EP1168961A4 - Appareil et procede passifs et non invasifs pour surveiller la frequence cardiaque foetale - Google Patents

Appareil et procede passifs et non invasifs pour surveiller la frequence cardiaque foetale

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Publication number
EP1168961A4
EP1168961A4 EP00916231A EP00916231A EP1168961A4 EP 1168961 A4 EP1168961 A4 EP 1168961A4 EP 00916231 A EP00916231 A EP 00916231A EP 00916231 A EP00916231 A EP 00916231A EP 1168961 A4 EP1168961 A4 EP 1168961A4
Authority
EP
European Patent Office
Prior art keywords
waveform
fetal
mother
maternal
sensor
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP00916231A
Other languages
German (de)
English (en)
Other versions
EP1168961A2 (fr
Inventor
Robert S Greenberg
John A Cristion
Edward J Moses
Wayne I Sternberger
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Johns Hopkins University
Original Assignee
Johns Hopkins University
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Filing date
Publication date
Application filed by Johns Hopkins University filed Critical Johns Hopkins University
Publication of EP1168961A2 publication Critical patent/EP1168961A2/fr
Publication of EP1168961A4 publication Critical patent/EP1168961A4/fr
Withdrawn legal-status Critical Current

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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
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/30—Input circuits therefor
    • A61B5/307—Input circuits therefor specially adapted for particular uses
    • A61B5/308—Input circuits therefor specially adapted for particular uses for electrocardiography [ECG]
    • 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
    • A61B5/02405—Determining heart rate variability
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/30—Input circuits therefor
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/316—Modalities, i.e. specific diagnostic methods
    • A61B5/318—Heart-related electrical modalities, e.g. electrocardiography [ECG]
    • A61B5/344—Foetal cardiography
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/43—Detecting, measuring or recording for evaluating the reproductive systems
    • A61B5/4306—Detecting, measuring or recording for evaluating the reproductive systems for evaluating the female reproductive systems, e.g. gynaecological evaluations
    • A61B5/4343—Pregnancy and labour monitoring, e.g. for labour onset detection
    • A61B5/4362—Assessing foetal parameters
    • 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
    • A61B5/02411—Detecting, measuring or recording pulse rate or heart rate of foetuses
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/25—Bioelectric electrodes therefor
    • A61B5/279—Bioelectric electrodes therefor specially adapted for particular uses
    • A61B5/28—Bioelectric electrodes therefor specially adapted for particular uses for electrocardiography [ECG]
    • A61B5/282—Holders for multiple electrodes

Definitions

  • the invention relates generally to biomedical devices and, in particular, comprises a non- invasive and passive apparatus and method that uses sensors and signal processing techniques to monitor fetal electrocardiographic waveform (EKG f ), heart rate, heart rate variability and heart
  • EKG f fetal electrocardiographic waveform
  • heart rate heart rate
  • heart rate variability heart rate variability
  • Fetal assessment in this context is intended to detect conditions that, if continued, would likely result in fetal and newborn damage or death.
  • the condition of the fetus is reflected by the cardiovascular responses in utero and may be recognized by monitoring the fetal heart rate.
  • the primary non-invasive fetal monitoring technique is the Doppler/tocometer.
  • the technique is cumbersome and subject to data loss as a result of fetal and maternal movement.
  • a Doppler transducer is placed on the mother's abdomen in a position that focuses the ultrasound signal at the fetal heart. Should the fetus move relative to the transducer, it is highly likely that the transducer will no longer be in proper position and, thus, not record an accurate
  • U.S. Patent No. 5,257,627 to Rapoport relates to a portable apparatus for the non- invasive, simultaneous, self-testing of fetal and maternal signals.
  • the device has a signal processing means for simultaneously processing fetal heart rate and maternal input signals, and also has a communication linking means for the simultaneous transmission of the fetal heart rate and maternal input data to a remote output device.
  • Rapoport's device uses ultrasonic means to detect the fetal heart rate.
  • Non-invasive techniques include the processing of electrocardiograph and electromyogram signals for determination of the fetus' well-being.
  • U.S. Patent No. 4,299,234 to Epstein et al. relates to a fetal heart rate monitor which combines electrocardiograph and electromyogram type signals to increase reliability and accuracy of the resulting heart rate information.
  • U.S. Patent No. 4,781,200 to Baker relates to a self-contained, lightweight ambulatory fetal monitoring system for substantially continuous analysis of fetal well-being.
  • the monitor includes a sensor garment which is worn by the mother and has a plurality of sensors.
  • the sensors detect fetal heartbeats and movements of the fetus within the mother.
  • Signals developed by the sensors are processed by signal processing equipment and analyzed by a programmable data processing unit which can be provided with a variety of analytical programs which are proposed to automatically and continuously analyze fetal well-being.
  • the sensor belt goes around the waist of the mother, and thus obstructs the surgical field.
  • U.S. Patent No. 5,042,499 to Frank et al. relates to a fetal heart rate monitor that monitors weak fetal electrocardiogram signals in the presence of strong interfering noise.
  • Frank et al's invention non-invasively obtains from the abdomen of a pregnant subject the fetal EKG f signal,
  • electrocardiograph lead There is no uniform placement of the abdominal electrodes for all patients. Placement of such leads is dependent on prior examination by a trained medical professional to identify optimal lead orientation.
  • a large maternal signal and the presence of electrical noise has substantially precluded recognition of the fetal electrocardiogram.
  • electrical noise e.g. muscle artifact
  • the placement of a fetal scalp electrode is clearly invasive, generally less comfortable for the mother, and has associated increased risks, such as infection, to the fetus, mother, and caretakers.
  • the issue of infection has received more attention recently with increased risks of serious bloodborne infections such as AIDS.
  • the present invention provides a method of monitoring a fetal biopotential waveform. More particularly, the present invention provides a method for generating a fetal biopotential waveform and using the waveform components to monitor many variables including, but not limited to, the fetal heart rate, the fetal heart rate variability, and/or the fetal heart vector orientation of a fetus in a pregnant mother.
  • the method includes the steps of measuring at least one biopotential waveform indicative of the mother's heart beat to form a maternal waveform, measuring at least one biopotential waveform indicative of the combined maternal and fetal heart beats to form a combined biopotential waveform, and using signal processing to cancel the maternal waveform from the combined waveform to derive a fetal waveform indicative of the fetus' biopotential electrocardiographic waveform (EKGf).
  • the present invention also provides an apparatus for monitoring a fetal biopotential waveform.
  • the present invention also provides an apparatus for generating a fetal biopotential waveform and using the waveform to monitor the fetal heart rate, the fetal heart rate variability, and/or the fetal heart vector orientation of a fetus in a pregnant mother.
  • the apparatus includes at least one sensor, e.g., an electrode, for measuring at least one biopotential waveform indicative of a maternal heart beat, at least one sensor for measuring at least one biopotential waveform indicative of the combined maternal and fetal heart beats taken from a pregnant mother, and signal processing hardware, software, or hybrid mixes that can cancel the maternal waveform from the combined waveform to form a waveform indicative of the EKGf.
  • the present invention non-invasively and passively measures fetal and maternal electrocardiographic and maternal electromyographic waveforms by using traditional surface electrode electrocardiographic and electromyographic techniques combined with adaptive signal processing methods to solve the problems associated with the devices/techniques described above.
  • patient information e.g., fetal heart rate/variability, taking into account noise artifacts attributable to uterine contractions
  • the invention uses, for example, suitable skin contact electrodes connected to amplifiers to acquire biopotential waveforms and form signals, preferably differential signals, indicative of the mother's heart beat from sensors, e.g., electrodes, placed on her chest, and indicative of the combined maternal and fetal heart beats from sensors placed on the mother's
  • Maternal heart rate, heart rate variability, and respiration rate are derived from the chest signals; standard maternal EKG is derived from planar leads. Instead of differential signals, more vectors may be formed by collecting single-ended signals and creating "differential pairs" therefrom.
  • the sensors placed on the mother's abdomen, lower back, or both are preferably placed to form pairs of sensors wherein each sensor of the pair is spaced from the other and each pair is positioned in a substantially criss-crossed pattern with respect to other sensor pairs. Substantial spacing between the sensors of each sensor pair and between pairs of sensors is preferred so as to achieve a three-dimensional processing of the fetal biopotential waveform.
  • the sensors are preferably positioned to avoid blocking any surgical fields, for example, the abdominal area.
  • the uniqueness of the vectors can be used to establish the vector orientation of the fetus.
  • the number of vectors used is sufficient to achieve a clear signal indicative of the combined fetal and maternal waveforms. If a clear enough combined signal is obtained from a single sensor, the present invention can operate using a single sensor to obtain the combined
  • the signals from the abdominal electrodes are divided into a plurality of channels.
  • an adaptive signal processing filter (ASPF) algorithm or other suitable algorithm is used to cancel the estimated maternal waveform from each channel in the abdominal electrodes, using chest signals as references.
  • the system selects from at least one of the resulting waveforms to serve as the reference fetal waveform, for example, the waveform with the highest peak-to-peak amplitude.
  • the reference waveform is then processed against the other abdominal waveforms with the maternal waveforms canceled to form an enhanced fetal signal that is a representation of the EKGf.
  • the EKG f can subsequently be used to measure fetal heart rate and other biophysical profile parameters.
  • Surface electromyogram (EMG) signals allow for concurrent monitoring of uterine contractions and afford improved cancellation of motion artifacts including noise attributable to
  • the present invention provides a device that is totally non-invasive, passive and will supplant the fetal scalp electrode and, therefore, eliminate those risks of infection.
  • all signals are derived from standard EKG electrodes applied to the patient's skin.
  • the present invention also provides a device with sensor placement, e.g., probe electrode placement, that is universal across the patient population. Furthermore, in embodiments of the
  • sensor strips or other free floating sensors e.g., non-adhesive
  • the patient's position can be rotated or reorientated relative to the sensor field.
  • the sensors must be capable of sensing a respective waveform without the need to be adhered to the patient's body.
  • the present invention also provides a device where the placement of the electrodes maintains a clear surgical field, thereby facilitating operative procedures such as cesarean section
  • the present invention also provides a device that overcomes the signal loss anomaly of
  • ultrasound devices resulting from fetal movement There is no need to tend to the device and reposition electrodes as the fetus moves, thereby allowing health professional time and attention to be directed toward more productive patient care activities.
  • the present invention also provides a device that will achieve a full representation of the
  • fetal EKG f waveform which may provide useful information about the fetal condition.
  • the present invention also provides a device which upon interpretation of the fetal EKG f
  • the present invention provides a device that routinely collects maternal EKG signals. Thus, collateral information about the well-being of the mother and possible maternal-fetal interactions are immediately available.
  • the present invention also provides a device that will function for an ambulatory patient, either pre-term or during prolonged labors where the patient wishes to ambulate.
  • the present invention also provides a device that can be used in the case of non-imminent deliveries, for example, pre-term patients who may have high risk pregnancies.
  • the present invention also provides a device that computes and displays a unique monitoring reading that provides a measure of the instantaneous processing performance.
  • the present invention also provides a device that computes and displays heart rate variability information in at least two forms: i) long term variability trend, as is available with current commercial systems; and ii) a unique measure of instantaneous variability.
  • the present invention also provides a means to monitor multiple gestations with no additional sensors and/or processing techniques being required.
  • the present invention also provides a device that routinely collects electromyographic
  • EMG EMG signals as a means for monitoring maternal uterine contractions and for providing an additional signal input for noise cancellation.
  • the device also permits the identification and characterization of active (maternal movement) and passive (surgical manipulation, uterine contraction) maternal signals from EMG inputs useful for canceling noise
  • Fig. 1 is a block diagram of the preferred concept of the present invention.
  • Fig. 2 illustrates exemplary electrode positions and signal channels for the present
  • Fig. 3 is an illustration of a sensor placement scheme showing strip sensors positioned on opposing sides of a pregnant mother's abdomen in accordance with an embodiment of the present invention.
  • Fig. 4 is an illustration of a sensor placement scheme showing a strip sensor in place and a strip sensor connected to an electrode interface.
  • Fig. 5 is a functional block diagram of the signal processing of the invention.
  • Fig. 6 illustrates an exemplary adaptive signal processing filter (ASPF) used in the invention's signal processing, the ASPF using a Least-Mean-Squares (LMS) algorithm.
  • APF adaptive signal processing filter
  • LMS Least-Mean-Squares
  • Fig. 7 illustrates results using the present invention with simulated data. Characteristic simulated fetal (Baseline Fetal) and maternal EKG signals were summed together (Abdominal) with noise in order to validate the signal processing algorithms. Fetal R-peaks are evident
  • Fig. 8 illustrates results with representative clinical data. Data sample collected in the clinical environment using the present invention. The three signal traces correspond to the simulation data shown in the inset of Fig. 7. The jagged appearance of the signals is an artifact of graphics manipulation and not a system limitation.
  • Fig. 9 is a graph showing the time histories of the fetal heart rate and the maternal heart rate derived from waveforms acquired according to the present invention.
  • the present invention provides a method of monitoring a fetal biopotential waveform.
  • the present invention provides a method for generating a fetal biopotential waveform and using the waveform to monitor the fetal heart rate, the fetal heart rate variability, and/or the fetal heart vector orientation of a fetus in a pregnant mother.
  • the method includes the steps of measuring at least one biopotential waveform indicative of the mother's heart rate to form a maternal waveform, measuring at least one biopotential waveform indicative of the combined maternal and fetal heart rates to form a combined biopotential waveform, and using signal processing to cancel the maternal waveform from the combined waveform to derive a fetal waveform indicative of the fetal electrocardiographic waveform (EKG f ).
  • the present invention also provides an apparatus for monitoring a fetal biopotential waveform and an apparatus for monitoring the fetal heart rate, the fetal heart rate variability, and/or the fetal heart vector orientation of a fetus in a pregnant mother.
  • the apparatus includes at least one electrode for measuring at least one biopotential waveform indicative of a maternal heart rate, at least one electrode for measuring at least one biopotential waveform indicative of the combined maternal and fetal biopotential waveform taken from a pregnant mother, and a signal processing circuit that can cancel the maternal waveform from the combined waveform to form a waveform indicative of the fetal electrocardiographic waveform (EKG f ).
  • the maternal biopotential waveform is preferably acquired from at least one sensor, e.g., a skin contact electrode, and preferably from two or more sensors, placed on or in contact with the mother's chest, upper back, or both.
  • the combined waveform is acquired from at least one sensor, e.g., a skin contact electrode, and preferably from two or more sensors, placed on or in contact with the mother's abdomen and/or lower back.
  • the combined waveform is acquired by combining the signal from at least one sensor placed on or in contact with the mother's abdomen and at least one other sensor placed on or in contact with the mother's abdomen, lower back, or both.
  • the combined waveform can be preferably derived, according to the invention, from a
  • the method then includes canceling an acquired maternal waveform from each channel to form a plurality of resulting waveforms, and selecting at least one of the resulting waveforms as a reference fetal waveform.
  • the selected waveform can be, for example, the waveform with the highest peak-to-peak amplitude.
  • the selected reference fetal waveform is enhanced using an adaptive signal processing filter algorithm or another suitable algorithm to remove correlated noise by processing against the remaining
  • the signal processing algorithm can use a least mean squares (LMS) algorithm to dynamically weigh all of the waveforms derived from the sensor on the mother's chest against each of the waveforms derived from each of the sensors on the mother's abdomen and/or lower back.
  • LMS least mean squares
  • the fetal electrocardiographic waveform derived according to the method and apparatus of the present invention can be visually analyzed by observing a visual display of the waveform or by inspecting other forms of data acquired that correlate with or have a relationship to the waveform.
  • a trained technician can visually analyze the waveform to determine any abnormalities in the visual representation of the waveform and thus can determine any abnormalities in the fetus' well-being.
  • a table or library of normal EKG f 's can be
  • the mother's abdomen and/or lower back are preferably spaced away from the lower anterior abdomen or, for example, away from the lower right-side anterior abdomen so as not to interfere with a cesarean section delivery of the fetus, an appendectomy operation or other procedure should such procedures be necessary.
  • the skin sensors placed on the mother's chest are preferably placed, for example, away from the midline of the chest so as not to interfere with resuscitation attempts on the mother, should such attempts be necessary.
  • the sensors used to transduce the biopotential signals of interest may preferably be skin contact electrodes.
  • Exemplary electrodes include silver-silver chloride (Ag-Ag CI) dot electrodes that make contact with the skin on one or more sides and are in contact with an electrical contact (e.g., a snap) on the other side.
  • the skin is generally prepared in order to provide a good electrical interface with the dot electrode. For instance, the skin may be wiped with alcohol, subject to slight abrasion, and coated with an electrode gel. After the preparation, the dot electrode is applied and wired into an amplifier of the signal processing system. Good technique in skin preparation is helpful when the sensors employed are skin contact electrodes. Poor electrode interfaces can lead to excessive noise on the signal lead, potential for external pick-up, and similar problems. These "extra" noises or noise sources are likely to be of such a character that they may interfere with the extraction and enhancement of the fetal electrocardiographic waveform.
  • the present invention provides a method to automatically generate a signal to automatically generate a signal.
  • an impedance meter such as the Prep-Check, available from General Devices, making an impedance measurement requires that an active measurement be made, for example, by imposing a small current on the circuit and measuring the voltage drop.
  • the present inventors have developed a preferred method of using the passive amplifier data to make an assessment of signal quality.
  • the signal quality can be tested by a variety of means, including testing the frequency character.
  • the frequency character (spectrum) of the EKG signal preferably has a large low frequency component followed by a roll-off with increasing frequency.
  • amplifiers are used that preferably have a 60 Hz notch filter for rejecting line noise artifacts.
  • EKG signals After the notch filter, the signal rises slightly to a flat noise floor.
  • "good” EKG signals preferably repeatedly and reliably exhibit this spectrum, whereas "bad” EKG signals do not exhibit a 60 Hz notch characteristic and reach a noise floor at a lower frequency and at a higher relative amplitude. These distinctions are used to validate whether a channel is good or bad.
  • a segment of the EKG signal is preferably processed by an algorithm known as a fast fourier transfer (FFT) to generate the frequency spectrum. Then, a ratio of the signal energy at a low frequency (approximately 2 Hz) to the signal energy at 60 Hz
  • FFT fast fourier transfer
  • Good channels are those determined to have large ratio magnitudes whereas bad channels have smaller ratio magnitudes, depending upon the sensors used and the characteristics of the various signals that are obtained. Those channels that do not exceed a minimum ratio magnitude are deemed to be bad and are not used for subsequent processing.
  • the ability to selectively include only "good" signals provides the apparatus with a high level of adaptability and robustness.
  • the device can also include, for example, a thermometer or a motion sensor. Suitable motion sensors that can be used include, for example, accelerometers or inclinometers. These added devices can be included to provide an indication of the patient's condition at the time that certain changes in electrocardiographic waveform occur.
  • the information acquired by the monitor might be stored and forwarded or might be used to identify problem situations.
  • collateral measurements of the activities occurring at the time a "suspect" event occurs may shed light on the nature of the event. For instance, if an episode of
  • the apparatus of the present invention is described in more detail below and includes electrodes and signal processing circuitry to carry out the methods and complete the apparatus described above.
  • biopotential waveform of an electrically beating fetal heart, though small in proportion to its mother, will exist in combination with the maternal waveform.
  • the invention preferably starts by acquiring maternal and maternal-plus-fetal biopotential
  • the maternal waveforms can be collected by surface electrodes preferably placed on the mother's chest and/or upper back, preferably on both sides, but not in the middle, of the mother's chest.
  • upper back what is meant is the portion of the back not below the level corresponding to the sternum.
  • the maternal-plus-fetal waveforms or “combined waveforms” are collected by surface electrodes placed on the mother's abdomen and/or lower back, preferably on the sides of the mother's abdomen.
  • lower back what is meant is that portion of the back below the sternum.
  • An exemplary electrode placement scheme is shown in Fig. 2.
  • a clinically significant aspect of the present invention is that the sensors (electrodes) are placed in an adaptable pattern, in other words, in a pattern irrespective of the fetal position, the maternal condition, or the size and shape of the mother.
  • the electrodes are preferably positioned in a manner so as to remain clear of usual potential operative sites. Equally significant is the fact that the successful implementation of the monitor is insensitive to variations in the placement of the electrodes; thus, a patient who is monitored at different points in time need not have the electrodes placed in the same exact location for each monitoring episode.
  • the electrodes can be a plurality of separate electrodes or a small number, for example, two, of electrode strips. Each strip can contain a plurality of electrodes and preferably only a single cable assembly. According to a preferred embodiment of the present invention, two electrode strips are used and each strip contains a plurality of electrodes. Placement of the electrode strips can be routine, simple, and
  • Fig. 3 is an illustration of a sensor placement scheme useful in accordance with the
  • Chest sensors for monitoring the maternal biophysical waveform are shown in
  • strip sensor 34 includes a plurality (seven in the strip sensor shown) of individual sensors 38 along the length of the strip sensor 34.
  • strip sensor 36 includes a plurality of sensors 40 (seven in the strip sensor shown) spaced along the length of strip sensor
  • Fig. 4 shows the operative positioning of a left-side strip sensor 42 containing seven sensors 44 spaced along the length of strip sensor 42.
  • the strip sensor 42 is positioned in the same place as the left-side sensor shown in Fig. 3.
  • the strip sensor is positioned on the pregnant mother along the lower anterior abdomen away from the operative field necessary for a cesarean section delivery, and wrapping around the curve of the mothers lower abdomen.
  • a strip sensor 46 containing seven individual sensors 48 spaced along the length of strip sensor 46. Strip sensor 46 is not in an operative position but is
  • a singular lead 50 carrying signals from each of the seven individual sensors 48 can be employed and can be interfaced with an electrode interface 52 from which a lead 54 extends to carry the signals for further signal processing.
  • numbers of differently oriented vectors are collected for both signal types (maternal only and maternal-plus-fetal). Pairs of electrodes (channels) are
  • An exemplary channel would include the pair of
  • All channels are preferably amplified and filtered in order to reject noise and provide anti-aliasing for subsequent digitization. In one embodiment, all channels are sampled at a rate less than or equal to 250 samples/second.
  • sampling involves digitization, a resolution of less than or equal to 16 bits is preferred.
  • Other sampling methods can be used, including analog methods, hybrid analog/digital methods, or combinations
  • Channel validation as discussed above is preferably used to assure that
  • the first phase of signal processing applies an Adaptive Signal Processing Filter (ASPF) algorithm to cancel the estimated maternal (chest) waveform from each abdominal channel.
  • a standard maternal EKG can be derived from planar leads.
  • All chest channels are dynamically weighted against individual abdominal channels in order to effect the cancellation of the estimated maternal (chest) waveform from each abdominal channel.
  • Several bipolar leads measure the electrical signal (reference) across the maternal chest (Chest Channel 1...N).
  • Several additional bipolar leads measure the signal from the maternal abdomen (Abdominal Channel 1...Q).
  • the chest leads are used as a basis to cancel the maternal signal from the abdominal leads (Estimated Fetal 1...K).
  • the abdominal leads are enhanced to derive the resulting fetal EKG r
  • Additional reference signals can be included to optimize noise cancellation. All components used to implement the algorithms are commercially available individually.
  • a filter chip co-processor as described in U.S. Patent No. 5,931 ,892, which is incorporated herein in its entirety by reference, can be used, for example, to implement the ASPF algorithm.
  • the resultant estimated fetal waveforms will exhibit a range of peak-to-peak
  • At least one of the resultant waveforms is selected as the reference for the next phase of processing, for example, the waveform with the largest peak-to-peak amplitude.
  • Channel validation can preferably be used to assure that non-functional or corrupt abdominal
  • the selected reference fetal waveform happens to be Estimated Fetal 1 in Fig. 5 although any of the estimated fetal signals can be selected.
  • One method of selecting the estimated fetal signal is to choose the signal with the largest peak-to-peak amplitude.
  • the selected estimated fetal signal is enhanced to remove correlated noise, by processing against the remaining abdominal estimated fetal waveforms.
  • the enhanced fetal signal that is the output of this step is a representation of the fetus' biopotential electrocardiogram (EKGf) and can be used to assess or monitor fetal conditions including the well-being of the fetus.
  • the EKGf can be used to assess fetal well-being by measuring fetal heart rate, fetal heart rate variability, and approximate entropy, as well as defining orientation of the fetus within the mother, and/or other components of biophysical profile parameters.
  • Fetal heart rate and heart rate variability are derived, preferably through R-to-R interval timing, or by appropriate auto-correlation processing of either the enhanced fetal signal or one or more of the processed abdominal signals.
  • Fetal position, inferred from the heart vector orientation, is determined by the signal strength and polarity of the EKG f waveform relative to the abdominal
  • the maternal heart vector can be used as a reference point for determining the fetal heart vector.
  • the three-dimensional nature of the abdominal array readily accommodates
  • the invention has been validated both with simulated data (Fig. 7) and human clinical
  • the monitor concept and algorithms can be validated using simulated data comprised of a representative fetal EKG f signal (Fig. 7). To this representative signal a maternal signal of an
  • amplitude proportional to a standard signal reported in literature can be added.
  • the fetal and maternal EKG's were randomly dithered in both amplitude and repetition rate.
  • a baseline noise level characterized by what is seen in the clinical situation, was also added to this composite.
  • This signal was then processed by the algorithm to first adaptively cancel the maternal signal, and then adaptively enhance the resulting fetal signal to identify the underlying signal.
  • the results from clinical data (Fig. 8) demonstrate comparable performance.
  • the device comprised a MP100 system (BIOPAC Systems, Inc.), with 16 ECG100B
  • Fig. 9 demonstrates a use of the present invention in monitoring the deceleration of a
  • fetus' heart rate as, for example, accompanying uterine contractions.
  • Both the fetal heart rate and the maternal heart rate shown in the graph of Fig. 9 were derived according to the method and apparatus of the present invention.
  • Fig. 9 shows that during the time period of from about 48 to about 50 seconds there was a corresponding, and normal, deceleration of the fetal heart rate.
  • the present invention is a reliable, accurate, non-invasive, and passive technique to measure the electrocardiographic waveform of the fetus. Furthermore, the present invention
  • the monitor's output can include the fetal
  • electrocardiographic waveform in addition to the fetal heart rate, and includes a description of heart rate variability as well as maternal heart rate and noise artifacts attributable to uterine

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  • Physiology (AREA)
  • Pediatric Medicine (AREA)
  • Pregnancy & Childbirth (AREA)
  • Gynecology & Obstetrics (AREA)
  • Reproductive Health (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)
  • Ultra Sonic Daignosis Equipment (AREA)

Abstract

L'invention concerne un appareil et un procédé permettant de contrôler la fréquence cardiaque foetale et de surveiller la fréquence cardiaque et les contractions utérines de la mère, grâce à des formes d'onde biopotentielles, qui indiquent la fréquence cardiaque de la mère, produites par des capteurs placés sur ou à proximité de la poitrine de la mère, ces formes d'onde indiquant par ailleurs les fréquences cardiaques de la mère et du foetus détectées par des capteurs disposés sur l'abdomen ou le bas du dos de la mère, voire sur les deux. Les signaux émis par ces capteurs abdominaux sont divisés en plusieurs voies, un algorithme ASPF (filtre de traitement de signaux adaptatif), ou tout autre algorithme approprié, étant ensuite utilisé pour effacer la forme d'onde maternelle estimée à partir de chaque voie dérivée de ces capteurs abdominaux. Puis ce système sélectionne, à partir des formes d'onde obtenues, au moins une forme d'onde destinée à servir de forme d'onde foetale de référence. Cette forme d'onde de référence est ensuite comparée aux autres formes d'onde, de préférence à l'aide dudit algorithme ASPF, de manière à former un signal foetal amélioré représentant l'électrocardiogramme biopotentiel foetal (EKGf), qui peut être utilisé ultérieurement pour mesurer la fréquence cardiaque foetale ainsi que d'autres paramètres du profil biophysique. Enfin, les signaux électromyographiques (EMG) superficiels permettent à la fois de surveiller les contractions utérines et de réduire efficacement les artefacts dus aux mouvements.
EP00916231A 1999-03-15 2000-03-10 Appareil et procede passifs et non invasifs pour surveiller la frequence cardiaque foetale Withdrawn EP1168961A4 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US12444799P 1999-03-15 1999-03-15
US124447P 1999-03-15
PCT/US2000/006295 WO2000054650A2 (fr) 1999-03-15 2000-03-10 Appareil et procede passifs et non invasifs pour surveiller la frequence cardiaque foetale

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EP1168961A2 EP1168961A2 (fr) 2002-01-09
EP1168961A4 true EP1168961A4 (fr) 2003-05-02

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EP (1) EP1168961A4 (fr)
JP (1) JP2002538872A (fr)
AU (1) AU758778B2 (fr)
CA (1) CA2345720C (fr)
WO (1) WO2000054650A2 (fr)

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Also Published As

Publication number Publication date
WO2000054650A3 (fr) 2001-02-15
EP1168961A2 (fr) 2002-01-09
CA2345720A1 (fr) 2000-09-21
AU758778B2 (en) 2003-03-27
JP2002538872A (ja) 2002-11-19
WO2000054650A2 (fr) 2000-09-21
AU3736700A (en) 2000-10-04
CA2345720C (fr) 2005-01-04

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