GB2524224A

GB2524224A - Heart activity and blood flow measuring device

Info

Publication number: GB2524224A
Application number: GB1400610.0A
Authority: GB
Inventors: Dennis Majoe
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-01-14
Filing date: 2014-01-14
Publication date: 2015-09-23
Also published as: GB2524224A9; GB201400610D0

Abstract

A heart activity and blood flow measuring device comprising of a hand held master unit 3 and a plurality of sensor units, wherein the first type is used to measure electro cardio activity of the heart, and the second type is used to measure absorption of infrared and red light by the blood in the region under the sensor unit placed on a human body. The plurality of sensor units will preferably communicate with the master unit and may also receive power from said master unit. The sensors will preferably include a computing component, a means to communicate wirelessly with the master unit, a timing component, memory, signal amplification and digital electronics.

Description

Heart Activity and Blood Flow Measuring Device This invention relates to a wireless approach to measuring blood flow and oxygenation at several points of the human body relative in time to the body heart beat.

In many health related conditions blood flow around the body can be compromised due to improper functioning or blockage of the arterial and venal pathways as well as changes in the flow properties of the blood. Examples are the effects of diabetes on blood properties and artherosclerosis of the extremities in peripheral vascular disease and constriction in Raynauds.

A blood pressure reading provides a global indicator of the combined status of the heart and the vascular system. However measuring blood flow as a response of the heart beat at spatially different points on the body provides a more detailed regional analysis of the cardio vascular system. The detection of changes in spatial blood flow and blood oxygenation patterns over time or when compared to normative data for a given comparative healthy population can be used as a predictor for a wide range of diseases. In particular the patterns should be detected at different sites on the human body at which one would expect particular pattern changes for particular diseases. For example one would consider flow to the outer limbs and their extremities in relation to diabetes, around the chest for heart and lung diseases and on the neck and head for problems relating to oxygenation of the brain.

The measuring device is composed of two types of sensor a plurality of which may be placed at different sites on the human body surface, a first type to detect the heart beat using electro cardio potential monitoring and a second type which measures blood flow and blood oxygenation indirectly due to infrared and red light absorption, referred to from now on as infrared absorption, by sub-dermal blood flow. In addition the measuring device includes a master unit, such as a smart mobile phone, that is portable and is brought near each sensor unit during a measurement procedure in order to communicate with and control the sensors and it may also provide a source of recharge power to the sensors.

An example of the invention will now be described by referring to the accompanying drawings: * figure 1 shows the master unit, the first type unit measuring electro cardio potential, the second type sensor unit measuring blood flow and oxygenation indirectly using infrared absorption, the sensor units displaced around the human body in areas where one may record blood flow and oxygenation for the purposes of diagnosing disease * figure 2a shows the first type unit from plan and side view comprising commercially available off the shelf electrode pads to which are clipped the reference electrode connector and a primary electrode connector as well as adjoining electrical cable * figure 2b shows the first type unit with internal detail of the reference electrode connector and the primary electrode connector * figure 2c shows the modules that make up the system on chip integrated circuit that performs the electro cardio potential measurement and recording * figure 3a shows the second type unit in plan with internal detail and in side view showing the adhesive pad that allows the sensor to be held flat against the skin.

* figure 3b shows the protrusion of the infrared emitters and detectors from the base fabric * figure 3c shows the modules that make up the system on chip integrated circuit that performs the infrared absorption measurement and recording The present invention describes an electronic measurement device comprising a master unit 3 and sensor units a first type 1 which is used to measure electra cardio activity of the heart and a second type 2 which is used to measure absorption of infrared light by the blood in the region under the sensor unit, as shown placed on a human body in Figure 1. The first and second type units may communicate with the master unit. The sensor units may receive power inductively from the master unit and having done so may operate for some time under this received power. The first and second type units include a computing component, a means to communicate wirelessly with the master unit, a timing component, memory and signal amplification and digitisation electronics.

When the master unit communicates with a first or second type unit, the master will initialise the timers in each type unit with current real clock time as defined by the real time clock inside the master unit. The first type units, detect the electrical potential between electrode pad contacts 4 and 5 in order to measure electro cardio activity of the heart and storing the electrical potentials as digitised waveforms in the memory. When the first type unit records in memory the electro cardio activity each waveform sample is annotated digitally with the real clock time measured by that first type unit. The second type units, include infrared light emitting diodes, infrared light level detectors, signal amplification and digitisation electronics to detect the amount of infrared light, generated by the emitting diodes, that is reflected back by the skin and flesh of the user into the infrared detectors and stores the reflection level as a digitised waveform in the memory. This waveform indirectly corresponds to blood flow and blood oxygen saturation in the sub-dermal flesh of the user below the second type unit. When the second type unit records in memory the level of reflected infrared light each waveform sample is annotated digitally with the real clock time measured by that second type unit. When the first and second type units have operated for some time and after several heart beats, the master unit is brought close to each first or second type unit and the stored digitised waveforms are communicated and stored into the master unit. The master unit may then use the recordings to assess heart activity, blood flow and blood oxygenation at several parts of the body, with emphasis on measuring the time delays between specific features in each measure, and can thereby infer potential diseases.

Since the blood flow at remote parts of the body may be affected by the orientation of the body relative to the vertical, each sensor unit includes an accelerometer sensor to detect the gravitational force vector and to provide a measure of the inclination of the limb to which the sensor is attached. The inclination value should be provided to the master unit as part of the waveform recording data record.

In a preferred embodiment the first type unit comprises two electrode connectors 6 and 7.

The reference electrode connectorS click fits onto a standard commercial off the shelf dry gel adhesive backed electrode 4 commonly used in clinical practice. The primary electrode connector 7 also click fits to a second dry gel adhesive backed electrode 5. The primary electrode connector consists of a thin pad 8 into which a nearfield induction coil is imprinted 9 which connects to application specific integrated circuits (ASIC) 10 in a single or multi-chip form factor. The ASIC chip adheres to the thin pad 8. The ASIC connects electrically to the local electrode clip 11 and also connects electrically to the remote reference electrode via the attached wire 12.

The first type unit ASIC includes a front end module 13, a computing module 14 with CPU core 15, flash memory storage 16 and real time clock 17 and a near field communications back end module 18.

When a master unit is brought near the first type unit, the master unit's oscillating inductive field couples to the imprinted induction coil and is used to both power the first type unit and charge its power storage capacitor as well as to allow data communication between the master and the first type unit.

The front end module 13 incorporates an instrumentation differential voltage amplifier preferably exhibiting very high input impedance, high gain between 1000 and 10000 times and high common mode voltage rejection. The differential input of the amplifier is connected to the primary and reference electrodes so as to measure the electro cardio potential voltage between the electrodes applied to the human skin. The output of the instrumentation amplifier (IA) drives a second amplifier circuit which in turn drives the offset input terminals of the IA such that any long term drift of the IA output can be compensated ensuring the output remains within the range of the power rails. The output of the IA is used as input to a second amplifier which acts as a low pass filter aimed to allow through signal frequencies up to 40Hz at near unit gain while attenuating higher frequencies. The front end preferably includes an accelerometer sensor, such as a 3 axis sensor based on MEMS technology and an analogue to digital converter which is used to digitise the filtered output of the IA as well as the three voltages of the 3 axis accelerometer.

The computing module comprises a central processing unit (CPU) core 15 connected to a real time clock 17 and flash memory 16. The computing unit connects to the front end module controlling the analogue to digital converter and the reading of the digitised voltages. The CPU is programmed to store the digitised values as well as the real time clock information into flash memory at a regular sample period. The CPU may also perform additional calculations and data compression as it is preferably required to perform optimally. When the master unit is inductively coupled to a first type unit and can engage in communications the master unit provides the first type unit the current real time clock of the master unit such that the two units are time synchronised.

The computing module is connected to the back end module in order to engage in communications over the near field inductive link. The back end module performs the required control and regulation of the near field communications link and the also scavenges power from the inductive link to power the ASIC and to charge a storage capacitor, which continues to provide power to the ASIC when the master unit is removed and the inductive link is broken. Preferably the back end module implements the Standard ECMA-340 Near Field Communication Interface and Protocol (NFCIP-1) 3rd edition (June 2013) using inductive coupled devices operating at the centre frequency of 13,56 MHz for interconnection of computer peripherals.

In a preferred embodiment the second type unit consists of a thin pad 18 into which a near field induction coil 19 is imprinted which connects to application specific integrated circuits (ASIC) in a single or multi-chip form factor. The ASIC chip adheres to the thin pad. The ASIC drives power selectively to two infrared light emitting diodes, 21 and 22, emitting at 660nm and 9lOnm respectively. The light is directed into the sub-dermal layers of the human skin to which the thin pad is adhered by way of adhesive pads. The diodes are driven in turn. The level of reflected light received back in the light detector 23 is digitised and recorded with measurements being taken at high sample rate.

The second type unit ASIC includes a front end module 24, a computing module 25 and a back end module 26 similar to the first type unit.

When a master unit is brought near the second type unit, the master unit's oscillating inductive field couples to the imprinted induction coil and is used to both power the second type unit and charge its power storage capacitor as well as to allow data communication between the master and the second type unit. The ASIC includes a front end module, a computing module with flash memory storage and real time clock and a near field communications back end module.

The front end module incorporates drive transistors that can switch current into the infrared emitting diodes as well as a detector amplifier (DA) that scales the output of the light detector voltage appropriately. The output of the DA drives a second amplifier circuit which in turn drives the offset input terminals of the DA such that any long term drift of the

S

DA output, due for example to ambient infrared light, can be compensated ensuring the output remains within the range of the power rails. The output of the DAis used as input to a second amplifier which acts as a low pass filter aimed to allow through signal frequencies up to 40Hz at near unit gain while attenuating higher frequencies. The front end preferably includes an accelerometer sensor, such as a 3 axis sensor based on MEMS technology and an analogue to digital converter which is used to digitise the filtered output of the DA as well as the three voltages of the 3 axis accelerometer.

The computing module comprises a central processing unit (CPU) core connected to a real time clock and flash memory. The computing unit connects to the front end module controlling the analogue to digital converter and the reading of the digitised voltages and switching on and off of the light emitting diodes. The CPU is programmed to store the digitised values as well as the real time clock information into flash memory at a regular sample period. The CPU may also perform additional calculations and data compression as it is preferably required to perform optimally. When the master unit is inductively coupled to a second type unit and can engage in communications the master unit provides the second type unit the current real time clock of the master unit such that the two units are time synchronised.

The computing module is connected to the back end module in orderto engage in communications over the near field inductive link. The back end module performs the required control and regulation of the near field communications link and the also scavenges power from the inductive link to power the ASIC and to charge a storage capacitor, which continues to provide power to the ASIC when the master unit is removed and the inductive link is broken. Preferably the back end module implements the Standard [CMA-340 Near Field Communication Interface and Protocol (NFCIP-1) 3rd edition (June 2013) using inductive coupled devices operating at the centre frequency of 13,56 MHz for interconnection of computer peripherals.

The master unit preferably comprises a smart mobile phone with integrated near field communications ability compatible with the above standard. When the master unit is in near proximity to a sensor unit near field communications can begin. The master unit will identify the type of sensor unit and will request the sensor unit to download the most recent set of data recordings. The master unit will also inform the sensor unit the real time clock value held by the master unit.

Having received waveform data from all sensor units the master unit software application processes the data as follows. Waveform data from a first type unit is analysed and the peak of the QRS waveform of the heart beat is identified and the time at which it occurred. For each identified heart beat ORS peak, the application searches the waveforms of data from all second type sensor units and identifies the time delay that occurred between the peak of the ORS and the peak of maximal absorption of 9lOnm light emitted, when the reflected infrared light was least, which corresponds to the time of maximum blood flow. The ratio of reflected GGOnm and 9lOnm is also computed as an indicator of blood oxygenation.

By requesting input from the user, the application collects spatial information indicating where each of the second type sensor units was placed, for example behind the right knee or on the right temple. Statistics are calculated for each spatial position such that an average value and standard deviation may be calculated for the time delays and ratios over several heart beats.

The application can then compare the spatial separated statistical values obtained during a measurement session with previous sessions in order to identify and display trends and to compare them against normative data, where the measuring device was used to collect normative spatial statistics for a large population of healthy control subjects as well as subjects representing groups with specific diseases. Additional data analysis may be conducted such as a variety of machine learning algorithms to classify or diagnose disease.

Claims

Claims 1. A heart activity and blood flow sensor system comprising a mobile master unit, first and second type sensor units deployed statically and spatially on points of interest on the human body, in which a first type sensor unit measures and records electro cardio voltage waveforms across one or more electrodes on the upper torso and a second type unit simultaneously measures indirectly the blood flow and blood oxygenation ratio in the sub-dermal flesh at any place on the body by recording the level of reflected injected infrared and red light absorption, where the first and second type units receive initialisation information from the master unit allowing all type sensor units to be synchronised to the same reference clock of real time and sensor units annotate all recordings with regular real time clock time stamps and transmit these recordings to the master unit for processing such that the master unit may compare all sensor unit readings as they simultaneously occurred.
2. A heart activity and blood flow sensor system as in claim 1 in which the first and second type units may receive energy inductively from a power source in the master unit.
3. A heart activity and blood flow sensor system as in claim 1 in which the first and second type units communicate bi-directionally with the master unit wirelessly using electrical induction or modulated light or radio waves.
4. A heart activity and blood flow sensor system as in claim 1, 2 and 3 in which the master unit receives recorded digitised waveform data from the sensor units and uses the time stamps on these recordings to identify the time delay between the electro cardio potential peak at the time of a heart beat measured by a first type unit and the increase in infrared light absorption recorded by a second type unit, so that this time delay may be used to infer biomarkers for a disease.
5. A heart activity and blood flow sensor system as in claim 1, 2 and 3 in which the first and second type sensor units include a component to measure the acceleration forces due to gravity and thereby infer the inclination of the human body at that point where a sensor is attached, and to annotate the recorded waveform with this inclination value.
6. A heart activity and blood flow sensor system as in claim 1, 2, 3,4 and 5 in which the master unit is a smart mobile phone with near field communication capability and where each type sensor unit includes a near field communication coil for power coupling and wireless data communication, where each sensor unit comprises a system on chip electronic device highly integrating the necessary features for computation, analogue voltage amplification and digitisation, control of the switching on and off of infrared diodes, data communication and real time clock maintenance.
7. A heart activity and blood flow sensor system as in claim 1, 2, 3,4,5 and 6 in which the smart mobile phone includes a software application which uses the data from each sensor unit to compute the time delays between heart beat and blood flow peaks and other waveform statistics and compares these with normative data from healthy subjects in order to determine any risk of disease.