WO2005062924A2 - Transducteur pour convertir des pulsations de battements cardiaques en signal electrique - Google Patents

Transducteur pour convertir des pulsations de battements cardiaques en signal electrique Download PDF

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Publication number
WO2005062924A2
WO2005062924A2 PCT/US2004/043296 US2004043296W WO2005062924A2 WO 2005062924 A2 WO2005062924 A2 WO 2005062924A2 US 2004043296 W US2004043296 W US 2004043296W WO 2005062924 A2 WO2005062924 A2 WO 2005062924A2
Authority
WO
WIPO (PCT)
Prior art keywords
membrane
transducer according
pulsations
transducer
gas
Prior art date
Application number
PCT/US2004/043296
Other languages
English (en)
Other versions
WO2005062924A3 (fr
Inventor
David W. Gerdt
Martin C. Baruch
Charles M. Adkins
Original Assignee
Empirical Technologies Corporation
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 Empirical Technologies Corporation filed Critical Empirical Technologies Corporation
Publication of WO2005062924A2 publication Critical patent/WO2005062924A2/fr
Publication of WO2005062924A3 publication Critical patent/WO2005062924A3/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
    • A61B5/02444—Details of sensor
    • 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

Definitions

  • This invention is concerned with transducers for converting mechanical pulsations into an electrical signal.
  • One environment in which the invention is useful is physiological monitoring of the states of health, fatigue and mind of military personnel, emergency rescue personnel, and so-called first responders, for example.
  • the invention provides a sensitive device that produces an electrical signal in response to heartbeat pulsations, for, example.
  • the invention employs a wrist- mounted case or housing in which slightly pressurized gas, preferably air, is confined in a chamber between a pair of flexible walls, one of which is a high compliance follower membrane that senses the heartbeat pulse signature and the other of which is a piezoelectric membrane. Heartbeat pulsations applied to the follower membrane are transferred to the piezoelectric membrane through pressure oscillations in the air, serving as a coupling medium.
  • two chambers containing gas, preferably air are wrist-mounted at separate locations.
  • a first chamber has a wall constituted by a piezoelectric membrane and is contained in a case positioned on a wrist, like a watch.
  • a second chamber has a wall constituted by a compliant follower membrane exposed to heartbeat pulsations, and is mounted on a band attached to the case, like a watch band.
  • the two chambers are connected by tubing that transfers heartbeat pulsations from the second chamber to the first chamber via air in the tubing, serving as a coupling medium.
  • Both embodiments preferably employ electronics including, for example, an amplifier with a high input impedance stage to convert the current output of the piezoelectric membrane to a voltage, and a voltage amplifier stage to produce an output signal that can be displayed locally or at a distance.
  • Fig. 1 is a diagrammatic sectional view of a first embodiment of the invention
  • Fig. 2 is a circuit diagram of an amplifier for use in the invention
  • Fig. 3 is a perspective view of a second embodiment of the invention
  • Fig. 4 is a diagrammatic sectional view of a first unit employed in the second embodiment
  • Fig. 5 is an exploded view showing components of the first unit
  • Fig. 6 is an exploded view showing components of a second unit of the first embodiment.
  • a pulse sensing transducer in accordance with a first embodiment of the invention includes two main components mounted in a suitable case or housing.
  • a first component is a very low durometer high compliance follower membrane, preferably silicone, anchored at its perimeter.
  • the follower membrane is disposed near a radial artery on the wrist, at a pulse palpation point, to sense the heartbeat pulse signature and transfer it to the second component, a piezoelectric membrane, via a gaseous coupling medium, preferably air.
  • a gaseous coupling medium preferably air.
  • the low stiffness of the follower membrane and the low inertia of the air coupling medium allow the palpations of the artery to be transferred efficiently to the piezoelectric membrane. It appears that the air coupling medium acts as an incompressible piston with almost no inertia. Since the velocity of transferred pulsations is very low, there is very low frictional loss and essentially no viscosity and no turbulence in the coupling medium.
  • the acoustic signature of the heartbeat pulse resides in frequencies above its fundamental (near 1 Hz) and has useful content out to about 15 Hz.
  • the energy is mostly contained in the fundamental frequency at the conventional pulse rate.
  • the identification of this frequency bandwidth is useful in determining sample rates and collection times that may be required by various analytical techniques.
  • the displacement of the follower membrane transfers the motions associated with the heartbeat pulses into pressure oscillations in the coupling gas. At the low frequencies contained in the pulse and breathing signatures, there is essentially no distortion due to inertial or acoustic phenomena, and the displacement of the follower membrane directly correlates to pressure at the piezoelectric membrane .
  • the piezoelectric membrane is preferably a piezopolymer film, such as PVDF, having electrodes (e.g., silver) on opposite sides of the film.
  • the piezoelectric membrane may be circular with a diameter about the same as a dime, or rectangular, for example.
  • the membrane is anchored at its perimeter and is sensitive whether or not there is a differential pressure between the opposing sides of the membrane. However, it is preferred to establish a differential pressure between the sides of the membrane to put the membrane in elastic tension. The differential pressure is produced by slightly pressurizing the air between the membranes. Once a static elastic deformation of the piezoelectric membrane is reached, electrical charge accumulates on one face of the membrane for deformation caused by increases in the pressure differential.
  • This charge can be used to produce a current in proportion to the stressing of the stretched piezoelectric membrane.
  • Pressure oscillations in the air coupling medium are converted into strain oscillations in the piezoelectric membrane, which are converted to current oscillations that can be measured.
  • the volume of gas between the follower membrane and the piezoelectric membrane is preferably pressurized to of the order of 1 to 2 psi, which is sufficient to cause bulging of the membranes (spherical in the case of a circular membrane) . In the absence of pressurization, a membrane is not appropriately stretched and can deform permanently in very small amounts.
  • Pressure oscillations can cause some parts of the membrane to move in one direction while other parts move in another, which can wash out a signal from a piezoelectric membrane. Moreover, slight movements of the hand or body can cause the membrane to flap, creating artifact signals that degrade the signal- to-noise ratio.
  • a device that converts the current to a voltage and then to amplify that voltage. In the invention, it is preferred to use a transimpedance amplifier that inputs current and outputs voltage, followed by a voltage amplifier.
  • the transimpedance configuration clamps the voltage on the piezoelectric membrane to zero and gives an output proportional to the current produced by the movement of the charge produced piezoelectrically.
  • the output is proportional to the rate of strain in the piezoelectric membrane, which is the time derivative of its displacement.
  • a modification of the transimpedance design can include an integrating capacitor in the feedback path of the amplifier. This sets a low frequency break point and allows the integration of signals in the passband of the amplifier. If the break point is set about 1 decade below the pulse fundamental, the output is purely a pressure pulse, but the settling time to sudden inputs is slow (about 10 sec), If the break point is set about 1 decade above the pulse fundamental, the output is purely derivative pulse, and the settling time is rapid (about 0.1 sec). If the break point is set at the pulse rate, both signals are down 3 dB, and the output is a mixture of the two signals. The choice of signal type is a function of its use.
  • Fig. 1 shows, somewhat diagrammatically, an example of a transducer 10 in accordance with a first embodiment of the invention.
  • the embodiment shown is intended to be wrist-mounted and includes a case 12 about the size of a watch case and a conventional wrist strap 14 (watch band) attached to the case for securing the case to a pulse palpation point on a wrist.
  • a follower membrane 16, shown bulging outwardly, is typically a silicone film about 0.01 inch thick with a SHORE A durometer of about 10 (available from the Rogers Corp.).
  • a volume of air 20 is contained in a chamber between the follower membrane and a piezoelectric membrane 18 and is pressurized to about 1 to 2 psi, for example, by an air pump 22 that can be a simple thumb-operated pump mounted on the transducer device or a pump connected to the air space chamber via tubing. In either case, a one-way valve can be used to admit air and prevent loss of air pressure.
  • the membranes are anchored in the case at their peripheries .
  • a printed circuit board 24 is mounted in the case and provides electronics for processing the current output of the piezoelectric membrane.
  • Fig. 2 shows an amplifier circuit 25 useful in the electronics of the invention and including a transimpedance amplifier as a first stage 28 and a voltage amplifier as a second stage 30.
  • the feedback resistor of the first stage should be as high as possible.
  • the output of the amplifier can be converted to a digital signal that can be processed by a conventional digital signal processor, and the electronics may include a transceiver (or merely a transmitter) for remote communication.
  • An output signal of the electronics can be sampled at an appropriate rate to reduce power requirements.
  • a power supply of the electronics includes a battery 32 mounted on the case, but the battery can be mounted in the case or on the wrist strap, for example.
  • the invention can be used in a single-point blood pressure monitoring system of the type described in co- pending application 10/502,932 filed July 29, 2004, incorporated herein by reference. Other applications of the invention will be apparent to those skilled in the art.
  • Fig. 3 show a second embodiment of the invention, employing two gas-containing chambers connected by tubing. A first chamber is incorporated in a first wrist-mounted unit 34, and a second chamber is incorporated in a second wrist-mounted unit 36. The first unit uses a conventional watch case with certain added components.
  • Fig. 4 shows the complete first unit
  • Fig. 5 is an exploded view of the first unit.
  • the watch case 38 is surmounted by a conventional finger-operated pump 40 that includes a flexible diaphragm 42 with a finger-closed center hole 44 and a one-way check valve 46 for pressurizing a chamber 48, one wall of which is a piezoelectric membrane 50 perimeter- anchored over a center hole 52 of a washer 54. Pressure pulsations are transferred to the chamber 48 of the first unit via tubing 56 connected to the second unit.
  • the first unit 34 may include the valve body 58, a washer/spacer 60, and electronics on a printed circuit board 62, and may have a conventional case back 64.
  • the first unit 34 is wrist- mounted by a watch band strap 66 which also supports the second unit 36.
  • the second unit 36 has a gas-containing chamber connected by the tubing 56 to the first unit.
  • One wall of the chamber is constituted by a high compliance elastomeric follower membrane 68, which, in the form shown, is a silicone membrane of rectangular configuration.
  • the follower membrane is perimeter-mounted between upper and lower rectangular washer/spacers 70,72.
  • the upper spacer 70 abuts a wall 74 with a center opening 76 over which is mounted a sleeve 77 closed by a top wall 78 to form a hollow turret.
  • a stainless steel coupling 80 connects the interior of the hollow turret to the tubing 56 attached to the first unit 34.
  • washer 72 is a 1/8 inch thick silicone stand-off.
  • Membrane 68 is a 0.01 inch thick grey Bisco silicone membrane.
  • Washer 70 is a 0.031 inch thick Bisco silicone member.
  • Wall 74 is a 0.031 in thick Bisco silicone member.
  • Sleeve 77 is a 7/16 x 1/16 inch wall silicone tubing.
  • Wall 78 is a 1/16 inch silicone sheet.
  • Tubing 56 is a 1/8 x 1/16 inch wall silicone tubing.
  • components of the transducer device can be assembled using an appropriate adhesive.
  • the follower membrane 68 bulges from the stand-off 72 to contact the skin of the wrist at a palpation point, so that heartbeat pulsations to which the follower membrane is exposed are transferred through the air column in the tubing 56 to pressurized air contained in the chamber in the first unit, and thereby to the piezoelectric membrane 50.
  • a piezoelectric signal can then be processed as in the first embodiment.
  • the piezoelectric membrane and the electronics are preferably electrically shielded, as in a Faraday cage.
  • the Faraday cage can be constituted from one of the electrodes of the piezoelectric membrane and metallized walls of the chamber containing the electronics.
  • the transducer devices of the invention can be part of a system which may include, for example, a small intermediate transceiver worn on a belt of an individual and a command transceiver with a range of about two miles, for example. Vital physiological variables may be monitored on a periodic (programmed) or queried basis (e.g., from the command transceiver) .
  • the system may include a device for measuring core temperature of an individual and may use GPS for individual location.
  • the invention can be used to provide a continuous physiologic monitor of heart rate, breathing rate, systolic blood pressure, inspiratory effort, heart rate variability, sleep cycles, restfulness of sleep, sleep disorder problems, and respiratory problems, for example.
  • the invention can assist as a triage device, allowing for maximum utilization of medical resources . While preferred embodiments of the invention have been shown and described, it will be apparent that modifications can be made without departing from the principles and spirit of the invention, the scope of which is defined in the accompanying claims .

Landscapes

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

Abstract

L'invention concerne des transducteurs conçus pour convertir des pulsations mécaniques en signal électrique, qui utilisent deux membranes, l'une, une membrane suiveuse exposée aux pulsations, l'autre, une membrane piézo-électrique couplée à la membrane suiveuse par un volume d'air légèrement sous pression. Lesdites membranes peuvent faire partie d'une chambre simple ou de chambres séparées couplées par une colonne d'air. L'invention concerne, par exemple, un transducteur de pulsations de battements cardiaques.
PCT/US2004/043296 2003-12-23 2004-12-23 Transducteur pour convertir des pulsations de battements cardiaques en signal electrique WO2005062924A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US53162403P 2003-12-23 2003-12-23
US60/531,624 2003-12-23

Publications (2)

Publication Number Publication Date
WO2005062924A2 true WO2005062924A2 (fr) 2005-07-14
WO2005062924A3 WO2005062924A3 (fr) 2007-07-26

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103462595A (zh) * 2013-09-22 2013-12-25 天津万合星辰信息技术有限公司 一种便携式传感器组件
CN103680065A (zh) * 2013-11-14 2014-03-26 东莞龙昌数码科技有限公司 一种的疲劳检测仪的反馈器
CN103932685A (zh) * 2014-04-14 2014-07-23 天津万合星辰信息技术有限公司 用于检测人体节律振动的传感器
CN110292368A (zh) * 2019-06-25 2019-10-01 浙江大学 具备测量点位置容错性能的血压柔性传感器

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5450852A (en) * 1993-11-09 1995-09-19 Medwave, Inc. Continuous non-invasive blood pressure monitoring system
US5617868A (en) * 1994-11-22 1997-04-08 Colin Corporation Pulse wave detecting apparatus
US6695789B2 (en) * 2002-02-21 2004-02-24 Medwave, Inc. Disposable non-invasive blood pressure sensor

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5450852A (en) * 1993-11-09 1995-09-19 Medwave, Inc. Continuous non-invasive blood pressure monitoring system
US5722414A (en) * 1993-11-09 1998-03-03 Medwave, Inc. Continuous non-invasive blood pressure monitoring system
US5617868A (en) * 1994-11-22 1997-04-08 Colin Corporation Pulse wave detecting apparatus
US6695789B2 (en) * 2002-02-21 2004-02-24 Medwave, Inc. Disposable non-invasive blood pressure sensor

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103462595A (zh) * 2013-09-22 2013-12-25 天津万合星辰信息技术有限公司 一种便携式传感器组件
WO2015039373A1 (fr) * 2013-09-22 2015-03-26 天津万合星辰信息技术有限公司 Ensemble capteur portable
CN103680065A (zh) * 2013-11-14 2014-03-26 东莞龙昌数码科技有限公司 一种的疲劳检测仪的反馈器
CN103932685A (zh) * 2014-04-14 2014-07-23 天津万合星辰信息技术有限公司 用于检测人体节律振动的传感器
CN103932685B (zh) * 2014-04-14 2016-04-13 天津普仁万合信息技术有限公司 用于检测人体节律振动的传感器
CN110292368A (zh) * 2019-06-25 2019-10-01 浙江大学 具备测量点位置容错性能的血压柔性传感器
CN110292368B (zh) * 2019-06-25 2024-02-13 浙江大学 具备测量点位置容错性能的血压柔性传感器

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