Patent Application
20230346239
The disclosed technology relates to a device, system and method for performing at least one impedance measurement on a biological subject.
The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.
WO2007/002991 describes an apparatus for performing impedance measurements on a subject. The apparatus includes a first processing system for determining an impedance measurement procedure and determining instructions corresponding to the measurement procedure. A second processing system is provided for receiving the instructions, using the instructions to generate control signals, with the control signals being used to apply one or more signals to the subject. The second processing system then receives first data indicative of the one or more signals applied to the subject, second data indicative of one or more signals measured across the subject and performs at least preliminary processing of the first and second data to thereby allow impedance values to be determined.
In one broad form, the a system is provided for performing at least one impedance measurement on a biological subject, the system including: a measuring device having: a first housing including spaced pairs of foot drive and sense electrodes provided in electrical contact with feet of the subject in use; a second housing including spaced pairs of hand drive and sense electrodes provided in electrical contact with hands of the subject in use; at least one signal generator electrically connected to at least one of the drive electrodes to apply a drive signal to the subject; at least one sensor electrically connected to at least one of the sense electrodes to measure a response signal in the subject; a measuring device processor that at least in part: controls the at least one signal generator; receives an indication of a measured response signal from the at least one sensor; and, generates measurement data indicative of at least one measured impedance value; and, a client device in communication with the measuring device, the client device being adapted to receive measurement data allowing the client device to display an indicator associated a result of the impedance measurement.
In one embodiment the drive and sense electrodes are spaced apart plate electrodes.
In one embodiment the first housing includes a raised lip extending at least partially around each pair of foot drive and sense electrodes to thereby guide positioning of a subject's foot relative to the foot drive and sense electrodes in use.
In one embodiment the raised lip is configured to engage at least a heel of the subject.
In one embodiment the first housing includes feet that support the first housing spaced from a surface.
In one embodiment the feet engage load cells mounted within the first housing, the measuring device processor being adapted to determine a weight of a subject standing on the first housing.
In one embodiment the second housing has a curved upper surface.
In one embodiment the second housing includes a display configured to display at least one of: a weight; a body status indicator; a measurement status indicator; and, an error indicator.
In one embodiment the second housing includes a raised portion between each pair of hand drive and sense electrodes, the raised portion defining thumb recesses to thereby guide positioning of a subject's hands relative to each pair of hand drive and sense electrodes in use.
In one embodiment raised portion includes two ridges, each ridge extending towards a respective hand sense electrodes, and being adapted to be positioned between a subject's thumb and forefinger.
In one embodiment the system includes a stand including: a base that supports the first housing; a platform that supports the second housing; and, a leg coupled to the base and platform to support the platform relative to the base.
In one embodiment the leg includes a trough that receives a lead extending between the first and second housings.
In one embodiment stand includes at least one of: a support that supports a client device; and, a handle.
In one embodiment the base includes wheels.
In one embodiment the system includes: four signal generators, each signal generator being electrically connected to a respective drive electrode; and, four sensors, each sensor being electrically connected to at least one of the sense electrodes to measure a response signal in the subject and wherein the measuring device processor selectively controls the four signal generators and four sensors to perform a sequence of impedance measurements, the impedance measurements including: segmental impedance measurements; and, whole of body impedance measurements.
In one embodiment the measuring device processor communicates with the client device to at least one of: determine the at least one measurement to be performed; provide a measurement indication to the client device, the measurement indication being indicative of a measurement being performed; provide measurement data to the client device, the measurement data being indicative of at least one of: measured signals; a body parameter value derived from the measured signals, the body parameter including at least one of: a respiration parameter; a cardiac parameter; an impedance parameter; and, a weight parameter.
In one embodiment the measuring device processor: determines a presence of a subject in accordance with signals from at least one of the load cells and the at least one sensor; commences at least one measurement procedure; provides a measurement indication to the client device, the client device is responsive to the measurement indication to display an interface to the subject, the interface being indicative of at least one of: information regarding the measurement process; measured signals; a body parameter value; a body status indicator; instructions to the subject; and, a question for the subject; performs the measurement; and, provides measurement data to the client device, the measurement data being indicative of at least one of: measured signals; a body parameter value derived from the measured signals, the body parameter including at least one of: a respiration parameter; a cardiac parameter; an impedance parameter; and, a weight parameter.
In one broad form, a method is provided for performing at least one impedance measurement on a biological subject, the system including: using a measuring device having: a first housing including spaced pairs of foot drive and sense electrodes provided in electrical contact with feet of the subject in use; a second housing including spaced pairs of hand drive and sense electrodes provided in electrical contact with hands of the subject in use; at least one signal generator electrically connected to at least one of the drive electrodes to apply a drive signal to the subject; at least one sensor electrically connected to at least one of the sense electrodes to measure a response signal in the subject; a measuring device processor that at least in part: controls the at least one signal generator; receives an indication of a measured response signal from the at least one sensor; and, generates measurement data indicative of at least one measured impedance value; and, using a client device in communication with the measuring device, the client device being adapted to receive measurement data allowing the client device to display an indicator associated a result of the impedance measurement.
It will be appreciated that the broad forms of embodiments of the disclosed technology and their respective features can be used in conjunction and/or independently, and reference to separate broad forms is not intended to be limiting. Furthermore, it will be appreciated that features of the method can be performed using the system or apparatus and that features of the system or apparatus can be implemented using the method.
Various examples and embodiments of the disclosed technology will now be described with reference to the accompanying drawings, in which:
An example of an apparatus suitable for performing at least one impedance measurement on a biological subject will now be described with reference to
In this example, the measuring system 100 includes an impedance measuring device 110, including a measuring device processor 112 coupled to at least one signal generator 113 and at least one sensor 114, which are in turn coupled to respective drive and sense electrodes 123, 124, via connections, such as wires or leads 122. Two drive and two sense electrodes are shown in this example, but this is not intended to be limiting and additional electrodes can be provided as will be described in more detail below.
In use, the signal generator 113 generates a drive signal, which is applied to the subject S via the drive electrodes 123, whilst the sensor 114 measures a response signal via the sense electrodes 124. Thus, in use, the measuring device processor 112 controls the at least one signal generator 113 to cause drive signals to be applied to a subject, with a response signal being measured using the at least one sensor 114, allowing the measuring device processor 112 to generate measurement data indicative of at least one measured impedance value. The measurement data can include an indication of the measured signals and/or impedance values derived therefrom, as will be described in more detail below.
The measuring device 110 is typically in communication with a client device 130, such as a portable computer system, mobile phone, tablet or the like, allowing the measurement data to be provided to the client device 130, in turn allowing the client device to display an indicator associated a result of the impedance measurement.
As part of this, the client device 130 can receive measurement data including an indication of the drive/sense signals and/or measured impedance values. The client device 130 can then optionally perform further processing, for example to determine the impedance indicators, such as indicators of body composition or the like. The client device 130 can also combine impedance values or indicators with other information, including indications of disease states or physical characteristics of the subject, determined either by manual user input or based on signals from one or more physical characteristic sensors. This allows the client device 130 to generate collected subject data, which can then be transferred to a remote processing system, such as a server or the like for further analysis and/or storage. Additionally, the client device 130 can analyse historical measurement data, either stored locally or retrieved from the server, allowing changes in measured values over time to be monitored, as will be described in more detail below.
An example of the physical construction of the measuring device is shown in
In this example, the measuring device includes first and second housings 210, 220. The first housing 210 includes two spaced pairs of foot drive and sense electrodes 123.1, 124.1, which are typically made of spaced apart plates provided on an upper surface of the first housing 210, thereby forming footplates on which a user can stand. The second housing 220 includes two spaced pairs of hand drive and sense electrodes 123.2, 124.2 formed from spaced apart plates provided on an upper surface, thereby forming handplates on which a user can rest their hands.
The plate electrodes are typically made of an electrically conductive material, such as a metal, for example stainless steel, and/or another conductive material such as ITO (Indium Tin Oxide), or the like. Throughout the remaining description, reference will generally be made to metal plate electrodes, but it will be appreciated that this is not intended to be limiting.
In any event, the above arrangement utilising two housings allows the unit to be used by having the user stand on the first housing, or alternatively sit on a chair, with their feet resting on the foot drive and sense electrodes. The user can then place their hands on the hand drive and sense electrodes on second housing, which can be supported by a desk or table in a seated arrangement, or by a stand or other support for a standing arrangement.
The use of two housing containing separate electrodes, therefore allows impedance measurements to be performed in a variety of circumstances, and in particular allows measurements to be performed in either seated or standing arrangements, which is important in ensuring the system can be used by individuals having restricted physical capabilities. Additionally, the use of plate electrodes provided in a housing allows the system to be readily used, and avoids the need for preparation, such as cleaning of tissue surfaces or removal of hair, to allow wet electrodes to be applied to the skin.
A number of further features will now be described.
In this example, the first housing 210 is a cuboid having a generally rectangular side profile, with an isosceles trapezoidal shape in plan view, similar to a set of weighing scales. In one example, the housing can be made from moulded upper and lower portions, which couple together to define an internal cavity, which in use contains required components mounted on a circuit board.
The electrodes 123.1, 124.1 are mounted on an upper surface of the upper housing 310.1, with the electrodes 123.1, 124.1 being made of a thin metallic plate, such as stainless steel or the like. The electrodes may have downwardly facing tabs extending through openings in the housing, to thereby couple the electrodes to the housing and allow for electrical connection to the leads within the housing 210. In one example, the electrodes 123.1, 124.1 are slightly biased, for example by having a smaller spacing between openings in the housing than the distance between the tabs, so that the electrode curves slightly away from the housing in a rest position. As a result, the electrodes bend when weight is applied until the electrodes 123.1, 124.1 rest against the housing 210, which in turn helps the electrodes 123.1, 124.1 conform to a shape of the subject's feet. This provides a greater degree of comfort and helps ensure good electrical contact.
To further assist with good electrical contact, the electrodes are sized and positioned to optimise consistent contact with the feet, whilst allowing a range of different feet sizes to be accommodated. In one example, the electrodes are spaced apart by at least one of at least 8 cm, at least 8.2 cm, at least 8.4 cm, up to 9 cm, up to 8.8 cm, up to 8.6 cm, between 8 cm and 9 cm, between 8.2 cm and 8.8 cm, between 8.4 cm and 8.6 cm and more typically approximately 8.5 cm. This enables a range of different foot sizes to be accommodated by the electrodes.
The foot drive and sense electrodes are identically shaped to reduce the number of different parts required to manufacture the device. The foot drive and sense electrodes can have a surface area that is at least one of at least 110 cm, at least 115 cm, at least 120 cm, at least 122 cm, up to 140 cm, up to 135 cm, up to 130 cm, up to 218 cm, between 110 cm2 and 140 cm2, between 115 cm2 and 135 cm2, between 120 cm2 and 130 cm2, between 122 cm2 and 128 cm2 and approximately 125 cm2.
The above described dimensions ensure an approximately consistent surface area of contact between the subject's feet and the electrodes irrespective of minor variations in feet positioning, which helps ensure consistent measurements are obtained, allowing variations in measurements over time to be tracked more accurately. Additionally, the dimensions allow the apparatus to be used by subjects with a range in different feet sizes.
To further assist in controlling foot positioning, the first housing 210 includes a raised section 211.1, 211.2, defining a lip extending at least partially around each pair of foot drive and sense electrodes to thereby guide positioning of a subject's foot relative to the foot drive and sense electrodes in use. In particular, the raised lip includes a rear portion 211.1 configured to engage at least a heel of the user, thereby helping guide the user in positioning their feet in a longitudinal direction, whilst the side portions 211.2 extend along either side of the foot drive and sense electrodes to guide feet placement laterally. Guiding the subject's foot positioning in this manner can ensure good and more importantly, consistent contact between the feet and electrodes each time the system is used.
In this regard, it will be appreciated that whilst this will still allow for some minor variation in positioning between different subjects, for example due to different feet sizes, this helps ensure that any given subject's feet are provided at a consistent position relative to the drive and sense electrodes each time the system is used. This provides reproducible positioning, which in turn reduces variations between successive measurements that could be caused by changes in foot position. Consequently, this helps ensure the system can be used for more reliable longitudinal measurements.
The first housing, and in particular the lower portion 310.2 includes measuring device feet that support the first housing spaced from a surface. The measuring device feet engage load cells mounted within the first housing 210, allowing the measuring device processor 112 to determine a weight of a subject standing on the first housing 210. The measuring device feet are typically adjustable, allowing each of the measuring device feet to be raised or lowered, so that the first housing can be positioned and levelled upon a surface with each of the measuring device feet in engagement with the ground, to thereby ensure accurate weight measurements are captured. A bubble spirit level indicator 212 can be provided on an upper surface of the first housing to thereby ensure accurate levelling of the first housing.
The circuitry provided on the circuit board, will typically include signal generators and sensors for the foot drive and sense electrodes. Additionally, the circuitry can include power systems, for example for voltage conversion or the like.
The second housing 220 is a cuboid having a generally triangular side profile, with an isosceles trapezoidal shape in plan view. In one example, the housing is formed from moulded upper and lower portions, which couple together to define an internal cavity, which in use contains required components mounted on a circuit board (not shown).
The electrodes 123.2, 124.2 are mounted on an upper surface of the upper housing 320.1. The electrodes 123.2, 124.2 are typically made of a thin metallic plate, such as a stainless steel plate, and having tabs extending through openings in the housing 220, to thereby couple the electrodes to the housing and allow for electrical connection to the leads. Again, the electrodes may be raised from the housing in a rest position, so that the electrodes bend when weight is applied, to help the electrodes conform to a shape of the subject's hands. This provides a greater degree of comfort and helps ensure good electrical contact.
Additionally, an upper surface of the second housing is shaped to at least partially conform to a shape of a subject's hands. In particular, the second housing has a curved upper surface, to help the subject rest their hands on the surface even if they are unable to lay their hands out completely flatly, for example due to arthritis, or the like. In one example, the hand sense electrode 124.2 contact the subject's palms, with the drive electrodes 123.2 contacting the fingers. In this instance, as subject's are more likely to have difficulty straightening their fingers, the radius of curvature of the hand drive electrode is different to, and typically less than a radius of curvature of the hand sense electrode, so the hand drive electrode is more curved.
To further assist good electrical contact, over a range of different hand sizes, the hand drive and sense electrodes in each pair are typically spaced apart by at least one of at least 3 cm, at least 3.2 cm, at least 3.4 cm, up to 4 cm, up to 3.8 cm, up to 3.6 cm, between 3 cm and 4 cm, between 3.2 cm and 3.8 cm, between 3.4 cm and 3.6 cm and more typically approximately 3.5 cm.
The hand drive and sense electrodes are identically shaped to reduce the number of different parts required to manufacture the device. The hand drive and sense electrodes can have a surface area that is at least one of at least 35 cm, at least 38 cm, at least 40 cm, at least 41 cm, up to 55 cm, up to 50 cm, up to 45 cm, up to 43 cm, up to 42 cm, between 35 cm2 and 50 cm2, between 38 cm2 and 45 cm2, between 40 cm2 and 43 cm2, between 41 cm2 and 42 cm2, and approximately 41 cm2. The drive electrode has a curved generally rectangular shape and is wider than long to accommodate lateral movement and splaying of the fingers.
Additionally, a guide is provided to assist the subject in positioning their hands. In one example, this is achieved by having a raised portion 221 positioned between each pair of hand drive and sense electrodes, the raised portion defining thumb recesses 221.1 to thereby guide positioning of a subject's thumbs, with the crook of the thumb engaging the raised portion, and hence hands relative to each pair of hand drive and sense electrodes in use. In particular, the raised portion includes two ridges 221.2, each ridge extending towards a respective hand sense electrodes 124.2, and terminating level with an edge of the sense electrode closest to the drive electrode, and being adapted to be positioned between a subject's thumb and forefinger, to thereby guide subject hand placement.
The raised portion 221 can also include a display 222, which is configured to display information, such as a weight, a body status indicator, such as a fluid status, an impedance indicator, or the like, a measurement status indicator, for example showing progression of the measurement process, and/or an error indicator, indicating issues with the measurement procedure.
The second housing can also include a recessed portion 326 along one edge of an underside surface of the second housing, allowing a user to insert their fingers between the second housing and a support surface, to thereby more easily lift the second housing. Connector ports in an underside of the second housing align with a channel on an underside of the housing, which extends front to back, allowing a lead that attaches to the first housing 210 to exit from a front or rear of the second housing. The second housing can accommodate a USB port for charging a tablet or other processing device when coupled thereto.
In one example, the system can be used in conjunction with a stand and an example of this will now be described with reference to
In this example, the stand 300 includes a base 310 that supports the first housing 210, a platform 320 that supports the second housing 220, and a leg 330 coupled to the base 310 and platform 320 to support the platform 320 relative to the base 310. The stand 300 can be made of any suitable material, and in one example, includes metal plates, such as aluminium or steel plates, forming the base 310 and platform 320, with the leg being made of extruded aluminium or the like.
The base 310 typically includes mounting brackets having a tongue spaced from the base 310, and which are configured to receive the measuring device feet, allowing the feet to be slid into engagement with the mounting brackets, to thereby secure the first housing 210 to the base 310. The platform 320 may include lugs which engage holes in an underside of the second housing, allowing the second housing to be clipped onto the platform.
The leg typically includes a trough including a flexible or pliant cover 341 including a slit extending along the length of the cover, allowing the connector lead to be inserted through the slit into the trough so it can be hidden from view in use.
The leg 430 is typically curved so that a centre of the platform 420 is offset from a centre of the base 410 in a longitudinal direction, so that as the subject stands on the first housing the second housing is provided in front of the subject. The platform is typically spaced from the base by a vertical distance of at least one of at least 100 cm, at least 103 cm, at least 104 cm, at least 105 cm, up to 110 cm, up to 108 cm, up to 107 cm, up to 106 cm, between 100 cm and 110 cm, between 103 cm and 108 cm, between 104 cm and 107 cm and between 105 cm and 106 cm. The use of a fixed relative position between the base and platform means that the subject is in the same physical position each time a measurement is performed, which helps ensure that changes in readings are as a result of changes in fluid levels and not simply due to redistribution of fluids caused by a change in subject position. It will be appreciated that this allows consistent measurements to be performed on a single subject between different pieces of equipment, allowing measurements to be compared even if different measuring devices are used.
The stand can incorporate lighting, such as LEDs mounted in the platform, base or leg, for aesthetic appearances.
The stand can further incorporate a support 331, for supporting a processing system, such as the client device 130, and in particular a tablet, smartphone or other similar client device. The support can be magnetic, thereby magnetically coupling the client device to the support, to reduce the chance of this being inadvertently dislodged. The support 331 can incorporate or be coupled to a handle 332 to assist with positioning of the stand. In this regard the base 310 includes wheels 311 on a rearward edge, so the stand can be tipped backwards and supported on the wheels, allowing a user to grasp the handle and roll the stand, allowing this to be more easily moved.
In the above example, the apparatus includes four drive electrodes and four sense electrodes. Accordingly, in one example, a four channel system can be provided, and an example of this will now be described with reference to
In this example, the system includes the measuring device processor 512, which is in turn connected to signal four generators 513, allowing drive signals to be applied to each of the drive electrodes 123. Eight sensors 514 are provided coupled to each of the sense electrodes 124, as well as the drive electrodes 123, allowing the drive electrodes to be used for sensing, for example when sensing ECG or other body signals.
The measuring device processor 512 is also typically connected to the load cells 312.3, allowing weight measurements to be performed, as well as a communications module 517 for communication with the client device 130.
In use, the measuring device processor selectively controls the four signal generators 513 and four sensors 514 coupled to the sense electrodes 124, to perform a sequence of impedance measurements, including segmental impedance measurements and/or whole of body impedance measurements. In this regard, example electrode arrangements are shown in
The manner in which impedance measurements are performed will now be described in more detail. In particular, the measuring device processor 512 is adapted to generate control signals, which cause the signal generators 513 to generate one or more alternating signals, such as voltage or current signals of an appropriate waveform, which can be applied to a subject S, via the first electrodes 123. The measuring device processor 512 also receives an indication of measured response signals from the sense electrodes 124 and sensors 514, processing these and an indication of the applied drive signals to determine impedance values. It will be appreciated that the measuring device processor 512 may be any form of electronic processing device capable of performing appropriate control, and could include an FPGA (field programmable gate array), or a combination of a programmed computer system and specialised hardware, or the like.
The signal generators 513 could be of any appropriate form, but will typically include digital to analogue converters (DACs) for converting digital signals from the processing device to analogue signals, which are amplified to generate the required drive signals, whilst the sensors 514 typically includes one or more amplifiers for amplifying sensed response signals and analogue to digital converters (ADCs) to digitise the analogue response signals and providing digitised response signals to the processing device.
The nature of the alternating drive signal will vary depending on the nature of the measuring device and the subsequent analysis being performed. For example, the system can use Bioimpedance Analysis (BIA) in which a single low frequency signal is injected into the subject S, with the measured impedance being used directly in the determination of biological parameters. In one example, the applied signal has a relatively low frequency, such as below 100 kHz, more typically below 50 kHz and more preferably below 10 kHz. In this instance, such low frequency signals can be used as an estimate of the impedance at zero applied frequency, commonly referred to as the impedance parameter value R0, which is in turn indicative of extracellular fluid levels.
Alternatively, the applied signal can have a relatively high frequency, such as above 200 kHz, and more typically above 500 kHz, or 1000 kHz. In this instance, such high frequency signals can be used as an estimate of the impedance at infinite applied frequency, commonly referred to as the impedance parameter value R∞, which is in turn indicative of a combination of the extracellular and intracellular fluid levels, as will be described in more detail below.
Alternatively and/or additionally, the system can use Bioimpedance Spectroscopy (BIS) in which impedance measurements are performed at each of a number of frequencies ranging from very low frequencies (1 kHz and more typically 3 kHz) to higher frequencies (1000 kHz), and can use as many as 256 or more different frequencies within this range. Such measurements can be performed by applying a signal which is a superposition of plurality of frequencies simultaneously, or a number of alternating signals at different frequencies sequentially, depending on the preferred implementation. The frequency or frequency range of the applied signals may also depend on the analysis being performed.
When impedance measurements are made at multiple frequencies, these can be used to derive one or more impedance parameter values, such as values of R0, Zc, R∞, which correspond to the impedance at zero, characteristic and infinite frequencies. These can in turn be used to determine information regarding both intracellular and extracellular fluid levels, as will be described in more detail below.
A further alternative is for the system to use Multiple Frequency Bioimpedance Analysis (MFBIA) in which multiple signals, each having a respective frequency are injected into the subject S, with the measured impedances being used in the assessment of fluid levels. In one example, four frequencies can be used, with the resulting impedance measurements at each frequency being used to derive impedance parameter values, for example by fitting the measured impedance values to a Cole model, as will be described in more detail below. Alternatively, the impedance measurements at each frequency may be used individually or in combination.
Thus, the measuring device 110 may either apply an alternating signal at a single frequency, at a plurality of frequencies simultaneously, or a number of alternating signals at different frequencies sequentially, depending on the preferred implementation. The frequency or frequency range of the applied signals may also depend on the analysis being performed.
In one example, the applied signal is generated by a voltage generator, which applies an alternating voltage to the subject S, although alternatively current signals may be applied. In one example, the voltage source is typically symmetrically arranged, with two signal generators 313 being independently controllable, to allow the signal voltage across the subject to be varied, for example to minimise a common mode signal and hence substantially eliminate any imbalance as described in copending patent application number WO2009059351.
As the drive signals are applied to the subject, the sensors 514 then determines the response signal in the form of the voltage across or current through the subject S, using sense electrodes 124. Thus, a voltage difference and/or current is measured between the sense electrodes 124. In one example, a voltage is measured differentially, meaning that two sensors 514 are used, with each sensor 514 being used to measure the voltage at each sense electrode 124 and therefore need only measure half of the voltage as compared to a single ended system. Digitised response signals are then provided to the measuring device processor 512, which determines an indication of the applied drive signal and measured response signals, and optionally uses this information to determine measured impedances.
In this regard, the response signal will be a superposition of voltages generated by the human body, such as the ECG (electrocardiogram), voltages generated by the applied signal, and other signals caused by environmental electromagnetic interference. Accordingly, filtering or other suitable analysis may be employed to remove unwanted components.
The acquired signal is typically demodulated to obtain the impedance of the system at the applied frequencies. One suitable method for demodulation of superposed frequencies is to use a Fast Fourier Transform (FFT) algorithm to transform the time domain data to the frequency domain. This is typically used when the applied current signal is a superposition of applied frequencies. Another technique not requiring windowing of the measured signal is a sliding window FFT.
In the event that the applied current signals are formed from a sweep of different frequencies, then it is more typical to use a signal processing technique such as multiplying the measured signal with a reference sine wave and cosine wave derived from the signal generator, or with measured sine and cosine waves, and integrating over a whole number of cycles. This process, known variously as quadrature demodulation or synchronous detection, rejects all uncorrelated or asynchronous signals and significantly reduces random noise. Other suitable digital and analogue demodulation techniques will be known to persons skilled in the field.
In the case of BIS, impedance or admittance measurements are determined from the signals at each frequency by comparing the recorded voltage and the current through the subject. The demodulation algorithm can then produce amplitude and phase signals at each frequency, allowing an impedance value at each frequency to be determined.
Whilst the measured impedance can be used directly, in one example, the measured impedance is used to derive an impedance parameter, such as an impedance (resistance) at zero frequency, R0, which equals the extracellular resistance Re, or the impedance at a theoretical infinite frequency R∞, which can be used with R0 to derive an intracellular resistance Ri, as well as other impedance parameters. The impedance parameters may be determined in any one of a number of manners such as by:
In one example, the frequencies used are in the range 0 kHz to 1000 kHz, and in one specific example, four measurements are recorded at frequencies of 25 kHz, 50 kHz, 100 kHz, and 200 kHz, although any suitable measurement frequencies can be used.
A further alternative for determining impedance parameter values is to perform impedance measurements at a single frequency, and use these as an estimate of the parameter values. In this instance, measurements performed at a single low frequency (typically less than 50 kHz) can be used to estimate R0, measurements at a single high frequency (typically more than 100 kHz) can be used to estimate R∞, allowing a value of Ri to be determined.
The above described equivalent circuit models the resistivity as a constant value and does not therefore accurately reflect the impedance response of a subject, and in particular does not accurately model the change in orientation of the erythrocytes in the subject's blood stream, or other relaxation effects. To more successfully model the electrical conductivity of the human body, an improved CPE based model may alternatively be used.
When performing measurements of cardiac and/or respiratory parameters, the system is typically used passively, with signals being measured via the sense electrodes 124 and optionally also via the drive electrodes 123. The detected signals are a superposition of voltages generated by the human body, and will include cardiac and respiratory components, which can typically be isolated through suitable filtering, for example 1-40 Hz for cardiac signals and below 1 Hz for respiratory signals.
A typical measurement process using the above described apparatus will now be described with respect to
In this example, at step 600 the system acts to detect the presence of a subject. This can be achieved in any suitable manner, and could involve detecting the weight of a subject standing on the first housing, contact with the drive or sense electrodes, or activation of a suitable application on the client device 130, with this being communicated to the measuring device.
At step 610, the measuring device processor provides a measurement indication to the client device, thereby allowing the client device 130 to display relevant information to the subject at step 620. The information can include any information regarding the measurement process, including an indication of the measurement being performed, a time to completion, instructions to the subject, for example asking the subject to stand still, or the like. This allows the subject to prepare for the measurement, and ensure they are positioned correctly for the relevant measurement being performed. The interface could also display information regarding the measurements, including results, previous measurements or the like, as well as questions requesting further information from the user, such as asking the user questions relating to current symptoms, or the like.
At step 630 the measuring device processor 512 performs a measurement procedure. Typically multiple measurement procedures are performed in sequence, for example by performing a weight measurement, impedance measurement and then measurement of cardiac and/or respiratory parameters. It will be appreciated that the system may be configured to always perform each of these, or alternatively may be configured to only perform selected ones of the procedures depending on the preferred implementation and/or current settings.
As the measurement process is completed, the measuring device processor determines measurement data at step 640, which can include raw data, such as values of the magnitude and/or phase of measured signals, processed values, such as impedance values, or the like. The measurement data is provided to the client device 130, at step 650, allowing client device to display a body status indicator indicative of a body status of the subject.
The nature of the body status indicator will vary depending on the preferred implementation and could include a simple indication of measured parameter values, such as impedance values, a heart rate, respiration rate, or the like. Alternatively, the body status indicator could include values derived from the measured parameter values, such as an indication of body composition parameters, an indication of relative water levels, measurement of a disease state or the like. The body status indicator could be based on current measurements alone, or could take into account prior measurements, for example, examining variations in fluid levels over time.
Accordingly, the above described process can detect the presence of the subject and then trigger the measurement process, including an impedance measurement process, and optionally other measurement processes, with information being presented to the subject via the client device.
A number of further features will now be described.
In one example, the body status indicators can include, but are not limited to any one or more of:
In one example, the measuring device processor 512 provides a measurement indication to the client device, the measurement indication being indicative of a measurement being performed. Thus, the measuring device processor 512 can determine a presence of a subject in accordance with signals from at least one of the load cells and the at least one sensor, commence at least one measurement procedure and provide the measurement indication to the client device. The client device is responsive to the measurement indication to display information to the subject including information regarding the measurement process, measured signals, a body parameter value, a body status indicator, instructions to the subject and a question for the subject. This allows the system to automatically commence measurements and display relevant information to the subject, so the subject can see the measurement is being performed, and allowing them to take appropriate action, such as standing in a correct position.
In one example, the measuring device processor detects when a subject is standing on the foot unit in accordance with signals from at least one of the load cells and causes a weight measurement procedure to be performed using signals from the load cells. Thus, this can be used to automatically trigger a weight measurement process when the subject stands on the first housing. Similarly, the measuring device processor detects when a subject's hands and feet are positioned in contact with the hand and feet electrodes in accordance with signals from the at least one sensor and cause a measurement procedure to be performed including at least one of an impedance measurement procedure, a cardiac measurement procedure and a respiration measurement procedure. Thus, a suitable measurement can be automatically performed depending on the subject's interaction with the measuring device, with impedance or other measurements only being performed when the subject's hands and feet are in contact with the respective electrodes, whilst weight measurements are performed when the subject's hands are not in contact with the hand sense/drive electrodes.
Thus, in one example, the measuring device processor detects when a subject is standing on the foot unit in accordance with signals from at least one of the load cells, provides weight measurement indication to the client device, the client device being responsive to the weight measurement indication to instruct the subject to stand for a weight measurement, before the weight measurement is performed. Following this, the measuring device processor provides a body measurement indication to the client device, the client device being responsive to the body measurement indication to instruct the subject to place their feet and hands on the respective electrodes, detects when a subject's hands and feet are positioned in contact with the hand and feet electrodes in accordance with signals from the at least one sensor and commences an impedance measurement procedure, a cardiac measurement procedure or respiration measurement procedure. Following this results can be displayed to the user. Thus, this allows the subject to be informed throughout the measurement process, whilst ensuring the process only progresses once the subject is correctly positioned, thereby ensuring accuracy of the measurements.
A specific example system will now be described in more detail with reference to
In this example, the system 700 includes a number of measuring systems 100 coupled via a communications network 740 to one or more processing devices, such as a server 750, which may in turn be coupled to a database 751. This arrangement allows subject data to be collected by the measurement systems 100 and provided to the server 750 for storage and optional analysis. Collected subject data may be stored in the database 751 together with other information, such as body state indicators, allowing this information to be remotely accessed and viewed by authorised users, such as clinicians, or the like.
In the above arrangement, the communications network 740 can be of any appropriate form, such as the Internet and/or a number of local area networks (LANs) and provides connectivity between the measuring systems 100 and the server 750. It will however be appreciated that this configuration is for the purpose of example only, and in practice the measuring systems 100 and server 750 can communicate via any appropriate mechanism, such as via wired or wireless connections, including, but not limited to mobile networks, private networks, such as an 802.11 networks, the Internet, LANs, WANs, or the like, as well as via direct or point-to-point connections, such as Bluetooth, or the like.
Accordingly, it will be appreciated that the client device 130 can be of any appropriate form and one example is shown in
In this example, the client device 130 includes at least one microprocessor 800, a memory 801, an input/output device 802, such as a keyboard and/or display, and an external interface 803, interconnected via a bus 804 as shown. The external interface 803 can be utilised for connecting the client device 130 to peripheral devices, such as the communications networks 740, databases, other storage devices, or the like. Although a single external interface 803 is shown, this is for the purpose of example only, and in practice multiple interfaces using various methods (eg. Ethernet, serial, USB, wireless or the like) may be provided.
In use, the microprocessor 800 executes instructions in the form of applications software stored in the memory 801 to allow communication with the server 750, for example to allow subject data to be provided to the sever, or the like.
Accordingly, it will be appreciated that the client device 130 may be formed from any suitable processing system, such as a suitably programmed PC, Internet terminal, lap-top, or hand-held PC, and in one preferred example is either a tablet, or smart phone, or the like. Thus, in one example, the client device 130 is a standard processing system such as an Intel Architecture based processing system, which executes software applications stored on non-volatile (e.g., hard disk) storage, although this is not essential. However, it will also be understood that the client devices 130 can be any electronic processing device such as a microprocessor, microchip processor, logic gate configuration, firmware optionally associated with implementing logic such as an FPGA (Field Programmable Gate Array), or any other electronic device, system or arrangement.
An example of a suitable server 750 is shown in
In use, the microprocessor 900 executes instructions in the form of applications software stored in the memory 901 to allow the required processes to be performed, including communicating with the client devices 130, and optionally receiving, analysing and/or displaying results of impedance measurements. The applications software may include one or more software modules, and may be executed in a suitable execution environment, such as an operating system environment, or the like.
Accordingly, it will be appreciated that the server 750 may be formed from any suitable processing system, such as a suitably programmed client device, PC, web server, network server, or the like. In one particular example, the server 750 is a standard processing system such as an Intel Architecture based processing system, which executes software applications stored on non-volatile (e.g., hard disk) storage, although this is not essential. However, it will also be understood that the processing system could be any electronic processing device such as a microprocessor, microchip processor, logic gate configuration, firmware optionally associated with implementing logic such as an FPGA (Field Programmable Gate Array), or any other electronic device, system or arrangement. Accordingly, whilst the term server is used, this is for the purpose of example only and is not intended to be limiting.
Whilst the server 750 is a shown as a single entity, it will be appreciated that the server 750 can be distributed over a number of geographically separate locations, for example by using processing systems and/or databases 751 that are provided as part of a cloud based environment. Thus, the above described arrangement is not essential and other suitable configurations could be used.
Operation of the system will now be described in further detail with reference to
For the purpose of these examples it will also be assumed that subjects use the client devices 130 to interact with or control the measuring device 110, allowing impedance and/or other measurements to be performed and allowing information, such as information regarding physical characteristics, to be collected. This is typically achieved by having the subject interact with the system via a GUI (Graphical User Interface), or the like presented on the client device 130, which may be generated by a local application, or hosted by the server 750, which is typically part of a cloud based environment, and displayed via a suitable application, such as a browser or the like, executed by the client device 130. Actions performed by the client device 130 are typically performed by the processor 800 in accordance with instructions stored as applications software in the memory 801 and/or input commands received from a user via the I/O device 802. Similarly, actions performed by the server 750 are performed by the processor 900 in accordance with instructions stored as applications software in the memory 901 and/or input commands received from a user via the I/O device 902, or commands received from the client device1.
The system utilises multiple measuring and client devices 110, 130, which interact with one or more central servers 750, typically forming part of a cloud based environment. This allows subject data to be collected from a number of different sources, and then aggregated and stored centrally, in turn allowing the system to function as an electronic medical record system.
Whilst the following example focuses on the analysis of impedance indicators only, it will be appreciated that the techniques could be extended to include other parameter values, such as other vital signs or the like, and reference to impedance indicators only is not intended to be limiting.
However, it will be appreciated that the above described configuration assumed for the purpose of the following examples is not, and numerous other configurations may be used. It will also be appreciated that the partitioning of functionality between the measuring device 110, client devices 130, and servers 750 may vary, depending on the particular implementation.
In this example, at step 1000 the subject optionally activates the client device 130, which would typically involve opening an application installed on the client device in order to allow the measurement process to commence.
At this time, the subject may optionally be prompted to provide authentication information, which may involve supplying biometric information, for example by performing an iris scan, fingerprint scan, or the like, or alternatively entering information such as a password, PIN or similar. As a further alternative, authentication information can be derived from the results of measurements performed below, for example by basing authentication information on a combination of measured parameters, such as a height, weight, and impedance values. Provided authentication information can then be used to authenticate and identify the subject, with this being performed locally by the client device 130, or remotely by the server 750 depending on the preferred implementation.
A measurement procedure may also be selected. In this regard a number of different measurement procedures may be implemented depending on a range of factors, such as the software modules loaded onto the client device 130, conditions suffered by the subject, body status indicators to be displayed, or the like. The process of selecting a measurement procedure can involve displaying information regarding available measurement procedures allowing a user to select one of these. Alternatively, this may be performed automatically, for example by selecting a measurement procedure based on the software installed on the device. As a further alternative this may not be required if identical measurement processes are used irrespective of the information presented to the subject.
At step 1005 the subject stands on the foot unit comprising the first housing 210, with the measuring device processor 512 detecting this based on signals from the load cells at step 1010. At step 1015, the measuring device processor 512 generates a weight measurement indication, which is provided to the client device 130 at step 1020, causing the client device to notify the subject that the weight measurement is to commence, optionally providing instructions, such as instructing the subject to stands still with their hands by their sides, to prevent the subject inadvertently resting their hands on the hand unit, thereby compromising the weight measurement. Once signals from the weight sensors have reached equilibrium, a weight measurement is performed and weight data generated.
At step 1030, the measuring device processor 512 provides the client device 130 with a body measurement indication, causing the client device to notify the subject to place their hands on the hand unit comprising the second housing 220, with their hands and in contact with the respective hand drive and sense electrodes at step 1040. Contact with the electrodes is detected by applying a drive signal to the drive electrodes and measuring the response signal to ensure successful contact has been achieved at step 1045. It will be appreciated that if this has not occurred additional instruction can be provided to the subject in a manner similar to that outlined above.
At step 1050, impedance measurements are commenced, with a sequence of drive signals being applied to respective ones of the drive electrodes, and measurements being performed via respective sense electrodes. In general, two signal generators are activated at step 1050, so that drive signals are applied via two of the drive electrodes, with response signals being detected via two of the sense electrodes at step 1055. This is repeated for different combinations of electrodes until desired measurements have been performed. In one preferred example, this process is performed to collect impedance measurements at multiple frequencies, and typically 256 or more frequencies, with this being performed to measure segmental impedance values for each limb, and the torso, as well as whole of body impedance measurements.
At step 1060, a cardiac/respiration measurement is performed, with the sensors 514 being activated to measure body signals at step 1065.
At step 1070 the measured signals are used by the measurement device processor 512 to generate measurement data. The measurement data can include raw data or may include partially or fully processed data. For example, minimal processing such as filtering of signals is typically performed by the measuring device. Additionally, voltage and current signals may be processed in order to determine impedance values such as resistance, reactance and phase angle values. For example, in the case of BIS, impedance or admittance measurements are determined from the signals at each frequency by comparing the recorded voltage and the current through the subject. The demodulation algorithm can then produce amplitude and phase signals at each frequency, allowing an impedance value at each frequency to be determined. The measurement data can include processed signals as well as raw data depending on the preferred implementation. In general inclusion of the raw data is preferred as this can allow data to be reprocessed at a later date, for example allowing this to be analysed using improved algorithms.
At step 1075 the measurement data is provided to the client device 130, typically using a short range wireless communication protocol such as Bluetooth, NFC or the like. The use of a short range protocol reduces the likelihood of the measurement data being intercepted by third parties. Irrespective of this however the measurement data can be encrypted utilising a public key of the client device. With the data also further being optionally signed by a private key of the measuring device to thereby verify the source of the measurement data and hence help ensure measurement data integrity.
At step 1080 the client device 130 may optionally request additional information, with this being provided by the subject at step 1085. This could include requesting authentication information, if this has not previously been provided. Alternatively, this could include displaying a question to the subject. The question may relate to symptoms or other information required by the system, such as information regarding physical characteristics, exercise, diet or the like, allowing additional information regarding the subject to be collected. By doing this each time a measurement is performed allows a wide range of data regarding the subject to be collected, without placing an undue burden on the subject.
It will also be appreciated that other measurements could also be performed in addition to those outlined above, for example using other suitable sensing mechanisms. For example, the client device 130 may be equipped with sensors allowing additional information, such as a subject temperature to be measured.
The measurement data is collated with any other relevant information, with collected subject data being provided to the server 750 at step 1090. The collected subject data typically includes the measurement data and any additional data, such as responses to questions, data collected from additional sensors, such as physical characteristic data, but may also include other data such as environmental data, including but not limited to location data, temperature data, of the like. The collected subject data may be encrypted using a suitable encryption mechanism, such as encrypting the collected subject data using a public key of the server 750, and optionally signing the collected subject data using a private key of the client device 130, thereby ensuring privacy of the collected subject data is maintained.
At step 1095, the server 250 updates subject data stored in the subject database 751, by adding the collected subject data. It will be appreciated that this allows subject data relating to the individual to be collected over time, which in turn enables a comprehensive health record to be established directly from measurement data recorded from a measuring device. Once subject data has been recorded, this can be used to generate a body status indicator which is displayed to the subject. The body status indicator can be displayed at any time during the process and this does not need to wait until collected subject data has been uploaded to the server. Indeed, this can be performed concurrently with the data collection process.
The nature of the body status indicator will vary depending on the preferred implementation and the nature of the measurement data. The body status indication could include a simple recorded value but more typically examined changes in parameter values such as changes in fluid levels or the like. The nature of the body status indicator is not important for the purposes of the current example and numerous body status indicators will be known to those in the art, for example as listed above.
In one example the body status indicator is generated locally using the client device 130, as shown in
In this example step 1100 the client device 130 determines if previously measured body parameter values are required. It will be appreciated that these may not be required, for example if they are already stored locally on the client device 130, or if they are not needed to generate the body status indicator. Assuming previous body parameter values are required, at step 1105 the client device 130 generates a subject data request which is transferred to the server 250. At step 1110 the server 250 retrieves relevant subject data, returning this retrieved subject data to the client device 130 at step 1115. At step 1120, the client device 130 calculates the body status indicator, for example by determining a change in the body parameter value, causing this to be displayed to the subject at step 1125.
At this stage, the client device 130 may also optionally generate a notification, for example based on comparison of the body parameter value and/or body status indicator to a reference range or other notification criteria. The notification can be displayed on the client device 130, and may include a motivational message, alert, warning, or the like. For example, if the user has an unexpectedly high heart rate, or if fluid levels have changed dramatically in a short period of time, a warning may be displayed to the subject directing them to seek medical attention.
Additionally, and/or alternatively notifications can be provided to other authorised users. For example, subjects can grant specific users, such as medical practitioners, authorisation to access their subject data. In this instance the client device 130 can generate a notification and transfer this to an authorised user, such as the subject's doctor, alerting them to a particular event. This can be used to allow the medical practitioner to contact the subject directing them to seek medical attention.
It will be appreciated that the above-described process may require that subject data is retrieved and provided to the client device 130. As an alternative to this however the body status indicator could be generated by the server 250 and transferred to the client device, and an example of this will now be described with reference to
In this example, the server 250 retrieves required subject data at step 1150 and then calculates the body status indicator at step 1155. The body status indicator is then transferred to the client device 130 at step 1160, allowing this to be displayed to the subject at step 1165. The server 250 may then optionally generate a notification at step 1170 allowing this to be provided to the client device 130 or a client device of an authorised user as required.
It will be appreciated that features from different examples above may be used interchangeably where appropriate. Furthermore, whilst the above examples have focussed on a subject such as a human, it will be appreciated that the measuring device and techniques described above can be used with any animal, including but not limited to, primates, livestock, performance animals, such race horses, or the like. The above described processes can be used for diagnosing the presence, absence or degree of a range of conditions and illnesses, including, but not limited to oedema, lymphodema, body composition, or the like, and reference to specific indicators is not intended to be limiting.
Throughout this specification and claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers. As used herein and unless otherwise stated, the term “approximately” means±20%.
Persons skilled in the art will appreciate that numerous variations and modifications will become apparent. All such variations and modifications which become apparent to persons skilled in the art, should be considered to fall within the spirit and scope that the invention broadly appearing before described.
