WO2007141121A1 - Nouveau système de surveillance sans fil - Google Patents

Nouveau système de surveillance sans fil Download PDF

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Publication number
WO2007141121A1
WO2007141121A1 PCT/EP2007/054742 EP2007054742W WO2007141121A1 WO 2007141121 A1 WO2007141121 A1 WO 2007141121A1 EP 2007054742 W EP2007054742 W EP 2007054742W WO 2007141121 A1 WO2007141121 A1 WO 2007141121A1
Authority
WO
WIPO (PCT)
Prior art keywords
frequency
antenna system
sensor
reader
resonant
Prior art date
Application number
PCT/EP2007/054742
Other languages
English (en)
Inventor
Didier Michel
Raymond Ranwez
Original Assignee
Apreco
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 Apreco filed Critical Apreco
Publication of WO2007141121A1 publication Critical patent/WO2007141121A1/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
    • A61B5/0002—Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/12—Supports; Mounting means
    • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
    • H01Q1/2208—Supports; Mounting means by structural association with other equipment or articles associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems

Definitions

  • the present invention relates to the field of monitoring circumstance / situation variables and/or data.
  • One particular application area of the invention is for instance sleep diagnostic and therapeutic.
  • the invention concerns a new type of sensors and a new type of dedicated readers that can be used to control / monitor variables and/or data concerning specific circumstances
  • a sleep diagnostic process is usually made over a full night and concerns the recording and the interpretation of many different types of channels such as: respiratory movement, air flow, body position, eye movements, ECG, EEG, EMG, oxygen saturation, leg activity, respiratory noise, etc.
  • a classical sleep study requires 20 to 40 sensors that are placed on the patient's body and connected to various devices through wires. These processing units carry out the amplification, filtering, analog to digital conversion. The storage, analysis and display are usually performed by a computer.
  • a physician working in a sleep laboratory is always concerned with the patient's comfort in the hospital in order to get a real representation of the sleep at home.
  • the number of wires needed to connect each sensor to the front-end device severely constrains patient's mobility in the bed and could be viewed as a strong bias to the sleep study. This whole sheaf of wires can also induce stress on the sensors and could imply channel disconnection or connector damage.
  • Some systems have been described, where the signal is digitized on the sensor itself, then sent with some kind of a digital transmission (WiFi, RFID, ). These systems imply a power source at the sensor location, in order to amplify and/or filter and/or digitize the original signal.
  • the power source on the sensor means a lot of complications, because of the short lifecycle or the need to recharge.
  • Description of the invention The present invention may be seen as an analog network system transferring the information wirelessly and without mandatory local power supply at the sensor location.
  • the system involves the use of passive wireless units (at least one passive wireless unit working as resonant antenna system with variable resonance frequency, herein referred to as "variable resonance sensors” VRS), sensors (at least one) measuring circumstance / situation variables and/or data, capable to act upon said VRS unit(s), and a dedicated reader monitoring the variable resonant frequency of said VRS unit(s).
  • passive wireless units at least one passive wireless unit working as resonant antenna system with variable resonance frequency, herein referred to as "variable resonance sensors” VRS
  • sensors at least one measuring circumstance / situation variables and/or data, capable to act upon said VRS unit(s)
  • a dedicated reader monitoring the variable resonant frequency of said VRS unit(s).
  • the analog treatment and digital process can be made on the reader side.
  • the invention can involve sensors each related to a physiological activity and a dedicated reader monitoring the variable resonant frequency of several VRS units.
  • the basic idea is to make a resonant antenna system on the sensor side, for which the resonant frequency will vary according to the signal to be measured.
  • One RLC circuit (called “reader") is excited by an alternative source of tension at a frequency close to its resonant frequency.
  • the induced electromagnetic field oscillates at the same frequency.
  • Another RLC circuit (called "sensor") having a resonant frequency close to this of the reader is placed in the electromagnetic field. If the sensor's inductance (the antenna) is correctly positioned (orientation, distance,%), an efficient inductive coupling appears between the 2 circuits. This effect can be monitored in the reader, for instance by measuring the tension at the terminal of the inductance or by measuring the current.
  • the reader or primary circuit (see Fig. 1), is composed of a resistance ⁇ p, a capacitor C p and an inductance ⁇ p.
  • the circuit is excited by an alternative sinusoidal tension generator at an angular frequency ⁇ . The value of the tension over time is:
  • the sensor or secondary circuit (see Fig.1 ) is composed of a resistance Rs, a capacitor C s and an inductance L Sm There is no direct source of tension in the circuit.
  • the two circuit are inductively coupled, with a mutual inductance M. Note that
  • AI k ⁇ / L p L s , Q ⁇ k being the coupling coefficient.
  • the absolute value of the primary current is the modulus of (13):
  • Figure 2 shows a plot of is maximum when the denominator of (14) is
  • T 1_ _ A minimum, i.e. when 1 ⁇ P ⁇ C 1 , J . This occurs for an angular excitation frequency ⁇ 0 , called resonant frequency:
  • the bandwidth A ⁇ of the circuit is defined as the range of frequencies where the current is above ⁇ /T ⁇ (-3dB).
  • the quality factor Q is the ratio of the resonant frequency to the bandwidth:
  • Equation (25) demonstrates that to maximize the influence of the sensor on the reader's current, we can: • maximize the coupling coefficient ( Figures 3 - 4)
  • Figure 5 shows the coupling coefficient of a reader antenna of radius 25cm and a sensor antenna of radius [1..5cm]. Combining (25) and (26), we can plot (Fig. 6 t, ⁇ as a function d, keeping the same parameters as for Fig. 4 and Fig. 5.
  • Equation (11) becomes :
  • Reader and sensor are tuned at the same frequency.
  • the sensor is placed on an object or body. Movements of the object or body affects the coupling coefficient k by modifying the distance reader- sensor or the relative orientation of the 2 antennas.
  • the variations of k engender variations of the current in the reader. These variations (or any other related value) are measured.
  • the mean distance between the reader and the sensor should be chosen where the sensibility is maximum (small movements will produce great signal variation) and signal measurable. In the example presented in Fig. 6 this distance is about 0.5m.
  • Reader tuned, sensor is tuned/detuned at a variable frequency, the frequency being a function of the physiological parameter.
  • the physiological parameter is actually frequency modulating an oscillator which in turn acts on the sensor's basic RLC circuit by short-circuiting (sensor highly detuned) or not (sensor tuned) the capacitor (see Fig 9).
  • the frequency modulated signal is demodulated to extract the physiological signal information.
  • Figure 10 shows an example of electrical schematic for the sensor.
  • the physiological parameter acts on a varicap.
  • the change of value of the capacitor changes to oscillating frequency of the oscillator.
  • the oscillator needs a power source. Since the power required is very low, one can consider several options for the power source:
  • Reader tuned, sensor basically tuned at the same frequency.
  • the physiological parameter affects a component of the RLC circuit, for instance the capacitor.
  • the sensor is thus slightly detuned, the amount of detuning varying with the physiological parameter.
  • There are several ways to measure the sensor detuning on the reader Measuring the amplitude of the current
  • the sensor detuning affects the current in the reader and any other related value (tension, etc) Theses values can be measured.
  • the generator in the reader sweeps a range of frequencies to find the resonant frequency of the sensor.
  • the resonant frequency of the sensor is the frequency for which the current in the reader is minimum.
  • the reader design is more complex. In particular, the reader must stay tuned during the frequency sweep of the generator to achieve a good sensitivity. The reader's RLC circuit characteristics must thus be changed dynamically according to the frequency of the generator.
  • the reader By listening to the sensor's damped resonant frequency The reader charges to sensor's RLC circuit by emitting an oscillating magnetic field close to the sensor's presumed resonant frequency. The generator is then switched off. The sensor will continue to oscillate for some time (depending on the damping factor) at it's own damped resonant frequency. The reader listen to the oscillating magnetic field emitted by the sensor and monitor the frequency.
  • a VRS Variable Resonant Sensor
  • VRU Vehicle Resonant Unit
  • the actimetry function could be either analog or digital.
  • the sensor In the digital way, the sensor is sensitive to an amount of acceleration and triggers when this acceleration is above a certain threshold. In the analog way, it means that the analog data could be proportional to a movement or to the acceleration of a part of the body.
  • Ball-based actimetry, digital (cf. fig.11 )
  • a VRS is placed on a leg.
  • the resonant frequency of the VRU is changed just by switching the VRU's antenna, or by switching a capacitor placed on it by a "classic" ball-based actimeter.
  • the movement can simply be detected by analyzing the amplitude modulation on the reader antennas when a movement occurs.
  • a VRS is placed on a leg.
  • the resonant frequency of the VRU is modified by means of a Varicap itself biased by the piezo sensor.
  • the body position function could be based on the same principle as for the actimetry function.
  • Ball-based body position function A VRS is placed on the patient body (for example on the chest).
  • the VRU's frequency is changed just by switching the VRU's antenna, or by switching capacitors placed on it by a "classic" ball-based body position sensor.
  • the VRU has one frequency per position.
  • Gravity-based body position A VRS is placed on the patient body (for example on the chest).
  • One or more tilt switches change the VRU's frequency.
  • a piezo belt drives a Varicap which in turns changes the VRU's resonant frequency
  • variable capacitor cf. fig. 15
  • the sensor part of the VRS is a capacitor formed inserting a sheet of copper between 2 sheets of foam and an external shield.
  • variable inductor cf. fig. 16
  • An inductor (a coil) is placed around the patient like a belt so that its inductance changes with the respiration movement. This, in turn, changes the VRU's resonant frequency (cf. figure 16).
  • the sensors described here are based on a thermistor, a pressure cannula and on a new mechanical design.
  • Thermistor-based VRS are based on a thermistor, a pressure cannula and on a new mechanical design.
  • a possible implementation is to bias a Varicap, which controls the VRU resonant frequency, by the voltage drop created through the thermistor, the voltage divider being powered with a battery.
  • Other schemes are possible.
  • the pressure sensor can be either a strain gauge or a piezo. They can be placed in the flow (like a Venturi or a device comprising a fine- mesh screen in a tube) or orthogonally to the flow (like a Pitot tube). Both need at least amplification and a battery. The output could then drive a VRU's Varicap. Special mechanical design. The pressure created by the airflow may change the distance between two metallic flaps forming a capacitor which in turn changes the VRU's frequency.
  • the sensors described here detect sounds (like snoring) from the patient.
  • a piezo microphone (or other kind of microphone) is used to get the snoring noise from the patient. This sensor (probably) needs amplification before acting upon a VRU's Varicap. Capacitive snore microphone
  • the sound coming from the patient acts on a metallic plate that vibrates with the sound.
  • This plate could be part of a capacitor that changes the VRU's frequency.
  • EMG Normally, EMG needs differential amplifier. Since the VRS is inherently isolated from any other device, and since the EMG channels do not need to be interconnected (one channel per VRS), a simple amplifier (2 or 3 stages) could be enough to drive a VRU's Varicap and give a valuable signal. This needs a battery.
  • ECG A one-channel ECG could be done like a one-channel EMG
  • This kind of VRS could use a chamber in which the pressure is measured with either a variable capacitor formed by moving metallic plates, or a variable inductor. This capacitor or the inductor can then change the VRU's frequency.
  • the first is to calculate the SpO2 value within the VRS with a microcontroller and to send the calculated SpO2 value (in addition to the plethismographic data) digitally through the VRU.
  • the second option is to send the raw data (Red base line, Red delta, IR base line, and IR delta) in a multiplexed fashion through the VRU, the SpO2 value being calculated on the reader side.
  • the gain of the VRS is the reduced power needed internally since the communication do not need any power.
  • this VRS is very similar to a snore microphone except for the bandpass (longer time constant).

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Molecular Biology (AREA)
  • Biophysics (AREA)
  • Pathology (AREA)
  • Biomedical Technology (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Medical Informatics (AREA)
  • Physics & Mathematics (AREA)
  • Surgery (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Measuring And Recording Apparatus For Diagnosis (AREA)

Abstract

La présente invention concerne un système de surveillance sans fil impliquant l'utilisation d'unités passives sans fil fonctionnant comme un système d'antennes à résonance avec une fréquence de résonance variable (VRS) et un lecteur dédié surveillant la fréquence variable de résonance des unités VRS. L'invention concerne également un nouveau type de capteurs et un nouveau type de lecteurs dédiés qui peuvent être utilisés pour de tels systèmes de surveillance (tels que pour la surveillance des différents canaux pour le diagnostic du sommeil et des analyses thérapeutiques).
PCT/EP2007/054742 2006-06-08 2007-05-16 Nouveau système de surveillance sans fil WO2007141121A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
EP06115155.1 2006-06-08
EP06115155 2006-06-08
EP06123949 2006-11-13
EP06123949.7 2006-11-13

Publications (1)

Publication Number Publication Date
WO2007141121A1 true WO2007141121A1 (fr) 2007-12-13

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PCT/EP2007/054742 WO2007141121A1 (fr) 2006-06-08 2007-05-16 Nouveau système de surveillance sans fil

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7680522B2 (en) 2006-09-29 2010-03-16 Nellcor Puritan Bennett Llc Method and apparatus for detecting misapplied sensors
US8319401B2 (en) 2010-04-30 2012-11-27 Nellcor Puritan Bennett Llc Air movement energy harvesting with wireless sensors
US8428676B2 (en) 2010-03-31 2013-04-23 Covidien Lp Thermoelectric energy harvesting with wireless sensors
CN103456156A (zh) * 2013-09-23 2013-12-18 东南大学 一种工作频率可调的长距离无源无线传感器遥测系统
US8874180B2 (en) 2010-02-28 2014-10-28 Covidien Lp Ambient electromagnetic energy harvesting with wireless sensors
US8968193B2 (en) 2008-09-30 2015-03-03 Covidien Lp System and method for enabling a research mode on physiological monitors
US9078610B2 (en) 2010-02-22 2015-07-14 Covidien Lp Motion energy harvesting with wireless sensors
US9415125B2 (en) 2012-05-02 2016-08-16 Covidien Lp Wireless, reusable, rechargeable medical sensors and system for recharging and disinfecting the same
CN107317487A (zh) * 2017-08-31 2017-11-03 鲁东大学 一种基于谐振电路的开关电源电磁辐射屏蔽装置
CN110461214A (zh) * 2017-03-09 2019-11-15 皇家飞利浦有限公司 测量身体中的性质

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3958558A (en) * 1974-09-16 1976-05-25 Huntington Institute Of Applied Medical Research Implantable pressure transducer

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3958558A (en) * 1974-09-16 1976-05-25 Huntington Institute Of Applied Medical Research Implantable pressure transducer

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7680522B2 (en) 2006-09-29 2010-03-16 Nellcor Puritan Bennett Llc Method and apparatus for detecting misapplied sensors
US8968193B2 (en) 2008-09-30 2015-03-03 Covidien Lp System and method for enabling a research mode on physiological monitors
US9078610B2 (en) 2010-02-22 2015-07-14 Covidien Lp Motion energy harvesting with wireless sensors
US8874180B2 (en) 2010-02-28 2014-10-28 Covidien Lp Ambient electromagnetic energy harvesting with wireless sensors
US8428676B2 (en) 2010-03-31 2013-04-23 Covidien Lp Thermoelectric energy harvesting with wireless sensors
US8319401B2 (en) 2010-04-30 2012-11-27 Nellcor Puritan Bennett Llc Air movement energy harvesting with wireless sensors
US9415125B2 (en) 2012-05-02 2016-08-16 Covidien Lp Wireless, reusable, rechargeable medical sensors and system for recharging and disinfecting the same
CN103456156A (zh) * 2013-09-23 2013-12-18 东南大学 一种工作频率可调的长距离无源无线传感器遥测系统
CN110461214A (zh) * 2017-03-09 2019-11-15 皇家飞利浦有限公司 测量身体中的性质
CN107317487A (zh) * 2017-08-31 2017-11-03 鲁东大学 一种基于谐振电路的开关电源电磁辐射屏蔽装置

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