WO2014029986A1 - Foetal monitoring - Google Patents

Foetal monitoring Download PDF

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Publication number
WO2014029986A1
WO2014029986A1 PCT/GB2013/052195 GB2013052195W WO2014029986A1 WO 2014029986 A1 WO2014029986 A1 WO 2014029986A1 GB 2013052195 W GB2013052195 W GB 2013052195W WO 2014029986 A1 WO2014029986 A1 WO 2014029986A1
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WO
WIPO (PCT)
Prior art keywords
heart rate
processor
foetal
foetal heart
status
Prior art date
Application number
PCT/GB2013/052195
Other languages
French (fr)
Inventor
Michelle FERNANDES
Ricardo Pachon CORTES
Original Assignee
Fernandes & Co. Global Healthcare Solutions Limited
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Publication date
Application filed by Fernandes & Co. Global Healthcare Solutions Limited filed Critical Fernandes & Co. Global Healthcare Solutions Limited
Publication of WO2014029986A1 publication Critical patent/WO2014029986A1/en

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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
    • A61B5/0004—Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network characterised by the type of physiological signal transmitted
    • A61B5/0011—Foetal or obstetric data
    • 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
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7271—Specific aspects of physiological measurement analysis
    • A61B5/7275—Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/74—Details of notification to user or communication with user or patient ; user input means
    • A61B5/746—Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/02—Measuring pulse or heart rate
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
    • A61B8/08—Detecting organic movements or changes, e.g. tumours, cysts, swellings
    • A61B8/0866—Detecting organic movements or changes, e.g. tumours, cysts, swellings involving foetal diagnosis; pre-natal or peri-natal diagnosis of the baby
    • G—PHYSICS
    • G16—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
    • G16H—HEALTHCARE INFORMATICS, i.e. INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR THE HANDLING OR PROCESSING OF MEDICAL OR HEALTHCARE DATA
    • G16H40/00—ICT specially adapted for the management or administration of healthcare resources or facilities; ICT specially adapted for the management or operation of medical equipment or devices
    • G16H40/60—ICT specially adapted for the management or administration of healthcare resources or facilities; ICT specially adapted for the management or operation of medical equipment or devices for the operation of medical equipment or devices
    • G16H40/63—ICT specially adapted for the management or administration of healthcare resources or facilities; ICT specially adapted for the management or operation of medical equipment or devices for the operation of medical equipment or devices for local operation
    • G—PHYSICS
    • G16—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR SPECIFIC APPLICATION FIELDS
    • G16H—HEALTHCARE INFORMATICS, i.e. INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR THE HANDLING OR PROCESSING OF MEDICAL OR HEALTHCARE DATA
    • G16H50/00—ICT specially adapted for medical diagnosis, medical simulation or medical data mining; ICT specially adapted for detecting, monitoring or modelling epidemics or pandemics
    • G16H50/30—ICT specially adapted for medical diagnosis, medical simulation or medical data mining; ICT specially adapted for detecting, monitoring or modelling epidemics or pandemics for calculating health indices; for individual health risk assessment

Definitions

  • the invention relates to apparatuses and methods for monitoring foetal status.
  • the status of a foetus may comprise information indicative of foetal health and wellbeing.
  • a stillbirth also known as an intra-uterine death (IUD) is the death of a foetus that occurs between 28 to 36 weeks of gestational life.
  • IUD intra-uterine death
  • the global prevalence of stillbirths varies from two per one thousand live births in developed countries, to up to forty-two per one thousand live births in developing countries.
  • a total of approximately 2.6 million stillbirths occur across the world each year. Of these, about 45% occur when the mother is in labour, while 55% occur in the third trimester of pregnancy.
  • the causes of stillbirths include a variety of medical conditions namely poor foetal growth, maternal medical conditions (such as diabetes and hypertension), maternal infections during pregnancy, placental conditions, congenital abnormalities and
  • Foetal distress involves a number of changes in foetal homeostasis including changes in foetal heart function, and is a sign of declining foetal health. If undetected and/or untreated, foetal distress can progress to foetal death (stillbirth or IUD) in less than seventy-two hours.
  • Foetal distress can be detected by identifying abnormalities in foetal heart function such as an abnormal heart rate, reduced variability, the absence of accelerations and the presence of decelerations in foetal heart rate. This is done by measuring foetal heart rate using ultrasound technology and the interpretation of the resultant signals by specialised medical personnel.
  • Hospital based technologies are typically large, unwieldy and expensive. They typically output a foetal heart rate trace to a paper chart or display the trace on an LCD display. They require highly trained medical personnel to operate them and to interpret the outputs.
  • Home based foetal heart rate monitors typically detect and audibly output the foetal heart beat without any further interpretation of the foetal heart rate signal into measures of foetal health status. In addition, they only measure mean foetal heart rate and do not measure the other important components of the foetal heart rate signal.
  • a device for monitoring foetal status comprising a receiver configured to receive raw sensor data indicative of foetal heart rate.
  • the device also comprises a processor in electrical communication with the receiver and configured to: determine at least one parameter of the raw sensor data; compare the determined at least one parameter with corresponding predetermined criteria; determine a status of the at least one parameter based on the comparison; and generate an output based on the determined status.
  • the at least one parameter comprises a plurality of parameters
  • the processor is configured to determine a corresponding plurality of statuses, one for each of the plurality of parameters, and wherein each of the statuses may be one of normal, cautionary and abnormal.
  • the processor is configured to generate a normal output if each of the plurality of statuses is determined to be normal.
  • the processor is configured to generate a cautionary output if one or more of the plurality of statuses is determined to be cautionary.
  • the processor is configured to generate an abnormal output if each of the plurality of statuses is determined to be abnormal, or if a cautionary output is repeated.
  • the plurality of parameters comprises mean foetal heart rate, and wherein the corresponding predetermined criteria comprise minimum and maximum threshold values.
  • the processor is configured to determine that a mean foetal heart rate status is normal if the determined mean foetal heart rate is in a range from a normal minimum threshold value to a normal maximum threshold value.
  • the normal minimum threshold value is in the range form 105 beats per minute to 1 15 beats per minute and the normal maximum threshold value is in the range from 155 beats per minute to 165 beats per minute.
  • the processor is configured to determine that the mean foetal heart rate status is cautionary if the mean foetal heart rate is outside the range from the normal minimum threshold value to the normal maximum threshold value and in a range from an abnormal minimum threshold value to an abnormal maximum threshold value.
  • the abnormal minimum is in the range form 95 beats per minute to 105 beats per minute and the abnormal maximum is in the range form 165 beats per minute to 175 beats per minute.
  • the processor is configured to determine that the mean foetal heart rate status is abnormal if the mean foetal heart rate is less than the abnormal minimum threshold value or greater than the abnormal maximum threshold value.
  • the plurality of parameters comprises foetal heart rate accelerations.
  • the processor is configured to determine that the foetal heart rate accelerations are normal if two or more foetal heart rate accelerations occur in a twenty minute recording epoch and no foetal heart rate decelerations occur in the twenty minute recording epoch.
  • the processor is configured to determine that the foetal heart rate acceleration is cautionary if fewer than two foetal heart rate accelerations occur in a twenty minute recording epoch or one or more foetal heart rate decelerations occur in the twenty minute recording epoch.
  • the processor is configured to determine that the foetal heart rate acceleration is abnormal if fewer than two or more foetal heart rate accelerations occur in a twenty minute recording epoch and one or more foetal heart rate decelerations occur in the twenty minute recording epoch.
  • the plurality of parameters comprises foetal heart rate variability.
  • the processor is configured to determine that foetal heart rate variability is normal if fluctuations occur in the range from 6 to 25 beats per minute.
  • the processor is configured to determine that the foetal heart rate variability is cautionary if fluctuations of less than 6 beats; or more than 25 beats, occur per minute in a 20 minute recording epoch.
  • the processor is configured to determine that the foetal heart rate variability is abnormal if fluctuations of less than 6 beats or more than 25 beats occur per minute in a 40 minute recording.
  • the generated normal output comprises a green indication.
  • the generated cautionary output comprises an amber indication and an instruction to a user to undertake one or more steps.
  • the generated abnormal output comprises a red indication and an instruction to a user to undertake one or more steps.
  • the device further comprises a display in electrical communication with the processor and configured to receive the generated output from the processor and display it to a user.
  • the processor is further configured to summarise the output by generating summary data corresponding to a traffic light system and to control the display to display the summary data.
  • the processor is further configured to provide detailed data
  • the processor is further configured to determine instructions to a user based on the determined status of the at least one parameter and to control the display to display the instructions.
  • the device further comprises a transmitter in electrical communication with the processor, wherein the processor is further configured to control the transmitter transmit data based on the at least one determined parameter.
  • transmission of the data is via email.
  • the processor is further configured to store the generated output in one of a memory internal to the device, or to a memory located in a cloud computing network.
  • a system comprising a device for monitoring foetal status.
  • the device comprises a receiver configured to receive raw sensor data indicative of foetal heart rate.
  • the device also comprises a processor in electrical communication with the receiver and configured to: determine at least one parameter of the raw sensor data; compare the determined at least one parameter with corresponding predetermined criteria; determine a status of the at least one parameter based on the comparison; and generate an output based on the determined status.
  • the system further comprises a sensor assembly configured to obtain the raw sensor data and transmit the foetal heart rate data to the receiver.
  • the sensor assembly is configured to transmit the foetal heart rate data wirelessly.
  • a computer readable medium comprising computer readable code configured, when read by a computer, to control a processor to undertake the step of receiving raw sensor data indicative of foetal heart rate.
  • the code also undertakes the step of determining at least one parameter of the raw sensor data.
  • the code also undertakes the step of comparing the determined at least one parameter with corresponding predetermined criteria.
  • the code also undertakes the step of determining a status of the at least one parameter based on the comparison.
  • the code also undertakes the step of and generating an output based on the determined status.
  • a method for monitoring foetal health comprises: receiving, at a receiver, raw ultrasound sensor data indicative of foetal heart rate.
  • the method comprises determining, by a processor, at least one parameter of the raw sensor data.
  • the method comprises comparing, by the processor, the determined at least one parameter with corresponding predetermined criteria.
  • the method comprises determining, by the processor, a status of the at least one parameter based on the comparison.
  • the method comprises generating, by the processor, an output based on the determined status.
  • Figure 1 is a schematic block diagram of a system for monitoring foetal status
  • Figure 2 is a schematic representation of a system for monitoring foetal status fitted to an expectant mother
  • Figure 3 is a flow chart of a method for monitoring foetal status
  • Figure 4 is a table summarising exemplary values for the parameters for determining whether a status of a parameter is normal, cautionary or abnormal;
  • Figure 5 is a schematic representation of how the processor is configured to determine the status of the output;
  • Figure 6 is an exemplary screenshot of a summary output from a display of a device for monitoring foetal status
  • Figure 7 is an exemplary screenshot from a display of a detailed clinical output of a device for monitoring foetal status
  • Figure 8 is a schematic representation of a foetal heart rate signal.
  • a device preferably a handheld device, which is operable in the home by unskilled users and is capable of one or more of:
  • the apparatuses and methods may receive raw sensor data indicative of foetal health and process that data to determine one or more parameters.
  • the parameters may be used to determine and generate an output indicative of foetal health and display this to a user.
  • Figure 1 shows a system 100 for foetal monitoring.
  • the system 100 comprises a sensor assembly 102 that is configured to measure foetal heart rate data and transmit the data to a device 104.
  • the device 104 comprises a receiver 106, a processor 108, a memory 109 and a display 1 10.
  • the receiver 106 is in electrical communication with the processor 108.
  • the processor 108 is in electrical communication with the display 1 10 and the memory 109.
  • the sensor assembly 102 comprises an array of one or more ultrasound
  • the sensor assembly is equipped with a wireless transceiver that is configured to transmit raw reflected ultrasound data to the receiver 106 of the device 104.
  • the sensor assembly 102 may also use alternative technology capable of sensing foetal heart rate. Further, the sensor assembly 102 may be configured to transmit the raw sensor data to the receiver 106 via alternative wireless transmission methods, or by a wired connection.
  • the sensor assembly 102 is configured to be positioned in contact with the skin of a subject's abdomen and may comprise straps configured to hold the sensor assembly 102 in position on the subject.
  • the receiver 106 is configured to receive the raw sensor data from the sensor assembly 102.
  • the receiver 106 transmits the received data to the processor 108.
  • the processor 108 comprises at least one microprocessor utility and is generally configured to process the raw sensor data and provide an output for display by the display 1 10.
  • the processor 108 may also be configured to store raw and/or processed foetal heart rate data in the memory 109 for comparison of multiple foetal monitoring sessions to determine long term trends in foetal health.
  • the stored data may be
  • the processor 108 may be further configured to connect to a computer network, such as the Internet, to send raw and/or processed foetal heart rate data to a third party, for example a medical professional.
  • a computer network such as the Internet
  • the processor 108 may be further configured to plot a trace of foetal heart rate to the display or to a printer, to which the device may be electrically connected.
  • the processor 108 is configured to automate the interpretation of the foetal heart rate signal according to clinical guidelines, and to present the result to the user on the display unit of the device 104.
  • the processor 108 may also be configured to generate a set of user prompts for each foetal heart rate output scenario according to clinically prescribed guidelines, and to present these user prompts to the user on the display unit 1 10 of the device 104.
  • the device 104 may be a handheld device. That is, the device 104 may be sized appropriately to fit within the hand of a user during operation. Alternatively, the device 104 may be a portable device. That is, the device may be sized appropriately to be portable by a user and carried by the user from one place to another. Exemplary devices 104 may be a smartphone, a PDA, a laptop or another handheld device comprising a computer processing capability. Specific exemplary devices may comprise a custom built device comprising a computer processing utility.
  • Figure 2 shows the system 100, with the sensor assembly 102 fitted to a subject 200.
  • the sensor assembly 102 is secured in position on the abdomen of the subject 200 by a strap 202 and transmits the raw sensor data to the device 104, which in the example of figure 2 is a smartphone.
  • Figure 3 shows a flow chart of a method for monitoring foetal health.
  • the sensor assembly 102 transmits 300 an ultrasound signal into the abdomen of the subject 200. Reflected signals are received from within the abdomen and are received by the sensor assembly 102 where they are converted into an electrical signal. The frequency of the signals reflected from the moving walls of the foetal heart is shifted in accordance with the Doppler effect.
  • the sensor assembly 102 transmits 302 raw sensor data, which comprises the reflected ultrasound signals, to the receiver 106 of the device 104, which then transmits 304 the raw sensor data to the processor 108.
  • the raw sensor data is processed by the device 104 to identify components specific to the foetal heart rate.
  • the processor 108 can be configured to generate a message to a user on the display unit of the device 104 to reposition the sensor assembly 102.
  • the raw sensor data is demodulated in a phase detector, which may be a circuit or may be embodied in software, to obtain differential frequencies describing the movements within the ultrasound signal and located in the acoustic frequency band.
  • a phase detector which may be a circuit or may be embodied in software, to obtain differential frequencies describing the movements within the ultrasound signal and located in the acoustic frequency band.
  • the processor 108 obtains an instantaneous foetal heart rate by measuring the time between the peaks and calculating the number of heart beats that would occur with that period in a minute.
  • a sequence of instantaneous foetal heart rates forms a signal, referred to here as foetal heart rate (FHR) and measured in beats per minute.
  • FHR foetal heart rate
  • the FHR includes a noise element formed by the superposition of signals arising by mechanical activity in the interior of the subject 200, for example cardiac activity, breathing activity, and bowel movements.
  • the processor 108 separates a portion of the FHR signal relating to the movement of the heart of the foetus from a portion of the FHR signal relating to the noise 306.
  • an MR filter for example, a low-pass Butterworth filter of 20-th order with cut-off at 1 Hz
  • a wavelet based de- noising method may be applied to the FHR (such as by soft-thresholding the wavelet transform and inverse transforming the de-noised wavelet coefficients).
  • the processor 108 extracts parameters indicative of the wellbeing of the foetus, for example: baseline foetal heart rate, number of foetal heart rate accelerations, number of foetal heart rate decelerations, and beat to beat variability per minute.
  • the baseline foetal heart rate is a low order approximation of the FHR, i.e. a smooth curve.
  • the baseline FHR is obtained by an iterative process in which segments of accelerations and/or decelerations are discarded, and the high frequencies of the remaining signal are filtered out.
  • the foetal heart rate accelerations and foetal heart rate decelerations correspond to the segments of the FHR that are above or below certain thresholds with respect to the baseline foetal heart rate, and extend over a certain period of time as set out in more detail below.
  • Baseline foetal heart rate, foetal heart rate accelerations and foetal heart rate decelerations can be obtained 308, 310 by an iterative procedure as follows.
  • An initial baseline foetal heart rate is constructed by assuming that all foetal heart rate accelerations and foetal heart rate decelerations are above and below initial thresholds either side of a mean value of the FHR.
  • the mean value may be determined over an entire recording epoch of, for example, 10 minutes.
  • the FHR is greater than an upper threshold, which is set higher than the mean FHR, this is determined to be a foetal heart rate acceleration. If the FHR is less than a lower threshold, which is set below the mean FHR, this is determined to be a foetal heart rate deceleration. Any portions of foetal heart rate identified as foetal heart rate
  • the resulting signal i.e. with foetal heart rate accelerations and decelerations removed, is then smoothed, for example by processing it through a Butterworth low-pass filter of first order.
  • the smoothed signal is the determined initial baseline foetal heart rate.
  • the next iteration begins by identifying foetal heart rate accelerations as portions of the FHR that are greater than the initial baseline foetal heart rate (calculated in the previous step) by, for example, 15 beats per minute or more at an average rate of 5 beats per minute per second or more and remains at least 15 beats per minute or more above the calculated initial baseline foetal heart rate for at least 15 seconds.
  • foetal heart rate decelerations are identified as portions of the FHR that are less than the calculated baseline foetal heart rate by, for example, 15 beats per minute or more at an average rate of 5 beats per minute per second or more and remain at least 15 beats per minute or more below the calculated baseline foetal heart rate for at least 15 seconds.
  • a new baseline foetal heart rate is constructed following the procedure described in the previous paragraph, i.e. removing the foetal heart rate accelerations and decelerations from the FHR and smoothing to determine a new baseline foetal heart rate. The process is repeated until the determined baseline foetal heart rate converges within a certain tolerance.
  • the foetal heart rate accelerations and decelerations also converge along with the baseline foetal heart rate.
  • the method described above therefore results in converged foetal heart rate accelerations and decelerations.
  • the number of foetal heart rate accelerations and decelerations are also determined.
  • the foetal heart rate accelerations and decelerations may be plotted against time to produce a curve for each.
  • the areas under the curves of foetal heart rate accelerations and decelerations can be calculated, for example, by adding the integral of low degree polynomials, fitted to the signal in the least-squares sense, in windows of ten seconds.
  • Foetal heart rate variability is now determined 312.
  • Foetal heart rate variability is represented by fluctuations in baseline foetal heart rate of 6 to 25 beats per minute. It is determined by computing the average baseline foetal heart rate for each 60 second recording epoch, and computing the difference in these averages between adjacent minutes as absolute values.
  • Foetal heart rate variability is a function of the baseline foetal heart rate of important positive prognostic significance and is indicative of positive foetal health. The normal range for foetal heart rate variability from plus or minus 6 to 25 beats per minute from the baseline foetal heart rate. Decreased foetal heart rate variability or an absence of foetal heart rate variability is indicative of severe compromises in foetal health and impending, or concurrent, foetal distress.
  • the status of the foetal heart rate variability is determined to be cautionary. That is, if the foetal heart rate variability is less than 6 beats per minute, the status is determined to be cautionary.
  • the status of the parameters may be based on the Non Stress Test, which is a clinical standard used to determine whether a foetus is "reactive" or "non-reactive". A reactive foetus is considered broadly to be healthy and a non-reactive foetus may be experiencing some foetal distress and may indicate an unhealthy foetus.
  • the baseline foetal heart rate, the foetal heart rate accelerations, the foetal heart rate decelerations and the foetal heart rate variability are compared to predetermined criteria 314 to determine their status 316.
  • the status of each parameter may be "normal”, “cautionary” or "abnormal” as set out below.
  • the baseline foetal heart rate is compared to threshold values that define a normal range and an abnormal range. Specifically, if the average of the determined baseline foetal heart rate over the entire recording is in a range from a normal minimum threshold value to a normal maximum threshold value, the status of the baseline foetal heart rate is determined to be normal.
  • An exemplary normal minimum threshold value may be in the range from 105 beats per minute to 1 15 beats per minute or, specifically, 1 10 beats per minute.
  • An exemplary normal maximum threshold value may be in the range from 155 beats per minute to 165 beats per minute or, specifically 160 beats per minute. If the average of the determined baseline foetal heart rate over the entire recording is outside the range from the normal minimum threshold value to the normal maximum threshold value, but within a range from a lower abnormal threshold value to an upper abnormal threshold value, the status of the baseline foetal heart rate is determined to be 'cautionary', i.e. to require further monitoring.
  • a 'cautionary' status acknowledges that a parameter is not within normal limits, but is not considered to be a serious risk to foetal health. Therefore, a cautionary status can be considered to lie between a normal status and an abnormal status. If the average of the determined baseline foetal heart rate over the entire recording is above the abnormal maximum threshold or below the abnormal minimum threshold, the processor 108 determines that the baseline foetal heart rate status is abnormal.
  • An exemplary abnormal minimum threshold value may be in the range from 95 beats per minute to 105 beats per minute, and, specifically, may be 100 beats per minute.
  • An exemplary abnormal maximum threshold value may be in the range from 165 beats per minute to 175 beats per minute and, specifically, may be 170 beats per minute.
  • the foetal heart rate accelerations are a function of foetal heart rate with an important positive prognostic significance and are indicative of positive foetal health and adequate foetal oxygenation.
  • the foetal heart rate accelerations are compared to predetermined criteria.
  • foetal heart rate accelerations are identified during the iterative process. Specifically, if the determined foetal heart rate increases above the baseline foetal heart rate by 15 beats per minute or more at an average rate of 5 beats per minute per second or more and remains at least 15 beats per minute or more above the baseline foetal heart rate for at least 15 seconds, the processor 108 determines that a foetal heart rate acceleration has occurred.
  • the processor 108 determines the total number of foetal heart rate accelerations in the epoch
  • the processor determines that two or more foetal heart rate accelerations occur in a recording epoch of twenty minutes, the status of the foetal heart rate acceleration parameter is determined to be normal.
  • the processor 108 determines the presence of less than two foetal heart rate accelerations in a 20 minute recording epoch, the status of the foetal heart rate acceleration parameter is determined to be cautionary. This is indicative of impending compromises in foetal health.
  • the processor 108 determines the presence of less than two foetal heart rate accelerations in a 40 minute recording epoch, the status of the foetal heart rate acceleration parameter is determined to be abnormal. This is indicative of impending, or concurrent, foetal distress.
  • foetal heart rate decelerations are identified during the iterative process discussed above. Specifically, if the determined foetal heart rate decreases below the baseline foetal heart rate by 15 beats per minute or more at an average rate of 5 beats per minute per second or more and remains at least 15 beats per minute or more below the baseline foetal heart rate for at least 15 seconds, the processor 108 determines that a foetal heart rate deceleration has occurred.
  • the processor 108 determines the total number of foetal heart rate decelerations in the epoch, Foetal heart rate decelerations are functions of foetal heart rate with an important negative prognostic significance. Their presence is indicative of severe compromises in foetal health and impending, or concurrent, foetal distress. If the processor 108 determines that no foetal heart rate decelerations occur in a recording epoch of, twenty minutes, the status of the foetal heart rate deceleration parameter is determined to be normal.
  • the processor 108 determines that one or more foetal heart rate decelerations, each lasting less than 60 seconds in duration, occur in the twenty minute recording epoch, the status of the foetal heart rate deceleration parameter is determined to be cautionary. This is indicative of impending compromises in foetal health. If the processor 108 determines that one or more foetal heart rate decelerations, at least one of which lasts 60 or more seconds in duration, occur in the twenty minute recording epoch, the status of the foetal heart rate deceleration parameter is determined to be abnormal. This is indicative of impending, or concurrent, foetal distress. At the end of each recording epoch, the processor 108 determines the foetal heart rate variability for that epoch.
  • the processor 108 determines a foetal heart rate variability in a range from 6-25 beats per minute during a 20 minute recording epoch, the status of the foetal heart rate variability is determined to be normal.
  • the processor 108 determines a foetal heart rate variability of less than 6 beats per minute or greater than 25 beats per minute during a 20 minute recording epoch, the status of the foetal heart rate variability is determined to be cautionary. This is indicative of impending compromises in foetal health.
  • the processor 108 determines a foetal heart rate variability of less than 6 beats per minute or greater than 25 beats per minute during a 40 minute recording epoch, the status of the foetal heart rate variability is determined to be abnormal. This is indicative of impending, or concurrent, foetal distress.
  • the processor 108 may be configured to determine that the status of the foetus is normal if the parameters described above satisfy certain clinical guidelines. For example, in one embodiment of the exemplary device, the processor 108 may be configured to determine the status of the foetus according to the Non Stress Test which dictates that if baseline foetal heart rate is within the normal minimum and normal maximum thresholds, two or more accelerations occur within a twenty minute period, no decelerations occur, and foetal heart rate variability is within normal limits the foetus is considered to be healthy.
  • Figure 4 shows a table summarising exemplary values for the parameters for determining whether a status of a parameter is normal, cautionary or abnormal.
  • the status of each of the parameters is determined 316 based on the comparison of the parameter to the corresponding predetermined criteria.
  • the determined statuses are used by the processor 108 to generate an output and display it 318 to a user on the display 1 10.
  • the processor 108 generates a normal output if the status of each of the parameters is determined to be normal.
  • the processor 108 generates a cautionary output if one or more of the statuses of the parameters are determined to be cautionary.
  • the processor 108 generates an abnormal output if the status of each of the parameters is determined to be abnormal or if, following repeated or continuous monitoring within a sixty minute period, a cautionary warning is detected for more than fifty percent of the recordings, i.e. for more than 30 minutes of recording time.
  • the outputs may be displayed to a user in a "traffic light" sequence. That is, a normal output may be displayed as a green indication to a user, a cautionary output may be displayed as an amber indication to a user and an abnormal output may be displayed as a red indication to a user.
  • the traffic light sequence is used throughout the remainder of the document for clarity.
  • Figure 5 shows a schematic representation of how the processor is configured to determine the status of the output.
  • the status of each of the parameters 500a-d is determined to be one of Normal (N), Cautionary (C) or Abnormal (A). This is shown at references 502a-d. If the status of each parameter 500a-d is normal, the status of the output is normal 504a, which corresponds to a green output. If the status of at least one parameter 500a-d is cautionary, the status of the output is cautionary 504b, which corresponds to an amber output. If the status of all parameters 500a-d are abnormal, the status of the output is abnormal 504c, which corresponds to a red output. In addition to the green, amber and red outputs referred to above, messages and other information may also be displayed to a user as part of the generated output.
  • N Normal
  • C Cautionary
  • A Abnormal
  • Figure 6 shows a screen shot of an exemplary green output.
  • the "green” light 600 of the traffic lights 602 is shown enlarged and this will be coloured green.
  • the text "your baby is normal” appears on the display.
  • a series of soft keys 604a-g are located along the bottom of the screen and provide additional functionality.
  • soft key 604a instructs the processor 108 to save the foetal monitoring session data
  • soft key 604b instructs the processor 108 to email the session data to a designated email account, for example the email account of a medical professional or a family member.
  • the email addresses may already be stored in the device
  • soft key 604c instructs the processor 108 to repeat the test.
  • the user may be instructed to gently prod the baby until they feel it move, then repeat the test. If the situation is the same or worsens on completion of two or more repeat tests, the generated output becomes red.
  • the numerical values of the parameters computed, their normal ranges and the final green/amber/red output generated are stored in a memory that can be accessed by the user if required. This may be displayed to the user as a spreadsheet such as shown in Figure 7.
  • the processor 108 may also be configured to repeat the test automatically if certain conditions exist. For example, if a deceleration is determined during a test, the processor 108 may be configured to repeat the test twice. If a deceleration is again determined then the generated output will become red, or abnormal. Additional information and instruction may be displayed to the user as part generated output.
  • Figure 8 is a plot of foetal heart rate data against time showing a foetal heart rate acceleration 800, a region of baseline foetal heart rate 802 and a region showing foetal heart rate variability 804.
  • the apparatuses and methods described herein provide a high degree of accuracy when monitoring foetal health.
  • the parameters of the raw sensor data are determined by eye by a skilled operative.
  • Known home based technologies generally provide no output other than an audible heart beat sound and perhaps a trace of foetal heart rate.
  • the apparatuses and methods disclosed herein may be used easily by expectant mothers and unskilled operators to give a useful assessment of raw data indicative of foetal heart rate.

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Abstract

The invention relates to a device for monitoring foetal status. The device comprises a receiver configured to receive raw sensor data indicative of foetal heart rate. The device also comprises a processor in electrical communication with the receiver and configured to: determine at least one parameter of the raw sensor data; compare the determined at least one parameter with corresponding predetermined criteria; determine a status of the at least one parameter based on the comparison; and generate an output based on the determined status. The device may also comprise a display in electrical communication with the processor and configured to display the output to a user.

Description

FOETAL MONITORING Technical field The invention relates to apparatuses and methods for monitoring foetal status. The status of a foetus may comprise information indicative of foetal health and wellbeing.
Background A stillbirth, also known as an intra-uterine death (IUD), is the death of a foetus that occurs between 28 to 36 weeks of gestational life. The global prevalence of stillbirths varies from two per one thousand live births in developed countries, to up to forty-two per one thousand live births in developing countries. A total of approximately 2.6 million stillbirths occur across the world each year. Of these, about 45% occur when the mother is in labour, while 55% occur in the third trimester of pregnancy.
The causes of stillbirths include a variety of medical conditions namely poor foetal growth, maternal medical conditions (such as diabetes and hypertension), maternal infections during pregnancy, placental conditions, congenital abnormalities and
complications during the process of childbirth. These disorders result in a condition of poor foetal functioning, called 'foetal distress'. Foetal distress involves a number of changes in foetal homeostasis including changes in foetal heart function, and is a sign of declining foetal health. If undetected and/or untreated, foetal distress can progress to foetal death (stillbirth or IUD) in less than seventy-two hours.
Foetal distress can be detected by identifying abnormalities in foetal heart function such as an abnormal heart rate, reduced variability, the absence of accelerations and the presence of decelerations in foetal heart rate. This is done by measuring foetal heart rate using ultrasound technology and the interpretation of the resultant signals by specialised medical personnel.
Current technologies for monitoring foetal heart rate fall into two broad categories: hospital based equipments; and home based equipments. Hospital based technologies, are typically large, unwieldy and expensive. They typically output a foetal heart rate trace to a paper chart or display the trace on an LCD display. They require highly trained medical personnel to operate them and to interpret the outputs. Home based foetal heart rate monitors typically detect and audibly output the foetal heart beat without any further interpretation of the foetal heart rate signal into measures of foetal health status. In addition, they only measure mean foetal heart rate and do not measure the other important components of the foetal heart rate signal.
In both the western and developing world, the number of times a foetus can be monitored to detect disturbances in its heart function (and therefore health status) is limited to 3-6 times during the entire 9 months of pregnancy. This is because hospital based technologies are too resource intensive to monitor foetal health on a regular basis. The home based foetal heart rate monitors do not characterise the foetal heart rate signal accurately, and do not measure most, if not all, the relevant components of foetal heart rate. Further, in developing nations, the equipments required to monitor foetal health can be prohibitively expensive. These factors contribute significantly to both the high rate of stillbirths, and the high rates of severe medical illness in the newborn.
Summary
According to the invention in a first aspect, there is provided a device for monitoring foetal status. The device comprises a receiver configured to receive raw sensor data indicative of foetal heart rate. The device also comprises a processor in electrical communication with the receiver and configured to: determine at least one parameter of the raw sensor data; compare the determined at least one parameter with corresponding predetermined criteria; determine a status of the at least one parameter based on the comparison; and generate an output based on the determined status.
Optionally, the at least one parameter comprises a plurality of parameters, and wherein the processor is configured to determine a corresponding plurality of statuses, one for each of the plurality of parameters, and wherein each of the statuses may be one of normal, cautionary and abnormal.
Optionally, the processor is configured to generate a normal output if each of the plurality of statuses is determined to be normal. Optionally, the processor is configured to generate a cautionary output if one or more of the plurality of statuses is determined to be cautionary.
Optionally, the processor is configured to generate an abnormal output if each of the plurality of statuses is determined to be abnormal, or if a cautionary output is repeated.
Optionally, the plurality of parameters comprises mean foetal heart rate, and wherein the corresponding predetermined criteria comprise minimum and maximum threshold values.
Optionally, the processor is configured to determine that a mean foetal heart rate status is normal if the determined mean foetal heart rate is in a range from a normal minimum threshold value to a normal maximum threshold value. Optionally, the normal minimum threshold value is in the range form 105 beats per minute to 1 15 beats per minute and the normal maximum threshold value is in the range from 155 beats per minute to 165 beats per minute.
Optionally, the processor is configured to determine that the mean foetal heart rate status is cautionary if the mean foetal heart rate is outside the range from the normal minimum threshold value to the normal maximum threshold value and in a range from an abnormal minimum threshold value to an abnormal maximum threshold value.
Optionally, the abnormal minimum is in the range form 95 beats per minute to 105 beats per minute and the abnormal maximum is in the range form 165 beats per minute to 175 beats per minute.
Optionally, the processor is configured to determine that the mean foetal heart rate status is abnormal if the mean foetal heart rate is less than the abnormal minimum threshold value or greater than the abnormal maximum threshold value.
Optionally, the plurality of parameters comprises foetal heart rate accelerations.
Optionally, the processor is configured to determine that the foetal heart rate accelerations are normal if two or more foetal heart rate accelerations occur in a twenty minute recording epoch and no foetal heart rate decelerations occur in the twenty minute recording epoch.
Optionally, the processor is configured to determine that the foetal heart rate acceleration is cautionary if fewer than two foetal heart rate accelerations occur in a twenty minute recording epoch or one or more foetal heart rate decelerations occur in the twenty minute recording epoch.
Optionally, the processor is configured to determine that the foetal heart rate acceleration is abnormal if fewer than two or more foetal heart rate accelerations occur in a twenty minute recording epoch and one or more foetal heart rate decelerations occur in the twenty minute recording epoch.
Optionally, the plurality of parameters comprises foetal heart rate variability.
Optionally, the processor is configured to determine that foetal heart rate variability is normal if fluctuations occur in the range from 6 to 25 beats per minute.
Optionally, the processor is configured to determine that the foetal heart rate variability is cautionary if fluctuations of less than 6 beats; or more than 25 beats, occur per minute in a 20 minute recording epoch.
Optionally, the processor is configured to determine that the foetal heart rate variability is abnormal if fluctuations of less than 6 beats or more than 25 beats occur per minute in a 40 minute recording.
Optionally, the generated normal output comprises a green indication.
Optionally, the generated cautionary output comprises an amber indication and an instruction to a user to undertake one or more steps.
Optionally, the generated abnormal output comprises a red indication and an instruction to a user to undertake one or more steps. Optionally, the device further comprises a display in electrical communication with the processor and configured to receive the generated output from the processor and display it to a user. Optionally, the processor is further configured to summarise the output by generating summary data corresponding to a traffic light system and to control the display to display the summary data.
Optionally, the processor is further configured to provide detailed data
corresponding to the value of the determined at least one parameter to control the display to display the detailed data.
Optionally, the processor is further configured to determine instructions to a user based on the determined status of the at least one parameter and to control the display to display the instructions.
Optionally, the device further comprises a transmitter in electrical communication with the processor, wherein the processor is further configured to control the transmitter transmit data based on the at least one determined parameter.
Optionally, transmission of the data is via email.
Optionally, the processor is further configured to store the generated output in one of a memory internal to the device, or to a memory located in a cloud computing network.
According to the invention in a second aspect, there is provided a system comprising a device for monitoring foetal status. The device comprises a receiver configured to receive raw sensor data indicative of foetal heart rate. The device also comprises a processor in electrical communication with the receiver and configured to: determine at least one parameter of the raw sensor data; compare the determined at least one parameter with corresponding predetermined criteria; determine a status of the at least one parameter based on the comparison; and generate an output based on the determined status. The system further comprises a sensor assembly configured to obtain the raw sensor data and transmit the foetal heart rate data to the receiver. Optionally, the sensor assembly is configured to transmit the foetal heart rate data wirelessly.
According to the invention in a third aspect, there is provided a computer readable medium comprising computer readable code configured, when read by a computer, to control a processor to undertake the step of receiving raw sensor data indicative of foetal heart rate. The code also undertakes the step of determining at least one parameter of the raw sensor data. The code also undertakes the step of comparing the determined at least one parameter with corresponding predetermined criteria. The code also undertakes the step of determining a status of the at least one parameter based on the comparison. The code also undertakes the step of and generating an output based on the determined status.
According to the invention in a third aspect, there is provided a method for monitoring foetal health. The method comprises: receiving, at a receiver, raw ultrasound sensor data indicative of foetal heart rate. The method comprises determining, by a processor, at least one parameter of the raw sensor data. The method comprises comparing, by the processor, the determined at least one parameter with corresponding predetermined criteria. The method comprises determining, by the processor, a status of the at least one parameter based on the comparison. The method comprises generating, by the processor, an output based on the determined status.
Brief description of the drawings
Exemplary embodiments of the invention will now be described with reference to the accompanying drawings, in which:
Figure 1 is a schematic block diagram of a system for monitoring foetal status;
Figure 2 is a schematic representation of a system for monitoring foetal status fitted to an expectant mother;
Figure 3 is a flow chart of a method for monitoring foetal status;
Figure 4 is a table summarising exemplary values for the parameters for determining whether a status of a parameter is normal, cautionary or abnormal; Figure 5 is a schematic representation of how the processor is configured to determine the status of the output;
Figure 6 is an exemplary screenshot of a summary output from a display of a device for monitoring foetal status;
Figure 7 is an exemplary screenshot from a display of a detailed clinical output of a device for monitoring foetal status; and Figure 8 is a schematic representation of a foetal heart rate signal.
Description
The inventors have appreciated that there is a need for a device, preferably a handheld device, which is operable in the home by unskilled users and is capable of one or more of:
• Measuring foetal health using foetal heart rate data with a high degree of precision;
• Processing foetal heart rate data to provide relevant user information indicative of foetal heath to detect foetal distress early;
• Presenting user information to a user, such as an expectant mother or healthcare worker, in an easily understood manner that does not require specialist training;
• Prompting the user into further action when necessary;
• Offering the possibility to store and transfer data to a medical professional if
required; and
• Being portable and usable anytime and anywhere.
Generally, disclosed herein are apparatuses and methods for monitoring foetal health. The apparatuses and methods may receive raw sensor data indicative of foetal health and process that data to determine one or more parameters. The parameters may be used to determine and generate an output indicative of foetal health and display this to a user.
Figure 1 shows a system 100 for foetal monitoring. The system 100 comprises a sensor assembly 102 that is configured to measure foetal heart rate data and transmit the data to a device 104. The device 104 comprises a receiver 106, a processor 108, a memory 109 and a display 1 10. The receiver 106 is in electrical communication with the processor 108. The processor 108 is in electrical communication with the display 1 10 and the memory 109.
The sensor assembly 102 comprises an array of one or more ultrasound
transceivers and is configured to transmit a 1 -3 MHz ultrasound signal into the womb of an expectant mother and receive a reflected signal. The sensor assembly is equipped with a wireless transceiver that is configured to transmit raw reflected ultrasound data to the receiver 106 of the device 104. The sensor assembly 102 may also use alternative technology capable of sensing foetal heart rate. Further, the sensor assembly 102 may be configured to transmit the raw sensor data to the receiver 106 via alternative wireless transmission methods, or by a wired connection. The sensor assembly 102 is configured to be positioned in contact with the skin of a subject's abdomen and may comprise straps configured to hold the sensor assembly 102 in position on the subject.
The receiver 106 is configured to receive the raw sensor data from the sensor assembly 102. The receiver 106 transmits the received data to the processor 108. The processor 108 comprises at least one microprocessor utility and is generally configured to process the raw sensor data and provide an output for display by the display 1 10.
The processor 108 may also be configured to store raw and/or processed foetal heart rate data in the memory 109 for comparison of multiple foetal monitoring sessions to determine long term trends in foetal health. In addition, the stored data may be
downloaded to another device, such as a desktop computer or other processing device, at a later time. The processor 108 may be further configured to connect to a computer network, such as the Internet, to send raw and/or processed foetal heart rate data to a third party, for example a medical professional.
The processor 108 may be further configured to plot a trace of foetal heart rate to the display or to a printer, to which the device may be electrically connected. The processor 108 is configured to automate the interpretation of the foetal heart rate signal according to clinical guidelines, and to present the result to the user on the display unit of the device 104. The processor 108 may also be configured to generate a set of user prompts for each foetal heart rate output scenario according to clinically prescribed guidelines, and to present these user prompts to the user on the display unit 1 10 of the device 104.
The device 104 may be a handheld device. That is, the device 104 may be sized appropriately to fit within the hand of a user during operation. Alternatively, the device 104 may be a portable device. That is, the device may be sized appropriately to be portable by a user and carried by the user from one place to another. Exemplary devices 104 may be a smartphone, a PDA, a laptop or another handheld device comprising a computer processing capability. Specific exemplary devices may comprise a custom built device comprising a computer processing utility.
Figure 2 shows the system 100, with the sensor assembly 102 fitted to a subject 200. The sensor assembly 102 is secured in position on the abdomen of the subject 200 by a strap 202 and transmits the raw sensor data to the device 104, which in the example of figure 2 is a smartphone.
Figure 3 shows a flow chart of a method for monitoring foetal health.
The sensor assembly 102 transmits 300 an ultrasound signal into the abdomen of the subject 200. Reflected signals are received from within the abdomen and are received by the sensor assembly 102 where they are converted into an electrical signal. The frequency of the signals reflected from the moving walls of the foetal heart is shifted in accordance with the Doppler effect.
The sensor assembly 102 transmits 302 raw sensor data, which comprises the reflected ultrasound signals, to the receiver 106 of the device 104, which then transmits 304 the raw sensor data to the processor 108.
In exemplary systems, the raw sensor data is processed by the device 104 to identify components specific to the foetal heart rate. In the event that these components are not identified, the processor 108 can be configured to generate a message to a user on the display unit of the device 104 to reposition the sensor assembly 102.
The raw sensor data is demodulated in a phase detector, which may be a circuit or may be embodied in software, to obtain differential frequencies describing the movements within the ultrasound signal and located in the acoustic frequency band. For each contiguous pair of peaks of the demodulated raw sensor data waveform, the processor 108 obtains an instantaneous foetal heart rate by measuring the time between the peaks and calculating the number of heart beats that would occur with that period in a minute. A sequence of instantaneous foetal heart rates forms a signal, referred to here as foetal heart rate (FHR) and measured in beats per minute.
The FHR includes a noise element formed by the superposition of signals arising by mechanical activity in the interior of the subject 200, for example cardiac activity, breathing activity, and bowel movements.
The processor 108 separates a portion of the FHR signal relating to the movement of the heart of the foetus from a portion of the FHR signal relating to the noise 306. For this de-noising procedure, an MR filter (for example, a low-pass Butterworth filter of 20-th order with cut-off at 1 Hz) may be applied to the FHR signal. Alternatively, a wavelet based de- noising method may be applied to the FHR (such as by soft-thresholding the wavelet transform and inverse transforming the de-noised wavelet coefficients).
From the de-noised FHR, the processor 108 extracts parameters indicative of the wellbeing of the foetus, for example: baseline foetal heart rate, number of foetal heart rate accelerations, number of foetal heart rate decelerations, and beat to beat variability per minute.
The baseline foetal heart rate is a low order approximation of the FHR, i.e. a smooth curve. The baseline FHR is obtained by an iterative process in which segments of accelerations and/or decelerations are discarded, and the high frequencies of the remaining signal are filtered out. The foetal heart rate accelerations and foetal heart rate decelerations correspond to the segments of the FHR that are above or below certain thresholds with respect to the baseline foetal heart rate, and extend over a certain period of time as set out in more detail below. Baseline foetal heart rate, foetal heart rate accelerations and foetal heart rate decelerations can be obtained 308, 310 by an iterative procedure as follows.
An initial baseline foetal heart rate is constructed by assuming that all foetal heart rate accelerations and foetal heart rate decelerations are above and below initial thresholds either side of a mean value of the FHR. The mean value may be determined over an entire recording epoch of, for example, 10 minutes.
If the FHR is greater than an upper threshold, which is set higher than the mean FHR, this is determined to be a foetal heart rate acceleration. If the FHR is less than a lower threshold, which is set below the mean FHR, this is determined to be a foetal heart rate deceleration. Any portions of foetal heart rate identified as foetal heart rate
accelerations or decelerations are not considered in the calculation of the baseline foetal heart rate.
The resulting signal, i.e. with foetal heart rate accelerations and decelerations removed, is then smoothed, for example by processing it through a Butterworth low-pass filter of first order. The smoothed signal is the determined initial baseline foetal heart rate. The next iteration begins by identifying foetal heart rate accelerations as portions of the FHR that are greater than the initial baseline foetal heart rate (calculated in the previous step) by, for example, 15 beats per minute or more at an average rate of 5 beats per minute per second or more and remains at least 15 beats per minute or more above the calculated initial baseline foetal heart rate for at least 15 seconds. Similarly, foetal heart rate decelerations are identified as portions of the FHR that are less than the calculated baseline foetal heart rate by, for example, 15 beats per minute or more at an average rate of 5 beats per minute per second or more and remain at least 15 beats per minute or more below the calculated baseline foetal heart rate for at least 15 seconds. With these foetal heart rate accelerations and decelerations, a new baseline foetal heart rate is constructed following the procedure described in the previous paragraph, i.e. removing the foetal heart rate accelerations and decelerations from the FHR and smoothing to determine a new baseline foetal heart rate. The process is repeated until the determined baseline foetal heart rate converges within a certain tolerance. The foetal heart rate accelerations and decelerations also converge along with the baseline foetal heart rate. The method described above therefore results in converged foetal heart rate accelerations and decelerations. The number of foetal heart rate accelerations and decelerations are also determined.
The foetal heart rate accelerations and decelerations may be plotted against time to produce a curve for each. The areas under the curves of foetal heart rate accelerations and decelerations can be calculated, for example, by adding the integral of low degree polynomials, fitted to the signal in the least-squares sense, in windows of ten seconds.
Foetal heart rate variability is now determined 312. Foetal heart rate variability is represented by fluctuations in baseline foetal heart rate of 6 to 25 beats per minute. It is determined by computing the average baseline foetal heart rate for each 60 second recording epoch, and computing the difference in these averages between adjacent minutes as absolute values. Foetal heart rate variability is a function of the baseline foetal heart rate of important positive prognostic significance and is indicative of positive foetal health. The normal range for foetal heart rate variability from plus or minus 6 to 25 beats per minute from the baseline foetal heart rate. Decreased foetal heart rate variability or an absence of foetal heart rate variability is indicative of severe compromises in foetal health and impending, or concurrent, foetal distress. In conditions of decreased or absent foetal heart rate variability, the status of the foetal heart rate variability is determined to be cautionary. That is, if the foetal heart rate variability is less than 6 beats per minute, the status is determined to be cautionary. The status of the parameters may be based on the Non Stress Test, which is a clinical standard used to determine whether a foetus is "reactive" or "non-reactive". A reactive foetus is considered broadly to be healthy and a non-reactive foetus may be experiencing some foetal distress and may indicate an unhealthy foetus. The baseline foetal heart rate, the foetal heart rate accelerations, the foetal heart rate decelerations and the foetal heart rate variability are compared to predetermined criteria 314 to determine their status 316. The status of each parameter may be "normal", "cautionary" or "abnormal" as set out below. The baseline foetal heart rate is compared to threshold values that define a normal range and an abnormal range. Specifically, if the average of the determined baseline foetal heart rate over the entire recording is in a range from a normal minimum threshold value to a normal maximum threshold value, the status of the baseline foetal heart rate is determined to be normal. An exemplary normal minimum threshold value may be in the range from 105 beats per minute to 1 15 beats per minute or, specifically, 1 10 beats per minute. An exemplary normal maximum threshold value may be in the range from 155 beats per minute to 165 beats per minute or, specifically 160 beats per minute. If the average of the determined baseline foetal heart rate over the entire recording is outside the range from the normal minimum threshold value to the normal maximum threshold value, but within a range from a lower abnormal threshold value to an upper abnormal threshold value, the status of the baseline foetal heart rate is determined to be 'cautionary', i.e. to require further monitoring.
Generally, a 'cautionary' status acknowledges that a parameter is not within normal limits, but is not considered to be a serious risk to foetal health. Therefore, a cautionary status can be considered to lie between a normal status and an abnormal status. If the average of the determined baseline foetal heart rate over the entire recording is above the abnormal maximum threshold or below the abnormal minimum threshold, the processor 108 determines that the baseline foetal heart rate status is abnormal.
An exemplary abnormal minimum threshold value may be in the range from 95 beats per minute to 105 beats per minute, and, specifically, may be 100 beats per minute. An exemplary abnormal maximum threshold value may be in the range from 165 beats per minute to 175 beats per minute and, specifically, may be 170 beats per minute.
The foetal heart rate accelerations are a function of foetal heart rate with an important positive prognostic significance and are indicative of positive foetal health and adequate foetal oxygenation. The foetal heart rate accelerations are compared to predetermined criteria.
As mentioned above, foetal heart rate accelerations are identified during the iterative process. Specifically, if the determined foetal heart rate increases above the baseline foetal heart rate by 15 beats per minute or more at an average rate of 5 beats per minute per second or more and remains at least 15 beats per minute or more above the baseline foetal heart rate for at least 15 seconds, the processor 108 determines that a foetal heart rate acceleration has occurred.
At the end of a recording epoch, the processor 108 determines the total number of foetal heart rate accelerations in the epoch
If the processor determines that two or more foetal heart rate accelerations occur in a recording epoch of twenty minutes, the status of the foetal heart rate acceleration parameter is determined to be normal.
If the processor 108 determines the presence of less than two foetal heart rate accelerations in a 20 minute recording epoch, the status of the foetal heart rate acceleration parameter is determined to be cautionary. This is indicative of impending compromises in foetal health.
If the processor 108 determines the presence of less than two foetal heart rate accelerations in a 40 minute recording epoch, the status of the foetal heart rate acceleration parameter is determined to be abnormal. This is indicative of impending, or concurrent, foetal distress.
Similarly, foetal heart rate decelerations are identified during the iterative process discussed above. Specifically, if the determined foetal heart rate decreases below the baseline foetal heart rate by 15 beats per minute or more at an average rate of 5 beats per minute per second or more and remains at least 15 beats per minute or more below the baseline foetal heart rate for at least 15 seconds, the processor 108 determines that a foetal heart rate deceleration has occurred.
At the end of a recording epoch, the processor 108 determines the total number of foetal heart rate decelerations in the epoch, Foetal heart rate decelerations are functions of foetal heart rate with an important negative prognostic significance. Their presence is indicative of severe compromises in foetal health and impending, or concurrent, foetal distress. If the processor 108 determines that no foetal heart rate decelerations occur in a recording epoch of, twenty minutes, the status of the foetal heart rate deceleration parameter is determined to be normal. If the processor 108 determines that one or more foetal heart rate decelerations, each lasting less than 60 seconds in duration, occur in the twenty minute recording epoch, the status of the foetal heart rate deceleration parameter is determined to be cautionary. This is indicative of impending compromises in foetal health. If the processor 108 determines that one or more foetal heart rate decelerations, at least one of which lasts 60 or more seconds in duration, occur in the twenty minute recording epoch, the status of the foetal heart rate deceleration parameter is determined to be abnormal. This is indicative of impending, or concurrent, foetal distress. At the end of each recording epoch, the processor 108 determines the foetal heart rate variability for that epoch.
If the processor 108 determines a foetal heart rate variability in a range from 6-25 beats per minute during a 20 minute recording epoch, the status of the foetal heart rate variability is determined to be normal.
If the processor 108 determines a foetal heart rate variability of less than 6 beats per minute or greater than 25 beats per minute during a 20 minute recording epoch, the status of the foetal heart rate variability is determined to be cautionary. This is indicative of impending compromises in foetal health.
If the processor 108 determines a foetal heart rate variability of less than 6 beats per minute or greater than 25 beats per minute during a 40 minute recording epoch, the status of the foetal heart rate variability is determined to be abnormal. This is indicative of impending, or concurrent, foetal distress.
The processor 108 may be configured to determine that the status of the foetus is normal if the parameters described above satisfy certain clinical guidelines. For example, in one embodiment of the exemplary device, the processor 108 may be configured to determine the status of the foetus according to the Non Stress Test which dictates that if baseline foetal heart rate is within the normal minimum and normal maximum thresholds, two or more accelerations occur within a twenty minute period, no decelerations occur, and foetal heart rate variability is within normal limits the foetus is considered to be healthy. Figure 4 shows a table summarising exemplary values for the parameters for determining whether a status of a parameter is normal, cautionary or abnormal.
As described above, the status of each of the parameters is determined 316 based on the comparison of the parameter to the corresponding predetermined criteria. The determined statuses are used by the processor 108 to generate an output and display it 318 to a user on the display 1 10.
The processor 108 generates a normal output if the status of each of the parameters is determined to be normal. The processor 108 generates a cautionary output if one or more of the statuses of the parameters are determined to be cautionary. The processor 108 generates an abnormal output if the status of each of the parameters is determined to be abnormal or if, following repeated or continuous monitoring within a sixty minute period, a cautionary warning is detected for more than fifty percent of the recordings, i.e. for more than 30 minutes of recording time.
In an exemplary device, the outputs may be displayed to a user in a "traffic light" sequence. That is, a normal output may be displayed as a green indication to a user, a cautionary output may be displayed as an amber indication to a user and an abnormal output may be displayed as a red indication to a user. The traffic light sequence is used throughout the remainder of the document for clarity.
Figure 5 shows a schematic representation of how the processor is configured to determine the status of the output. The status of each of the parameters 500a-d is determined to be one of Normal (N), Cautionary (C) or Abnormal (A). This is shown at references 502a-d. If the status of each parameter 500a-d is normal, the status of the output is normal 504a, which corresponds to a green output. If the status of at least one parameter 500a-d is cautionary, the status of the output is cautionary 504b, which corresponds to an amber output. If the status of all parameters 500a-d are abnormal, the status of the output is abnormal 504c, which corresponds to a red output. In addition to the green, amber and red outputs referred to above, messages and other information may also be displayed to a user as part of the generated output.
Figure 6 shows a screen shot of an exemplary green output. The "green" light 600 of the traffic lights 602 is shown enlarged and this will be coloured green. In addition, the text "your baby is normal" appears on the display. A series of soft keys 604a-g are located along the bottom of the screen and provide additional functionality. In particular, soft key 604a instructs the processor 108 to save the foetal monitoring session data; soft key 604b instructs the processor 108 to email the session data to a designated email account, for example the email account of a medical professional or a family member. The email addresses may already be stored in the device; and soft key 604c instructs the processor 108 to repeat the test.
Other screen shots may be displayed dependent on the output generated by the processor 108. For example, if an amber output is generated, the amber light 606 of the traffic lights 602 will be enlarged and will flash amber. In addition, the message "please repeat the test" may be displayed to the user. If a red output is generated, the red light 608 of the traffic lights 602 is enlarged and flashes red. In addition, the message "Please consult your doctor" is displayed to the user.
As a further example, if the baseline foetal heart rate and/or variability status is determined to be cautionary and there are fewer than two accelerations in a twenty minute period, the user may be instructed to gently prod the baby until they feel it move, then repeat the test. If the situation is the same or worsens on completion of two or more repeat tests, the generated output becomes red.
In addition, the numerical values of the parameters computed, their normal ranges and the final green/amber/red output generated are stored in a memory that can be accessed by the user if required. This may be displayed to the user as a spreadsheet such as shown in Figure 7.
The processor 108 may also be configured to repeat the test automatically if certain conditions exist. For example, if a deceleration is determined during a test, the processor 108 may be configured to repeat the test twice. If a deceleration is again determined then the generated output will become red, or abnormal. Additional information and instruction may be displayed to the user as part generated output.
Figure 8 is a plot of foetal heart rate data against time showing a foetal heart rate acceleration 800, a region of baseline foetal heart rate 802 and a region showing foetal heart rate variability 804.
The apparatuses and methods described herein provide a high degree of accuracy when monitoring foetal health. By contrast, in known hospital based technologies the parameters of the raw sensor data are determined by eye by a skilled operative. Known home based technologies generally provide no output other than an audible heart beat sound and perhaps a trace of foetal heart rate. In addition, the apparatuses and methods disclosed herein may be used easily by expectant mothers and unskilled operators to give a useful assessment of raw data indicative of foetal heart rate.
The skilled person will envisage other embodiments of the invention without departing from the spirit and scope of the appended claims.

Claims

CLAIMS:
1 . A device for monitoring foetal status comprising:
a receiver configured to receive raw sensor data indicative of foetal heart rate;
a processor in electrical communication with the receiver and configured to determine at least one parameter of the raw sensor data,
compare the determined at least one parameter with corresponding predetermined criteria,
determine a status of the at least one parameter based on the comparison and generate an output based on the determined status.
2. A device according to claim 1 , wherein the at least one parameter comprises a plurality of parameters, and wherein the processor is configured to determine a
corresponding plurality of statuses, one for each of the plurality of parameters, and wherein each of the statuses may be one of normal, cautionary and abnormal.
3. A device according to claim 2, wherein the processor is configured to generate a normal output if each of the plurality of statuses is determined to be normal.
4. A device according to claim 2 or 3, wherein the processor is configured to generate a cautionary output if one or more of the plurality of statuses is determined to be cautionary.
5. A device according to any of claims 2 to 4, wherein the processor is configured to generate an abnormal output if each of the plurality of statuses is determined to be abnormal, or if a cautionary output is repeated.
6. A device according to any of claims 2 to 5, wherein the plurality of parameters comprises mean foetal heart rate, and wherein the corresponding predetermined criteria comprise minimum and maximum threshold values.
7. A device according to claim 6, wherein the processor is configured to determine that a mean foetal heart rate status is normal if the determined mean foetal heart rate is in a range from a normal minimum threshold value to a normal maximum threshold value.
8. A device according to claim 7, wherein the normal minimum threshold value is in the range form 105 beats per minute to 1 15 beats per minute and the normal maximum threshold value is in the range from 155 beats per minute to 165 beats per minute.
9. A device according to any of claims 6 to 8, wherein, the processor is configured to determine that the mean foetal heart rate status is cautionary if the mean foetal heart rate is outside the range from the normal minimum threshold value to the normal maximum threshold value and in a range from an abnormal minimum threshold value to an abnormal maximum threshold value.
10. A device according to claim 9, wherein the abnormal minimum is in the range form 95 beats per minute to 105 beats per minute and the abnormal maximum is in the range form 165 beats per minute to 175 beats per minute.
1 1 . A device according to any of claims 6 to 10, wherein, the processor is configured to determine that the mean foetal heart rate status is abnormal if the mean foetal heart rate is less than the abnormal minimum threshold value or greater than the abnormal maximum threshold value.
12. A device according to any of claims 2 to 1 1 , wherein the plurality of parameters comprises foetal heart rate accelerations.
13. A device according to claim 12, wherein the processor is configured to determine that the foetal heart rate accelerations are normal if two or more foetal heart rate accelerations occur in a twenty minute recording epoch and no foetal heart rate
decelerations occur in the twenty minute recording epoch.
14. A device according to claim 12 or 13, wherein the processor is configured to determine that the foetal heart rate acceleration is cautionary if fewer than two foetal heart rate accelerations occur in a twenty minute recording epoch or one or more foetal heart rate decelerations occur in the twenty minute recording epoch.
15. A device according to any of claims 12 to 14, wherein the processor is configured to determine that the foetal heart rate acceleration is abnormal if fewer than two or more foetal heart rate accelerations occur in a twenty minute recording epoch and one or more foetal heart rate decelerations occur in the twenty minute recording epoch.
16. A device according to any of claims 2 to 15, wherein the plurality of parameters comprises foetal heart rate variability.
17. A device according to claim 16, wherein the processor is configured to determine that foetal heart rate variability is normal if fluctuations occur in the range from 6 to 25 beats per minute.
18. A device according to claim 16 or 17, wherein the processor is configured to determine that the foetal heart rate variability is cautionary if fluctuations of less than 6 beats; or more than 25 beats, occur per minute in a 20 minute recording epoch.
19. A device according to any of claims 16 to 18, wherein the processor is configured to determine that the foetal heart rate variability is abnormal if fluctuations of less than 6 beats or more than 25 beats occur per minute in a 40 minute recording.
20. A device according to any of claims 3 to 19, wherein the generated normal output comprises a green indication.
21 . A device according to any of claims 4 to 20, wherein the generated cautionary output comprises an amber indication and an instruction to a user to undertake one or more steps.
22. A device according to any of claims 5 to 21 , wherein the generated abnormal output comprises a red indication and an instruction to a user to undertake one or more steps.
23. A device according to any preceding claim, further comprising a display in electrical communication with the processor and configured to receive the generated output from the processor and display it to a user.
24. A device according to claim 23, wherein the processor is further configured to summarise the output by generating summary data corresponding to a traffic light system and to control the display to display the summary data.
25. A device according to claim 23 or 24, wherein the processor is further configured to provide detailed data corresponding to the value of the determined at least one parameter to control the display to display the detailed data.
26. A device according to any of claims 23 to 25, wherein the processor is further configured to determine instructions to a user based on the determined status of the at least one parameter and to control the display to display the instructions.
27. A device according to any preceding claim, further comprising a transmitter in electrical communication with the processor, wherein the processor is further configured to control the transmitter transmit data based on the at least one determined parameter.
28. A device according to claim 27, wherein transmission of the data is via email.
29. A device according to any preceding claim, wherein the processor is further configured to store the generated output in one of a memory internal to the device, or to a memory located in a cloud computing network.
30. A system comprising a device for monitoring foetal status, the device comprising: a receiver configured to receive raw sensor data indicative of foetal heart rate; a processor in electrical communication with the receiver and configured to determine at least one parameter of the raw sensor data,
compare the determined at least one parameter with corresponding predetermined criteria,
determine a status of the at least one parameter based on the comparison and generate an output based on the determined status,
the system further comprising a sensor assembly configured to obtain the raw sensor data and transmit the foetal heart rate data to the receiver.
31 . A system according to claim 30, wherein the sensor assembly is configured to transmit the foetal heart rate data wirelessly.
32. A computer readable medium comprising computer readable code configured, when read by a computer to control a processor to undertake the steps of:
receiving raw sensor data indicative of foetal heart rate; determining at least one parameters of the raw sensor data;
comparing the determined at least one parameters with corresponding
predetermined criteria;
determining a status of the at least one parameters based on the comparison; and generating an output based on the determined status.
33. A method for monitoring foetal health comprising:
receiving, at a receiver, raw ultrasound sensor data indicative of foetal heart rate; determining, by a processor, at least one parameters of the raw sensor data; comparing, by the processor, the determined at least one parameters with corresponding predetermined criteria;
determining, by the processor, a status of the at least one parameters based on the comparison; and
generating, by the processor, an output based on the determined status.
PCT/GB2013/052195 2012-08-21 2013-08-20 Foetal monitoring WO2014029986A1 (en)

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EP3607878A1 (en) * 2018-08-06 2020-02-12 Koninklijke Philips N.V. Cardiotocographic signals classification

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