Systems and methods for performing transabdominal fetal oximetry or transabdominal fetal pulse oximetry

Abstract

Systems, devices, and methods for performing transabdominal fetal oximetry and / or transabdominal fetal pulse oximetry using physiological characteristics and / or calibration factors are adapted to receive physiological characteristics of a pregnant mammal and determine one or more potential influences of the physiological characteristics on the behavior of an optical signal projected into the abdomen of the pregnant mammal. A calibration factor for the optical signal is then determined in response to the influences. The calibration factor is then used to calibrate the fetal-detected electronic signal to determine a level of fetal hemoglobin oxygen saturation.

Description

[Technical Field]

[0001] (Related Applications) This application is based on U.S. Provisional Patent Application No. 62 / 878,243, filed July 24, 2019, entitled "SYSTEMS, DEVICES, AND METHODS FOR PERFORMING TRANS-ABDOMINAL FETAL OXIMETRY AND / OR TRANS-ABDOMINAL FETAL PULSE OXIMETRY USING PHYSIOLOGICAL CHARACTERISTICS AND / OR A CALIBRATION FACTOR" and entitled "SYSTEMS, DEVICES, AND METHODS FOR PERFORMING FETAL OXIMETRY AND / OR FETAL PULSE OXIMETRY USING FETAL DEPTH AND / OR A MATERNAL HEMOGLOBIN OXYGEN SATURATION LEVEL." This is an international PCT application of U.S. Provisional Patent Application No. 62 / 971,152, filed February 6, 2020, entitled "HEMOGLOBIN OXYGEN SATURATION LEVEL," all of which are hereby incorporated in their entireties herein.

[0002] The present invention is in the field of medical devices, and more particularly in the field of transabdominal fetal oximetry and transabdominal fetal pulse oximetry. [Background technology]

[0003] Oximetry is a method for determining the oxygen saturation of hemoglobin in mammalian blood. Typically, in adult humans, 90% (or more) of hemoglobin is saturated with oxygen (i.e., bound to oxygen), whereas fetal blood is only 30%-60% saturated with oxygen. Pulse oximetry is a form of oximetry that uses changes in blood volume throughout the cardiac cycle to internally calibrate hemoglobin oxygen saturation measurements in arterial blood.

[0004] Current methods of monitoring fetal health, such as monitoring fetal heart rate, are ineffective in determining the level of fetal distress and often produce false positive results suggesting fetal distress, which can lead to unnecessary cesarean section deliveries. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Provisional Patent Application No. 62 / 878,243 [Patent Document 2] U.S. Provisional Patent Application No. 62 / 971,152 Summary of the Invention

[0006] Described herein are systems, devices, and methods for performing transabdominal fetal oximetry and / or transabdominal fetal pulse oximetry using physiological characteristics and / or calibration factors. In some embodiments, a physiological characteristic of a pregnant mammal may be received, for example, by a computer or processor. The impact of the physiological characteristic on the behavior of an optical signal projected into the abdomen of the pregnant mammal may then be determined. Exemplary impact factors include absorption and scattering of the optical signal. A calibration factor for the optical signal may then be determined in response to the determined impact of the physiological characteristic. In some cases, determining the calibration factor may include querying a database for a corresponding calibration factor using the physiological characteristic. The determined calibration factor may then be stored in the database.

[0007] In some cases, the processor may be further configured to receive a composite detected electronic signal from a detector communicatively coupled to the processor. The composite detected electronic signal may correspond to an optical signal emitted from the abdomen of the pregnant mammal and the fetus contained therein, detected by the detector, and converted into the composite detected electronic signal. The emitted optical signal represents a portion of the light projected into the abdomen of the pregnant mammal and onto the fetus contained therein. The fetal signal may then be generated by isolating the portion of the composite detected electronic signal corresponding to the light incident on the fetus. Isolation of the fetal signal from the composite signal (maternal and fetal signals) can be achieved in numerous ways, including, but not limited to, filtering via a bandpass filter or a Kalman filter, amplification, and / or processing using one or more input signals, such as fetal heart rate, maternal heart rate, maternal pulse oxygen saturation value, and / or maternal respiration value, to remove the portion of the composite signal contributed by the pregnant mammal and / or amplify the portion of the composite signal contributed by the fetus. Some of these techniques could also be used to remove noise (e.g., ambient light, harmonics, etc.) from the composite signal and / or the fetal signal. The calibration coefficients are then applied to the fetal signal to generate a calibrated fetal signal, which is processed to determine a fetal hemoglobin oxygen saturation level for the fetus. The fetal hemoglobin oxygen saturation level may then be communicated to a user, such as a doctor, midwife, or nurse.

[0008] In some embodiments, an indication of whether the fetal signal corresponds to pre-ductal or post-ductal blood may be received by the processor. Typically, this indication is entered by a clinician based on the location of the detector on the pregnant mammal's abdomen capturing the composite signal, which corresponds to the location on the fetus from which the composite signal originated (e.g., head, chest, or limbs). This indication may later be provided or displayed to a user along with the fetal hemoglobin oxygen saturation level, allowing the user to determine whether the fetal hemoglobin oxygen saturation level is dangerously low for the fetus.

[0009] In some embodiments, the maternal detected electronic signal may be received from a detector communicatively coupled to the processor. The maternal detected electronic signal may correspond to an optical signal emitted from the abdomen of the pregnant mammal (that did not travel deep enough into the abdomen to reach the fetus), detected by the detector, and converted into the maternal detected electronic signal. In some embodiments, the maternal detected electronic signal may be a short separation signal that passes only through maternal tissue. The emitted optical signal represents a portion of the light projected into the abdomen of the pregnant mammal by the light source. The maternal detected electronic signal may then be analyzed to determine a physiological characteristic of the pregnant mammal. The determined physiological characteristic and / or calibration coefficient for the pregnant mammal may be stored in a database.

[0010] The received physiological characteristics may be intrinsic or extrinsic, for example, the age of the pregnant mammal, the weight of the pregnant mammal, and the body mass index of the pregnant mammal. Sometimes the physiological characteristics are received from a clinician based on the clinician's observations, or based on an ultrasound device, a Doppler device, an image of the pregnant mammal's abdomen, a Fitzpatrick scale reading, a manually operated caliper, a blood measurement device, an oximeter, a pulse oximeter, and / or a scale.

[0011] In one embodiment, the received physiological characteristic is skin pigment or melanin concentration of the pregnant mammal, and determining the influence of the physiological characteristic on the behavior of the optical signal may include determining how much of the optical signal is absorbed by melanin / skin pigment of the pregnant mammal.

[0012] Additionally or alternatively, the received physiological characteristic may be a thickness of the abdominal muscle layer of the pregnant mammal, in which case determining the influence of the physiological characteristic on the behavior of the optical signal may include determining how much of the optical signal is absorbed by the abdominal muscle layer of the pregnant mammal.

[0013] Additionally or alternatively, the received physiological characteristic is the thickness of the adipose layer in the abdomen of the pregnant mammal, and in that case, determining the influence of the physiological characteristic on the behavior of the optical signal includes determining how much of the optical signal is scattered by the adipose layer in the abdomen of the pregnant mammal.

[0014] Additionally or alternatively, the received physiological characteristic may be a body mass index of the pregnant mammal, and determining the influence of the physiological characteristic on the behavior of the optical signal may include determining how much of the optical signal is scattered or absorbed by the pregnant mammal's abdomen due to her body mass index.

[0015] Additionally or alternatively, the received physiological characteristic may be abdominal thickness (also referred to herein as fetal depth) of the pregnant mammal, in which case determining the influence of the physiological characteristic on the behavior of the optical signal may include determining how much of the optical signal is absorbed by the abdomen / abdominal tissue of the pregnant mammal.

[0016] Additionally or alternatively, the received physiological characteristic may be an abdominal thickness of the pregnant mammal, and determining the influence of the physiological characteristic on the behavior of the optical signal may include determining how much of the optical signal is scattered by the abdomen of the pregnant mammal.

[0017] Additionally or alternatively, the received physiological characteristic may include a hemoglobin concentration in the blood of the pregnant mammal, and in these circumstances, determining the influence of the physiological characteristic on the behavior of the optical signal may include determining how much of the optical signal is absorbed by hemoglobin in the pregnant mammal.

[0018] Additionally or alternatively, the received physiological characteristic may be hemoglobin oxygen saturation of the blood of the pregnant mammal, and determining the influence of the physiological characteristic on the behavior of the optical signal may include determining how much of the optical signal is absorbed by oxygenated hemoglobin and / or deoxygenated hemoglobin of the pregnant mammal.

[0019] In another embodiment, the maternal detected electronic signal may be received from a detector communicatively coupled to the processor, and the maternal detected electronic signal may correspond to an optical signal emitted from the abdomen of the pregnant mammal, detected by the detector, and converted into the maternal detected electronic signal. The emitted optical signal represents a portion of light projected (by the light source) into the abdomen of the pregnant mammal. The maternal detected electronic signal may then be analyzed to determine a physiological characteristic of the pregnant mammal. In response to the analysis, a calibration factor for the optical signal emitted from the pregnant mammal may be determined. In some embodiments, the physiological characteristic of the pregnant mammal may be associated with the calibration factor, and this association may be stored in a database.

[0020] In some cases, the composite detected electronic signal may be received from a detector communicatively coupled to the processor. The composite detected electronic signal may correspond to an optical signal emitted from the abdomen of the pregnant mammal and the fetus contained therein, detected by the detector, and converted into the composite detected electronic signal. The emitted optical signal represents a portion of light projected by the light source into the abdomen of the pregnant mammal and onto the fetus contained therein. The fetal signal may then be generated by isolating the portion of the composite detected electronic signal corresponding to the light incident on the fetus. A calibration factor may be applied to the fetal signal to generate a calibrated fetal signal. The calibrated fetal signal may then be used to determine a fetal hemoglobin oxygen saturation level, and the fetal hemoglobin oxygen saturation level may be communicated to a user, for example, via displaying the fetal hemoglobin oxygen saturation on a display.

[0021] In some embodiments, determining a calibration factor for the optical signal in response to the influence may include querying a database for a calibration factor corresponding to the physiological characteristic and receiving the queried calibration factor from the database.

[0022] In some cases, an indication of whether the fetal signal corresponds to pre-ductal or post-ductal blood may be received, for example, from a clinician or physician, and this indication may be provided to the user along with the fetal hemoglobin oxygen saturation level.

[0023] In some cases, the maternal detected electronic signal may be received from a detector communicatively coupled to the processor. The maternal detected electronic signal may correspond to an optical signal emanating from the abdomen of the pregnant mammal that is detected by the detector and converted into a maternal detected electronic signal, i.e., that did not pass through or impinge on the fetus. As such, it is an optical signal that only passes through the maternal abdomen but does not penetrate deep enough into the abdomen to impinge on the fetus. The maternal detected electronic signal may then be analyzed and / or processed, and a physiological characteristic of the pregnant mammal may be determined in response to the analysis.

[0024] In some cases, the physiological property determined is a skin pigment of the pregnant mammal, and the calibration factor may be related to how much of the optical signal is absorbed by the skin pigment of the pregnant mammal. Additionally or alternatively, the physiological property determined is a thickness of the abdominal muscle layer of the pregnant mammal, and the calibration factor may be related to how much of the optical signal is absorbed by the abdominal muscle layer of the pregnant mammal.

[0025] Additionally or alternatively, the determined physiological property may be a thickness of the adipose layer of the abdomen of the pregnant mammal, and the calibration factor may be related to how much of the optical signal is scattered by the adipose layer of the abdomen of the pregnant mammal. Additionally or alternatively, the determined physiological property may be a thickness of the abdomen of the pregnant mammal, and the calibration factor may be related to how much of the optical signal is absorbed by the abdomen of the pregnant mammal. Additionally or alternatively, the determined physiological property may be a thickness of the abdomen of the pregnant mammal, and the calibration factor may be related to how much of the optical signal is scattered by the abdomen of the pregnant mammal. Additionally or alternatively, the determined physiological property may be a hemoglobin concentration in the blood of the pregnant mammal, and the calibration factor may be related to how much of the optical signal is absorbed by the hemoglobin of the pregnant mammal. Additionally or alternatively, the physiological characteristic determined may be hemoglobin oxygen saturation of the pregnant mammal's blood, and the calibration factor may relate to how much of the optical signal is absorbed by oxygenated and deoxygenated hemoglobin of the pregnant mammal. [Brief explanation of the drawings]

[0026] [Figure 1A] FIG. 1 is a block diagram illustrating an exemplary system for determining oxygen saturation levels for fetal hemoglobin and / or determining whether meconium is present in the amniotic fluid of a pregnant mammal, consistent with some embodiments of the present invention. [Figure 1B] FIG. 1 is a block diagram of an exemplary processor-based system capable of storing data and / or executing instructions for the processes disclosed herein, consistent with some embodiments of the present invention. [Figure 2A] 1 is a block diagram illustrating an exemplary fetal probe consistent with certain embodiments of the present invention. [Figure 2B] FIG. 10 is a block diagram illustrating another exemplary fetal probe, consistent with certain embodiments of the present invention. [Figure 3A]1 provides an illustration of exemplary dimensions for tissue layers within two different maternal abdomens containing individual fetuses, consistent with certain embodiments of the present invention. [Figure 3B] 1 provides an illustration of exemplary dimensions for tissue layers within two different maternal abdomens containing individual fetuses, consistent with certain embodiments of the present invention. [Figure 3C] 1 provides a midsagittal plan view of the abdomen of a pregnant mammal with a fetal hemoglobin probe positioned thereon, consistent with certain embodiments of the present invention. [Figure 4A] 1 depicts an exemplary fetal hemoglobin probe in contact with the abdomen of a pregnant mammal, showing the different layers of maternal abdominal tissue, consistent with certain embodiments of the present invention. [Figure 4B] 10 depicts another exemplary fetal hemoglobin probe in contact with the abdomen of a pregnant mammal, consistent with certain embodiments of the present invention. [Figure 4C] 1 depicts an exemplary fetal hemoglobin probe configured to contact the abdomen of a pregnant mammal and detect two short-range separated signals and one long-range separated signal, consistent with some embodiments of the present invention, with the layers of the maternal abdomen depicted as a single layer. [Figure 4D] 1 illustrates an exemplary fetal hemoglobin probe configured to contact the abdomen of a pregnant mammal and detect two short-range separated signals and one long-range separated signal, consistent with some embodiments of the present invention, with some of the layers of the maternal abdomen shown. [Figure 5] 1 provides a flowchart illustrating a process for determining fetal hemoglobin oxygen saturation levels, consistent with certain embodiments of the present invention. [Figure 6] 1 is a flowchart illustrating a process for determining physiological characteristics of a pregnant mammal using received optical signals, consistent with some embodiments of the present invention. [Figure 7A]1 is a flowchart illustrating an example process for determining fetal depth and / or fetal hemoglobin oxygen saturation level, according to some embodiments of the present invention. [Figure 7B] 10 is a flowchart illustrating an example process for determining fetal depth, according to some embodiments of the present invention. [Figure 7C] 10 provides a graph illustrating a scatter plot of the change in percent light transmission for 1-N fetal signals as a function of source-detector distance, according to some embodiments of the present invention. [Figure 7D] 1 provides a graph illustrating a scatter plot of the change in percent light transmission for maternal signals 1-N as a function of source-detector distance, according to some embodiments of the present invention. [Figure 8] 1 is a flowchart illustrating an example process for determining fetal depth and / or fetal hemoglobin oxygen saturation level, according to some embodiments of the present invention. [Figure 9] 1 is a flowchart illustrating an example process for determining fetal depth and / or fetal hemoglobin oxygen saturation level, according to some embodiments of the present invention. [Figure 10] 1 is a flowchart illustrating a process for determining fetal hemoglobin oxygen saturation levels using physiological characteristics of a pregnant mammal determined using one or more maternal detected electronic signals, according to some embodiments of the present invention. [Figure 11] 11 is a flowchart illustrating a process 1100 for determining the influence of physiological characteristics on the behavior of light traversing through the abdomen of a pregnant mammal and / or her fetus, according to some embodiments of the present invention. [Figure 12] 10 is a flowchart illustrating an example process for determining fetal hemoglobin oxygen saturation level using maternal hemoglobin oxygen saturation level and / or fetal depth, according to some embodiments of the present invention. [Figure 13]1 provides a flowchart illustrating a process for determining fetal hemoglobin oxygen saturation levels using calibration factors and / or physiological characteristics of a pregnant mammal, consistent with certain embodiments of the present invention. [Figure 14] 1 provides a flowchart illustrating a process for determining fetal hemoglobin oxygen saturation levels, consistent with certain embodiments of the present invention. [Figure 15A] 1 provides a flowchart illustrating a first part of a process for determining a composite fetal hemoglobin oxygen saturation level, consistent with certain embodiments of the present invention. [Figure 15B] 10 provides a flowchart illustrating a second part of a process for determining a composite fetal hemoglobin oxygen saturation level, consistent with certain embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] The behavior of light projected into the abdomen of a pregnant mammal can be affected (e.g., absorbed and / or scattered) by the abdominal tissues of the pregnant mammal. This can affect how much of the light incident on the maternal abdomen is incident on the fetus within the abdomen of the pregnant mammal, and / or can affect the clarity of the signal received from the maternal abdomen and / or the signal incident on the fetus. Knowing how much light is incident on the fetus is important for a variety of reasons. For example, values for the intensity of light incident on the fetus and / or the percent transmission of light through the abdomen of the pregnant mammal could be used in oximetry calculations and / or to calculate fetal hemoglobin oxygen saturation using the Beer-Lambert law. Additionally, the behavior (absorption and / or scattering) of light projected into the abdomen of a pregnant mammal, which are referred to herein as absorption coefficients, i.e., (μ a (λ)) and / or the scattering coefficient (μ sUnderstanding of λ, sometimes referred to as (λ), could, for example, lead to greater accuracy when calculating fetal hemoglobin oxygen saturation, if used to determine the impact of the interaction of light traveling through the abdominal tissue of a pregnant mammal with her abdomen.

[0028] How much light reaches the fetus is often not linearly related to how much light is projected into the abdomen of the pregnant mammal. Individual combinations of pregnant mammals and fetuses vary in terms of the size and / or intrinsic properties of each individual tissue layer, such as hemoglobin oxygen saturation and the amount of blood passing through the tissue, often making approximations of how much light reaches the fetus or other one-size-fits-all approaches to calculating or correcting the calculation of fetal hemoglobin oxygen saturation inaccurate. Therefore, calibrating the calculation using the physiological properties of the pregnant mammal and / or the combination of pregnant mammal and fetus would help calculate fetal hemoglobin oxygen saturation with greater accuracy.

[0029] Transabdominal fetal oximetry and / or transabdominal fetal pulse oximetry are often performed using near-infrared (NIR) light. NIR light projected into the abdomen of a pregnant mammal can be absorbed, for example, by melanin in the pregnant mammal's skin, the pregnant mammal's myoglobin (muscle) tissue, and the hemoglobin in the pregnant mammal's blood, with deoxygenated hemoglobin absorbing more light than oxygenated hemoglobin. Therefore, knowing how much melanin is in the pregnant mammal's skin, the concentration of her myoglobin layer, and / or her hemoglobin oxygen saturation can aid in predicting how much light or photons her hemoglobin is likely to absorb. This absorption characteristic (in mathematical equations, the absorption coefficient (μ)) a Knowing the λ (or λ) (example equations are provided herein) may allow for more accurate calculation of fetal hemoglobin oxygen saturation, for example, via one or more of the methods disclosed herein.

[0030] In addition, the intensity of light projected into the abdomen of a pregnant mammal often decays exponentially with distance (in this case, the distance between the maternal epidermis and the fetal epidermis, or fetal depth), e.g., according to the inverse square law, such that the intensity of light incident on the fetus is proportional to fetal depth.

[0031] NIR light projected into the abdomen of a pregnant mammal can be scattered, for example, by adipose tissue in the maternal abdomen located between the fetal hemoglobin oxygen saturation probe and the fetus.

[0032] Therefore, factors such as the melanin content, hemoglobin oxygen saturation, myoglobin concentration, and / or adipose tissue thickness of a pregnant mammal will affect how much light enters the fetus. To understand how much light enters the fetus, it is important to understand one or more of these physiological characteristics of a pregnant mammal, so that the analysis of light reflected from the fetus and the subsequent calculation of fetal hemoglobin oxygen saturation can be more accurate.

[0033] In some instances, hemoglobin oxygen saturation calculations are performed using certain assumptions, including, but not limited to, that the path lengths for different wavelengths of light through tissue are the same (or so close that they have negligible impact) and / or that the scattering behavior of light as it passes through tissue is of negligible importance. While these assumptions may be appropriate for simple applications (e.g., determining a user's hemoglobin oxygenation via projecting light through a finger or earlobe), they are not always valid when projecting light deeper into tissue, such as when projecting light into the maternal abdomen to determine hemoglobin oxygen saturation levels for a pregnant mammalian fetus, because the deeper probing geometry, for example, when probing the maternal abdomen, can magnify the path length differences for mismatched wavelengths. Because these assumptions are not always valid in this context, measurements or other calibration factors that take into account how layers of maternal tissue can affect the behavior of light as it passes through the tissue could improve accuracy in determining hemoglobin oxygen saturation levels for the fetus. Examples of such measurements and / or calibration factors are discussed below.

[0034] 1 provides an example system 100 for detecting and / or determining fetal hemoglobin oxygen saturation levels. The components of system 100 may be coupled together via wired and / or wireless communication links. In some cases, wireless communication of one or more components of system 100 may be enabled using short-range wireless communication protocols (e.g., BLUETOOTH®, Near Field Communication (NFC), Radio Frequency Identification (RFID), and Wi-Fi) designed to communicate over relatively short distances, for example, with a computer or personal electronic device (e.g., a tablet computer or smartphone), as described below.

[0035] System 100 includes a light source 105 and a detector 160, which may be contained in a single housing, sometimes referred to as fetal hemoglobin probe 115. Light source 105 may include a single light source or multiple light sources, and detector 160 may include a single detector or multiple detectors.

[0036] The light source 105 transmits light into the abdomen of the pregnant mammal at one or more wavelengths, including NIR. The light source 105 may be, for example, an LED and / or a laser coupled to a fiber optic cable, a tunable light bulb, and / or a tunable LED. In some cases, the light source may be one or more fiber optic cables arranged in an array and optically coupled to a laser. In some cases, the light source 105 is tunable or user-configurable, while in other cases, one or more of the light sources can be configured to emit light within a predefined wavelength range. Additionally or alternatively, there are one or more filters (not shown). These filters / polarizers may also be tunable or user-configurable.

[0037] Certain exemplary light sources 105 have a relatively small form factor and are adapted to operate with high efficiency, which may help conserve space and / or limit heat generated by light source 105. In one embodiment, light source 105 is configured to emit light in the 770 nm to 850 nm range. In some examples, light source 105 may be configured to not emit light that may irritate or burn a patient's skin, for example, and / or harm a fetus. This may be achieved, for example, by configuring and / or instructing light source 105 to emit high-intensity / high-power pulses of light for short durations. The use of high-intensity / high-power pulses of light may increase the likelihood that a detector, such as detector 160, positioned relatively far from the light source will receive sufficient light to be detected following transmission of light into and emission from the abdomen of the pregnant mammal in a manner that is not harmful to the pregnant mammal or her fetus. Additionally or alternatively, one or more light sources 105 may be configured to emit light in a time-division multiplexed manner so that signals received from each of multiple detectors, such as detector 160, are distinguishable from one another. The time-division multiplexed emitted light may be utilized for detectors that are relatively close to light source(s) 105.

[0038] Detector 160 can be configured to detect optical signals emitted from the pregnant mammal and / or fetus, for example, via transmission and / or backscatter. Detector 160 converts the optical signals into electronic signals that are transmitted to a computer or processor and / or to an on-board transceiver that can transmit the signals to a computer / processor. This emitted light can then be processed to determine how much light of various wavelengths passes through the fetus and / or how much light of various wavelengths is reflected and / or absorbed by fetal oxygenated and / or deoxygenated hemoglobin, so that fetal hemoglobin oxygen saturation levels can be determined. This processing is discussed in more detail below.

[0039] Exemplary detectors include, but are not limited to, cameras, conventional photomultiplier tubes (PMTs), silicon PMTs, avalanche photodiodes, and silicon photodiodes. In some embodiments, the detector may have relatively low cost (e.g., less than $50), low voltage requirements (e.g., less than 100 volts), and a non-glass (e.g., plastic) form factor. In other embodiments (e.g., non-contact pulse oximetry), a highly sensitive camera may be deployed to receive light emitted by the abdomen of the pregnant mammal. For example, detector 160 may be a highly sensitive camera adapted to capture subtle changes in fetal skin tone caused by changes in cardiovascular pressure associated with fetal myocardial contractions. In these embodiments, detector 160 and / or fetal hemoglobin probe 115 may or may not be in contact with the abdomen of the pregnant mammal; non-contact embodiments may be used to perform so-called non-contact pulse oximetry. In these embodiments, light source 105 may be adapted to provide light (e.g., light in the visible spectrum, near infrared, etc.) directed toward the abdomen of the pregnant mammal such that detector 160 can receive / detect light emitted by the abdomen of the pregnant mammal and the fetus. The emitted light captured by detector 160 can be transmitted to computer 150 for processing, for example, to convert the image into a measure of fetal hemoglobin oxygen saturation according to one or more of the processes described herein.

[0040] The fetal hemoglobin probe 115, light source 105, and / or detector 160 may be any suitable size and, in some circumstances, may be sized using any suitable sizing system (e.g., girth size and / or small, medium, large, etc.) to accommodate the size of the pregnant mammal. Exemplary lengths for the fetal hemoglobin probe 115 include lengths of 4 cm to 40 cm and widths of 2 cm to 10 cm. In some circumstances, the size and / or configuration of the fetal hemoglobin probe 115 or its components may be dependent on the skin pigmentation of the pregnant mammal and / or fetus. In some circumstances, the fetal hemoglobin probe 115 may be adapted to be applied to the skin of the pregnant mammal via a tape or strap that cooperates with a mechanism (e.g., a snap, a loop, etc.) (not shown). In some embodiments, fetal hemoglobin probe 115 may be configured as a multi-parameter unit that may be configured to communicate, e.g., bidirectionally, with computer 150 and / or a processor, e.g., to integrate, share, and store data among different components of system 100.

[0041] System 100 includes multiple optional independent sensors / probes designed to monitor various aspects of maternal and / or fetal health, which may be in contact with the pregnant mammal. These probes / sensors are a NIRS adult hemoglobin probe 125, a pulse oximetry probe 130, a Doppler and / or ultrasound probe 135, and a uterine contraction measurement device 140. Not all embodiments of system 100 include all of these components. In some embodiments, system 100 may further include an electrocardiogram (ECG) machine (not shown) that can be used to determine the heart rate of the pregnant mammal and / or the fetus, and / or an intrauterine pulse oximetry probe (not shown) that can be used to determine the fetal heart rate. Doppler and / or ultrasound probe 135 is configured to be placed on the abdomen of the pregnant mammal and is sized and shaped approximately like a silver U.S. dollar coin, and can provide information regarding the position, orientation, and / or heart rate of the fetus. The pulse oximetry probe 130 may be a conventional pulse oximetry probe placed on the hand and / or fingers of the pregnant mammal to measure the hemoglobin oxygen saturation of the pregnant mammal. The NIRS adult hemoglobin probe 125 may be placed, for example, on the second finger of the pregnant mammal and configured to use near-infrared spectroscopy to calculate, for example, the ratio of adult oxygenated hemoglobin to adult deoxygenated hemoglobin. The NIRS adult hemoglobin probe 125 may also be used to determine the heart rate of the pregnant mammal.

[0042] Optionally, system 100 may include a uterine contraction measuring device 140 configured to measure the strength and / or timing of uterine contractions of the pregnant mammal. In some embodiments, uterine contractions may be measured by uterine contraction measuring device 140 as a function of pressure (e.g., measured in mmHg, for example) over time. In some cases, uterine contraction measuring device 140 is and / or includes a tocotransducer, an instrument that includes a pressure-sensitive area that detects changes in abdominal contour to measure uterine activity, and in this way monitors the frequency and duration of contractions.

[0043] In another embodiment, the uterine contraction measuring device 140 may be configured to pass an electrical current through the pregnant mammal and measure the change in electrical impedance with each uterine contraction. Additionally or alternatively, uterine contractions may also be measured via near-infrared spectroscopy, for example, using light received / detected by detector 160, since uterine contractions, being muscle contractions, are oscillations of the uterine muscle between contraction and relaxation states. During both of these phases, the oxygen consumption of the uterine muscle differs, and these differences may be detectable using NIRS.

[0044] Measurements and / or signals from NIRS adult hemoglobin probe 125, pulse oximetry probe 130, Doppler and / or ultrasound probe 135, and / or uterine contraction measurement device 140 may be transmitted to receiver 145 for transmission to computer 150 and display on display device 155, and may in some cases be considered secondary signals. As discussed below, measurements provided by NIRS adult hemoglobin probe 125, pulse oximetry probe 130, Doppler and / or ultrasound probe 135, and uterine contraction measurement device 140 may be used in conjunction with fetal hemoglobin probe 115 to isolate a fetal pulse signal and / or fetal heart rate from a maternal pulse signal and / or maternal heart rate. Receiver 145 may be configured to receive signals and / or data from one or more components of system 100, including, but not limited to, fetal hemoglobin probe 115, NIRS adult hemoglobin probe 125, pulse oximetry probe 130, Doppler and / or ultrasound probe 135, and / or uterine contraction measurement device 140. Communication between receiver 145 and other components of the system may occur using wired or wireless communication.

[0045] In some instances, one or more of the NIRS adult hemoglobin probe 125, pulse oximetry probe 130, Doppler and / or ultrasound probe 135, and uterine contraction measurement device 140 may include a dedicated display to provide measurements, for example, to a user or to a medical care provider. It is important to note that not all of these probes may be used in all instances. For example, if a pregnant mammal is using the fetal hemoglobin probe 115 in an environment other than a hospital or treatment facility (e.g., at home or at work), some of the probes of system 100 (e.g., the NIRS adult hemoglobin probe 125, pulse oximetry probe 130, Doppler and / or ultrasound probe 135, and uterine contraction measurement device 140) may not be used.

[0046] In some cases, receiver 145 may be configured to process or pre-process the received signal, for example, by performing a fast Fourier transform (FFT), bandwidth narrowing, and / or phase correlation filtering to make the signal compatible with computer 150 (e.g., converting an optical signal to an electrical signal), amplify the received signal, and / or improve the signal-to-noise ratio (SNR). In some cases, receiver 145 may reside within and / or be a component of computer 150. In some embodiments, computer 150 may be configured to amplify or condition the received detected signal, for example, to improve the signal-to-noise ratio.

[0047] Receiver 145 may be adapted to transmit the received, pre-processed, and / or processed signals to computer 150. Computer 150 may function to process the received signals and facilitate providing results to display device 155, as discussed in more detail below. Exemplary computers 150 include desktop and laptop computers, servers, tablet computers, personal electronic devices, mobile devices (e.g., smartphones), Internet of Things (IoT) devices that may enable remote patient / pregnant mammal monitoring, and the like. Exemplary display devices 155 are computer monitors, tablet computing devices, and displays provided by one or more of the components of system 100. In some cases, display device 155 may be resident on receiver 145 and / or computer 150. Computer 150 may be communicatively coupled to database 170, which may be configured to store physiological characteristics and / or combinations of physiological characteristics of the pregnant mammal and / or its fetus, the influence of the physiological characteristics on light behavior, information related to the calculation of hemoglobin oxygen saturation levels, calibration coefficients, etc. In some embodiments, database 170 may be local (e.g., coupled to computer 150) and / or remote (e.g., a cloud computing database).

[0048] In some embodiments, the pregnant mammal may be electrically isolated from one or more components of the system 100, for example, by an electrical isolator 120. Exemplary electrical isolators 120 include circuit breakers, ground fault switches, and fuses.

[0049] System 100 may further include an electrocardiogram (ECG) machine 175 and / or a ventilation / respiratory signal source 180. ECG 175 may be used to determine the heart rate of the pregnant mammal and / or the fetus. In some embodiments, ECG 175 may be a fetal ECG used internally via birth canal placement, which may be used to measure the fetal heart rate, for example.

[0050] In some embodiments, system 100 may include a ventilation / respiratory signal source 180 that may be configured to monitor the respiration rate of the pregnant mammal and provide a respiratory signal indicative of the respiration rate of the pregnant mammal, e.g., to computer 150. Additionally or alternatively, ventilation / respiratory signal source 180 may be a source of a ventilation signal obtained, e.g., through cooperation with a ventilation machine. Exemplary ventilation / respiratory signal source 180 include, but are not limited to, a carbon dioxide measuring device, a stethoscope and / or an electroacoustic stethoscope, a device that measures chest excursion for the pregnant mammal, and a pulse oximeter. A signal from a pulse oximeter may be analyzed to determine variability in a PPG signal corresponding to respiration for the pregnant mammal. Additionally or alternatively, ventilation / respiratory signal source 180 may be configured to provide a respiratory signal corresponding to the frequency at which gas (e.g., air, anesthetic, etc.) is provided to the pregnant mammal, e.g., during a surgical procedure. This respiratory signal may be used, e.g., to determine the respiratory rate for the pregnant mammal.

[0051] In some embodiments, measurements provided by the NIRS adult hemoglobin probe 125, pulse oximetry probe 130, Doppler and / or ultrasound probe 135, uterine contraction measurement device 140, ECG 175, and / or arousal / respiratory signal source 180 may be used in conjunction with the fetal probe 115 to isolate the fetal pulse signal and / or fetal heart rate from the maternal pulse signal and / or maternal heart rate.

[0052] 1B provides an example of a processor-based system 151 capable of storing and / or executing instructions for the processes described herein. Processor-based system 151 may be representative of, for example, computing device 150. It should be noted that not all of the various processor-based systems that may be employed in accordance with embodiments of the present invention have all of the features of system 151. For example, a particular processor-based system may not include a display because such functionality is provided by a client computer communicatively coupled to the processor-based system or because display functionality is not required. Such details are not important to the present invention.

[0053] System 151 includes a bus 12 or other communication mechanism for communicating information and a processor 14 coupled with bus 12 for processing information. System 151 also includes a main memory 16, such as a random access memory (RAM) or other dynamic storage device, coupled to bus 12 for storing information and instructions to be executed by processor 14. Main memory 16 may also be used to store temporary variables and / or other intermediate information during execution of instructions to be executed by processor 14. System 151 also includes a read-only memory (ROM) 18 or other static storage device coupled to bus 12 for storing static information and instructions for processor 14. A storage device 10, which may be one or more of a hard disk, a flash memory-based storage device, a magnetic storage medium, an optical storage medium (e.g., Blu-ray Disc, Digital Versatile Disc (DVD)-ROM), or any other storage medium readable from the processor 14, is provided and coupled to bus 12 for storing information and instructions (e.g., an operating system, application programs, etc.).

[0054] System 151 may be coupled via bus 12 to a display 22, such as a flat panel display, for displaying information to a user. An input device 24, such as a keyboard including alphanumeric and other keys, may be coupled to bus 12 for communicating information and command selections to processor 14. Another type of user input device is a cursor control device 26, such as a mouse, trackball, or cursor direction keys, for communicating directional information and command selections to processor 14 and for controlling cursor movement on display 22. Although not shown in detail, other user interface devices, such as a microphone, speaker, etc., may be involved in receiving user input and / or providing output.

[0055] The processes referred to herein may be performed by processor 14 executing appropriate sequences of processor-readable instructions stored in main memory 16. Such instructions may be read into main memory 16 from another processor-readable medium, such as storage device 10, and execution of the sequences of instructions stored in main memory 16 causes processor 14 to perform the associated actions. In alternative embodiments, hardwired circuitry or firmware-controlled processing units (e.g., field programmable gate arrays) may be used in place of or in combination with processor 14 and its associated computer software instructions to implement the present invention. The processor-readable instructions may be rendered in any computer language.

[0056] System 151 may further include a communications interface 28 coupled to bus 12. Communications interface 28 may be adapted to provide a bidirectional data communications channel with a computer network that provides connectivity to the plasma processing system discussed above. For example, communications interface 28 may be a LAN card that provides a data communications connection to a compatible local area network (LAN), which itself is communicatively coupled to other computer systems. The exact details of such communications paths are not important to the present invention. What is essential is that system 151 can send and receive messages and data through communications interface 28 and, in that manner, communicate with other controllers, etc.

[0057] 2A is a block diagram illustrating an example fetal probe 115A having a housing 111A containing an example array of light source 105 and multiple detectors 160A-160D. Housing 111A may be any housing configured to contain the components of fetal probe 115A, including light source 105, multiple detectors 160A-160D, optical power source 121 (e.g., a battery), fetal depth probe 138, maternal probe 133, communication device (e.g., antenna or transceiver) 142, processor 151, power port 141, and / or communication port 131. Example fetal probe 115A includes light source 105 substantially aligned with four detectors 160A-160D along the Y-axis. In some embodiments, the gain or sensitivity of detectors 160A-160D may vary with their respective positions relative to light source 105, for example, so that detectors positioned farther away from light source 105 (e.g., detectors 160A and 160B) have greater gain / sensitivity than detectors positioned closer to light source 105 (e.g., detectors 160C and 160D).

[0058] In one embodiment, fetal probe 115A may include light source 105 configured to emit light at multiple wavelengths, such as 735 nm, 760 nm, 810 nm, 808 nm, and 850 nm, and detectors 160A-160D may each be configured to detect light / photons at each of these wavelengths. An exemplary distance between light source 105 and detector 160A is 3 cm, an exemplary distance between light source 105 and detector 160B is 5 cm, an exemplary distance between light source 105 and detector 160C is 7 cm, and an exemplary distance between light source 105 and detector 160D is 10 cm.

[0059] 2B is a block diagram illustrating an example fetal probe 115B having multiple light sources 105 and multiple detectors 160A-160U arranged in an example array within housing 111B. Housing 111B may be any housing configured to accommodate the components of fetal probe 115B, including multiple light sources 105, multiple detectors 160A-160U, optical power source 121 (e.g., a battery), fetal depth probe 138, maternal pulse oximetry probe 133, communication device (e.g., antenna or transceiver) 142, processor 151, power port 141, and / or communication port 131. Example fetal probe 115A includes light source 105 substantially aligned with four detectors 160A-160D along the Y-axis.

[0060] Exemplary fetal probe 115B includes a row of three light sources 105 positioned approximately in the center of housing 111B along the Y-axis. Light sources 105 may be substantially aligned with one another along the X-axis. The housing may further include nine detectors 160A-160I positioned in three rows and three columns above light sources 105 and nine detectors 160K-160R positioned in three rows and three columns below light sources 105. In some embodiments, the gain or sensitivity of detectors 160E-160R may be varied relative to their respective positions relative to light source 105, e.g., detectors positioned farther away from light source 105 have greater gain / sensitivity, as described above with respect to fetal probe 115A.

[0061] 2A and 2B are provided as examples only and are not intended to limit the arrangement and / or number of light sources 105 and / or detectors 160 that may be used. Any arrangement of light sources and detectors may be used to detect optical signals and convert them into the detected electronic signal(s) discussed herein.

[0062] 3A and 3B provide illustrations 301 and 302, respectively, of several layers of tissue present in two different maternal abdomens, including their respective fetuses. Information used to generate illustrations 301 and 302 may be received, for example, from an ultrasound imaging device (e.g., Doppler / ultrasound probe 135) and / or MRI images.

[0063] Diagrams 301 and 302 provide example dimensions for several layers of maternal tissue and fetuses located proximate the placement of fetal hemoglobin probe 115, including the depth of the fetus within the abdomen of each pregnant mammal. Fetal depth may be understood, for example, as the distance between the epidermis of the pregnant mammal and the epidermis of the fetus and / or the combined width of the maternal tissue layers and amniotic fluid. Diagram 301 shows maternal abdominal tissue for a fetus that has reached 29 weeks of gestation. The tissue layers shown in diagram 301 include subcutaneous fat layer 305A, abdominal (skeletal) muscle layer 310A, intraperitoneal fat layer 315A, uterine wall (smooth muscle) layer 320A, amniotic fluid layer 325A, and fetus 330A. Width measurements for each of these layers were taken proximate (e.g., directly below) fetal hemoglobin probe 115. The approximate locations of where the width measurements were taken are indicated by lines connecting the top and bottom surfaces of the layers of interest. For example, in Figure 3A, the width of the subcutaneous fat layer 305A is represented by line 1, the width of the abdominal muscle layer 310 is represented by line 2, the width of the intra-abdominal fat layer 315A is represented by line 3, the width of the uterine wall layer 320A is represented by line 4, and the width of the amniotic fluid layer 325A is represented by line 5. The approximate dimensions for these layers of maternal tissue located proximate to (e.g., directly beneath) the fetal hemoglobin probe 115 are as follows: Subcutaneous fat layer 305A: 10.2 mm (represented by line 1); abdominal muscle layer 310A: 7.1 mm (represented by line 2); Intraperitoneal fat layer 315A: 2.0 mm (represented by line 3); Uterine wall layer 320A: 3.1 mm (represented by line 4); Amniotic fluid layer 325A: 3.6 mm (represented by line 5); and Fetus 330A. In this example, the total distance from the maternal epidermis to the epidermis of fetus 330A (ie, fetal depth) is 28 mm.

[0064] The fetus shown in illustration 302 of Figure 3B has reached 35 weeks of gestation. The tissue layers shown in illustration 302 include subcutaneous fat layer 305B, abdominal muscle (skeletal muscle) layer 310B, intra-abdominal fat layer 315B, uterine wall (smooth muscle) layer 320B, and fetus 330B. Width measurements for each of these layers were taken proximate (e.g., directly beneath) the fetal hemoglobin probe 115. The approximate locations of where the width measurements were taken are represented by lines connecting the top and bottom surfaces of the layers of interest. For example, in Figure 3B, the width of subcutaneous fat layer 305B is represented by line 1, the width of abdominal muscle layer 310B is represented by line 2, the width of intra-abdominal fat layer 315B is represented by line 3, and the width of uterine wall layer 320B is represented by line 2. The approximate dimensions for the maternal tissue layers located proximate (e.g., directly beneath) the fetal hemoglobin probe 115 are as follows: Subcutaneous fat layer 305B: 11.3 mm (represented by line 1); abdominal muscle layer 310B: 3.1 mm (represented by line 2); Intraperitoneal fat layer 315B: 3.1 mm (represented by line 3); Uterine wall layer 320B: 2.3 mm (represented by line 4); and Fetus 330B.

[0065] In this example, the total distance from the maternal skin to the fetus (i.e., fetal depth) is 19.8 mm. Because the fetus is more developed and larger at 35 weeks gestation, the width of the amniotic fluid is negligible and is not included in this example. In addition, for illustrations 301 and 302, the width of the skin of a pregnant mammal is also negligible, approximately 1 mm to 1.5 mm.

[0066] In some embodiments, fetus 330A and / or fetal layer 330B may be divided into one or more additional layers (not shown). These layers may be associated with, for example, one or more of vernix caseosa, hair, skin, bone, etc. In some embodiments, information regarding one or more of these layers (e.g., the melanin content of the fetal skin and / or hair color) may be inferred from, for example, the parentage of the fetus, genetic testing of the fetus, and / or direct observation of the fetus, for example, via optical endoscopy and / or transvaginal examination.

[0067] FIG. 3C depicts a midsagittal plan view of a pregnant mammal's abdomen 305 with a fetal hemoglobin probe 115 positioned thereon. As shown in FIG. 3, the pregnant mammal's abdomen 305 includes a fetus 330, a uterus 340, and an approximation of maternal tissue (e.g., skin, muscle, etc.) 330. The fetal hemoglobin probe 115 can be positioned anywhere on the pregnant mammal's abdomen, and in some cases, more than one fetal hemoglobin probe 115 may be placed on the pregnant mammal's abdomen. FIG. 3C further illustrates that a first optical signal 420A is projected into the pregnant mammal's abdomen, with the penetration depth of the first optical signal 420A being limited to the edge of the uterine wall 340, where the first optical signal 420A then backscatters or transmits to a detector, such as detector 160, of the fetal hemoglobin probe 115. 3C also shows that second optical signal 420B is projected into the abdomen of the pregnant mammal and penetrates fetus 330 before being detected by detector 160. First optical signal 420A can include a single wavelength or multiple wavelengths of light, which can be, for example, red or NIR. In some embodiments, the first optical signal can include light of two distinct wavelengths or wavelength ranges, i.e., one red and one NIR light. Second optical signal 420B can include a single wavelength or multiple wavelengths of light, for example, red or NIR light. The wavelength(s) of second optical signal 420B can be different from first optical signal 420A and / or can be projected into the abdomen of the pregnant mammal at a different time than first optical signal 420A so that second optical signal 420B can be distinguished from first optical signal 420A during processing of the detected portions of each of first optical signal 420A and second optical signal 420B. In some embodiments, the first optical signal 420A and the second optical signal 420B may include two different wavelengths or wavelength ranges of light, one red and one NIR, that are slightly different from each other. For example, the first optical signal 420A may be red and the second optical signal 420B may be NIR, or either the first optical signal 420A or the second optical signal 420B may be red or NIR.In these embodiments, the wavelengths of the first optical signal 420A and the second optical signal 420B can be selected such that the difference in their respective path lengths is negligible. The two wavelengths can be calculated by, for example, calculating the absorption of the optical signals, i.e., (μ, ), using, for example, a Lambert-Beer calculation or a modified Lambert-Beer calculation as described herein. a (λ)) and / or scattering (μ s This would allow for pulse oximetry calculations using the difference in (λ).

[0068] Figure 4A depicts an example fetal hemoglobin probe 115C in contact with the abdomen of a pregnant mammal in a manner similar to that shown in Figure 3. Figure 4A also shows multiple tissue layers. More specifically, Figure 4A shows a first layer representing maternal skin layer 415, a second layer representing maternal subcutaneous fat layer 421, a third layer representing maternal abdominal (skeletal) muscle layer 425, a fourth layer representing maternal intra-abdominal fat layer 430, a fifth layer representing uterine wall (smooth muscle) layer 435, a sixth layer representing amniotic fluid layer 440, and a seventh layer representing fetus 330.

[0069] Fetal hemoglobin probe 115C includes first light source 105A emitting first light beam 420A1, second light source 105B emitting second light beam 420A1, and detector 160. First light beam 420A1 and / or second light beam 420B1 may comprise a single wavelength or multiple wavelengths of light, e.g., in the red, near-infrared, or infrared spectrum. In some circumstances, the characteristics of light beam 420A1 may be different in wavelength from light beam 420B1 and / or may be projected onto the abdomen of the pregnant mammal at different times, so that the light projected from the two light sources can be distinguished when received by detector 160 and processed according to one or more of the processes described herein. In some embodiments, fetal hemoglobin probe 115C may include a filter (not shown) for detector 160 that can attenuate the light from first light source 105A and second light source 105B so that detector 160 detects equal amounts of light from first light source 105A and second light source 105B.

[0070] In many cases, the depth of light propagation through the abdomen of the pregnant mammal depends on the distance between the light source and the detector. In some embodiments, the position of the first light source 105A and / or the second light source 105B can be adjusted (e.g., moved closer to or farther from the detector 160) to adapt the depth of propagation for light emitted from the light source. The adjustment may be facilitated, for example, by a track or other positioning device (not shown) included in the fetal hemoglobin probe 115C. In some cases, the positioning of the first light source 105A and / or the second light source 105B may be adjusted depending on the depth of the fetus 330 within the abdomen of the pregnant mammal (i.e., a measurement of the width of the maternal tissue 405 located between the fetal hemoglobin probe 115C and the fetus 330). Measurements of the depth of the fetus 330 within the abdomen of the pregnant mammal may be provided, for example, by an ultrasound or Doppler probe such as Doppler / ultrasound probe 135 and / or by MRI images, some of which are illustrated in diagrams 301 and 302.

[0071] In some embodiments, first light source 105A may be positioned relative to detector 160 such that light emitted from the first light source (i.e., light beam 420A1) only propagates through maternal tissue 405 and does not reach fetus 330. Second light source 105B may be positioned farther away from detector 160 (relative to first light source 105A) such that light projected by second light source 105B (i.e., light beam 420B1) penetrates deeper into the abdomen of the pregnant mammal than light beam 420A1, and backscattering therefrom and / or transmission therethrough is detected by detector 160. In other words, light source 105A may be positioned such that light beam 420A1 only illuminates maternal tissue 1405, such that the portion of light beam 420A1 detected by detector 160 is only backscattered from maternal tissue 405 and not from fetus 330 and / or passes through only maternal tissue 405 and not through fetus 330, while light source 105B may be positioned such that light beam 420B1 illuminates both maternal tissue 405 and fetus 330, such that the portion of light beam 420B1 detected by detector 160 is backscattered from and / or passes through maternal tissue 405 and fetus 330. This positioning of first light source 105A facilitates short-set (SS) measurements, and the path of first light beam 420A1 and / or the amount of first light beam 420A1 detected by detector 160 may be referred to herein as the SS channel. This positioning of the second light source 105B facilitates long-distance (LS) measurements, and the path of the second light beam 420B1 and / or the amount of detection of the second light beam 420B1 by the detector 160 may be referred to herein as the LS channel.

[0072] 4B depicts an example fetal probe 115B positioned on the abdomen of a pregnant mammal. The maternal tissue of the abdomen of the pregnant mammal is represented as maternal tissue 405, and the fetus within the abdomen of the pregnant mammal is represented as fetus 410.

[0073] Fetal probe 115D has one light source 105 and six detectors 160A, 160B, 160C, 160D, 160E, and 160F, each having a different position relative to light source 105, with first detector 160A being closest to light source 105 and sixth detector 160F being furthest from light source 105. The positions of detectors 160A-160F relative to light source 105 are sometimes referred to herein as the source-detector distance. In some embodiments, the detectors 160A-160F may be arranged in a line, with the first detector 160A positioned 1 cm away from the light source 105, the second detector 160B positioned 1 cm away from the first detector 160A, the third detector 160C positioned 1 cm away from the second detector 160B, the fourth detector 160D positioned 1 cm away from the third detector 160C, the fifth detector 160E positioned 1 cm away from the fourth detector 160D, the sixth detector 160F positioned 1 cm away from the fifth detector 160E, and so on, spaced 1 cm apart from each other.

[0074] Light source 105 projects optical signal 420 into the pregnant mammal's abdomen 405, and the resulting optical signal will be detected by one or more of detectors 160A-160F. It is expected that detectors closer to light source 105 will detect the portion of the optical signal that impinges on the pregnant mammal's abdomen 405 and not on the fetus 330; in some embodiments, first detector 160A and / or second detector 160B are positioned, e.g., via a light source / detector distance setting, so that most, if not all, of the optical signals 420A1 and 420B1 detected by detector 160A and / or second detector 160B are only incident on the pregnant mammal's abdomen 405 (i.e., not on the fetus). Third through sixth detectors 160C-160F will detect the portions of optical signals 420C, 420D, 420E, and 420F that impinge on the pregnant mammal 405 and fetus 330, as shown in FIG. 4 . In some cases, the third detector 160F may be positioned 3 cm to 5 cm from the light source, and the sixth detector 160F may be positioned 6 cm to 10 cm from the light source. Additionally or alternatively, the third through sixth detectors 160C-160F may be positioned within 4 cm to 10 cm of the light source.

[0075] As the source-detector distance increases, the proportion of the light signal that corresponds to light incident on fetus 330 increases. Thus, light signal 420F may include a higher proportion of light incident on the fetus than, for example, 420E or 420D.

[0076] Figures 4C and 4D depict an exemplary fetal hemoglobin probe 115E in contact with the abdomen of a pregnant mammal in a manner similar to that shown in Figures 4A and 4B, with maternal tissue layers similar to those shown in Figure 4A. The embodiment shown in Figure 4C utilizes simplified layers of maternal tissue 450, while the embodiment shown in Figure 4D shows many layers of maternal tissue, with maternal tissue layers similar to those shown in Figure 4A, with fetal probe 115E configured to enable dual short-range (SS) analysis of light backscattered from and / or transmitted through the abdomen of a pregnant mammal and a fetus contained therein.

[0077] Fetal probe 115E includes first light source 105A emitting first light signal 420C, compact detector 455, second light source 105B emitting second light signal 420, and detector 160. A first portion 420A3 of the second light signal may be detected by compact detector 455, and a second portion 420B of the second light signal may be detected by detector 160. First light beam 420C and / or second light beam 420 may include light of a single wavelength or multiple wavelengths, e.g., in the red, near-infrared, and / or broadband spectrum. In some circumstances, the wavelength of light signal 420C may be different from the wavelength of light signal 420 and / or may be projected at different times to allow differentiation between the light projected from the two light sources when received by detector 160 and processed according to one or more of the processes described herein. Miniature detector 455 may be similar to detector 160, but may have, for example, a smaller size and / or lower sensitivity. In some cases, miniature detector 455 may be a miniature fiber detector. In some embodiments, fetal probe 115E may include a filter (not shown) for detector 160 that can attenuate light so that detector 160 detects equal amounts of light from first light source 105A and second light source 105B.

[0078] In some embodiments, the position of first light source 105A and / or second light source 105B can be adjusted (e.g., moved closer to or farther from detector 160) to accommodate, for example, the depth of penetration of light from the light source as detected by detector 160. The adjustment may be facilitated, for example, by manual manipulation and / or placement of the detector and / or by moving the detector along a track or other positioning device contained within and / or associated with fetal probe 115E (not shown). In some cases, the positioning of first light source 105A and / or second light source 105B may be adjusted depending on the depth of fetus 330 within the abdomen of the pregnant mammal (i.e., a measurement of the width of maternal tissue 450 located between fetal probe 115E and fetus 330). Measurements of the depth of the fetus 330 within the abdomen of the pregnant mammal may be provided, for example, by an ultrasound or Doppler probe such as the Doppler / ultrasound probe 135 and / or by imaging the abdomen of the pregnant mammal, the illustrations of which are shown in Figures 3A and 3B.

[0079] In some embodiments, first light source 105A may be positioned relative to detector 160 such that light emitted by the first light source (i.e., optical signal 420C) only propagates through maternal tissue 305 and does not reach fetus 330. Second light source 105B may be positioned farther away from detector 160 (relative to first light source 105A) such that light projected by second light source 105B (i.e., optical signal 420) projects deeper into the abdomen of the pregnant mammal than optical signal 420C and reaches fetus 330, and light backscattered from and / or transmitted through the fetus is detected by detector 160. Miniature detector 455 may be positioned between first light source 105A and second light source 105B such that light (i.e., optical signal 420) only propagates through maternal tissue 450 before being detected by miniature detector 455 and does not reach fetus 330. This positioning of first light source 105A facilitates the collection of a first set of short-standby (SS) measurements, where the path of first optical signal 420C and / or the amount of detection of first optical signal 420C by detector 160 may be referred to herein as a first SS channel. This positioning of second light source 105B facilitates long-standby (LS) measurements, where the path of second optical signal 420 and / or the amount of detection of second optical signal 420 by detector 160 may be referred to herein as a LS channel. This positioning of compact detector 455 facilitates the collection of a second set of short-standby (SS) measurements, where the path of first optical signal 420C and / or the amount of detection of first optical signal 420C by detector 160 may be referred to herein as a second SS channel. Thus, fetal probe 115E provides SS measurements of both first light source 105A and second light source 105B.

[0080] 5 provides a flowchart illustrating a process 500 for determining fetal hemoglobin oxygen saturation levels. Process 500 may be performed, for example, by any of the systems or system components described herein.

[0081] Initially, a detected composite electronic signal will be received from a photodetector (e.g., detector 160) by a processor and / or a computer, such as computer 150 (step 505). The detected composite electronic signal may be received, for example, from a photodetector, a transceiver coupled to the photodetector, and / or a fetal hemoglobin probe, such as fetal hemoglobin probe 115.

[0082] The detected composite electronic signal may correspond to optical signals of multiple wavelengths emitted (e.g., via transmission, backscattering, and / or reflection) from the abdomen of the pregnant mammal and / or her fetus. The light entering and exiting the abdomen of the pregnant mammal may be generated by one or more light sources, such as light source 105, and may be of any acceptable frequency or wavelength (e.g., near-infrared (NIR)) and / or combination of frequencies and / or wavelengths. In some embodiments (e.g., when multiple detectors are used), the received detected composite electronic signal may include and / or be associated with a detector identifier (e.g., a code) so that the location of a particular detected composite electronic signal can be known. This location may then be used to analyze the received detected composite electronic signal to determine various coefficients of the detected light and / or imaged tissue.

[0083] In step 510, the path length and / or degree of scattering and / or absorption of each wavelength of light emitted from the abdomen of the pregnant mammal is measured and / or determined, for example, through analysis of the detected first light signal. In some embodiments, performing step 510 may include using a modified Beer-Lambert law, reproduced below as Equation 1. Equation 1 may, for example, provide an absorption coefficient (μ) for a particular wavelength: a (λ), the change in absorption coefficient, and / or the effective mean path length factor (DPF) for a particular wavelength (λ).

number

number

[0084] In some embodiments, using Equation 1, absorption coefficients may be determined for different layers of maternal tissue (also referred to herein as individual absorption coefficients) using, for example, optical properties of the tissue type and / or maternal geometry (e.g., tissue layer width) and / or tissue density. For example, a set of absorption coefficients for different types and / or characteristics of maternal tissue may be experimentally determined and / or modeled based on the properties of the maternal tissue layers. Exemplary properties include, but are not limited to, tissue type, tissue density, tissue layer thickness, tissue layer location (e.g., DFP and / or distance between the light source and detector (represented by r in relation to Equation 1)), and / or optical properties (e.g., scattering coefficients and / or absorption coefficients for known tissue widths, which may be modified or otherwise adjusted based on, for example, the geometry of a particular pregnant mammal and / or fetus). In some embodiments, these individual absorption coefficients may then be aggregated to generate an overall absorption coefficient that more closely approximates the absorption of light for a particular situation (e.g., a particular pregnant mammal, a particular location in the abdomen of a pregnant mammal, etc.).

[0085] In some embodiments, steps 505-515 may be performed for each individual pregnant mammal, e.g., to customize or calibrate the instruments and / or calculations to account for individual physiology, instrumentation (e.g., light source and / or detector) location, noise, etc., among other factors. Additionally or alternatively, in other embodiments, steps 505-515 may be performed multiple times (e.g., hundreds, thousands, etc.) to determine multiple calibration coefficients. In some cases, the multiple determined calibration coefficients may be used, e.g., to determine an average calibration coefficient for the pregnant mammal, which may be associated with one or more physiological characteristics of the pregnant mammal. For example, in one embodiment, calibration coefficients for 10,000 pregnant women may be determined. These calibration factors may then be used, for example, to determine a universal calibration factor for all pregnant women (e.g., an average calibration factor for 10,000 pregnant women), and / or these calibration factors may be grouped according to one or more physiological factors, including, but not limited to, fetal gestational age, maternal weight, maternal height, maternal melanin content, etc.

[0086] Optionally, in step 520, one or more physiological characteristics or parameters of the pregnant mammal and / or fetus are received and / or determined (e.g., via analysis of ultrasound information or images of the pregnant mammal, an illustration of which is provided by FIGS. 3A and 3B). Exemplary physiological characteristics include, but are not limited to, the melanin content and / or degree and / or type of skin pigmentation of the female and / or fetus, fetal depth, fetal gestational age, and / or the width of one or more layers of maternal or fetal tissue, abdominal wall thickness for the pregnant mammal, percentage of hemoglobin blood concentration, and the degree of blood perfusion in tissue, which may be measured, for example, via DC tissue measurements. In some cases, physiological characteristics may be grouped as intrinsic or geometric characteristics, with exemplary intrinsic characteristics being blood or tissue oxygenation and / or hemoglobin concentration levels, and body mass index (BMI), abdominal wall thickness, and / or abdominal wall layer thickness being geometric characteristics.

[0087] One or more physiological characteristics of the pregnant mammal and / or fetus may be associated (e.g., indexed in a database table) with calibration factors, e.g., in an index or look-up table (step 525). In some embodiments, these associations can be used to select an appropriate calibration factor for a particular pregnant mammal and / or fetus, as discussed in more detail below with respect to FIG. 13. The calibration factor, the one or more physiological characteristics of the pregnant mammal and / or fetus, and / or the association(s) between them may then be stored (step 530) in a memory resident in a database, e.g., database 170, and / or a computer, e.g., computer 150. Sometimes, the calibration factors may be aggregated and correlated with physiological attributes so that assumptions / calibration factors can be determined and / or applied without having to calculate a calibration factor for each pregnant mammal individually.

[0088] FIG. 6 provides a flow chart illustrating a process 600 for determining fetal hemoglobin oxygen saturation levels using physiological characteristics of a pregnant mammal determined using maternal detected electronic signals.

[0089] Process 600 may be performed, for example, by system 100 and / or its components. Process 600 may be performed in situ, for example, during labor or fetal delivery and / or during a medical examination of a pregnant mammal. In some cases, process 600 may be performed continuously, periodically, and / or as needed over a period of time, such as labor and fetal delivery, so that, for example, fetal hemoglobin oxygen saturation levels may be calibrated and recalibrated as needed over time and / or as conditions for the fetus and / or pregnant mammal change, such as when the fetus is progressing through the birth canal.

[0090] Initially, one or more maternal detected electronic signals corresponding to optical signals emitted from the abdomen of the pregnant mammal will be received (step 605). The optical signals are generated by a light source, such as light source 105, impinge on the abdomen of the pregnant mammal, pass through a portion of the tissue of the pregnant mammal, are reflected or backscattered, and pass through the maternal tissue where they will be detected by a detector, such as detector 160. Exemplary optical signals such as the optical signals detected by the detector and received in step 605 are shown in FIG. 3C as first optical signal 325A and second optical signal 420B.

[0091] In step 610, the maternal detected electronic signal is analyzed to determine one or more physiological characteristics of the pregnant mammal (step 615). The analysis may be, for example, a frequency domain and / or time-of-flight analysis performed by a fetal hemoglobin probe configured to obtain time-of-flight measurements for photons projected into the maternal abdomen. In some embodiments, determining the physiological characteristics for the pregnant mammal may be performed by determining how tissues of the pregnant mammal respond to incident light, for example, via measurements of light absorption and / or scattering in step 610. In some embodiments, light absorption and / or scattering may be expressed as an absorption coefficient or scattering coefficient, respectively, and used in one or more equations described herein. Then, in step 620, a calibration coefficient for the physiological characteristics is determined (step 620). In some cases, steps 610 and 615 may be performed to determine one or more intrinsic physiological characteristics of the pregnant mammal that may be uniform across a portion of the pregnant mammal's abdomen. Such intrinsic physiological characteristics include, but are not limited to, the melanin content of the female's skin and / or the degree and / or type of skin pigmentation, fetal depth, the width of one or more layers of maternal or fetal tissue, abdominal wall thickness for a pregnant mammal, hemoglobin oxygen saturation, the degree of blood perfusion in abdominal tissues, whether the pregnant mammal is anemic, tissue oxygen saturation, and hemoglobin concentration levels.

[0092] Determining (i.e., calculating) and / or selecting the calibration coefficients in step 620 may be done, for example, by assessing how much light from the incident optical signal is absorbed and / or scattered by the abdominal tissue of the pregnant mammal and / or assessing the time of flight for photons of the optical signal to travel through the abdominal tissue of the pregnant mammal and be detected by a detector. In some embodiments, determining / selecting the calibration coefficients in step 620 may be accomplished by querying a database, such as database 170, and / or memory resident in a computer, such as computer 150, for calibration coefficients corresponding to the physiological characteristics determined in step 615. The database may be populated with the physiological characteristics and calibration coefficients correlated via process 500. In some embodiments, the associations between the results of performing steps 605, 610, 615, and / or 620 may be mapped to one another (step 625), and the results of performing steps 605, 610, 615, and / or 620 may be stored, for example, in a database such as database 170 and / or memory resident within a computer such as computer 150.

[0093] In one embodiment, the physiological characteristic determined in step 615 may be the skin pigmentation, pigmentation, and / or melanin content of the pregnant mammal, which may be determined, for example, by determining how much light incident on the abdomen of the pregnant mammal is absorbed by the skin of the pregnant mammal. The skin pigment of the pregnant mammal affects how much of the incident light is absorbed, which in turn affects how much of the light incident on the abdomen of the pregnant mammal travels through maternal tissue to the fetus, and may be associated with a known or calculated coefficient determined and / or selected in step 620. For example, performing 620 may include querying a database for a calibration coefficient associated with how much light the skin of the pregnant mammal absorbs. In this embodiment, the calibration coefficient may be an absorption coefficient that may be associated with the absorption rate and / or skin pigment of the pregnant mammal.

[0094] In another embodiment, the maternal detected electronic signal received in step 605 may be analyzed in step 610 to determine a physiological characteristic, i.e., the concentration or thickness of the myoglobin or muscle layer of the pregnant mammal's abdomen. This analysis may be performed, for example, using a fetal hemoglobin probe configured as a frequency-domain NIRS system and / or using a fetal hemoglobin probe configured to obtain the time-of-flight for photons projected into the maternal abdomen to penetrate the maternal myoglobin layer, be reflected back to a detector. The pregnant mammal's myoglobin tissue can absorb light projected into the maternal abdomen, and measuring and / or calculating how much light is absorbed (e.g., not detected) by the pregnant mammal's abdominal tissue could be used to determine the physiological characteristic of how thick and / or dense the maternal myoglobin layer(s) are. In step 620, this physiological characteristic may be used, for example, to calculate a calibration factor and / or may be used to query a database of calibration factors to find a calibration factor associated with the physiological characteristic of myoglobin thickness and / or concentration determined for the pregnant mammal.

[0095] In another embodiment, the maternal detected electronic signal received in step 605 may be analyzed in step 610 to determine a physiological characteristic, i.e., the total thickness of the pregnant mammal's abdomen (sometimes referred to herein as fetal depth), which may change over the course of pregnancy due to fetal size increase. Additionally or alternatively, the thickness of the pregnant mammal's abdominal tissue may change over the course of pregnancy and / or during labor and delivery of the fetus due to preeclampsia or eclampsia, which may cause edema that alters the thickness of the pregnant mammal's abdomen. For this embodiment, the analysis of step 610 may be performed, for example, using a fetal hemoglobin probe configured as a frequency-domain NIRS system and / or a fetal hemoglobin probe configured to obtain the time of flight for photons projected into the maternal abdomen, penetrate the maternal abdominal layers, and reflect back to a detector. The abdominal tissue of the pregnant mammal can absorb light projected into the maternal abdomen, and measuring and / or calculating how much light is absorbed (e.g., not detected) by the abdominal tissue of the pregnant mammal could be used to determine a physiological characteristic of how thick the abdominal tissue of the pregnant mammal is. In step 620, this physiological characteristic may be used, for example, to calculate a calibration factor and / or to query a database of calibration factors to find a calibration factor associated with the physiological characteristic of myoglobin concentration and / or thickness determined for the pregnant mammal.

[0096] In another embodiment, the maternal detected electronic signal received in step 605 may be analyzed in step 610 to determine a physiological characteristic, i.e., the thickness of the adipose layer, or fat layer, of the pregnant mammal's abdomen. This analysis may be performed, for example, using a fetal hemoglobin probe configured as a frequency-domain NIRS system and / or using a fetal hemoglobin probe configured to obtain the time-of-flight for photons projected into the maternal abdomen to penetrate the maternal adipose layer, be reflected back to a detector. The adipose tissue of the pregnant mammal can scatter light projected into the maternal abdomen, and measuring and / or calculating how much light is scattered (e.g., not detected) by the adipose tissue of the pregnant mammal could be used to determine the physiological characteristic of how thick the maternal adipose layer(s) are. In step 620, this physiological characteristic may be used, for example, to calculate a calibration factor and / or may be used to query a database of calibration factors to find a calibration factor associated with the physiological characteristic of adipose thickness determined for the pregnant mammal.

[0097] 7A is a flow chart illustrating a process 700 for determining fetal depth and / or oxygen saturation levels for fetal hemoglobin. Process 700 may be performed, for example, by system 100 and / or its components.

[0098] Optionally, in step 705, a plurality of first detected electronic signals, each corresponding to an optical signal of one or more wavelengths projected into the abdomen of the pregnant mammal by one or more light sources, such as light source 105, and emitted from the abdomen via, for example, reflection, backscattering, and / or transmission (i.e., through the maternal abdomen), are received by a computer or processor, such as computer 150. Each first detected signal of the plurality of first detected signals may be received from a different detector, such as detectors 160A-160V shown and discussed above with respect to FIGS. 3A, 3B, and 3. The received first detected electronic signals may be associated with a detector identifier. Each detector may have a different light source-detector distance. For example, a probe, such as fetal probes 115A, 115B, 115D, and / or 115E, may have one light source and multiple detectors, each with a different light source-detector distance. In some embodiments, the light signal detected by a detector positioned further away from the light source may have a higher percentage of light incident on the fetus than a detector positioned relatively closer to the light source.

[0099] One exemplary wavelength range for the optical signal corresponding to the first detected electronic signal is between 600 nm and 1000 nm, which may be similar to one or more of the optical signals 420. In some embodiments, the optical signal may be a broadband optical signal (e.g., white light and / or a range of wavelengths, e.g., 10, 15, or 20), and the received first detected signal may correspond to an optical signal of multiple wavelengths. In some embodiments, the optical signal, or a portion thereof, may be at a set or known wavelength, such as 808 nm, that is an isosbestic point for light directed into human tissue to determine the ratio of oxygenated to deoxygenated hemoglobin in human blood. Light of this wavelength is reflected equally from oxygenated and deoxygenated hemoglobin.

[0100] Once step 705 is performed, the first detected electronic signals received in step 705 are processed to isolate a signal portion corresponding to light incident on the fetus (step 710). This isolated portion of each first detected electronic signal is sometimes referred to herein as a first fetal signal. Step 710 may be performed using any suitable method for isolating a fetal signal from a corresponding first detected electronic signal, including methods disclosed herein. Suitable methods include, but are not limited to, reducing noise in the signal, for example, through application of filtering or amplification techniques; determining a portion of the first detected electronic signal contributed by the pregnant mammal and then subtracting or removing that portion of the first detected electronic signal from the received first detected electronic signal; and / or receiving information regarding the fetal heart rate and using that information to lock in (e.g., via a lock-in amplifier) on the portion of the received first detected electronic signal generated by the fetus.

[0101] Optionally, performing step 710 may include preprocessing one or more of the first detected electronic signals, for example, to remove noise from the signals and / or to remove confounding effects of anatomical or physiological signals (e.g., respiratory signals) of the pregnant mammal from the first detected electronic signals. Performing preprocessing may include, but is not limited to, applying filtering techniques to the first detected electronic signals, applying amplification techniques to the first detected electronic signals, utilizing a lock-on amplifier to the first detected electronic signals, etc. In some embodiments, preprocessing may include applying a filter (e.g., bandpass or Kalman) to one or more of the first detected electronic signals to reduce noise or hum in the first detected electronic signals, which may be caused, for example, by electronic noise generated by equipment generating the first detected electronic signals and / or equipment detecting the first detected electronic signals, and / or electronic noise generated by ambient equipment coupled to the pregnant mammal in some cases.

[0102] Optionally, in step 715, an indication of a hemoglobin oxygen saturation level for the pregnant mammal may be received, for example, from a pulse oximetry probe such as pulse oximetry probe 130, a maternal pulse oximetry probe such as maternal probe 133, and / or a NIRS adult hemoglobin probe such as NIRS adult hemoglobin probe 125, and / or may be determined, for example, using the initial detected electrical signal, e.g., using a processor executing process 700. Additionally or alternatively, an indication of a tissue oxygen saturation level of the pregnant mammal may be received and / or determined in step 715. The tissue oxygen saturation level of the pregnant mammal may be received, for example, from a diffuse optical tomography (DOT) instrument and / or may be determined by applying DOT to the initial detected electrical signal. Additionally or alternatively, an indication of hemoglobin oxygen saturation level and / or tissue oxygen saturation level for the pregnant mammal may be determined using one or more of the first detected electronic signals received in step 705, for example, using the Beer-Lambert Law as discussed above with respect to Equation 1.

[0103] In some cases, the hemoglobin oxygen saturation level and / or tissue oxygen saturation level of the pregnant mammal may be used to determine how much light is incident on the fetus, as discussed below.

[0104] In step 720, fetal depth is received, for example, from the Doppler / ultrasound probe 135 and / or determined, for example, using the first detected electronic signal of step 705, the first fetal signal of step 710, and / or the maternal hemoglobin saturation level and / or maternal tissue saturation level of step 715.

[0105] When fetal depth is determined in step 720, fetal depth may be determined by comparing the intensities of the early fetal signals to one another and determining the change in intensity for each early fetal signal. In some cases, the comparison may incorporate the position and / or source / detector distance for each detector providing the corresponding first detected electronic signal, and fetal depth may be determined by quantifying the drop or decrease in fetal signal intensity as the source / detector distance increases for detectors positioned further away from the light source. This decrease in intensity as a function of source / detector distance may be used to determine fetal depth.

[0106] 7B provides a flowchart illustrating one example process for performing step 720 to determine fetal depth. First, in step 750, a first initial detected electronic signal may be analyzed to determine whether it includes an early fetal signal. The first initial detected electronic signal may correspond to an optical signal, such as first optical signal 420A, detected by a first detector, such as first detector 160A. The analysis of step 750 is based on the processing / isolation of step 710 and may include a yes / no determination of whether there is any early fetal signal to be isolated from the first initial detected electronic signal. If the first initial detected electronic signal includes an early fetal signal, the strength of the early fetal signal will be determined (step 755).

[0107] Regardless of whether an early fetal signal is included in the first early detected electronic signal, a determination is made in step 760 as to whether a second early detected electronic signal includes an early fetal signal. The second early detected electronic signal may correspond to an optical signal, such as second optical signal 420B, detected by a second detector, such as second detector 160B. Step 760 may be performed in a manner similar to that of step 750. If an early fetal signal is included in the second early detected electronic signal, the strength of the early fetal signal is determined (step 755).

[0108] Regardless of whether an early fetal signal is included in the second early detected electronic signal, a determination will be made in step 765 as to whether a third early detected electronic signal includes an early fetal signal. The third early detected electronic signal may correspond to an optical signal, such as third optical signal 420C, detected by a third detector, such as third detector 160C. Step 765 may be performed in a manner similar to the performance of steps 750 and / or 760. If an early fetal signal is included in the third early detected electronic signal, the strength of the early fetal signal will be determined (step 755).

[0109] A process such as step 765 may be repeated N times until it is determined whether the last initial detected electronic signal of the plurality of initial detected electronic signals received in step 705 includes an early fetal signal (step 770). The Nth initial detected electronic signal may correspond to an optical signal, such as sixth optical signal 420F, detected by a sixth detector, such as third detector 160F. Step 770 may be performed in a manner similar to the performance of steps 750, 760, and / or 765. If an early fetal signal is included in the Nth initial detected electronic signal, the strength of the early fetal signal will be determined (step 755).

[0110] In step 775, fetal depth is determined by analyzing the determined intensity of each individual early fetal signal determined in step 755. In some embodiments, step 775 may be performed by plotting (e.g., using a scatter plot) intensity on a graph showing fetal signal intensity as a function of the detector detecting each of the first through Nth fetal signals and / or the fetal signal as a function of the distance between the light source generating the light signal and the detector detecting each of the first through Nth early detected electronic signals. Figure 7C provides an example of a graph 702 showing a scatter plot of light intensity (watts / cm) of the first through Nth fetal signals as a function of light source / detector distance (cm), which may be determined by performing step 755. In Figure 7C, graph 702 corresponds to the early detected electronic signals detected by detectors 1 through 6 160A-160F and the distance of each detector from light source 105. As can be seen in graph 702, the change in percent light transmission for a signal detected with distance from the light source, sometimes related to the strength of the signal, follows a predominantly inverse proportional relationship. The change in percent light transmission and / or light intensity incident on the fetus may vary nonlinearly depending on fetal depth and / or source-detector distance as shown in graph 702 of FIG. 7C. In some embodiments, the change in light intensity and / or percent light transmission reaching the fetus may also depend inversely on fetal depth as shown in FIG. 7D, which includes graph 703 showing the change in percent light transmission as a function of source-detector distance measured in cm for the maternal signal and / or maternal portion of the signal.

[0111] Because the first fetal signal is detected by a third detector with a source-to-detector distance of 3 cm, an example fetal depth may be approximately 25 mm. Fetal depth may be determined using the rate of decay of fetal signal intensity with increasing source-to-detector distance. This rate of decay may correspond to the slope of the linear regression of the scatter plot.

[0112] In some embodiments, fetal depth may be determined by analyzing light at the 808 nm isosbestic point. Light at this wavelength is reflected in the same manner from oxygenated and deoxygenated hemoglobin, and therefore the scattering and absorption of light at this wavelength should be the same for both oxygenated and deoxygenated hemoglobin and should not change based on, for example, the hemoglobin oxygen saturation level of the pregnant mammal's blood and / or the fetal blood. Therefore, when performing step 720 using light at the 808 nm isosbestic point, it may not be necessary to determine the scattering and / or absorption of the optical signal by maternal tissue (sometimes referred to as the scattering coefficient and / or absorption coefficient, respectively).

[0113] In step 725, a second detected electronic signal corresponding to the second optical signal is received. The second detected electronic signal corresponds to a second optical signal exiting the abdomen of the pregnant mammal and may be similar to the first detected electronic signal received in step 705. The second detected electronic signal is then processed to isolate the portion of the signal incident on the fetus (step 730). The isolated portion of the second detected electronic signal may also be referred to herein as the fetal signal. In some embodiments, performance of step 730 may be similar to performance of step 710.

[0114] The fetal depth is used to select coefficients for analyzing the second fetal signal to determine a fetal hemoglobin oxygen saturation level in step 735. For example, the fetal depth may be used to determine and / or select a differential path length factor (DFP) and / or a correlation factor for a particular wavelength for use in calculations to determine a hemoglobin oxygen saturation level for the fetus (step 740), e.g., using the modified Beer-Lambert law presented above as Equation 1 for each wavelength.

[0115] The fetal depth would then be used to determine and / or select the DFP for a particular wavelength. The value of I for each wavelength of light in the incident fetal light signal can be, for example, the intensity of light projected into the abdomen of the pregnant mammal and / or the intensity of light incident on the fetus, which can be determined via the processes disclosed herein. In embodiments in which a hemoglobin oxygen saturation level and / or tissue oxygen saturation level of the pregnant mammal is received and / or determined in step 715, the hemoglobin oxygen saturation level and / or tissue oxygen saturation level may be used to determine the intensity of the light or how much of the light emitted by the light source directed into the abdomen of the pregnant mammal is absorbed by maternal tissue or hemoglobin. Correlations between the hemoglobin oxygen saturation level and / or tissue oxygen saturation level of the pregnant mammal and how much of the incident light she may absorb for each wavelength of light may be known and / or empirically determined, and these correlations may be stored in a look-up table in a database, such as database 170, so that when the hemoglobin oxygen saturation level and / or tissue oxygen saturation level for the pregnant mammal is received and / or determined in step 715, the table may be used to look up the corresponding level of light absorption (e.g., a percentage or ratio) for the pregnant mammal. This value (level of light absorption for the pregnant mammal) may then be applied (e.g., subtracted or multiplied) to the initial intensity of the light source when it attempts to project light into the abdomen of the pregnant mammal to determine the initial intensity of light (I) incident on the fetus. ΔI(λ) is the change in the measured intensity of light (I) incident on the fetus at wavelength λ, which may be the change in the intensity of the detected fetal signal for light of wavelength λ.

[0116] Once the absorption coefficient (or change in absorption coefficient) is determined via Equation 1, an indication of fetal hemoglobin oxygen saturation may be determined, for example, via calculation using Equation 2 provided below.

number

[0117] Equation 1 can be solved by inputting the change in intensity I as a function of wavelength λ for two or more wavelength pairs. From this, Equation 2 can be used to calculate the known extinction coefficient ε for a particular wavelength, which can be looked up, for example, in a look-up table stored, for example, on computer 150. HbO (λ) and ε Hb (λ) to change the absorption coefficient Δμ a The wavelength pair used to perform the calculation of Equation 2 can be any wavelength pair within the spectrum of wavelengths of the optical signal incident on the abdomen of the pregnant mammal. In some embodiments, ΔC HbO and ΔC Hb The calculation of Equation 2 is performed multiple times (e.g., 10, 100, or 1000 times) at different combinations of wavelengths to arrive at multiple values for ΔC HbO and ΔC Hb The calculated values may be weighted and / or averaged according to one or more criteria to arrive at a robust value (e.g., statistically valid and / or with an acceptable level of confidence and error rate) as . Additionally or alternatively, the calculation of Equation 2 may be performed multiple times (e.g., 10, 100, or 1000 times) to fit multiple wavelengths to the equation simultaneously.

[0118] ΔC generated via Equation 2 HbO and ΔC Hb The value of σ is a relative, not absolute, value for the concentrations of oxygenated and deoxygenated hemoglobin in fetal blood, which may be useful for monitoring changes in the fetal hemoglobin oxygen saturation level over time. In some embodiments, the determining of step 1235 may further include determining the overall oxygen saturation for fetal hemoglobin by determining the ratio of the change in oxygenated hemoglobin concentration to the change in total hemoglobin concentration, which is the sum of oxygenated and deoxygenated hemoglobin. Additionally or alternatively, fetal hemoglobin oxygen saturation may be determined using another method as may be disclosed herein.

[0119] Once the fetal hemoglobin oxygen saturation level is determined in step 740, providing an indication of the fetal hemoglobin oxygen saturation level to the user may be facilitated by, for example, display on a display device such as display device 155 (step 745).

[0120] 8 is a flowchart illustrating a process 800 for determining the time of flight for photons incident on a fetus and / or the oxygen saturation level for fetal hemoglobin. Process 800 may be performed, for example, by system 100 and / or its components.

[0121] Optionally, in step 805, a plurality of first detected electronic signals, each corresponding to an optical signal of one or more wavelengths projected into the abdomen of the pregnant mammal by one or more light sources, such as light source 105, and emerging therefrom, e.g., via reflection, backscattering, and / or transmission (i.e., through the maternal abdomen), are received by a computer or processor, such as computer 150. The first detected electronic signals received in step 805 may be similar to the first detected electronic signals received in step 705. In some embodiments, the time from when the optical signal is projected into the abdomen of the pregnant mammal to when the optical signal is received by the detector may be received in step 805. Additionally or alternatively, the plurality of detected electronic signals may include timestamp information corresponding, for example, to when the optical signal is projected into the abdomen of the pregnant mammal and / or when the first detected electronic signal is received by the respective detector.

[0122] Once step 805 has been performed, each of the first detected electronic signals received in step 805 will be processed to isolate the portion of the signal corresponding to the light incident on the fetus (step 810). Performance of step 810 may be similar to performance of step 710.

[0123] In step 815, an indication of the time of flight for a photon of the optical signal incident on the fetus may be received and / or may be determined using the time from when the photon of the optical signal leaves the light source to when it is received by the detector when steps 805 and 810 are performed. The time of flight may be determined by calculating the length from when the optical signal is projected into the abdomen of the pregnant mammal to when it is received by the detector. If the plurality of first detected electronic signals include timestamp information corresponding to when the optical signal is projected into the abdomen of the pregnant mammal and when the first detected electronic signals are received by the respective detectors, determining the time of flight for the photon of the optical signal incident on the fetus may be made by determining the difference or length of time between the timestamp for when the optical signal is projected into the abdomen of the pregnant mammal and the timestamp for when the first detected electronic signals are received by the respective detectors.

[0124] In step 820, fetal depth is received, for example, from Doppler / ultrasound probe 135 and / or determined, for example, using the first detected electronic signal of step 805, the first fetal signal of step 810, and / or the time of flight of step 815. When fetal depth is determined in step 820, the fetal depth may be determined by calculating the distance traveled by the optical signal during the time from when the optical signal is projected into the abdomen of the pregnant mammal to when it is received by the detector, according to Equation 3 below. D=s*t Equation 3 Here, D = distance traveled; s = speed of light; and t = the time from when the light signal is projected into the abdomen of the pregnant mammal to when it is received by the detector. Since the distance calculated via Equation 3 is the distance the light travels to the fetus and back to the detector, the fetus distance can be calculated by dividing the value of the distance traveled by the light (D) by two.

[0125] In step 825, a second detected electronic signal corresponding to the second optical signal is received. The second detected electronic signal corresponds to a second optical signal exiting the abdomen of the pregnant mammal and may be similar to the first detected electronic signal received in step 805. The second detected electronic signal is then processed to isolate the portion of the signal incident on the fetus (step 830). The isolated portion of the second detected electronic signal may also be referred to herein as a second fetal signal. In some embodiments, performance of step 830 may be similar to performance of step 810 and / or step 730.

[0126] In step 835, the fetal depth is used to select coefficients for analyzing the second detected electronic signal to determine the fetal hemoglobin oxygen saturation level. For example, the fetal depth may be used to determine and / or select a differential path length factor (DFP) and / or correlation coefficient for a particular wavelength for use in calculations to determine the hemoglobin oxygen saturation level for the fetus (step 840), e.g., using Equation 1 and Equation 2 provided and discussed above. In some embodiments, performance of step 835 may be similar to performance of step 735. Additionally or alternatively, fetal hemoglobin oxygen saturation may be determined using another method as may be disclosed herein.

[0127] Once the fetal hemoglobin oxygen saturation level is determined in step 840, providing an indication of the fetal hemoglobin oxygen saturation level to the user may be facilitated by, for example, display on a display device such as display device 155 (step 845).

[0128] 9 provides a flowchart illustrating a process 900 for determining a fetal hemoglobin oxygen saturation level using physiological characteristics of a pregnant mammal determined using a maternal detected electronic signal. Process 900 may be performed, for example, by system 100 and / or its components. Process 900 may be performed in situ, for example, during labor or fetal delivery and / or during a medical examination for the pregnant mammal. In some cases, process 900 may be performed continuously, periodically, and / or as needed over a period of time, such as labor and fetal delivery, so that, for example, the fetal hemoglobin oxygen saturation level may be calibrated and recalibrated as needed over time and / or when conditions for the fetus and / or the pregnant mammal change, such as when the fetus is progressing through the birth canal.

[0129] In step 925, a detected composite electronic signal is received from a detector by a processor and / or a computer, such as computer 150. The detected composite electronic signal may be received, for example, from a photodetector, a transceiver coupled to a photodetector, and / or a fetal hemoglobin probe, such as fetal hemoglobin probe 115. The detected composite electronic signal may correspond to an optical signal emitted from the pregnant mammal's abdomen and / or her fetus. The light entering and exiting the pregnant mammal's abdomen may be generated by one or more light sources, such as light source 105, and may be of any acceptable frequency or wavelength (e.g., near-infrared (NIR)) and / or combination of frequencies and / or wavelengths. In some embodiments, step 925 may further include receiving an indication of whether the fetal hemoglobin oxygen saturation level is pre-ductal or post-ductal, for example, in a manner similar to receiving an indication of whether the fetal hemoglobin oxygen saturation level is pre-ductal or post-ductal in step 1305. Step 925 may be performed at any time following the performance of step 920. However, in many cases, step 925 will be performed immediately or shortly (e.g., 5 seconds, 30 seconds, 1 minute) after the performance of step 920, taking into account dynamic changes to abdominal physiological characteristics of, for example, a pregnant mammal.

[0130] The received detected composite electronic signal is then analyzed to isolate the signal portion corresponding to the light incident on the fetus, thereby generating a fetal signal (step 930). Step 930 may be performed, for example, in a manner similar to steps 810, 710, or any other method implementation disclosed herein. The calibration coefficient selected and / or determined in step 920 is then applied to the fetal signal to calibrate the fetal signal (step 935). Once the fetal signal is calibrated, an indication of the fetal hemoglobin oxygen saturation level is determined (step 940) and provided to the user (step 945). Optionally, execution of step 945 may include indicating to the user whether the fetal hemoglobin oxygen saturation level is pre-ductal or post-ductal in a manner similar to execution of step 1355. Execution of steps 935-945 may be similar to execution of steps 1345-1350 and / or steps 830-835 disclosed below. Additionally or alternatively, fetal hemoglobin oxygen saturation may be determined using another method that may be disclosed herein.

[0131] 10 provides a flowchart illustrating a process 1000 for determining fetal hemoglobin oxygen saturation levels using physiological characteristics of a pregnant mammal determined using one or more maternal detected electronic signals. Process 1000 may be used to account for changes in the geometry and / or physiological characteristics of the mother across the surface area of a fetal hemoglobin probe, such as fetal hemoglobin probe 115. Process 1000 may be performed, for example, by system 100 and / or its components. Process 1000 may be performed in situ, for example, during labor or delivery of the fetus and / or during a medical examination for the pregnant mammal. In some cases, process 1000 may be performed continuously, periodically, and / or as needed over a time period such as labor and fetal delivery (e.g., 1 hour to 24 hours), so that, for example, fetal hemoglobin oxygen saturation levels may be calibrated and recalibrated as needed over time and / or as conditions for the fetus and / or pregnant mammal change, such as when the fetus is progressing through the birth canal.

[0132] Initially, in step 1005, one or more maternal detected electronic signals corresponding to one or more optical signals emitted from the abdomen of the pregnant mammal are received (step 1005). The maternal detected electronic signals are generated by a light source, such as light source 105, impinge on the abdomen of the pregnant mammal, pass through a portion of the maternal abdominal tissue, and are reflected or backscattered through the maternal tissue where they are detected by a detector, such as detector 160. Each optical signal may be associated with a location and / or an identifier of each detector that detected the respective optical signal. For example, each detector that detects a maternal detected electronic signal may be associated with an identifier (e.g., detector 1, detector 2, etc.), a location that may be the detector's location (e.g., coordinates) on the fetal hemoglobin probe 115, and / or a location on the maternal abdomen (e.g., 1 inch (2.54 cm) below the umbilicus, 1 inch (2.54 cm) below the umbilicus and 1 inch (2.54 cm) left of the midsagittal line, etc.). Exemplary optical signals, such as those that may be detected by the detectors and received in step 1005, are shown, for example, in FIG. 3C as first optical signal 420A and second optical signal 420B and in FIGS. 4A-4B as optical signal 420.

[0133] In step 1010, each of the maternal detected electronic signals will be analyzed to determine one or more extrinsic or geometric physiological characteristics of the pregnant mammal (step 1015). Exemplary extrinsic physiological characteristics include, but are not limited to, the melanin content and / or degree and / or type of skin pigmentation of the pregnant mammal, the width of one or more layers of maternal or fetal tissue, and abdominal wall thickness for the pregnant mammal. Exemplary dimensions for the abdominal wall and / or thicknesses of abdominal wall layers of the pregnant mammal are provided above with respect to Figures 3A and 3B.

[0134] In step 1020, a calibration coefficient is selected and / or determined for each maternal detected electronic signal. The determination (i.e., calculation) and / or selection of the calibration coefficient may be performed, for example, by assessing how much light from the incident optical signal is absorbed and / or scattered by the abdominal tissue of the pregnant mammal and / or by assessing the time of flight for photons of the optical signal to travel through the abdominal tissue of the pregnant mammal and be detected by a detector. In some embodiments, the selection of the calibration coefficient may be accomplished by querying a database, such as database 170, and / or memory resident within a computer, such as computer 150, for a calibration coefficient corresponding to the physiological characteristic determined in step 915. The database may be populated with the physiological characteristics and calibration coefficients correlated via process 500. In some embodiments, the results of performing steps 1005, 1010, 1015, and / or 1020 may be stored, for example, in a database, such as database 170, and / or memory resident within a computer, such as computer 150.

[0135] In step 1025, a physiological characteristic and / or a calibration factor may be associated with the detector that detected each individual maternal detected electronic signal received in step 1005. Additionally or alternatively, in step 1025, the physiological characteristic and / or calibration factor may be associated with a location on the abdomen of the pregnant mammal.

[0136] In one embodiment, the set of results from performing steps 1005-1025 is provided by the values in Table 1 below, which provides a detector identifier, a value for the physiological characteristic of abdominal thickness, and a calibration factor corresponding to the physiological characteristic of abdominal thickness. [Table 1]

[0137] In step 1030, one or more detected composite electronic signals are received by a processor and / or computer, such as computer 150. The one or more detected composite electronic signals may be received from the detector(s) that provided the maternal detected electronic signal received in step 1005, and each of the detected composite electronic signal(s) may be associated with a location and / or an identifier for the detector that detected each respective detected composite electronic signal. In some embodiments, step 1030 may further include receiving an indication of whether the fetal hemoglobin oxygen saturation level is pre-ductal or post-ductal, e.g., in a manner similar to receiving an indication of whether the fetal hemoglobin oxygen saturation level is pre-ductal or post-ductal in step 1305.

[0138] The detected composite electronic signal may be received, for example, from a photodetector, a transceiver coupled to a photodetector, and / or a fetal hemoglobin probe, such as fetal hemoglobin probe 115. The detected composite electronic signal may correspond to an optical signal emitted from the pregnant mammal's abdomen and / or her fetus. The light entering and exiting the pregnant mammal's abdomen can be generated by one or more light sources, such as light source 105, and may be of any acceptable frequency or wavelength (e.g., near-infrared (NIR)) and / or combination of frequencies and / or wavelengths. Step 1030 may be performed at any time following the performance of step 1025. However, in many cases, step 1030 will be performed immediately or shortly thereafter (e.g., 5 seconds, 30 seconds, 1 minute, 1 hour) after the performance of step 1025, for example, to account for dynamic changes to the physiological characteristics of the pregnant mammal's abdomen.

[0139] The received detected composite electronic signal(s) would then be analyzed to isolate portions of each individual composite electronic signal corresponding to light incident on the fetus, thereby generating a corresponding number of fetal signals (step 1035). Step 1035 may be performed in a manner similar to the performance of steps 710 and / or 810, and / or according to other method(s) disclosed herein. A calibration factor correlated to the detector that detected each individual detected composite electronic signal would then be applied to the fetal signal corresponding to each individual detected composite electronic signal (step 1040). Performance of step 1040 may be similar to the performance of step 935 discussed above.

[0140] Continuing with the above embodiment, in step 1040, the application of calibration coefficients to the fetal signals received from the first, second, and third detectors corresponds to the first, second, and third fetal signals (i.e., fetal signal 1, fetal signal 2, and fetal signal 3), respectively, corresponding to calibration coefficients P1, P2, and P3 as shown in Table 2 below, and the calibration coefficients for the detectors, first, second, and third physiological characteristics correspond to the calibration coefficients for the first, second, and third fetal signals, respectively, shown in Table 2. [Table 2]

[0141] In some embodiments, the fetal signals and / or fetal signal 1, fetal signal 2, and / or fetal signal 3 disclosed herein may be signals including multiple wavelengths of light, and calibration factors for each of these wavelengths may be determined and / or applied separately for each individual wavelength (or group of similar wavelengths) included in each fetal signal. Additionally or alternatively, the fetal signals and / or fetal signal 1, fetal signal 2, and / or fetal signal 3 disclosed herein may each be detected by a separate detector and / or may be detected by the same detector at different times. For example, a fetal pulse may be extracted from multiple fetal signals (each of which may be detected by a separate detector), and the calibration of the fetal signal(s) may be affected differently in each detector channel by different proportions of different physiological properties, governed by the following relationship: For detector 1, signal = function D1 (D1, P1, P2, P3...), where D1 is a vector of coefficients related to detector 1 geometry, wavelength, etc., P1 is a vector related to physical property P1, P2 is a vector related to physical property P2, etc. In this example, function D1 may be thought of as a tensor.

[0142] Once each of the fetal signals has been calibrated, an indication of the fetal hemoglobin oxygen saturation level is determined (step 1045), for example, using one or more of the methods disclosed herein. In some cases, step 1050 may be performed by individually determining the fetal hemoglobin oxygen saturation level for each fetal signal and averaging the individually determined fetal hemoglobin oxygen saturation levels to arrive at an average fetal hemoglobin oxygen saturation level. Additionally or alternatively, each of the fetal signals may be a mixture or combination of different signals resulting from various concurrent physical characteristics, and in some cases, each calibration coefficient C1, C2, etc. may be a vector, which for a family of detector signals may be a tensor matrix.

[0143] Once the fetal hemoglobin oxygen saturation level is determined, the fetal hemoglobin oxygen saturation level will be provided to the user (step 1050). Optionally, performance of step 1050 may include instructing the user whether the fetal hemoglobin oxygen saturation level is pre-ductal or post-ductal, in a manner similar to performance of step 1355. In some embodiments, performance of steps 1045 and 1050 may be similar to performance of steps 1345-1350, steps 830-835, and / or steps 940 and 945.

[0144] 11 provides a flowchart illustrating a process 1100 for determining the effect of physiological characteristics on the behavior (e.g., scattering, absorption, etc.) of light traversing through the abdomen of a pregnant mammal and / or her fetus. Process 1100 may be performed by component combinations of system 100 and / or its components. Exemplary physiological characteristics include, but are not limited to, how many tissue layers are irradiated with light, skin pigmentation, density of the tissue or tissue layer, depth of the fetus within the maternal abdomen, composition of the tissue or tissue layer, etc.

[0145] In step 1105, physiological characteristics of the pregnant mammal and / or her fetus are received. In some cases, the physiological characteristics may be determined, for example, through analyzing images of the pregnant mammal and / or her fetus. The images may be generated by one or more imaging techniques, including, but not limited to, MRI or ultrasound imaging techniques. Exemplary image illustrations that may be analyzed to determine one or more physiological characteristics include those of FIGS. 3A and 3B. Additionally or alternatively, the physiological characteristics may not be image-based, such as, for example, body mass index, skin pigmentation, age, etc.

[0146] In step 1110, it is determined how physiological characteristics affect the behavior of light directed and / or passing into the maternal abdomen and / or fetus. The light directed and / or passing into the maternal abdomen and / or fetus may be of a single wavelength or multiple (e.g., broad or narrow) wavelengths, and the determination may be based on and / or take into account one or more wavelengths of interest. In general, the behavior of light (e.g., scattering) depends on tissue morphology and particle size / density of materials (e.g., water, lipids, etc.) within the tissue. Different tissue layers typically have different morphologies, particle sizes, and / or particle densities. For example, if the physical property of a tissue layer is a higher than average amount of fat in the tissue (i.e., a high lipid count), one might expect the amount of light scattering to be higher than average due to the higher than average lipid count. In some embodiments, this effect can be measured using a scattering coefficient (e.g., μ s (λ)), absorption coefficient (e.g., μ a (λ)), adjustments to scattering coefficients, and / or adjustments to absorption coefficients, which can be input into equations relating to and / or incorporating the behavior of light as it passes through a medium or media, such as the Beer-Lambert law and / or modified Beer-Lambert law.

[0147] The determination of step 1110 may be made, for example, using experimental observations collected from one or more pregnant mammals and / or mathematical modeling performed on a plurality of theoretical pregnant mammals and / or theoretically modeled physiological characteristics. For example, experimental observations may be used to correlate physiological characteristics of the pregnant mammal / mammal abdomen with observed light signal behavior that may be detected as it emanates from the abdomen of the pregnant mammal under study (e.g., via reflection, backscattering, and / or absorption). Additionally or alternatively, the detected light scattering and / or detected light signals for a population of pregnant mammals may be analyzed to determine how various physiological characteristics of the pregnant mammals in the population may affect light scattering. For example, the light scattering and / or detected light signals may be analyzed along with physiological characteristics such as the thickness of the subcutaneous fat layer for each pregnant mammal in the population to determine whether the thickness of the subcutaneous fat layer affects the behavior of the detected light, and if so, how and to what extent the light behavior is affected. This process may be repeated, for example, with multiple physiological characteristics of pregnant mammals in the population, or with multiple tissue layers of the pregnant mammal for each pregnant mammal in the population, either singly (i.e., one at a time) and / or in combination (i.e., to determine how multiple physiological characteristics may affect the behavior of the light). In some embodiments, the determination of step 1110 may depend on the frequency / wavelength of the light being observed or measured. In some cases, the determination of step 1110 may take into account how different intrinsic and / or tissue and geometric characteristics of the pregnant mammal and / or fetus may affect different wavelengths. For example, a particular physiological characteristic may affect the behavior of light at a first wavelength (e.g., 700 nm) differently than it may affect light at a second wavelength (e.g., 800 nm), e.g., scattering and / or absorption of light at the first wavelength may be greater / less than light at the second wavelength. Thus, the influence of the physiological characteristic may be determined for different frequencies / wavelengths of light and / or for different frequency / wavelength ranges.

[0148] Additionally or alternatively, when step 1110 is performed using mathematical modeling, one or more known, understood, estimated, and / or assumed ways in which light may behave as it passes through a material and / or multiple materials (e.g., skin, fat, muscle, etc.) may be mathematically modeled from a physiological perspective, such as through the abdomen of a pregnant mammal, using one or more known, understood, estimated, and / or assumed ways in which light may behave as it passes through a material (e.g., skin, water, water with a known lipid count, skeletal muscle, fat, smooth muscle, water with a known electrolyte count, etc.). Exemplary programs that may be used to perform mathematical modeling include, but are not limited to, NIRFAST for Monte Carlo simulation and finite element modeling.

[0149] In one example, the physiological characteristic received in step 1105 may be skin pigmentation, pigmentation, and / or melanin content input by a clinician or physician. In some embodiments, skin pigmentation may be quantified by a clinician using the Fitzpatrick scale and input to a processor or computer that performs step 1110. In step 1110, it will be determined how the quantified skin pigment of the pregnant mammal affects the behavior of light that enters the pregnant mammal's abdomen and / or exits her skin. The skin pigment of the pregnant mammal's skin may affect how much of the incident light is absorbed, which will affect how much of the light that enters the pregnant mammal's abdomen travels through maternal tissue and enters the fetus, according to a known or calculated factor determined in step 1110.

[0150] In another example, the physiological characteristic received in step 1105 may be the density, concentration, and / or thickness of the myoglobin or muscle layer (sometimes collectively referred to herein as myoglobin concentration) of the abdomen of the pregnant mammal. The myoglobin tissue of the pregnant mammal can absorb light projected into the maternal abdomen, and a measurement of how dense the myoglobin layer is may be used to determine how much light is absorbed (e.g., undetected) by the myoglobin tissue of the pregnant mammal. In step 620, this physiological characteristic may be used, for example, to calculate a calibration factor and / or to query a database of calibration factors to find a calibration factor associated with the physiological characteristic of myoglobin concentration determined for the pregnant mammal.

[0151] In another example, the physiological characteristic received in step 1105 may be the overall thickness of the pregnant mammal's abdomen (sometimes referred to herein as fetal depth), which may change due to the increasing size of the fetus over the course of pregnancy. In some cases, the thickness of the pregnant mammal's abdomen may be determined, for example, through a body mass index (BMI) calculation, analysis of images, example illustrations of which are shown in diagrams 301 and 302, and / or analysis of ultrasound images. Additionally or alternatively, the thickness of the pregnant mammal's abdominal tissue may change over the course of pregnancy and / or during labor and delivery of the fetus due to preeclampsia or eclampsia. The pregnant mammal's abdominal tissue can absorb light projected into the maternal abdomen, and measurements and / or calculations of how much light is absorbed (e.g., undetected) by the pregnant mammal's abdominal tissue may be used to determine the physiological characteristic of how thick the pregnant mammal's abdominal tissue is. In step 1115, this physiological characteristic may be used, for example, to calculate a calibration factor and / or may be used to query a database of calibration factors to find a calibration factor associated with the physiological characteristic of abdominal thickness determined for the pregnant mammal.

[0152] In yet another embodiment, the physiological characteristic received in step 1105 may be the thickness of the adipose layer or fat layer in the abdomen of the pregnant mammal. The adipose tissue of the pregnant mammal can scatter light projected into the maternal abdomen, and measurements and / or calculations of how thick the adipose layer is may be used to determine how much light the adipose layer scatters. In step 1115, this physiological characteristic may be used, for example, to calculate a calibration factor and / or to query a database of calibration factors to find a calibration factor associated with the determined physiological characteristic of adipose thickness for the pregnant mammal.

[0153] In different embodiments, the physiological characteristic received in step 1105 may be the amount of hemoglobin circulating in the blood of the pregnant mammal (i.e., hemoglobin concentration). The amount of hemoglobin circulating in the blood of the pregnant mammal may be determined via a blood measurement, such as a hemoglobin concentration measurement, a hematocrit measurement, and / or a total blood volume measurement, to quantify maternal hemoglobin concentration. In some cases, the hemoglobin concentration measurement may be measured using a device, such as a Masimo SpHb device, configured to non-invasively measure hemoglobin concentration.

[0154] Anemia is a condition that causes a decrease in the hemoglobin concentration in the blood of a pregnant mammal, while conditions such as polycythemia vera cause an increase in the hemoglobin concentration in the blood of a pregnant mammal. The hemoglobin concentration in the blood of a pregnant mammal can absorb light projected into the maternal abdomen, and a value for the hemoglobin concentration in the blood of a pregnant mammal can be used to determine how much light the maternal hemoglobin absorbs, where the blood of an anemic pregnant mammal will not absorb as much light as a pregnant mammal with a normal value for hemoglobin concentration, which will affect how much light enters the fetus. Similarly, the increased hemoglobin concentration of a pregnant mammal with polycythemia vera may absorb more light than a pregnant mammal with a normal value for hemoglobin concentration, which will affect how much light enters the fetus. In step 1115, this physiological characteristic may be used, for example, to calculate a calibration factor and / or may be used to query a database of calibration factors to find a calibration factor associated with the physiological characteristic of adipose thickness determined for the pregnant mammal.

[0155] In another embodiment, the physiological characteristic received in step 1105 may be a hemoglobin oxygen saturation measurement of the pregnant mammal, which may be measured, for example, by analysis of a direct arterial blood sample, estimated using a venous blood sample, or measured using a pulse oximeter such as pulse oximeter 130 and / or a NIRS adult hemoglobin probe such as a NIRS adult hemoglobin probe. Pneumonia, asthma, COVID-19, cardiovascular conditions that can affect oxygen saturation, and high altitude can all cause a drop in maternal hemoglobin oxygen saturation. The hemoglobin oxygen saturation in the blood of the pregnant mammal determines how much light is absorbed by oxygenated and / or deoxygenated hemoglobin, and a value for the hemoglobin oxygen saturation of the blood of the pregnant mammal may be used to determine how much light is absorbed by the mother's oxygenated / deoxygenated hemoglobin, which affects how much light enters the fetus.

[0156] In step 1120, the determined effect(s) of one or more physiological characteristics and / or combination(s) of physiological characteristics on the behavior of the light are stored in a database, such as database 170. Sometimes, the physiological characteristics may be indexed within the database to a corresponding determination of the effect of the physiological characteristic on the light or specific wavelengths of light. For example, a physiological characteristic that is static over a period of time (e.g., anemia, hypertension, respiratory disease, and / or naturally low blood oxygen levels for a pregnant mammal) may be indexed and / or correlated to a corresponding determination (e.g., a calibration coefficient) of the effect of the physiological characteristic on the light / or specific wavelengths of light.

[0157] 12 is a flowchart illustrating an example process 1200 for determining fetal hemoglobin oxygen saturation levels using maternal hemoglobin oxygen saturation levels and / or fetal depth indications. Process 1200 may be performed, for example, by system 100 and / or its components.

[0158] In step 1205, an indication of a hemoglobin oxygen saturation level for the pregnant mammal may be received, e.g., from a pulse oximetry probe, such as pulse oximetry probe 130, a maternal pulse oximetry probe, such as maternal probe 133, and / or a NIRS adult hemoglobin probe, such as a NIRS adult hemoglobin probe, and / or may be determined, e.g., using the first detected electronic signal, e.g., using a processor executing process 1200. Additionally or alternatively, an indication of a tissue oxygen saturation level for the pregnant mammal may be received and / or determined in step 715. The tissue oxygen saturation level of the pregnant mammal may be received, e.g., from a diffuse optical tomography (DOT) instrument and / or determined by applying DOT to the first detected electronic signal. In some embodiments, performance of step 1205 may be similar to performance of step 715.

[0159] In step 1210, an intensity value for the light signal incident on the abdomen of the pregnant mammal is received. This intensity value may be known, for example, from the manufacturer of the light source used to generate the light signal, and / or may be determined experimentally. In step 1215, the portion of the incident light signal that is absorbed by the pregnant mammal and therefore does not impinge on the fetus, and / or how much of the incident signal may impinge on the fetus, is determined and / or received. The portion of the incident light signal that may impinge on the fetus is sometimes referred to herein as the incident fetal light signal. Step 1215 determines the light absorption rate (e.g., Δμ) of the pregnant mammal based on the hemoglobin oxygenation level and / or tissue oxygenation level of the pregnant mammal received in step 1205. a In some embodiments, the determination of step 1215 may be similar to performing step 720.

[0160] In step 1220, a detected electronic signal is received from a photodetector, such as detector 160. The detected electronic signal may correspond to an optical signal of one or more wavelengths incident on and emanating from the abdomen of the pregnant mammal and her fetus and detected by the detector over a period of time. Detecting the optical signal may include counting photons of different wavelengths received by the detector and / or incident on an optical fiber coupled to the detector. Optionally, the received detected electronic signal may resemble the detected electronic signal received in steps 705 and / or 725 of process 700 and / or steps 805 and / or 825 of process 800, discussed above.

[0161] Optionally, in some embodiments, fetal depth (e.g., the distance between the abdominal skin of the pregnant mammal and the skin of the fetus) may be received and / or determined (step 1225). Fetal depth may be received, for example, from a Doppler / ultrasound probe, such as Doppler / ultrasound probe 135, and / or a fetal depth probe, such as fetal depth probe 138. Fetal depth may be determined, for example, via execution of process 700 and / or process 800, described above with respect to FIGS. 7 and 8, respectively. Once fetal depth is received and / or determined in step 1225, the fetal depth may be used to determine and / or select a calibration coefficient and / or a differential path length factor (DPF) for one or more wavelengths of light included in the fetal signal and / or the incident optical signal.

[0162] In step 1230, the portion of the detected electronic signal of step 1220 that was incident on the fetus is isolated from the detected electronic signal, for example, according to one or more methods disclosed herein. This isolated portion of the received detected electronic signal is sometimes referred to herein as the fetal signal. Step 1230 may be performed using any suitable method of isolating the fetal signal from the detected electronic signal. Suitable methods include, but are not limited to, reducing noise in the signal, for example, through application of filtering or amplification techniques, determining the portion of the detected electronic signal contributed by the pregnant mammal and then subtracting or removing that portion of the detected electronic signal from the received detected electronic signal, and / or receiving information about the fetal heart rate and using that information to lock in (e.g., via a lock-in amplifier) on the portion of the received detected electronic signal produced by the fetus.

[0163] In step 1235, the fetal signal is analyzed to determine a fetal hemoglobin oxygen saturation level, e.g., using Equation 1 and Equation 2 described above and / or one or more of the methods disclosed herein. In some embodiments, performance of step 1235 may be similar to performance of step 740 of process 700 and / or step 840 of process 800, respectively. Once the fetal hemoglobin oxygen saturation level is determined in step 1235, providing an indication of the fetal hemoglobin oxygen saturation level to the user may be facilitated by display on a display device, such as display device 155.

[0164] 13 is a flowchart illustrating a process 1300 for determining fetal hemoglobin oxygen saturation levels using calibration factors and / or physiological characteristics of the pregnant mammal and / or fetus. Process 1300 may be performed, for example, by system 100 and / or its components.

[0165] Initially, a detected composite electronic signal is received from a photodetector (e.g., detector 160) by a processor and / or computer, such as computer 150 (step 1305). The detected composite electronic signal may be received, for example, from a photodetector, a transceiver coupled to the photodetector, and / or a fetal hemoglobin probe, such as fetal hemoglobin probe 115. The detected composite electronic signal may correspond to an optical signal emitted from the abdomen of the pregnant mammal and / or the fetus. The light incident on and exiting the abdomen of the pregnant mammal can be generated by one or more light sources, such as light source 105, and may be of any acceptable frequency or wavelength (e.g., near-infrared (NIR)) and / or combination of frequencies and / or wavelengths. In some embodiments (e.g., when multiple detectors are used), the received detected composite electronic signal may include and / or be associated with a detector identifier so that the location of the particular detected composite electronic signal can be known. This location may then be used to analyze the detected composite electronic signal to determine various coefficients of the detected light and / or imaged tissue.

[0166] In some embodiments, an indication of whether the fetal hemoglobin oxygen saturation level is preductal or postductal may also be received in step 1305. This indication may, in some cases, be an indication of where on the fetus the light signal is being reflected, with a measurement from the fetal head indicating a preductal measurement (i.e., a higher fetal oxygen saturation level) and a measurement from the fetal torso (e.g., back, buttocks) indicating a postductal measurement where a lower oxygen saturation level is expected. The indication of where on the fetus the measurement is being reflected may be provided by a user who enters this information following, for example, examination of an image, such as an ultrasound or MRI image, of the pregnant mammal's abdomen.

[0167] Optionally, information regarding the fetus and / or the pregnant mammal may be received (step 1310). Exemplary information includes, but is not limited to, fetal heart rate, fetal ECG signal, maternal heart rate, maternal ECG signal, uterine contraction information for the pregnant mammal, maternal hemoglobin oxygen saturation, and / or maternal respiratory signal.

[0168] The received detected composite electronic signal is then analyzed to isolate a signal portion corresponding to light incident on the fetus, thereby generating a fetal signal (step 1315). Step 1315 may be performed using any suitable method of isolating the fetal signal from the received detected composite electronic signal. Suitable methods include, but are not limited to, applying filtering or amplification techniques, determining the portion of the detected composite electronic signal contributed by the pregnant mammal and then subtracting or removing that portion of the detected composite electronic signal from the detected composite electronic signal, and / or receiving information regarding the fetal heart rate and using that information to lock in (e.g., via a boxcar integrator and / or gated integrator and / or lock-in amplifier) on the portion of the detected composite electronic signal that may be generated and / or influenced by the fetus. When information is received in step 1310, performing step 1315 may include using the information received in step 1310 to generate the fetal signal.

[0169] In step 1320, it will be determined whether the pregnant mammal is associated with a calibration factor. The pregnant mammal may be associated with a calibration factor through, for example, execution of process 500, which may occur close in time (e.g., contemporaneously, within minutes, hours, days, and / or weeks) to receiving the detected composite electronic signal in step 1305. In some cases, the calibration factor may be specific to the pregnant mammal and / or to the gestational age for her fetus. When the pregnant mammal is associated with a calibration factor, process 1300 proceeds to step 1345, where the calibration factor is received.

[0170] Additionally or alternatively, one or more physiological characteristics of the pregnant mammal and / or fetus may be requested and / or determined (step 1325). The physiological characteristics may be determined, for example, through analysis of images of the pregnant mammal's abdomen and / or analysis of fetal depth measurements. An exemplary request may take the form of, for example, a user providing a query or request to the fetal hemoglobin probe 115. The physiological characteristics may be received through any suitable means, including, but not limited to, direct entry by a user via an interface (e.g., a keypad or microphone), querying a database for medical / physiological information about the pregnant mammal, etc. In some cases, the physiological characteristics may be demographic (e.g., age or skin tone) and / or pregnancy-related (e.g., gestational age, fetal position within the abdomen, etc.). In step 1330, physiological characteristics for the pregnant mammal and / or fetus are received. A database, such as database 170, will then be queried using the received physiological characteristics to determine and / or select one or more calibration coefficients applicable to the pregnant mammal and / or fetus (step 1335).

[0171] The queried calibration coefficient(s) are received in step 1340 and applied to the fetal signal to calibrate or improve (e.g., clarify or increase accuracy of) the fetal signal, and the calibrated signal is then used to determine a level of fetal hemoglobin oxygen saturation, thereby generating a calibrated fetal signal (step 1345). In some embodiments, performing step 1345 may include using each of the calibration coefficients received in step 1340 to generate a corresponding calibration curve that accounts for one or more physiological characteristics of the pregnant mammal and / or fetus, and then applying these calibration curves to the fetal signal to calibrate and / or improve the fetal signal.

[0172] In step 1350, the calibrated fetal signal is analyzed to determine fetal hemoglobin oxygen saturation, and providing an indication of the level of fetal oxygen saturation to a user may be facilitated, for example, by computer 150 and / or a display device (step 1355). Optionally, performance of step 1355 may include indicating to the user whether the fetal hemoglobin oxygen saturation level is preductal or postductal. An indication of whether the fetal hemoglobin oxygen saturation level is preductal or postductal may assist a clinician in determining whether the fetal hemoglobin oxygen saturation level is low enough to cause concern (e.g., suggest possible fetal acidosis) or to warrant further intervention, such as a cesarean section. Further details regarding performance of step 1340 are provided below with respect to the discussion of process 1400, particularly with respect to performance of steps 1425 and 1430.

[0173] 14 provides a flowchart illustrating a process 1400 for determining fetal hemoglobin oxygen saturation levels using physiological characteristics of a pregnant mammal and / or fetus. Process 1400 may be performed, for example, by system 100 and / or its components.

[0174] Initially, a detected composite electronic signal will be received from a photodetector (e.g., detector 160) by a processor and / or computer, such as computer 150 (step 1405). The detected composite electronic signal may be received, for example, from a photodetector, a transceiver coupled to the photodetector, and / or a fetal hemoglobin probe, such as fetal hemoglobin probe 115. In some embodiments, step 1405 may further include receiving an indication of whether the fetal hemoglobin oxygen saturation level is pre-ductal or post-ductal, e.g., in a manner similar to receiving an indication of whether the fetal oxygen saturation level is pre-ductal or post-ductal in step 1405.

[0175] The detected composite electronic signal may correspond to a light signal emitted by the pregnant mammal and / or her fetus. The light entering and exiting the abdomen of the pregnant mammal may be generated by one or more light sources, such as light source 105, and may be of any acceptable frequency or wavelength (e.g., near-infrared (NIR)) and / or combination of frequencies and / or wavelengths. In some embodiments (e.g., when multiple detectors are used), the received detected composite electronic signal may include and / or be associated with a detector identifier so that the location of reception for a particular detected composite electronic signal is known. This location may then be used to analyze the received detected composite electronic signal to determine various coefficients of the detected light and / or imaged tissue.

[0176] In step 1410, physiological characteristics related to the pregnant mammal and / or fetus are received. Exemplary physiological characteristics include, but are not limited to, fetal depth within the abdomen, fetal position, fetal and / or pregnant mammal skin pigmentation, uterine thickness, skin thickness, fetal tissue type, fetal tissue thickness, density and / or thickness of various layers of tissue included in the maternal abdomen (e.g., skin, fat, uterus, subcutaneous fat, amniotic fluid, fetus, etc.). In some embodiments, the physiological characteristics may be determined from analysis of images (e.g., ultrasound or MRI) of the pregnant mammal, examples of which are provided in the illustrations of FIGS. 3A and 3B. Additionally or alternatively, the physiological characteristics may be directly input by, for example, a physician, user, and / or operator via, for example, measuring physiological characteristics and / or measuring aspects of images of the pregnant mammal's abdomen.

[0177] In step 1415, a database, such as database 170, will be queried for information regarding how physiological characteristics may affect the behavior of light traversing through the pregnant mammal and / or fetus. This determination may be the result of performing process 500, process 1300, and / or process 1100.

[0178] In step 1420, the signals received in step 1405 are analyzed to determine how physiological characteristics may affect the behavior of light as it enters, travels through, and exits the abdomen of the pregnant mammal.

[0179] The received detected composite electronic signal is then analyzed to isolate the portion of the signal that corresponds to the light incident on the fetus (step 1425). In some instances, this isolated portion of the signal may be referred to herein as the "fetal signal." Step 1425 may be performed using any suitable method for isolating the fetal signal from the received detected composite electronic signal. In many cases, the fetal signal is associated with a fetal pulse signal, and the fetal signal (which is optical and contained in the optical signal) corresponds in time to the fetal pulse signal, so that the fetal pulse signal may be used to isolate the fetal signal from the composite electronic signal. This correspondence may be used to extract the fetal signal from the composite electronic signal. Suitable methods include, but are not limited to, reducing noise in the signal, for example, through the application of filtering or amplification techniques; determining the portion of the detected composite electronic signal that is contributed by the pregnant mammal and then subtracting or removing that portion of the detected composite electronic signal from the detected composite electronic signal; and / or receiving information regarding the fetal heart rate and using that information to lock in (e.g., via a lock-in amplifier) the portion of the detected composite electronic signal that may be generated and / or influenced by the fetus.

[0180] In step 1430, the fetal signal is analyzed to determine a fetal hemoglobin oxygen saturation level. In some embodiments, two (or more) different detected composite electronic signals (also referred to herein as a first detected composite electronic signal and a second detected composite electronic signal) may be received in step 1405. The first detected composite electronic signal and the second detected composite electronic signal may be at two different wavelengths and / or wavelength ranges, in which case they will be analyzed in step 1425 to produce first and second fetal signals. The first and second fetal signals are analyzed and processed to determine a value of PPD pulse amplitude during end-diastole for each fetal signal, thereby respectively determining I and II fetal signals herein. D1 and I D2 First and second PPD pulse amplitudes during end-diastole, referred to as PPD pulse amplitudes (PPD pulse amplitudes) during systole, are then determined. In some instances, the end-diastolic PPD pulse amplitudes may also be understood and / or referred to as AC signals or AC values. The first and second fetal signals are then analyzed and processed to determine a value for the PPD pulse amplitude during systole for each fetal signal, thereby respectively referring to I and I herein. S1 and I S2 The first and second PPD pulse amplitudes during systole, referred to as PPD pulse amplitudes, are determined. In some instances, the PPD pulse amplitude during systole may also be understood and / or referred to as a DC signal or DC value.

[0181] The ratio of the ratios (also referred to as "R") would then be determined by performing calculations according to Equation 4a and / or Equation 4b below.

number

[0182] In some cases, the R value determined / calculated via execution of process 1400 is determined on a case-by-case basis for each individual pregnant mammal and / or fetus, allowing for customized or individualized R values for each situation or fetus. In some embodiments, the R value may be correlated to an intrinsic saturation SpO2 value determined from independent control data. This specificity may be clinically important because it provides a more accurate R determination than if the value for R were determined as an average value across all situations by the pulse oximeter or DOT manufacturer. In some cases, the R value is provided by the pulse oximeter manufacturer and is based on an evaluation of empirically determined results. A problem with this approach is that it assumes that the conditions under which the pulse oximeter will be used are relatively uniform across patients and situations, such as the finger or earlobe being traditional locations on the body where pulse oximetry measurements are taken. However, such assumptions cannot be made with sufficient certainty in the case of a pregnant mammal and her fetus, and generalized R values determined by manufacturers under average conditions do not exhibit the predictability or uniformity required to have sufficient confidence. Sometimes, the step of determining R may be performed, for example, continuously, periodically, or multiple times as needed during a monitoring session to tailor the R value specifically to a point in time or situation. For example, during labor and fetal delivery, R value determinations may be performed hourly, every 30 minutes, or every minute to adapt the R value to when the fetus and / or pregnant mammal or her uterus moves and / or when muscles stretch / contract. Alternatively, the R value may be a measured (independent) quantity that may not be provided by the manufacturer of the oximetry device. Calibration curves associated with these R values may be related to true SpO2 values, empirically derived and incorporated by the manufacturer.

[0183] Sometimes, the determination of fetal hemoglobin oxygen saturation level is based on the oxygenated hemoglobin (ε) and deoxygenated hemoglobin (ε) for the first and second fetal signals. dThe extinction coefficient of hemoglobin may be determined by the absorption coefficient of the tissue under study (e.g., μ a (λ)) divided by the hemoglobin concentration. The absorption coefficient may be received and / or understood, for example, via performance of process 1100 and / or step 1415. Once the extinction coefficients are determined (e.g., via looking them up in a table and / or database such as database 170), they can be plugged into the following equation (Equation 5a) to determine fetal hemoglobin oxygen saturation (SpO2):

number

[0184] After determination, provision of the fetal oxygen hemoglobin saturation (SpO2) value to a user (e.g., a doctor, nurse, or patient) may be facilitated (step 1435), for example, via providing instructions to a display device (e.g., display device 155) or to the screen of a computer (e.g., computer 150) or a device (e.g., fetal hemoglobin probe 115).

[0185] Optionally, performance of step 1435 may include indicating to the user whether the fetal hemoglobin oxygen saturation level is preductal or postductal in a manner similar to performance of step 1355. An indication of whether the fetal hemoglobin oxygen saturation level is preductal or postductal may assist the clinician in determining whether the fetal hemoglobin oxygen saturation level is low enough to cause concern (e.g., to suggest possible fetal acidosis) or to warrant further intervention, such as a cesarean section. Further details regarding performance of step 1340 are provided below with respect to the discussion of process 1400, particularly with respect to performance of steps 1425 and 1430.

[0186] Additionally or alternatively, performing step 1425 and / or step 1430 may include using the influence of one or more physiological characteristics on the detected composite electronic signal determined in step 1420, e.g., in the form of adjusting the scattering coefficient and / or the absorption coefficient. For example, the detected composite electronic signal received in step 1405 may be the result of projecting light of two different wavelengths into the maternal abdomen. Exemplary values for the first wavelength (λ1) range between 760 nm and 805 nm, and exemplary values for the second wavelength (λ2) range between 808 nm and 830 nm. In many cases, the light at λ1 and λ2 will be monochromatic or within a narrow band of the electromagnetic spectrum. Light at both wavelengths will enter the maternal abdomen, be collected via an optical cable, and be passed to one or more detectors, such as detector 160, and / or be detected directly by detector 160. The data collected by the detector may then be translated and / or processed via the following Equations 6, 7a, and 7b to determine the change in absorption coefficient and the change in oxygenated hemoglobin saturation (Δ[HbO]) and deoxygenated hemoglobin saturation (Δ[Hb]), respectively.

number

number

[0187] Δμ a The value of (λ) can be calculated, for example, by using the extinction coefficient of oxygenated hemoglobin (ε) in Equation 6 above for wavelength λ. o ) and / or the extinction coefficient of deoxygenated hemoglobin (ε d These values for two different wavelengths, λ1 and λ2, can then be input into Equations 7a and 7b to determine the relative change in oxygenated hemoglobin saturation (Δ[HbO]) and the change in deoxygenated hemoglobin saturation (Δ[Hb]).

[0188] A reconstruction algorithm is applied that takes into account, for example, the path length difference between the source and detector positions, the fetal depth, etc., to obtain the predicted change in absorption coefficient at the detector, Δμ aEquations 7a and 7b may then be solved to determine the change in oxygenated hemoglobin saturation (Δ[HbO]) and the change in deoxygenated hemoglobin saturation (Δ[Hb]) for the fetus. In one exemplary embodiment, these values (Δ[HbO] and Δ[Hb]) may be used to determine the relative fetal hemoglobin oxygen level. Additionally or alternatively, the values for Δ[HbO] and Δ[Hb] may be used to generate two-dimensional or three-dimensional maps of the abdomen of the pregnant mammal showing the relative change in oxygenated hemoglobin saturation (Δ[HbO]) and the change in deoxygenated hemoglobin saturation (Δ[Hb]). The change in oxygenated hemoglobin saturation (Δ[HbO]) and the change in deoxygenated hemoglobin saturation (Δ[Hb]) may be shown using, for example, grayscale, color coding, and the images may be topographic, cross-sectional, and / or volumetric. This process does not provide an absolute value for fetal hemoglobin oxygen saturation, but rather a relative value for fetal hemoglobin oxygen saturation that can be used to monitor fetal hemoglobin oxygen saturation over time to identify changes that may indicate that the fetus is in a state of distress, such as in the case of a rapidly or slowly declining fetal hemoglobin oxygen saturation level.

[0189] 15 provides a flowchart illustrating a process 1500 for determining a composite fetal hemoglobin oxygen saturation level using physiological characteristics of a pregnant mammal and / or fetus. Process 1500 may be performed, for example, by system 100 and / or its components. In some embodiments, process 1500 may be performed using a fetal hemoglobin probe, such as fetal hemoglobin probe(s) 115 disclosed herein.

[0190] In step 1505, a first maternal detected electronic signal is received by the processor. The first maternal detected electronic signal may be received from a first detector communicatively coupled to the processor. The first maternal detected electronic signal may correspond to a first optical signal emitted from a first location on the abdomen of the pregnant mammal, detected by a first detector positioned proximate to (on) the first location on the abdomen of the pregnant mammal, and converted into the first maternal detected electronic signal. The first emitted optical signal may be a portion of light projected into the abdomen of the pregnant mammal by a first light source. In some embodiments, performing step 1505 may be similar to performing step 905.

[0191] In step 1510, the first maternal detected electronic signal will be analyzed to optionally determine a physiological characteristic (step 1515). Then, in response to the analysis, a first calibration factor will be determined for the first optical signal emitted from the first location of the pregnant mammal (step 1520). In some embodiments, the performance of steps 1510, 1515, and / or 1520 may be similar to the performance of steps 910, 915, and / or 920, respectively.

[0192] In step 1525, a first maternal detected electronic signal is received by the processor. The first maternal detected electronic signal may be received from a first detector communicatively coupled to the processor. The first maternal detected electronic signal may correspond to a first optical signal emitted from a first location on the abdomen of the pregnant mammal, detected by a first detector positioned proximate to (on) the first location on the abdomen of the pregnant mammal, and converted into the first maternal detected electronic signal. The first emitted optical signal may be a portion of light projected into the abdomen of the pregnant mammal by a first light source. In some embodiments, performance of step 1525 may be similar to performance of step 1505, but performed with a different maternal detected electronic signal (i.e., the second maternal detected electronic signal).

[0193] In step 1530, the first maternal detected electronic signal is analyzed to optionally determine a physiological characteristic (step 1535). Then, in response to the analysis, a first calibration factor is determined for the first optical signal emitted from the first location of the pregnant mammal (step 1540). In some embodiments, performance of steps 1510, 1515, and / or 1520 may be similar to performance of steps 1510, 1515, and / or 1520, respectively, but performed with a different maternal detected electronic signal (i.e., the second maternal detected electronic signal).

[0194] In some embodiments, the first and / or second physiological trait and / or the first and / or second calibration coefficient for the pregnant mammal may be stored in a database. Sometimes, an association between the first physiological trait of the pregnant mammal and the first calibration coefficient and / or an association between the second physiological trait of the pregnant mammal and the second calibration coefficient may be made and this association may be stored in the database.

[0195] In step 1545, a first composite detected electronic signal is received from a first detector. The first detector may be positioned proximate a first location on the pregnant mammal's abdomen. In some embodiments, such as when the pregnant mammal wears a fetal hemoglobin probe for a period of time, the first composite detected electronic signal is received shortly (e.g., 0.5 seconds, 1 second, 1 minute, etc.) after step 1505 is performed. The first composite detected electronic signal may correspond to a third optical signal emitted from the pregnant mammal's abdomen and the fetus contained therein, detected by the first detector, and converted into the first composite detected electronic signal. The third emitted optical signal may be a portion of light projected by, for example, the first and / or third light sources into the pregnant mammal's abdomen and onto the fetus contained therein.

[0196] The first composite signal is analyzed or processed using one or more of the processes described herein to isolate a portion of the first composite electronic signal corresponding to light incident on the fetus, thereby generating a first fetal signal, for example, using one or more of the methods disclosed herein (step 1550). A first calibrated fetal signal is then generated by applying a first calibration factor to the first fetal signal (step 1555), and a first fetal hemoglobin oxygen saturation level is then determined using the first calibrated fetal signal (step 1560). The first fetal hemoglobin oxygen saturation level may be determined, for example, using any of the methods disclosed herein.

[0197] In step 1565, a second composite detected electronic signal is received from a second detector. The second detector may be positioned proximate a second location on the pregnant mammal's abdomen. In some embodiments, such as when the pregnant mammal wears a fetal hemoglobin probe for a period of time, the second composite detected electronic signal is received shortly (e.g., 0.5 seconds, 1 second, 1 minute, etc.) after step 1505 is performed. The second composite detected electronic signal may correspond to a third optical signal emitted from the pregnant mammal's abdomen and the fetus contained therein, detected by the second detector, and converted into the second composite detected electronic signal. The third emitted optical signal may be a portion of light projected into the pregnant mammal's abdomen and onto the fetus contained therein by, for example, the second and / or third light sources.

[0198] The second composite electronic signal is analyzed or processed using one or more of the processes described herein to isolate a portion of the second composite electronic signal corresponding to light incident on the fetus, thereby generating a second fetal signal, for example, using one or more of the methods disclosed herein (step 1570). A second calibrated fetal signal is then generated by applying a second calibration factor to the second fetal signal (step 1575), and a second fetal hemoglobin oxygen saturation level is then determined using the second calibrated fetal signal (step 1580). The second fetal hemoglobin oxygen saturation level may be determined, for example, using any of the methods disclosed herein. In step 1585, a composite fetal hemoglobin oxygen saturation level is determined using the first and second fetal hemoglobin oxygen saturation levels. Step 1585 may be performed, for example, by averaging the first and second fetal hemoglobin oxygen saturation levels. In some embodiments, process 1550 and / or steps 1545-1580 may be repeated continuously, periodically, and / or as needed, resulting in the determination of various fetal hemoglobin oxygen saturation levels over time. In these embodiments, the composite fetal hemoglobin oxygen saturation level may include more fetal hemoglobin oxygen saturation levels than the first and second fetal hemoglobin oxygen saturation levels determined in steps 1560 and 1580, and these values may optionally be averaged, and / or the composite fetal hemoglobin oxygen saturation level may be a time-weighted average of all fetal hemoglobin oxygen saturation levels determined over a given time period (e.g., 5 minutes, 15 minutes, 1 hour, etc.). An indication of the composite fetal hemoglobin oxygen saturation level will be communicated to the user at step 1590. In some cases, an indication of the first and / or second fetal hemoglobin oxygen saturation levels may also be provided at step 1590. Additionally or alternatively, an indication of whether the fetal blood used to determine the fetal hemoglobin oxygen saturation level is pre-ductal or post-ductal may also be provided at step 1590.

[0199] For the embodiments described herein, the light directed into the abdomen and fetus of the pregnant mammal may be at least two separate wavelengths and / or frequencies (e.g., red, near infrared, etc.), and the detected electronic signals received may correspond to these different wavelengths of light.

[0200] Thus, systems, devices, and methods for determining fetal oxygen levels have been disclosed. In some embodiments, use of the systems, devices, and methods described herein is particularly useful during labor and fetal delivery (e.g., during the first and / or second stage of labor), as fetal health can be difficult to assess during this process.

[0201] In some embodiments, two or more of the processes or two or more of the process parts may be combined in any order or performed together. The embodiments of the present invention are, for example, as follows. [Embodiment 1] receiving, by a processor, physiological characteristics of the pregnant mammal; determining, by the processor, an influence of the physiological characteristic on a behavior of an optical signal projected into an abdomen of the pregnant mammal; determining, by the processor, a calibration factor for the optical signal in response to the influence; A method of providing [Embodiment 2] receiving, by the processor, a composite detected electronic signal from a detector communicatively coupled to the processor, the composite electronic signal corresponding to an optical signal emitted from an abdomen of the pregnant mammal and a fetus contained therein, the optical signal detected by the detector and converted into the composite detected electronic signal, the emitted optical signal being a portion of light projected by a light source into the abdomen of the pregnant mammal and onto the fetus contained therein; generating, by the processor, a fetal signal by isolating a portion of the composite detected electronic signal corresponding to light incident on the fetus; generating, by the processor, a calibrated fetal signal by applying the calibration coefficient to the fetal signal; determining, by the processor, a fetal hemoglobin oxygen saturation level using the calibrated fetal signal; facilitating, by the processor, providing the fetal hemoglobin oxygen saturation level to a user; 2. The method of claim 1, further comprising: [Embodiment 3] determining the calibration factor for the optical signal in response to the influence; 3. The method of claim 1 or claim 2, further comprising querying a database by the processor for a calibration coefficient corresponding to the physiological characteristic. [Embodiment 4] receiving, by the processor, an indication of whether the fetal signal corresponds to pre-duct or post-duct blood; providing, by the processor, the indication of whether the fetal signal corresponds to pre-ductal blood or post-ductal blood when facilitating the provision of the fetal hemoglobin oxygen saturation level to the user; 3. The method of claim 2, further comprising: [Embodiment 5] receiving, by the processor, a maternal detected electronic signal from a detector communicatively coupled to the processor, the maternal detected electronic signal corresponding to an optical signal emitted from an abdomen of the pregnant mammal, the optical signal detected by the detector and converted into the maternal detected electronic signal, the emitted optical signal being a portion of light projected into the abdomen of the pregnant mammal by a light source; analyzing, by the processor, the maternal detected electronic signals, wherein the physiological characteristic of the pregnant mammal is determined in response to the analysis; 5. The method of any one of claims 1 to 4, further comprising: [Embodiment 6] storing, by the processor, the determined physiological characteristics for the pregnant mammal and the calibration coefficients in a database; The method of embodiment 5, further comprising: [Embodiment 7] A method described in any one of embodiments 1 to 6, wherein the physiological characteristics are received from at least one of an ultrasound device, a Doppler device, an image of the pregnant mammal's abdomen, a Fitzpatrick scale readout, a manually operated caliper, a blood measurement device, an oximeter, a pulse oximeter, and a scale. [Embodiment 8] 8. The method of any one of embodiments 1 to 7, wherein the physiological property is endogenous. [Embodiment 9] 9. The method of any one of embodiments 1 to 8, wherein the physiological property is exogenous. [Embodiment 10] 10. The method of any one of embodiments 1 to 9, wherein the physiological characteristics are the age of the pregnant mammal, the weight of the pregnant mammal, and the body mass index of the pregnant mammal. [Embodiment 11] A method according to any one of embodiments 1 to 10, wherein the received physiological characteristic is skin pigment of the pregnant mammal, and further wherein determining the influence of the physiological characteristic on the behavior of the optical signal includes determining how much of the optical signal is absorbed by skin pigment of the pregnant mammal. [Embodiment 12] A method according to any one of embodiments 1 to 10, wherein the received physiological characteristic is the thickness of the abdominal muscle layer of the pregnant mammal, and further wherein determining the influence of the physiological characteristic on the behavior of the optical signal includes determining how much of the optical signal is absorbed by the abdominal muscle layer of the pregnant mammal. [Embodiment 13] A method according to any one of embodiments 1 to 10, wherein the received physiological characteristic is the thickness of the adipose layer in the abdomen of the pregnant mammal, and further wherein determining the influence of the physiological characteristic on the behavior of the optical signal includes determining how much of the optical signal is scattered by the adipose layer in the abdomen of the pregnant mammal. [Embodiment 14] A method described in any one of embodiments 1 to 10, wherein the received physiological characteristic is a body mass index for the pregnant mammal, and further wherein determining the influence of the physiological characteristic on the behavior of the optical signal includes determining how much of the optical signal is scattered or absorbed by the abdomen of the pregnant mammal. [Embodiment 15] A method according to any one of embodiments 1 to 10, wherein the received physiological characteristic is the thickness of the abdomen of the pregnant mammal, and further wherein determining the influence of the physiological characteristic on the behavior of the optical signal includes determining how much of the optical signal is absorbed by the abdomen of the pregnant mammal. [Embodiment 16] A method according to any one of embodiments 1 to 10, wherein the received physiological characteristic is the thickness of the abdomen of the pregnant mammal, and further wherein determining the influence of the physiological characteristic on the behavior of the optical signal includes determining how much of the optical signal is scattered by the abdomen of the pregnant mammal. [Embodiment 17] A method according to any one of embodiments 1 to 10, wherein the received physiological characteristic is a hemoglobin concentration in the blood of the pregnant mammal, and further wherein determining the influence of the physiological characteristic on the behavior of the optical signal includes determining how much of the optical signal is absorbed by the hemoglobin of the pregnant mammal. [Embodiment 18] A method according to any one of embodiments 1 to 10, wherein the received physiological characteristic is hemoglobin oxygen saturation of the blood of the pregnant mammal, and further wherein determining the influence of the physiological characteristic on the behavior of the optical signal includes determining how much of the optical signal is absorbed by oxygenated hemoglobin and deoxygenated hemoglobin of the pregnant mammal. [Embodiment 19] receiving, by a processor, a maternal detected electronic signal from a detector communicatively coupled to the processor, the maternal detected electronic signal corresponding to an optical signal emitted from an abdomen of the pregnant mammal, the optical signal detected by the detector and converted into the maternal detected electronic signal, the emitted optical signal being a portion of light projected into the abdomen of the pregnant mammal by a light source; analyzing, by the processor, the maternal detected electronic signals to determine a physiological characteristic of the pregnant mammal; determining, by the processor, a calibration factor for the optical signal emitted from the pregnant mammal in response to the analysis; A method of providing [Embodiment 20] correlating, by the processor, the physiological characteristics of the pregnant mammal with the calibration coefficients; storing, by the processor, the association between the physiological characteristic of the pregnant mammal and the calibration factor in a database; 20. The method of claim 19, further comprising: [Embodiment 21] receiving, by the processor, a composite detected electronic signal from a detector communicatively coupled to the processor, the composite detected electronic signal corresponding to an optical signal emitted from an abdomen of the pregnant mammal and a fetus contained therein, the optical signal detected by the detector and converted into the composite detected electronic signal, the emitted optical signal being a portion of light projected by a light source into the abdomen of the pregnant mammal and onto the fetus contained therein; generating, by the processor, a fetal signal by isolating a portion of the composite detected electronic signal corresponding to light incident on the fetus; generating, by the processor, a calibrated fetal signal by applying the calibration coefficient to the fetal signal; determining, by the processor, a fetal hemoglobin oxygen saturation level using the calibrated fetal signal; facilitating, by the processor, providing the fetal hemoglobin oxygen saturation level to a user; 21. The method of any one of embodiments 19 or 20, further comprising: [Embodiment 22] determining the calibration factor for the optical signal in response to the influence; A method according to any one of embodiments 19 to 22, comprising the step of the processor querying a database for a calibration coefficient corresponding to the physiological characteristic. [Embodiment 23] receiving, by the processor, an indication of whether the fetal signal corresponds to pre-ductal blood or post-ductal blood; providing, by the processor, the indication of whether the fetal signal corresponds to pre-ductal blood or post-ductal blood when facilitating the provision of the fetal hemoglobin oxygen saturation level to the user; 22. The method of claim 21, further comprising: [Embodiment 24] 24. The method of any one of embodiments 19 to 23, wherein the physiological property is endogenous. [Embodiment 25] 24. The method of any one of embodiments 19 to 23, wherein the physiological property is exogenous. [Embodiment 26] A method described in any one of embodiments 19 to 25, wherein the determined physiological characteristic is skin pigment of the pregnant mammal and the calibration coefficient is related to how much of the light signal is absorbed by the skin pigment of the pregnant mammal. [Embodiment 27] A method described in any one of embodiments 19 to 25, wherein the determined physiological characteristic is the thickness of the abdominal muscle layer of the pregnant mammal, and the calibration coefficient is related to how much of the optical signal is absorbed by the abdominal muscle layer of the pregnant mammal. [Embodiment 28] A method described in any one of embodiments 19 to 25, wherein the determined physiological characteristic is the thickness of the adipose layer in the abdomen of the pregnant mammal, and the calibration coefficient is related to how much of the optical signal is scattered by the adipose layer in the abdomen of the pregnant mammal. [Embodiment 29] A method according to any one of embodiments 19 to 25, wherein the determined physiological characteristic is the thickness of the abdomen of the pregnant mammal, and the calibration coefficient is related to how much of the optical signal is absorbed by the abdomen of the pregnant mammal. [Embodiment 30] A method described in any one of embodiments 19 to 25, wherein the determined physiological characteristic is the thickness of the abdomen of the pregnant mammal and the calibration coefficient is related to how much of the optical signal is scattered by the abdomen of the pregnant mammal. [Embodiment 31] A method described in any one of embodiments 19 to 25, wherein the determined physiological characteristic is the hemoglobin concentration of the pregnant mammal's blood, and the calibration coefficient is related to how much of the optical signal is absorbed by the pregnant mammal's hemoglobin. [Embodiment 32] A method according to any one of embodiments 19 to 25, wherein the determined physiological characteristic is hemoglobin oxygen saturation of the pregnant mammal's blood, and the calibration coefficient is related to how much of the optical signal is absorbed by oxygenated hemoglobin and deoxygenated hemoglobin of the pregnant mammal. [Embodiment 33] receiving, by a processor, a first maternal detected electronic signal from a first detector communicatively coupled to the processor, the first maternal detected electronic signal corresponding to a first optical signal emitted from a first location on the abdomen of the pregnant mammal, the first optical signal being detected by a first detector positioned proximate the first location on the abdomen of the pregnant mammal and converted into the first maternal detected electronic signal, the first emitted optical signal being a portion of light projected into the abdomen of the pregnant mammal by a first light source; analyzing, by the processor, the first maternal detected electronic signal and determining, in response to the analysis, a first calibration factor for the first optical signal emitted from the first location of the pregnant mammal; receiving, by the processor, a second maternal detected electronic signal from a second detector communicatively coupled to the processor, the second maternal detected electronic signal corresponding to a second optical signal emitted from an abdomen of the pregnant mammal, the second optical signal detected by a second detector positioned at a second location on the abdomen of the pregnant mammal and converted into the second maternal detected electronic signal, the second emitted optical signal being a portion of light projected into the abdomen of the pregnant mammal by a second light source; analyzing, by the processor, the second maternal detected electronic signal and determining, in response to the analysis, a second calibration factor for the second optical signal emitted from the second location of the pregnant mammal; A method of providing [Embodiment 34] analyzing, by the processor, the first maternal detected electronic signal and determining, in response to the analysis, a first physiological characteristic for the first location on the abdomen of the pregnant mammal; 34. The method of claim 33, further comprising: [Embodiment 35] storing, by the processor, the first physiological characteristic and the first calibration factor for the pregnant mammal in a database; 35. The method of claim 34, further comprising: [Embodiment 36] correlating, by the processor, the first physiological characteristic of the pregnant mammal with the first calibration factor; storing, by the processor, the association between the first physiological characteristic of the pregnant mammal and the first calibration factor; 36. The method of claim 34 or 35, further comprising: [Embodiment 37] analyzing, by the processor, the second maternal detected electronic signal and determining, in response to the analysis, a second physiological characteristic for the second location on the abdomen of the pregnant mammal; 37. A method according to any one of embodiments 33 to 36, further comprising: [Embodiment 38] storing, by the processor, the second physiological characteristic and the calibration factor for the pregnant mammal in a database; 38. The method of embodiment 37, further comprising: [Embodiment 39] correlating, by the processor, the second physiological characteristic of the pregnant mammal with the second calibration factor; storing, by the processor, the association between the second physiological characteristic of the pregnant mammal and the second calibration factor; The method of embodiment 38, further comprising: [Embodiment 40] receiving, by the processor, a first composite detected electronic signal from the first detector, the first composite detected electronic signal corresponding to a third optical signal emitted from the abdomen of the pregnant mammal and the fetus contained therein, the third optical signal detected by the first detector and converted into the first composite detected electronic signal, the third emitted optical signal being a portion of light projected by the first light source into the abdomen of the pregnant mammal and onto the fetus contained therein; generating, by the processor, a first fetal signal by isolating a portion of the first composite electronic signal corresponding to light incident on the fetus; generating, by the processor, a first calibrated fetal signal by applying the first calibration factor to the first fetal signal; determining, by the processor, a first fetal hemoglobin oxygen saturation level using the first calibrated fetal signal; facilitating, by the processor, providing the fetal hemoglobin oxygen saturation level to a user; 39. A method according to any one of embodiments 33 to 38, further comprising: [Embodiment 41] receiving, by the processor, a second composite detected electronic signal from the second detector, the second composite detected electronic signal corresponding to a fourth optical signal emitted from the abdomen of the pregnant mammal and the fetus contained therein, the fourth optical signal detected by the second detector and converted into the second composite detected electronic signal, the emitted fourth optical signal being a portion of light projected by the second light source into the abdomen of the pregnant mammal and onto the fetus contained therein; generating, by the processor, a second fetal signal by isolating a portion of the second composite electronic signal corresponding to light incident on the fetus; generating, by the processor, a second calibrated fetal signal by applying the second calibration factor to the first fetal signal; determining, by the processor, a second fetal hemoglobin oxygen saturation level using the first calibrated fetal signal; determining, by the processor, a composite fetal hemoglobin oxygen saturation level using the first and second fetal hemoglobin oxygen saturation levels; facilitating, by said processor, providing said composite fetal hemoglobin oxygen saturation level to a user; 40. A method according to any one of embodiments 33 to 39, further comprising: [Explanation of symbols]

[0202] 10. Storage Devices 12 Bus 14 processors 16 Main Memory 18 Read-Only Memory (ROM) 22 Display 24 Input Devices 26 Cursor Control Devices 28 Communication Interface 100 System for detecting and / or determining fetal hemoglobin oxygen saturation 105, 105A, 105B light source 111A, 111B housing 115, 115C fetal hemoglobin probe 115A, 115B, 115D, 115E Fetal Probes 120 Electrical isolator 121 Optical Power Source 125 NIRS Adult Hemoglobin Probe 130 Pulse Oximetry Probe 131 communication port 133 Maternal Pulse Oximetry Probe 135 Doppler and / or ultrasound probes 138 Fetal Depth Probe 140 Uterine contraction measurement device 141 Power Port 145 Receiver 150 Computers 151 Processor-Based Systems 155 Display Devices 160, 160A-160R detector 170 databases 175 Electrocardiogram (ECG) Machine 180 Ventilation / Respiration Signal Source 301, 302 Diagram of layers of maternal tissue 305A, 305B Subcutaneous fat layer 310A, 310B abdominal muscle (skeletal muscle) layer 315A, 315B Intraperitoneal fat layer 320A, 320B Uterine wall (smooth muscle) layer 325A amniotic fluid layer 330, 330A, 330B fetus 330 Maternal tissue 340 Uterus 405 Maternal tissue 410 Fetus 415 Maternal Skin Layer 420A, 420A2, 420A3, 420B, 420B2, 420C, 420D, 420E, 420F optical signal 420A1, 420B light beam 421 Subcutaneous fat layer 425 Abdominal (skeletal) muscle layer 430 Intraperitoneal fat layer 435 Uterine wall (smooth muscle) layer 440 Amniotic fluid layer 450 Maternal tissue 455 Small Detector 702, 703 Scatter plot showing fetal signal light intensity

Claims

1. In the method, receiving, by a processor, physiological characteristics of the pregnant mammal; determining, by the processor, an influence of the physiological characteristic on a behavior of an optical signal projected into an abdomen of the pregnant mammal; and determining, by the processor, a calibration factor for the optical signal in response to the influence; The method, wherein the received physiological characteristic is an abdominal thickness of the pregnant mammal, and further wherein the determining the influence of the physiological characteristic on the behavior of the optical signal includes determining how much of the optical signal is absorbed by the abdomen of the pregnant mammal.

2. receiving, by the processor, a composite detected electronic signal from a detector communicatively coupled to the processor, the composite detected electronic signal corresponding to an optical signal emitted from an abdomen of the pregnant mammal and a fetus contained therein, the optical signal detected by the detector and converted into the composite detected electronic signal, the emitted optical signal being a portion of light projected by a light source into the abdomen of the pregnant mammal and onto the fetus contained therein; generating, by the processor, a fetal signal by isolating a portion of the composite detected electronic signal corresponding to light incident on the fetus; generating, by the processor, a calibrated fetal signal by applying the calibration coefficient to the fetal signal; determining, by the processor, a fetal hemoglobin oxygen saturation level using the calibrated fetal signal; facilitating, by the processor, providing the fetal hemoglobin oxygen saturation level to a user; The method of claim 1 further comprising:

3. determining the calibration factor for the optical signal in response to the influence; 3. The method of claim 1 or claim 2, further comprising querying, by the processor, a database for a calibration factor corresponding to the physiological characteristic.

4. receiving, by the processor, an indication of whether the fetal signal corresponds to pre-duct or post-duct blood; providing, by the processor, the indication of whether the fetal signal corresponds to pre-ductal blood or post-ductal blood when facilitating the provision of the fetal hemoglobin oxygen saturation level to the user; The method of claim 2 further comprising:

5. receiving, by the processor, a maternal detected electronic signal from a detector communicatively coupled to the processor, the maternal detected electronic signal corresponding to an optical signal emitted from an abdomen of the pregnant mammal, the optical signal detected by the detector and converted into the maternal detected electronic signal, the emitted optical signal being a portion of light projected into the abdomen of the pregnant mammal by a light source; analyzing, by the processor, the maternal detected electronic signals, wherein the physiological characteristic of the pregnant mammal is determined in response to the analysis; 5. The method of any one of claims 1 to 4, further comprising:

6. storing, by the processor, the determined physiological characteristics for the pregnant mammal and the calibration coefficients in a database; The method of claim 5 further comprising:

7. 7. The method of claim 1, wherein the physiological characteristic is received from at least one of an ultrasound device, a Doppler device, an image of the pregnant mammal's abdomen, a Fitzpatrick scale readout, a manually operated caliper, a blood measuring device, an oximeter, a pulse oximeter, and a scale.

8. The method of claim 1 , wherein the physiological property is endogenous.

9. The method of claim 1 , wherein the physiological property is exogenous.

10. 10. The method of claim 1, wherein the physiological characteristics are the age of the pregnant mammal, the weight of the pregnant mammal, and the body mass index of the pregnant mammal.

11. 11. The method of claim 1, wherein the received physiological characteristic is a skin pigment of the pregnant mammal, and further wherein determining the influence of the physiological characteristic on the behavior of the optical signal comprises determining how much of the optical signal is absorbed by the skin pigment of the pregnant mammal.

12. 11. The method of claim 1, wherein the received physiological characteristic is a thickness of a muscle layer in the abdomen of the pregnant mammal, and further wherein determining the influence of the physiological characteristic on the behavior of the optical signal comprises determining how much of the optical signal is absorbed by the muscle layer in the abdomen of the pregnant mammal.

13. 11. The method of claim 1, wherein the received physiological characteristic is a thickness of an adipose layer in the abdomen of the pregnant mammal, and further wherein determining the influence of the physiological characteristic on the behavior of the optical signal comprises determining how much of the optical signal is scattered by the adipose layer in the abdomen of the pregnant mammal.

14. 11. The method of claim 1, wherein the received physiological characteristic is a body mass index for the pregnant mammal, and further wherein determining the influence of the physiological characteristic on the behavior of the optical signal comprises determining how much of the optical signal is scattered or absorbed by the abdomen of the pregnant mammal.

15. 11. The method of claim 1, wherein the received physiological characteristic is an abdominal thickness of the pregnant mammal, and further wherein determining the influence of the physiological characteristic on the behavior of the optical signal comprises determining how much of the optical signal is scattered by the abdomen of the pregnant mammal.

16. 11. The method of claim 1, wherein the received physiological characteristic is a hemoglobin concentration in the blood of the pregnant mammal, and further wherein determining the influence of the physiological characteristic on the behavior of the optical signal comprises determining how much of the optical signal is absorbed by hemoglobin in the pregnant mammal.

17. 11. The method of claim 1, wherein the received physiological characteristic is hemoglobin oxygen saturation of the pregnant mammal's blood, and further wherein determining the influence of the physiological characteristic on the behavior of the optical signal comprises determining how much of the optical signal is absorbed by oxygenated hemoglobin and deoxygenated hemoglobin of the pregnant mammal.

Images