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 women. Fetal heart rate is particularly critical during term or last month of pregnancy and doctors 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 skin. To obtain fetal heart rate, position of fetus needs to be 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 baby moves (which happen often), 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 because of ultrasound piezoelectric crystals. 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 sections. Fetus
shy away from the ultrasound waves making it difficult to position the probe.
Another technique, for fetal heart rate detection uses ECG (Electrocardiogram). 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.
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 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 an acoustic sensor which further gets processed by a processor. The processor then determines the fetal heart rate and gives the required information to an output means. Acoustic Sensors which acquire audio signals of fetal heart sound are cost effective, small, reusable and non-invasive. This 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. When the contraction ends, fetal heart rate should recover to its normal value else the situation demands immediate intervention by doctors. If fetal heart rate is abnormal for certain duration of time, doctors would
typically induce artificial labor or opt for cesarean section. Delay in deciding when the delivery process should be intercepted and when a pregnant woman needs to be shifted to operation theatre can be fatal to fetus and/or mother. Hence during labor doctors 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 doctors to monitor every patient minute by minute. Doctors need a central 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 by the processor. 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.
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. This enables the operator or the patient or the doctor to know any abnormal clinical conditions and call for any help or emergency or perform a clinical procedure. LEDs and speakers could be used for this purpose.
In an alternative embodiment, the alarm device which is an audio device is adapted to indicate fetal heart beats. This enables a doctor for examples, 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 information could be further use for reporting, analysis or remote monitoring. Hence the communication interface (for example, which could be a wired or wireless) enables the transfer of the required signals to the required peripheral devices or location.
In another alternative environment, the acoustic sensor further comprises a holding means to position said acoustic sensor at a location of interest. This helps the operator to conveniently position the sensor at a preferred location using hands. Also an adhesive can be used as a holding means, if the duration of monitoring needs to be long.
In another alternative embodiment, the portable device further comprises a pressure sensor to determine a uterine contraction. Contraction generally starts at the final stage of pregnancy. Clinically, the fetus should regain its normal heart rate with in 15 sec of a uterine contraction. Once this sensor detects end of a contraction, a signal processing algorithm in the processor for calculating the fetal heart rate is activated. This helps in monitoring the fetal heart rate in the final stage of pregnancy.
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. This helps 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 target specialist or operator 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 said alarm associated with the monitoring system alerts the physician or the nurse of an emergency, which can help in timely delivery of clinical help and procedures.
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 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,
FIG 2 illustrates a block diagram of the portable device used for monitoring the fetal heart rate along with an alarm device and a pressure 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 for detection of fetal heart rate information using the portable device,
FIG 5 illustrates a flowchart for detection of fetal heart rate using the acoustic sensor and the pressure sensor, 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 comprises at least one acoustic sensor 110, to capture the fetal heart signal. Acoustic sensor 110 acquires audio signals of fetal heart sound. These sensors are cost effective, waterproof, small size, reusable and non-invasive. The sensors do 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 device 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 acoustic sensor needs signal processing in order to determine heart rate, and processor such as Digital signal processor (DSP)/ Microcontroller/ Field Programmable Gate Arrays (FPGA) can be programmed to implement such signal processing algorithm. The device further comprises an output means 130 for indicating information associated with the determined fetal heart rate. The output means could be a display device. The display device could be an LCD display which can display a numerical value of the heart rate or show a graphical representation of critical information of the fetal heart. The output device can 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 used for monitoring the fetal heart rate along with an alarm means 210 and a pressure sensor 230. The alarm means 210 indicate a status of the fetal heart rate. The alarm means could be a light source or/and an audio device. LED's and speakers can be used for this purpose. A set of different color of LED could be used for indicate or give an alarm related to 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 FHR conditions. The audio alarm device could also be driven by the processor algorithm to indicate fetal heart beats. This enables a doctor 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. This transfers the required signals to the required peripheral devices or location.
The portable device further comprises a pressure sensor 230 to determine a uterine contraction. Conventionally, doctors feel the uterine contractions with their hand and when the contraction ends, they measure the fetal heart rate with a stethoscope. Evidently, it is very strenuous and demands the presence of a doctor 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 a duration of time. Also the efficiency of monitoring relies on expertise of the doctors or nurses.
The pressure sensor 230 enables to realise a continuous monitoring system that can be pasted or positioned on abdomen during the entire process of labor. This type of pressure sensor could be used in hospitals or clinics having plenty of labor rooms for a centralized monitoring. It acquires fetal
heart sound signals from all patients in the labor rooms, which could be captured at a centralized location for monitoring. For example, the Fetal Heart Rates (FHRs) could be displayed at a central location like a nursing station or at the Doctor's room. This can lead to effective supervision of every patient.
In medical science, the time the fetus shall take to regain its normal FHR after a uterine contraction shall not exceed 15 sec. This pressure sensor 230 is used to sense the contractions of pregnant women during labor. Once this sensor detects end of contraction, the signal processing algorithm for the calculation of FHR is activated. With this combination of acoustic sensor 110 to acquire fetal heart sounds and pressure sensor 230 to sense contractions during labor, an FHR monitoring system that is cheap and continuous and that can be used in the labor rooms can be realized.
FIG 3 illustrates a block diagram 300 of a portable device implemented using an embodiment of the invention. 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 complicated audio processing algorithm. In order to enumerate the novel characteristics of the invention, the system functionality must first be described.
The hardware architecture for the fetal heart rate monitor is shown here. Soft processor 304 is responsible for calculating the FHR after pressure 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. When end of contraction is detected by the pressure sensor 230, this module activates signal processing algorithm to calculate FHR. During the next
contraction, FHR calculation is deactivated as no audio signals of fetal heart sound are available during a contraction. When this contraction ends, the control logic 306 will again activate the FHR calculation algorithm. In this way, the FHR monitoring system is continuous in its true sense.
The figure also comprises a hardware controller 308 for an audio codec 310. Instead of an audio codec, we could use an analog-to-digital convertor. This hardware is enabled by the configuration code running in the soft-processor. The system 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 enabled by the configuration code running in the soft-processor 304.
The Soft-processor 304 primarily is used for running the algorithm to process the audio samples from acoustic sensor 110 to find the heart rate. Soft-processor 304 is also used to configure the parameters of audio codec 310 such as sampling frequency. It also configures the communication interface for example; a wireless transmission module 314 to transmit the heart rate after the processing of input audio signal is over. The system is shown comprising a memory module 316 to store information associated to the FHR.
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 pressure sensor along with acoustic audio sensor enables continuous monitoring of fetal heart rate. FPGA 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. Division of functions in hardware and software is critical to get real time resource optimized performance of the system. Since software and hardware are implemented in single FPGA device the interaction between these two important parts of the system can be controlled in better way. The said device could even be realized as portable device similar to that like a PDA, with specialized software to detect the FHR.
The system is based on audio processing algorithm using filtering and autocorrelation. The algorithm requires high precision for input sound and 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. In one of the methods, the fetal heart beat signals are acquired using acoustic sensors at step 402 and are then analyzed as a sequence of audio frames as shown in step 404. 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, dynamic threshold is applied to the filtered signal based on maximum amplitude of the filtered signal. Then energy of the filtered signal is computed for each non-overlapped audio frame at step 410. 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 acoustic sensor and the pressure sensor. At step 502, an end of uterine contraction is determined using a pressure sensor 230. At step 504 the fetal heart rate is determined with the help of the acoustic sensor 110, for example using some techniques as explained in FIG 4. The information related to the FHR is then transmitted to a central monitoring station as shown in step 506.
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 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 or an audio device.
Summarizing, the present invention introduces a portable device for detecting fetal heart rate using 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.
Patent claims:
1. A portable device (100) for detecting fetal heart rate comprising:
- at least one acoustic sensor (110), to capture the fetal heart signal;
- 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 as claimed in claim 1, wherein the acoustic sensor further comprise a holding means to position said acoustic sensor (110) at a location of interest.
10. 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 10;
- 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).
11. The system as claimed in claim 10, wherein the plurality of portable devices (602,604,606,608) further comprises pressure sensors to determine a uterine contraction.
12. The system as claimed in claim 10, wherein the communication channel (610) is wired or wireless.
13. The system as claimed in claim 10, wherein the monitoring station (612) further comprise an alarm means (618) to indicate a status of the fetal heart rate.
14. The system according to claim 10, wherein the monitoring station (612) further comprise a storage means (614) to store information associated with the determined fetal heart rate.

The present invention introduces a portable device (100) for detecting fetal heart rate using an acoustic sensor (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.