Title of Invention	APPARATUS FOR NON-INVASIVELY SENSING PULSE RATE AND BLOOD FLOW ANOMALIES
Abstract	The present invention provides an apparatus and method for non-invasively sensing pulse rate and blood flow anomalies using a localized, uni-directional, and constant magnetic field. The apparatus comprises a magnetic source for producing the magnetic field, a signal acquisition module with a magnetic sensor for detecting the modulations of the magnetic field caused by the blood flow; and a signal processing module for processing the acquired signals so as to produce data of pulse rate and blood flow anomalies. The method senses pulse rate and blood flow anomalies by providing a localized, uni-directional, and constant magnetic field in proximity to a blood vessel; detecting the variations of the magnetic field caused by the flow of pulsatile blood within the blood vessel; and processing the signals of the detected variations so as to monitor the blood flow.

Title of Invention

APPARATUS FOR NON-INVASIVELY SENSING PULSE RATE AND BLOOD FLOW ANOMALIES

Abstract

The present invention provides an apparatus and method for non-invasively sensing pulse rate and blood flow anomalies using a localized, uni-directional, and constant magnetic field. The apparatus comprises a magnetic source for producing the magnetic field, a signal acquisition module with a magnetic sensor for detecting the modulations of the magnetic field caused by the blood flow; and a signal processing module for processing the acquired signals so as to produce data of pulse rate and blood flow anomalies. The method senses pulse rate and blood flow anomalies by providing a localized, uni-directional, and constant magnetic field in proximity to a blood vessel; detecting the variations of the magnetic field caused by the flow of pulsatile blood within the blood vessel; and processing the signals of the detected variations so as to monitor the blood flow.

Full Text	APPARATUS FOR NON-INVASIVELY SENSING PULSE RATE AND BLOOD FLOW ANOMALIES Field of the Invention [0001] The present invention generally relates to apparatuses for monitoring blood flows, and more particularly to an apparatus and for non-invasivcty sensing pulse rate and blood flow anomalies using a localized, uni-dircctional, and constant magnetic field [0002] With the advancement of bioelectronics, portable health monitoring devices are getting popular for they arc able to provide continuous monitoring of an individual's health condition with ease of use and comfort. The portable health monitoring devices are increasingly used at places such as home, ambulance and hospital, and at situations including military training and sports. [0003] Pulse rate and blood flow characteristics are important parameters-subject to continuous monitoring because they are important in assessing the health condition of an individual. Healthcare institutes such as the hospitals and elderly care centres can use this information to remotely monitor the health conditions of their patients. This is particular important for paraplegic patients whose blood flow anomalies need to be detected early, In addition, blood flow anomaly monitoring for patients after major surgeries is important to ensure patients smooth recovery, [0004] Furthermore, pulse rate and blood flow information of individuals subjected to crowded and cramped conditions with limited physical activity may be utilized to trigger alert for immediate attention when blood flow anomalies, such as deep vein thrombosis, are detected. Similar monitoring and alert system may also be deployed during disaster where life condition of the affected personnel can be assessed continuously for rescue risk management. Finally, it is important for monitoring of the pulse rate and blood flow of personnel working in dangerous environments such as deep sea condition (divers), high temperature (fire-fighters), and deep underground (coal miners). [0005] Current apparatuses for non-invasive measurements of blood pulse rate use electrical, mechanical and optical means for sensing. The apparatuses can come in the form of chest stripes, socks attachments, wrist-watches, and finger attachments. However, each of the apparatuses for blood pulse measurement has its weaknesses. Chest stripes and sock attachments usually measure the body electrical signals to detennino the pulse rate; it is simple but requires the use of complex algorithms and/or reference signals to reduce noise due to motion artifacts. Measurement of pulse rate by mechanical means employs the detection of pulsation on the skin, which is highly susceptible to other motion artifacts. Optical means for pulse rate measurements usually come as finger attachment device. Such device employs the use of special light sources and detectors, which normally results in higher power consumption. With the various apparatuses discussed above, it is important to note that most of these apparatuses aro not able to acquire information on blood flow. [0005] Another typo of apparatuses for measuring pulse rate and blood flow employs non-invasive electromagnetic method. For example, U.S. Pat 5,935,077 discloses an electromagnetic blood flow sensor that uses a bipolar magnetic field sourpe to provide a varying magnetic field with a component parallel to the skin and through the blood vessel, a stogle sense electrode on the skin adjacent to the blood vessel, a reference electrode, and a detector that samples tho sense electrode signal in synchronism to the varying magnetic field. However, the non-invasive electromagnetic apparatuses using electrodes to measure pulse rate and blood flow have poor signal-to-noise ratios as most of tho systems employ electrodes; tho apparatuses are more susceptible to body electrical noise and motion artifacts. In addition, most of these apparatuses employ the reversal of magnetic field polarity to achieve signal acquisition of pulse rate and blood flow information. This method usually requires the use of an olectromagnet, which will result in high power consumption. As such, tho current electromagnetic .apparatuses of pulse rate and blood flow monitoring aro not portable and are not meant for ambulatory use. Summary of the Invention [0007] Therefore, one embodiment of the present invention provides an apparatus for non-invasively monitoring of blood flow of an object including human. In the embodiment, tho apparatus comprises a magnetic source for producing a localized, uni- directional, and constant magnetic field; and a signal acquisition modulo with a magnetic sensor disposed within the magnetic field for detecting the modulations of the magnetic field caused by the blood flow; a signal conditioning module for converting the output of the signal acquisition module with appropriate amplifications; and a digital signal processing module for processing the output signal from the signal conditioning module; thereby pulse rate and blood flow anomaly can bo monitored. In another embodiment, the apparatus further comprises a display/uscrinterface/alarm module for providing visual or acoustic notification to a user. [0008] In another embodiment of the apparatus, the magnetic source is a permanent magnet. In another embodiment of the apparatus, the magnetic source is an electromagnet. In yet another embodiment of the apparatus, the strength of the magnetic field produced by the electromagnet is controlled electronically, [0009] In another embodiment of the apparatus, the magnetic source is preferably able to produce a magnetic field strength of 1000 Gauss ± 20% tolerance; wherein when the magnetic source is preferably able to produce a magnetic field strength of 1000 Gauss ± 20% tolerance, the magnetic source and magnetic sensor are separated by a distance of approximately 2.5 cm±20 %. [0010] In another embodiment of the apparatus, the magnetic sensor is- any magnetic sensor with appropriate sensitivity of detecting the modulation of the magnetic field from the magnetic source. In yet another embodiment of the apparatus, the magnetic sensor is a Giant Magneto Resistance (GMR) magnetic sensor. In yet another embodiment of the apparatus, the magnetic sensor is a Spintronics based magnetic sensor. In yet another embodiment of the apparatus, the magnetic sensor is an anisotropic maguotoresistive sensor. [0011] In another embodiment of the apparatus, the magnetic source and the1 magnetic sensor are preferably placed along the longitudinal axis of the blood vessel, in yet another embodiment of the apparatus, the magnetic source and sensor ore placed at an offset position or angle with respect to the longitudinal axis of any major blobd vessels near the surface of the skin. [0012] In another embodiment of the apparatus, the signal conditioning module comprises an amplifier for amplifying the signals received from the signal acquisition modulo,'and a signal digitization circuit for digitizing the received signals. In yet another embodiment of the apparatus, the signal conditioning modulo further comprises an optional envelope detector and/or filter using an analoguc-to-digital converter (ADC). [0013] In another embodiment of the apparatus, the signal processing module comprises a microcontroller, a microprocessor, a digital signal processor, programs to perform signal analysis, and a memory for storing all the programs and providing venues for the execution of the programs. In yet another embodiment of the apparatus, the pulse rate can bo calculated with the following equation: [0014] £0016] where n is the number of pulses detected within the time duration T (in Seconds); and T is the total time to observe n pulses, [0016] In another embodiment of the apparatus, the magnetic source further comprises a placement mechanism controlling the placement of the magnetic source in respect to the signal acquisition module and the orientation of tho blood vessel; thereby the placement of the magnetic source can be controlled. In yet another embodiment of the apparatus, the signal processing module further has the feedback capacities to control the signal for the placement mechanism and tho signal for the sensitivity of the sensor in tho signal conditioning module; in turn, the sensitivity control feedbacks to the signal acquisition modulo, and the placement mechanism feedbacks to the magnetic source to vary magnetic positions. [0017] In anothor embodiment of tho apparatus, the signal acquisition module further comprises a placement mechanism for a user to manually or automatically adjust tho position and orientation of tho magnetio sensor. In another embodiment of the apparatus, the display/userinterface/alarm modulo displays tho two measurable parameters: blood flow anomaly arid measured pulse rate. In another embodiment of the apparatus, tho display/uscrjnterfacc/alarm modulo comprises a display, an alarm, and a user interface. [0018] In another embodiment, the apparatus further comprises a wireless interface modulo to allow remote monitoring; and a base station for receiving the information from the wireless interface module, In yat another embodiment of tho apparatus, the base station comprises a data CODEC (Encoder and Decoder) and transceiver modules, display and user interface module, and microprocessor modules with RAM/ROM. [0019] Another embodiment of the present invention provides a method for non- invasively monitoring of the blood flow of an object In this embodiment, the method comprises providing a localized, uni-dircctional, and constant magnetic field in proximity to a blood vessel; detecting the variations of the magnetic field caused by the flow of pulsatile blood within the blood vessel; and processing the signals of the detected variations so as to monitor the blood flow. [0020] In another embodiment of the method, the localized, uni-directional, and constant magnetic field is provided by a magnetic source that is a permanent magnet or an electromagnet In yet another embodiment of the method, the variations of the magnetic field is detected by a signal acquisition module with a magnetic sensor. In yet another embodiment of the method, the magnetic sensor is a Spintronics based magnetic sensor or an anisotropic magnctoresistive sensor. In yet another embodiment of the method, the ' processing includes; converting the output of the signal acquisition module with appropriate amplifications by a signal conditioning module; and processing the output signal from the signal conditioning modulo to measure pulse rate and detect blood flow anomaly by a digital signal processing module. [0021] In another embodiment of the method, the signal processing module comprises a microcontroller, a microprocessor, a digital signal processor, programs to perform signal analysis, and a memory for storing all the programs and providing venues for the execution of the programs. In yet another embodiment of the method, the pulse rate can be calculated with the following equation: [0022J [0023] where n is the number of pulses detected within the time duration T (in seconds); and T is the total time to observe n pulses. [0024] In another embodiment of the method, the signal processing module detects the time interval between two adjacent pulses so as to measure and display physiological anomalies. In yet another embodiment of the method, the physiological anomalies include cardiac arrhythmia and on-set of heart failures. [0025] One advantage of the present invention is that using magnetic field sensing to acquire the Modulated Magnetic Signature of Blood (MMSB) provides electrical isolation and is therefore less susceptible to body bioelectrical noise such as bioelcctrical noiso from the heart, brain and voluntary and involuntary motion artifacts. [0026] Another advantage of tho present invention is that it docs not need to have direct physical contact of the magnetic source and/or signal acquisition module with tho skin, For example, thore could be fabric, perspiration and oil secretion between them. These do not in any way affect the quality of signal being acquired or measured. Another advantage of tho present invention is that the use of a localised constant unidirectional magnetic field allows tho employment of a permanent magnet. This will greatly reduce power consumption of the system making it feasible for deployment as a portable device. [0027] Another advantage of tho present invention is that the apparatus docs not require a reference potential or signal such as tho electrocardiogram (ECG). Another, advantage of the present invention is that the apparatus can bo designed and developed to automatically or manually optimize the data acquisition process by varying the strength of the magnetic field or the sensitivity of tho sensor, [0028] The objectives and advantages of the invention will become apparent from the following detailed description of preferred embodiments thereof in connection with the accompanying drawings. Brief Description of the Drawings [0029] Preferred embodiments according to the present invention will now be described with reference to the Figures, in which like reference numerals denote like elements. [0030] t FIG 1 is a functional block diagram of tho non-invasive magnetic apparatus for sensing pulse rate and blood flow in an object in accordance with one embodiment of the present invention. [0031] FIG 1a shows a non-direct contact configuration for sensing pulse rate and blood flow using tho non-invasive magnetio apparatus as shown in FIG 1. [0032] FIG 2 shows exemplary schematic electronic circuits for the Signal Acquisition Modulo and the Signal Conditioning Modulo as shown in FIG 1 in accordance with one embodiment of the present invention. [0033] PIG 3 is a functional block diagram of the non-invasivo magnetic apparatus for sensing pulse rato and blood flow in accordance with another embodiment of tho present invention, [0034] FIG 4 is n graphic illustration of resistance change with respect to magnetic field applied. [0035] FIG 5 shows a typical digitized signal acquired with normal blood flow on the wrist. [0036] FIG 6 shows a typical digitized signal acquired with restricted blood flow on the wrist [0037] FIG 7 shows a typical digitized signal acquired with normal blood flow on the heel at a more refined resolution. [0030] FIG 8 shows a typical digitized signal acquired with restricted blood flow on tho heel at a more refined resolution. [0039] FIG 9a illustrates the working principle of a Spintronics based magnetic sensor with no external magnetic field, [0040] FIG 9b illustrates the working principle of a Spintronics based magnetic sensor with external magnetic field. [0041] FIG 10 is a flowchart of the method of sensing pulse rate and blood flow anomalies in accordance with one embodiment of tho present invention. [0042] FIG 11 shows a top view of hand with the non-invasivo magnetic apparatus in accordance with one embodiment of the present invention. [0043] FIG 12 shows a side view of hand with tho non-invasivc magnetic apparatus in accordance with one embodiment of tho present invention. [0044] FIG 13 shows a cross-section view of hand with tho non-invasivo magnetic apparatus in accordance with one embodiment of tho present invention. Detailed Description of tho Invention [0045] The present invention may bo understood more readily by reference to tho following detailed description of certain embodiments of tho invention. [0046] Throughout this application, whore publications are referenced, the disclosures of these publications are hereby incorporated by reference, in their entireties, into this application in order to more fully describe the state of art to which this invention pertains. [0047] In the following detailed description, specific details are set forth in order to provide a thorough understanding of the invention. However, it will bo understood by those skilled in the relevant art that the present invention may bo practiced without these specific details. In other instances, well-known methods, procedures, components, and materials have not been described in detail so as not to obscure the present invention. [0048] The present invention provides an apparatus and method for non-invasively sensing pulse rate and blood flow in an object including human. The present invention is originated from the inventors discovery that when a localized, uni-directional, and constant magnetic field is applied to a blood vessel, tno flow of pulsatile blood can modulate the applied magnetic field and that the modulation of the magnetic field can bo sensed directly if a magnetic sensor is disposed in a suitable position within the magnetic field. Of principle, the apparatus comprises a magnotio source for providing the magnetic field, a magnetic sensor for acquiring the signals of modulation, and a signal processing/displaying subunit for processing and outputting the processed signal. The processed signals, named modulated magnetic signature of blood (MMSB), arc a function of the strength of tho magnetic source, the sensitivity of tho sensor, the distance between them, and their relative placement and orientation with respect to a major blood vessel near tho surface of the skin. While tho following description will use specific configurations and dimensions and modules to illustrate tho principles of tho present invention, it by no means intends to limit the practice of tho present invention to those specifics. [0049] Now referring to PIG 1, there is provided a functional block diagram of the non-invasive magnetic apparatus for sensing pulse rate and blood flow in an object in accordance with one embodiment of the present invention. The non-invasive magnetic apparatus 10 comprises a magnetic source 1, a signal acquisition module 2, and a signal processing/displaying subunit 6 including a signal conditioning modulo 3, a signal processing module 4, and a display/userinterface/alarm module 5. Briefly, a permanent magnet is shown in FIG 1 to illustrate the magnetic field distribution near an artery and the signal acquisition modulo, Tho flow of pulsatile blood in the artery modulates the applied magnetic field to create a modulated magnetic signature of blood flow (MMSB). The MMSB is translated by the signal acquisition modulo to an electrical signal, which is then conditioned and digitized for signal processing. Then; the processed signal, primarily the pulse rate and blood flow profile, will be sent to the display/uscrinterface/olann module. [0050] The magnetic source 1 provides a localized, uni-dircctional, and constant magnetic field that is close to a major blood vessel. As discussed above, the flow of pulsatile blood modulates the applied magnetic field to produce a modulated magnetic signature of the blood flow (MMSB). The magnetic source 1 may comprise a permanent magnet, an electromagnet (including coil of wiro, coil of wiro on a ferromagnetic material, or coil of wiro on a magnet), or the like as long as a constant magnctio field can be generated. The magnetic source may optionally further comprise a slider and control interface so as to control the position of the magnetic source within the apparatus. In addition, tho magnetic source 1 may come in various geometry and sizes. As discussed hereinafter, a magnetic source may produce a magnetic field strength of 1000 Gauss ± 20 % tolerance; that was used for tho inventors experiments. It is to be notod that the magnetic source may be of other magnetic field strength where tho related parameters (e.g., tho sensitivity of tho sensor, the distance between the magnetic source and sensor, and the relative placement and orientation of the magnetic source and sensor with respect to a blood vessel) will have to be modified with appropriate support from experimental results. [0051] The signal acquisition module 2 comprises a magnetic sensor that is able to translate magnetic variations to voltages proportional to the variations of the magnetic signature. The magnetic sensors suitable for tho present invention include, but are not limited to, spintronics. based sensors (e,g. giant magnctorcsistive (GMR) sensor and tunneling magnetoresistivc (TMR) sensor), anisotropic magnctorcsistive (AMR) sensors and any magnetic based sensors. One exemplary magnetic sensor is a Spintronics based magnetic sensor (e.g., AAH002-02 manufactured by NVE Corporation). It is to bo noted that other magnetic-based sensors, with different sensitivities may also be used to detect tho modulated magnetic signature of blood flow (MMSB), but the related parameters (e.g., the strength of the magnetic source, the distance between the magnetic source and sensor, and tho relative placement and orientation of the raagnetio source and sensor: with respect to a blood vessel) will have to bo modified with appropriate support from experimental results. [0052] Magnetic sensors are well known in the art. Their working principles will only be briefly described herein. Such sensors change their resistances based on the magnetic field applied. FIGs 9a and 9b show a graphic illustration of the working principle behind the GMR magnetic sensors. As shown in FIG 9a, a conductive, nonmagnetic interlayer A is sandwiched by two-alloy layers B; when no external magnetic field is applied, the magnetic moments in the alloy layers face opposite directions (represented by the arrows), and the resistance to current C is high. As shown in FIG 9b, when an external magnetic field D is applied, applied external magnetic field overcomes: anti-ferromagnetic coupling, aligning magnetic moments in alloy layers, and the electrical resistance drops dramatically; 10% to 15% is typical. The magnetic signal variation is translated to a corresponding change of resistance in the GMR sonsor device. This change of resistance with magnetic field applied can be illustrated as shown in HG 4. To those skilled in the art, the curve shows a change of resistance that can be correlated to minute variations in magnetic field. [0053] Now referring to FIG 2, there is provided an exemplary schematic electronic circuit for the signal acquisition module 2 in accordance with one embodiment of the present invention. The circuit of the signal acquisition module 2 is so configured that a direct current (DC) power supply such as a battery to create a potential across the Wheatstone-Bridge connected to the GMR sensor. Coupled with the use of a Whcatstonc- Bfidge, the change in resistance due to the minute variations in the magnetic field can, be translated into a measurable potential To those skilled in the art, the potential applied across Y+ and V- will result in a measured output across OUT+ and OUT- Tho changes in resistance due to the applied magnetic field will then bo linearly translated to a differential potential change across OUT+ and OUT-. Acquiring and measuring this differential potential will allow the magnetic field variations duo to MMSB to bo quantified and processed for measuring pulse rates and detecting blood flow anomalies. [0054] With tho application of a localised, unidirectional, and constant magnetic source, tho measurable range of the Spintronics based magnetic sensor is shifted as shown in FIG 4. To those skilled in tho art, this will provide better linearity for the sensor to detect the minute changes of magnelio field generated from tho modulated magnetic signature of blood (MMSB). [0055] For optimized measurement of pulse rates and detection of blood flow anomalies by the apparatus, the factors other than the strength of the magnetic source and the sensitivity of tho magnetic sensor need to be considered. First is the placement and orientation of the magnetic source with respect to a blood vessel. Tho magnetic source 1 may Be preferably placed along the longitudinal axis of the blood vessel at an appropriate proximity that will generate a signal which can be detected by the magnetic senior,. In addition, the magnetic source may also be placed at an offset position or angle with respect to the longitudinal axis of any major blood vessels near the surface of the skin. If so, then other parameters including tho strength of the magnetic source, the sensitivity of the sensor, and tho distance between the magnetic source and sensor will have to be modified with appropriate support from experimental results. Second is the distance between the magnetic source and sensor. The distance is affected by many factors including the strength of the magnetic source. For example, when the magnetic source is about 1000 Gauss, the distance between tho magnetic source and sensor is about 2.5 cm ± 20 %. When the magnetic source produces a magnetic field with different strengths, it is easy for those skilled in the art to determine the proper range within which the magnetic sensor can be disposed without undue experimentation. [005G1 The magnetic source and magnetic sensor can sense tho pulse rate and blood flow in a non-direct contact configuration. As shown in FIG la, ono space gap 7 may exist between the magnetic source/sensor and the skin. For example, the space gap could be fabric, perspiration and oil secretion between them. The thickness of tho space gap can be easily determined in consideration of tho strength of the magnetic source, the sensitivity of the magnetic sensor, and the material used in tho space gap. [0057] Now referring back to HG 1, tho signal conditioning modulo 3 converts tho differential-ended output of tho signal acquisition module 2 into a single-ended signal with appropriate amplifications. In ono embodiment, tho signal conditioning modulo 3 comprises an amplifier for amplifying the signals received from the signal acquisition , modulo, anda signal digitization circuit for digitizing tho received signals. FIG 2 shows an exemplary schematic circuit of the signal conditioning modulo 3. The suitable circuits aro well known in tho art. As shown in FIG 2, an optional envelope detector and/or filter is proposed before digitization of tho signal using an analoguc-to-digital converter (ADC). To those skilled in the art, this will allow them to implement analogue signal selection before digitization, [0058] Now referring to FIG 1 and FIG 2, tho digital signal processing modulo 4 proccssos tho digital signals from the signal conditioning modulo 3 to measure the pulso rate and detect blood flow anomaly, In one embodiment, the signal processing module 4 comprises a microcontroller, a microprocessor, a digital signal processor, programs to perform signal analysis, and a memory for storing oll the programs and providing venues for the execution of the programs. The result output /display module 5 displays the two measurable parameters-blood flow anomaly and measured pulse rate-obtained from the digital signal processing modulo 4 m cither discrete (LED) or continuous form (LCD), In one embodiment, the result output/display module 5 comprises a display, an alarm, and a user interface, [0050] The outputs may take different forms. For example, the outputs may be an alarm notification if any anomalies are detected. The pulse rates may be expressed as pulses per minute. The outputs may also bo digital data with computed pulse rates. Typical digital data are shown in FIG 5 and FIG 6 for normal and abnormal blood flow condition respectively. Typical digital data are shown an FIG 7 and FIG S (at a more refined resolution) for normal and abnormal blood flow condition respectively. The calculation of pulse rates from the digital data will bo discussed hereinafter. [0060] Now referring to FIG 3, there is provided a functional block diagram of the non-invasivo magnetic apparatus that is able to automate signal acquisition to achieve optimal signal level. As shown in FIG 3, the signal processing module 4 now has the feedback capacities to control the sensitivity of the sensor and placement mechanism such as a slider in the signal conditioning module, The placement mechanism enables a user to manually or automatically adjust the position and orientation of the magnetic source. In turn, tho sensitivity control feedbacks to the signal acquisition module, and the slider control feedbacks to tho magnetic source to vary magnetic positions. While not shown in FIG 3, the signal acquisition modulo may further comprises a placement mechanism enabling a user to manually or automatically adjust tho position and orientation of the magnetic sensor. In addition, while not shown in FIG 3, the magnetic source may further comprise a strength adjustment mechanism when the electromagnet is used as tho magnetic source. Tho devices for controlling position and orientation of the magnetic source and sensor and for controlling the strength of the magnetic source arc well known to those in the arts; any suitable devices may be used in the present invention. [0061] Still referring to FIG 3, tho apparatus further comprises a wireless interface modulo 8 to allow remote monitoring. Tho base station 9 may be incorporated into the apparatus or employed in a separate location for receiving the information from tho apparatus. The base station comprises a data CODEC (Encoder and Decoder) and transceiver modules, display and user interface module, and microprocessor modules with HAM/ROM. The wireless transmission is well known in the art, thus no details will be provided herein. [0062] Now referring to FIG 10, there is provided a flow chart of the method for sensing the pulse rato and blood flow anomalies using a localized, uni-dircctional, and constant magnetic field. [0063J The method 100 starts with placing directly or in proximity to the skin the apparatus for non-invasively sensing pulse rato and blood flow using the localized, uni- directional, and constant magnetic field 110, The magnetic source and sensor of the apparatus is preferably disposed along the longitudinal axis of a major blood vessel such as, but not limited to, the ones found on the wrist, leg, or heel. [0064] Then, the sensor is then connected to a direct current (DC) power supply 120 such as a battery to create a potential across the Whcatstone-Bridgo connected to the GMR. sensor. For example, when the sensor used is the NVB AAH002-02, the potential applied is a DC voltage supply of 9V. Then, the signal acquisition module outputs the differential outputs, OUT+ and OUT-130. [00065] Then, the output signals from the signal acquisition modulo are amplified by the signal conditioning module before any analogue signal conditioning (optional) 140, To those skilled in the art, such a configuration will ensure signal integrity. The analogue signal will then be digitised by tho analogue-to-digital converter (ADC), [0066] Then, the conditioned output signals from the signal conditioning module are processed by the signal processing module to measure tho pulse rate and detect blood flow anomalies 150. Now referring to FIG 5, there is provided a typical digital data acquired with normal blood flow on the wrist The pulse rate can bo calculated with the following equation; where n is the number of pulses detected within the time duration T (in seconds); a is the time interval between two adjacent pulses as shown in FIG 5; and T is the total time to observe n pulses in seconds. Tho measurable parameter a can be used for tho observation of heart beat anomaly such as the presence of a chaotic pattern which could signify the on set of a heart attack or cardiac arrhythmia, [0067] Then, the outputs from the signal processing module include pulse rate and blood flow anomalies. The outputs will be displayed 160 on the result output /display module. [0068] The apparatus and method of the present invention is applicable to many situations. For example, hospitals can use the apparatus for monitoring patients; athletes . can use the apparatus for monitoring their blood flow; elders can be monitored remotely with the wireless apparatus; blood flow anomalies can be detected in different circumstances such as long flight, rescues, and dangerous situations. [0069] FIGS 11-13 shows the placement and configuration of the non-invasive magnetic apparatus in accordance with one embodiment of the present invention. The magnetic source 1 and magnetic signal acquisition module % are placed along the longitudinal axis of the blood vessel on the wrist In this design, the apparatus can be ' incorporated into any wrist wearing devices or decors. Of course, the apparatus can be used in other parts of a body and incorporated into other devices, [0070] While the present invention has been described with reference to particular embodiments, it will be understood that the embodiments are illustrative and that the invention scope is not so limited. Alternative embodiments of the present invention will become apparent to those having ordinary skill in the art to which the present invention pertains. Such alternate embodiments are considered to be encompassed within the spirit and scope of the present invention. Accordingly, the scope of the present invention is described by the appended claims and is supported by the foregoing description. We Claim: 1. An apparatus for non-invasively monitoring of blood flow of a living subject, comprising: a magnetic source for producing a localized, uni-directional, and constant magnetic field; and a signal acquisition module with a magnetic sensor, wherein the magnetic sensor is disposed within the magnetic field and detects the modulations of the localized, uni- directional, and constant magnetic field effected by the blood flow passing through the magnetic field in a blood vessel near the skin surface of the living subject; a signal conditioning module for converting the output of the signal acquisition module with appropriate amplifications; and a digital signal processing module Tor processing the output signal from the signal conditioning module; thereby pulse rate and blood flow anomaly can be monitored. 2. The apparatus as claimed in claim 1, further comprising a notification module for providing visual or acoustic notification to a user. 3. The apparatus as claimed in claim 1, wherein the magnetic source is a permanent magnet. 4. The apparatus as claimed in claim 1, wherein the magnetic source is an electromagnet. 5. The apparatus as claimed in claim 4, wherein the strength of the magnetic field produced by the electromagnet is controlled electronically, 6. The apparatus as claimed in claim 1, wherein the magnetic source is preferably able to produce a magnetic field strength of 1000 Gauss + 20% tolerance. 7. The apparatus as claimed in claim 6, wherein when the magnetic source is preferably able to produce a magnetic field strength of 1000 Gauss + 20% tolerance, the magnetic source and magnetic sensor are separated by a distance of approximately 2.5 cm + 20 %, 8. The apparatus as claimed in claim 1, wherein the magnetic sensor is any magnetic sensor with appropriate sensitivity of detecting the modulation of the magnetic field from the magnetic source. 9. The apparatus as claimed in claim 8, wherein the magnetic sensor is a Giant Magneto Resistance (GMR) magnetic sensor. 10. The apparatus as claimed in claim 8, wherein the magnetic sensor is a Spintronics based magnetic sensor. 11. The apparatus as claimed in claim 8, wherein the magnetic sensor is an anisotropic magnctorcsistivc sensor. 12. The apparatus as claimed in claim 1, wherein the magnetic source and the magnetic sensor are placed along the longitudinal axis of the blood vessel, 13. The apparatus as claimed in claim 1, wherein the magnetic source and sensor arc placed at an offset position or angle with respect to the longitudinal axis of the blood vessel. 14. The apparatus as claimed in claim 1, wherein the signal conditioning module comprises an amplifier for amplifying the signals received from the signal acquisition module, and a signal digitization circuit for digitizing the received signals. 15. The apparatus as claimed in claim 14, wherein the signal conditioning module further comprises an envelope detector and/or filter using an analogue-to-digital converter (ADC). 16. The apparatus as claimed in claim 1, wherein the signal processing module comprises a microcontroller, a microprocessor, a digital signal processor, programs to perform signal analysis, and a memory for storing all the programs and providing venues for the execution of the programs. 17. The apparatus as claimed in claim 16, wherein the microprocessor calculates the pulse rate with the following equation: where n is the number of pulses detected within the time duration T (in seconds); and T is the total time to observe n pulses. 18. The apparatus as claimed in claim 1, wherein the magnetic source further comprises a placement mechanism controlling the placement of the magnetic source in respect to the signal acquisition module and the orientation of the blood vessel; thereby the placement of the magnetic source can be controlled. 19. The apparatus as claimed in claim 18, wherein the signal processing module further has the feedback capacities to control the signal for the placement mechanism and the signal for a sensitivity control for sensor in the signal conditioning module; in turn, the sensitivity control feedbacks to the signal acquisition module to control the sensitivity of the magnetic sensor, and the signal for the placement mechanism feedbacks to the magnetic source to vary magnetic positions, 20. The apparatus as claimed in claim 1, wherein the signal acquisition module further comprises a placement mechanism for a user to manually or automatically adjust the position and orientation of the magnetic sensor. 21. The apparatus as claimed in claim 2, wherein the notification module displays the two measurable parameters: blood flow anomaly and measured pulse rate. 22. The apparatus as claimed in claim 2, wherein the notification module comprises a display, an alarm, and a user interface, 23. The apparatus as claimed in claim 1, further comprising: a wireless interface module to allow remote monitoring the pulse rate and blood flow anomaly; and a base station for receiving the information from the wireless interface module. 24. The apparatus as claimed in claim 23, wherein the base station comprises a data CODEC (Encoder and Decoder) and transceiver modules, display and user interface module, and microprocessor modules with RAM/ROM. The present invention provides an apparatus and method for non-invasively sensing pulse rate and blood flow anomalies using a localized, uni-directional, and constant magnetic field. The apparatus comprises a magnetic source for producing the magnetic field, a signal acquisition module with a magnetic sensor for detecting the modulations of the magnetic field caused by the blood flow; and a signal processing module for processing the acquired signals so as to produce data of pulse rate and blood flow anomalies. The method senses pulse rate and blood flow anomalies by providing a localized, uni-directional, and constant magnetic field in proximity to a blood vessel; detecting the variations of the magnetic field caused by the flow of pulsatile blood within the blood vessel; and processing the signals of the detected variations so as to monitor the blood flow.

Full Text

APPARATUS FOR NON-INVASIVELY SENSING PULSE RATE AND BLOOD
FLOW ANOMALIES
Field of the Invention
[0001] The present invention generally relates to apparatuses for monitoring blood flows,
and more particularly to an apparatus and for non-invasivcty sensing pulse rate and blood flow
anomalies using a localized, uni-dircctional, and constant magnetic field
[0002] With the advancement of bioelectronics, portable health monitoring devices
are getting popular for they arc able to provide continuous monitoring of an individual's
health condition with ease of use and comfort. The portable health monitoring devices are
increasingly used at places such as home, ambulance and hospital, and at situations
including military training and sports.
[0003] Pulse rate and blood flow characteristics are important parameters-subject to
continuous monitoring because they are important in assessing the health condition of an
individual. Healthcare institutes such as the hospitals and elderly care centres can use this
information to remotely monitor the health conditions of their patients. This is particular
important for paraplegic patients whose blood flow anomalies need to be detected early, In
addition, blood flow anomaly monitoring for patients after major surgeries is important to
ensure patients smooth recovery,
[0004] Furthermore, pulse rate and blood flow information of individuals subjected
to crowded and cramped conditions with limited physical activity may be utilized to trigger
alert for immediate attention when blood flow anomalies, such as deep vein thrombosis,
are detected. Similar monitoring and alert system may also be deployed during disaster
where life condition of the affected personnel can be assessed continuously for rescue risk
management. Finally, it is important for monitoring of the pulse rate and blood flow of
personnel working in dangerous environments such as deep sea condition (divers), high
temperature (fire-fighters), and deep underground (coal miners).

[0005] Current apparatuses for non-invasive measurements of blood pulse rate use
electrical, mechanical and optical means for sensing. The apparatuses can come in the
form of chest stripes, socks attachments, wrist-watches, and finger attachments. However,
each of the apparatuses for blood pulse measurement has its weaknesses. Chest stripes and
sock attachments usually measure the body electrical signals to detennino the pulse rate; it
is simple but requires the use of complex algorithms and/or reference signals to reduce
noise due to motion artifacts. Measurement of pulse rate by mechanical means employs
the detection of pulsation on the skin, which is highly susceptible to other motion artifacts.
Optical means for pulse rate measurements usually come as finger attachment device.
Such device employs the use of special light sources and detectors, which normally results
in higher power consumption. With the various apparatuses discussed above, it is important
to note that most of these apparatuses aro not able to acquire information on blood flow.
[0005] Another typo of apparatuses for measuring pulse rate and blood flow
employs non-invasive electromagnetic method. For example, U.S. Pat 5,935,077 discloses
an electromagnetic blood flow sensor that uses a bipolar magnetic field sourpe to provide a
varying magnetic field with a component parallel to the skin and through the blood vessel,
a stogle sense electrode on the skin adjacent to the blood vessel, a reference electrode, and
a detector that samples tho sense electrode signal in synchronism to the varying magnetic
field. However, the non-invasive electromagnetic apparatuses using electrodes to measure
pulse rate and blood flow have poor signal-to-noise ratios as most of tho systems employ
electrodes; tho apparatuses are more susceptible to body electrical noise and motion
artifacts. In addition, most of these apparatuses employ the reversal of magnetic field
polarity to achieve signal acquisition of pulse rate and blood flow information. This
method usually requires the use of an olectromagnet, which will result in high power
consumption. As such, tho current electromagnetic .apparatuses of pulse rate and blood
flow monitoring aro not portable and are not meant for ambulatory use.
Summary of the Invention
[0007] Therefore, one embodiment of the present invention provides an apparatus
for non-invasively monitoring of blood flow of an object including human. In the
embodiment, tho apparatus comprises a magnetic source for producing a localized, uni-

directional, and constant magnetic field; and a signal acquisition modulo with a magnetic
sensor disposed within the magnetic field for detecting the modulations of the magnetic
field caused by the blood flow; a signal conditioning module for converting the output of
the signal acquisition module with appropriate amplifications; and a digital signal
processing module for processing the output signal from the signal conditioning module;
thereby pulse rate and blood flow anomaly can bo monitored. In another embodiment, the
apparatus further comprises a display/uscrinterface/alarm module for providing visual or
acoustic notification to a user.
[0008] In another embodiment of the apparatus, the magnetic source is a permanent
magnet. In another embodiment of the apparatus, the magnetic source is an electromagnet.
In yet another embodiment of the apparatus, the strength of the magnetic field produced by
the electromagnet is controlled electronically,
[0009] In another embodiment of the apparatus, the magnetic source is preferably
able to produce a magnetic field strength of 1000 Gauss ± 20% tolerance; wherein when
the magnetic source is preferably able to produce a magnetic field strength of 1000 Gauss
± 20% tolerance, the magnetic source and magnetic sensor are separated by a distance of
approximately 2.5 cm±20 %.
[0010] In another embodiment of the apparatus, the magnetic sensor is- any
magnetic sensor with appropriate sensitivity of detecting the modulation of the magnetic
field from the magnetic source. In yet another embodiment of the apparatus, the magnetic
sensor is a Giant Magneto Resistance (GMR) magnetic sensor. In yet another embodiment
of the apparatus, the magnetic sensor is a Spintronics based magnetic sensor. In yet
another embodiment of the apparatus, the magnetic sensor is an anisotropic
maguotoresistive sensor.
[0011] In another embodiment of the apparatus, the magnetic source and the1
magnetic sensor are preferably placed along the longitudinal axis of the blood vessel, in
yet another embodiment of the apparatus, the magnetic source and sensor ore placed at an
offset position or angle with respect to the longitudinal axis of any major blobd vessels
near the surface of the skin.
[0012] In another embodiment of the apparatus, the signal conditioning module
comprises an amplifier for amplifying the signals received from the signal acquisition
modulo,'and a signal digitization circuit for digitizing the received signals. In yet another

embodiment of the apparatus, the signal conditioning modulo further comprises an optional
envelope detector and/or filter using an analoguc-to-digital converter (ADC).
[0013] In another embodiment of the apparatus, the signal processing module
comprises a microcontroller, a microprocessor, a digital signal processor, programs to
perform signal analysis, and a memory for storing all the programs and providing venues
for the execution of the programs. In yet another embodiment of the apparatus, the pulse
rate can bo calculated with the following equation:
[0014]
£0016] where n is the number of pulses detected within the time duration T (in
Seconds); and T is the total time to observe n pulses,
[0016] In another embodiment of the apparatus, the magnetic source further
comprises a placement mechanism controlling the placement of the magnetic source in
respect to the signal acquisition module and the orientation of tho blood vessel; thereby the
placement of the magnetic source can be controlled. In yet another embodiment of the
apparatus, the signal processing module further has the feedback capacities to control the
signal for the placement mechanism and tho signal for the sensitivity of the sensor in tho
signal conditioning module; in turn, the sensitivity control feedbacks to the signal
acquisition modulo, and the placement mechanism feedbacks to the magnetic source to
vary magnetic positions.
[0017] In anothor embodiment of tho apparatus, the signal acquisition module
further comprises a placement mechanism for a user to manually or automatically adjust
tho position and orientation of tho magnetio sensor. In another embodiment of the
apparatus, the display/userinterface/alarm modulo displays tho two measurable parameters:
blood flow anomaly arid measured pulse rate. In another embodiment of the apparatus, tho
display/uscrjnterfacc/alarm modulo comprises a display, an alarm, and a user interface.
[0018] In another embodiment, the apparatus further comprises a wireless interface
modulo to allow remote monitoring; and a base station for receiving the information from
the wireless interface module, In yat another embodiment of tho apparatus, the base station
comprises a data CODEC (Encoder and Decoder) and transceiver modules, display and
user interface module, and microprocessor modules with RAM/ROM.

[0019] Another embodiment of the present invention provides a method for non-
invasively monitoring of the blood flow of an object In this embodiment, the method
comprises providing a localized, uni-dircctional, and constant magnetic field in proximity
to a blood vessel; detecting the variations of the magnetic field caused by the flow of
pulsatile blood within the blood vessel; and processing the signals of the detected
variations so as to monitor the blood flow.
[0020] In another embodiment of the method, the localized, uni-directional, and
constant magnetic field is provided by a magnetic source that is a permanent magnet or an
electromagnet In yet another embodiment of the method, the variations of the magnetic
field is detected by a signal acquisition module with a magnetic sensor. In yet another
embodiment of the method, the magnetic sensor is a Spintronics based magnetic sensor or
an anisotropic magnctoresistive sensor. In yet another embodiment of the method, the '
processing includes; converting the output of the signal acquisition module with
appropriate amplifications by a signal conditioning module; and processing the output
signal from the signal conditioning modulo to measure pulse rate and detect blood flow
anomaly by a digital signal processing module.
[0021] In another embodiment of the method, the signal processing module
comprises a microcontroller, a microprocessor, a digital signal processor, programs to
perform signal analysis, and a memory for storing all the programs and providing venues
for the execution of the programs. In yet another embodiment of the method, the pulse
rate can be calculated with the following equation:
[0022J
[0023] where n is the number of pulses detected within the time duration T (in
seconds); and T is the total time to observe n pulses.
[0024] In another embodiment of the method, the signal processing module detects
the time interval between two adjacent pulses so as to measure and display physiological
anomalies. In yet another embodiment of the method, the physiological anomalies include
cardiac arrhythmia and on-set of heart failures.
[0025] One advantage of the present invention is that using magnetic field sensing
to acquire the Modulated Magnetic Signature of Blood (MMSB) provides electrical

isolation and is therefore less susceptible to body bioelectrical noise such as bioelcctrical
noiso from the heart, brain and voluntary and involuntary motion artifacts.
[0026] Another advantage of tho present invention is that it docs not need to have
direct physical contact of the magnetic source and/or signal acquisition module with tho
skin, For example, thore could be fabric, perspiration and oil secretion between them.
These do not in any way affect the quality of signal being acquired or measured. Another
advantage of tho present invention is that the use of a localised constant unidirectional
magnetic field allows tho employment of a permanent magnet. This will greatly reduce
power consumption of the system making it feasible for deployment as a portable device.
[0027] Another advantage of tho present invention is that the apparatus docs not
require a reference potential or signal such as tho electrocardiogram (ECG). Another,
advantage of the present invention is that the apparatus can bo designed and developed to
automatically or manually optimize the data acquisition process by varying the strength of
the magnetic field or the sensitivity of tho sensor,
[0028] The objectives and advantages of the invention will become apparent from
the following detailed description of preferred embodiments thereof in connection with the
accompanying drawings.
Brief Description of the Drawings
[0029] Preferred embodiments according to the present invention will now be
described with reference to the Figures, in which like reference numerals denote like
elements.
[0030] t FIG 1 is a functional block diagram of tho non-invasive magnetic apparatus
for sensing pulse rate and blood flow in an object in accordance with one embodiment of
the present invention.
[0031] FIG 1a shows a non-direct contact configuration for sensing pulse rate and
blood flow using tho non-invasive magnetio apparatus as shown in FIG 1.
[0032] FIG 2 shows exemplary schematic electronic circuits for the Signal
Acquisition Modulo and the Signal Conditioning Modulo as shown in FIG 1 in accordance
with one embodiment of the present invention.

[0033] PIG 3 is a functional block diagram of the non-invasivo magnetic apparatus
for sensing pulse rato and blood flow in accordance with another embodiment of tho
present invention,
[0034] FIG 4 is n graphic illustration of resistance change with respect to magnetic
field applied.
[0035] FIG 5 shows a typical digitized signal acquired with normal blood flow on
the wrist.
[0036] FIG 6 shows a typical digitized signal acquired with restricted blood flow
on the wrist
[0037] FIG 7 shows a typical digitized signal acquired with normal blood flow on
the heel at a more refined resolution.
[0030] FIG 8 shows a typical digitized signal acquired with restricted blood flow
on tho heel at a more refined resolution.
[0039] FIG 9a illustrates the working principle of a Spintronics based magnetic
sensor with no external magnetic field,
[0040] FIG 9b illustrates the working principle of a Spintronics based magnetic
sensor with external magnetic field.
[0041] FIG 10 is a flowchart of the method of sensing pulse rate and blood flow
anomalies in accordance with one embodiment of tho present invention.
[0042] FIG 11 shows a top view of hand with the non-invasivo magnetic apparatus
in accordance with one embodiment of the present invention.
[0043] FIG 12 shows a side view of hand with tho non-invasivc magnetic apparatus
in accordance with one embodiment of tho present invention.
[0044] FIG 13 shows a cross-section view of hand with tho non-invasivo magnetic
apparatus in accordance with one embodiment of tho present invention.
Detailed Description of tho Invention
[0045] The present invention may bo understood more readily by reference to tho
following detailed description of certain embodiments of tho invention.
[0046] Throughout this application, whore publications are referenced, the
disclosures of these publications are hereby incorporated by reference, in their entireties,

into this application in order to more fully describe the state of art to which this invention
pertains.
[0047] In the following detailed description, specific details are set forth in order to
provide a thorough understanding of the invention. However, it will bo understood by
those skilled in the relevant art that the present invention may bo practiced without these
specific details. In other instances, well-known methods, procedures, components, and
materials have not been described in detail so as not to obscure the present invention.
[0048] The present invention provides an apparatus and method for non-invasively
sensing pulse rate and blood flow in an object including human. The present invention is
originated from the inventors discovery that when a localized, uni-directional, and
constant magnetic field is applied to a blood vessel, tno flow of pulsatile blood can
modulate the applied magnetic field and that the modulation of the magnetic field can bo
sensed directly if a magnetic sensor is disposed in a suitable position within the magnetic
field. Of principle, the apparatus comprises a magnotio source for providing the magnetic
field, a magnetic sensor for acquiring the signals of modulation, and a signal
processing/displaying subunit for processing and outputting the processed signal. The
processed signals, named modulated magnetic signature of blood (MMSB), arc a function
of the strength of tho magnetic source, the sensitivity of tho sensor, the distance between
them, and their relative placement and orientation with respect to a major blood vessel near
tho surface of the skin. While tho following description will use specific configurations
and dimensions and modules to illustrate tho principles of tho present invention, it by no
means intends to limit the practice of tho present invention to those specifics.
[0049] Now referring to PIG 1, there is provided a functional block diagram of the
non-invasive magnetic apparatus for sensing pulse rate and blood flow in an object in
accordance with one embodiment of the present invention. The non-invasive magnetic
apparatus 10 comprises a magnetic source 1, a signal acquisition module 2, and a signal
processing/displaying subunit 6 including a signal conditioning modulo 3, a signal
processing module 4, and a display/userinterface/alarm module 5. Briefly, a permanent
magnet is shown in FIG 1 to illustrate the magnetic field distribution near an artery and the
signal acquisition modulo, Tho flow of pulsatile blood in the artery modulates the applied
magnetic field to create a modulated magnetic signature of blood flow (MMSB). The
MMSB is translated by the signal acquisition modulo to an electrical signal, which is then

conditioned and digitized for signal processing. Then; the processed signal, primarily the
pulse rate and blood flow profile, will be sent to the display/uscrinterface/olann module.
[0050] The magnetic source 1 provides a localized, uni-dircctional, and constant
magnetic field that is close to a major blood vessel. As discussed above, the flow of
pulsatile blood modulates the applied magnetic field to produce a modulated magnetic
signature of the blood flow (MMSB). The magnetic source 1 may comprise a permanent
magnet, an electromagnet (including coil of wiro, coil of wiro on a ferromagnetic material,
or coil of wiro on a magnet), or the like as long as a constant magnctio field can be
generated. The magnetic source may optionally further comprise a slider and control
interface so as to control the position of the magnetic source within the apparatus. In
addition, tho magnetic source 1 may come in various geometry and sizes. As discussed
hereinafter, a magnetic source may produce a magnetic field strength of 1000 Gauss ± 20
% tolerance; that was used for tho inventors experiments. It is to be notod that the
magnetic source may be of other magnetic field strength where tho related parameters (e.g.,
tho sensitivity of tho sensor, the distance between the magnetic source and sensor, and the
relative placement and orientation of the magnetic source and sensor with respect to a
blood vessel) will have to be modified with appropriate support from experimental results.
[0051] The signal acquisition module 2 comprises a magnetic sensor that is able to
translate magnetic variations to voltages proportional to the variations of the magnetic
signature. The magnetic sensors suitable for tho present invention include, but are not
limited to, spintronics. based sensors (e,g. giant magnctorcsistive (GMR) sensor and
tunneling magnetoresistivc (TMR) sensor), anisotropic magnctorcsistive (AMR) sensors
and any magnetic based sensors. One exemplary magnetic sensor is a Spintronics based
magnetic sensor (e.g., AAH002-02 manufactured by NVE Corporation). It is to bo noted
that other magnetic-based sensors, with different sensitivities may also be used to detect tho
modulated magnetic signature of blood flow (MMSB), but the related parameters (e.g., the
strength of the magnetic source, the distance between the magnetic source and sensor, and
tho relative placement and orientation of the raagnetio source and sensor: with respect to a
blood vessel) will have to bo modified with appropriate support from experimental results.
[0052] Magnetic sensors are well known in the art. Their working principles will
only be briefly described herein. Such sensors change their resistances based on the
magnetic field applied. FIGs 9a and 9b show a graphic illustration of the working principle

behind the GMR magnetic sensors. As shown in FIG 9a, a conductive, nonmagnetic
interlayer A is sandwiched by two-alloy layers B; when no external magnetic field is
applied, the magnetic moments in the alloy layers face opposite directions (represented by
the arrows), and the resistance to current C is high. As shown in FIG 9b, when an external
magnetic field D is applied, applied external magnetic field overcomes: anti-ferromagnetic
coupling, aligning magnetic moments in alloy layers, and the electrical resistance drops
dramatically; 10% to 15% is typical. The magnetic signal variation is translated to a
corresponding change of resistance in the GMR sonsor device. This change of resistance
with magnetic field applied can be illustrated as shown in HG 4. To those skilled in the
art, the curve shows a change of resistance that can be correlated to minute variations in
magnetic field.
[0053] Now referring to FIG 2, there is provided an exemplary schematic electronic
circuit for the signal acquisition module 2 in accordance with one embodiment of the
present invention. The circuit of the signal acquisition module 2 is so configured that a
direct current (DC) power supply such as a battery to create a potential across the
Wheatstone-Bridge connected to the GMR sensor. Coupled with the use of a Whcatstonc-
Bfidge, the change in resistance due to the minute variations in the magnetic field can, be
translated into a measurable potential To those skilled in the art, the potential applied
across Y+ and V- will result in a measured output across OUT+ and OUT- Tho changes
in resistance due to the applied magnetic field will then bo linearly translated to a
differential potential change across OUT+ and OUT-. Acquiring and measuring this
differential potential will allow the magnetic field variations duo to MMSB to bo quantified
and processed for measuring pulse rates and detecting blood flow anomalies.
[0054] With tho application of a localised, unidirectional, and constant magnetic
source, tho measurable range of the Spintronics based magnetic sensor is shifted as shown
in FIG 4. To those skilled in tho art, this will provide better linearity for the sensor to detect
the minute changes of magnelio field generated from tho modulated magnetic signature of
blood (MMSB).
[0055] For optimized measurement of pulse rates and detection of blood flow
anomalies by the apparatus, the factors other than the strength of the magnetic source and
the sensitivity of tho magnetic sensor need to be considered. First is the placement and
orientation of the magnetic source with respect to a blood vessel. Tho magnetic source 1

may Be preferably placed along the longitudinal axis of the blood vessel at an appropriate
proximity that will generate a signal which can be detected by the magnetic senior,. In
addition, the magnetic source may also be placed at an offset position or angle with respect
to the longitudinal axis of any major blood vessels near the surface of the skin. If so, then
other parameters including tho strength of the magnetic source, the sensitivity of the
sensor, and tho distance between the magnetic source and sensor will have to be modified
with appropriate support from experimental results. Second is the distance between the
magnetic source and sensor. The distance is affected by many factors including the
strength of the magnetic source. For example, when the magnetic source is about 1000
Gauss, the distance between tho magnetic source and sensor is about 2.5 cm ± 20 %.
When the magnetic source produces a magnetic field with different strengths, it is easy for
those skilled in the art to determine the proper range within which the magnetic sensor can
be disposed without undue experimentation.
[005G1 The magnetic source and magnetic sensor can sense tho pulse rate and blood
flow in a non-direct contact configuration. As shown in FIG la, ono space gap 7 may exist
between the magnetic source/sensor and the skin. For example, the space gap could be
fabric, perspiration and oil secretion between them. The thickness of tho space gap can be
easily determined in consideration of tho strength of the magnetic source, the sensitivity of
the magnetic sensor, and the material used in tho space gap.
[0057] Now referring back to HG 1, tho signal conditioning modulo 3 converts tho
differential-ended output of tho signal acquisition module 2 into a single-ended signal with
appropriate amplifications. In ono embodiment, tho signal conditioning modulo 3
comprises an amplifier for amplifying the signals received from the signal acquisition ,
modulo, anda signal digitization circuit for digitizing tho received signals. FIG 2 shows an
exemplary schematic circuit of the signal conditioning modulo 3. The suitable circuits aro
well known in tho art. As shown in FIG 2, an optional envelope detector and/or filter is
proposed before digitization of tho signal using an analoguc-to-digital converter (ADC).
To those skilled in the art, this will allow them to implement analogue signal selection
before digitization,
[0058] Now referring to FIG 1 and FIG 2, tho digital signal processing modulo 4
proccssos tho digital signals from the signal conditioning modulo 3 to measure the pulso
rate and detect blood flow anomaly, In one embodiment, the signal processing module 4

comprises a microcontroller, a microprocessor, a digital signal processor, programs to
perform signal analysis, and a memory for storing oll the programs and providing venues
for the execution of the programs. The result output /display module 5 displays the two
measurable parameters-blood flow anomaly and measured pulse rate-obtained from the
digital signal processing modulo 4 m cither discrete (LED) or continuous form (LCD), In
one embodiment, the result output/display module 5 comprises a display, an alarm, and a
user interface,
[0050] The outputs may take different forms. For example, the outputs may be an
alarm notification if any anomalies are detected. The pulse rates may be expressed as
pulses per minute. The outputs may also bo digital data with computed pulse rates. Typical
digital data are shown in FIG 5 and FIG 6 for normal and abnormal blood flow condition
respectively. Typical digital data are shown an FIG 7 and FIG S (at a more refined
resolution) for normal and abnormal blood flow condition respectively. The calculation of
pulse rates from the digital data will bo discussed hereinafter.
[0060] Now referring to FIG 3, there is provided a functional block diagram of the
non-invasivo magnetic apparatus that is able to automate signal acquisition to achieve
optimal signal level. As shown in FIG 3, the signal processing module 4 now has the
feedback capacities to control the sensitivity of the sensor and placement mechanism such
as a slider in the signal conditioning module, The placement mechanism enables a user to
manually or automatically adjust the position and orientation of the magnetic source. In
turn, tho sensitivity control feedbacks to the signal acquisition module, and the slider
control feedbacks to tho magnetic source to vary magnetic positions. While not shown in
FIG 3, the signal acquisition modulo may further comprises a placement mechanism
enabling a user to manually or automatically adjust tho position and orientation of the
magnetic sensor. In addition, while not shown in FIG 3, the magnetic source may further
comprise a strength adjustment mechanism when the electromagnet is used as tho magnetic
source. Tho devices for controlling position and orientation of the magnetic source and
sensor and for controlling the strength of the magnetic source arc well known to those in
the arts; any suitable devices may be used in the present invention.
[0061] Still referring to FIG 3, tho apparatus further comprises a wireless interface
modulo 8 to allow remote monitoring. Tho base station 9 may be incorporated into the
apparatus or employed in a separate location for receiving the information from tho

apparatus. The base station comprises a data CODEC (Encoder and Decoder) and
transceiver modules, display and user interface module, and microprocessor modules with
HAM/ROM. The wireless transmission is well known in the art, thus no details will be
provided herein.
[0062] Now referring to FIG 10, there is provided a flow chart of the method for
sensing the pulse rato and blood flow anomalies using a localized, uni-dircctional, and
constant magnetic field.
[0063J The method 100 starts with placing directly or in proximity to the skin the
apparatus for non-invasively sensing pulse rato and blood flow using the localized, uni-
directional, and constant magnetic field 110, The magnetic source and sensor of the
apparatus is preferably disposed along the longitudinal axis of a major blood vessel such
as, but not limited to, the ones found on the wrist, leg, or heel.
[0064] Then, the sensor is then connected to a direct current (DC) power supply
120 such as a battery to create a potential across the Whcatstone-Bridgo connected to the
GMR. sensor. For example, when the sensor used is the NVB AAH002-02, the potential
applied is a DC voltage supply of 9V. Then, the signal acquisition module outputs the
differential outputs, OUT+ and OUT-130.
[00065] Then, the output signals from the signal acquisition modulo are amplified by
the signal conditioning module before any analogue signal conditioning (optional) 140, To
those skilled in the art, such a configuration will ensure signal integrity. The analogue
signal will then be digitised by tho analogue-to-digital converter (ADC),
[0066] Then, the conditioned output signals from the signal conditioning module
are processed by the signal processing module to measure tho pulse rate and detect blood
flow anomalies 150. Now referring to FIG 5, there is provided a typical digital data
acquired with normal blood flow on the wrist The pulse rate can bo calculated with the
following equation;

where n is the number of pulses detected within the time duration T (in seconds); a is the
time interval between two adjacent pulses as shown in FIG 5; and T is the total time to
observe n pulses in seconds. Tho measurable parameter a can be used for tho observation

of heart beat anomaly such as the presence of a chaotic pattern which could signify the on
set of a heart attack or cardiac arrhythmia,
[0067] Then, the outputs from the signal processing module include pulse rate and
blood flow anomalies. The outputs will be displayed 160 on the result output /display
module.
[0068] The apparatus and method of the present invention is applicable to many
situations. For example, hospitals can use the apparatus for monitoring patients; athletes
. can use the apparatus for monitoring their blood flow; elders can be monitored remotely
with the wireless apparatus; blood flow anomalies can be detected in different
circumstances such as long flight, rescues, and dangerous situations.
[0069] FIGS 11-13 shows the placement and configuration of the non-invasive
magnetic apparatus in accordance with one embodiment of the present invention. The
magnetic source 1 and magnetic signal acquisition module % are placed along the
longitudinal axis of the blood vessel on the wrist In this design, the apparatus can be '
incorporated into any wrist wearing devices or decors. Of course, the apparatus can be
used in other parts of a body and incorporated into other devices,
[0070] While the present invention has been described with reference to particular
embodiments, it will be understood that the embodiments are illustrative and that the
invention scope is not so limited. Alternative embodiments of the present invention will
become apparent to those having ordinary skill in the art to which the present invention
pertains. Such alternate embodiments are considered to be encompassed within the spirit
and scope of the present invention. Accordingly, the scope of the present invention is
described by the appended claims and is supported by the foregoing description.

We Claim:
1. An apparatus for non-invasively monitoring of blood flow of a living subject,
comprising:
a magnetic source for producing a localized, uni-directional, and constant magnetic
field; and
a signal acquisition module with a magnetic sensor, wherein the magnetic sensor is
disposed within the magnetic field and detects the modulations of the localized, uni-
directional, and constant magnetic field effected by the blood flow passing through the
magnetic field in a blood vessel near the skin surface of the living subject;
a signal conditioning module for converting the output of the signal acquisition
module with appropriate amplifications; and
a digital signal processing module Tor processing the output signal from the signal
conditioning module;
thereby pulse rate and blood flow anomaly can be monitored.
2. The apparatus as claimed in claim 1, further comprising a notification module for
providing visual or acoustic notification to a user.
3. The apparatus as claimed in claim 1, wherein the magnetic source is a permanent
magnet.
4. The apparatus as claimed in claim 1, wherein the magnetic source is an
electromagnet.
5. The apparatus as claimed in claim 4, wherein the strength of the magnetic field
produced by the electromagnet is controlled electronically,
6. The apparatus as claimed in claim 1, wherein the magnetic source is preferably able
to produce a magnetic field strength of 1000 Gauss + 20% tolerance.

7. The apparatus as claimed in claim 6, wherein when the magnetic source is
preferably able to produce a magnetic field strength of 1000 Gauss + 20% tolerance, the
magnetic source and magnetic sensor are separated by a distance of approximately 2.5 cm
+ 20 %,
8. The apparatus as claimed in claim 1, wherein the magnetic sensor is any magnetic
sensor with appropriate sensitivity of detecting the modulation of the magnetic field from
the magnetic source.
9. The apparatus as claimed in claim 8, wherein the magnetic sensor is a Giant
Magneto Resistance (GMR) magnetic sensor.
10. The apparatus as claimed in claim 8, wherein the magnetic sensor is a Spintronics
based magnetic sensor.
11. The apparatus as claimed in claim 8, wherein the magnetic sensor is an anisotropic
magnctorcsistivc sensor.
12. The apparatus as claimed in claim 1, wherein the magnetic source and the magnetic
sensor are placed along the longitudinal axis of the blood vessel,
13. The apparatus as claimed in claim 1, wherein the magnetic source and sensor arc
placed at an offset position or angle with respect to the longitudinal axis of the blood
vessel.
14. The apparatus as claimed in claim 1, wherein the signal conditioning module
comprises an amplifier for amplifying the signals received from the signal acquisition
module, and a signal digitization circuit for digitizing the received signals.

15. The apparatus as claimed in claim 14, wherein the signal conditioning module
further comprises an envelope detector and/or filter using an analogue-to-digital converter
(ADC).
16. The apparatus as claimed in claim 1, wherein the signal processing module
comprises a microcontroller, a microprocessor, a digital signal processor, programs to
perform signal analysis, and a memory for storing all the programs and providing venues
for the execution of the programs.
17. The apparatus as claimed in claim 16, wherein the microprocessor calculates the
pulse rate with the following equation:

where n is the number of pulses detected within the time duration T (in seconds); and T is
the total time to observe n pulses.
18. The apparatus as claimed in claim 1, wherein the magnetic source further
comprises a placement mechanism controlling the placement of the magnetic source in
respect to the signal acquisition module and the orientation of the blood vessel; thereby the
placement of the magnetic source can be controlled.
19. The apparatus as claimed in claim 18, wherein the signal processing module further
has the feedback capacities to control the signal for the placement mechanism and the
signal for a sensitivity control for sensor in the signal conditioning module; in turn, the
sensitivity control feedbacks to the signal acquisition module to control the sensitivity of
the magnetic sensor, and the signal for the placement mechanism feedbacks to the
magnetic source to vary magnetic positions,
20. The apparatus as claimed in claim 1, wherein the signal acquisition module further
comprises a placement mechanism for a user to manually or automatically adjust the
position and orientation of the magnetic sensor.

21. The apparatus as claimed in claim 2, wherein the notification module displays the
two measurable parameters: blood flow anomaly and measured pulse rate.
22. The apparatus as claimed in claim 2, wherein the notification module comprises a
display, an alarm, and a user interface,
23. The apparatus as claimed in claim 1, further comprising:
a wireless interface module to allow remote monitoring the pulse rate and blood
flow anomaly; and
a base station for receiving the information from the wireless interface module.
24. The apparatus as claimed in claim 23, wherein the base station comprises a data
CODEC (Encoder and Decoder) and transceiver modules, display and user interface
module, and microprocessor modules with RAM/ROM.

The present invention provides an apparatus and method for non-invasively sensing pulse
rate and blood flow anomalies using a localized, uni-directional, and constant magnetic
field. The apparatus comprises a magnetic source for producing the magnetic field, a signal
acquisition module with a magnetic sensor for detecting the modulations of the magnetic
field caused by the blood flow; and a signal processing module for processing the acquired
signals so as to produce data of pulse rate and blood flow anomalies. The method senses
pulse rate and blood flow anomalies by providing a localized, uni-directional, and constant
magnetic field in proximity to a blood vessel; detecting the variations of the magnetic field
caused by the flow of pulsatile blood within the blood vessel; and processing the signals of
the detected variations so as to monitor the blood flow.

Documents:

3354-KOLNP-2008-(11-09-2013)-CORRESPONDENCE.pdf

3354-KOLNP-2008-(11-09-2013)-OTHERS.pdf

3354-KOLNP-2008-(15-10-2013)-ABSTRACT.pdf

3354-KOLNP-2008-(15-10-2013)-CLAIMS.pdf

3354-KOLNP-2008-(15-10-2013)-CORRESPONDENCE.pdf

3354-KOLNP-2008-(15-10-2013)-DESCRIPTION (COMPLETE).pdf

3354-KOLNP-2008-(15-10-2013)-DRAWINGS.pdf

3354-KOLNP-2008-(15-10-2013)-FORM-1.pdf

3354-KOLNP-2008-(15-10-2013)-FORM-2.pdf

3354-KOLNP-2008-(15-10-2013)-FORM-3.pdf

3354-KOLNP-2008-(15-10-2013)-OTHERS.pdf

3354-KOLNP-2008-(15-10-2013)-PETITION UNDER RULE 137.pdf

3354-kolnp-2008-abstract.pdf

3354-kolnp-2008-claims.pdf

3354-KOLNP-2008-CORRESPONDENCE-1.1.pdf

3354-kolnp-2008-correspondence.pdf

3354-kolnp-2008-description (complete).pdf

3354-kolnp-2008-drawings.pdf

3354-kolnp-2008-form 1.pdf

3354-kolnp-2008-form 18.pdf

3354-kolnp-2008-form 2.pdf

3354-KOLNP-2008-FORM 3-1.1.pdf

3354-kolnp-2008-form 3.pdf

3354-kolnp-2008-form 5.pdf

3354-kolnp-2008-international preliminary examination report.pdf

3354-kolnp-2008-international publication.pdf

3354-kolnp-2008-international search report.pdf

3354-kolnp-2008-others.pdf

3354-kolnp-2008-pct priority document notification.pdf

3354-kolnp-2008-specification.pdf

abstract-3354-kolnp-2008.jpg

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Patent Number

258964

Indian Patent Application Number

3354/KOLNP/2008

PG Journal Number

08/2014

Publication Date

21-Feb-2014

Grant Date

18-Feb-2014

Date of Filing

18-Aug-2008

Name of Patentee

NANYANG POLYTECHNIC

Applicant Address

180 ANG MO KIO AVENUE 8 Singapore 569830

Inventors:

#	Inventor's Name	Inventor's Address
1	PHUA, CHEE TECK	BLOCK 92 PIPIT ROAD # 12-99 SINGAPORE 370092
2	KAM, SEE HOON	BLK 236 COMPASSVALE WALK #14-512, SINGAPORE 540236
3	GOOI, BOON CHONG	9 BUKIT BATOK CENTRAL LINK #08-04, SINGAPORE 658074
4	YING, MING HUA	BLK 110 BUKIT MERAH VIEW #11-558, SINGAPORE 150110

PCT International Classification Number

A61B 5/0265

PCT International Application Number

PCT/SG2006/000409

PCT International Filing date

2006-12-29

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	200601301-5	2006-02-27	Singapore