JP7228678B2 - Biological information measuring instrument and biological information measuring method using the same - Google Patents

Description

The present invention relates to a biological information measuring instrument and a biological information measuring method using the same.

Photoplethysmography (PPG) is one of methods for noninvasively monitoring biological signals and biological information of a subject. PPG is a technique for monitoring changes in blood flow in living tissue by irradiating the surface of a subject's body with light having a predetermined wavelength and measuring time-series changes in the amount of light reflected or transmitted therethrough. Since blood flow is affected by multiple biological systems, PPG measures biological signals, for example, pulse rate (HB), heart rate variability (HRV), vascular elasticity (RI), and arterial blood oxygen saturation. (SpO2), local tissue oxygen saturation (rSO2) can be obtained.

In measurement by PPG, depending on the posture and / or body movement of the subject, the vascular system changes due to the bending of each part of the body, and the body composition changes due to the movement of fat and muscle. Conventionally, when high-precision measurement is required, subjects are assigned a resting posture and are forced to remain in that posture during measurement. Therefore, if the posture of the subject changes during measurement, there is a risk that correct measurement results will not be obtained.

Patent Literature 1 shown below discloses a technique for accurately obtaining a causal relationship between a subject's body movement and respiratory disease symptoms. Specifically, Patent Document 1 discloses a sleep evaluation system composed of a pulse oximeter and a PC, wherein the pulse oximeter acquires measurement data related to blood oxygen saturation information from a measurement finger of a subject. A probe to be acquired, a three-axis acceleration sensor for acquiring measurement data related to body motion information of a subject, and a storage unit for storing measurement data measured by the probe and the three-axis acceleration sensor, wherein the PC stores the storage A sleep evaluation system is disclosed that has a processing function that acquires measurement data stored in a unit and analyzes the relationship between the variation in the blood oxygen saturation level and the subject's body movement.

JP 2006-263054 A

However, in diagnosing a subject with a respiratory disease, the above technique disclosed in Patent Document 1 simply grasps whether or not blood oxygen saturation decreases in synchronization with body movement of the subject. It was not aimed at accurately determining the subject's blood oxygen saturation per se. In other words, originally, the blood oxygen saturation level should be obtained by measuring the subject in a correct resting posture, but in the above technology, the subject's posture has changed. In such a case, the blood oxygen saturation level measured and indicated deviates from the value that should be measured in the original ideal state.

Therefore, the present invention provides a biological information measuring device and a biological information measuring method using the same that can accurately calculate the biological information even when the posture and/or body movement of the subject changes. for the purpose.

More specifically, one object of the present invention is to correct the subject's SpO2 It is an object of the present invention to provide a biological information measuring instrument and a biological information measuring method using the same, which can more accurately calculate the .

The present invention for solving the above-mentioned problems includes the invention specifying matters or technical features shown below.

The present invention according to one aspect is a biological information measuring device. The biological information measuring device may include a biological signal acquisition section that acquires a biological signal of a subject, and a posture state signal acquisition section that acquires a posture state signal of the subject. The subject's biosignals may be output from a biosensor, including a PPG sensor. Also, the posture state signal of the subject may be output from a motion sensor. The biological information measuring device further includes a posture state estimation unit that estimates the posture state of the subject based on the posture state signal acquired by the posture state signal acquisition unit; and an SpO2 calculation unit that calculates SpO2 in the reference posture state of the subject based on the posture state estimated by the posture state estimation unit. The SpO2 calculator may calculate the SpO2 by applying a parameter set corresponding to the estimated posture state to the absorbance ratio calculated based on the acquired biological signal.

The biological information measuring device may further include a parameter set storage unit that stores a plurality of parameter sets corresponding to a plurality of posture state models.

Moreover, the biological information measuring device may further include a parameter set selection section that selects one of the predetermined parameter sets corresponding to the estimated posture state from the parameter set storage section. Then, the SpO2 calculator can correct the absorbance ratio based on the selected one predetermined parameter set.

Further, the biological information measuring device selects one or more of the parameter sets corresponding to the estimated posture state from the parameter set storage unit, and performs interpolation based on the selected one or more of the parameter sets. It may further comprise a parameter set estimator for estimating a parameter set by computation. Then, the SpO2 calculator can correct the absorbance ratio based on the estimated one parameter set.

Further, the SpO2 calculator can correct the absorbance ratio by the interpolation calculation using the probability density function. Alternatively, the SpO2 calculator may correct the absorbance ratio by the interpolation calculation using a predetermined nonlinear function.

Also, the biological information measuring device may further include a parameter set estimator that estimates a parameter set corresponding to a specific posture state based on the estimated posture state and the absorbance ratio. Then, the parameter set estimator may store the estimated parameter set in the parameter set storage.

Further, the posture state estimating section may estimate the posture state of the subject based on the biological signals output from the at least one biological sensor.

Also, the at least one biosensor may include at least one of a blood pressure sensor, pulse sensor, ECG sensor and myoelectric sensor.

Also, the motion sensor includes at least one of a gravity sensor, an acceleration sensor, a gyro sensor, a geomagnetic sensor, a pressure sensor, an ultrasonic sensor, an infrared sensor, an image sensor, and a spectrum sensor.

Moreover, the present invention according to another aspect can be a biological information measuring method using a biological information measuring instrument. The method may include acquiring biometric signals of a subject and acquiring postural state signals of the subject. The subject's biosignals may be output from a biosensor, including a PPG sensor. Also, the posture state signal of the subject may be output from a motion sensor. The method also includes: estimating a posture state of the subject based on the acquired posture state signal; and calculating SpO2. Then, calculating the SpO2 is calculating the SpO2 by applying a parameter set corresponding to the estimated posture state to the absorbance ratio calculated based on the acquired biological signal. can include

Furthermore, the present invention according to another aspect can also be configured as a computer program for executing the above method under the control of a processor in a computing device and a recording medium recording the same.

In this specification and the like, the term "means" does not simply mean physical means, but also includes those whose functions are realized by software. Also, the function of one means may be realized by two or more physical means, or the functions of two or more means may be realized by one physical means.

In addition, in the present disclosure, the term "system" includes a logical assembly of multiple devices (or functional modules that implement specific functions), and each device or functional module is physically a single entity. It does not matter whether it is configured or configured as a separate object.

According to the present invention, even when the posture and/or body movement of a subject change, the biological information can be accurately calculated.

Other technical features, objects, effects and advantages of the present invention will be made clear by the following embodiments described with reference to the accompanying drawings.

It is a block diagram showing an example of composition of a biological information measuring device concerning one embodiment of the present invention. 4 is a block diagram for explaining details of a control unit of the biological information measuring device according to one embodiment of the present invention; FIG. It is a block diagram showing an example of composition of a biological information measuring device concerning one embodiment of the present invention. It is a figure which shows an example of the parameter mixture ratio map in the biological information measuring device which concerns on one Embodiment of this invention. FIG. 10 is a diagram showing an example of body composition distribution assumed according to the posture state of a subject; FIG. 10 is a diagram showing an example of body composition distribution assumed according to the posture state of a subject; It is a block diagram showing an example of composition of a biological information measuring device concerning one embodiment of the present invention. It is a block diagram showing an example of composition of a biological information measuring device concerning one embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiments described below are merely examples, and are not intended to exclude various modifications and application of techniques not explicitly described below. The present invention can be implemented in various modifications (for example, by combining each embodiment) without departing from the scope of the invention. In addition, in the description of the drawings below, the same or similar parts are denoted by the same or similar reference numerals. The drawings are schematic and do not necessarily correspond to actual dimensions, proportions, and the like. Even between the drawings, there are cases where portions with different dimensional relationships and ratios are included.

[First embodiment]
In this embodiment, when measuring SpO2, the posture of the subject is observed, the optimal parameter set is selected according to the observed posture, and the selected parameter set is applied to the calculated absorbance ratio. , SpO2 and a measurement method using the same.

FIG. 1 is a block diagram showing an example configuration of a biological information measuring instrument according to one embodiment of the present invention. The biological information measuring instrument 1 shown in the figure is a device for measuring SpO2, which is one of the biological indicators of a subject, and includes, for example, a sensor section 10, a control section 20, a user interface section 30, a communication It is configured including components such as the interface unit 40 . The biological information measuring device 1 is generally called a pulse oximeter, but is not limited to this. For example, the biological information measuring instrument 1 may be configured as an integrated type in which these components are accommodated in one housing (not shown). Such an integrated biological information measuring device 1 can be attached to a subject's chest or finger, for example. As another example, the biological information measuring device 1 may be configured such that all or part of the sensor section 10 and the like are separated from the housing. Alternatively, some components such as the control unit 20, the user interface unit 30, and the communication interface unit 40 may be configured integrally as one controller board or control device body. Alternatively, the biological information measuring instrument 1 may be configured such that part of the functions of the control section 20 are executed by an external device (for example, a computing device).

The sensor unit 10 includes, for example, at least one biosensor 12 and at least one motion sensor 14 . The biosensor 12 is a sensor that observes a subject's biophenomenon and detects and outputs a biosignal based on the biophenomenon. Biosensor 12 typically includes a PPG sensor 12a for measuring SpO2 (see FIG. 2). As is obvious to those skilled in the art, the PPG sensor 12a is an active sensor having a light emitting portion for emitting light of two wavelengths (red light and infrared light) and a light receiving portion for receiving these lights. A sensor, for example transmissive and reflective. Although the present disclosure assumes that the PPG sensor 12a is of a reflective type, it is not limited to this. The reflective PPG sensor 12a receives reflected light (which may include scattered light, diffused light, etc.) from the irradiated living body. As will be described later, the biological signals detected by the PPG sensor 12a can be used to estimate the subject's posture and/or body movement state (hereinafter referred to as "posture state"). In other words, changes in biosignals detected by the PPG sensor 12a can be regarded as changes in the subject's posture. The posture state may include, for example, the movement state of a specific part such as raising and lowering the subject's hand or upper arm. Also, the biosensor 12 may include at least one of a blood pressure sensor, a pulse sensor, an ECG sensor, and a myoelectric sensor. At least some of these biosensors 12 are attached, for example, to measurement sites or locations of the subject according to the characteristics of the sensors, and detect biosignals. A biological signal detected by the biological sensor 12 is output to the control unit 20 .

The motion sensor 14 is a sensor that observes the posture state of the subject and detects and outputs a signal related to the posture state (hereinafter referred to as "posture state signal"). A known sensor can be used for the motion sensor 14 . As an example, the motion sensor 14 includes a gravity sensor, an acceleration sensor, a gyro sensor (these may be collectively referred to as an "inertial sensor"), a geomagnetic sensor, a pressure sensor, an ultrasonic sensor, an infrared sensor, an image sensor. , and a spectral sensor. A posture state signal detected by the motion sensor 14 is output to the control unit 20 . It should be noted that some of the motion sensors 14 may not be attached directly to the subject, but may be constructed and arranged to observe from a remote location, for example, from the subject. For example, the image sensor can be configured as a camera to capture an image of a subject and output the image signal to the biological information measuring instrument 1 or an external computing device.

The control unit 20 typically includes a processor 22 and a memory 24 , and is a component that comprehensively controls the operation of the biological information measuring device 1 under the control of the processor 22 . The memory 24 holds, for example, processing programs and various setting information. A processing program may be configured, for example, including several program modules. In addition, in this embodiment, the memory 24 is configured to store one or more parameter sets necessary for calculating SpO2, which will be described later, and to store the calculated SpO2 as a measurement result. For example, the control unit 20 executes a predetermined processing program under the control of the processor 22, cooperates with other components, and calculates SpO2 based on the acquired biomedical signals and posture state signals, This is stored in the memory 24 as a measurement result. In this sense, the control unit 20 functions as a computing device. The measurement results may include, for example, a timestamp indicating the time the SpO2 was measured. In the present embodiment, the calculated SpO2 is the SpO2 estimated in the reference posture state in consideration of the subject's current posture state. The details of SpO2 calculation will be described later.

The user interface unit 30 is a component that provides a user interface that functions interactively for subjects and/or medical professionals such as doctors (hereinafter these people may be collectively referred to as "users"). be. For example, under the control of the processor 22, the user interface unit 30 receives an input operation from the user and/or displays, for example, the calculated SpO2 measurement result to the user. A simple configuration example of the user interface unit 30 can be implemented by a power button and a display such as an LED or LCD. Also, the user interface unit 30 may include a speaker, a vibrator, and the like. As another example, the user interface unit 30 may be a touch panel. The user can, for example, interactively operate the user interface unit 30 as a touch panel to display necessary information and perform various settings of the biological information measuring device 1 .

In addition, in the present disclosure, the user interface unit 30 is configured as part of the biological information measuring device 1, but is not limited to this. For example, part or all of the user interface unit 30 may be realized by an external computing device. As an example, the external computing device is configured to be able to communicate with the control unit 20 via the communication interface unit 40, and the user operates a web browser on the computing device to obtain the measurement results and/or the measurement results. You can refer to the analysis results for With such a configuration, the biological information measuring instrument 1 does not need to have the user interface section 30, or may have a minimal configuration, and the housing size can be reduced.

The communication interface unit 40 is a component for communicably connecting the biological information measuring instrument 1 to an external device. The form of connection between the communication interface section 40 and the external device is not limited to wired and/or wireless, and the communication interface section 40 employs a configuration corresponding to such a form of connection. For example, the communication interface unit 40 can be designed in compliance with the USB standard, the Bluetooth (registered trademark) standard, the Wi-Fi (registered trademark) standard, and the like. As an example, the communication interface unit 40 is defined as a USB mass storage class, and the measurement results stored in the memory 24 of the biological information measuring instrument 1 are read out by an external device.

FIG. 2 is a block diagram for explaining the details of the control section of the biological information measuring instrument according to one embodiment of the present invention. As shown in the figure, the control unit 20 of the biological information measuring device 1 includes, for example, a sensor control unit 201, a biological signal reception unit 202, a posture state signal reception unit 203, an absorbance ratio calculation unit 204, and a posture state It includes an estimation unit 205 , a parameter set storage unit 206 , a parameter set selection unit 207 , an SpO2 calculation unit 208 and a measurement result storage unit 209 . Also, in this example, as the biosensor 12 of the sensor unit 10, a PPG sensor 12a is illustrated, and as the motion sensor 14, an inertial sensor 14a and a triaxial geomagnetic sensor 14b are illustrated. The inertial sensor 14a typically includes a 3-axis acceleration sensor and a 3-axis gyro sensor, and together with the 3-axis geomagnetic sensor 14b functions as a 9-axis motion sensor. In addition, as described above, the motion sensor 14 is not limited to these sensors, and may include a camera such as an image sensor or a spectrum sensor.

The sensor control section 201 controls the operation of the sensor section 10 . For example, the sensor control unit 201 performs light emission control for driving the light emitting unit of the PPG sensor 12a in order to start measuring SpO2 in accordance with an instruction from the user interface unit 30 based on the user's operation.

The biosignal receiver 202 receives or acquires biosignals output from the PPG sensor 12a. The biological signal output from the PPG sensor 12a is typically red light (for example, wavelength λ1 = 660 to 670 nm or its vicinity) emitted by the first light emitting unit (not shown), which is biological tissue (arterial blood). A signal component based on the first reflected light obtained by irradiating a living body and an infrared light (for example, wavelength λ2 = 880 to 940 nm or its vicinity) emitted by a second light emitting unit (not shown) and a signal component based on the second reflected light obtained by irradiating the tissue. The biosignal receiver 202 is an example of a biosignal acquirer, and the biosensor 12 itself or a configuration including the biosensor 12 and the biosignal receiver 202 can also be understood as an example of the biosignal acquirer. The biosignal receiver 202 outputs the received biosignal to the absorbance ratio calculator 204 .

The posture state signal receiving unit 203 receives or acquires posture state signals output from various motion sensors 14 (inertial sensor 14a and geomagnetic sensor 14b in this example). The posture state signal reception unit 203 is an example of a posture state signal acquisition unit, and the motion sensor 14 itself or a configuration composed of the motion sensor 14 and the posture state signal reception unit 203 is also understood as an example of a posture state signal acquisition unit. can be Posture state signal reception section 203 outputs the received posture state signal to posture state estimation section 205 .

The absorbance ratio calculator 204 calculates an absorbance ratio (R) for use in calculating SpO2 based on the biological signal output from the biological signal receiver 202 . The absorbance ratio calculator 204 outputs the calculated absorbance ratio (R) to the SpO2 calculator.

The absorbance ratio (R) is a value calculated by a known method using the difference in absorption coefficients of oxygenated hemoglobin (O ₂ Hb) and reduced hemoglobin (HHb) for light of different wavelengths. More specifically, the absorbance ratio (R) can be calculated by Equation 1 below.
R=Red/IR=(AC _Red /DC _Red )/(AC _IR /DC _IR ) Equation 1
where Red is the absorbance of the received red light (that is, the first reflected light) and IR is the absorbance of the received infrared light (that is, the second reflected light). AC _Red is the absorbance of the AC signal component (that is, pulsation component) of the received red light Red, DC _Red is the absorbance of the DC signal component of the received red light Red, and AC _IR is the AC signal of the received infrared light IR. The component (ie, pulsating component) absorbance, DC _IR , is the absorbance of the DC signal component of the received infrared light IR.

ただし、［Ｏ_２Ｈｂ］は酸化ヘモグロビン濃度、［ＨＨｂ］は還元ヘモグロビン濃度である。
これより、ＳｐＯ２は、Ｂｅｅｒ－Ｌａｍｂｅｒｔ則を考慮して、ＳｐＯ２は、以下の理論式から算出される。

ただし、ε_{ＨＨｂ，Ｒｅｄ}は還元ヘモグロビン（ＨＨｂ）に対する赤色光Ｒｅｄのモル吸光係数、ε_{Ｏ２Ｈｂ，Ｒｅｄ}は酸化ヘモグロビン（Ｏ_２Ｈｂ）に対する赤色光Ｒｅｄのモル吸光係数、ε_{Ｏ２Ｈｂ，ＩＲ}は酸化ヘモグロビン（Ｏ_２Ｈｂ）に対する赤外光ＩＲのモル吸光係数、及びε_{ＨＨｂ，ＩＲ}は還元ヘモグロビン（ＨＨｂ）に対する赤外光ＩＲのモル吸光係数である。The calculated absorbance ratio (R) is used for conversion to SpO2 according to the Beer-Lambert law. SpO2 is represented by the following definitional formula.

However, [O ₂ Hb] is the oxygenated hemoglobin concentration, and [HHb] is the reduced hemoglobin concentration.
From this, SpO2 is calculated from the following theoretical formula in consideration of the Beer-Lambert law.

where ε _{HHb, Red} is the molar absorption coefficient of red light Red with respect to reduced hemoglobin (HHb), ε _{O2Hb, Red} is the molar absorption coefficient of red light Red with respect to oxidized hemoglobin (O ₂ Hb), ε _{O2Hb, IR} is oxidized hemoglobin ( O ₂ Hb) and ε _HHb,IR is the infrared IR molar extinction coefficient for reduced hemoglobin (HHb).

By the way, it is known that the Beer-Lambert law has a large divergence between the theoretical formula and experimental values. Therefore, conventionally, the actual SpO2 is calculated using a fixed parameter set that is linearly fitted to the SpO2 region of 80 to 100%, for example, using the following equations and numerical values.
SpO2=α _fix −β _fix ×R Equation 4
However, α _fix =110 and β _fix =25.

However, the conventional fixed parameter set is based on the premise that the subject is in the standard posture state and that the posture state has not changed (that is, is in a resting state). Therefore, when the subject's posture state is other than the reference posture state, the SpO2 calculated using the fixed parameter set is not necessarily accurate. Therefore, as will be described later, the biological information measuring instrument 1 of the present disclosure calculates SpO2 using a parameter set considering the posture state instead of the fixed parameter set.

Still referring to FIG. 2 , posture state estimation section 205 estimates the posture state of the subject based on the posture signal output from posture state signal reception section 203 . The postural state of the subject includes, for example, lying (supine and prone), sitting, standing, and intermediate postures among these postures. In this embodiment, the posture state estimation unit 205 estimates one of the three posture states of the lying position, the sitting position (reclining), and the standing position. As an example, when a posture signal indicating a horizontal direction (inclination angle (elevation angle)=0 degrees) is acquired from the motion sensor 14 attached to the chest of the subject, the posture state estimation unit 205 determines the posture state of the subject to be lying. Assume the state. As another example, when a posture signal indicating a vertical direction (tilt angle=90 degrees) is acquired from the motion sensor 14 attached to the chest of the subject, the posture state estimation unit 205 determines the posture state of the subject to be the standing state. We estimate that As still another example, when a posture signal indicating an oblique direction (for example, an inclination angle of 60 degrees) is acquired from the motion sensor 14 attached to the chest of the subject, the posture state estimation unit 205 determines the posture state of the subject as sitting. Assume the state. Furthermore, as described in other embodiments, the posture state estimating unit 205 can indicate the body posture from the lying position to the standing position, for example, by the tilt angle. Posture state estimation section 205 outputs the estimated posture state to parameter set selection section 207 . Note that, as described in other embodiments, the posture state estimation unit 205 may further estimate the posture state of the subject based on biosignals obtained from the biosensor 12 .

The parameter set storage unit 206 stores preset parameter sets corresponding to each of a plurality of posture state models. Parameter set storage unit 206 can typically be formed as a certain storage area on memory 24 . The parameter set includes, but is not limited to, several parameters for calculating SpO2 from the absorbance ratio (R), such as α, β, and γ. In the present disclosure, parameter sets are referred to as "parameter set (α, β)" or "parameter set (α, β, γ)" as necessary. The parameter sets may include, for example, a lying parameter set corresponding to the lying model, a sitting parameter set corresponding to the sitting model, and a standing parameter set corresponding to the standing model, but are not limited to these. can't In other words, these parameter sets are correction parameter sets for estimating SpO2 during measurement in the subject's reference posture state. A parameter set can be defined, for example, from empirically obtained data such as from clinical trials.

Parameter set selection section 207 selects and reads out at least one parameter from a plurality of parameter sets stored in parameter set storage section 206 based on the posture state estimated by posture state estimation section 205 . For example, when the posture state output from posture state estimation section 205 indicates a sitting state, parameter set selection section 207 extracts a sitting parameter set from parameter set storage section 206 . The parameter set selection unit 207 outputs the selected and read parameter set to the SpO2 calculation unit 208 .

The SpO2 calculator 208 calculates SpO2 based on the absorbance ratio (R) output from the absorbance ratio calculator 204 and the parameter set (α, β) output from the parameter set selector 207 . Specifically, the SpO2 calculator 208 calculates SpO2 by applying a parameter set (α, β) to the absorbance ratio (R) according to the following equation.
SpO2 = α + β × R ... Formula 5

That is, the parameter set (α, β) referred to here is composed of values considering the posture of the subject, instead of fixed values that do not take into account the posture of the subject. Therefore, by applying the parameter set (α, β) to the absorbance ratio (R), the SpO2 in the standard posture state corrected with respect to the SpO2 in the posture state at the time of measurement is calculated. become. SpO2 calculation section 208 outputs the calculated SpO2 to measurement result storage section 209 .

The measurement result storage unit 209 stores the SpO2 output from the SpO2 calculation unit 208 as the measurement result. Measurement result storage unit 209 can typically be formed as a certain storage area on memory 24 . For example, the user can browse the measurement results stored in the measurement result storage unit 209 by operating the user interface unit 30 .

As described above, according to the present embodiment, when SpO2 is measured, the posture state of the subject is observed, the optimal parameter set corresponding to the observed posture state is selected, and the selected parameter set is used as the calculated absorbance Since the SpO2 is calculated by applying it to the ratio, it is possible to calculate the SpO2 in the standard posture state that is corrected with respect to the SpO2 in the posture state at the time of measurement.

[Second embodiment]
In the present embodiment, when SpO2 is measured, the posture state of the subject is observed, and an optimal parameter set is estimated from a preset parameter set according to the posture state estimated thereby, and the estimated parameter set is calculated. A biological information measuring device for calculating SpO2 by applying the calculated absorbance ratio and a measuring method using the same will be described.

FIG. 3 is a block diagram showing an example of the configuration of the biological information measuring device according to one embodiment of the present invention. The biological information measuring instrument 1 according to the present embodiment differs from the biological information measuring instrument 1 according to the first embodiment in that a parameter set estimating section 210 is provided instead of the parameter set selecting section 207. . Moreover, the posture state estimation unit 205 of the present embodiment is configured to estimate the posture state from the measured tilt angle, instead of selectively specifying a preset posture state.

That is, posture state estimating section 205 estimates and outputs the posture state based on the posture state signal output from posture state signal receiving section 203 . For example, based on the posture state signal, the posture state estimation unit 205 identifies the posture state by the tilt angle between the lying position and the sitting position or the tilt angle between the sitting position and the standing position. Posture state estimation section 205 outputs the posture state indicated by the tilt angle to parameter set estimation section 210 .

Parameter set estimating section 210 estimates an optimum parameter set used for calculating SpO2 based on the tilt angle output from posture state estimating section 205 . In this embodiment, the parameter set estimation unit 210 is configured to be able to refer to a parameter mixture ratio conversion map (hereinafter referred to as "mixture ratio conversion map") as shown in FIG. 4(a), for example. The parameter mixing ratio indicates at what ratio (weight) the corresponding parameters in different parameter sets are mixed. The mixture ratio conversion map may be held in a predetermined data structure in a predetermined storage area of the memory 24, or may be configured as part of the parameter set estimation section 210, for example. The mixture ratio conversion map shown in FIG. 4(a) is defined such that the mixture ratio linearly changes in relation to the inclination angle between the lying position and the sitting position. In another example, the mixture ratio conversion map is defined such that the mixture ratio changes non-linearly in relation to the tilt angle, as shown in FIG.

More specifically, the parameter set estimator 210 extracts one or more parameter sets from the parameter set storage 206 according to the tilt angle. For example, if the tilt angle is 30 degrees between the lying position and the sitting position, the parameter set estimation unit 210 extracts the lying position parameter set and the sitting position parameter set that are set adjacent to the tilt angle. Subsequently, the parameter set estimator 210 refers to the corresponding mixture ratio conversion map, determines the mixture ratio of the extracted parameter sets from the tilt angle, and calculates the parameter set according to the determined mixture ratio. For example, if the lying parameter sets are α _Lying and β _Lying , the lying parameter sets α _Sitting and β _Sitting , and the mixing ratio is 67:33, the parameter set (α, β) is
α=α _Lying ×. 67+α _Sitting ×. 33
β=β _Lying ×. 67+β _Sitting ×. 33
is calculated as
The parameter set estimation unit 210 outputs the calculated parameter set to the SpO2 calculation unit 208 as in the first embodiment.

The SpO2 calculation unit 208, as in the first embodiment, based on the absorbance ratio (R) output from the absorbance ratio calculation unit 204 and the parameter set (α, β) output from the parameter set selection unit 207 to calculate SpO2.

As described above, according to the present embodiment, the posture state is estimated from the tilt angle based on the posture state signal, one or more parameter sets are extracted according to the estimated tilt angle, and the mixture ratio By referring to the conversion map, the mixture ratio is determined from the tilt angle, and using the determined mixture ratio, the optimum parameter set is estimated or calculated, so SpO2 can be more accurately measured regardless of the subject's posture. can be calculated.

(Example 2-1)
In this example, modeling of a non-linear mixing ratio conversion map as shown in FIG. 4(b), for example, will be described. However, in this example, to simplify the explanation, it is between the lying position and the standing position (however, the supine position - standing position - prone position (prone position), and the supine position - standing position and standing position - prone position). is symmetrical with the order.). The parameter set estimator 210 estimates an optimal parameter set using one or more parameter sets according to the estimation model described here.

First, it is assumed that the body composition in each posture of the subject has certainty in the form of a normal distribution, and as shown in FIG. I think. Each parameter set follows a normal distribution with mean μ=n and variance σ=1/2.

Let f(x) be the function following the lying parameter set distribution, and g(x) be the function following the standing parameter set distribution.

であるから、ｆ（０）：ｇ（０）は、

となる。つまり、傾斜角度ｘ＝０のときの最適パラメータセットは、臥位パラメータセットを９２％、立位パラメータセットを８％の割合で混合した値となる。Referring to FIG. 5, when considering the optimal parameter set when the tilt angle x=0 (rad), only the lying parameter set may be selected due to the fully lying posture state. However, in this example, we introduce the concept of mixed distributions. That is, consider the overlap of the distributions of f(x) and g(x) when x=0. Specifically, f(0) and g(0) are

So f(0):g(0) is

becomes. That is, the optimal parameter set when the tilt angle x=0 is a value obtained by mixing 92% of the lying parameter set and 8% of the standing parameter set.

Similarly, based on the tilt angle x, the mixture distribution function is used to determine the mixture ratio of the different parameter sets, thereby calculating the optimum parameter set. For example, the mixing ratio of the optimal parameter sets when the tilt angle is x=6/π is 69% for the lying parameter set and 31% for the standing parameter set.

If it is desired to assume that the mixing ratio at the tilt angle x=0 is more biased toward the supine position, the mixing ratio can be arbitrarily adjusted by setting the variance σ small.

The mixture ratio calculated as described above (for example, lying parameter set = 69%, standing parameter set = 31%) is, as shown in FIG. It can also be considered as the contribution rate of each normal distribution f(x)/2, g(x)/2 in (f(x)+g(x)))/2.

This can also be extended to N distributions of parameter sets.

As described above, by considering the distribution of parameter sets, it is possible to model a non-linear mixing ratio conversion map such as that shown in FIG. 4(b). Thereby, the parameter set estimation unit 210 estimates the optimum parameter set by referring to such a mixture ratio conversion map.

In this embodiment, an example using a normal distribution has been described, but the present invention is not limited to this, and other distributions such as gamma distribution and Poisson distribution may be used.

(Example 2-2)
In this example, a case will be described in which the mixture distribution of the above parameter set is expanded to multiple variables.

である。ただし、本例では、ｇ（ｘ，ｙ）は、ｆ（ｘ，ｙ）よりもｙ軸方向に分散が大きい分布として定義している。That is, the distribution functions f(x, y) and g(x, y), the mixing ratios of the lying parameter set and the standing parameter set are defined as follows, respectively.
Mixing ratio of supine parameter set = f(x, y)/(f(x, y) + g(x, y))
Mixing ratio of standing parameter set = g (x, y) / (f (x, y) + g (x, y))
however,

is. However, in this example, g(x, y) is defined as a distribution having a greater variance in the y-axis direction than f(x, y).

As described above, the mixing ratio of each parameter set is determined according to the value of the tilt angle (x, y). Therefore, the parameter set estimating unit 210 determines a more realistic mixture ratio from the tilt angle (x, y) specified based on the posture state signal detected by the motion sensor 14, for example, and uses the determined mixture ratio as Since the optimum parameter set is estimated or calculated by using this, SpO2 can be calculated more accurately regardless of the posture of the subject.

(Example 2-3)
The modeling of the nonlinear mixture ratio conversion map can also be realized by using nonlinear functions based on various n-order polynomials instead of the above mixture distribution functions. As an example, f(x) is represented by the following nonlinear function.

であっても良い。更に他の例として、ｆ（ｘ）は、
ｆ（ｘ）＝０．９２８８ｘ^３－２．２９２８ｘ^２＋０．６７３ｘ＋１．００４３ …式１７
であっても良い。As another example, f(x) is

can be As yet another example, f(x) is
f(x)=0.9288x ³ −2.2928x ² +0.673x+1.0043 Equation 17
can be

Also, as described above, the parameter set distribution based on the nonlinear function may be expanded into multiple variables. That is, the non-linear function with the calculated tilt angle (x, y) can be defined as follows in this example.
f(x,y)=0.9288x ³ −2.2928x ² +0.673x+1.0043−y ² Equation 18

[Third embodiment]
In the present embodiment _{, SpO2} is calculated, a biological information measuring device and a measuring method using the same will be described for estimating the parameter set (α ₂ , β ₂ ) when changing to another posture state in a short time, for example. In other words, the present embodiment utilizes the characteristic that the SpO2 value does not change or changes only slightly immediately after the change in the posture state of the subject.

FIG. 7 is a block diagram showing an example configuration of a biological information measuring device according to an embodiment of the present invention. The biological information measuring instrument 1 according to the present embodiment is configured so that the parameter set estimation unit 210 can newly estimate a parameter set based on the SpO2 calculated by the SpO2 calculation unit 208. It differs from the embodiment. The functions and/or configurations of the other components in the figure are the same as those described above, so descriptions thereof are omitted. In the following description, it is assumed that the parameter set storage unit 206 stores, for example, sitting parameter sets (α _Sitting , β _Sitting ).

For example, based on the detected posture signal, the posture state estimation unit 205 estimated that the posture state of the subject was sitting (tilt angle=60 degrees). Assume that the reclined position (inclination angle=30 degrees) is estimated from the above. Since the parameter set selection unit 207 cannot extract the parameter set for reclining from the parameter set storage unit 206, it requests the parameter set estimation unit 210 to estimate the parameter set for reclining.

In response to this, when parameter set estimation section 210 receives a new posture state (that is, tilt angle=30 degrees) from posture state estimation section 205, parameter set estimation section 210 corresponds to, for example, the previous posture state from parameter set storage section 206. Based on the SpO2 value calculated when the posture state stored in the measurement result storage unit 209 is the sitting state and the biological signal detected by the absorbance ratio calculation unit 204 The calculated absorbance ratio is acquired. Subsequently, the parameter set estimation unit 210 estimates a parameter set (α _Reclining , β _Reclining ) for the reclining posture based on the sitting position parameter set, the SpO2 value, and the absorbance ratio. That is, in the present embodiment, it is assumed that the SpO2 value does not change or is small immediately after the change in posture (for example, several seconds to several minutes) before and after the change in posture. As another example, the parameter set estimating unit 210 estimates a new parameter set further based on the absorbance ratio calculated in the previous posture state in addition to the sitting parameter set, the SpO2 value, and the absorbance ratio. Also good. In this case, for example, the parameter set estimator 210 may be configured to receive the absorbance ratio and the posture state in time series from the absorbance ratio calculator 204 and the posture state estimator 205, respectively. The parameter set estimation unit 210 stores the newly estimated parameter set in the parameter set storage unit 206 as a reclining parameter set.

As a result, for example, when parameter sets for each of the lying position, sitting position, and standing position are prepared in advance in the parameter set storage unit 206, the posture state of the subject changes to a state other than these during SpO2 measurement. However, parameter sets can be estimated and new estimated parameter sets can be added to the parameter set storage unit 206 at any time, and parameter sets for various posture states can be accumulated. Become.

[Fourth embodiment]
In the present embodiment, a parameter set (α _fix , β _fix , γ) obtained by adding a new correction parameter γ to the previous fixed parameter set (α _fix , β _fix ) is used to calculate SpO2 using a biological information measuring device and A measurement method using this will be described. Here, γ is a function according to the posture state and the absorbance ratio R.

It is a block diagram showing an example of composition of a biological information measuring device concerning one embodiment of the present invention. In the biological information measuring device 1 shown in the figure, the parameter set selection unit 207 receives the posture state estimated from the posture state estimation unit 205 and the absorbance ratio from the absorbance ratio calculation unit 204. It is different from the configuration in

For example, if the posture state estimation unit 205 estimates that the posture state is the lying state based on the detected posture state signal, the parameter set selection unit 207 selects the lying position corresponding to the lying position and the absorbance ratio. A parameter set (α _fix , β _fix , γ _Lying ) including the order parameter γ _Lying is selected and output to SpO2 calculation section 208 . Alternatively, the parameter set selection unit 207 selects the lying position parameter γ _Lying corresponding to the lying position state and the absorbance ratio, combines this with the fixed parameter set (α _fix , β _fix ), and generates a new parameter set (α _fix , β _fix , γ _Lying ).

Subsequently, the SpO2 calculation unit 208 of this embodiment calculates SpO2 using the following formula.
SpO2= _αfix + _βfix ×R+γ Equation 19
However, α _fix and β _fix are conventional fixed values (eg, α _fix =110, β _fix =25) that are linearly fitted to the region where the arterial blood oxygen saturation is 80 to 100%, and γ is the posture state. and a correction parameter according to the absorbance ratio or the like.
Thereby, the SpO2 calculation unit 208 calculates SpO2 according to the above formula based on the absorbance ratio (R) based on the detected biological signal and the selected parameter set (α _fix , β _fix , γ _Lying ).

Also, the biological information measuring instrument 1 may be configured with a parameter set estimating section 210 instead of the parameter set selecting section 207 as shown in the second embodiment. That is, parameter set estimating section 210 selects one or more parameters γ according to the estimated posture state, estimates optimal parameter γ from these parameters γ, and sets parameter set (α _fix , β _fix , γ) may be output to SpO2.

[Fifth embodiment]
In the present embodiment, immediately after a change in the posture state of the subject, taking into account the characteristic that the SpO2 value does not change or changes very slightly before and after the change, biometric information measurement for estimating the correction parameter γ An instrument and a measurement method using the same are described.

For example, it is assumed that the parameter set estimation unit 210 as shown in FIG. 7 is given a lying position state (tilt angle=0 degrees) as the posture state. The parameter set estimation unit 210, for example, the SpO2 value calculated when the posture state stored in the measurement result storage unit 209 is the lying position, the fixed parameter set (α _fix , β _fix ), and the detected Based on the absorbance ratio (R) calculated based on the biological signals thus obtained, the parameter γ is estimated when the posture state is the sitting state.

[Sixth embodiment]
In this embodiment, in addition to the posture state signal obtained from the motion sensor 14, the biometric signal obtained from the biosensor 12 is used to estimate the posture state, and the optimum parameter set corresponding to the estimated posture state is selected. Or, a biological information measuring device for estimation and a measuring method using the same will be described.

That is, upon receiving the biological signal output from the biological sensor 12, the biological signal receiving section 202 outputs the biological signal to the absorbance ratio calculating section 204 and the posture state estimating section 205, respectively. Also, upon receiving the posture state signal output from the motion sensor 14 , the posture state signal receiving section 203 outputs the posture state signal to each of the posture state estimating sections 205 . Thus, posture state estimation section 205 estimates the posture state of the subject based on the biomedical signal and the posture state signal.

As described above, the posture state of the subject can generally be estimated using the posture state signal from the motion sensor 14. For example, when comparing a standing position and a sitting position, either posture state signal from the inertial sensor alone can be used to estimate the subject's posture. It is difficult to estimate the posture state. On the other hand, the inventors have confirmed that the biological signal detected by the biological sensor 12 varies depending on the posture of the subject. Therefore, the posture state estimation unit 205, for example, tentatively estimates the posture state of the subject based on the posture state signal, and finally estimates the posture state of the temporarily estimated posture state based on the biological signal. configured to

As described above, according to the present embodiment, the posture state estimating unit 205 estimates the posture state using the biological signal obtained from the biosensor 12 in addition to the posture state signal obtained from the motion sensor 14. , a more accurate attitude state will be obtained, and therefore the selected parameter set will also be more accurate.

Each of the above embodiments is an example for explaining the present invention, and is not intended to limit the present invention only to these embodiments. The present invention can be embodied in various forms without departing from the gist thereof.

For example, in the above embodiment, a parameter set (α, β, γ) consisting of parameters α, β, and γ has been described, but the parameters are not limited to these parameters. For example, since the tendency of noise contained in the biosignal changes depending on the posture of the subject, a parameter set including parameters that take such noise into consideration may be used.

Also, for example, in the methods disclosed herein, steps, actions, or functions may be performed in parallel or in a different order without conflicting results. The steps, acts and functions described are provided as examples only and some of the steps, acts and functions may be omitted or combined together without departing from the scope of the invention. one, and other steps, operations, or functions may be added.

In addition, although various embodiments are disclosed in this specification, specific features (technical matters) in one embodiment may be added to other embodiments or Certain features in the embodiments can be substituted and such forms are included in the gist of the invention.

DESCRIPTION OF SYMBOLS 1... Biological information measuring instrument 10... Sensor part 12... Biological sensor 12a... PPG sensor 14... Motion sensor 14a... Inertial sensor 14b... Geomagnetic sensor 20... Control part 201... Sensor control part 202... Biosignal receiving part 203... Posture state signal Reception unit 204 Absorbance ratio calculation unit 205 Posture state estimation unit 206 Parameter set storage unit 207 Parameter set selection unit 208 SpO2 calculation unit 209 Measurement result storage unit 210 Parameter set estimation unit 30 User interface unit 40 Communication interface

Claims (11)

a biological signal acquisition unit that acquires a biological signal of a subject output from a biological sensor including a PPG sensor;
a posture state signal acquisition unit that acquires a posture state signal of the subject output from a motion sensor;
a posture state estimation unit that estimates the posture state of the subject based on the posture state signal acquired by the posture state signal acquisition unit;
an SpO2 calculation unit that calculates SpO2 in the subject's reference posture state based on the biosignal acquired by the biosignal acquisition unit and the posture state estimated by the posture state estimation unit;
The SpO2 calculation unit calculates the SpO2 by applying a parameter set corresponding to the estimated posture state to the absorbance ratio calculated based on the acquired biological signal.
Biological information measuring instrument. further comprising a parameter set storage unit that stores a plurality of parameter sets corresponding to a plurality of posture state models;
The biological information measuring device according to claim 1. further comprising a parameter set selection unit that selects one of the parameter sets corresponding to the estimated posture state from the parameter set storage unit;
The SpO2 calculator corrects the absorbance ratio based on the selected one predetermined parameter set.
The biological information measuring device according to claim 2. selecting one or more of the parameter sets corresponding to the estimated posture state from the parameter set storage unit, and estimating one parameter set by interpolation calculation based on the selected one or more of the parameter sets; further comprising a parameter set estimator for
The SpO2 calculation unit corrects the absorbance ratio based on the estimated one parameter set.
The biological information measuring device according to claim 2. The SpO2 calculation unit corrects the absorbance ratio by the interpolation calculation using a probability density function.
The biological information measuring device according to claim 4. The SpO2 calculation unit corrects the absorbance ratio by the interpolation calculation using a predetermined nonlinear function.
The biological information measuring device according to claim 4. further comprising a parameter set estimating unit that estimates a parameter set corresponding to a specific posture state and the absorbance ratio based on the estimated posture state;
The parameter set estimation unit stores the estimated parameter set in the parameter set storage unit.
The biological information measuring device according to claim 2. The posture state estimation unit estimates the posture state of the subject based on the biological signal output from the biological sensor.
The biological information measuring device according to claim 1. 9. The biological information measuring device according to claim 8, wherein said biological sensor includes at least one of a blood pressure sensor, an ECG sensor and an electromyographic sensor. The motion sensor includes at least one of a gravity sensor, an acceleration sensor, a gyro sensor, a geomagnetic sensor, a pressure sensor, an ultrasonic sensor, an infrared sensor, an image sensor, and a spectrum sensor.
The biological information measuring device according to claim 1. Acquiring a subject's biological signal output from a biological sensor including a PPG sensor;
obtaining a posture state signal of the subject output from a motion sensor;
estimating the posture state of the subject based on the acquired posture state signal;
calculating SpO2 in the subject's reference posture state based on the acquired biosignal and the estimated posture state;
Calculating the SpO2 includes calculating the SpO2 by applying a parameter set corresponding to the estimated posture state to an absorbance ratio calculated based on the acquired biological signal. ,
Biometric information measurement method.

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