to a processor 140 that processes the output and detected ECG and BCG characteristics therein, to determine a heart-based condition of a user 122. In various implementations, one or more additional sensors, represented at block 150, are also coupled to the processor 140, which uses the inputs as part of the determination of the heart-based condition (e.g., such as a vibration sensor that is used to remove noise in one or both of a BCG- and ECG-based signals). One or more of the scales illustrated by FIGS. 1 and 2 of the present disclosure can be combined with one or more of the scales or aspects thereof of the application Ser. No. 12/579,264, such as those illustrated by FIG. 1A and FIG. 1B. The teachings of this reference is herein fully incorporated specifically and generally.
With regard to U.S. patent application Ser. No. 13/982,185, a weighing scale is described and illustrated by FIGS. 1A-1B. The weighing scale acquires BCG (ballistocardiogram) data from a user. The system includes a BCG capture device, a secondary sensor and a processor circuit. The BCG capture device includes a heart and vascular characteristic sensor that captures, from the user, a BCG signal indicative of at least one of physical movement and mechanical output of the user's proximal aorta. The secondary sensor detects the blood pressure pulse travel time at the user's feet, to determine a characteristic of the user's distal arterial stiffness, and then provides an output characterizing the detected indication. The processor circuit uses the sensor outputs to determine best estimates of the user's overall circulatory function and to generate an output result indicative of a user's arterial condition. In some aspects, a scale-type BCG sensor device includes an ECG-type hand-held sensor that detects ECG characteristics that are used in connection with BCG characteristics detected at the scale-type device. An output from the BCG sensor device is passed to a processor that processes the output and detected ECG and BCG characteristics therein, to determine a heart-based condition of a user. One or more of the scales illustrated by FIGS. 1 and 2 of the present disclosure can be combined with one or more of the scales or aspects thereof of the application Ser. No. 13/982,185, such as those illustrated by FIG. 1A and FIG. 1B. The teachings of this reference is herein fully incorporated specifically and generally.
Reference may also be made to published patent documents U.S. Patent Publication No. 2010/0094147 and U.S. Patent Publication No. 2013/0310700, which are, together with the references cited therein, herein fully incorporated by reference for the purposes of sensors and sensing technology. The aspects discussed therein may be implemented in connection with one or more of embodiments and implementations of the present disclosure (as well as with those shown in the figures). In view of the description herein, those skilled in the art will recognize that many changes may be made thereto without departing from the spirit and scope of the present disclosure.
As illustrated herein, various circuit-based building blocks and/or modules may be implemented to carry out one or more of the operations and activities described herein shown in the block-diagram-type figures. In such contexts, these building blocks and/or modules represent circuits that carry out one or more of these or related operations/activities. For example, in certain of the embodiments discussed above (such as the pulse circuitry modularized as shown in FIGS. 3 a-b), one or more blocks/modules are discrete logic circuits or programmable logic circuits configured and arranged for implementing these operations/activities, as in the circuit blocks/modules shown. In certain embodiments, the programmable circuit is one or more computer circuits programmed to execute a set (or sets) of instructions (and/or configuration data). The instructions (and/or configuration data) can be in the form of firmware or software stored in and accessible from a memory (circuit). As an example, first and second modules/blocks include a combination of a CPU hardware-based circuit and a set of instructions in the form of firmware, where the first module/block includes a first CPU hardware circuit with one set of instructions and the second module/block includes a second CPU hardware circuit with another set of instructions.
Accordingly, aspects of the present disclosure are directed to, inter alia, the following apparatuses, systems, and/or methods:

- Measuring a pulse arrival time at the foot based on the recording of two or more simultaneous impedance signals from a set of electrodes in contact with the feet, in which:
  - at least a first impedance signal is measured from one foot to another body region (e.g., the other foot),
  - at least a second impedance signal is measured within one foot, and
  - a first pulse arrival time is extracted from a first impedance signal, and is used as timing reference to extract and process a second pulse arrival time in a second impedance signal.
- The first pulse arrival time can be used as a timing reference for processing a third signal containing synchronous information (e.g., BCG or impedance cardiogram).
- The second pulse arrival time can be used as a timing reference for processing a third signal containing synchronous information (e.g., BCG or impedance cardiogram).
- A PTT can be measured by taking the difference between the pulse arrival time at the foot and a timing derived from a simultaneously-measured signal (e.g., BCG or impedance cardiogram).
- A PTT can be measured by taking the difference between the second pulse arrival time and the first pulse arrival time.
- A third impedance signal can be measured in the second foot, and, a first pulse arrival time can be extracted from a first impedance signal, and is used as timing reference to extract and process a third pulse arrival time in a third impedance signal.
  - A computation of a PWV from the first and either of the second or third timings can be flagged as potentially inaccurate based on a difference between the second and third pulse arrival times higher than a defined threshold.
  - A computation of a PWV can be performed from the first timing and the pooled timings extracted from the second and third impedance signals, if the difference between the second and third pulse arrival times is lower than a defined threshold.
- A sensor for measuring the electrical impedance of a foot, using at least one set of two electrodes for excitation and sensing respectively, whereas electrode contacts are interleaved over an area so as to always provide a similar area of contact with the foot for each electrode irrespectively of the foot position within the limits of the overall electrode area.
  - The first set of two electrodes can be in contact with the back of the foot, and a second set of two electrodes can provide contact with the front of the foot, and, the two sets of electrodes can be connected in a Kelvin configuration for impedance measurement.
  - The spacing between the first set of electrode contacting the back of the foot and the second set of electrodes contacting the front of the foot can be larger than 20 mm.
  - The set of electrodes can include two inter-digitated electrodes.
  - The set of electrodes can include of an array contacts, whereas every other contact is connected the same electrode.

Based upon the above discussion and illustrations, those skilled in the art will readily recognize that various modifications and changes may be made to the present disclosure without strictly following the exemplary embodiments and applications illustrated and described herein. For example, the input terminals as shown and discussed may be replaced with terminals of different arrangements, and different types and numbers of input configurations (e.g., involving different types of input circuits and related connectivity). Such modifications do not depart from the true spirit and scope of the present disclosure.

Claims

What is claimed is:

1. A weighing scale comprising:

a CPU and a memory circuit with user-corresponding data stored in the memory circuit, and a platform over which a plurality of electrodes are interleaved and configured and arranged for engaging a user while the user stands on the platform;

circuitry configured and arranged for obtaining a plurality of measurement signals from the plurality of electrodes, the circuitry having a first power-consumption mode of operation and a second power-consumption mode of operation;

the CPU, the memory circuit and the plurality of electrodes being configured and arranged to:

using a signal-sense circuit to sense wireless-signals indicative of the user approaching the platform and, in response, causing the circuitry to transition from the first power-consumption mode of operation to the second power-consumption mode of operation;

after the circuitry is operating in the second power-consumption mode of operation, causing the CPU to access the user-corresponding data stored in the memory circuit and thereafter cause a plurality of impedance-measurement signals to be obtained by using the plurality of electrodes while they are contacting the user via the platform and, therefrom, generating signals corresponding to cardiovascular timings of the user.

2. A weighing scale constructed and arranged consistent with one or more embodiments disclosed herein.

3. A method directed to a weighing scale constructed and arranged consistent with one or more embodiments disclosed herein.