WO2014204721A1 - Système de télésurveillance d'évènements physiologiques - Google Patents

Système de télésurveillance d'évènements physiologiques Download PDF

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Publication number
WO2014204721A1
WO2014204721A1 PCT/US2014/041747 US2014041747W WO2014204721A1 WO 2014204721 A1 WO2014204721 A1 WO 2014204721A1 US 2014041747 W US2014041747 W US 2014041747W WO 2014204721 A1 WO2014204721 A1 WO 2014204721A1
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WIPO (PCT)
Prior art keywords
signal
antenna
receive
frequency
transmit
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Application number
PCT/US2014/041747
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English (en)
Inventor
Brian Watson
Daniel Mckenna
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Biozense, Inc.
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Publication date
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Publication of WO2014204721A1 publication Critical patent/WO2014204721A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
    • A61B5/0809—Detecting, measuring or recording devices for evaluating the respiratory organs by impedance pneumography
    • 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
    • A61B5/0205—Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
    • 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
    • A61B5/026—Measuring blood flow
    • A61B5/0265—Measuring blood flow using electromagnetic means, e.g. electromagnetic flowmeter
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves 
    • A61B5/053—Measuring electrical impedance or conductance of a portion of the body
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2503/00—Evaluating a particular growth phase or type of persons or animals
    • A61B2503/02—Foetus
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B2503/00—Evaluating a particular growth phase or type of persons or animals
    • A61B2503/04—Babies, e.g. for SIDS detection
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/22—Ergometry; Measuring muscular strength or the force of a muscular blow
    • A61B5/224—Measuring muscular strength
    • A61B5/227—Measuring muscular strength of constricting muscles, i.e. sphincters

Definitions

  • the present invention pertains to remote, non-contact and noninvasive devices and methods to detect, measure, or monitor physiological processes in animals and humans. More particularly, the invention regards electromagnetic impedance sensors and systems incorporating such sensors used for remote detection of physiological processes such as heartbeat, respiration, muscle contractions, blood flow, and hemorrhaging.
  • the term "remote” is used to indicate activities outside of, and not requiring contact with, the subject body.
  • the average conductivity and relative dielectric constant of the human body are approximately equal to seawater. These parameters vary for each of the organs and tissues. During the cardiac cycle, the volume of blood in each heart chamber varies, producing a periodic change in the electrical conductivity. Movement or deformation of the body tissues during respiration or muscle contractions varies the shape and relative distance between organs and the distribution of blood also creating changes in electrical conductivity.
  • pulse oximetry on a surgical ward is subject to motion artifacts and false alarms, it remains commonly employed to detect
  • hypoventilation the most common complication from post-operative opioid analgesia. Hypoventilation is a particular concern in the obstructive sleep apnea patient. Many hospitals have instituted a modified early warning system with scoring systems, alert algorithms, and response teams, speeding institution of therapy in deteriorating patients. Heart rate and respiratory rate comprise two of the seven scored categories. Alteration in respiratory rate was the most common vital sign change predisposing to cardiopulmonary arrest. Consequently, there is a need for devices and methods for detecting and monitoring physiological events in patients while simultaneously accommodating incidental movement of the patient.
  • Prior fetal monitor heart rate sensors are either ultrasound based or electrode based fetal Electrocardiogram (ECG) sensors.
  • ECG Electrocardiogram
  • Ultrasound-based sensors are extremely directional, prone to signal loss due to misalignment with the baby in the womb, and require constant intervention by a trained operator to maintain a usable signal. Due to insulating properties of the vernix surrounding the fetus in the womb, the electrical signals from the fetal heart are highly attenuated at the skin surface of the mother's abdomen, resulting in extremely weak and noisy fetal ECG signals in electrode-based fetal heart rate monitors, and unreliable fetal heart rate measurements.
  • fetal scalp electrodes screwed into the skin on the baby's head are sometimes used for fetal heart rate measurements in problematic deliveries.
  • the use of fetal scalp electrodes demonstrates that existing conventional non-invasive fetal heart rate sensors are inadequate for accurate and reliable fetal heart rate measurements.
  • Neonatal monitoring especially premature infants, currently requires attachment of electrodes, pulse oximeters, and other sensors.
  • electrodes For premature infants, there is limited area for sensor attachment and their skin is relatively delicate. After delivery, even after the skin is cleaned and prepped, the limited surface available for attachment of electrodes or pulse oximeters in very low birth weight infants can limit monitoring options. It is very difficult to use ECG electrodes for continuous monitoring due to the harshness of electrode paste. Also, intermittent re-attachment of sensors increases the risk of infection and proliferation of antibiotic resistant bacteria. Consequently, there is a need for remote and noncontact devices and methods for detecting and monitoring physiological events in infants.
  • the present invention provides electromagnetic impedance sensors and associated methods to detect, measure, and monitor physiological indicators including, for example, the heart and respiration rate without direct contact with a subject patient.
  • the present invention is particularly, but not exclusively, useful for detecting the onset of respiratory distress in a patient.
  • the sensors and methods are capable of operating in the presence of large intermittent patient motion or external objects including metal objects that may interfere with the
  • An amplified transmit signal drives an excitation antenna, generating a radio frequency magnetic field. This low-power field penetrates the body and leads to a re-induced magnetic field, which is superimposed on the excitation field. Changes in the electrical impedance of the subject body due to physiological processes and events produce corresponding variations in the receive signal that are detected by a receive antenna. This signal is conditioned and analyzed to determine dynamic physiological parameters related to events such as, but not limited to, cardiac activity, respiration, muscle contractions, blood flow, and hemorrhaging.
  • a transmit signal frequency is selected for effective penetration of a subject body.
  • An antenna system is then selected or designed to provide effective transmission and reception of signals of the selected frequency while minimizing reception of the transmit signal in the absence of physiologically-induced impedance changes in the subject body.
  • a signal centered at the selected frequency is projected on the subject body and a receive signal is captured that contains a lower frequency modulation that is the subject signal of interest for measuring or monitoring.
  • An offset signal of adjustable magnitude and opposite polarity may be optionally added to the receive signal to reduce its magnitude until the adjusted receive signal is within a predetermined dynamic range for resolution of subject signals.
  • the ratio between the receive and subject signal amplitudes should be less than 100 dB.
  • the receive signal is mixed with a reference signal and filtered to generate a mixed signal having a lower frequency closer to the subject frequency range.
  • the mixed and reference signals are captured digitally and the subject signals are extracted and analyzed to determine physiological parameters of interest.
  • a system determines if a subject is near the antenna by monitoring the antenna impedance. If a subject is near the antennas, a continuous waveform signal with high amplitude and frequency stability is generated and applied to a patient in proximity to a transmit antenna. A receive signal is modulated by the electrical impedance of the subject, which changes dynamically due to physiological events. A balancing signal of approximately the same magnitude but with opposite polarity is generated by the system and combined with the receive signal to constrain the magnitude of the receive signal. The balancing signal is produced adaptively in response to the real-time events of the subject patient to continuously constrain the magnitude of the receive signal. The receive signal, balancing signal, and transmit signal are monitored as a function of time and analyzed to determine physiological parameters.
  • the system includes an antenna system with integrated electronics that together perform all the required functions. Operational information may be displayed on the integrated system or transmitted in any of a variety of conventional methods to remote locations.
  • One optional form of this configuration is a portable system that may be hand located on a patient's body or otherwise placed as desired depending on the instant application needs.
  • the signal generation and signal processing electronic components are separated from the antenna components and connected via wired or wireless communication components.
  • the antenna components are located in, on or adjacent a subject support surface such as, for example, a chair, a hospital bed or gurney, a medical examination table, or a neonatal bassinette.
  • the invention also includes novel support surfaces and devices, for example a chair, a hospital bed or gurney, a medical examination table, or a neonatal bassinette, that incorporates or is combined with a monitoring system according to the invention.
  • Event detection may be configured to trigger user alarms.
  • the antenna system includes paired transmit and receive antenna elements in conventional magnetic field antenna form, the antenna elements configured to minimize mutual electromagnetic coupling.
  • the coupling requirement is satisfied through other design elements.
  • a transmit frequency in the range of 1 kHertz (1000 cycles per second) to 20 MHertz (20,000 kHertz) is used to provide sufficient tissue penetration and satisfy other operational requirements.
  • the senor design has particular value as compatible with and avoiding interference with implanted medical devices such as pacemakers.
  • the device may also be designed to satisfy regulatory electronic emissions standards.
  • Figure 1 is a schematic illustration of one configuration of a system according to the invention.
  • Figure 2 is a schematic illustration of an embodiment of the invention.
  • Figure 3 is a side view illustration of an inventive combination of a conventional hospital patient support and a patient monitoring system according to the invention.
  • Figure 4 is a side view illustration of an application of the invention in combination with a neonatal child support.
  • Figure 5 is an illustration of a portable configuration of a detecting system according to the invention in an exemplary application.
  • Figure 6 is a schematic illustration of the components of a preferred embodiment of a detecting system according to the invention.
  • Figures 7a and 7b are a flow diagram illustrating the associated operation of the embodiment of Figure 6.
  • FIG. 1 depicts elements of one embodiment of a system according to the invention and the following discussion refers to the elements shown.
  • a signal generator 10 is configured to generate a transmit signal.
  • the signal generator 10 is connected to a transmit antenna 101 .
  • the transmit antenna 101 is configured and located to generate the transmit signal in the proximity of a subject body 106.
  • a receive antenna 102 is located adjacent to the transmit antenna 101 , or may be provided by the same transmit antenna 101 .
  • a receiver 12 is
  • An output device 16 is connected to the signal processor 14 or may be integrated with signal processor 14.
  • the signal generator 10 In operation, the signal generator 10 generates a transmit signal to drive the transmit antenna 101 , generating an excitation radio frequency magnetic field.
  • This low-power field penetrates the subject body 106 and leads to a re- induced magnetic field, which is superimposed on the excitation field.
  • Small changes in the electrical impedance of the body due to movements of small portions of the body (e.g. blood, heart or lung tissue) such as occurring during physiological processes (e.g. blood flow, cardiac movement, respiration) produce a corresponding variation in a receive signal that is detected by the receive antenna 102.
  • This receive signal is received by the receiver 12 and may be optionally conditioned as and if necessary to enable the signal processor 14 to accept and manage the received signal.
  • the signal generator 10 is also connected to the signal processor 14 to provide the transmit signal to the signal processor 14.
  • the signal processor 14 compares the transmit signal with the received signal and, from the differences, determines the timing of events associated with the physiological processes. The event information is then made available to the user or other systems through the output device 16.
  • the system may be beneficially used to detect events such as heart beats or cardio-pulmonary cycles in a human or other animal as the subject of detection.
  • the signal generator 10 and its required output - the transmit signal - is in part specified by the physical characteristics of the subject.
  • An effective frequency is dependent in part on the absorption and other characteristics of the body and the events of interest. For human bodies and similar subjects a frequency in the range of 1 kHertz (1000 cycles per second) to 100 MHertz (100,000 kHertz) is feasible, while a range of 1 MHertz to 20 MHertz is more preferred for practical considerations and a frequency of 3 MHertz has been found most effective.
  • the term "detect” is used generally to describe the operation of the device to obtain the desired information regarding a subject body. Detecting and detection includes measuring and monitoring and other similar functional events associated with obtaining this information. For example, monitoring over time a known physiological event to obtain information about the changes in or ceasing of the event is considered herein detecting of the event.
  • the lower bound on the transmit signal is due to the need to separate the detection events of interest from the transmit carrier frequency.
  • the transmit frequency lower bound is necessary to enable distinguishing the signal components of these events from the transmit carrier signal.
  • the upper bound of 100 MHertz is due to the lack of effective signal above this frequency with the subject body dimensions existing with humans and similarly dimensioned bodies.
  • RF power absorption increases with frequency and power loss is exponential with distance into the body; at the depths required for detection of physiological events in a human a frequency below 100 MHertz has been found to be necessary to obtain depth penetration to create an effective signal.
  • the inventive method may be used to detect events having associated lower frequencies such as blood flow during hemorrhaging.
  • the frequency of interest may be very low, such as 1 milliHertz ( 0.001 Hertz)
  • the transmit signal frequency may be lower accordingly.
  • the transmit signal must have a continuous wave form and have a design that has extremely-low phase noise, as that term is understood in the industry.
  • the transmit signal may be filtered or amplified as may be required by the limitations of the other system hardware components.
  • the defining functional requirements of the receiver 12 are dependent on the anticipated power of the receive signal (the power of the transmit signal and antenna characteristics) and the particular requirements of the signal processor 14 employed. It is expected that in most applications pre- amplification and filtering will be required and provided by conventional devices.
  • the signal processor 14 receives both the transmit signal and the receive signal. If the frequency of the transmit (and receive) signal is substantially greater than that of the events of interest, such as when using a frequency of 100 MHertz, it is convenient to shift the frequency to baseband so that it is more readily processed. This frequency shift may be accomplished within the signal processor by combining each of the transmit signal and receive signal with a common reference continuous wave signal. The manner of this frequency reduction to baseband will be clear to one skilled in the art given the requirements here. Further, depending on the nature of the signal processor, conversion to a digital signal may be necessary. The above functions of the signal processor may be embodied in a variety of different alternative hardware device combinations.
  • FIG. 2 is a schematic illustration of a detection system according to the invention and configured for measurement of human physiological events such as heart rate and pulmonary rate.
  • human physiological events such as heart rate and pulmonary rate.
  • Many of the elements and components illustrated and discussed are provided to accommodate the incidental events occurring in application of the inventive device and method to human subjects and may not be necessary or may be altered if used in other applications or for other purposes.
  • the functional connectivity of the components is defined in
  • the antenna system consists of a single transmit antenna 101 and single receive antenna 102 as discussed above.
  • the receive antenna 102 has a substantially circular circumference that bounds a circular interior area.
  • the transmit antenna 101 includes a substantially circular outer ring portion, with a cutout portion that bounds a substantially circular inner ring portion.
  • the periphery of the transmit antenna 101 bounds an interior area and substantially surrounds an open area that is partially bordered by the inner ring portion.
  • the receive antenna 102 is located in relative registration to the transmit antenna 101 so that approximately half of the receive antenna interior area is superimposed on the transmit antenna inner area and approximately half of the receive antenna interior area is superimposed on the open area.
  • the total magnetic flux through the receive antenna 102 from the transmit antenna 101 is minimized. This is desired to reduce the magnitude of the transmit signal that is detected at the receive antenna 102 and reduce the signal dynamic range that is required to process the receive signals.
  • both antennas are formed of flat wire integrated in a printed circuit board.
  • the flat wire forming the transmit antenna 101 and receive antenna 102 should include only a relatively small number of turns to limit self-resonance to substantially less than the operating frequency. Typically, this requires the number of turns to be less than ten.
  • the flat wire in both antennas should have a common constant width. As well the flat wire in each turn should be spaced from each adjacent turn by half the wire width to minimize the parasitic capacitance between turns. Electrostatic shielding should be used in the receive antenna 102 and this may be a large flat copper single turn loop that covers all of the receive antenna turns with a small gap along the radial direction at one selected azimuthal angle.
  • Both antennas are preferably substantially planar in geometry and parallel and are preferably mounted within and supported and protected by a housing appropriate for the application environment.
  • a curved geometry antenna may be used depending on the particular application.
  • the transmit antenna 101 is connected generally to a source of a transmit signal with a carrier frequency of 3.000 MHertz characterized by low phase noise and minimal harmonic frequency content.
  • the extent of acceptable phase noise and harmonics is somewhat dependent on the resolution ability of the electronic hardware available for signal reception and processing.
  • the signal source is a 3.000 MHertz low phase noise transmit crystal oscillator 300.
  • a 3 MHertz low pass filter 301 is provided to reduce harmonics to acceptable levels.
  • the transmit signal is then amplified by a amplifier 330 to the extent necessary to produce the needed receive signal.
  • the needed power of the transmit signal provided to the antenna depends in part on the application parameters and the strength of the receive signal.
  • the receive antenna 102 is connected to a low-noise pre-amplifier 303 and a 3 MHz bandpass filter 304 and then a subsequent first amplifier 305.
  • the pre-amplifier 303, bandpass filter 304, and first amplifier 305 are provided to condition the received signal to the requirements of the signal processing components. These components or their functions may be combined or integrated into other components of the system.
  • the bandpass filter 304 should be selected to remove incidental receive signal components such as might be created by environment sources or hardware noise.
  • the receive signal and the transmit signal, respectively from the first and second amplifiers 305, 306, are each separately and similarly mixed by respective mixers 308, 309 with a signal provided by a low-phase noise local oscillator 307.
  • the oscillator 307 is selected to provide an extremely stable signal centered at a frequency of 3.001 MHertz.
  • the oscillator mixing signal frequency is selected to be 1 kHertz from the transmit signal such that the downconverted frequency is low enough to be conveniently processed by available signal processing hardware and high enough to contain the relatively low frequency (100 Hertz) modulation due to physiological events of interest such as respiration.
  • the oscillator mixing signal may be appropriately selected to provide the same result.
  • Both the downconverted (1 kHertz center frequency) transmit signal and downconverted (1 kHertz center frequency) receive signal pass through respective low pass filters 310, 31 1 to remove incidental frequencies substantially higher than 1 kHertz possibly generated by the mixing process.
  • Both the downconverted transmit signal and the downconverted receive signal are input to an analog- to-digital converter 312.
  • the digital converter 312 is connected to a digital signal processor 316 to accept both the digitized downconverted transmit signal and the digitized downconverted receive signal centered at 1 kHertz.
  • the digital signal processor 316 is configured to analyze the two signals by way of comparison to detect differences that reflect changes in the signal resulting from changes in the electrical impedance of the human subject body.
  • a quadrature (90-degree) phase shifted version of the transmit signal is created using the Hilbert transform.
  • the receive signal is multiplied by the transmit signal and 90-degree phase shifted transmit signal to move the signals to baseband and create a complex (in-phase and quadrature) baseband signal.
  • This signal is low- pass filtered digitally to remove high frequency components.
  • This complex baseband signal contains both the relative amplitude and phase difference between the transmit and receive signals. Particularly, signal amplitude and phase changes resulting from movement of body tissue or liquid movement may be detected in this way.
  • the functions of the digital signal processor 316 as well as the other components maybe be performed by other specific alternative hardware devices or systems.
  • the word "signal processor" should be understood to be general and may be satisfied by various conventional and future devices and systems and may include a combination of hardware and executable software components.
  • the signal processor may also include and integrate the components and functions for the signal downconversion and analog to digital conversion. For example also, other combinations of devices and functions within the configurations described here may be integrated onto a single digital device.
  • the physiological event of interest is a cardiac rate
  • the signal is filtered and features of the signal such as peaks and troughs are used to determine the respiratory rate.
  • the respiratory signal is subtracted and the remaining signal is used to develop cardiac metrics.
  • the remaining signal is compared with a time shifted version of itself to develop the signal autocorrelation. Peaks in the autocorrelation indicate the repetition period of the cardiac cycle. Alternatively, features of individual cardiac events are identified such as peaks to determine the cardiac rate or area per heartbeat to estimate cardiac output. Alternatively, wavelet analysis may be used to partition the signal into multiple, respiratory and cardiac, signals before feature extraction. In similar manner, signal components of one or more physiological events may be determined to discern physiological parameters for simultaneous events.
  • the output devices may be any of conventional devices including, as shown, LCD display 317, wireless interface 319, wired interface 320 such as USB.
  • User input may be provided through these same interface devices or separate input interface 318.
  • Power may be provided by any conventional means including a connected power source and a power regulation module 321 .
  • Figures 3, 4, 5 illustrate exemplary applications of the present device and methods.
  • the subject body is the physiological body of a person in typical circumstances of health care.
  • an antenna system 1 10 is placed in close proximity to, but not in contact with, the subject body 106.
  • the antenna system 1 10 must be designed to operate while spatially and physically separated from the body by various objects such as supporting devices and bedding and the like. In typical applications of the invention, the separation may be limited to a few inches ( 76.2 mm: millimeters). For these applications an effective receive antenna will have a physical geometry radius in the range of about 3 to 12 inches ( 76.2 to 304.8 mm). This is based on a typical effective antenna range being generally equal to the radius of the overall geometry of the receive antenna. Where the antenna must be operated at a greater distance from the subject body, the antenna must be designed with a greater effective range, typically achieved by increased antenna loop diameter.
  • the antenna system 1 10 is secured to, or otherwise located proximate, the underside of a hospital gurney or bed. With an appropriate sized antenna, a location under the body-supporting surface, or above the supporting surface but beneath any mattress or cushioning will allow operation without contact with the subject body, and without discomfort to the subject person.
  • an electronics package 103 including all the remaining electronic components of the system, may be located nearby and physically connected to the antenna system 1 10. Alternatively, the electronics package 103 may be located remotely and connected by shielded cabling. Alternatively also, the electronics may be integrated into a unified sensor (Figure 5).
  • the subject body 106 is the body of new-born child in a neonatal care facility.
  • the antenna system 1 10 and electronics package 103 are located under a typical plastic neonatal bassinet.
  • the antenna geometric size may be smaller than previously described for use in monitoring an adult body.
  • monitoring events such as heart rate and pulmonary rate without contact is critical to maximizing health and care.
  • FIG. 5 illustrates a portable monitoring system 100 that is enabled by the present methods.
  • the antenna system 1 10 and electronics package 103 are both integrated into the monitoring system 100.
  • the monitoring system is sized to allow it to be placed on a subject body, in this example on the abdomen of a patient. In applications of a pregnant mother, for example, the mother's physiological events and fetal physiological events may be monitored
  • the electronics package 103 may include local visual output display, or may be connected by conventional wired or wireless methods to a remote display or other devices. Likewise, individual components of the electronics package 103 or the electronics package 103 itself may be located separate from the antenna and connected appropriately. While the present system 100 is illustrated in contact with the subject body 106, it should be clear from the prior discussion that its operation would be effective if separated by clothing, bedding, or other incidental objects or space.
  • the present devices and methods include embodiments wherein a balancing signal is generated and combined with a receive signal to cancel or minimize the signal components induced by gross movements of the subject body. This limits the amplitude of the receive signal so that it does not exceed the known maximum input limits of the receive amplifier and digitizer electronics. If the subject body moves grossly relative to the sensor antennas, the balancing signal amplitude and phase are dynamically adjusted to compensate for the receive signal change and minimize the receive signal. This can be done automatically without interruption of the measuring activities and without notice by the user or subject.
  • FIG. 7a and 7b An associated operational flow diagram is provided in Figures 7a and 7b.
  • Figure 6 should be interpreted following conventional interpretation of the connectivity between the components and elements defined.
  • the elements in Figure 6 that are common with the configuration illustrated in Figure 2 have the functions and characteristics and operation previously specified except as differentiated below.
  • a voltage controlled amplifier 315 is connected and controlled as shown to apply its output to constrain the amplitude of the received signal.
  • a digital-to-analog converter 313 is connected to communicate with the digital signal processor 316.
  • the digital-to-analog converter 313 is connected to provide input to a voltage controlled phase shifter 314 and voltage controlled amplifier 315 to generate a balancing signal to the pre-amplifier 303.
  • the voltage controlled phase shifter 314 receives the filtered transmit signal from the low pass filter 301 .
  • the figures regard an automatic system operating procedure 400 directed by the digital signal processor 316.
  • the system turns on the transmit signal to the maximum value in step 401 by powering the electronics package 103 and using channel 1 of the digital to analog converter 313 and the connected voltage controlled amplifier 302.
  • the balancing signal is turned off in step 402 by setting the gain of the voltage controlled amplifier 315 to a low value.
  • the system determines if a subject is near the antenna in step 403 by measuring the impedance in the transmit antenna coil and comparing the impedance value to a predetermined value in step 404.
  • the transmit antenna impedance can be determined indirectly by measuring the current through the transmit antenna using impedance 322 and channel 3 of the analog-to-digital converter 312.
  • the presence of a subject may be determined by observing the receive signal phase as compared to the transmit signal phase. While this step of determining if a subject is near - within an effective detection range - is not critical to the process of measuring physiological events in the subject body, it is valuable in practical application.
  • an operational state will be set to, for example the text: "No Patient Above Antenna” in step 405, and the state status will be displayed to the operator in step 406 via display 317 or other output device. This process is repeated until the effective proximity of a subject is determined.
  • the operational state will be set to, for example the text: "Patient Above Antenna” in step 407, the state status will be displayed to the operator in step 408, and the system will transition to the next functional step 409.
  • the receive signal is measured in step 409 and processed in step 410 to isolate and determine the physiological components of the signal.
  • Physiological parameters are extracted in step 41 1 in the same manner as discussed previously and sent to the user interface in step 412.
  • the receive signal is checked to insure that it is within the known input range of the receive electronics. If so, the cycle repeats as long as a subject is near the antenna.
  • step 415 the transmit gain of the voltage controlled amplifier 302 is set to the minimum value to avoid saturating the receive electronics.
  • the balancing signal is also turned off in step 416 by setting the gain of the voltage controlled amplifier 315 to a low value using channel 3 of the digital-to-analog converter 313.
  • step 417 the receive signal amplitude is measured and in step 418 compared to the known input range of the electronics. If the signal is off scale then an error condition is set in step 419 and sent to the user interface in step 420.
  • the amplitude and phase of a balancing signal are calculated within the digital signal processor 316 to minimize the receive signal in step 421 .
  • the balancing signal is applied in step 422 by generating analog control signals using channels 2 and 3 of the digital-to- analog converter 313.
  • the controlling signals are produced by the digital signal processor 316 and drive the voltage controlled amplifier 315 and voltage controlled phase shifter 314.
  • the balancing signal is produced by modifying the transmit signal via the voltage controlled phase shifter 314 and applying the result to the connected voltage controlled amplifier 315.
  • the transmit signal is checked in step 423 to determine if it is at the maximum. If not, the transmit signal gain is increased by one increment in step 424 and the receive signal is measured again.
  • the gain is incrementally increased and new balancing signals are applied until the transmit gain is at a previously determined, system dependent, maximum value. In this way, the signal amplitude is increased while constraining the receive signal so that it remains within the input scale of the analog-to-digital converter 312. Once the transmit signal is set to the maximum value and the receive signal is still on scale, the system will transition to the normal operating mode 414 functional step 403. The above process may be continued indefinitely to measure and monitor a subject body for one or more simultaneous

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  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Radiology & Medical Imaging (AREA)
  • Electromagnetism (AREA)
  • Hematology (AREA)
  • Measuring And Recording Apparatus For Diagnosis (AREA)

Abstract

L'invention concerne des capteurs d'impédance électromagnétique et des procédés associés pour détecter, mesurer et surveiller l'un quelconque d'une variété d'indicateurs physiologiques comprenant, par exemple, la fréquence cardiaque et respiratoire sans contact direct avec un patient. La présente invention est particulièrement, mais pas exclusivement, utile pour détecter l'apparition de détresse respiratoire chez un patient. Les capteurs et les procédés sont aptes à fonctionner en présence d'un grand mouvement de patient intermittent ou d'objets externes comprenant des objets métalliques qui peuvent interférer avec le champ électromagnétique utilisé dans des activités de mesure.
PCT/US2014/041747 2013-06-19 2014-06-10 Système de télésurveillance d'évènements physiologiques WO2014204721A1 (fr)

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US61/836,815 2013-06-19

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018077657A1 (fr) 2016-10-25 2018-05-03 Vigilitech Ag Dispositif de capteur
CN110996787A (zh) * 2017-05-04 2020-04-10 皇家飞利浦有限公司 用于通过频率调谐和阻抗相位和/或幅度变化的分析来动态聚焦于心脏和/或肺的系统和方法

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Publication number Priority date Publication date Assignee Title
WO2008036396A2 (fr) * 2006-09-21 2008-03-27 Noninvasive Medical Technologies, Inc. Appareil et procédé d'interrogation radio non invasive du thorax
US20080275328A1 (en) * 2005-06-27 2008-11-06 David Paul Jones Sensing body functions
US7811234B2 (en) * 2002-08-01 2010-10-12 California Institute Of Technology Remote-sensing method and device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7811234B2 (en) * 2002-08-01 2010-10-12 California Institute Of Technology Remote-sensing method and device
US20080275328A1 (en) * 2005-06-27 2008-11-06 David Paul Jones Sensing body functions
WO2008036396A2 (fr) * 2006-09-21 2008-03-27 Noninvasive Medical Technologies, Inc. Appareil et procédé d'interrogation radio non invasive du thorax

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018077657A1 (fr) 2016-10-25 2018-05-03 Vigilitech Ag Dispositif de capteur
CN109963498A (zh) * 2016-10-25 2019-07-02 维吉泰科股份有限公司 传感器装置
JP2019537733A (ja) * 2016-10-25 2019-12-26 ヴィジリテック アーゲー センサーデバイス
JP2022091843A (ja) * 2016-10-25 2022-06-21 ヴィジリテック アーゲー センサーデバイス
CN109963498B (zh) * 2016-10-25 2022-07-12 维吉泰科股份有限公司 传感器装置
US11696697B2 (en) 2016-10-25 2023-07-11 Vigilitech Ag Sensor device
CN110996787A (zh) * 2017-05-04 2020-04-10 皇家飞利浦有限公司 用于通过频率调谐和阻抗相位和/或幅度变化的分析来动态聚焦于心脏和/或肺的系统和方法
CN110996787B (zh) * 2017-05-04 2023-11-07 皇家飞利浦有限公司 用于通过频率调谐和阻抗相位和/或幅度变化的分析来动态聚焦于心脏和/或肺的系统和方法

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