Biological information measuring device, biological information measuring method, and biological information measuring program

Abstract

This enables a simple and easy assessment of the reliability of respiratory rate, without requiring a complex system configuration. [Solution] A biological information measuring device is configured comprising: a respiratory rate calculation unit 7c that calculates the respiratory rate of a subject by deriving a respiratory waveform, which is a periodic virtual waveform, from a photoplethysmography waveform obtained from the subject; a reliability data generation unit 7d that calculates the variance of the period or the variance of the amplitude of the respiratory waveform derived by the respiratory rate calculation unit 7c, and generates reliability data that quantifies the reliability of the respiratory rate calculation result by the respiratory rate calculation unit 7c based on the calculated variance; and a display output unit 6 that displays and outputs the reliability data generated by the reliability data generation unit 7d.

Description

Technical Field

[0005] , ,

[0001] The present disclosure relates to a biological information measurement device, a biological information measurement method, and a biological information measurement program.

Background Art

[0002] In recent years, with the increasing importance of biological information, a pulse oximeter, which is an example of a biological information measurement device, has been widely spreading. A pulse oximeter is a medical device that measures, for example, the arterial blood oxygen saturation (SpO2) of a subject without blood sampling through signal acquisition by the photoelectric plethysmogram method.

[0003] Regarding the waveform signal obtained from a subject by the photoelectric plethysmogram method (hereinafter sometimes referred to as "pulse wave" or "photoelectric plethysmogram waveform"), it is known that the respiratory rate of the subject can be calculated based on the photoelectric plethysmogram waveform (see, for example, Patent Document 1 and Non-Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In pulse oximeters that determine SpO2 and other parameters from pulse waves, it is conceivable to add a function to calculate respiratory rate based on those pulse waves. However, in that case, the respiratory rate would not be obtained by directly measuring it from the subject (but indirectly through calculation), so the reliability of that respiratory rate could become an issue. On the other hand, it is undesirable for reliability assessment to require a complex system configuration or for the convenience of the user to be compromised.

[0006] This disclosure provides a technology that enables simple reliability assessment of respiratory rate without requiring a complex system configuration, by generating reliability data that focuses on the periodic nature of respiration. [Means for solving the problem]

[0007] One aspect of this disclosure is, A respiratory rate calculation unit calculates the respiratory rate of a subject by deriving a periodic, virtual waveform called a respiratory waveform from a photoplethysmography waveform obtained from the subject, based on the photoplethysmography waveform obtained from the subject. A reliability data generation unit calculates the variance of the period or amplitude of the respiratory waveform derived by the respiratory rate calculation unit, and generates reliability data that quantifies the reliability of the respiratory rate calculation result by the respiratory rate calculation unit based on the calculated variance. A display output unit that displays and outputs the reliability data generated by the reliability data generation unit, It is a biological information measuring device equipped with [specific features / features].

[0008] Another aspect of this disclosure is, A respiratory rate calculation step involves calculating the respiratory rate of a subject by deriving a periodic, virtual waveform called a respiratory waveform from the photoplethysmography waveform obtained from the subject, based on the photoplethysmography waveform obtained from the subject. A reliability data generation step involves determining the variance of the period or amplitude of the respiratory waveform derived in the respiratory rate calculation step, and generating reliability data that quantifies the reliability of the respiratory rate calculation result by the respiratory rate calculation unit based on the determined variance. A display output step that displays and outputs the reliability data generated in the reliability data generation step, This is a biological information measurement method that includes [a specific feature / feature].

[0009] Another aspect of this disclosure is: On the computer, A respiratory rate calculation step involves calculating the respiratory rate of a subject by deriving a periodic, virtual waveform called a respiratory waveform from the photoplethysmography waveform obtained from the subject, based on the photoplethysmography waveform obtained from the subject. A reliability data generation step involves determining the variance of the period or amplitude of the respiratory waveform derived in the respiratory rate calculation step, and generating reliability data that quantifies the reliability of the respiratory rate calculation result by the respiratory rate calculation unit based on the determined variance. A display output step that displays and outputs the reliability data generated in the reliability data generation step, This is a biological information measurement program that performs the following actions. [Effects of the Invention]

[0010] According to this disclosure, when calculating the respiratory rate of a subject from a photoplethysmography waveform obtained from the subject, it becomes possible to easily determine the reliability of the respiratory rate without requiring a complex system configuration. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic external view of a pulse oximeter, which is a biological information measuring device according to one embodiment of the present disclosure, where (a) is a plan view, (b) is a front view seen from the fingertip insertion side, and (c) is a side view. [Figure 2] This is a block diagram showing the functional configuration of a pulse oximeter, which is a biological information measuring device according to one embodiment of the present disclosure. [Figure 3] This is an explanatory diagram showing a specific example of a waveform acquired by a pulse oximeter, which is a biological information measurement device according to one embodiment of this disclosure. [Modes for carrying out the invention]

[0012] Hereinafter, a biological information measuring device, a biological information measuring method, and a biological information measuring program according to the present disclosure will be described based on the drawings.

[0013] <1. Configuration of Biological Information Measuring Device> First, a configuration example of the biological information measuring device will be described.

[0014] The biological information measuring device is a medical device used to measure the biological information of a subject. In this embodiment, the subject is a human body having life, and the biological information is physiological information such as the pulse rate, blood oxygen saturation (SpO2), respiratory rate, etc. used as indicators for measuring the health status of the human body. The following description will be given by taking the case where the biological information measuring device is a pulse oximeter as an example. That is, in this embodiment, the biological information measuring device is configured as a pulse oximeter.

[0015] FIG. 1 is an external view schematically showing the pulse oximeter according to this embodiment, (a) is a plan view, (b) is a front view seen from the fingertip insertion side, and (c) is a side view. FIG. 2 is a block diagram showing the functional configuration of the pulse oximeter according to this embodiment.

[0016] As shown in FIG. 1, the pulse oximeter according to this embodiment includes a pair of upper and lower holding members 1 and 2, and these holding members 1 and 2 are arranged so as to face each other with the fingertip insertion portion 3 sandwiched therebetween. And the holding members 1 and 2 are configured to engage with each other so that relative displacement is possible in the direction of opening and closing the fingertip insertion portion 3 in a state biased by a spring member (not shown). With such a configuration, when the finger of the subject is inserted into the fingertip insertion portion 3, the inserted finger is sandwiched from both sides by the holding members 1 and 2 and held in that state.

[0017] One of the holding members 1 and 2 is provided with a light emitting unit 4 that irradiates light necessary for measuring biological information, and a light receiving unit 5 that receives the light. The light necessary for measuring biological information is, for example, infrared light and red light. In the example of FIG. 1, among the pair of upper and lower holding members 1 and 2, a so-called reflection type is shown in which both the light emitting unit 4 and the light receiving unit 5 are arranged on one of the holding members 2 on one side, but it is not necessarily limited to this. For example, a so-called transmission type in which the light emitting unit 4 and the light receiving unit 5 are arranged on separate holding members 1 and 2 may also be used.

[0018] In addition, on at least one outer surface of the holding members 1 and 2, a display output unit 6 for displaying and outputting various information including the measurement result of biological information is provided. As the display output unit 6, for example, a liquid crystal display panel can be considered, but it is not necessarily limited to this, and any other device can be used as long as it can visibly display and output various information.

[0019] Furthermore, in at least one housing of the holding members 1 and 2, a control unit 7 electrically connected to the light emitting unit 4, the light receiving unit 5, and the display output unit 6 is provided. The control unit 7 is for controlling the processing operation in a pulse oximeter, and is configured with hardware resources such as a combination of a CPU (Central Processing Unit) and various memory devices. That is, the control unit 7 is configured with hardware resources as a microcomputer, and the CPU executes a predetermined program stored in the memory, so that the predetermined program (software) and the hardware resources cooperate to control the processing operation in the pulse oximeter.

[0020] In the control unit 7, when the CPU executes a predetermined program, as shown in FIG. 2, it functions as at least a waveform acquisition unit 7a, an oxygen saturation measurement unit 7b, a respiration rate calculation unit 7c, and a reliability data generation unit 7d.

[0021] The waveform acquisition unit 7a is a function that acquires the photoplethysm waveform from the subject using the combination of the light-emitting unit 4 and the light-receiving unit 5. Details regarding the photoplethysm waveform and the acquisition method may be based on publicly known technology, and therefore will be omitted here.

[0022] The oxygen saturation measurement unit 7b has the function of measuring the subject's SpO2 based on the photoplethysmography waveform acquired by the waveform acquisition unit 7a. Details of the SpO2 measurement method based on the photoplethysmography waveform can be those of publicly known technology, and such explanations are omitted here.

[0023] The respiratory rate calculation unit 7c calculates the respiratory rate of a subject by deriving a respiratory waveform, which is a periodic virtual waveform, from the photoplethysmography waveform acquired by the waveform acquisition unit 7a. Details of the respiratory rate calculation method and other related matters can be based on publicly known technology, and will not be explained here.

[0024] The reliability data generation unit 7d is a function that generates reliability data that quantifies the reliability of the respiratory rate calculation result obtained by the respiratory rate calculation unit 7c. The reliability data and the method for generating it will be described in detail later.

[0025] The functions of the waveform acquisition unit 7a, oxygen saturation measurement unit 7b, respiratory rate calculation unit 7c, and reliability data generation unit 7d described above are realized by the predetermined program (software) stored in memory, which is configured with hardware resources as a microcomputer, and the CPU of the control unit 7 executes a predetermined program. In other words, the predetermined program that realizes these functions corresponds to one embodiment of the "biological information measurement program" according to this embodiment.

[0026] In that case, the predetermined programs that implement each function may be provided by being stored on a recording medium readable by the control unit 7 (e.g., magnetic disk, optical disk, magneto-optical disk, semiconductor memory, etc.), as long as they are installed in a way that the CPU of the control unit 7 can access them, or they may be provided from an external source via a network such as the Internet or a dedicated line.

[0027] <2. Procedure for measuring biological information> Next, we will describe an example of the processing operation in the pulse oximeter with the above configuration, that is, the procedure of the biological information measurement method according to this embodiment.

[0028] In this embodiment, a pulse oximeter attached to the finger of the subject is used to measure at least the subject's SpO2 and respiratory rate. The steps constituting the measurement procedure are described below.

[0029] Figure 3 is an explanatory diagram showing a specific example of a waveform acquired by a pulse oximeter according to this embodiment. In the figure, the horizontal axis represents elapsed time, and the vertical axis represents signal intensity.

[0030] (SpO2 measurement step) When using the pulse oximeter, first, insert the subject's finger into the fingertip insertion section 3, and then use the biasing force of the spring member to close the gap between the clamping members 1 and 2 to attach the pulse oximeter to the subject's finger. At this time, insert the finger as far as possible into the fingertip insertion section 3 so that the finger touches the light-emitting section 4 and the light-receiving section 5 of the pulse oximeter.

[0031] When the pulse oximeter is attached, the control unit 7 of the pulse oximeter starts the measurement process for SpO2, etc. The measurement process is carried out continuously from the time the pulse oximeter is attached until a predetermined time (for example, 1 minute) has elapsed.

[0032] Specifically, during the measurement process, the amount of light received by the light receiving unit 5 in response to the light emitted by the light emitting unit 4 is monitored. At this time, monitoring results are obtained for two wavelengths of light: infrared and red. As a result, the waveform acquisition unit 7a acquires the photoelectric pulse wave waveform for each of the two wavelengths.

[0033] Then, when the waveform acquisition unit 7a acquires two-wavelength photopulse wave waveforms, the oxygen saturation measurement unit 7b measures the subject's SpO2 based on, for example, the relationship between the ratios of each changing component (pulsation). The quantification of SpO2 based on the two-wavelength photopulse wave waveforms can be performed using publicly known techniques, and a detailed explanation of this is omitted here.

[0034] The SpO2 measurement results obtained in this manner are displayed on the display output unit 6. This allows the user of the pulse oximeter to visually confirm the SpO2 measurement results of the subject. In addition to SpO2, the pulse rate of the subject can also be measured from the photoelectric pulse wave waveform, so the display output unit 6 may also display the pulse rate measurement results together with the SpO2 measurement results.

[0035] (Respiratory rate calculation step) In this embodiment, the pulse oximeter's control unit 7 functions as a respiratory rate calculation unit 7c. That is, by calculating the respiratory rate using the respiratory rate calculation unit 7c, it is possible to determine the respiratory rate of the subject in addition to their SpO2. Furthermore, the respiratory rate can be added as an item to be displayed and output by the display output unit 6.

[0036] The respiratory rate calculation unit 7c calculates the respiratory rate by, for example, deriving a virtual respiratory waveform from the photoelectric pulse wave waveform acquired by the waveform acquisition unit 7a.

[0037] Specifically, as shown in Figure 3, for example, first, fluctuations in the amount of light received by the light receiving unit 5 at at least one wavelength during the measurement process are identified as pulse waves (photoelectric pulse wave waveforms) (see "Pulse Wave" in the figure). Then, the difference between the peak of each wave in the identified pulse wave and a hypothetically set baseline, and the difference between the bottom of the wave and the baseline are calculated, and these calculated differences are connected in a time series over the measurement process. The resulting waveform is used as a periodic, hypothetical breathing waveform (see "Breathing Waveform" in the figure).

[0038] After deriving a periodic virtual respiratory waveform, the respiratory rate calculation unit 7c analyzes the derived respiratory waveform, performs noise reduction and other processing, and then measures the number of times the subject breathed during the measurement period (e.g., 1 minute) from the waveform's fluctuations. The measured number is then used as the respiratory rate calculation result.

[0039] Furthermore, the method for calculating the respiratory rate does not necessarily have to be the one described above; other publicly known methods may also be used.

[0040] The respiratory rate calculation results obtained in this way are also displayed and output by the display output unit 6, similar to the SpO2 measurement results. This allows the pulse oximeter user to visually check the respiratory rate calculation results for the subject over a predetermined period of time (e.g., 1 minute).

[0041] (Reliability data generation step) As described above, in this embodiment, the pulse oximeter can display and output not only the subject's SpO2 but also the subject's respiratory rate.

[0042] However, the respiratory rate displayed is calculated by the respiratory rate calculation unit 7c based on the subject's pulse wave (photoelectric pulse wave waveform), and is not obtained by directly measuring the subject's respiration. In other words, unlike SpO2 and pulse rate, which can be directly identified from the subject's pulse wave, it is obtained indirectly through calculation processing in the control unit 7. Therefore, the reliability of the respiratory rate, or the degree to which it is reliable, may be a concern.

[0043] Therefore, in this embodiment, when the respiratory rate calculation unit 7c calculates the respiratory rate, the reliability data generation unit 7d generates reliability data based on the calculation result. The reliability data generated by the reliability data generation unit 7d quantifies the reliability of the respiratory rate calculation result by the respiratory rate calculation unit 7c and serves as an indicator for determining how reliable the respiratory rate calculation result is.

[0044] Reliability data can be generated by performing a statistical analysis on the respiratory waveform used as the basis for calculating the respiratory rate.

[0045] Specifically, first, the variance of the period or the variance of the amplitude of the respiratory waveform derived by the respiratory rate calculation unit 7c is determined. That is, by analysis of variance on the periodic respiratory waveform, the variation in the temporal magnitude of each period in the respiratory waveform is determined as the variance of the period of the respiratory waveform, and the variation in the amplitude of each period in the respiratory waveform is determined as the variance of the amplitude of the respiratory waveform. At least one of the period variance and the amplitude variance, preferably both, are determined. Any known technique can be used for determining the variance, and a detailed explanation is omitted here.

[0046] After determining the variance of the period or amplitude of the respiratory waveform, the determined variance is compared with a predetermined threshold. Through this comparison with the predetermined threshold, it is determined which of the multiple ranks defined by that threshold the determined variance falls into. This categorizes the degree of variance into one of the predetermined ranks. Each of these ranks is pre-assigned identification data to distinguish it.

[0047] After this ranking process, the identification data for the corresponding rank is extracted, and this extracted identification data is used as reliability data. Specifically, for example, the identification data for each rank, such as rank A, rank B, rank C, etc., or rank 1, rank 2, rank 3, etc., is used as reliability data that quantifies the reliability of the respiratory rate calculation results.

[0048] Thus, reliability data is generated in a way that allows for the identification of reliability levels, for example, through ranking. While this example uses ranking to quantify reliability, it is not necessarily limited to this method. Any method that allows for the quantification of reliability as an indicator, such as quantifying the calculated variance, is also acceptable.

[0049] The reliability data generated in this manner, along with the respiratory rate calculation results, is displayed and output by the display output unit 6.

[0050] <3. Effects of this embodiment> According to this embodiment, one or more of the following effects are achieved.

[0051] (a) In this embodiment, the respiratory rate of a subject is calculated from the photoplethysmography waveform, and at the same time, reliability data is generated that quantifies the reliability of the respiratory rate calculation result by determining the variance of the period or the variance of the amplitude of the respiratory waveform on which the calculation was based, and this reliability data is displayed and output. As a result, the user of the pulse oximeter can refer to the reliability data when looking at the respiratory rate calculation result displayed on the display output unit 6, and objectively judge how reliable the result is, using the reliability data as an indicator.

[0052] Therefore, according to this embodiment, by objectively determining the reliability of the respiratory rate calculation results, it becomes possible to infer the usage status of the pulse oximeter and, if necessary, to perform remeasurement using the pulse oximeter, making it extremely convenient for pulse oximeter users.

[0053] Furthermore, the reliability data displayed and output is generated by the pulse oximeter's control unit 7 using the variance of the period or amplitude of the respiratory waveform. Respiratory waveforms are generally repeating waveforms with regular periods and amplitudes. Therefore, by focusing on the variance of the period or amplitude and generating reliability data using that variance, the reliability data can be generated with a processing load that can be handled by the pulse oximeter's control unit 7 without requiring complex information processing. In addition, by utilizing the variance, it becomes easy to improve the appropriateness and accuracy of the generated reliability data. In this way, by utilizing the variance of the period or amplitude of the respiratory waveform, reliability data can be generated appropriately without requiring a complex system configuration other than the pulse oximeter.

[0054] In other words, according to this embodiment, when calculating the respiratory rate of a subject from the photoplethysmography waveform obtained from the subject, it becomes possible to easily determine the reliability of the respiratory rate without requiring a complex system configuration.

[0055] (b) In this embodiment, reliability data is generated in a way that allows the degree of reliability to be identified by ranking. Therefore, according to this embodiment, when determining the reliability of the respiratory rate calculation result, it is possible to make a judgment based on the rank shown as reliability data. In other words, for pulse oximeter users, the reliability of the respiratory rate can be easily and accurately determined without requiring complicated numerical inquiries, making it extremely convenient.

[0056] (c) In this embodiment, the biological information measuring device is configured as a pulse oximeter, and the pulse oximeter displays and outputs not only SpO2 but also respiratory rate in a manner that allows for reliability assessment. Therefore, according to this embodiment, users can use it easily, and even in that case, appropriate reliability judgments are made regarding the displayed output results, making it extremely convenient in that respect.

[0057] <4. Variation> Although embodiments of this disclosure have been described in detail above, this disclosure is not limited to the embodiments described above, and various modifications are possible without departing from its essence.

[0058] In the embodiments described above, the biological information measuring device was a fingertip-type pulse oximeter, and the biological information measured was primarily SpO2. However, the invention is not necessarily limited to this. For example, an earlobe-type pulse oximeter can be used in exactly the same way. Furthermore, if the device utilizes the photoelectric pulse wave waveform obtained from the subject, it can be used in exactly the same way with other types of biological information measuring devices (for example, those configured using a general-purpose computer device) instead of a pulse oximeter. The same applies to the biological information; it can be other types of biological information besides SpO2.

[0059] Furthermore, while the above-described embodiment uses a case where the reliability data for the respiratory rate calculation result is based on ranking, it is not necessarily limited to this. The reliability data may be based on other types of data (for example, numerical representations of variance) rather than ranking, as long as the degree of reliability is identifiable. [Explanation of Symbols]

[0060] 2... Clamping member, 3... Fingertip insertion part, 4... Light-emitting part, 5... Light-receiving part, 6... Display output part, 7... Control unit, 7a... Waveform acquisition part, 7b... Oxygen saturation measurement part, 7c... Respiratory rate calculation part, 7d... Reliability data generation part

Claims

1. A respiratory rate calculation unit calculates the respiratory rate of a subject by deriving a periodic, virtual waveform called a respiratory waveform from a photoplethysmography waveform obtained from the subject, based on the photoplethysmography waveform obtained from the subject. A reliability data generation unit calculates the variance of the period or amplitude of the respiratory waveform derived by the respiratory rate calculation unit, and generates reliability data that quantifies the reliability of the respiratory rate calculation result by the respiratory rate calculation unit based on the calculated variance. A display output unit that displays and outputs the reliability data generated by the reliability data generation unit, A biological information measuring device equipped with the following features.

2. The aforementioned reliability data allows for the identification of the degree of reliability through ranking. A biological information measuring device according to claim 1.

3. It is configured as a pulse oximeter. A biological information measuring device according to claim 1 or 2.

4. A respiratory rate calculation step involves calculating the respiratory rate of a subject by deriving a periodic, virtual waveform called a respiratory waveform from a photoplethysmography waveform obtained from the subject, based on the photoplethysmography waveform obtained from the subject. A reliability data generation step involves determining the variance of the period or amplitude of the respiratory waveform derived in the respiratory rate calculation step, and generating reliability data that quantifies the reliability of the respiratory rate calculation result by the respiratory rate calculation unit based on the determined variance. A display output step that displays and outputs the reliability data generated in the reliability data generation step, A method for measuring biological information, comprising the following features.

5. On the computer, A respiratory rate calculation step involves calculating the respiratory rate of a subject by deriving a periodic, virtual waveform called a respiratory waveform from a photoplethysmography waveform obtained from the subject, based on the photoplethysmography waveform obtained from the subject. A reliability data generation step involves determining the variance of the period or amplitude of the respiratory waveform derived in the respiratory rate calculation step, and generating reliability data that quantifies the reliability of the respiratory rate calculation result by the respiratory rate calculation unit based on the determined variance. A display output step that displays and outputs the reliability data generated in the reliability data generation step, A biometric information measurement program that performs the following actions.

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