Processing device, and non-transitory computer-readable medium

Abstract

An input interface receives at least one of first data corresponding to actual measured values of arterial oxygen partial pressure and arterial oxygen saturation of a subject, and second data corresponding to a value of at least one of arterial carbon dioxide partial pressure, pH of arterial blood, body temperature, and concentration of 2, 3-Diphosphoglycerate in blood of the subject. A processor determines a rule for converting the arterial oxygen saturation of the subject into an estimated value of the arterial oxygen partial pressure of the subject based on at least one of the first data and the second data. In response to reception of third data corresponding to transcutaneous arterial oxygen saturation of the subject at the input interface, the processor calculates the estimated value based on the third data and the rule.

Description

PROCESSING DEVICE, AND NON-TRANSITORY COMPUTER-READABLE MEDIUM

[0001] The presently disclosed subject matter relates to a processing device for monitoring arterial oxygen partial pressure, that is an index of a respiratory function of a subject. The presently disclosed subject matter also relates to a non-transitory computer-readable medium having stored a computer program adapted to be executed by a processor installed in the processing device.Background

[0002] In an acute medical care, for example, management of the respiratory function of a subject is an important factor. Since respirations are performed to take up oxygen in the ambient air to be supplied to the body, the oxygen content in the blood may be an index of the respiratory function. Japanese Patent Publication No. 2017-538553A discloses a system configured to optimize artificial ventilation by additionally monitoring arterial oxygen saturation.Summary

[0003] It is demanded to enable non-invasive and continuous monitoring of the arterial oxygen partial pressure.

[0004] An illustrative aspect of the present disclosure provides a processing device, comprising: an input interface configured to receive at least one of first data corresponding to actual measured values of arterial oxygen partial pressure and arterial oxygen saturation of a subject, and second data corresponding to a value of at least one of arterial carbon dioxide partial pressure, pH of arterial blood, body temperature, and concentration of 2, 3-Diphosphoglycerate in blood of the subject; and a processor configured to determine a rule for converting the arterial oxygen saturation of the subject into an estimated value of the arterial oxygen partial pressure of the subject based on at least one of the first data and the second data, wherein the processor is configured to, in response to reception of third data corresponding to transcutaneous arterial oxygen saturation of the subject at the input interface, calculate the estimated value based on the third data and the rule.

[0005] An illustrative aspect of the present disclosure provides a non-transitory computer-readable medium having stored a computer program adapted to be executed by a processor installed in a processing device and configured to cause, when executed, the processing device to: receive at least one of first data corresponding to actual measured values of arterial oxygen partial pressure and arterial oxygen saturation of a subject, and second data corresponding to a value of at least one of arterial carbon dioxide partial pressure, pH of arterial blood, body temperature, and concentration of 2, 3-Diphosphoglycerate in blood of the subject; determine a rule for converting the arterial oxygen saturation of the subject into an estimated value of the arterial oxygen partial pressure of the subject based on at least one of the first data and the second data; and in response to reception of third data corresponding to transcutaneous arterial oxygen saturation of the subject at the input interface, calculate the estimated value based on the third data and the rule.

[0006] According to the configuration of each of the above illustrative aspects, since the value of arterial oxygen partial pressure of the subject is estimated with the actual measured value of transcutaneous arterial oxygen saturation that can be acquired continuously and non-invasively, it is possible to realize continuous monitoring of the estimated value of arterial oxygen partial pressure of the subject without imposing a burden in connection with the invasion at the time of blood collection. In addition, the rule for converting the actual measured value of transcutaneous arterial oxygen saturation to the estimated value of arterial oxygen partial pressure is determined through a minimum number of blood gas analyses (including zero times) based on the value of a physiological parameter of the subject that may affect the deviation of the oxygen dissociation curve. Accordingly, it is possible to obtain the estimated value of arterial oxygen partial pressure in which the physiological condition of the subject is reflected, while further reducing the burden that would be imposed on the subject.

[0007] FIG. 1 illustrates a functional configuration of a monitoring system according to an exemplary embodiment.FIG. 2 illustrates an oxygen dissociation curve.FIG. 3 illustrates events that would cause deviations of the oxygen dissociation curve.

[0008] Examples of embodiments will be described below in detail with reference to the accompanying drawings.

[0009] FIG. 1 illustrates a functional configuration of a monitoring system 10 according to an exemplary embodiment. The monitoring system 10 is configured to monitor the arterial oxygen partial pressure (PaO2) of a subject 20. The PaO2 is a value indicative of a partial pressure of oxygen contained in arterial blood, and is used as an index indicative of an oxygenated state of blood in a lung, as the respiratory function.

[0010] FIG. 2 illustrates the relationship between the PaO2 and an invasive arterial oxygen saturation (SaO2). This characteristic curve is known as an oxygen dissociation curve. The SaO2 is a value indicative of a ratio of hemoglobin bound to oxygen in arterial blood. The SaO2 may be expressed with percentages. In this example, it is illustrated as having a value from 0 corresponding to 0% to 1 corresponding to 100%.

[0011] The value of PaO2 can be estimated with the oxygen dissociation curve as long as the value of SaO2 is acquired. However, since the SaO2 is a value obtained invasively, the value of PaO2 to be acquired must be intermittent. In addition, since the SaO2 is a value obtained invasively, multiple acquisitions of the PaO2 value would be a burden on the subject.

[0012] Moreover, as illustrated with the dashed lines in FIG. 2, it is known a phenomenon in which the oxygen dissociation curve entirely deviates leftward or rightward in accordance with changes of various physiological parameters. FIG. 3 illustrates the effect of changes in the physiological parameter on the deviation of the oxygen dissociation curve.

[0013] Examples of physiological parameters causing the deviation of the oxygen dissociation curve include the affinity of oxygen and hemoglobin in arterial blood, the partial pressure of carbon dioxide in arterial blood (PaCO2), the pH of arterial blood, the body temperature (blood temperature), and the concentration of 2,3-DPG (2,3-Diphosphoglycerate) in blood. It should be noted that the blood temperature may be estimated on the basis of the body temperature that is measured at another body site, such as the body surface temperature or the rectal temperature.

[0014] In view of the fact that the difference between the SaO2 and the SpO2 is not so considerable, the inventors of the present application conceived that, once a calibrated oxygen dissociation curve is determined with consideration of the physiological parameter of the subject 20, the PaCO2 can be accurately and continuously calculated with the calibrated oxygen dissociation curve from measured values of the SpO2 that are obtained non-invasively and continuously thereafter. The calibrated oxygen dissociation curve is an example of a rule for converting the arterial oxygen saturation of the subject 20 to an estimated value of PaO2.

[0015] As a model representing the oxygen dissociation curve, the following equation (Hill equation) is known. SaO2 = (PaO2 / P50)n / [ 1 + (PaO2 / P50)n] …(1) As illustrated in FIG. 2, P50 represents the value of PaO2 that corresponds to a case where the SaO2 exhibits 50%. 26.8 is known as a standard value of the P50. Leftward deviation of the oxygen dissociation curve causes decrease of the P50, whereas rightward deviation of the oxygen dissociation curve causes increase of the P50. Namely, once the P50 as a constant is specified, it is possible to determine a calibrated oxygen dissociation curve reflecting the condition of the subject 20.

[0016] As illustrated in FIG. 1, the monitoring system 10 includes a processing device 11. An example of a technique for determining a calibrated oxygen dissociation curve with the processing device 11 will be described.

[0017] The processing device 11 includes an input interface 111. The input interface 111 is configured as a hardware interface that receives first data D1 corresponding to actual measured values of PaO2 and SaO2 of the subject 20. The actual measured values of PaO2 and SaO2 are acquired by subjecting arterial blood collected from the subject 20 to analysis with a blood gas analyzer (not illustrated). The first data D1 may be transmitted from the blood gas analyzer, or may be manually inputted by a user through a user interface (not illustrated).

[0018] As used herein, the expression "data corresponding to an actual measured value" is meant to include both a case where the data indicates the actual measured value itself, as well as a case where the data indicates a value that is obtained by applying a prescribed conversion to the actual measured value, an estimated value of the actual measured value, or the like.

[0019] The first data D1 may be in the form of analog data or digital data, in accordance with the specification of the input source. In the case where the first data D1 is in the form of analog data, the input interface 111 includes an adequate conversion circuit including an A / D converter. This description is similarly applied to other data that can be received by the input interface 111 described later.

[0020] The processing device 11 includes a processor 112. The processor 112 is configured to perform an arithmetic operation of specifying the P50 by substituting actual measured values of PaO2 and SaO2 corresponding to the first data D1 received by the input interface 111 in the Equation (1). This operation corresponds to a calibration of the oxygen dissociation curve in view of the affinity of oxygen and hemoglobin in arterial blood of the subject 20 illustrated in FIG. 3.

[0021] As illustrated in FIG. 1, the processing device 11 includes a storage 113. The processor 112 is configured to store, in the storage 113, data corresponding to the oxygen dissociation curve calibrated by the above-described operation. The storage 113 may be implemented by a semiconductor memory, a hard disk drive, a magnetic tape drive, or the like.

[0022] The above-described actual measured value of SaO2 that is inputted as the first data D1 may be replaced with the actual measured value of SpO2. However, it is preferable to acquire the actual measured value of SaO2 because not only it can be acquired together with the PaO2 by a single collection of arterial blood but also it represents the oxygen saturation of the arterial blood more directly.

[0023] The input interface 111 of the processing device 11 is configured as a hardware interface adapted to additionally receive second data D2 corresponding to an actual measured value of at least one of the PaCO2, the pH, the body temperature, and the concentration of 2, 3-DPG in the blood of the subject 20. The second data D2 may be received in addition to the first data D1, or may be received in place of the first data D1.

[0024] The actual measured values of PaCO2 and pH are acquired by subjecting arterial blood collected from the subject 20 to analysis with a blood gas analyzer (not illustrated). In this case, the second data D2 may be transmitted from the blood gas analyzer, or may be manually inputted by the user through a user interface (not illustrated).

[0025] The body temperature may be acquired through a temperature sensor (not illustrated) attached to the subject 20. The second data D2 may be transmitted from the temperature sensor, or may be manually inputted by a user through a user interface (not illustrated). It should be noted that the body temperature may not be the actual measured value. A value of 37℃, known as the standard temperature Ts of the blood, may be used as the value of the body temperature.

[0026] The 2, 3-DPG concentration is acquired by subjecting the blood collected from the subject to measurement with a measurement kit (not illustrated) using an ultraviolet absorbance measurement method, for example. In this case, the second data D2 may be transmitted from the blood gas analyzer, or may be manually inputted by the user through a user interface (not illustrated). It should be noted that the 2,3-DPG concentration may not be the actual measured value. 4.65×10-3moles, known as the standard value Ds of the 2, 3-DPG concentration, may be used as the value of the 2, 3-DPG concentration.

[0027] The P50 in Equation (1) may be specified on the basis of the second data D2 with the following equations. P50 = [ P50s ( P50c / P50s ) ( P50p / P50s ) ] (P50t / P50s ) ( P50d / P50s ) …(2) P50c = P50s + 1.273 x 10-1( Pc - Pcs ) + 1.083 x 10-4( Pc - Pcs )2…(3) P50p = P50s - 25.535 ( ph - phs ) + 10.646 ( ph - phs )2- 1.764 ( ph - phs )3…(4) P50t = P50s + 1.435 ( T - Ts ) + 4.163 x 10-2( T - Ts )2+ 6.86 x 10-4( T - Ts )3…(5) P50d = P50s + 795.63 ( D - Ds ) - 19660.89 ( D - Ds )2…(6) where, P50s: the standard value of P50 (26.8) Pc: the actual measured value of PaCO2 Pcs: the standard value of PaCO2 (40 mmHg) Ph: the actual measured value of pH Phs: the standard value of pH (7.24) T: the actual measured value of body temperature Ts: the standard value of blood temperature (37℃) D: the actual measured value of 2, 3-DPG concentration Ds: the standard value of 2, 3-DPG concentration (4.65 x 10-3mol)

[0028] It should be noted that the values of the coefficients in the above equations as well as the specific values of some physiological parameters are merely illustrative. As for a physiological parameter that is not to be monitored, a standard value thereof is substituted as the actual measured value of each equation.

[0029] By specifying the P50 as described above, the oxygen dissociation curve is calibrated on the basis of various physiological parameters. The processor 112 stores data corresponding to the calibrated oxygen dissociation curve in the storage 113.

[0030] In a case where both the first data D1 and the second data D2 are received by the input interface 111, the value of P50 that is used for calibrating the oxygen dissociation curve may be calculated with the following equations. P50 = k1 P50d1 + k2 P50d2 …(7) k1 + k2 = 1 …(8) where, P50d1: the value of P50 specified with the first data D1 P50d2: the value of P50 that is specified with the second data D2 Each of k1 and k2 is a coefficient indicative of a contribution degree of each term to the P50 that is to be finally specified, and may be appropriately determined by the user. Here, k1 and k2 are positive real numbers.

[0031] The monitoring system 10 includes a pulse oximetry probe 12. The pulse oximetry probe 12 is attached to the body of the subject 20. The pulse oximetry probe 12 is provided with a well-known configuration for measuring SpO2 of the subject 20.

[0032] Specifically, the pulse oximetry probe 12 includes multiple light sources configured to emit light beams with multiple wavelengths at which the absorbance characteristics of oxygenated hemoglobin are different from each other. For example, a first light beam having a central wavelength in the red region, and a second light beam having a central wavelength in the infrared region are irradiated onto a living tissue including the artery of the subject 20. The pulse oximetry probe 12 includes a light detecting element. The light detecting element is configured to detect light quantity of each of the first light beam and the second light beam that have passed through the living tissue, and output a signal corresponding to the light quantity.

[0033] The light attenuation A1 of the first light beam due to the arterial blood is specified from the difference between the light quantity of the first light beam emitted from the light source and the light quantity of the first light beam detected by the light detecting element. Similarly, the light attenuation A2 of the second light beam due to the arterial blood is specified from the difference between the light quantity of the second light beam emitted from the light source and the light quantity of the second light beam detected by the light detecting element. In a case where let Φ be a ratio of a light attenuation variation ΔA1 of the first light beam and a light attenuation variation ΔA2 of the second light beam caused by the pulsation of the arterial blood, SpO2 may be given by the following equation as a function of Φ. SpO2 = f (Φ) …(9)

[0034] The input interface 111 of the processing device 11 is configured as a hardware interface adapted to additionally receive third data D3 corresponding to the actual measured value of the SpO2 of the subject 20. The signal outputted from the pulse oximetry probe 12 is subjected to processing for calculating SpO2 with a pulse oximeter (not illustrated). The third data D3 may be transmitted from the pulse oximeter, or may be manually inputted by a user through a user interface (not illustrated).

[0035] The processor 112 reads out the data corresponding to the calibrated oxygen dissociation curve stored in the storage 113, and substitutes an actual measured value of SpO2 corresponding to the third data D3 in place of the value of SaO2 in Equation (1). As a result, an estimated value of PaO2 based on the calibrated oxygen dissociation curve is calculated.

[0036] The processing device 11 includes an output interface 114. The processor 112 is configured to output data E1 corresponding to the estimated value of PaO2 from the output interface 114.

[0037] The monitoring system 10 includes an output device 13. The output device 13 is configured to enable the estimated value of PaO2 to be notified to the user. The output device 13 may be implemented by a display device, a printing device, a data transmission device, or the like. The processing device 11 may be a device independent of the output device 13, or may be a part of the output device 13.

[0038] The output interface 114 is configured as a hardware interface. The data E1 may be in the form of analog data or digital data in accordance with the specification of the output device 13. In the case where the data E1 is in the form of analog data, the output interface 114 includes an adequate conversion circuit including a D / A converter. This description is similarly applied to other data that can be outputted by the output interface 114 described later.

[0039] According to the configuration of the present exemplary embodiment described above, since the value of PaO2 of the subject 20 is estimated with the actual measured value of SpO2 that can be acquired continuously and non-invasively, it is possible to realize continuous monitoring of the estimated value of PaO2 of the subject 20 without imposing a burden in connection with the invasion at the time of blood collection. In addition, the rule for converting the actual measured value of SpO2 to the estimated value of PaO2 is determined through a minimum number of blood gas analyses (including zero times) based on the value of a physiological parameter of the subject 20 that may affect the deviation of the oxygen dissociation curve. Accordingly, it is possible to obtain the estimated value of PaO2 in which the physiological condition of the subject 20 is reflected, while further reducing the burden that would be imposed on the subject 20.

[0040] The input interface 111 of the processing device 11 may be configured as a hardware interface adapted to additionally receive fourth data D4 corresponding to a value of a fraction of inspiratory oxygen (FiO2) of the subject 20. The value of FiO2 may be an actual measured value, a prescribed value, or an estimated value. The fourth data D4 may be transmitted from an oxygen breathing device (not illustrated) connected to the subject 20, or may be manually inputted by a user through a user interface (not illustrated). The FiO2 is an example of inspiratory oxygen information.

[0041] In this case, the processor 112 is configured to obtain a P / F ratio (PaO2 / FiO2) based on the estimated value of the PaO2 obtained as described above and the actual measured value of the FiO2 corresponding to the fourth data D4. The P / F ratio is an example of an index indicative of an oxygenation capability of the subject 20.

[0042] The processor 112 is configured to output data E2 corresponding to the obtained P / F ratio from the output interface 114 to the output device 13. The output device 13 is configured to enable the estimated value of P / F ratio to be notified to the user.

[0043] Since the value of PaO2 acquired through the blood gas analysis is conventionally used, the value of the P / F ratio has to be calculated intermittently. However, according to the configuration described above, since the value of P / F ratio of the subject 20 is estimated with the actual measured value of SpO2 that can be acquired continuously and non-invasively, it is possible to realize continuous monitoring of the oxygenation capability of the subject 20 without imposing a burden in connection with the invasion at the time of blood collection.

[0044] As long as the index is based on the PaO2, the index indicative of the oxygenation capability of the subject 20 may not be limited to the P / F ratio. Other examples of the index include an A-aDO2 corresponding to the difference between a PAO2 (alveolar oxygen partial pressure calculated from the alveolar equation) and the PaO2, a ratio of the A-aDO2 to the PaO2 (A-aDO2 / PaO2), a ratio of the PaO2 to the PAO2 (PaO2 / PAO2), an oxygenation index (OI), and the like. The OI is obtained by multiplying the value of (FiO2 / PaO2) with a value of a mean airway pressure (MAP). The PAO2 may be an example of the inspiratory oxygen information.

[0045] Since the SpO2 is generally presented as an integer value, the values of the PaO2 and the P / F ratio that are estimated on the basis of the actual measured value of SpO2 has to be discrete. Accordingly, the processor 112 of the processing device 11 may perform processing for simulatively enhancing the resolution of the actual measured value of SpO2.

[0046] As an example, the processor 112 may be configured to subject the third data D3 received by the input interface 111 to smoothing. For instance, it is possible to simulatively enhance the resolution of the actual measured value by subjecting a prescribed number of actual measured values of SpO2 corresponding to the third data D3 that are acquired in succession to moving average processing. As a result, the resolution of the estimated values of PaO2 and P / F ratio may be enhanced as well.

[0047] As another example, the processor 112 may be configured to derive a trendline with respect to the third data D3 received by the input interface 111 at multiple time points, and to perform extrapolation or interpolation based on the trendline. In other words, the processor 112 can simulatively enhance the resolution of the actual measured values by estimating a value of SpO2 at a desired time point that is different from the above multiple time points based on the derived trendline. As a result, the resolution of the estimated values of PaO2 and P / F ratio may be enhanced as well.

[0048] As another example, the input interface 111 may be configured to obtain an actual measured value of Φ in Equation (9) as the third data D3. In this case, the processor 112 is configured to calculate an estimated value of PaO2 based on the following equation. Here, "g" is a function that is different from "f". PaO2 = g (Φ) …(10) Since the actual measured value of Φ corresponding to the SpO2 is acquired prior to the integer conversion with the function f as a non-integer value, the resolution of the estimated values of PaO2 and P / F ratio obtained by the above equation may be enhanced as well.

[0049] As described above, since the SpO2 is generally presented as an integer value, an actual value of the SpO2 may fall within a certain range. For example, in a case where a presented measured value of SpO2 is 95%, the actual value of SpO2 may fall within a range from 94.5% to 95.4%. Accordingly, the value of PaO2 estimated from the specific measured value of SpO2 may fall within a certain range as well.

[0050] In consideration of the above fact, the processor 112 of the processing device 11 may be configured to specify a range within which the estimated value of PaO2 may fall, based on the actual measured value of SpO2 corresponding to the third data D3. In this case, the processor 112 may be configured to output data E3 indicative of a range within which the estimated value of PaO2 may fall from the output interface 114 to the output device 13.

[0051] According to such a configuration, it is possible to enable the range within which the estimated value of PaO2 of the subject 20 may fall to be notified to the user through the output device 13.

[0052] At least one of the first data D1 and the second data D2 may be updated through periodic or non-periodic measurement. The processor 112 of the processing device 11 may be configured to correct the data corresponding to the calibrated oxygen dissociation curve stored in the storage 113 in response to the reception of at least one of the first data D1 and the second data D2 as updated by the input interface 111.

[0053] In the case where the first data D1 is updated, the processor 112 specifies the P50 again with the manner described with reference to Equation (1), and corrects the oxygen dissociation curve with the re-specified value of P50. The data corresponding to the corrected oxygen dissociation curve is stored in the storage 113. The estimation of PaO2 based on the actual measured value of SpO2 corresponding to the third data D3 subsequently received by the input interface 111 is performed on the basis of a rule corresponding to the corrected oxygen dissociation curve.

[0054] In the case where the second data D2 is updated, the processor 112 specifies the P50 again with the manner described with reference to Equations (2) to (6), and corrects the oxygen dissociation curve with the re-specified value of P50. The data corresponding to the corrected oxygen dissociation curve is stored in the storage 113. The estimation of PaO2 based on the actual measured value of SpO2 corresponding to the third data D3 subsequently received by the input interface 111 is performed on the basis of a rule corresponding to the corrected oxygen dissociation curve.

[0055] According to such a configuration, the latest physiological condition of the subject 20 can be reflected in the estimated value of PaO2.

[0056] The first data D1 may include information indicative of a time point when each of the actual measured values of PaO2 and SaO2 is acquired. Similarly, the second data D2 may include information indicative of a time point when each of the actual measured values of PaCO2, pH, body temperature, and concentration of 2, 3-DPG in blood is acquired. The processor 112 of the processing device 11 may be configured to refer to the information to determine whether an elapsed time length since the acquisition of each actual measured value exceeds a threshold value. The threshold value is appropriately determined on the basis of a time length for which the reliability of the first data D1 and the second data D2 would be maintained.

[0057] In this case, the processor 112 is configured not to perform the estimation of PaO2 based on the third data D3 corresponding to SpO2 that is acquired after the determination that the elapsed time length exceeds the threshold value.

[0058] Since the first data D1 and the second data D2 are based on the values of the physiological parameters acquired intermittently, the reliability as to whether the physiological condition of the subject 20 is accurately reflected decreases with the elapse of time. Accordingly, the reliability of the data corresponding to the calibrated oxygen dissociation curve stored in the storage 113 decreases as well. According to such a configuration, the PaO2 of the subject 20 can be prevented from being estimated on the basis of the data with decreased reliability.

[0059] The processor 112 may be configured to output, from the output interface 114, notification control data N that causes the output device 13 to notify the fact that the elapsed time length exceeds the threshold value. The notification may be performed through at least one of a visual notification, an audible notification, and a haptic notification. The output device 13 in this case is an example of a notification device. The notification device may be a device independent of the output device 13.

[0060] According to the above configuration, it is possible to prompt the user to update at least one of the first data D1 and the second data D2 in order to continue the continuous monitoring of the PaO2 of the subject 20. The user may be enabled to select whether the estimated value of PaO2 is calculated.

[0061] As illustrated in FIG. 1, the input interface 111 of the processing device 11 may be configured as a hardware interface adapted to additionally receive fifth data D5 corresponding to a trend of the vital sign of the subject 20.

[0062] As used herein, the term "vital sign" means a numerical value of at least one of the pulse rate, the respiration, the body temperature, the blood pressure, and the level of consciousness, or changes with time of the numerical value. The changes with time of the numerical value can be visualized as a waveform or a graph. As used herein, the expression "trend of the vital sign" refers to a medically significant one among the changes with time of the vital sign.

[0063] The fifth data D5 may be transmitted from a device (not illustrated) that acquires the vital sign of the subject 20, or may be manually inputted by a user through a user interface (not illustrated).

[0064] In this case, the processor 112 is configured to associate the fifth data D5 received by the input interface 111 with the estimated value of PaO2 calculated on the basis of at least the third data D3 by way of time information. The vital sign may be associated with at least one of the first data D1, the second data D2, the third data D3, the fourth data D4, and the estimated value of P / F ratio by way of time information.

[0065] According to such a configuration, it is possible to facilitate works for specifying an estimated value of PaO2 at a time point when the vital sign of the subject 20 exhibits a variation based on the estimated values of PaO2 of the subject 20 acquired continuously in order to analyze relationship with the trend of the vital sign.

[0066] The processor 112 of the processing device 11 having various functions described above may be implemented by one or more non-exclusive microprocessors configured to cooperate with one or more general-purpose memories. Examples of the non-exclusive microprocessor include a CPU, an MPU, and a GPU. Examples of the non-exclusive memory include a ROM and a RAM. In this case, a computer program for executing the above-described processing may be stored in the ROM. The ROM is an example of a non-transitory computer-readable medium having stored a computer program. The non-exclusive microprocessor designates at least a part of the program stored in the ROM, loads the designated program in the RAM, and executes the above-described processing in cooperation with the RAM. The computer program may be pre-installed in the non-exclusive memory, or may be downloaded from an external server device over a communication network, and then installed in the non-exclusive memory. In this case, the external server device is an example of the non-transitory computer-readable medium having stored a computer program.

[0067] The processor 112 may be implemented by an exclusive integrated circuitry capable of executing the above-described computer program, such as a microcontroller, an ASIC, and an FPGA. In this case, the above-described computer program is pre-installed in a memory element included in the exclusive integrated circuitry. The memory element is an example of the computer-readable medium having stored a computer program. The processor 112 may also be implemented by a combination of the non-exclusive microprocessor and the exclusive integrated circuitry.

[0068] Each of the configurations referenced in the foregoing description is illustrative only to facilitate an understanding of the presently disclosed subject matter. Each exemplary configuration may be appropriately modified or combined with another exemplary configuration within the scope of the presently disclosed subject matter.

[0069] In the above exemplary embodiment, the processing device 11 is provided as a device independent of the pulse oximeter that measures the SpO2 of the subject 20. However, the processing device 11 may be incorporated in the pulse oximeter.

[0070] The present application is based on Japanese Patent Application No. 2023-127521 filed on August 4, 2023, the entire contents of which are hereby incorporated by reference.

Claims

1. A processing device, comprising: an input interface configured to receive at least one of first data corresponding to actual measured values of arterial oxygen partial pressure and arterial oxygen saturation of a subject, and second data corresponding to a value of at least one of arterial carbon dioxide partial pressure, pH of arterial blood, body temperature, and concentration of 2, 3-Diphosphoglycerate in blood of the subject; and a processor configured to determine a rule for converting the arterial oxygen saturation of the subject into an estimated value of the arterial oxygen partial pressure of the subject based on at least one of the first data and the second data, wherein the processor is configured to, in response to reception of third data corresponding to transcutaneous arterial oxygen saturation of the subject at the input interface, calculate the estimated value based on the third data and the rule.

2. The processing device according to claim 1, wherein the processor is configured to, in response to reception of fourth data corresponding to inspiratory oxygen information of the subject at the input interface, obtain an index indicative of oxygenation capability of the subject based on the estimated value and the fourth data.

3. The processing device according to claim 1 or 2, wherein the input interface is configured to receive the third data at multiple time points; and wherein the processor is configured to perform smoothing with respect to the third data received at the multiple time points to enhance resolution of the transcutaneous arterial oxygen saturation.

4. The processing device according to claim 1 or 2, wherein the input interface is configured to receive the third data at multiple time points; wherein the processor is configured to derive a trendline with respect to the third data received at the multiple time points; and wherein the processor is configured to estimate a value of the transcutaneous arterial oxygen saturation at a time point different from the multiple time points based on the trendline to enhance resolution of the transcutaneous arterial oxygen saturation.

5. The processing device according to any one of claims 1 to 4, wherein first light including a first wavelength and second light including a second wavelength different from the first wavelength are irradiated to a living tissue of the subject; and wherein the third data corresponds to a ratio of attenuation variation of the first light having passed through the living tissue and attenuation variation of the second light having passed through the living tissue.

6. The processing device according to any one of claims 1 to 5, wherein the processor is configured to specify a range within which the estimated value may fall based on the transcutaneous arterial oxygen saturation corresponding to the third data.

7. The processing device according to any one of claims 1 to 6, wherein the processor is configured to, in response to updating of at least one of the first data and the second data, correct the rule based on at least one of the first data and the second data as updated.

8. The processing device according to any one of claims 1 to 7, wherein the processor is configured not to calculate the estimated value in a case where an elapsed time length since the actual measured value is acquired exceeds a threshold value.

9. The processing device according to any one of claims 1 to 8, wherein the processor is configured to, in a case where an elapsed time length since the actual measured value is acquired exceeds a threshold value, cause a notification device to notify that the elapsed time length exceeds the threshold value.

10. The processing device according to any one of claims 1 to 9, wherein the processor is configured to, in response to reception of fifth data corresponding to a trend of a vital sign of the subject, associate the fifth data with the estimated value by way of time information.

11. A non-transitory computer-readable medium having stored a computer program adapted to be executed by a processor installed in a processing device and configured to cause, when executed, the processing device to: receive at least one of first data corresponding to actual measured values of arterial oxygen partial pressure and arterial oxygen saturation of a subject, and second data corresponding to a value of at least one of arterial carbon dioxide partial pressure, pH of arterial blood, body temperature, and concentration of 2, 3-Diphosphoglycerate in blood of the subject; determine a rule for converting the arterial oxygen saturation of the subject into an estimated value of the arterial oxygen partial pressure of the subject based on at least one of the first data and the second data; and in response to reception of third data corresponding to transcutaneous arterial oxygen saturation of the subject at the input interface, calculate the estimated value based on the third data and the rule.

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