WO2017148881A1 - A method for assessing the reliability of a fetal and maternal heart rate measurement and a mobile device and system for implementing the same - Google Patents

A method for assessing the reliability of a fetal and maternal heart rate measurement and a mobile device and system for implementing the same Download PDF

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Publication number
WO2017148881A1
WO2017148881A1 PCT/EP2017/054545 EP2017054545W WO2017148881A1 WO 2017148881 A1 WO2017148881 A1 WO 2017148881A1 EP 2017054545 W EP2017054545 W EP 2017054545W WO 2017148881 A1 WO2017148881 A1 WO 2017148881A1
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WIPO (PCT)
Prior art keywords
heart rate
maternal
received
signal
fetal
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Application number
PCT/EP2017/054545
Other languages
French (fr)
Inventor
Sujitkumar Sureshrao HIWALE
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Koninklijke Philips N.V.
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Publication of WO2017148881A1 publication Critical patent/WO2017148881A1/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
    • A61B5/02—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
    • A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
    • A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb
    • A61B5/1118—Determining activity level
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6887—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient mounted on external non-worn devices, e.g. non-medical devices
    • A61B5/6898—Portable consumer electronic devices, e.g. music players, telephones, tablet computers
    • 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
    • A61B5/7203—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal
    • A61B5/7207—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal of noise induced by motion artifacts
    • A61B5/721—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal of noise induced by motion artifacts using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
    • 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
    • A61B5/7221—Determining signal validity, reliability or quality

Definitions

  • the invention relates to the field of measurements of fetal heart rate and maternal heart rate and, in particular, relates to a method of assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate and a mobile device and system for implementing the same.
  • fetal Doppler is a commonly used technique for assessing a fetal heart rate since it is simple to use and less technically challenging than other techniques. It is suitable for monitoring fetal heart rate even in low resource settings.
  • fetal Doppler suffers from the disadvantage that maternal heart sounds can be misidentified as fetal heart sounds. The misidentification of fetal heart sounds can have an impact on the reliability of the measurements obtained when monitoring a fetal heart rate.
  • fetal heart rate and maternal heart rate measurement are limited. In other words, it is not possible to determine whether a measurement reflects a true value or whether there are circumstantial factors (such as movement of the mother) that have affected the measurement. To overcome the problem of misidentification or inaccurate measurement of maternal and fetal heart rates, it would be valuable to have a measure of whether a fetal heart rate and maternal heart rate measurement is reliable.
  • a method for assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate comprising: receiving a heart rate signal that is indicative of a fetal heart rate; detecting a maternal heart rate using a detector of a mobile device; receiving an acceleration signal that is indicative of a maternal movement; and determining if the received fetal heart rate and the detected maternal heart rate are reliable based on the received acceleration signal.
  • a measurement of the fetal heart rate and the maternal heart rate is regarded as not being reliable if the measurement indicates that the fetal and maternal heart rates may have been affected by movement of the mother.
  • the method may further comprise: determining if the determined reliability of the received fetal heart rate and the detected maternal heart is above or below a threshold based on the received acceleration signal; if the determined reliability of the received fetal heart rate and the detected maternal heart rate is above the threshold, recording the fetal heart rate and the maternal heart rate; and if the determined reliability of the received fetal heart rate and the detected maternal heart is below the threshold, discontinuing receiving the heart rate signal and discontinuing detecting the maternal heart rate.
  • the method may further comprise notifying an operator of the determined reliability of the received fetal heart rate and the detected maternal heart.
  • the heart rate signal indicative of the fetal heart rate may be a Doppler signal.
  • the method may further comprise analysing a relationship between the detected maternal heart rate and the received accelerometer signal over a period of time to determine a type of maternal tachycardia.
  • the method may further comprise synchronizing the received heart rate signal that is indicative of a fetal heart rate and/or the acceleration signal that is indicative of a maternal movement with the detected maternal heart rate.
  • a computer program product comprising a computer readable medium, the computer readable medium having computer readable code embodied therein, the computer readable code being configured such that, on execution by a suitable computer or processor, the computer or processor is caused to perform any of the methods described above.
  • a system for assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate comprising the mobile device as described herein, a heart rate sensor configured to obtain the heart rate signal that is indicative of the fetal heart rate and an accelerometer sensor configured to obtain the acceleration signal that is indicative of the maternal movement.
  • the mobile device may comprise the accelerometer sensor.
  • the system may comprise a removable strap for placement onto the mother and the removable strap may comprise the accelerometer sensor and/or the heart rate sensor.
  • the system may comprise more than one accelerometer sensor, each accelerometer sensor for placement at a different position on the mother.
  • Figure 3 is a flow chart illustrating a method according to an embodiment of the invention.
  • Figure 5 is a flow chart illustrating a method according to an embodiment of the invention in practice.
  • FIG. 1 shows a block diagram of a mobile device 100 according to an embodiment of the invention that can be used for assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate.
  • the mobile device 100 may be, for example, a portable computing device such as a smartphone, a tablet, or any other portable computing device.
  • the mobile device 100 comprises a receiver 102, a detector 104 and a control unit 106.
  • the mobile device 100 may optionally comprise a memory unit 108 and at least one user interface component 110.
  • the detector 104 of the mobile device 100 is configured to detect a maternal heart rate.
  • the detector 104 can be any type of detector (or sensor) that is able to detect a heart rate of a subject automatically (e.g. without an operator being present with the subject) or manually (e.g. that requires the presence of an operator, such as the subject themselves or a healthcare professional).
  • the detector 104 comprises a camera.
  • the detector 104 comprises a camera and a light (for example, the flash of the camera).
  • the camera and/or light may be internal (i.e. built-in) to the mobile device 100.
  • the mother may place a finger on the detector 104 (e.g. over the camera) of the mobile device 100 in one example.
  • the detector 104 e.g. the camera
  • the detector 104 of the mobile device 100 can then extract a continuous heart rate signal from the pulsatile waves.
  • examples have been given, those skilled in the art will be aware of other types of detectors (or sensors) that can be used to detect the maternal or fetal heart rate.
  • the user interface component 110 of the mobile device 100 is configured to render information resulting from the method according to the invention to the subject or other user of the mobile device 100 (for example, the mother, a family member or a healthcare provider).
  • the user interface component 1 10 of the mobile device 100 may be configured to render the received heart rate signal that is indicative of a fetal heart rate, the detected maternal heart rate and/or the received acceleration signal that is indicative of a maternal movement.
  • the user interface component 110 can comprise any component that is suitable for rendering information resulting from the method according to the invention, and can be, for example, any one or more of a display screen (or other visual indicator), a speaker, one or more lights, a component for providing tactile feedback (e.g. a vibration function) or the like.
  • a device external to the mobile device 100 may render information resulting from the method according to the invention.
  • the mobile device 100 may also comprise the optional memory unit 108 that can be used for storing program code that can be executed by the control unit 106 to perform the method described herein.
  • the memory unit 108 can also be used to store signals
  • the mobile device 100 includes the received heart rate signal, the received acceleration signal, or any other signal
  • measurements made or obtained by any detectors or sensors that are part of the mobile device 100 including the detected maternal heart rate, or any other measurements) or that are external to the mobile device 100
  • any information obtained by the mobile device 100 including the determined reliability or quality for the fetal heart rate and maternal heart rate measurement.
  • FIG. 2 shows a block diagram of a system 200 according to an embodiment of the invention that can be used for assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate.
  • the system 200 comprises a heart rate sensor 202, a detector 204, an accelerometer sensor 206 and a control unit 208.
  • the mobile device 100 comprises the detector 104, 204 and the control unit 106, 208.
  • the heart rate sensor 202 and/or the accelerometer sensor 206 may also be internal to the mobile device 100.
  • the heart rate sensor 202 and/or the accelerometer sensor 206 may be external to the mobile device 100 and connected to an input port of the mobile device 100 via a wired or wireless connection.
  • the system 200 may comprise a removable strap for placement on the mother (for example, for placement on the abdomen of the mother).
  • the removable strap may comprise the heart rate sensor 202 and/or the accelerometer sensor 206, which may be connected to an input port of the mobile device 100 via a wired or wireless connection.
  • the heart rate sensor 202 of the system 200 can be placed on the body of the mother (e.g.
  • the heart rate sensor 202 may obtain a signal that is indicative of the fetal heart rate from a received heart rate signal by analysing the received heart rate signal to distinguish between the fetal heart rate signal and a maternal heart rate signal. This is possible since the fetal heart rate signal has a higher amplitude than the maternal heart rate signal. Thus, the fetal heart rate signal can be obtained from the received heart rate signal by extracting the signal having the higher amplitude. For example, the heart rate sensor 202 may calculate the time interval between the highest amplitude points in the received heart rate signal to obtain the heart rate that is signal indicative of the fetal heart rate.
  • the heart rate sensor 202 may obtain the fetal heart rate by analysing a relationship (or a common pattern) between a received acceleration signal and the maternal heart rate to distinguish the maternal heart rate from the fetal heart rate. This is possible since maternal movements affect a maternal heart rate more prominently than a fetal heart rate (i.e. the fetal heart rate is the signal that is less predominately affected by the maternal movement indicated by the accelerometer signal compared to the maternal heart rate signal).
  • the accelerometer sensor 206 of the system 200 is configured to obtain an acceleration signal that is indicative of a maternal movement. In one embodiment, the acceleration signal is further indicative of maternal uterine contractions.
  • the accelerometer sensor 206 may be placed in a position on the mother's bed, over the mother's chest, over the mother's abdomen or similar.
  • the system 200 may comprise more than one accelerometer sensor, each accelerometer sensor for placement at a different position.
  • the mobile device 100 comprises an accelerometer sensor 206 and the mobile device 100 is placed in a position on the mother's bed, over the mother's chest, over the mother's abdomen or similar.
  • the system 100 may comprise a removable strap for placement onto the mother and the removable strap may comprise an accelerometer sensor 206.
  • the removable strap may also comprise the heart rate sensor 202 and/or a tocodynamometer (toco) transducer, as described earlier.
  • the control unit 106, 208 of the system 200 is configured to determine if the received fetal heart rate and the detected maternal heart rate are reliable based on the received acceleration signal, as described earlier with reference to Figure 1.
  • Figure 3 illustrates a method of assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate according to an embodiment of the invention. This method can generally be performed by the mobile device 100.
  • a heart rate signal that is indicative of a fetal heart rate is received.
  • the receiver 102 of the mobile device 100 receives the heart rate signal indicative of the fetal heart rate from the heart rate sensor 202 of the system 200.
  • the heart rate sensor 202 may be internal to the mobile device 100 or external to the mobile device 100 and connected to an input port of the mobile device via a wired or wireless connection, as discussed earlier.
  • a maternal heart rate is detected using the detector 104, 204 of the mobile device 100.
  • the maternal movements may be classified based on a characteristic of the received acceleration signal.
  • the characteristic may be, for example, a magnitude of the received acceleration signal, a duration of the received acceleration signal, a frequency of the received acceleration signal or any other characteristic or combination of characteristics of the received acceleration signal.
  • the detected maternal heart rate can be used to characterise a source of the maternal movements. For example, movements originating from maternal factors (such as uterine contractions, change in position, or any other maternal factors) proportionally change the maternal heart rate, whereas movements due to external factors (such as maternal bed movement, change in position of sensors, or any other external factors) indirectly change the maternal heart rate or change the maternal heart rate after a delay.
  • maternal factors such as uterine contractions, change in position, or any other maternal factors
  • external factors such as maternal bed movement, change in position of sensors, or any other external factors
  • the received heart rate signal that is indicative of a fetal heart rate and/or the acceleration signal that is indicative of a maternal movement may be synchronized with the detected maternal heart rate.
  • the fetal heart rate signal and the maternal heart rate signal may be captured simultaneously (i.e. the method may comprise receiving a signal that is indicative of a fetal heart rate simultaneously with detecting a maternal heart rate using a detector of a mobile device).
  • the relationship between the received fetal heart rate signal, the detected maternal heart rate signal and/or the acceleration signal can be analysed over a period of time for use in determining the reliability of the received fetal heart rate and the detected maternal heart rate.
  • the relationship between the received fetal heart rate signal, the detected maternal heart rate signal and/or the acceleration signal can be analysed over a period of time to determine a response of the fetal heart rate signal and/or the maternal heart rate signal to the acceleration signal.
  • the control unit 106, 208 of the mobile device 100 determines if the fetal heart rate received at the receiver 102 of the mobile device 100 and maternal heart rate detected at the detector 104 of the mobile device 100 are reliable based on the acceleration signal received at the receiver 102 of the mobile device 100.
  • the control unit 106, 208 determines that the received fetal heart rate and the detected maternal heart are reliable. In other words, the movement of the mother is determined to have a negligible effect on the measurements.
  • the control unit 106, 208 determines that the received fetal heart rate and the detected maternal heart is unreliable. In other words, the movement of the mother is determined to have a significant effect on the measurements.
  • the maternal movements are classified based on a characteristic of the received acceleration signal, it may be determined if the received fetal heart rate and the detected maternal heart rate are reliable based on the classification of the maternal movements. For example, certain classes of movement may be determined to have a less significant effect on the measurements than others.
  • the source of the maternal movements is characterised, it may be determined if the received fetal heart rate and the detected maternal heart rate are reliable based on the characterisation. For example, certain sources of maternal movement may be determined to have a less significant effect on the maternal heart rate than others.
  • the determined reliability of the received fetal heart rate and the detected maternal heart rate may be in the form of a value assigned for the reliability to reflect the extent that external factors (such as movement of the mother) are determined to influence the measurements.
  • the value for the determined reliability will be smaller for acceleration signals close to the maximum value than for signals that are lower (or significantly lower) than the maximum value and, similarly, the value for the determined reliability will be smaller for acceleration signals having a long duration than for signals having a short duration.
  • the smaller the value for the determined reliability the less reliable the measurement and, similarly, the higher the value for the determined reliability, the more reliable measurement.
  • the determined reliability value may be compared to a threshold value to determine whether the measurements are reliable enough to be recorded or whether the measurements are to be discarded (which will be explained in more detail later).
  • the received signal that is indicative of a fetal heart rate may be monitored as a function of the received acceleration signal indicative of the maternal uterine contractions and a health parameter may be determined for the fetus based on the monitored fetal heart rate as a function of the maternal uterine contractions.
  • Figure 4 illustrates a method of assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate according to another embodiment of the invention. This method can generally be performed by the mobile device 100.
  • the method of Figure 4 comprises blocks 400, 402, 404, and 406, which correspond respectively to blocks 300, 302, 304, and 306 of Figure 3, as described earlier.
  • the method of Figure 4 further comprises blocks 408, 410 and 412.
  • the control unit 106, 208 compares the determined reliability with the threshold and makes the determination of whether the received fetal heart rate and the detected maternal heart is above or below the threshold based on the received acceleration signal.
  • the determined reliability of the received fetal heart rate and the detected maternal heart may be determined to be above the threshold if the acceleration signal is equal to or below the maximum value for the acceleration signal or if the acceleration signal is shorter than a set duration (i.e. where the movement of the mother is determined to have an insignificant effect on the measurements).
  • the determined reliability of the received fetal heart rate and the detected maternal heart may be determined to be below the threshold if the acceleration signal is above the maximum value for the acceleration signal or if the acceleration signal is longer than a set duration (i.e. where the movement of the mother is determined to have a significant effect on the measurements).
  • the reliability of the received fetal heart rate may also be determined to be below a threshold if the detected maternal heart rate is above a maximum value. If the detected maternal heart rate is above the maximum value, then it is determined to have an effect on the fetal heart rate along with the fetal movement and breathing patterns. This can lead to an inaccurate assumption that any observed changes are due to pathological conditions in the fetus, in which case, it may not be possible to accurately determine the fetal heart rate due to a large scale change in the maternal heart rate. Thus, if the detected maternal heart rate is above the maximum value for the maternal heart rate, the system 200 may be configured to stop recording measurements (for example, the received fetal heart rate signal and the detected maternal heart rate).
  • the system 200 may indicate to a user that measurement recording is stopped due to apparent non-reliability of the recorded fetal heart rate signal or it may continue to record the signals with an indication to the user that the recorded signals are potentially unreliable, for example, via the user interface component 110 of the mobile device 100 or by some other output device of the system 200 or external to the system 200.
  • the maximum value for the maternal heart rate may be set to a value of 100 bpm or above.
  • the maximum value may be set to a value of lOObpm, HObpm, 120bpm, 130bpm, 140bpm, 150bpm, or any other value above lOObpm.
  • the maximum value may be set based on the age of the mother.
  • the maximum value for the heart rate of a mother under 20 years of age may be set to a value of more than 155 bpm. In this way, based on the various threshold values it is possible to assess the reliability of the received fetal heart rate and the detected maternal heart rate.
  • the method of Figure 4 proceeds to block 410.
  • the received fetal heart rate and the detected maternal heart rate are recorded (or stored).
  • the memory unit 108 of the mobile device 100 records (or stores) the fetal heart rate and the maternal heart rate.
  • the fetal heart rate and the maternal heart rate may be recorded (or stored) in a memory unit external to the mobile device 100.
  • the method of Figure 4 proceeds to block 412.
  • the steps of receiving the fetal heart rate signal and detecting the maternal heart rate are discontinued (or stopped) or based on predetermined settings, the signals may be recorded with an indication to the user that the recorded signals are potentially unreliable. In other words, the recording of the fetal heart rate and the maternal heart rate is stopped.
  • the heart rate sensor 202 discontinues obtaining the heart rate signal indicative of a fetal heart rate and thus the receiver 102 of the mobile device 100 discontinues receiving the fetal heart rate. Also, the detector 104, 204 of the mobile device 100 discontinues detecting the maternal heart rate.
  • the received fetal heart rate is below a threshold for a set time period (which may be set to a value, such as less than 100 bpm, that prevents the received fetal heart rate being confused with the detected maternal heart rate); one of the heart rates is above a threshold and the other heart rate is below another threshold for a set time period;
  • maternal movements persist for longer than a set time period; the magnitude of maternal movements is above a threshold for a set time period;
  • the received fetal heart rate signal and the detected maternal heart rate signal along with maternal movements may be plotted on the same graph and analysed to classify the two signals. For example, an analysis may be based on characteristic parameters such as rate, baseline, variability, acceleration, deceleration, or the like. If the analysis indicates that the characteristic parameters of the two signals are close (for example, where the characteristic parameters differ by less than a threshold value), the result of the analysis may be indicated to the user via the user interface component 110 of the mobile device 100.
  • characteristic parameters such as rate, baseline, variability, acceleration, deceleration, or the like.
  • the analysis may also include an analysis of a relationship between the detected maternal heart rate and the simultaneously received accelerometer signal over a period of time to determine any increase in maternal heart rate (tachycardia) including the type of maternal tachycardia. For example, if the maternal tachycardia is found to be temporary, it may be determined to be the result of maternal physical activity (or
  • a case of maternal tachycardia due to physical activity may be determined where tachycardia is found to be preceded by maternal movements as detected by analysis of the received accelerometer signal.
  • the maternal tachycardia associated with maternal physical activity may appear transient in nature with a sharp peak followed by a gradual decrease in maternal heart rate towards a pre-movement baseline which is within a normal range.
  • the maternal tachycardia is found to persistent, it may be determined to indicate the presence of a systemic pathological condition such as an infection, cardiac problem, respiratory problem, etc.
  • the results of the analysis may be output to a user, for example, via the user interface component 1 10 of the mobile device 100 or by some other output device of the system 200 or external to the system 200.
  • the user may be provided with information regarding the maternal heart rate including whether there is tachycardia or bradycardia detected, whether the tachycardia/bradycardia is temporary or persistent, whether the tachycardia is determined to be associated with physical activity, whether the heart rates are within a normal range prescribed by health guidelines, etc.
  • the recording of maternal and fetal heart rates may be stopped or continued.
  • the results of the analysis may be used to adjust the threshold for the maternal heart rate. For example, the results may be used to adjust the threshold where it is determined that maternal and fetal parameters are disturbed by maternal movements and could lead to difficulty in interpretation of the measurements.
  • the method of Figure 4 may then be repeated.
  • the method of Figure 4 is repeated automatically on expiry of a time period.
  • the time period may be a pre-configured time period or may be a time period set by an operator of the system 200 or the mobile device 100 (such as the subject themselves, a family member or a healthcare professional).
  • the method of Figure 4 is repeated on instruction by an operator of the system 200 or the mobile device 100 (for example, via a user interface component).
  • an operator of the system 200 or the mobile device 100 is notified of the determined reliability of the received fetal heart rate and the detected maternal heart.
  • the notification may be rendered via the user interface component 1 10 of the mobile device 100.
  • the notification may be an audio and/or visual notification.
  • the notification may include one or more lights, an image rendered on a display, tactile stimulation, a sound (such as an alert, alarm, or the like) rendered through a microphone, or the like.
  • Figure 5 illustrates a method of assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate according to another embodiment of the invention in practice.
  • a user logs into a mobile application on the mobile device 100 (which in this example is a mobile phone).
  • the output of the heart rate sensor 202 (which in this example is a fetal Doppler output) is connected to an audio-in port of the mobile device 100.
  • the mobile device 100 is placed on the mother's bed and the mother's finger is placed over the detector 104, 202 (which in this example is a camera) of the mobile device 100.
  • the accelerometer sensor 206 receives an accelerometer signal at block 508 and, at block 510, it is determined whether movement of the mother is detected.
  • the process proceeds to block 512, where the process is paused until movement of the mother is no longer detected. Where no movement of the mother is detected or movement of the mother is no longer detected, the process moves to block 514.
  • the mobile device 100 records the maternal heart rate using the camera.
  • the user begins a fetal heart rate examination using the heart rate sensor 202.
  • a method, mobile device and system for assessing the reliability of a fetal heart rate and a maternal heart rate measurement This can be useful in monitoring a subject at home for antenatal fetal assessment and in hospital for intrapartum fetal monitoring.

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Abstract

There is provided a method for assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate. A heart rate signal that is indicative of a fetal heart rate is received. A maternal heart rate is detected using a detector of a mobile device. An acceleration signal that is indicative of a maternal movement is received. It is determined if the received fetal heart rate and the detected maternal heart rate are reliable based on the received acceleration signal. A corresponding mobile device and system that implements the method is also provided.

Description

A method for assessing the reliability of a fetal and maternal heart rate measurement and a mobile device and system for implementing the same
FIELD OF THE INVENTION
The invention relates to the field of measurements of fetal heart rate and maternal heart rate and, in particular, relates to a method of assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate and a mobile device and system for implementing the same.
BACKGROUND OF THE INVENTION
It has become customary to monitor a fetal heart rate during pregnancy since the information provided through such monitoring is clinically useful in the assessment of fetal we llbeing.
There are many methods and techniques that have been introduced for fetal monitoring. However, existing methods and techniques suffer from a disadvantage that a maternal heart rate may be mistaken or confused with a fetal heart rate and it is difficult to distinguish between the two heart rates, leading to misidentification of the fetal heart rate. For example, fetal Doppler is a commonly used technique for assessing a fetal heart rate since it is simple to use and less technically challenging than other techniques. It is suitable for monitoring fetal heart rate even in low resource settings. However, fetal Doppler suffers from the disadvantage that maternal heart sounds can be misidentified as fetal heart sounds. The misidentification of fetal heart sounds can have an impact on the reliability of the measurements obtained when monitoring a fetal heart rate.
To deal with this, it has been suggested to use simultaneous assessment to sense the maternal pulse rate in order to differentiate it from fetal heart rate recordings.
However, it is not practically possible to palpate maternal pulse rate and perform a fetal heart rate examination simultaneously to detect maternal heart sounds that might interfere with the fetal heart rate measurement. There have also been methods provided (such as that disclosed in US 2014/0330132 Al) in which the maternal heart rate can be removed from combined mother-fetus beats to distinguish heart beats. However, the reliability of the measurements of the fetal heart rate and maternal heart rate is still questionable due to external factors that may influence the measurements. One of the main external factors to have an effect on fetal heart rate and maternal heart rate measurement is movement of the mother during examination. Without knowledge of whether the measurement obtained during examination is reliable (or meets a quality requirement), misidentification or inaccurate measurement of maternal and fetal heart rates remains a problem.
Therefore, there is a need for a way to assess the reliability of a measurement of a fetal heart rate and a maternal heart rate.
SUMMARY OF THE INVENTION
As noted above, a limitation of fetal heart rate and maternal heart rate measurement is that the measurements can be misidentified and/or inaccurate. In other words, it is not possible to determine whether a measurement reflects a true value or whether there are circumstantial factors (such as movement of the mother) that have affected the measurement. To overcome the problem of misidentification or inaccurate measurement of maternal and fetal heart rates, it would be valuable to have a measure of whether a fetal heart rate and maternal heart rate measurement is reliable.
Therefore, according to a first aspect of the invention, there is provided a method for assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate, the method comprising: receiving a heart rate signal that is indicative of a fetal heart rate; detecting a maternal heart rate using a detector of a mobile device; receiving an acceleration signal that is indicative of a maternal movement; and determining if the received fetal heart rate and the detected maternal heart rate are reliable based on the received acceleration signal.
In the context of the present invention, a measurement of the fetal heart rate and the maternal heart rate is regarded as not being reliable if the measurement indicates that the fetal and maternal heart rates may have been affected by movement of the mother.
In some embodiments, the method may further comprise classifying the maternal movements based on a characteristic of the received acceleration signal and the step of determining if the received fetal heart rate and the detected maternal heart rate are reliable may comprise determining if the received fetal heart rate and the detected maternal heart rate are reliable based on the classification of the maternal movements. In some embodiments, the method may further comprise: determining if the determined reliability of the received fetal heart rate and the detected maternal heart is above or below a threshold based on the received acceleration signal; if the determined reliability of the received fetal heart rate and the detected maternal heart rate is above the threshold, recording the fetal heart rate and the maternal heart rate; and if the determined reliability of the received fetal heart rate and the detected maternal heart is below the threshold, discontinuing receiving the heart rate signal and discontinuing detecting the maternal heart rate.
In some embodiments, the method may further comprise notifying an operator of the determined reliability of the received fetal heart rate and the detected maternal heart.
In some embodiments, the heart rate signal indicative of the fetal heart rate may be a Doppler signal.
In some embodiments, the method may further comprise analysing a relationship between the detected maternal heart rate and the received accelerometer signal over a period of time to determine a type of maternal tachycardia.
In some embodiments, the acceleration signal may be further indicative of maternal uterine contractions and the method may further comprise: monitoring the received signal that is indicative of a fetal heart rate as a function of the received acceleration signal indicative of the maternal uterine contractions; and determining a health parameter for the fetus based on the monitored fetal heart rate as a function of the maternal uterine
contractions.
In some embodiments, the method may further comprise synchronizing the received heart rate signal that is indicative of a fetal heart rate and/or the acceleration signal that is indicative of a maternal movement with the detected maternal heart rate.
In some embodiments, the method may further comprise obtaining the fetal heart rate from the received heart rate signal by analysing the received heart rate signal to distinguish between a fetal heart rate signal and a maternal heart rate signal, wherein the fetal heart rate signal has a higher amplitude than the maternal heart rate signal and/or is less predominately affected by the maternal movement indicated by the accelerometer signal compared to the maternal heart rate signal.
According to a second aspect of the invention, there is provided a computer program product comprising a computer readable medium, the computer readable medium having computer readable code embodied therein, the computer readable code being configured such that, on execution by a suitable computer or processor, the computer or processor is caused to perform any of the methods described above.
According to a third aspect of the invention, there is provided a mobile device, comprising: a receiver configured to receive a heart rate signal that is indicative of a fetal heart rate and an acceleration signal that is indicative of a maternal movement; a detector configured to detect a maternal heart rate; a control unit configured to determine if the received fetal heart rate and the detected maternal heart rate are reliable based on the received acceleration signal.
In some embodiments, the detector may comprise a camera.
There is also provided a system for assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate, the system comprising the mobile device as described herein, a heart rate sensor configured to obtain the heart rate signal that is indicative of the fetal heart rate and an accelerometer sensor configured to obtain the acceleration signal that is indicative of the maternal movement.
According to a fourth aspect of the invention, there is provided a system for assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate, the system comprising: a heart rate sensor configured to obtain a heart rate signal that is indicative of a fetal heart rate; a mobile device comprising a detector configured to detect a maternal heart rate; an accelerometer sensor configured to obtain an acceleration signal that is indicative of a maternal movement; and a control unit configured to determine if the received fetal heart rate and the detected maternal heart rate are reliable based on the received acceleration signal.
In some embodiments, the mobile device may comprise the accelerometer sensor.
In some embodiments, the system may comprise a removable strap for placement onto the mother and the removable strap may comprise the accelerometer sensor and/or the heart rate sensor.
In some embodiments, the system may comprise more than one accelerometer sensor, each accelerometer sensor for placement at a different position on the mother.
It is thus possible to determine whether a measurement reflects a true value or whether there are circumstantial factors (such as movement of the mother) that have affected the measurement. In this way, misidentification or inaccurate measurement of maternal and fetal heart rates is prevented. It is also possible to quickly determine a likely cause of any increase in maternal heart rate (tachycardia). BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:
Figure 1 is a block diagram of a mobile device according to an embodiment of the invention;
Figure 2 is a block diagram of a system according to an embodiment of the invention;
Figure 3 is a flow chart illustrating a method according to an embodiment of the invention;
Figure 4 is a flow chart illustrating a method according to another embodiment of the invention; and
Figure 5 is a flow chart illustrating a method according to an embodiment of the invention in practice.
DETAILED DESCRIPTION OF EMBODIMENTS
As noted above, the invention provides a way to determine whether a measurement of a fetal heart rate and a maternal heart rate is reliable, i.e. whether the measurement is a reliable indicator of the fetal and maternal heart rates or whether the measurement has been affected by movement of the mother.
Figure 1 shows a block diagram of a mobile device 100 according to an embodiment of the invention that can be used for assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate. The mobile device 100 may be, for example, a portable computing device such as a smartphone, a tablet, or any other portable computing device. As illustrated in Figure 1, the mobile device 100 comprises a receiver 102, a detector 104 and a control unit 106. The mobile device 100 may optionally comprise a memory unit 108 and at least one user interface component 110.
The receiver 102 of the mobile device 100 is configured to receive a heart rate signal that is indicative of a fetal heart rate. In one embodiment, the heart rate signal is received from a heart rate sensor external to the mobile device 100. In another embodiment, the heart rate signal is received from a heart rate sensor internal to the mobile device 100. The receiver 102 is further configured to receive an acceleration signal that is indicative of a maternal movement. In one embodiment, the acceleration signal is received from an accelerometer sensor external to the mobile device 100. In another embodiment, the acceleration signal is received from an accelerometer sensor internal to the mobile device 100. The received acceleration signal may, according to one embodiment, be further indicative of maternal uterine contractions. For example, the received acceleration signal may be indicative of a frequency, duration and/or strength of the maternal uterine
contractions.
The detector 104 of the mobile device 100 is configured to detect a maternal heart rate. The detector 104 can be any type of detector (or sensor) that is able to detect a heart rate of a subject automatically (e.g. without an operator being present with the subject) or manually (e.g. that requires the presence of an operator, such as the subject themselves or a healthcare professional). In one embodiment, the detector 104 comprises a camera. In another embodiment, the detector 104 comprises a camera and a light (for example, the flash of the camera). The camera and/or light may be internal (i.e. built-in) to the mobile device 100. In order take a reading, the mother may place a finger on the detector 104 (e.g. over the camera) of the mobile device 100 in one example. Using the detector 104 (e.g. the camera) of the mobile device 100, it is possible to detect pulse waves generated by the heart pumping blood through a body via the interlinked system of arteries and arterioles. The detector 104 of the mobile device 100 can then extract a continuous heart rate signal from the pulsatile waves. Although examples have been given, those skilled in the art will be aware of other types of detectors (or sensors) that can be used to detect the maternal or fetal heart rate.
The user interface component 110 of the mobile device 100 is configured to render information resulting from the method according to the invention to the subject or other user of the mobile device 100 (for example, the mother, a family member or a healthcare provider). For example, the user interface component 1 10 of the mobile device 100 may be configured to render the received heart rate signal that is indicative of a fetal heart rate, the detected maternal heart rate and/or the received acceleration signal that is indicative of a maternal movement. The user interface component 110 can comprise any component that is suitable for rendering information resulting from the method according to the invention, and can be, for example, any one or more of a display screen (or other visual indicator), a speaker, one or more lights, a component for providing tactile feedback (e.g. a vibration function) or the like. Alternatively or in addition, a device external to the mobile device 100 may render information resulting from the method according to the invention.
The control unit 106 of the mobile device 100 processes the signals received by the receiver 102 and the signals detected by the detector 104. According to the invention, the control unit 106 is configured to determine if the received fetal heart rate and the detected maternal heart rate are reliable based on the received acceleration signal. The user interface component 1 10 of the mobile device 100 may be configured to provide an indication of whether the heart rate measurements are reliable.
The control unit 106 can comprise one or more processors, processing units, multi-core processors or modules that are configured or programmed to control the mobile device 100 to assess the reliability of a fetal heart rate and a maternal heart rate measurement as described below. In some implementations, the control unit 106 can comprise a plurality of software and/or hardware modules that are each configured to perform, or are for performing, individual or multiple steps of the method according to embodiments of the invention.
The mobile device 100 may also comprise the optional memory unit 108 that can be used for storing program code that can be executed by the control unit 106 to perform the method described herein. The memory unit 108 can also be used to store signals
(including the received heart rate signal, the received acceleration signal, or any other signal), measurements made or obtained by any detectors or sensors that are part of the mobile device 100 (including the detected maternal heart rate, or any other measurements) or that are external to the mobile device 100, and any information obtained by the mobile device 100 (including the determined reliability or quality for the fetal heart rate and maternal heart rate measurement).
Figure 2 shows a block diagram of a system 200 according to an embodiment of the invention that can be used for assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate. As illustrated in Figure 2, the system 200 comprises a heart rate sensor 202, a detector 204, an accelerometer sensor 206 and a control unit 208.
The mobile device 100 comprises the detector 104, 204 and the control unit 106, 208. The heart rate sensor 202 and/or the accelerometer sensor 206 may also be internal to the mobile device 100. Alternatively, the heart rate sensor 202 and/or the accelerometer sensor 206 may be external to the mobile device 100 and connected to an input port of the mobile device 100 via a wired or wireless connection. For example, the system 200 may comprise a removable strap for placement on the mother (for example, for placement on the abdomen of the mother). The removable strap may comprise the heart rate sensor 202 and/or the accelerometer sensor 206, which may be connected to an input port of the mobile device 100 via a wired or wireless connection. The heart rate sensor 202 of the system 200 can be placed on the body of the mother (e.g. against the maternal abdominal surface) to receive a heart rate signal. The heart rate sensor 202 is configured to obtain a heart rate signal that is indicative of a fetal heart rate from the received heart rate signal. In one embodiment, the heart rate sensor 202 is a Doppler transducer configured to obtain a Doppler signal that is indicative of a fetal heart rate (for example, a hand held Doppler transducer configured to acquire fetal heart sounds). In other embodiments, the heart rate sensor 202 is a stethoscope, a microphone, a sensor of the mobile device 100 or any other heart rate sensor configured to obtain a heart rate signal that is indicative of a fetal heart rate.
In one embodiment, the heart rate sensor 202 may obtain a signal that is indicative of the fetal heart rate from a received heart rate signal by analysing the received heart rate signal to distinguish between the fetal heart rate signal and a maternal heart rate signal. This is possible since the fetal heart rate signal has a higher amplitude than the maternal heart rate signal. Thus, the fetal heart rate signal can be obtained from the received heart rate signal by extracting the signal having the higher amplitude. For example, the heart rate sensor 202 may calculate the time interval between the highest amplitude points in the received heart rate signal to obtain the heart rate that is signal indicative of the fetal heart rate. In another embodiment, the heart rate sensor 202 may obtain the fetal heart rate by analysing a relationship (or a common pattern) between a received acceleration signal and the maternal heart rate to distinguish the maternal heart rate from the fetal heart rate. This is possible since maternal movements affect a maternal heart rate more prominently than a fetal heart rate (i.e. the fetal heart rate is the signal that is less predominately affected by the maternal movement indicated by the accelerometer signal compared to the maternal heart rate signal).
The detector 104, 204 of the system 200 is configured to detect a maternal heart rate, as described earlier with reference to Figure 1.
The accelerometer sensor 206 of the system 200 is configured to obtain an acceleration signal that is indicative of a maternal movement. In one embodiment, the acceleration signal is further indicative of maternal uterine contractions. The accelerometer sensor 206 may be placed in a position on the mother's bed, over the mother's chest, over the mother's abdomen or similar. The system 200 may comprise more than one accelerometer sensor, each accelerometer sensor for placement at a different position. In one embodiment, the mobile device 100 comprises an accelerometer sensor 206 and the mobile device 100 is placed in a position on the mother's bed, over the mother's chest, over the mother's abdomen or similar. In another embodiment, the system 100 may comprise a removable strap for placement onto the mother and the removable strap may comprise an accelerometer sensor 206. The removable strap may also comprise the heart rate sensor 202 and/or a tocodynamometer (toco) transducer, as described earlier.
The control unit 106, 208 of the system 200 is configured to determine if the received fetal heart rate and the detected maternal heart rate are reliable based on the received acceleration signal, as described earlier with reference to Figure 1.
Figure 3 illustrates a method of assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate according to an embodiment of the invention. This method can generally be performed by the mobile device 100.
With reference to Figure 3, at block 300, a heart rate signal that is indicative of a fetal heart rate is received. For example, the receiver 102 of the mobile device 100 receives the heart rate signal indicative of the fetal heart rate from the heart rate sensor 202 of the system 200. The heart rate sensor 202 may be internal to the mobile device 100 or external to the mobile device 100 and connected to an input port of the mobile device via a wired or wireless connection, as discussed earlier.
At block 302, a maternal heart rate is detected using the detector 104, 204 of the mobile device 100.
At block 304, an acceleration signal that is indicative of a maternal movement is received. For example, the receiver 102 of the mobile device 100 receives the acceleration signal indicative of the maternal movement from an accelerometer sensor 206 of the system 200. In one embodiment, the acceleration signal may further be indicative of maternal uterine contractions. The accelerometer sensor 206 may be internal to the mobile device 100 or external to the mobile device 100 and connected to an input port of the mobile device via a wired or wireless connection, as discussed earlier.
In one embodiment, the maternal movements may be classified based on a characteristic of the received acceleration signal. The characteristic may be, for example, a magnitude of the received acceleration signal, a duration of the received acceleration signal, a frequency of the received acceleration signal or any other characteristic or combination of characteristics of the received acceleration signal. In some embodiments, the detected maternal heart rate can be used to characterise a source of the maternal movements. For example, movements originating from maternal factors (such as uterine contractions, change in position, or any other maternal factors) proportionally change the maternal heart rate, whereas movements due to external factors (such as maternal bed movement, change in position of sensors, or any other external factors) indirectly change the maternal heart rate or change the maternal heart rate after a delay. Thus, by identifying a relationship between the received acceleration signal and the detected maternal heart rate over a period of time, it is possible to characterise the source of the maternal movements.
Although not shown in Figure 3, after block 304, the received heart rate signal that is indicative of a fetal heart rate and/or the acceleration signal that is indicative of a maternal movement may be synchronized with the detected maternal heart rate.
Alternatively, the fetal heart rate signal and the maternal heart rate signal may be captured simultaneously (i.e. the method may comprise receiving a signal that is indicative of a fetal heart rate simultaneously with detecting a maternal heart rate using a detector of a mobile device). In some embodiments, the relationship between the received fetal heart rate signal, the detected maternal heart rate signal and/or the acceleration signal can be analysed over a period of time for use in determining the reliability of the received fetal heart rate and the detected maternal heart rate. For example, the relationship between the received fetal heart rate signal, the detected maternal heart rate signal and/or the acceleration signal can be analysed over a period of time to determine a response of the fetal heart rate signal and/or the maternal heart rate signal to the acceleration signal.
At block 306, it is determined if the received fetal heart rate and the detected maternal heart rate are reliable based on the received acceleration signal. For example, the control unit 106, 208 of the mobile device 100 determines if the fetal heart rate received at the receiver 102 of the mobile device 100 and maternal heart rate detected at the detector 104 of the mobile device 100 are reliable based on the acceleration signal received at the receiver 102 of the mobile device 100.
In one embodiment, if the received acceleration signal is below a set maximum value and/or the duration of the acceleration signal is within a set time period (i.e. only a short duration movement is detected), the control unit 106, 208 determines that the received fetal heart rate and the detected maternal heart are reliable. In other words, the movement of the mother is determined to have a negligible effect on the measurements. On the other hand, if the received acceleration signal exceeds the set maximum value and/or the duration of the acceleration signal exceeds the set time period, the control unit 106, 208 determines that the received fetal heart rate and the detected maternal heart is unreliable. In other words, the movement of the mother is determined to have a significant effect on the measurements. In the embodiment where the maternal movements are classified based on a characteristic of the received acceleration signal, it may be determined if the received fetal heart rate and the detected maternal heart rate are reliable based on the classification of the maternal movements. For example, certain classes of movement may be determined to have a less significant effect on the measurements than others. Similarly, in embodiments where the source of the maternal movements is characterised, it may be determined if the received fetal heart rate and the detected maternal heart rate are reliable based on the characterisation. For example, certain sources of maternal movement may be determined to have a less significant effect on the maternal heart rate than others.
The determined reliability of the received fetal heart rate and the detected maternal heart rate may be in the form of a value assigned for the reliability to reflect the extent that external factors (such as movement of the mother) are determined to influence the measurements. For example, the value for the determined reliability will be smaller for acceleration signals close to the maximum value than for signals that are lower (or significantly lower) than the maximum value and, similarly, the value for the determined reliability will be smaller for acceleration signals having a long duration than for signals having a short duration. Here, the smaller the value for the determined reliability, the less reliable the measurement and, similarly, the higher the value for the determined reliability, the more reliable measurement. The determined reliability value may be compared to a threshold value to determine whether the measurements are reliable enough to be recorded or whether the measurements are to be discarded (which will be explained in more detail later).
In the embodiment where the acceleration signal is further indicative of maternal uterine contractions, the received signal that is indicative of a fetal heart rate may be monitored as a function of the received acceleration signal indicative of the maternal uterine contractions and a health parameter may be determined for the fetus based on the monitored fetal heart rate as a function of the maternal uterine contractions.
Figure 4 illustrates a method of assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate according to another embodiment of the invention. This method can generally be performed by the mobile device 100.
The method of Figure 4 comprises blocks 400, 402, 404, and 406, which correspond respectively to blocks 300, 302, 304, and 306 of Figure 3, as described earlier. The method of Figure 4 further comprises blocks 408, 410 and 412.
At block 408, it is determined if the determined reliability of the received fetal heart rate and the detected maternal heart is above or below a threshold based on the received acceleration signal. In other words, the control unit 106, 208 compares the determined reliability with the threshold and makes the determination of whether the received fetal heart rate and the detected maternal heart is above or below the threshold based on the received acceleration signal. For example, the determined reliability of the received fetal heart rate and the detected maternal heart may be determined to be above the threshold if the acceleration signal is equal to or below the maximum value for the acceleration signal or if the acceleration signal is shorter than a set duration (i.e. where the movement of the mother is determined to have an insignificant effect on the measurements). On the other hand, the determined reliability of the received fetal heart rate and the detected maternal heart may be determined to be below the threshold if the acceleration signal is above the maximum value for the acceleration signal or if the acceleration signal is longer than a set duration (i.e. where the movement of the mother is determined to have a significant effect on the measurements).
In another embodiment, the reliability of the received fetal heart rate may also be determined to be below a threshold if the detected maternal heart rate is above a maximum value. If the detected maternal heart rate is above the maximum value, then it is determined to have an effect on the fetal heart rate along with the fetal movement and breathing patterns. This can lead to an inaccurate assumption that any observed changes are due to pathological conditions in the fetus, in which case, it may not be possible to accurately determine the fetal heart rate due to a large scale change in the maternal heart rate. Thus, if the detected maternal heart rate is above the maximum value for the maternal heart rate, the system 200 may be configured to stop recording measurements (for example, the received fetal heart rate signal and the detected maternal heart rate). The system 200 may indicate to a user that measurement recording is stopped due to apparent non-reliability of the recorded fetal heart rate signal or it may continue to record the signals with an indication to the user that the recorded signals are potentially unreliable, for example, via the user interface component 110 of the mobile device 100 or by some other output device of the system 200 or external to the system 200.
In one embodiment, the maximum value for the maternal heart rate may be set to a value of 100 bpm or above. For example, the maximum value may be set to a value of lOObpm, HObpm, 120bpm, 130bpm, 140bpm, 150bpm, or any other value above lOObpm. In one embodiment, the maximum value may be set based on the age of the mother. For example, the maximum value for the heart rate of a mother under 20 years of age may be set to a value of more than 155 bpm. In this way, based on the various threshold values it is possible to assess the reliability of the received fetal heart rate and the detected maternal heart rate.
If the determined reliability of the received fetal heart rate and the detected maternal heart rate is above the threshold, the method of Figure 4 proceeds to block 410. At block 410, the received fetal heart rate and the detected maternal heart rate are recorded (or stored). For example, where the control unit 106, 208 determines that the reliability of the received fetal heart rate and the detected maternal heart rate is the threshold, the memory unit 108 of the mobile device 100 records (or stores) the fetal heart rate and the maternal heart rate. Alternatively or in addition, the fetal heart rate and the maternal heart rate may be recorded (or stored) in a memory unit external to the mobile device 100.
On the other hand, if the determined reliability of the received fetal heart rate and the detected maternal heart is below the threshold, the method of Figure 4 proceeds to block 412. At block 412, the steps of receiving the fetal heart rate signal and detecting the maternal heart rate are discontinued (or stopped) or based on predetermined settings, the signals may be recorded with an indication to the user that the recorded signals are potentially unreliable. In other words, the recording of the fetal heart rate and the maternal heart rate is stopped. For example, where the control unit 106, 208 determines that the reliability of the received fetal heart rate and the detected maternal heart rate is below the threshold, the heart rate sensor 202 discontinues obtaining the heart rate signal indicative of a fetal heart rate and thus the receiver 102 of the mobile device 100 discontinues receiving the fetal heart rate. Also, the detector 104, 204 of the mobile device 100 discontinues detecting the maternal heart rate.
In one embodiment, there may be other parameters or events detected that stop the steps of receiving the heart rate signal and detecting the maternal heart rate (i.e. that stop the recording of these measurements). For example, recording of the measurements may be stopped in any one or more of the following situations where:
no fetal heart rate is detected for a set time period;
no maternal heart rate is detected for a set time period;
the maternal heart rate is detected to be above a threshold for a set time period (which may be set to a value, such as 100 bpm, that prevents the detected maternal heart rate being confused with the received fetal heart rate);
the received fetal heart rate is below a threshold for a set time period (which may be set to a value, such as less than 100 bpm, that prevents the received fetal heart rate being confused with the detected maternal heart rate); one of the heart rates is above a threshold and the other heart rate is below another threshold for a set time period;
no heart rates are recorded for a set time period;
maternal movements persist for longer than a set time period; the magnitude of maternal movements is above a threshold for a set time period;
the detected maternal heart rate is above a threshold with the magnitude of maternal movements being above a threshold for a set time period; and/or
or any combination of the above stated conditions or other conditions.
In one embodiment, the received fetal heart rate signal and the detected maternal heart rate signal along with maternal movements may be plotted on the same graph and analysed to classify the two signals. For example, an analysis may be based on characteristic parameters such as rate, baseline, variability, acceleration, deceleration, or the like. If the analysis indicates that the characteristic parameters of the two signals are close (for example, where the characteristic parameters differ by less than a threshold value), the result of the analysis may be indicated to the user via the user interface component 110 of the mobile device 100.
The analysis may also include an analysis of a relationship between the detected maternal heart rate and the simultaneously received accelerometer signal over a period of time to determine any increase in maternal heart rate (tachycardia) including the type of maternal tachycardia. For example, if the maternal tachycardia is found to be temporary, it may be determined to be the result of maternal physical activity (or
movements). In one embodiment, a case of maternal tachycardia due to physical activity may be determined where tachycardia is found to be preceded by maternal movements as detected by analysis of the received accelerometer signal. For example, the maternal tachycardia associated with maternal physical activity may appear transient in nature with a sharp peak followed by a gradual decrease in maternal heart rate towards a pre-movement baseline which is within a normal range. On the other hand, if the maternal tachycardia is found to persistent, it may be determined to indicate the presence of a systemic pathological condition such as an infection, cardiac problem, respiratory problem, etc.
The results of the analysis may be output to a user, for example, via the user interface component 1 10 of the mobile device 100 or by some other output device of the system 200 or external to the system 200. For example, the user may be provided with information regarding the maternal heart rate including whether there is tachycardia or bradycardia detected, whether the tachycardia/bradycardia is temporary or persistent, whether the tachycardia is determined to be associated with physical activity, whether the heart rates are within a normal range prescribed by health guidelines, etc. Based on characteristics of any detected maternal tachycardia by the accelerometer signal, the recording of maternal and fetal heart rates may be stopped or continued.
The analysis may also include a study of the pattern (such as the magnitude, duration, frequency, or the like) of a maternal movement detected by the received
acceleration signal, any change in the detected maternal heart rate (or other parameter such as the maternal blood pressure, or similar) and/or any fetal parameters (such as variability, acceleration, body movements, or the like). The results of the analysis may be used to adjust the threshold for the maternal heart rate. For example, the results may be used to adjust the threshold where it is determined that maternal and fetal parameters are disturbed by maternal movements and could lead to difficulty in interpretation of the measurements.
The method of Figure 4 may then be repeated. In one embodiment, the method of Figure 4 is repeated automatically on expiry of a time period. The time period may be a pre-configured time period or may be a time period set by an operator of the system 200 or the mobile device 100 (such as the subject themselves, a family member or a healthcare professional). In another embodiment, the method of Figure 4 is repeated on instruction by an operator of the system 200 or the mobile device 100 (for example, via a user interface component).
Optionally, an operator of the system 200 or the mobile device 100 (such as the subject themselves, a family member or a healthcare professional) is notified of the determined reliability of the received fetal heart rate and the detected maternal heart. The notification may be rendered via the user interface component 1 10 of the mobile device 100. The notification may be an audio and/or visual notification. For example, the notification may include one or more lights, an image rendered on a display, tactile stimulation, a sound (such as an alert, alarm, or the like) rendered through a microphone, or the like.
Figure 5 illustrates a method of assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate according to another embodiment of the invention in practice.
With reference to Figure 5, at block 500, the process is started. At block 502, a user logs into a mobile application on the mobile device 100 (which in this example is a mobile phone). At block 504, the output of the heart rate sensor 202 (which in this example is a fetal Doppler output) is connected to an audio-in port of the mobile device 100. At block 506, the mobile device 100 is placed on the mother's bed and the mother's finger is placed over the detector 104, 202 (which in this example is a camera) of the mobile device 100. The accelerometer sensor 206 receives an accelerometer signal at block 508 and, at block 510, it is determined whether movement of the mother is detected. If detected movement of the mother is above a certain threshold, the process proceeds to block 512, where the process is paused until movement of the mother is no longer detected. Where no movement of the mother is detected or movement of the mother is no longer detected, the process moves to block 514. At block 514, the mobile device 100 records the maternal heart rate using the camera. At block 516, the user begins a fetal heart rate examination using the heart rate sensor 202. At block 518, it is again determined whether movement of the mother is detected. If movement of the mother is detected, the process proceeds to block 520 and the examination is re-started. On the other hand, if no movement of the mother is detected, the process proceeds to block 522 where the obtained data is saved and the process is ended.
There is therefore provided a method, mobile device and system for assessing the reliability of a fetal heart rate and a maternal heart rate measurement. This can be useful in monitoring a subject at home for antenatal fetal assessment and in hospital for intrapartum fetal monitoring.
Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless
telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:
1. A method for assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate, the method comprising:
receiving (300, 400) a heart rate signal that is indicative of a fetal heart rate; detecting (302, 402) a maternal heart rate using a detector of a mobile device; receiving (304, 404) an acceleration signal that is indicative of a maternal movement; and
determining (306, 406) if the received fetal heart rate and the detected maternal heart rate are reliable based on the received acceleration signal.
2. A method as claimed in claim 1, further comprising:
classifying the maternal movements based on a characteristic of the received acceleration signal; and
wherein determining if the received fetal heart rate and the detected maternal heart rate are reliable comprises determining if the received fetal heart rate and the detected maternal heart rate are reliable based on the classification of the maternal movements.
3. A method as claimed in claim 1 or 2, further comprising:
determining (408) if the determined reliability of the received fetal heart rate and the detected maternal heart is above or below a threshold based on the received acceleration signal;
if the determined reliability of the received fetal heart rate and the detected maternal heart rate is above the threshold, recording (410) the fetal heart rate and the maternal heart rate; and
if the determined reliability of the received fetal heart rate and the detected maternal heart is below the threshold, discontinuing (412) receiving the heart rate signal and discontinuing detecting the maternal heart rate.
4. A method as claimed in any preceding claim, further comprising:
notifying an operator of the determined reliability of the received fetal heart rate and the detected maternal heart.
5. A method as claimed in any preceding claim, further comprising:
analysing a relationship between the detected maternal heart rate and the received accelerometer signal over a period of time to determine a type of maternal tachycardia.
6. A method as claimed in claim 5, wherein the acceleration signal is further indicative of maternal uterine contractions and the method further comprises:
monitoring the received signal that is indicative of a fetal heart rate as a function of the received acceleration signal indicative of the maternal uterine contractions; and
determining a health parameter for the fetus based on the monitored fetal heart rate as a function of the maternal uterine contractions.
7. A method as claimed in any preceding claim, further comprising:
synchronizing the received heart rate signal that is indicative of a fetal heart rate and/or the acceleration signal that is indicative of a maternal movement with the detected maternal heart rate.
8. A method as claimed in any preceding claim, further comprising:
obtaining the fetal heart rate from the received heart rate signal by analysing the received heart rate signal to distinguish between a fetal heart rate signal and a maternal heart rate signal, wherein the fetal heart rate signal has a higher amplitude than the maternal heart rate signal and/or is less predominately affected by the maternal movement indicated by the accelerometer signal compared to the maternal heart rate signal.
9. A computer program product comprising a computer readable medium, the computer readable medium having computer readable code embodied therein, the computer readable code being configured such that, on execution by a suitable computer or processor, the computer or processor is caused to perform the method of any of claims 1-8.
10. A mobile device (100), comprising:
a receiver (102) configured to receive a heart rate signal that is indicative of a fetal heart rate and an acceleration signal that is indicative of a maternal movement;
a detector (104) configured to detect a maternal heart rate;
a control unit (106) configured to determine if the received fetal heart rate and the detected maternal heart rate are reliable based on the received acceleration signal.
11. A mobile device (100) as claimed in claim 10, wherein the detector comprises a camera.
12. A system (200) for assessing the reliability of a measurement of a fetal heart rate and a maternal heart rate, the system comprising:
the mobile device (100) as claimed in any one of claims 10 or 11; a heart rate sensor (202) configured to obtain the heart rate signal that is indicative of the fetal heart rate; and
an accelerometer sensor (206) configured to obtain the acceleration signal that is indicative of the maternal movement.
13. A system (200) as claimed in claim 12, wherein the mobile device comprises the accelerometer sensor (206).
14. A system (200) as claimed in claim 12, wherein the system comprises a removable strap for placement onto the mother and the removable strap comprises the accelerometer sensor (206) and/or the heart rate sensor (202).
15. A system (200) as claimed in any of claims 12 to 14, wherein the system comprises more than one accelerometer sensor (206), each accelerometer sensor for placement at a different position on the mother.
PCT/EP2017/054545 2016-02-29 2017-02-28 A method for assessing the reliability of a fetal and maternal heart rate measurement and a mobile device and system for implementing the same WO2017148881A1 (en)

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