Wearable device for fetal physiological condition determination

Abstract

In embodiments of the present disclosure, a device and method for determining the heart rate of a fetus and the heart rate variability of a pregnant woman and fetus is envisaged. The method comprises: generating a spectral transform from a waveform representative of an individual-specific hemodynamic parameter; determining a candidate residual signal included in a region independent of the excluded region of the spectral transformation; identifying candidate residual signals from among the candidate residual signals; comparing the candidate residual signal with a target signal representative of the oxygen level present in the blood flow of the individual, the target signal derived from a hemodynamic parameter; and upon identifying an inverse correlation between the candidate residual signal and a target signal of the individual, determining that the candidate residual signal is associated with a heart rate of a fetus located in the individual.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 424,290, filed on November 10, 2022, entitled “Wearable Devices for Fetus Physiological Condition Determination,” which is hereby incorporated by reference in its entirety. Technical Field

[0002] Embodiments of the present invention relate to a device that may be worn on the wrist or positioned on the chest area of an individual, and various methods and applications associated therewith. Background Art

[0003] This section is intended to introduce various aspects that may be relevant to the embodiments of the present invention described and / or claimed below. This discussion is believed to be helpful in providing background information to facilitate a better understanding of the various aspects of the embodiments of the present invention. Therefore, it should be understood that these statements are to be read in this light and not as admissions of prior art.

[0004] A wide variety of devices have been developed for monitoring patients' physiological characteristics. These devices provide patients, physicians, and other healthcare professionals with the information they need to ensure the best possible healthcare for their patients. As a result, these monitoring devices have become an integral part of modern medicine.

[0005] One technique for monitoring certain physiological characteristics of a patient is commonly referred to as pulse oximetry, and devices built on pulse oximetry technology are commonly referred to as pulse oximeters. Pulse oximetry can be used to measure various blood characteristics, such as arterial oxygen saturation of hemoglobin (SPO2) and the blood pulsation rate corresponding to each heartbeat of the patient. In fact, the "pulse" in pulse oximetry refers to the time-varying amount of arterial blood at the measurement site during each cardiac cycle. Those skilled in the art will recognize that the pulse oximetry technique used to obtain the above-mentioned physiological parameters may also be referred to as photoplethysmography, or PPG for short.

[0006] In the field of medicine, it is also desirable to regularly monitor the physical condition of a pregnant woman and her fetus. In particular, monitoring the physiological parameters of the woman and determining and / or deriving one or more physiological characteristics of the fetus based on these parameters (i.e., hemodynamic parameters) can make it possible to determine any sudden changes in the health of the woman and / or the condition of the fetus. Currently, there are several such devices available, but they are based on Doppler and cardiotocography ("CTG") technology. As such, these devices need to be placed directly on the mother's abdomen for detecting the fetal heart rate. As such, these devices are not capable of real-time monitoring of the health of the mother and the fetus over a long period of time.

[0007] The following patent disclosures of the applicant are hereby incorporated by reference in their entirety: U.S. Patent No. 9,314,197, entitled “Wearable pulse oximetry device,” U.S. Patent Nos. 8,868,149 and 9,149,216, each entitled “Photoplethysmography device and method,” PCT Application No. PCT / IB2017 / 058022, entitled “Wrist-Sensor Pulse Oximetry Device and Method,” and U.S. Patent Application Publication No. 2020 / 0015,723, entitled “Wrist-Sensor Pulse Oximetry Device And Method.” Summary of the Invention

[0008] In embodiments of the present disclosure, devices and methods are contemplated that address and overcome various deficiencies. In particular, devices and methods are contemplated for determining the heart rate of a fetus and the heart rate variability of a pregnant woman and a fetus. The system may include a device that utilizes photoplethysmography ("PPG") optical technology (e.g., a PPG sensor) to determine various physiological parameters of a pregnant woman and utilizes at least one of these parameters to determine a physiological parameter of a fetus carried by the woman. While such a device may be positioned on the wrist of a pregnant woman, it is contemplated that any location on the body from which a pulse can be determined. In embodiments, a device in the form of a chest patch may be placed on the chest area of a pregnant woman and may be used to obtain one or more hemodynamic parameters specific to the woman, which in turn are used to determine, for example, the heart rate of a fetus that she may be carrying.

[0009] In one embodiment, a method for determining at least a physiological parameter specific to a fetus located in an individual includes: generating a spectral transform from a waveform representing a hemodynamic parameter specific to the individual, the spectral transform including multiple harmonics within a sampling period, the multiple harmonics representing the hemodynamic parameter; determining multiple candidate residual signals included in a region included in an exclusion region independent of the spectral transform; identifying a candidate residual signal from the multiple candidate residual signals; comparing the candidate residual signal with a target signal representing an oxygen level present in the individual's blood flow, the target signal being derived from the hemodynamic parameter; and upon identifying an inverse correlation between the candidate residual signal and the target signal for the individual, determining that the candidate residual signal is associated with the heart rate of the fetus located in the individual.

[0010] In another embodiment, an apparatus includes a sensor, at least one light source, a processor, a network communication interface, and a memory. The processor is configured to: generate a spectral transform from a waveform representing a hemodynamic parameter specific to an individual, the spectral transform including a plurality of harmonics within a sampling period, the plurality of harmonics representing the hemodynamic parameter; determine a plurality of candidate residual signals included in a region that is independent of an exclusion region of the spectral transform; identify a candidate residual signal from the plurality of candidate residual signals; compare the candidate residual signal to a target signal representing an oxygen level present in the individual's bloodstream, the target signal being derived from the hemodynamic parameter; and upon identifying an inverse correlation between the candidate residual signal and the target signal for the individual, determine that the candidate residual signal is associated with a heart rate of a fetus located in the individual. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to better understand some embodiments of the present invention and to show how these embodiments may be practiced, reference will now be made by way of example to the accompanying drawings, in which like numerals designate corresponding elements or sections throughout the drawings. In the drawings:

[0012] Figure 1 is a graphic representation of a pulse oximeter;

[0013] Figure 2 is a perspective view of a wrist-wearable device according to an exemplary embodiment of the present invention;

[0014] Figure 3 depicts another embodiment and a perspective view of an example device that may be positioned on the breast of a pregnant woman;

[0015] Figure 4A and Figure 4B Depicting example implementations of applications of example devices of the present disclosure according to one or more embodiments described and illustrated herein;

[0016] Figure 5 depicts two different example graphical representations including individual-specific physiological data;

[0017] Figure 6 depicts three different graphical representations of the results of one or more processing operations performed on sampled hemodynamic waveforms associated with a PPG signal, according to one or more embodiments described and illustrated herein;

[0018] Figure 7 depicts two different graphical representations associated with variability in heart rate of a woman (e.g., a pregnant woman) generated as a result of one or more processing operations performed on sampled hemodynamic waveforms associated with a PPG signal, according to one or more embodiments described and illustrated herein;

[0019] Figure 8 Describes a workflow according to one or more embodiments described and illustrated herein, which workflow illustrates an example implementation of the methods and apparatus of the present disclosure;

[0020] Figure 9 depicts a graphical representation of various harmonic components of a filtered and detrended hemodynamic signal according to one or more embodiments described and illustrated herein;

[0021] Figure 10 depicting a graphical representation of residual signal regions from one or more candidate signals that may be used to potentially determine a fetal heart rate according to one or more embodiments described and illustrated herein; and

[0022] Figure 11 Depicts the presence of a residual signal that may be further analyzed to determine the heart rate of the fetus in accordance with one or more embodiments described and illustrated herein. DETAILED DESCRIPTION

[0023] Now referring to the drawings in detail, it should be understood that the details shown are by way of example and are only for the purpose of illustrative discussion of the preferred embodiments of the present invention. The description taken in conjunction with the drawings will make it clear to those skilled in the art how the present invention can be embodied in practice in several forms and embodiments.

[0024] It should also be understood that the embodiments of the present invention are not limited in their application to the details of construction and arrangement of components set forth in the following description or illustrated in the accompanying drawings. The embodiments of the present invention may be practiced or carried out in various other ways. In addition, it should be understood that the phraseology and terminology employed herein are for descriptive purposes only and should not be construed as limiting.

[0025] Figure 1 A pulse oximeter is shown. In particular, Figure 1A sensor 10 is shown that is adapted to be placed on a finger 12 of a user, such as a patient. Sensor 10 includes a clip formed by two clip portions 14 and 16 that are adapted to clamp and restrain sensor 10 to finger 12 when performing pulse oximetry measurements. Sensors of a type similar to sensor 10 are typically coupled to a cable 18 that couples sensor 10 to a monitoring system adapted to receive and process signals from sensor 10. Consequently, when used in a continuous monitoring mode, such sensors typically require the patient (or user) to be confined to an area in close proximity to the monitoring system, thereby limiting the patient's mobility. Additionally, the pinching pressure exerted by clip portions 14 and 16 on the patient's finger 12 may cause discomfort to the patient over time, requiring the patient to remove sensor 10. As a result, such sensors are not suitable for prolonged and continuous pulse oximetry measurements.

[0026] Figure 2 and Figure 3 The device illustrated in FIG addresses and overcomes various drawbacks.

[0027] Now turning to the accompanying drawings, Figure 2 is a perspective view of a device 200 (e.g., a wrist-wearable device) according to an exemplary embodiment of the present invention. The device 200 may be a wrist-type oximeter device adapted to be worn on a user's wrist, such as Figure 2 As further shown in FIG. In some embodiments, device 200 is adapted to obtain data from a user when the user wears device 200 on their wrist, including, for example, pulse data, oxygen saturation (SPO2) data, and / or other data. Thus, the user can wear device 200 in a manner similar to wearing a watch, wristband, or any other clothing, ornament, or apparel suitable for wearing on the user's wrist. In this manner, the user can wear device 200 while performing any regular and ordinary actions that the user would otherwise perform in daily life, such as walking, running, cycling, and the like. According to embodiments of the present disclosure, device 200 can be conveniently worn by users who need or desire to obtain, for example, pulse oximetry and pulse rate data, at any time or place, without having to be attached to complex monitoring devices or being restricted to certain monitoring areas. Thus, device 200 is a self-contained, self-powered device adapted to obtain, analyze, and process, for example, various optical and electromagnetic signals, ultimately obtaining pulse oximetry data from these optical and electromagnetic signals. Device 200 may also include a wired or wireless interface, whereby device 200 can transmit and / or relay data signals to external and / or remote devices. Thus, in some embodiments, device 200 may collect oximetry data and provide it to any remote user, an institution such as a hospital or clinic, or anyone else who has a need or interest in such pulse oximetry data for a user.

[0028] like Figure 2 , the device 200 may include a display 202 that displays, for example, data measured by the device 200. Such data may include pulse rate data (e.g., “PULSE 76”) and data regarding the oxygen saturation of the wearer's hemoglobin (e.g., “SPO 2 97%"). In some embodiments, the display 202 may be an LED display, such as, for example, an organic light emitting diode ("OLED") display, a liquid crystal display ("LCD"), or any other suitable display. In some embodiments, the device 200 may include one or more physical buttons or user input interfaces (e.g., alphanumeric buttons or user interfaces whereby a user may enter any combination of numbers and / or letters as desired or needed when the device is in use). Alternatively or additionally, in some embodiments, the one or more buttons or user interface inputs may be placed on any one or more sides of the device 200 or at any other area of the device 200 accessible to a user. In some embodiments, the device 200 may alternatively or additionally measure and / or display other data, including, for example, data regarding one or more vital signs, data regarding one or more blood analytes, blood pressure data (e.g., "BP 117 / 76"), and / or data regarding stroke volume (e.g., "SV73").

[0029] Figure 3 A perspective view depicts another embodiment and an example device 300 that can be placed on the chest of an individual (e.g., a pregnant woman). In an embodiment, example device 300 can be a patch worn on the chest area of a woman to monitor various physiological parameters specific to the woman, such as data related to hemodynamic parameters such as heart rate, pulse rate, and blood pressure, which can be obtained in real time. Furthermore, in an embodiment, various body positions of a pregnant woman during pregnancy can be monitored and determined in real time. For example, device 302 and / or device 200 can be used to determine postures such as sitting, standing, and lying down. Furthermore, the precise body positions in which the woman may be lying can also be determined. Data specific to these body postures or positions can be correlated with various hemodynamic parameters (such as heart rate, pulse rate, blood pressure, etc.). This correlation can be used to generate recommendations for specific body positions suitable for the pregnant mother. In an embodiment, these recommendations can be displayed on a display of device 200. In some embodiments, these recommendations can be wirelessly transmitted by example device 300 to, for example, a pregnant woman's smartphone and displayed on the smartphone's display. Other such examples are also contemplated. In an embodiment, data specific to blood pressure, heart rate, pulse rate, etc. may also be transmitted to the pregnant woman's smartphone by the example apparatus 300. The transmitted hemodynamic data may be output on the pregnant woman's smartphone.

[0030] Figure 4AAn example implementation of an application of the example apparatus 300 of the present disclosure is depicted in accordance with one or more embodiments described and illustrated herein. Figure 4A The illustration shows a pregnant woman lying down in a first posture 402, which is not a recommended position. Specifically, first posture 402 makes the pregnant woman appear to be pressing her abdomen against the surface of the mattress, potentially compressing and harming the health of the fetus. Accordingly, device 200 or example device 300 can determine the pregnant woman's position in real time and generate an audio and / or visual alert. In an embodiment, the audio alert may be a beeping sound, notifying the pregnant woman that she is in an unrecommended physical position. In an embodiment, the visual and audio alert may be transmitted to the pregnant woman's smartphone and displayed on the smartphone's screen. For example, as a result of the transmission from example device 300, the visual and audio alert may be output by the pregnant woman's smartphone. In an embodiment, the visual and audio alert may be a text message, such as "Adjust Position," combined with a beeping sound output by example device 300. In an embodiment, the smartphone may also vibrate.

[0031] Figure 4B An example implementation of an application of the example apparatus 300 of the present disclosure is depicted in accordance with one or more embodiments described and illustrated herein. Figure 4B Depicts a second posture 404 or orientation that may be detected by the device 200 or the example device 300. The second posture 404 is a posture that may be determined to be a recommended position because, as illustrated, the pregnant woman appears to have placed a pillow between her legs and is lying on her right side, such that one side of her abdomen appears to be resting on the mattress. Such a position does not appear to place any pressure on the fetus. The example device 300 may generate an audio alert in the form of a sound that is different from the sounds described above, indicating that the current position of the pregnant woman is safe and recommended and should be maintained as such. Similarly, the example device 300 may transmit an audio-visual recommendation that may be output on, for example, a smartphone of the pregnant woman. In an embodiment, the audio-visual recommendation may be a text message such as "Maintain position" or "Maintain current position" that is similar to a text message such as having the same meaning as described above regarding Figure 4A Describes the audio output combination of different beep patterns or frequencies.

[0032] In embodiments, it is noted that while device 200 may be a wrist-wearable device and example device 300 may be a patch wearable on an individual's chest, other designs, shapes, sizes, and configurations of these devices are also contemplated. Furthermore, each of device 200 and device 300 may include at least one light source, at least one sensor, a processor, a memory, a communication interface, and a battery. Furthermore, each device is communicatively coupled to one or more external devices (e.g., a server, a smartphone, a laptop, etc.), and the processor is operable to execute a software application that enables determination of various physiological and hemodynamic parameters used to determine at least the heart rate of the fetus, as well as various physiological conditions of the pregnant woman. In embodiments, each of these devices may also include an accelerometer for enabling determination of the position, movement, or orientation of the individual.

[0033] Figure 5 Depicted are two different example graphical representations that include individual-specific physiological data. The data can be collected using a PPG sensor-based device (e.g., device 200 and / or example device 300). In particular, a first example graphical representation 500 depicts time values on an example x-axis 502 and blood pressure values on an example y-axis 504. In particular, the first example graphical representation 500 depicts a systolic blood pressure curve 506 (indicated in purple) and a diastolic blood pressure curve 508 (indicated in blue) within a particular time range (e.g., a time range ranging from 0 seconds to 1800 seconds). The second example graphical representation depicts time values on an example x-axis 512 and respiratory rate on an example y-axis 514. In particular, respiratory curve 516 (indicated in green) is used to illustrate the variability of respiratory rate in, for example, a pregnant woman.

[0034] Figure 6 Depicted are three different graphical representations of the results of one or more processing operations performed on a sampled hemodynamic waveform associated with a PPG signal, in accordance with one or more embodiments described and illustrated herein. In particular, the third example graphical representation 600 depicts a heart rate curve 602 (indicated in blue), an oxygen level curve 606 (indicated in red), and a fetal heart rate curve 610 (indicated in blue).

[0035] Figure 7Depicted are two different graphical representations associated with the variability of the heart rate of a woman (e.g., a pregnant woman) generated as a result of one or more processing operations performed on a sampled hemodynamic waveform associated with a PPG signal, according to one or more embodiments described and illustrated herein. As illustrated, an example heart rate variability curve 712 ranges from 200 seconds to 1800 seconds, with a minimum value at 1000 seconds and a maximum value at 1800 seconds. Additionally, as illustrated, a general activity curve 706 ranges from 0 seconds to 1800 seconds and shows a sudden spike in activity at approximately the 700-second mark.

[0036] Figure 8 Depicted is a workflow 800 illustrating an example implementation of the methods and apparatus of the present disclosure, according to one or more embodiments described and illustrated herein. Before detailing the steps included as part of workflow 800, an overview of the method steps for determining physiological parameters of a fetus may be instructive.

[0037] The steps for determining physiological parameters of the fetus may be based on processing of measured hemodynamic signals. In particular, the devices 200 and 300 measure hemodynamic signals in the form of pulse waveforms, which are processed to determine blood pressure data, respiratory rate data, heart rate data, cardiac variability data, etc. These signals may be photoplethysmographic (based on PPG signals) or may be based on ultrasound readings or bioimpedance readings. Thereafter, as Figure 6 and Figure 7 As shown in FIG, various physiological parameters may be calculated from the extracted signals as part of one or more processing operations. Such physiological parameters may be calculated in a time dimension or a frequency dimension. In an embodiment, the calculation of physiological parameters based on the signals extracted from the pregnant woman is part of determining one or more signals representing the fetal heart rate. It is noted that the calculation of physiological parameters is associated with a signal of a hemodynamic waveform of a directly sampled PPG nature. The signal may also be of ultrasonic or electrical nature. Furthermore, it is noted that Figure 6 and Figure 7 The signals graphically represented in are the result of processing operations performed on the sampled hemodynamic waveforms of the PPG.

[0038] In operation and during implementation, the signal components corresponding to the first harmonic, the second harmonic, and the third harmonic can be correlated with physiological parameters specific to pregnant women, such as hemodynamic parameters such as heart rate, blood pressure, etc. In addition, specific excluded spectral regions or forbidden zones (in Figures 9 to 11(illustrated in [ 1 ] and described in more detail below). These keep-out zones occur in regions of the spectrum where the signal frequency is less than 1.7 Hz and greater than 4 Hz. In addition, each of the first, second, and third harmonics, and the corresponding thickness ranges for each of these harmonics, are also included in the keep-out zones. In summary, the keep-out zones do not correspond to or include signals that can be used to determine the accurate and final heart rate of the fetus (e.g., residual signals as described below).

[0039] In operation and during implementation, a specific spectral component of the signal (e.g., the residual signal) can be identified and / or selected for use in determining the fetal heart rate, for example, by evaluating whether the spectral component of the signal conforms to or satisfies a set of specific numerical characteristics, i.e., characteristics associated with common physiological parameters of the fetus. Note that the signal is extracted or identified from a spectral region that is independent of the exclusion region. For example, the average level of fetal heart rate variability, the average magnitude of fetal heart rate amplitude variation, etc. can be used as the numerical characteristics that should be met to associate the signal component with the fetal physiological parameter. Note that the comparison process will be described in further detail below.

[0040] Finally, the extracted or determined signal may be validated using at least one of the physiological parameters calculated from the signal specific to the pregnant woman.The method of validation may involve correlating the dynamics of the fetal parameter with at least one physiological parameter of the mother.

[0041] Return to Figure 8 Note that the device 200 worn on the wrist of a pregnant woman or the example device 300 disposed on the chest of the woman may be used to obtain hemodynamic signals such as, for example, a pulse waveform, as shown in the workflow 800 illustrated in FIG. Figure 3 . In an embodiment, the acquired physiological data may be stored in the memory of device 200 and / or the memory of device 300. In an embodiment, the collected data may be transmitted to one or more devices external to device 200, 300 (e.g., one or more servers). In an embodiment, the hemodynamic signal acquired by device 200 or device 300 may take the form of a blood pressure wave, which is unique in that it is a pulsating signal associated with one or more arteries of the heart. In an embodiment, the pulsating signal may be captured within various time periods or sampling windows (e.g., a 30-second sampling window, a 60-second sampling window, etc.) (block 802).

[0042] In embodiments, after capturing hemodynamic data (e.g., represented by a blood pressure wave), one or more signal processing operations may be performed on the captured hemodynamic data. In embodiments, these signal processing operations may be performed manually or automatically and without user intervention. In particular, a low-pass filter may be applied to the acquired hemodynamic data, represented by the blood pressure wave cleaned of high-frequency noise (block 804). As a result, data associated with frequencies above a certain threshold is filtered out from the blood pressure wave, and only those frequencies at or below the threshold are retained. In this manner, application of the low-pass filter removes frequency values corresponding to noise or interference.

[0043] In embodiments, an additional signal processing operation, namely a detrending operation, may be performed on the signal (block 806). In embodiments, the detrending operation corresponds to the application of a function that removes a "best fit line" from the data set (in this case, the detrended blood pressure waveform data represented by the aligned blood pressure waveforms). In embodiments, the use of the detrending operation or function enables the identification of cyclical or other comparable patterns in the waveforms. Furthermore, the detrending operation enables the identification of sudden increases, decreases, or comparable variations in the data set, waveform, etc.

[0044] In an embodiment, after the detrending operation is performed, a spectral transform may be generated manually or automatically and without user intervention (block 812). The generation of the spectral transform enables a graphical representation of the corresponding harmonic components of the detrended signal. Note that the graphical representation of the harmonic components of the detrended signal is shown in FIG. Figures 9 to 11 , and described in more detail below. Furthermore, it is noted that another output of the detrending operation may be a calculation of the oxygen level present in the bloodstream of, for example, a pregnant woman (block 808). It is noted that the oxygen level calculation results may be collected (block 810) and potentially stored in, for example, a memory of the apparatus 200 and / or the example apparatus 300.

[0045] After the spectral transformation is performed, a buffering operation associated with the residual spectrum may be performed (block 816), and the residual spectrum may be compared to a list of criteria. As described above, the residual spectrum may be compared to a list of criteria (e.g., average fetal heart rate variability, average magnitude of fetal heart rate amplitude variation, etc.) (block 818). Thereafter, a buffer may be established for the particular spectral candidate (block 820), and a weighted fetal heart rate value may be determined (block 822). Finally, a fetal-specific heart rate curve may be generated (block 824), and a correlation may be performed between the set of oxygen level calculations associated with the pregnant woman, as determined in block 810, and the heart rate curve generated in step 824. In an embodiment, if there is no anti-correlation (i.e., inverse correlation) between the oxygen level calculations and the fetal HR curve, process flow proceeds to block 802. However, if it is determined that an anti-correlation (i.e., inverse correlation) exists, such that the inverse correlation meets or exceeds a certain threshold, the heart rate curve determined in block 824 may be classified as the accurate and final heart rate curve for the fetus. The above is an overview of workflow 800 , while a more detailed description of at least a subset of steps 812 - 824 is provided below.

[0046] Figure 9 Depicts a graphical representation of various harmonic components of a filtered and detrended hemodynamic signal according to one or more embodiments described and illustrated herein. Figure 9 , the first harmonic 902, second harmonic 904, and third harmonic 906 (above 4 Hz) of the heart rate of a pregnant woman are shown. The first harmonic 902, second harmonic 904, and third harmonic 906, as well as frequencies above 4 Hz and below 1.7 Hz, are identified for elimination purposes, which in turn enables the identification of one or more additional candidate signals corresponding to the heart rate of the fetus.

[0047] In the embodiment, as Figure 8 In the portion of the workflow illustrated in FIG, frequencies corresponding to the first harmonic 902, the second harmonic 904, the third harmonic 906, and frequencies above 4 Hz are manually or automatically identified without user intervention as exclusion regions or "keep-out zones." In other words, the first harmonic 902, the second harmonic 904, the third harmonic 906, and frequencies above 4 Hz and below 1.7 Hz are not included as candidates for the fetal heart rate, or may not be classified as such. Note that the size of the keep-out zone incorporates the width of each of the harmonics and, as such, is slightly larger than the frequencies corresponding to the first harmonic 902, the second harmonic 904, and the third harmonic 906.

[0048] Furthermore, in an embodiment, the forbidden zone includes a frequency range higher than a specific threshold frequency and a frequency range lower than a specific threshold frequency. Figure 10, all frequencies below a frequency corresponding to, for example, less than 1.7 Hz and all frequencies above a frequency corresponding to, for example, 4 Hz are included as part of the forbidden zone. In other words, the signals within these zones may not correspond to the heart rate of the fetus or may not be used to determine the heart rate of the fetus. All frequencies below the first harmonic 902 are indicated by a brown rectangle (representing frequency range 908), and all frequencies above 4 Hz are indicated by a blue rectangle (representing frequency range 910). In summary, the forbidden zone includes a frequency range below the first harmonic 902, a frequency range above 4 Hz, a frequency range below 1.7 Hz, and frequency values corresponding to the first harmonic 902, the second harmonic 904, and the third harmonic 906. As such, any frequency that falls outside the range of the identified forbidden zone may be classified as a candidate signal (e.g., a residual signal) that may be used to determine the heart rate of the fetus. Note that, as described above and in Figure 9 The identification of the keep-out zone illustrated in corresponds to block 814 described above.

[0049] Figure 10 A graphical representation depicting residual signal regions 1000 and 1002 from one or more candidate signals that can be used to potentially determine a fetal heart rate according to one or more embodiments described and illustrated herein. As illustrated, residual signal regions 1000 and 1002 are identified between the first harmonic 902 and the second harmonic 904, and between the second harmonic 904 and the third harmonic 906 (below 4 Hz).

[0050] Figure 11 The present invention depicts a method that can be further analyzed to determine the presence of a residual signal of the fetal heart rate according to one or more embodiments described and illustrated herein. Figure 11 , residual signals 1102, 1104 are illustrated as existing between the first harmonic 902 and the second harmonic 904, and residual signals 1108, 1110 are additional residual signals illustrated as existing between the second harmonic 904 and the third harmonic 906 (when their values are above 1.7 Hz and below 4 Hz).

[0051] As part of identifying residual signals 1102, 1104, 1108, and 1110 that are considered suitable residual signals (i.e., residual signals that can be used to determine the heart rate of the fetus), these residual signals can be observed within a 20-second window. This observation process is the step of buffering the residual spectrum (block 816). At the end of the steps performed in block 816, a specific set of residual signals within the 20-second window are identified as potentially suitable residual signals for determining the heart rate of the fetus. The steps for identifying suitable residual signals are described below.

[0052] In an embodiment, after identifying a set of candidate residual signals within the 20-second window, these candidate residual signals are then checked against a list of criteria, i.e., one or more numerical properties that characterize standard or typical physiological behavior of the fetus (block 818). In an embodiment, the numerical criteria may correspond to specific numerical values representing average variability in heart rate, average variability in the amplitude of heart rate, average change in heart rate, etc. If a candidate residual signal fails to meet one or more of the numerical criteria, the candidate residual signal is filtered out. In other words, these signals are not determined to be suitable signals from which the fetal heart rate can be determined. Conversely, one or more residual signals that do meet the numerical criteria (e.g., associated with average variability in heart rate, average variability in the amplitude of heart rate, and average change in heart rate) are identified as suitable residual signals from which the fetal heart rate can be determined (block 820). After suitable residual signals have been determined, weighting coefficients can be determined for the residual signals.

[0053] In particular, in an embodiment, weighting coefficients may be determined for residual signals 1102, 1104, 1106, and 1108 so that these grouped signals can be combined to determine a single residual signal (block 822). For example, in an embodiment, the weighting coefficients may correspond to a weighted average of residual signals 1102, 1104, 1106, and 1108, which are then applied to these signals to combine them to generate a single signal. For example, residual signals 1102 and 1104 may be combined to generate a single signal, and residual signals 1106 and 1108 may be combined to generate another single signal.

[0054] After calculating the weighting coefficients, the residual signal to which the weighting coefficients are applied may be determined to be a fetal heart rate curve, which may need to be verified (block 824). The results of the verification step enable identification of a final or definitive and accurate fetal heart rate curve (block 828). In an embodiment, as Figure 9 As shown in FIG, it can be determined automatically and without user intervention or manually whether the SPO2 level (e.g., the level of oxygen present in the blood cells of a pregnant woman) as determined in block 810 is inversely correlated with the curve of the residual signal and fetal heart rate as determined in block 824. If an inverse correlation exists, it can be determined that the fetal heart rate curve determined in block 824 is likely to be the final and accurate heart rate of the fetus. In an embodiment, if an inverse correlation is lacking, additional physiological data, i.e., hemodynamic data, can be collected and the above-described and Figures 8 to 11 The steps illustrated in FIG. 8 , namely steps 802 - 824 , are performed to identify the fetal heart rate.

[0055] Item 1: A method for determining at least a physiological parameter specific to a fetus located in an individual, comprising: generating a spectral transform from a waveform representing a hemodynamic parameter specific to the individual, the spectral transform including multiple harmonics within a sampling period, the multiple harmonics representing the hemodynamic parameter; determining multiple candidate residual signals included in a region that is independent of an exclusion region of the spectral transform; identifying a candidate residual signal from the multiple candidate residual signals; comparing the candidate residual signal with a target signal representing an oxygen level present in the individual's blood flow, the target signal being derived from the hemodynamic parameter; and upon identifying an inverse correlation between the candidate residual signal and the target signal for the individual, determining that the candidate residual signal is associated with the heart rate of a fetus located in the individual.

[0056] Clause 2: The method of Clause 1, further comprising obtaining hemodynamic parameters specific to the individual in which the fetus is located using a sensor of a device disposed on the individual.

[0057] Clause 3: The method of clause 1, wherein the individual-specific hemodynamic parameter is the individual's heart rate.

[0058] Clause 4: The method of clause 2, wherein the device is worn on the wrist of the individual.

[0059] Clause 5: The method of clause 2, wherein the device is positioned on the chest of the individual.

[0060] Clause 6: The method of any one of clauses 1 to 5, further comprising performing one or more signal processing operations on the waveform representing the hemodynamic parameter.

[0061] Clause 7: The method of any one of clauses 6, wherein the performing of the one or more signal processing operations comprises: applying a low-pass filter to the waveform representing the hemodynamic parameter; and performing a detrending operation on the waveform representing the hemodynamic parameter.

[0062] Clause 8: The method of any of clauses 1 to 7, wherein identifying the candidate residual signal from the plurality of candidate residual signals comprises combining at least two different candidate target residual signals from the plurality of candidate residual signals within an oversampling period.

[0063] Clause 9: A method according to clause 8, wherein the merging of at least two different candidate target residual signals comprises: determining one or more weighting coefficients specific to the at least two different candidate target residual signals; and applying the one or more weighting coefficients to the at least two different candidate target residual signals for identifying the candidate residual signal.

[0064] Clause 10: The method of clause 9, wherein the one or more weighting coefficients are weighted averages.

[0065] Clause 11: The method of any of clauses 1 to 10, further comprising determining that the candidate residual signal is independent of the heart rate of the fetus when identifying the correlation between the candidate residual signal and the individual target signal.

[0066] Clause 12: The method of any one of clauses 1 to 11, wherein the exclusion zone comprises a plurality of harmonics representative of a hemodynamic parameter of the individual.

[0067] Clause 13: The method of any of clauses 1 to 12, wherein the exclusion zone comprises a first set of frequencies below a threshold frequency value and a second set of frequencies above an additional threshold frequency value.

[0068] Item 14: An apparatus comprising: a sensor; at least one light source; a processor; a network communication interface; and a memory; wherein the processor is configured to: generate a spectral transform from a waveform representing an individual-specific hemodynamic parameter, the spectral transform including multiple harmonics within a sampling period, the multiple harmonics representing the hemodynamic parameter; determine multiple candidate residual signals included in a region that is independent of an exclusion region of the spectral transform; identify a candidate residual signal from the multiple candidate residual signals; compare the candidate residual signal with a target signal representing an oxygen level present in the individual's blood flow, the target signal being derived from the hemodynamic parameter; and upon identifying an inverse correlation between the candidate residual signal and the individual's target signal, determine that the candidate residual signal is associated with the heart rate of a fetus located in the individual.

[0069] Clause 15: The apparatus of clause 14, wherein the processor is further configured to obtain, using the sensor, hemodynamic parameters specific to the individual in which the fetus is located.

[0070] Clause 16: Apparatus according to any of clauses 14 or 15, wherein the individual-specific hemodynamic parameter is the individual's heart rate.

[0071] Clause 17: The device of any of clauses 14 to 16, wherein the device is worn on the wrist of the individual.

[0072] Clause 18: The device of any one of clauses 14 to 17, wherein the device is positioned on the chest of the individual.

[0073] Clause 19: The apparatus of any of clauses 14 to 18, wherein the processor is further configured to perform one or more signal processing operations on the waveform representative of the hemodynamic parameter.

[0074] Clause 20: An apparatus according to any one of clauses 14 to 19, wherein the processor is configured to perform one or more signal processing operations by: applying a low-pass filter to the waveform representing the hemodynamic parameter; and performing a detrending operation on the waveform representing the hemodynamic parameter.

[0075] Clause 21: The apparatus of any of clauses 14 to 20, wherein the processor is configured to identify the candidate residual signal from the plurality of candidate residual signals by combining at least two different candidate target residual signals from the plurality of candidate residual signals within an oversampling period.

[0076] Clause 22: An apparatus according to clause 21, wherein the processor is configured to merge the at least two different candidate target residual signals by: determining one or more weighting coefficients specific to the at least two different candidate target residual signals; and applying the one or more weighting coefficients to the at least two different candidate target residual signals for identifying the candidate residual signal.

[0077] Clause 23: The apparatus of any of clauses 14 to 22, wherein the one or more weighting coefficients are weighted averages.

[0078] Clause 24: The apparatus of any of clauses 14 to 23, wherein the processor is further configured to determine that the candidate residual signal is independent of the heart rate of the fetus when identifying the correlation between the candidate residual signal and the individual target signal.

[0079] Clause 25: The apparatus of any of clauses 14 to 24, wherein the exclusion zone comprises a plurality of harmonics representative of a hemodynamic parameter of the individual.

[0080] Clause 26: Apparatus according to any of clauses 14 to 25, wherein the exclusion zone comprises a first set of frequencies below a threshold frequency value and a second set of frequencies above an additional threshold frequency value.

[0081] Clause 27: The device of any of clauses 14 to 26, wherein the hemodynamic parameter is at least one of the individual's heart rate, the individual's pulse rate, or the individual's blood pressure.

[0082] In the above description, an embodiment is an example or implementation of the present invention. The various appearances of "one embodiment", "an embodiment" or "some embodiments" do not necessarily refer to the same embodiments.

[0083] Although various features of embodiments of the invention may be described in the context of a single embodiment, these features may also be provided separately or in any suitable combination. Conversely, although embodiments of the invention may be described in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment.

[0084] Embodiments of the invention may include features from different embodiments disclosed above, and embodiments may combine elements from other embodiments disclosed above.Disclosure of elements of some embodiments of the invention in the context of specific embodiments should not be considered as limiting their use to only that specific embodiment.

[0085] Furthermore, it is to be understood that embodiments of the invention may be carried out or practiced in various ways and that embodiments of the invention may be implemented in other ways than those outlined in the above description.

[0086] The present invention is not limited to the figures or corresponding descriptions contained herein.For example, in methods according to some embodiments of the present invention, flow need not move through each illustrated step or state in exactly the same order as described.

[0087] Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0088] While this description relates to a limited number of embodiments, these should not be construed as limitations on the scope of the invention, but rather as illustrations of some of the preferred embodiments.Other possible variations, modifications, and applications are also within the scope of the embodiments of the invention.

Claims

1. A method of determining at least a physiological parameter specific to a fetus located in an individual, comprising: generating a spectral transform from a waveform representing a hemodynamic parameter specific to the individual, the spectral transform comprising a plurality of harmonics within a sampling period; determining a plurality of candidate residual signals included in a region independent of an exclusion region of the spectral transform; identifying a candidate residual signal from the plurality of candidate residual signals; comparing the candidate residual signal to a target signal representative of a level of oxygen present in the individual's bloodstream, the target signal being derived from the hemodynamic parameter; as well as In response to identifying an inverse correlation between the candidate residual signal and the target signal of the individual, it is determined that the candidate residual signal is associated with a heart rate of the fetus located in the individual.

2. The method of claim 1, further comprising obtaining the hemodynamic parameters specific to the individual in which the fetus is located using a sensor of a device disposed on the individual.

3. The method according to claim 1 or claim 2, wherein: The hemodynamic parameter specific to the individual is the individual's heart rate.

4. The method according to claim 2 or claim 3, wherein: The device is worn on the individual's wrist.

5. The method according to claim 2 or claim 3, wherein: The device is positioned on the chest of the individual.

6. The method of any one of claims 1 to 5, further comprising performing one or more signal processing operations on the waveform representing the hemodynamic parameter.

7. The method according to claim 6, wherein: Said performing of said one or more signal processing operations comprises: applying a low-pass filter to the waveform representing the hemodynamic parameter; and A detrending operation is performed on the waveform representing the hemodynamic parameter.

8. The method according to any one of claims 1 to 7, wherein The identifying of the candidate residual signal from the plurality of candidate residual signals comprises: At least two different candidate target residual signals from the plurality of candidate residual signals are combined within an oversampling period.

9. The method according to claim 8, wherein The combining of the at least two different candidate target residual signals comprises: determining one or more weighting coefficients specific to the at least two different candidate target residual signals; and The one or more weighting coefficients are applied to the at least two different candidate target residual signals for identifying the candidate residual signal.

10. The method according to claim 9, wherein: The one or more weighting coefficients are a weighted average.

11. The method of any one of claims 1 to 10, further comprising determining that the candidate residual signal is independent of the heart rate of the fetus when identifying the correlation between the candidate residual signal and the target signal of the individual.

12. The method according to any one of claims 1 to 11, wherein The exclusion zone includes the plurality of harmonics representing the hemodynamic parameter of the individual.

13. The method according to any one of claims 1 to 12, wherein The exclusion zone includes a first set of frequencies below a threshold frequency value and a second set of frequencies above an additional threshold frequency value.

14. An apparatus comprising: sensor; at least one light source; processor; Network communication interface; as well as Memory; Wherein, the processor is configured to: generating a spectral transform from a waveform representing an individual-specific hemodynamic parameter, the spectral transform comprising a plurality of harmonics within a sampling period, the plurality of harmonics representing the hemodynamic parameter; determining a plurality of candidate residual signals included in a region independent of an exclusion region of the spectral transform; identifying a candidate residual signal from the plurality of candidate residual signals; comparing the candidate residual signal to a target signal representative of the level of oxygen present in the individual's bloodstream, the target signal being derived from the hemodynamic parameter; and Upon identifying an inverse correlation between the candidate residual signal and the target signal of the individual, it is determined that the candidate residual signal is associated with a heart rate of a fetus located in the individual.

15. The device according to claim 14, wherein The processor is further configured to obtain, using the sensor, the hemodynamic parameters specific to the individual in which the fetus is located.

16. The apparatus of claim 14 or claim 15, wherein: The hemodynamic parameter specific to the individual is the individual's heart rate.

17. The device according to any one of claims 14 to 16, wherein The device is worn on the individual's wrist.

18. The device according to any one of claims 14 to 17, wherein The device is positioned on the chest of the individual.

19. The device according to any one of claims 14 to 18, wherein The processor is further configured to perform one or more signal processing operations on the waveform representing the hemodynamic parameter.

20. The device according to claim 19, wherein The processor is configured to perform the one or more signal processing operations by: applying a low-pass filter to the waveform representing the hemodynamic parameter; and A detrending operation is performed on the waveform representing the hemodynamic parameter.

21. The device according to any one of claims 14 to 20, wherein The processor is configured to identify the candidate residual signal from the plurality of candidate residual signals by: At least two different candidate target residual signals from the plurality of candidate residual signals are combined within an oversampling period.

22. The device according to claim 21, wherein The processor is configured to merge the at least two different candidate target residual signals by: determining one or more weighting coefficients specific to the at least two different candidate target residual signals; as well as The one or more weighting coefficients are applied to the at least two different candidate target residual signals for identifying the candidate residual signal.

23. The device according to any one of claims 14 to 22, wherein The one or more weighting coefficients are a weighted average.

24. The device according to any one of claims 14 to 23, wherein The processor is further configured to determine that the candidate residual signal is independent of the heart rate of the fetus when identifying the correlation between the candidate residual signal and the target signal of the individual.

25. The device according to any one of claims 14 to 24, wherein The exclusion zone includes the plurality of harmonics representing the hemodynamic parameter of the individual.

26. The device according to any one of claims 14 to 25, wherein The exclusion zone includes a first set of frequencies below a threshold frequency value and a second set of frequencies above an additional threshold frequency value.

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