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1. It was further found experimentally that character istic point A which is normally not very clearly identifiable in Oct 30 2008 an impedance cardiagram is more easily distinguishable using the apparatus of the invention and the technical features detailed in claim 1 0051 Using these characteristic points several parameters can be calculated as is commonly known in the art but see for example user manual for the pc software of the publically available Niccomo hemodynamic monitor supplied origi nally by Medis GmbH now owned by CardioDynamics Sec tion D Description of the calculated parameters pages 55 64 detailing commonly known clinically relevant param eters and details of their calculation using the known charac teristic points These parameters include pre ejection period left ventricular ejection time systolic time ratio and ejection time ratio The parameter of left ventricular ejection time is sometimes referred to in the art as left ventricular ejection phase The calculation of these parameters proceeds along the same lines as for their calculation using the prior art method of impedance cardiography and is therefore not the subject of this invention However as can be seen from the Niccomo user manual calculation of these parameters in the prior art requires characteristic points derived from an impedance car diogram The invention provides a measure of mechanical heart activity which provides improve2. doppler signal to produce an output signal representing the rate of change of the doppler signal with respect to time In fact calculation of the doppler signal itself is not strictly necessary as an intermediate step and other methods of calculating this rate of change of the doppler signal may be performed by the person skilled in the art as a matter of design once he understands that it is the rate of change of the doppler signal information which allows iden tification of the characteristic points 0056 Alternatively the first processor could be arranged to calculate the rate of change of the doppler signal and identify the characteristic points and then communicate these to the second processor which is arranged to perform the further analysis 0057 Alternatively the first processor could be arranged to calculate the rate of change of the doppler signal identify the characteristic points and then calculate the parameters communicating any combination of these to a further proces sor or workstation where the results can be examined by a doctor or other medical professional 0058 Inanalternative embodiment to the wireless transfer of information between the transducer and processor the transducer may store the information contained in the detected signal for transfer to a processor via a docking sta tion or other fixed connection after the measurement session is complete This removes the need for wireless capability and thereby
3. geographically separate from each other In the latter case transmission of informa tion between the processors can be accomplished by any known wireless means or by modem connection or by known computer network technology 0011 The invention also relates to a wearable apparatus to detect mechanical heart activity of an individual using dop pler radar comprising a transducer to transmit electromag netic signals of a certain frequency into the chest of the individual and to detect reflected signals from out of the chest and to transmit a signal representative of the detected signal to be received by a processing system which system is arranged to use the received signal to calculate an output signal representing the rate of change of the doppler signal associated with the reflected signal the rate of change with US 2008 0269589 Al respect to time to identify from the output signal a group of at least one characteristic point of the output signal and to calculate at least one parameter representative of heart activ ity the calculation based on the at least one identified char acteristic point 0012 This apparatus has the advantage that it can be worn by an individual while they move around and can therefore acquire signals demonstrating mechanical heart activity while the individual is ambulatory It has the further advan tage that the wearable apparatus need only comprise a suit able transducer for the production of elect
4. person Further the frequency modulation of the doppler shifted signal allows the required signal to be identi fied with respect to any other stray signals detected by the original transducer These stray signals may originate from for example back scattering of the original signal by organs in the body for example the heart or lungs U S Pat No 4 967 751 discloses that the movement of these organs intro duces a doppler frequency component into the back scattered signal and explains that this may originate from the breathing rate the beating rate of the heart and the movement of the heart valves 0005 U S Pat No 3 483 860 describes a method for monitoring heart movement comprising transmitting a radio frequency signal into the body and detecting and processing the reflected signal to produce an output signal The output signal is further differentiated to provide an indication of rate of ejection of blood from the heart 0006 It is an object of the invention to provide an improved measurement of mechanical heart activity 0007 This is achieved according to the invention whereby the method further comprises the steps of identifying from the output signal a group of at least one characteristic point of the output signal and further calculating at least one parameter representative of heart activity the calculation based on the at least one identified characteristic point Oct 30 2008 0008 The method includes transmitti
5. reduces the possibility of signal interference in an environment with a inherently large electromagnetic signal load 0059 Alternatively the transducer may remain connected to the processor via a fixed connection such as a lead during the measurement session This also reduces the possibility of interference while allowing interim results to be calculated during the measurement session This provides advantages in the case whereby the individual experiences a sudden increase in symptoms and it becomes desirable to communi cate information regarding the mechanical activity of the heart urgently to a medical professional 0060 In an exemplary embodiment the transducer situ ated in a comfortable harness is used by the individual once a day for a short period of time say 5 mins to take readings of the activity of the heart The resultant data either as raw data or as identified characteristic points or as calculated param eters is transmitted to a geographically remote location where it is analyzed by a doctor or other medical professional for monitoring of the individual over time 0061 Inthis case the correct position of the transducer on the chest of the individual can be initially identified using an initially performed impedance cardiogram Thereafter the individual simply places the transducer in the correctly iden tified position at regular intervals say once a day and oper ates it himself to provide parameters which provi
6. the plane of the trans ducer for example a section of heart wall muscle is highly advantageous in receiving an adequate reflected signal 0038 The transducer can be incorporated in a suitable housing which is advantageously dimensioned so that it can be arranged flat against the chest for example the sternum of the individual Suitable dimensions are between 3 and 6 cm wide and between 4 and 7 cm long These sizes allow for the hardware to be contained in the housing while maintaining the housing at a size which can be used effectively on an individual 0039 The technical steps to be performed in the process ing of the recorded data to provide an output signal containing the rate of change of the data with respect to time can be undertaken by a person skilled in the art using known data processing techniques For example it can be achieved using the Matlab computer language 0040 Similarly the method used to extract a signal repre sentative of the rate of change of the signal with respect to time will be known to the person skilled in the art For example the signal can be sampled and the rate of change of each sample over the length of the sample extracted How ever the output signal can also be calculated by inverse trans forming the detected signal to derive the mathematical func tion of the signal and mathematically deriving the function to produce the first order derivative 0041 FIG 3 shows the output of the processor whi
7. the rate of change of the detected signal is contactable via the world wide web In this case the skilled person can arrange for the signal from the wearable apparatus to be transmitted to an intermediate pro cessor a computer with a connection to the world wide web say which is arranged to transmit the signal representative of the detected signal through the world wide web to the remote processor Alternatively the wearable apparatus can be equipped with suitable processing to allow for the direct transmission of the signal representative of the detected sig nal into the world wide web to the remote processor 0021 Thus the system solves the problem of how to pro vide monitoring of mechanical heart activity from a location remote from the location of the individual being monitored 0022 The apparatus of the invention is particularly advan tageously arranged when it emits continuous wave electro magnetic waves although as a feature this is not necessary The apparatus of the invention achieves the desired result if the emitted and reflected signal is of such a duration that it is able to encode information from at least a single heart beat This can definitely be achieved if the electromagnetic signals are emitted in the form of a continuous beam However pulsed electromagnetic signals can also be used if each single pulse is long enough to encode the information from a single heart beat or for example if the time interval between
8. wide web wherein said computer is adapted to further trans mit the signal representative of the detected signal through the world wide web to the processing system 4 A processing system for receiving a signal transmitted from a wearable apparatus to detect mechanical heart activity of an individual using doppler radar the system arranged to receive a signal representative of a reflected electromagnetic signal detected from out of the chest of an individual and further arranged to US 2008 0269589 Al calculate an output signal representing the rate of change of the doppler signal associated with the reflected signal the rate of change with respect to time identify from the output signal a group of at least one characteristic point of the output signal and calculate at least one parameter representative of heart activity the calculation based on the at least one identi fied characteristic point wherein the processing system is adapted to receive the signal representative of the detected signal through the world wide web from a computer with a connection to the world wide web wherein said computer is adapted to receive the signal representative of the detected signal wirelessly from the wearable apparatus 5 canceled 6 The apparatus as claimed in claim 3 wherein the rate of change of the detected signal with respect to time is calculated as the first order derivative of the detected signal with respect to time 7
9. The apparatus as claimed in claim 3 wherein the trans ducer is arranged to emit continuous wave electromagnetic signals 8 The apparatus as claimed in claim 3 wherein the trans ducer emits continuous wave electromagnetic signals at a frequency in a range between 400 MHz and 5 GHz Oct 30 2008 9 The apparatus as claimed in claim 8 wherein the trans ducer emits continuous wave electromagnetic signals at a frequency in a range between 800 MHz and 4 GHz 10 The apparatus as claimed in claim 9 wherein the trans ducer emits continuous wave electromagnetic signals at a frequency of 2 45 GHz 11 The apparatus as claimed in claim 3 wherein it further comprises a display screen for the display of the output signal 12 The apparatus as claimed in claim 3 wherein the parameters representative of heart activity include at least one of pre ejection period left ventricular ejection time systolic time ratio and ejection time ratio 13 The apparatus as claimed in claim 3 wherein it is further arranged to output the value of at least one calculated parameter representative of heart activity 13 The method of claim 1 wherein the at least one param eter representative of heart activity is transmitted to a com puter aided detection system designed to automatically moni tor the individual s health and output and alert in the event that the parameter indicates a deterioration in the individual s condition
10. US 20080269589A1 a2 Patent Application Publication o Pub No US 2008 0269589 A1 as United States Thijs et al 43 Pub Date Oct 30 2008 54 APPARATUS FOR THE DETECTION OF G0 Foreign Application Priority Data HEART ACTIVITY Jul 15 2005 BP anna 05106544 9 75 Inventors Jeroen Adrianus Johannes Thijs Aachen DE Robert B Elfring Aachen DE Jens Muehlsteff Aachen DE Olaf Such Aachen DE Correspondence Address PHILIPS INTELLECTUAL PROPERTY amp STANDARDS 595 MINER ROAD CLEVELAND OH 44143 US KONINKLIJKE PHILIPS ELECTRONICS N V Eindhoven NL 73 Assignee 21 Appl No 11 995 543 22 PCT Filed Jul 14 2006 86 PCT No 371 c 1 2 4 Date PCT IB06 52407 Jan 14 2008 DR1 DR2 LP 100 Hz 5V GND DC DC Publication Classification 51 Int Cl AGIB 5 05 2006 01 GA USE ende 600 407 57 ABSTRACT The invention relates to heart measurement and heart moni toring in particular the measurement of mechanical heart activity and includes a method and apparatus to using dop pler radar to transmit an electromagnetic signal of a certain frequency into and detect a reflected signal from out of the chest of the individual to processing the detected signal to produce an output signal representing the rate of change of the doppler signal associated with the reflected signal and to identify from the output signal a group of at least one char acter
11. ated doppler radar to measure heart rate is known U S Pat No 4 958 638 for example describes a vital signs monitor utilizing a frequency modulated doppler radar beam which when trained on the surface of the chest from a distance provides a measurement of heart rate The frequencies of 3 and 10 GHz used for the vital signs monitor are reported as having minimal penetra tion into the body 0003 Less Contact Heart rate detection without even touching the user by Florian Michahelles Ramon Wicki and Bernt Schiele Eighth International Symposium on Wearable Computers ISWC 2004 Volume 1 pp 4 7 31 Oct 3 Nov 2004 describes a system to measure heart rate using micro impulse radar pulses The detected signal is filtered and the distances between all local maxima calculated and analyzed for regularly occurring patterns All maxima occurring within a certain distance are presumed to stem from the heart beat and are used to derive the heart rate 0004 U S Pat No 4 967 751 describes a system for mea suring breathing rate using the transmission of a continuous frequency electromagnetic wave through the upper body of a human being the detection of the doppler shifted signal on the other side of the upper body the frequency modulation of this detected signal and its retransmission back through the upper body and eventual detection at the original transducer The signal contains cyclical information about the breathing rate of the
12. ch processes the signal detected by the transducer The first trace 301 is the detected signal The second trace 302 is the rate of change of the detected signal with respect to time The third trace 303 is an example of a trace from an impedance cardio gram It can be seen from FIG 3 that the characteristic points of the impedance cardiogram 303 can be similarly identified on the trace representing the rate of change of the detected signal Specifically these characteristic points known to the skilled person are 0042 A representing the contraction of the atrium 0043 B representing the opening of the aortic valve and the beginning of the systolic ejection phase 0044 C representing maximum systolic flow 0045 X representing the closing of the aortic valve and the end of the ejection phase 0046 Y representing the closing of the pulmonal valve 0047 O representing the opening of the mitral valve 0048 In other words points equivalent to known charac teristic points identifiable from an impedance trace are now also identifiable from a signal which is the rate of change of a detected doppler signal reflected from the heart of an indi vidual 0049 The characteristic points can be identified using known techniques of signal processing and is a matter of design for the person skilled in the art For example the characteristic points can be identified from analysis of the morphology of the rate of change trace 302 0050
13. commercially available and are often used for the purposes of detection of movement using the far field of the beam for example in Radar measurements of traffic speed It is now found according to the invention that such transducers can also be used for near field measurements and are surpris ingly suitable for detecting mechanical heart activity via the detection of doppler shifted signals from the heart 0031 Generally in such doppler transducers as is known in the art an antenna emits an electromagnetic wave which when it is reflected from the surfaces of an object moving with a component of velocity non transverse to the impinging electromagnetic wave produces a shift in the frequency of the electromagnetic wave reflected back to the antenna This shift in frequency is called the doppler shift This doppler shifted reflected wave is detected by an antenna in the transducer which may or may not be the same antenna as the emitting antenna The relative speed of movement of the reflecting object is encoded in the frequency shift of the detected reflected wave and this value can be extracted using known techniques 0032 A transducer advantageously used in the apparatus of the invention contains a 2 45 GHz oscillator operating in continuous mode It is known that electromagnetic radiation is strongly absorbed in human tissue at around the frequen cies of 2 to 10 GHz but it is found according to this highly advantageous embodiment of t
14. d information concern ing heart movement 0052 The computer processing arranged to calculate the doppler signal calculate the rate of change of the doppler signal identify the characteristic points and then calculate the parameters from the characteristic points can be situated in various items of equipment Although the transducer itself will of necessity be positioned when in use in such a way that a doppler signal is produced which encodes information about the heart the processing that occurs after the transducer has received the initial signal need not be physically coupled to the transducer but may be arranged to received the output of the transducer wirelessly using any known wireless means Similarly the stages of processing may be separated and undertaken in processing units which are situated physically apart from each other but arranged to relay or transmit their results to each other using any known method including for example wireless transmission transmission down a tele phone line or say along a fixed physical connection such as a wire 0053 Asan example of how the invention may be worked the individual whose heart activity is to be measured is pro vided with a wearable doppler transducer fitted into a com fortable harness and coupled to a transmitter arranged to transmit the detected signal to a first remote processor which performs the actions of processing the signal to produce a doppler signal calculating t
15. de informa tion concerning the mechanical activity of his heart The resulting information is advantageously used when commu nicated to a doctor or health monitoring service but could Oct 30 2008 also be transmitted directly to a processor which is part of a computer aided detection system designed to automatically monitor the individual s health and alert him or a doctor or a health monitoring service in the event that the calculated parameters indicate a deterioration in the individual s condi tion 0062 It can be seen in the light of the information above that the invention provides a system for monitoring which is particularly suitable for use in the home and which does not require repeated use of impedance cardiograms which are inappropriate for use by untrained personnel 1 A method to detect mechanical heart activity of an indi vidual using doppler radar comprising transmitting an electromagnetic signal of a certain fre quency into and detecting a reflected signal from out of the chest of the individual transmitting a signal representative of the detected signal to a processing system processing by processing system the detected signal to produce an output signal representing the rate of change of the doppler signal associated with the reflected signal the rate of change with respect to time wherein the method further comprises the steps of identifying by the processing system from the output sig nal a
16. group of at least one characteristic point of the output signal and further calculating by the processing system at least one parameter representative of heart activity the calcu lation based on the at least one identified characteristic point wherein the signal representative of the detected signal is transmitted wirelessly to a computer with a connection to the world wide web and from said computer through the world wide web to the processing system 2 canceled 3 A wearable apparatus to detect mechanical heart activity of an individual using doppler radar comprising a transducer to transmit electromagnetic signals of a cer tain frequency into the chest of the individual and to detect reflected signals from out of the chest and to transmit a signal representative of the detected sig nal to a processing system which system is arranged to use the received signal to calculate an output signal representing the rate of change of the doppler signal associated with the reflected signal the rate of change with respect to time identify from the output signal a group of at least one characteristic point of the output signal and calculate at least one parameter representative of heart activity the calculation based on the at least one identi fied characteristic point wherein the apparatus comprises means for transmitting the signal representative of the detected signal wire lessly to a computer with a connection to the world
17. he invention that the radiation produced from an antenna operating at 2 45 GHz although absorbed and scattered to some extent by layers of tissue produces a detectable signal Oct 30 2008 0033 A particularly advantageous embodiment utilizes a commercially available Microwave Motion Sensor KMY 24 unit made by Micro Systems Engineering GmbH It contains a 2 45 GHz oscillator and receiver in the same housing and works in continuous wave mode The dimensions of the beam are amongst other things dependent on the dimensions of the antenna and in this case the unit contains an optimized patch antenna with minimized dimensions and a width of 3 5 cm producing a beam with a near field radius of 2 cm This provides a workable compromise between too large an antenna which would produce a wide beam easily contami natable by reflections from other structures and too small an antenna which would produce a narrow beam which is dif ficult to position satisfactorily In practice a beam with a width in the range of 1 cm to 2 5 cm is advantageous because it provides a workable compromise between the two extremes described above A beam with a width in the range of 1 5 cm to 3 cm is particularly advantageous for application of the apparatus to large adults or adults with an enlarged heart A beam with a width in the range of 0 5 cm to 1 75 cm is advantageous for application of the apparatus to small chil dren 0034 The commercially available uni
18. he rate of change of this doppler signal identifying the characteristic points and using these to calculate any required parameters In the case when the resulting first processor is in the same location as the indi vidual for example their home residence or hospital ward this first processor can be arranged to further transmit the resulting parameters along with the doppler trace and or a trace of the rate of change of the doppler signal as appropriate to aremote second processor situated in a computer worksta tion The results can be accessed at this workstation by a doctor or other medical professional for the purposes of monitoring the health of the individual 0054 Alternatively the first processor could be arranged to calculate only the doppler signal and communicate this to the second processor which can itself be arranged to perform all further analysis US 2008 0269589 Al 0055 Alternatively the first processor could be arranged to calculate only the doppler signal and calculate the rate of change of this doppler signal and then communicate this to the second processor which can itself be arranged to perform all further analysis In this sense the step of processing the detected signal to produce an output signal representing the rate of change of the doppler signal associated with the reflected signal can as an example be performed by first processing the detected signal to produce a doppler signal and then processing the
19. ich pumps blood around the body It is subdivided into 4 cham bers consisting of 2 atria which receive blood entering the heart with deoxygenated blood returning from the body entering into the right atrium and oxygenated blood from the lungs entering into the left atrium and 2 larger ventricles which are responsible for pumping blood out of the heart The right ventricle pumps deoxygenated blood received from the right atrium out of the heart and to the lungs where it is oxygenated The left ventricle the largest chamber in the heart is responsible for pumping oxygenated blood received from the left atrium out into the rest of the body As is also known measurements from electrocardiography ECG show that the heart pumps in a cyclical fashion and ECG measure ments allow identification of certain phases common to the electrical sequence of the heart FIG 1 shows a typical output trace from an ECG measurement The characteristic spikes shown in a typical trace are labeled P Q R S and T as indicated It is known that the P spike or wave is represen tative of the depolarization or excitation of the atria The QRS spikes known commonly as the QRS complex are representative of the excitation of the ventricles The QRS complex masks any signal from the repolarisation of the atria The T spike or T wave is representative of the repolarisation of the ventricles 0030 Transducers for the detection of doppler shifted sig nals are
20. istic point of the output signal and further to calculate at least one parameter representative of heart activity this cal culation based on the at least one identified characteristic point The apparatus provides a system for monitoring which is particularly suitable for use in the home and which does not require repeated use of impedance cardiograms which are inappropriate for use by untrained personnel 204 203 201 Doppler Module 5V 12V Patent Application Publication Oct 30 2008 Sheet 1 of 3 US 2008 0269589 A1 FIG 1 Patent Application Publication Oct 30 2008 Sheet 2 of 3 US 2008 0269589 A1 Doppler Module 203 HP 1 Hz r 202 204 205 Re lt a LP 100 Hz ifi Amplifier DC DC 5V 12V FIG 2 DR1 DR2 5V GND Patent Application Publication Oct 30 2008 Sheet 3 of 3 US 2008 0269589 A1 FIG 3 A s A ne dejddoan jp eiddoanp 39 US 2008 0269589 Al APPARATUS FOR THE DETECTION OF HEART ACTIVITY 0001 The invention relates to a method to detect mechani cal heart activity of an individual using doppler radar com prising transmitting an electromagnetic signal of a certain frequency into and detecting a reflected signal from out of the chest of the individual and processing the detected signal to produce an output signal representing the rate of change of the doppler signal associated with the reflected signal the rate of change with respect to time 0002 The use of frequency modul
21. mixer diode can be used for the calculation of rate of change 0036 It was found that the whole assembly is sensitive enough to process signals that are reflected by the heart 0037 Experimental results show that the positioning of the transducer relative to the heart is important in detecting a useful signal The electromagnetic signals must be reflected from the heart itself in order for mechanical heart information to be encoded in the reflected signals However it is found experimentally that individual variation between subjects alters the correct position or positions of the transducer in respect of optimal signal detection for each individual How ever if both the detected and output signals are visually displayed on a display screen it is possible to see if the transducer is correctly placed If the transducer is placed in such a way that the heart is not in the emitted beam of signals or is not reflecting the emitted signals back to the receiver US 2008 0269589 Al little or no cyclical activity will be seen in the reflected beam If the transducer is well positioned a cyclical signal will be seen A certain amount of experimentation is required in the correct positioning of the transducer on the surface of the chest of the individual before a suitable signal and therefore the correct position identified It has been found that arrang ing the sensor so that the emitted beam impinges on a plane structure predominantly parallel to
22. ng an electromag netic signal into the chest of an individual which is then reflected back from any internal organs in its path The elec tromagnetic signal becomes doppler shifted in the event that a reflecting organ is moving relative to the transducer This doppler shifted signal is detected by the transducer and when visually displayed shows a cyclical behavior representative of heart activity However if this signal is processed by a pro cessor to produce the rate of change of the signal with respect to time it is found that this outputted signal contains informa tion which allows information about mechanical heart activ ity to be extracted from the further signal 0009 Specifically the further signal contains cyclically occurring features and surprisingly when the further signal is compared to a trace from an impedance cardiogram it can be seen that equivalents of characteristic points found on the trace of the impedance cardiogram can be identified on the further signal allowing parameters such as pre ejection period and left ventricular ejection time which are normally calculated using the impedance cardiogram to be calculated using the outputted signal Therefore information represent ing mechanical activity of the heart can be extracted from the outputted signal and parameters can be calculated which pro vide a measure of mechanical heart activity The method requires no impedance cardiogram to be performed and yet still all
23. ows the same parameters to be calculated Equipment to perform the method is easier to use requiring simple place ment of the transducer against the chest and is therefore more suitable for repeated measurement of heart activity and is correspondingly more suited to repeated measurements for example in patient monitoring 0010 The invention also relates to a system to detect mechanical heart activity of an individual using doppler radar comprising a transducer to transmit electromagnetic signals of a certain frequency into and detect reflected signals from out of the chest of the individual a first computer processor coupled to the transducer to process the detected signal to produce an output signal representing the rate of change of the doppler signal associated with the reflected signal the rate of change with respect to time a second computer processor arranged to identify from the output signal a group of at least one characteristic point of the output signal and a third com puter processor arranged to calculate at least one parameter representative of heart activity the calculation based on the at least one identified characteristic point This system has the advantage that it allows the method of the invention to be performed over multiple devices and thereby provide maxi mum flexibility in assessing the mechanical activity of the heart of an individual The computer processors can be situ ated within the same computer or be
24. pulses is very short in comparison with the time it takes the heart to beat once In the later case each pulse encodes some fraction of the information available in each heart beat about the heart activity In the case where a train of very short pulses with a very short time interval are used the information encoded in the doppler shifted reflected signals represents a sampling of information from the heart 0023 The apparatus of the invention can be used with a transducer arranged to produce electromagnetic signals of frequency in a range of between 400 MHz and 5 GHz This range produces reflected signals from the heart However the apparatus works in a particularly advantageous manner when the frequency is in a range of between 800 MHz and 4 GHz 0024 The apparatus is operated advantageously when it emits electromagnetic signals which are of a single fre quency within the limits of conventional operation of elec tromagnetic antenna as will be appreciated by the person skilled in the art US 2008 0269589 Al 0025 The invention is further elucidated and embodi ments of the invention are explained using the following figures 0026 FIG 1 shows a typical trace from an ECG measure ment of the heart 0027 FIG 2 shows a block diagram of the apparatus of the invention 0028 FIG 3 shows the output of the processor which processes the signal detected by the transducer 0029 As is commonly known the heart is the organ wh
25. romagnetic signals and need not comprise the processor which may itself be remote from the wearable apparatus thereby saving space and weight in the wearable apparatus Thus the wearable apparatus has the advantage that it provides output signals to a remote processor which calculates the rate of change of the originally detected signal with respect to time identifies the characteristic points and calculates parameters The remote processor may be physically located in the same room as the individual or may even be located in another room in the same house 0013 The wearable apparatus can be worn by the indi vidual on a strap or a harness or using other carrying means Because the electromagnetic signals can penetrate through cloth and other wearable materials the apparatus can also be carried in a pocket constructed on the clothing of the indi vidual and arranged to be situated in a position where an optimal signal is detected by the transducer 0014 The invention also relates to a processing system for receiving the signal transmitted from a wearable apparatus to detect mechanical heart activity of an individual using doppler radar the system arranged to receive a signal repre sentative of a reflected electromagnetic signal detected from out of the chest of an individual and further arranged to calculate an output signal representing the rate of change of the doppler signal associated with the reflected signal the rate of change wi
26. senting the rate of change of the doppler signal associated with the reflected signal the rate of change with respect to time a second remote computer processor arranged Oct 30 2008 to identify from the output signal a group of at least one characteristic point of the output signal and a third remote computer processor arranged to calculate at least one param eter representative of heart activity the calculation based on the at least one identified characteristic point 0019 The system has the advantage that it allows the ambulatory monitoring of mechanical heart activity using a wearable transducer which emits electromagnetic signals and detects doppler shifted reflections of those signals passes those signals to a series of remote processors and processes those signals to produce a signal representative of mechanical heart activity The remote processors for example may be in the same room as the individual and may even be in the same computer but could be in another room in the same building or separated from each other geographically 0020 This system also has the further advantage that it can be used to provide monitoring of mechanical heart activity using a world wide web service In this case the individual who is monitored wears the transducer in a housing arranged in some way on his or her person as above so that a suitable signal is detected which has been reflected from the heart and the processor which calculates
27. t is utilized in the following way FIG 2 shows a block diagram of the appara tus The doppler transducer 201 is powered by a voltage supply 202 The output of the doppler transducer 201 is pro cessed through a high pass filter 203 a preamplifier 204 and alow pass filter 205 It was found experimentally that the high pass filter 203 should comprise a capacitance of 100 nF anda resistor of 1 MQ as this enabled a faster decay of the signal while removing the DC part of the signal from the doppler module The time constant t of 0 1 s produces a cut off frequency of 1 59 Hz Although the signal being detected is reflected from the heart which beats with a frequency of the order of 1 Hz the attenuation of this first order high pass filter is low enough not to destroy the signal The gain of the preamplifier 204 can be set in a range of 1 to 1000 but it was found that a particularly advantageous gain was 500 To enable sampling an 8 order low pass filter was realized with a cutoff frequency of 100 Hz using operational amplifiers 0035 FIG 1 also shows two output signals DR1 and DR2 from the doppler transducer As is known in the art some commercially available transducers contain two mixer diodes to provide additional information about the direction of movement of the reflecting object However two signals are not necessary for the apparatus to work If such a trans ducer is used to construct the apparatus the reflected signal from either
28. th respect to time identify from the output signal a group of at least one characteristic point of the output signal and calculate at least one parameter representative of heart activity the calculation based on the at least one identified characteristic point 0015 This apparatus has the advantage that it processes the signals from a portable apparatus arranged to detect dop pler radar signals from within the chest of an individual and processes them to produce signals representative of mechani cal heart activity according to the method of the invention 0016 Thus the wearable apparatus in combination with the remote processor together offer a solutions which solves the problem of how to arrange for ambulatory monitoring of mechanical heart activity of the individual 0017 The invention also relates to a system for the ambu latory detection of mechanical heart activity of an individual using doppler radar comprising a transducer to transmit an electromagnetic signal of a certain frequency the transducer positioned so that the doppler radar signal is emitted into the chest of the individual the transducer capable of detecting the reflected signal from out of the chest and further arranged to transmit a signal representative of the detected signal a first remote computer processor arranged to receive the signal representative of the detected signal and arranged to 0018 process the detected signal to produce an output signal repre
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