WO2011137930A1

WO2011137930A1 - A portable device for fetal heart rate monitoring and a system thereof

Info

Publication number: WO2011137930A1
Application number: PCT/EP2010/056029
Authority: WO
Inventors: Manish Birla; Garimella Padma Madhuri; Thiyagarajan Subramani; Ramasubramanian Viswanathan; Kiran Nagaraj; Zubin Varghese
Original assignee: Siemens AG; Siemens Corp
Current assignee: Siemens AG; Siemens Corp
Priority date: 2010-05-04
Filing date: 2010-05-04
Publication date: 2011-11-10
Anticipated expiration: 2012-11-04

Abstract

The present invention introduces a portable device (100) for detecting fetal heart rate using a detector (110), to capture the fetal heart signal and a processor (120), to determine the fetal heart rate by performing a signal analysis of the captured fetal heart signal. The device also has an output means (130) for indicating information associated with the determined fetal heart rate. Said device could be further used for the centralized monitoring to find the status information of the fetus and the pregnant women in the labor rooms.

Description

A portable device for fetal heart rate monitoring and a system thereof

The present invention relates to health monitoring systems, particularly a fetal heart rate (FHR) monitoring system.

Heart rate of fetus is a highly valuable indicator to assess the health of fetus in a pregnant woman. Fetal heart rate is particularly critical during term or last month of pregnancy and physicians frequently check this rate to detect fetal distress . Current fetal heart rate monitoring systems are

Doppler/Ultrasound based. These devices need gel to match impedance of probe with the skin of the mother. To obtain fetal heart rate, the position of fetus needs to be first located. Hence, gel is applied all over the abdomen of a pregnant woman. Once fetal heart is located, gel is applied again and probe is placed to get the heart beat signal.

During this process, if fetus moves, the process of

positioning probe and acquiring heart beat signal needs to be repeated. This is evidently a cumbersome and inconvenient process. Also, gel hardens after a few minutes adding to discomfort, resulting in replacing the gel quite often.

On the other hand the Doppler/Ultrasound based system is expensive. For long time monitoring the gel need to be replaced often, this will turn out to be expensive at the end. When used for longer times, especially close to the labor these probes or systems need to be strapped to the abdomen which creates unrest and inconvenience for the pregnant women. Exposing fetus to ultrasound continuously is not suggested as it supposedly increases probability of caesarean session. Fetus also shy away from the ultrasound waves making it difficult to position the probe. Another technique for fetal heart rate detection uses ECG (electro-cardiogram) . This also need gel and they require high processing power to determine fetal heart rate from the electric signal received from a pregnant woman' s abdomen resulting in expensive devices for signal processing and further analysis.

It is an object of the present invention to provide an economical and easy to use fetal heart rate monitor.

The said object is achieved by providing a portable device for detecting fetal heart rate according to claim 1 and claim 12 and by a system according to claim 10 for centralized fetal heart rate monitoring utilizing the portable device.

The underlying idea is to capture the fetal heart signal using a detector where said signal further gets processed by a processor. The processor then determines the fetal heart rate and gives the required information to an output means. A detector, preferably an acoustic sensor which acquires audio signals of fetal heart sound is cost effective, small, reusable and non-invasive. Also the use of acoustic sensors does not require the application of the gel for any impedance matching .

Also the use of a single processor makes the whole device small and portable. This further makes the device to be used any time during the period of pregnancy. The said device can also be used for centralized monitoring of fetal heart rates especially in hospitals having multiple labor rooms.

During labor, uterus undergoes contractions frequently almost every minute and during this contraction fetal heart rate drops. After a specific time of an end of uterine

contraction, fetal heart rate should recover to its normal value else the situation demands immediate intervention by a physician. If fetal heart rate is abnormal for certain duration of time, the physician would typically induce artificial labor or go for a cesarean session. Delay in deciding when the delivery process should be intercepted and when a pregnant woman needs to be shifted to an operation theatre can be fatal to the health of fetus and mother. Hence during labor the physician need a continuous monitoring system that checks fetal heart rate ideally every minute to avoid any medical complications to both fetus and mother. Also, in a labor room at a secondary care hospital, there are typically 20-30 patients and it is humanly impossible for a physician to monitor every patient minute by minute.

Physician needs a central monitoring system that shows the status of very patient in the labor room. The device

according to the present invention provides a centralized monitoring system, and helps in avoiding such complications.

In a preferred embodiment, the output means is a display device. This enables the operator of the said device to know the information associated with the determined fetal heart rate. The display could be an LCD display which can provide a numerical value of the heart rate or graphical representation of any critical information of the fetal heart. This helps in easy monitoring and fast analysis. In a further preferred embodiment, the output means is an information storage device. This enables the storage of any information associated with the fetal heart rate for future reference or further analysis. The information storage device can be a volatile or a non volatile memory device.

In an alternative embodiment, the device further comprise an alarm means to indicate a status of the fetal heart rate. The alarm means could be a visual indication by a light source or a sound indication by an audio device. The alarm helps the operator or the patient or the physician to know any abnormal clinical conditions and enable him to call for any help or emergency or provide an indication for the need of a clinical procedure. Light Emitting Diodes (LED) can be used as visual indicators for the alarm and speakers could be used as audio device for providing sound alarm. Other visual or audio indicators known to a person skilled in the art could be used for providing the alarm.

In an alternative embodiment, the alarm device which is an audio device is adapted to indicate fetal heart beats. This enables a physician to hear the real-time heart beat of the fetus.

In another alternative embodiment, the device further

comprise at least one communication interface to transmit information associated with the determined fetal heart rate. The determined fetal heart rate information could be further use for reporting, further analyzing or remote monitoring. Hence the communication interface enables the transfer of the fetal heart rate information to a peripheral device in a local or distributed network which could be in a local or remote location for reporting, further analyzing or remote monitoring as explained above. The communication interface can be a wired or wireless interface.

In another alternative environment, the detector further comprises a holding means to position said acoustic sensor at a location of interest. The holding means which can be a metallic or non metallic holder helps the operator or

physician to conveniently position the detector at a

preferred location using his hands. Also an adhesive can be used as a holding means, if the duration of monitoring is long .

In another alternative embodiment, the portable device further comprises a contraction sensor to determine a uterine contraction. Contraction generally starts at the final stage of pregnancy. Clinically, the fetus should regain its normal heart rate within 15 sec after the end of a uterine contraction. Once this sensor detects end of a contraction, a signal processing algorithm in the processor calculates the fetal heart rate. In a continuous monitoring system the fetal heart rate is continuously monitored. This helps in

monitoring the fetal heart rate in the final stage of

pregnancy. The contraction sensor can be a pressure sensor, rigidity detection sensors, tension detection sensors, vibration sensors, piezoelectric sensor, surface

electomyogram, etc.

In another alternative embodiment, the communication channel to transfer the information associated with the determined fetal heart rate from the plurality of devices to the

monitoring station is wired or wireless. These channels help use of peripheral devices, both wired and wireless to be used accordingly to monitor, store or report the associated information in the fetal heart rate to a specialist or physician sitting in a local or remote location. In another alternative embodiment, the monitoring station further comprise an alarm means to indicate a status of the fetal heart rate. This alarm associated with the monitoring station alerts the physician or the nurse of an emergency, which needs their quick intervention.

In another alternative embodiment, the monitoring station further comprise a storage means to store information

associated with the determined fetal heart rate. The storage associated with the monitoring station could act like a database, where the information received from the plurality of devices are stored for further processing or for future reference .

The present invention is further described hereinafter with reference to illustrated embodiments shown in the

accompanying drawings, in which: FIG 1 illustrates a block diagram of a portable device used for monitoring the fetal heart rate using a detector,

FIG 2 illustrates a block diagram of the portable device used for monitoring the fetal heart rate using an detector along with a contraction sensor,

FIG 3 illustrates a block diagram of the portable device implemented using an FPGA based processor according to an embodiment of the invention,

FIG 4 illustrates a flowchart showing the detection of fetal heart rate according to an embodiment of the invention, FIG 5 illustrates a flowchart showing the detection of fetal heart rate using an detector and a contraction sensor

according to an embodiment of the invention, and

FIG 6 illustrates a system for centralized fetal heart rate monitoring according to an embodiment of the invention.

FIG 1 illustrates a block diagram of a portable device 100 used for monitoring the fetal heart rate. The device 100 comprises at least one detector 110, to capture the fetal heart signal. The preferable detector 110 is an acoustic sensor, for example a microphone. Detector 110 acquires audio signals of fetal heart sound. Acoustic sensors are cost effective, waterproof, small size, reusable and non-invasive. The detector 110 does not employ ultrasound transducers and does not need any ultrasound processing or analyzing

circuitry. Ultrasound probes are big and fragile. The ultra sound probes need to be strapped around a pregnant woman' s abdomen for a good acquisition of the signal if the duration of examination is long. These straps are very uncomfortable and practically, it is not feasible to wear them for long time. On the other hand the acoustic sensors are simple, less complex and convenient to use. The detector 110 can even be realized using a piezoelectric sensor, where the vibrations caused by the fetal heart is captured and converted to electric signals for further analysis and heart rate

detection .

The device 100 also comprises a processor 120, which

determines the fetal heart rate by performing a signal analysis of the captured fetal heart signal. The output of detector 110 needs signal processing in order to determine heart rate. Processor such as Digital Signal Processor (DSP) or Microcontroller or Field Programmable Gate Arrays (FPGA) can be programmed to implement such signal processing

algorithm. The device 100 further comprises an output means 130 for indicating information associated with the determined fetal heart rate. The output means 130 could be a display device. The display device could be a Liquid Crystal Display (LCD) which can display a numerical value of the heart rate or show a graphical representation of critical information of the fetal heart. The output means 130 can also be a storage device, for example a hard disk or a memory stick to store any information associated with the fetal heart rate.

FIG 2 illustrates another embodiment of a portable device 100 used for monitoring the fetal heart rate along with an alarm means 210 and a contraction sensor 230. The alarm means 210 indicate a status of the fetal heart rate. The alarm means

210 in the portable device 100 could be a light source or an audio device or both. LED' s and speakers can be used for this purpose. A set of different colors of LED' s could be used for indicating different fetal heart rate conditions. For example red LED, if the heart rate is abnormal, green LED if the heart rate is normal, etc. The processor algorithm could also be configured to provide specific alarms via the audio device pertaining to specific fetal heart rate conditions. The audio alarm device could also be driven by the processor algorithm to indicate fetal heart beats. This enables a physician for examples, to hear the real-time heart beat of the fetus. The physician can even do this by connecting a pair of earlobes 220 to the device through a communication interface 240. The communication interface 240 could be a wired or wireless enabled. The communication interface 240, transfers the required signals to the required peripheral devices or location.

The portable device 100 further comprises a contraction sensor 230 to determine a uterine contraction.

Conventionally, physician feels the uterine contractions with their hand and when the contraction ends, they measure the fetal heart rate with a stethoscope. Evidently, in a hospital setup it is very strenuous and demands the presence of a physician or nurse for every patient in the labor room. Also, the process of labor can be as long as 6 to 8 hours or sometimes more and it is humanly impossible to continuously monitor for such duration of time. Also the efficiency of monitoring relies on expertise of the physician or nurses.

The contraction sensor 230 helps to realise a continuous monitoring system, where said contraction sensor 230 can be pasted or positioned on abdomen during the entire process of labor. This type of contraction sensors could be used in hospitals or clinics having plenty of labor rooms for

providing a centralized monitoring. It acquires fetal heart signals from all pregnant women in the labor rooms, which could be captured at a centralized location for monitoring. For example, the fetal heart rates could be displayed at a central location like a nursing station or at the physician' s room. This can lead to effective supervision of every

pregnant woman.

The time the foetus shall take to regain its normal heart rate after a uterine contraction shall not generally exceed 15 sec. This contraction sensor 230 is used to sense the contractions of pregnant women during labor.

In one embodiment, once the contraction sensor 230 detects end of contraction, the signal processing algorithm for the calculation of FHR, calculates the FHR and displays the FHR information in the display device. That is the FHR values are shown in the display only after the end of contraction and not during contraction. At the same time the status of the contraction can be displayed in the display device. For example, the status might be an indication whether the contraction is in progress or not.

In another embodiment the fetal heart rate can be

continuously captured and displayed in the display device even before, during and after the contraction to provide continuous monitoring along with the values corresponding to the captured contraction signals. Thus the display device can provide the values associated with the fetal heart rate and the contraction continuously. With this combination of detector 110 to acquire fetal heart signals and contraction sensor 230 to capture contraction signals during labor, an FHR monitoring system that is cheap and continuous can be realized.

FIG 3 illustrates a block diagram of a device 300 accoding to an embodiment herein. This invention uses software hardware combination of modern Field Programmable Gate Arrays (FPGA) 302. The invention proposes the use of soft-processor 304 along with hardware controllers in one single FPGA. This lowers the overall cost of the system. The processing

involves use of audio processing algorithm.

The hardware architecture for the fetal heart rate monitor is shown here. A detector 110 is shown which captures the fetal hear rate signals. Soft-processor 304 is responsible for calculating the FHR after contraction sensor 230 indicates end of contraction. Soft-processor 304 and hardware

controllers are implemented on single FPGA device. The architecture comprises of control logic 306, which is a hardware module that acts like a control switch. In one embodiment, the control logic 306 can be made to remain active all through the process cycle. When end of contraction is detected by the contraction sensor 230, the control logic 306 activates signal processing algorithm to calculate FHR. During the next contraction, FHR calculation is deactivated. When this contraction ends, the control logic 306 will again activate the FHR calculation algorithm. The processed

information, which can be a value associated with FHR and any information associated with contraction signals can be shown to the physician using suitable output means. The physician can monitor the values of the FHR and any information on contraction to find if the FHR has reached a normal range with in 15 seconds of the end of the contraction.

In yet another embodiment the FHR calculation algorithm remains active although the device operation cycle, making the FHR monitoring system continuous in its true sense. In this embodiment the control logic 306 can be made to go into a passive mode, allowing continuous capture and processing of FHR signals and contraction signals. Finally any output means can be used to display the information resulting from a processed FHR and contract signals.

The figure also comprises a hardware controller 308 for an audio codec 310, which can encode analog audio signals to digital. Instead of an audio codec, an analog-to-digital convertor can be used. These hardwares are operationally enabled by the configuration code running in the soft- processor. The device 300 also comprises a First-In-First-Out logic module 309 to process the acquired signals. The

architecture also comprises a hardware controller 312 for connecting any communication interface or device. The shown design interfaces a software enabled wireless transmission module 314. This hardware could be operationally enabled by the configuration code running in the soft-processor 304.

For example if the detector 110 used is an acoustic sensor, then the soft-processor 304 primarily is used for running the algorithm to process the audio signals to find the heart rate. Soft-processor 304 is also used to configure the parameters of audio codec 310 such as sampling frequency. The soft-processor 304 also configures the communication

interface for example; a wireless transmission module 314 to transmit the FHR information after the processing of input audio signal is over. The device 300 is shown comprising a memory module 316 to store information associated with the FHR.

Detectors 110, especially acoustic sensors are cost effective and easy to use. They give sufficient information for the purpose of monitoring the fetal heart rate. A signal

processing module implemented in the FPGA does the

calculations for fetal heart rate. Use of contraction sensor along with detector enables continuous monitoring of fetal heart rate. FPGA 302 has also the advantage of easy

configurability and do have the parallel processing capacity along with the advantage of handling all the required

processing in a single chip, making the device cheap, small and portable. Since software and hardware are implemented in single FPGA 302, the interaction between these two important parts of the device 300 can be controlled in better way. The device 300 could be realized as a portable device similar to that of a personal digital assistant (PDA) .

The device 300 uses audio processing algorithm for the captured FHR signals, which might need further filtering and autocorrelation. The algorithm takes care of high precision requirement of input sound and also adjustments and selection of required filter coefficients. The basic functionality of the algorithm implemented is depicted in the flowchart 400 given in FIG 4. The device could use any of the existing signal processing algorithms, for the determination of the fetal heart rate. At step 402, the fetal heart beat signals are acquired using detectors and at step 404 the signals are analyzed as a sequence of audio frames. At step 406 a low pass filter with cut off frequency suitable to fetal heart sound is applied on each audio frame. At step 408, a dynamic threshold is applied to the filtered signal based on maximum amplitude of the filtered signal. At step 410, the energy of the filtered signal is computed for each non-overlapped audio frame. At step 412 an auto correlation function of each audio frame is computed for different time lags. Then the duration of the heart cycle is calculated at step 414 from the auto correlation function. From this the fetal heart rate is determined and displayed in a display means at step 416.

FIG 5 illustrates a flowchart 500 for the detection of fetal heart rate using the detector and the contraction sensor. At step 502, an end of uterine contraction is determined using a contraction sensor. At step 504 the fetal heart rate is determined with the help of the detector, for example using techniques as explained in FIG 4. At step 506, the

information related to the FHR is then transmitted to a central monitoring station.

FIG 6 illustrates a system 600 for centralized fetal heart rate monitoring according to an embodiment of the invention. The scheme shows a wireless networked continuous monitoring system for labor rooms in a clinic or in a hospital. Each patient uses a portable device for measuring the fetal heart rate. The portable device 602, 604, 606, 608 are connected to pregnant women in the labor rooms. The figure shows these multiple devices connected through wireless link 610 to a central display unit 612. Central display unit 612 can also store history of FHR readings for each device in a memory storage 614 and display their statistical variations in the display unit 616. The monitoring station further comprises an alarm means 618 to indicate a status of the fetal heart rate. The alarm means could be a light source, for example an LED or an audio device, for example a speaker. Summarizing, the present invention introduces a portable device for detecting fetal heart rate using a detector preferably an acoustic sensor, to capture the fetal heart signal and a processor, to determine the fetal heart rate by performing a signal analysis of the captured fetal heart signal. The device also has an output means for indicating information associated with the determined fetal heart rate. Said device could be further used for the centralized

monitoring to find the status information of the fetus and the patient in the labor room.

Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present invention as defined.

Claims

Patent claims:

1. A portable device (100) for detecting fetal heart rate comprising :

- at least one detector (110) to capture the fetal heart signal, where the signal is captured non-invasively;

- a processor (120), said processor determining the fetal heart rate by performing a signal analysis of the captured fetal heart signal; and

- an output means (130) for indicating an information

associated with the determined fetal heart rate.

2. The device according to claim 1, wherein the output means (130) is a display device.

3. The device according to claim 1, wherein the output means (130) is an information storage device.

4. The device according to claim 1, further comprise an alarm means (210) to indicate a status of the fetal heart rate.

5. The device according to claim 4, wherein the alarm means (210) is a visual indication by a light source.

6. The device according to claim 4, wherein the alarm means (210) is a sound indication by an audio device.

7. The device according to claim 6, wherein the audio device is adapted to indicate fetal heart beats.

8. The device according to claim 1, further comprise at least one communication interface (240) to transmit information associated with the determined fetal heart rate.

9. The device according to claim 1, wherein the detector (110) further comprise a holding means to position said detector (110) at a location of interest.

10. The device as claimed in claim 1, wherein the detector (110) is an acoustic sensor.

11. The device as claimed in claim 1, wherein the detector (110) is a piezoelectric sensor.

12. A portable device (100) for continuous monitoring of heart rate of a fetus, comprising:

-at least one contraction sensor (230), adapted to capture a contraction signal of a uterus,

- at least one detector (110), adapted to capture a fetal heart signal of a fetus;

- a processor (120) configured to determine the heart rate of the fetus by performing a signal analysis on the captured fetal heart signal and the contraction signal; and

- an output means (130) for indicating an information

associated with the determined heart rate of the fetus and the contraction, Where, the contraction signal and the fetal heart signal are captured non-invasively .

13. The device as claimed in claim 12, wherein the detector (110) is an acoustic sensor.

14. The device as claimed in claim 12, wherein the detector (110) is a piezoelectric sensor.

15. The device according to claim 12, further comprise an alarm means (210) to indicate a status of the heart rate the fetus .

16. A system (600) for centralized fetal heart rate monitoring comprising:

- a plurality of portable devices (602, 604, 606, 608), said portable device as claimed in any of the claims 1 to 11;

- a monitoring station (612), said monitoring station (612) adapted to receive the information associated with the determined fetal heart rates from the plurality of devices (602, 604, 606, 608); and

- a communication channel (610) to transfer the information associated with the determined fetal heart rate from the plurality of devices (602, 604, 606, 608) to the monitoring station ( 612 ) .

17. The system according to claim 16, wherein the plurality of portable devices (602, 604, 606, 608) further comprises contraction sensors (230) to determine a uterine contraction.

18. The system according to claim 17, wherein the monitoring station (612) is adapted to receive information associated with uterine contractions from the plurality of devices (602, 604, 606, 608) .

19. The system according to claim 17, wherein the

communications channel (610) is a wired or wireless channel.

20. The system according to claim 17, wherein the monitoring station (612) further comprise an alarm means (618) to indicate a status of the fetal heart rate.

21. The system according to claim 17, wherein the monitoring station (612) further comprise a storage means (614) to store information associated with the determined fetal heart rate.