WO2007040505A1 - Dispositif de capteurs physiologiques - Google Patents

Dispositif de capteurs physiologiques Download PDF

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Publication number
WO2007040505A1
WO2007040505A1 PCT/US2005/034563 US2005034563W WO2007040505A1 WO 2007040505 A1 WO2007040505 A1 WO 2007040505A1 US 2005034563 W US2005034563 W US 2005034563W WO 2007040505 A1 WO2007040505 A1 WO 2007040505A1
Authority
WO
WIPO (PCT)
Prior art keywords
heart rate
wearer
sensors
monitoring system
waist
Prior art date
Application number
PCT/US2005/034563
Other languages
English (en)
Inventor
James E. Dotter
David J. Farrell
James A. Gilbert
Original Assignee
Cardio Technologies Llc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cardio Technologies Llc filed Critical Cardio Technologies Llc
Priority to PCT/US2005/034563 priority Critical patent/WO2007040505A1/fr
Publication of WO2007040505A1 publication Critical patent/WO2007040505A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
    • A61B5/024—Detecting, measuring or recording pulse rate or heart rate
    • A61B5/02438—Detecting, measuring or recording pulse rate or heart rate with portable devices, e.g. worn by the patient
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/683—Means for maintaining contact with the body
    • A61B5/6831—Straps, bands or harnesses

Definitions

  • the present invention relates generally to a sensor device for measuring heart rate during exercise and displaying this information for the user, and more particularly to an 5 improvement relating to the position of the sensor and to algorithms related thereto.
  • ECG electrocardiogram
  • portable or ambulatory ECG equipment has been developed that allows a doctor to monitor a patient's ECG signal over an extended period of time o while the patient is away from the doctor's office, clinic, or hospital.
  • Such devices may sense and transmit ECG signals through a telecommunications link to the doctor or may record the ECG signals in memory associated with the portable equipment for subsequent evaluation by the doctor.
  • these portable devices typically include twelve or more electrodes and they are utilized to diagnose heart disease. 5
  • a heart rate monitor such as those marketed by Polar Electro OY of Finland.
  • Typical heart rate monitors sold by Polar and other manufacturers are relatively simple devices to operate and are designed for use by an individual without assistance from any medical o professional and without any training.
  • Such a heart rate monitor typically includes a strap that is fastened around the chest of the user, in the vicinity of the user's heart.
  • the strap includes a pair 'of sensors, one located on the left side and one on the right side of the user's breastbone or sternum.
  • the signals from the two sensors are passed. through a passive filter in the strap and provided as inputs to a differential amplifier also located in the strap. From there, the signals are coupled to a receiver and display device typically worn on the user's wrist in a design that looks much like a wristwatch.
  • the strap For female users, there is the issue of the strap interacting with the women's bra or other undergarments, hi addition, for certain exercisers that are breathing heavily, the strap may be uncomfortable to the extent it constricts the user's chest. Further, to properly position or remove the chest strap, a user may find it necessary to remove their shirt, "which may not be desirable in certain situations.
  • a broad objective of the present invention is to provide an improved heart rate monitoring device for individuals to use in monitoring their exercise level. Another objective of the present invention is to improve the comfort of users wearing heart rate monitors. Another objective is to provide reliable heart rate data while maintaining this improved level of comfort.
  • a heart rate monitoring system is provided for use by a wearer in monitoring the wearer's heart rate, the wearer having a body with skin, a waist, and a centerline dividing the body into a right side and a left side.
  • the system includes a belt that fits .
  • a plurality of sensors retained within the belt in a position to be held against the wearer's skin, each sensor sensing the voltage 5 potential of the portion of the skin that sensor is in contact with, there being at least one sensor positioned on the left side and at least one sensor positioned on the right side of the ⁇ wearer's body; and electronic devices receptive of the sensed voltage potentials from the plurality of sensors and operative to determine a heart rate of the wearer.
  • the waist of the wearer may include an area on the wearer's body including and o extending between a point below the rib cage and a point at or above the hip region.
  • the system may further include a display device worn on the wearer's wrist that displays the determined heart rate.
  • the plurality of sensors may include a pair of sensors, each located on the back of the wearer proximate to a portion of the wearer's kidneys, each located on the sides of the wearer proximate to a portion of the wearer's ilium bones, or each located 5 on the front of the wearer along the wearer's front abdominal area.
  • the electronic devices may be located within the belt.
  • the system may further include a remote device that is located at a spaced apart position from the wearer that receives the heart rate determined by the electronic devices.
  • the system may further include a wireless communication link between the electronic devices and the remote o device.
  • the remote device may include a display device to display the determined heart rate.
  • the remote device may include a data storage device to store the determined heart rate.
  • Another aspect of the present invention relates to a method of monitoring a heart rate of an individual.
  • the method includes providing a belt having a plurality of sensors 5 thereon which can sense the voltage potential of human skin that is proximate to the sensors; positioning the belt on the waist of the individual in a position so that at least one sensor is positioned on the left side of the individual and at least one sensor is positioned on the right side of the individual; sensing the voltage potentials of the portions of skin proximate to the sensors; and determining the heart rate of the individual from the sensed o voltage potentials .
  • the method may further include displaying the determined heart rate, passing the determined heart rate information to a remote device that is located at a spaced apart position from the wearer, and/or storing the determined heart rate in a data storage device.
  • the determined heart rate may be passed to the remote device via a wireless communication link.
  • Figure 1 is a front view of portions of a user's body with the heart rate monitoring system of the present invention located thereon.
  • Figure 2 is a front view, similar to that of Figure I, showing possible areas on the user's body where the sensors of the heart rate monitoring system could be located.
  • Figure 3 is a pair of side views of a user's body, showing additional possible areas on the user's body where the sensors of the heart rate monitoring system could be located.
  • Figure 4 is a rear view of a user's body, showing additional possible areas on the user's body where the sensors of the heart rate monitoring system could be located.
  • FIG. 5 is a block diagram view of portions of the heart rate monitoring system of the present invention, showing the major components in the waist belt and the display device.
  • Figure 6 is a block diagram view of portions of the heart rate monitoring system of the present invention, showing the major components in the waist belt and the remote device.
  • Figure 7 is a representation of an electrical signal measured on the body representative of signals that drive the heart muscles, with the magnitude of the electrical signal being plotted versus time.
  • FIG. 8 is a flowchart of logic in a lead off detection algorithm associated with the heart rate monitoring system of the present invention.
  • DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Reference will now be made to the accompanying drawings, which assist in illustrating the various pertinent features of the present invention.
  • the present invention will now be described primarily in conjunction with a heart rate monitor having a plurality of sensors on a belt, it should be expressly understood that the present invention may be applicable to other applications where it is required/desired to measure electrical signals on the skin of a wearer.
  • the following description of a heart rate monitor is presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein.
  • a heart rate monitoring system of the present invention is shown as worn by a user 22 in Figure 1.
  • the system includes a belt 24 that senses electrical signals on the skin of the user and determines the heart rate of the user therefrom. This heart rate information is then communicated to a display device 26 worn on the wrist of the user 22.
  • the belt 24 is worn in a position on the waist 28 of the user 22.
  • the waist 28 of the user 22 is . defined to include a region including and between a point at the bottom of the user's rib cage and the user's hip region.
  • the heart rate information can be communicated to a remote device 30 not located on the user 22.
  • the belt 24 includes a pair of electrical sensors 36 and 38 as shown in Figure 1.
  • the sensors 36 and 38 may be located on the belt 24 in a position to be placed proximate to an area of the user's body containing the user's kidneys. This is shown in Figure 4 by areas 40 and 42 on the back of the user's waist. Note that this position would place the sensors 36 and 38 on opposite sides of the user's backbone. Alternatively, those sensors 36 and 38 on the belt 24 maybe positioned on opposite sides of the user's waist 28 in areas 40 and 42 so as to be proximate to the ilium bones that are a part of the user's pelvic bones, as shown in Figure 3.
  • the sensors 36 and 38 on the belt 24 may be positioned to be on the front of the user's waist 28 in areas 40 and 42, on opposite sides of the user's navel 50, as shown in Figure 4.
  • the sensors 36 and 38 could be composed of any suitable, flexible, conductive material, such as the sensor materials 5 currently used in heart rate monitors marketed to individual users, such as those sold by Polar Electro OY, Nike, and Timex. In some cases, these electrode materials are believed to include a multitude of electrically-conductive spherical beads that are retained in the strap or belt for positioning near the user's skin and having a standard conductive electrode on an opposite side thereof. 0 Components of the system are illustrated in block diagram form in Figure 5.
  • the belt 24 contains the sensors 36 and 38, which provide an electrical signal to a passive filter 60 that provides a filtered output to a differential amplifier 62.
  • the differential amplifier provides an output to a processor 64, which in turn provides a signal to an output device 66.
  • a battery 68 located within the belt 24 powers each of the 5 differential amplifier 62, the processor 64, and the output device 56.
  • An electromagnetic signal 69 is passed between the output device 66 of the belt 24 and an input device 70 of the display device 26.
  • the input device70 provides a signal to a display 72 that displays heart rate information on the display device 26.
  • the display device 26 also includes a user control device 74 that provides signals to the display 72 to o select/control operational modes and what type of information is displayed on the display 72.
  • a battery 76 provides power to the input device 70, the display 72, and optionally to the user control devices 74.
  • the electromagnetic signal could be passed to the remote device 30 ( Figures 1 and 6) 5 which may include other equipment such as a receiver and which may be stationed adjacent to or as part of a treadmill or other stationary exercise device such as a bicycle trainer, a running track, playing field, tennis or basketball court, or the like.
  • the remote device can include an input device 78 which may be similar to the input device 70, a display 80, a user control device.82, a battery 84 (or a connection to an o AC power source), and a data storage device or memory 86.
  • the data storage device 86 may include any suitable form of memory including magnetic, electronic, or optical, or combinations thereof, including compact flash memory, smart cards, memory ICs, and so forth.
  • the information relating to the heart rate could be stored in the belt 24 for later download to other equipment.
  • the output device 66 of the belt 24 and the input device 70 of the display device 26 may communicate via an RF transmitter, receiver, and associated antennas or they may communicate by magnetically coupling together the two circuits via a relatively low frequency magnetic field in the range of 5 kHz. hi the latter case, large coils could be used to provide the magnetic coupling.
  • a representation of the electrical signal from the heart is shown in Figure 7.
  • the electrical signal 90 is shown plotted versus time.
  • the electrical signal 90 includes several characteristic features that are repeated on a periodic basis. These features have been given standard names in the science of electrocardiography. For example, one portion of the signal is known as the P wave 92. A second portion of the signal is known as the Q wave 94.
  • The. Q wave 94 is followed by the R wave 96, which is followed by the S wave 98 and the T wave 100.
  • the combination of the Q wave 94, R wave 96, and S wave 98 are referred to as the QRS complex, hi Figure 7, some elapsed time is represented between the first series of the P wave 92 through T wave 100 and a second series of a P wave 92 through T wave 100.
  • It ⁇ is the amount of total elapsed time between identical portions of the electrical signal that can be used to determine the heart rate. For example, the elapsed time from one R wave
  • the QRS complex of the electrical heart signal typically occurs in approximately 65 milliseconds, which corresponds to a frequency of approximately 15 Hz.
  • Bandpass filtering can be used to remove electrical signals significantly above or below this 15 Hz range and this can eliminate a good deal of the noise.
  • Either the passive filter 60 or the processor 64 could perform this bandpass filtering.
  • Signals that are filtered out include those related to motion artifact, power line inductive or capacitive coupling, DC or baseline electronics wander, muscular activities, thermal noise and galvanic action noise from two dissimilar materials in contact.
  • This first noise source is low frequency noise as 5 a result of the imperfect connection between the skin and the electrode sensors, while the characteristics of the last noise source depend upon the material choices and construction of the electrode.
  • noise sources are not completely characterized, at a minimum there are internal sources of noise such as signals internal to the human body, there are external sources of noise such as fluorescent lights or other l o electrical equipment operating nearby, and there is circuit noise associated with the heart rate monitoring system itself.
  • next heartbeat will not happen sooner than a particular time after the last beat or before a certain longer time after the last beat.
  • the opening and closing of the window around the next anticipated heartbeat is not necessarily symmetrical because it has been determined that the heart rate
  • the time window can be adaptive in that the size of the window is increased or decreased depending on the measured heart rate. In this manner, certain noise and spurious signals can be ignored.
  • One source of these spurious signals may be interruptions and interference related to the environment, ambience (e.g., nearby power lines, automobiles, other athletes, and the like), and actions of the user.
  • a rolling average is a means of filtering, there will be some adjustment to make the window larger just due to the larger number of beats that the heart rate is filtered across.
  • Another signal processing technique that has been- determined to be useful in the heart rate monitoring system of the present invention is delaying transmission of the measured heart rate to allow for correction methods. This allows an algorithm in the microprocessor 64 to look at a series of actual beats and determine, based on a rolling average, whether heartbeats have been missed which should be inserted, or whether erroneous heartbeats have been detected which should be removed. Once these error corrections have been made, then transmission to the display device 26 (or remote device 30) can occur. Of course, there is a delay in the reporting of the data so the data being displayed is somewhat stale, but it is believed that this particular disadvantage is more than offset by obtaining a more accurate heart rate.
  • the rolling average together with the known maximum rate of change of the inter-beat timing, can be used to determine when a beat has been missed or an erroneous beat has been detected. It has also been determined that another signal processing technique is desirable as part of the heart rate monitoring system of the present invention.
  • a circuit is devised that can raise an alarm when one of the sensors 36 and 38 touching the skin is removed from the skin. This may be a temporary dislocation, or it may be a more permanent dislocation in which the user has removed the waist belt 24. In the case of a temporary dislocation, it is desirable to continue monitoring the heart, and to infer the behavior of the heart during the time that the sensor is off of the skin, based on recent history.
  • An algorithm is devised to continue reporting inferred heartbeats for a period of time, in anticipation that the sensor(s) will be replaced and heart rate monitoring will be continued. This eliminates momentary disruptions of heart rate reporting to the user, and maintains a more realistic record of heart rate activity for later review.
  • the detection of the sensor being off the skin is performed by detecting the impedance of each sensor relative to the other sensor or to circuit ground. With a DC current, this may be approximately 1 k ⁇ or with an AC current, this may be in the range of 50 ⁇ . If this impedance is greatly exceeded, the system can realize that the sensor is off the skin.
  • the flowchart of Figure 8 shows the logic performed by the algorithm 110.
  • the 5 algorithm 110 is only performed when one of the sensors is detected (112) to be off of the user's skin.
  • a timer is started (114) and the last good heart rate value continues to be reported.
  • a test is performed (116) to see if the timer has expired. If the timer has not expired, then another test is performed (118) to see if the sensor is back on the skin. If the answer is yes, then the algorithm returns (120) to normal monitoring. If the 0 answer to the test performed (118) is no, then the processing returns to the test (116) which determines if the timer has expired. If the timer has expired, then monitoring is ended (122).
  • Another signal processing technique that has been discovered to be useful with the heart rate monitoring system of the present invention is automatically adjustable . gain. It 5 has been discovered that the strength of the electrical signal varies greatly depending on the location on the user's body and that the strength of the electrical signal varies greatly from user to user.
  • the adjustable gain circuit initially searches for a usable electrical heart rate signal across a wide range of signal levels. Once a signal is identified, the detecting circuit can be fine tuned to the specific signal strength in an adaptive manner in order to o provide a more reliable reporting of the heart rate.
  • the optimal position for a heart rate monitoring system would be where the signal is strongest, on the chest. For reasons other than signal quality, the inventors have been motivated to. place the sensors at the waist portion. It is believed that no one else has previously been motivated to measure heart rate at this sub-optimal position, hi fact, it is believed that all prior art taught away from placing the sensors at any sub-optimal 0 position.
  • One possible scenario for use of the heart rate monitoring system of the present invention is that a user could wear the belt 24 on their waist for certain exercises and on their chest for other exercises.
  • the fact that certain signal processing techniques have been used to extract a degraded signal at the waist location does not prevent operation of 5 the system on an area of the chest where the signal is not so degraded.
  • the sensors are on opposite sides of a plane running longitudinally through the user's body parallel to the spine and intersecting the navel (dividing the body into left and right sides corresponding to one's left and right hand) because of the nature of the electrical signals conducted through the body. It is o generally believed that the wavefront of the signal on one side of the body emanating from a node in the heart is out of phase with the wavefront of the signal on the other side of the body emanating in an opposite direction from the heart node. For this reason, it is believed that little to no signal would be available if those sensors were placed on the same side of the plane or centerline while a stronger signal can be obtained if the 5 measurement is made from opposite sides of the centerline.
  • the heart rate monitoring system of the present invention would work suitably with sensors placed nearly anywhere on the body as long as there is one on each of the two sides of the body, hi the waist region, this could include any combination of one sensor anywhere on the waist on the left side of the body and a second sensor o anywhere on the waist on the right side of the body.
  • sensors on the front of the waist are not as effective as those on the side or back of the waist, particularly if the user is overweight with a large belly that may cause intermittent disruption of the signal because the sensors are bounced around too much.
  • ADC can.be useful, because it reduces the signal processing and adaptive gain requirements of the front end. More can be done algorithmically (digitally) within the processor or an integrated circuit.
  • the advantages primarily relate to the location of the sensor strap around the waist portion of the user's body. This position provides comfort, convenience, and . aesthetic improvements.
  • the familiarity of a waist belt as opposed to a chest strap is also a benefit to many users.
  • the advantages also include enhanced breathability of the wearer/athlete (especially during maximal effort), reducing chafing (especially relative to arm movement during running), and a more natural and familiar location for a constricting device which will probably be indistinguishable from the elastic in the athlete's shorts or pants.

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biomedical Technology (AREA)
  • Molecular Biology (AREA)
  • Veterinary Medicine (AREA)
  • Biophysics (AREA)
  • Pathology (AREA)
  • Engineering & Computer Science (AREA)
  • Cardiology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Medical Informatics (AREA)
  • Physics & Mathematics (AREA)
  • Surgery (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Physiology (AREA)
  • Measurement And Recording Of Electrical Phenomena And Electrical Characteristics Of The Living Body (AREA)
  • Measuring Pulse, Heart Rate, Blood Pressure Or Blood Flow (AREA)

Abstract

L'invention concerne un système de surveillance de fréquence cardiaque pour une utilisation dans l'entraînement sportif et de culture physique qui comprend une ceinture de capteurs portée à la taille de l'utilisateur et un dispositif d'affichage porté au poignet de l'utilisateur. La ceinture de capteurs a une paire de capteurs qui peuvent être situés sur des côtés opposés du corps dans des emplacements variés, tels que près des reins, près des os iliaques dans le bassin ou sur la zone abdominale avant de l'utilisateur. Diverses techniques de traitement de signal sont employées pour extraire le signal dégradé qui est disponible au niveau de la zone de la taille par comparaison à la zone de la poitrine. Ces techniques de traitement de signal comprennent le filtrage de bande passante, une fenêtre temporelle adaptative, une transmission retardée pour prévoir des procédés de correction tels que le remplacement d'un battement manquant et la suppression de battement supplémentaire, un algorithme de détection et de réglage de première frappe, une commande de gain réglable automatiquement, et une détection et une caractérisation de formes d'onde.
PCT/US2005/034563 2005-09-26 2005-09-26 Dispositif de capteurs physiologiques WO2007040505A1 (fr)

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PCT/US2005/034563 WO2007040505A1 (fr) 2005-09-26 2005-09-26 Dispositif de capteurs physiologiques

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2005/034563 WO2007040505A1 (fr) 2005-09-26 2005-09-26 Dispositif de capteurs physiologiques

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WO2007040505A1 true WO2007040505A1 (fr) 2007-04-12

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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005032365A1 (fr) * 2003-10-03 2005-04-14 Mega Elektroniikka Oy Technique de reconnaissance de debit cardiaque et de calcul de quantite a partir de celui-ci

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005032365A1 (fr) * 2003-10-03 2005-04-14 Mega Elektroniikka Oy Technique de reconnaissance de debit cardiaque et de calcul de quantite a partir de celui-ci

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