pulse oximeter

Abstract

This pulse oximeter offers high accuracy in measuring oxygen saturation and is suitable for measuring the oxygen saturation drop index. [Solution] The pulse oximeter 1 includes a saturation measurement unit 21 that measures the blood oxygen saturation of a subject 9 using a red light sensor 12 and an infrared light sensor 13 and converts it into a group of measurement data 211, a detection index calculation unit 22 that calculates a detection index 226, and an abnormal value detection unit 23 that detects an abnormal value 231 of oxygen saturation based on the detection index 226. The detection index calculation unit 22 calculates at least one of the following as the detection index 226: a green-red signal ratio 224, which is the ratio of the green light pulse wave signal intensity ratio 221 of the detection signal from the green light sensor 11 and the red light pulse wave signal intensity ratio 222 of the detection signal from the red light sensor 12; and a green-infrared signal ratio 225, which is the ratio of the green light pulse wave signal intensity ratio 221 and the infrared light pulse wave signal intensity ratio 223 of the detection signal from the infrared light sensor 13.

Description

Technical Field

[0001] The present invention relates to a pulse oximeter.

Background Art

[0002] A pulse oximeter measures the arterial oxygen saturation (SpO2) by irradiating the finger with red light and a near-infrared light source and detecting the light transmitted through the finger (see Patent Document 1). When performing an examination of the oxygen saturation decrease index, which is an indicator of sleep apnea syndrome, the arterial oxygen saturation of a subject during sleep is measured using a pulse oximeter.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When measuring the arterial oxygen saturation of a subject during sleep, when the subject takes a specific posture, there is a problem that although the detection state of the photoelectric pulse wave of the detection light is normal in the pulse oximeter, the oxygen saturation measured from the photoelectric pulse wave shows a low abnormal value. Examples of the specific posture include a posture in which the subject lies supine on a high bed and the fingertips hang downward from the supine height. When measuring the oxygen saturation with a pulse oximeter worn on the wrist in such a posture, it may show a low abnormal value compared to the measurement value in a normal posture where the arm is not hanging down. <000002​​​​

[0005] A pulse oximeter according to a first aspect of this disclosure includes: a green light sensor that detects green light transmitted or reflected from a subject after irradiating the subject with green light; a red light sensor that detects red light transmitted or reflected from a subject after irradiating the subject with red light; an infrared light sensor that detects infrared light transmitted or reflected from a subject after irradiating the subject with infrared light; and a control device that processes the detection signals of the green light sensor, the red light sensor, and the infrared light sensor, wherein the control device includes a saturation measurement unit that generates a group of measurement data indicating the oxygen saturation of the subject from the detection signals of the red light sensor and the infrared light sensor, and the detection signals of the green light sensor, the red light sensor, and the infrared light sensor The system comprises a detection index calculation unit that calculates a ratio of the following as a detection index, and an abnormal value detection unit that detects an abnormal value of the oxygen saturation based on the detection index, wherein the detection index calculation unit calculates at least one of the following as the detection index: a green light pulse wave signal intensity ratio, which is the ratio of the amplitude of the vibration component in the detection signal output by the green light sensor to the signal intensity of the detection signal; a red light pulse wave signal intensity ratio, which is the ratio of the amplitude of the vibration component in the detection signal output by the red light sensor to the signal intensity of the detection signal; and a green infrared signal ratio, which is the ratio of the green light pulse wave signal intensity ratio and an infrared light pulse wave signal intensity ratio, which is the ratio of the amplitude of the vibration component in the detection signal output by the infrared light sensor to the signal intensity of the detection signal.

[0006] A pulse oximeter according to a second aspect of this disclosure includes: a green light sensor that detects green light transmitted or reflected from a subject after irradiating the subject with green light; a red light sensor that detects red light transmitted or reflected from a subject after irradiating the subject with red light; an infrared light sensor that detects infrared light transmitted or reflected from a subject after irradiating the subject with infrared light; a control device that processes the detection signals from the green light sensor, the red light sensor, and the infrared light sensor; and a display unit that displays information obtained by the control device, wherein the control device is A set of measurement data indicating the oxygen saturation of the subject is generated from the detection signals of the red light sensor and the infrared light sensor, an abnormality detection index in the set of measurement data is calculated from the detection signals of the green light sensor, the red light sensor, and the infrared light sensor, the set of measurement data and the detection index are displayed on the display unit on the same time axis, a predetermined threshold for the detection index is displayed on the display unit, and the range in which the detection index exceeds the threshold and the range in which it falls below the threshold are displayed in different display modes within the set of measurement data displayed on the display unit.

[0007] A pulse oximeter according to a third aspect of this disclosure includes: a green light sensor that detects green light transmitted or reflected by a subject after irradiating the subject with green light; a red light sensor that detects red light transmitted or reflected by a subject after irradiating the subject with red light; an infrared light sensor that detects infrared light transmitted or reflected by a subject after irradiating the subject with infrared light; a control device that processes the detection signals of the green light sensor, the red light sensor, and the infrared light sensor; and a display unit that displays information obtained by the control device. The control device generates a group of measurement data indicating the oxygen saturation of the subject from the detection signals of the red light sensor and the infrared light sensor, calculates an abnormality detection index in the group of measurement data from the detection signals of the green light sensor, the red light sensor, and the infrared light sensor, displays the group of measurement data on the display unit, and issues an alert regarding the posture of the subject when the detection index exceeds a predetermined threshold. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram showing a pulse oximeter according to one embodiment of the present disclosure. [Figure 2] A schematic diagram showing the usage state of the pulse oximeter according to the above embodiment. [Figure 3] A block diagram showing the control device for the pulse oximeter according to the above embodiment. [Figure 4] A graph showing the detection signal in the above embodiment. [Figure 5] A graph showing the normal oxygen saturation and the ratio of each color pulse wave signal intensity in the above embodiment. [Figure 6] A graph showing the normal oxygen saturation, green-red signal ratio, and green-infrared signal ratio in the above embodiment. [Figure 7] A graph showing the oxygen saturation and the signal intensity ratio of each color pulse wave during abnormal conditions in the above embodiment. [Figure 8] A graph showing the oxygen saturation, green-red signal ratio, and green-infrared signal ratio during abnormal conditions in the above embodiment. [Figure 9] A graph showing a set of corrected data with abnormal values ​​removed from the above embodiment. [Figure 10] A graph showing a set of corrected data obtained by interpolating the portion of the above embodiment in which abnormal values ​​were removed. [Figure 11] A schematic diagram showing the display screen in the above embodiment. [Figure 12] A flowchart illustrating the process in the above embodiment. [Figure 13] A schematic diagram illustrating another embodiment of the present invention. [Modes for carrying out the invention]

[0009] An embodiment of this disclosure will be described below. In Figures 1 and 2, the pulse oximeter 1 has a sensor unit 10 and a control device 20. The sensor unit 10 and the control device 20 are housed in a case 2, and a display unit 30 is connected to the control device 20.

[0010] The sensor unit 10 is positioned on the surface of the case 2 and is held in close contact with the subject 9, such as the user's fingers, during measurement. The sensor unit 10 is equipped with a green light source 111, a red light source 112, an infrared light source 113, and a photodetector 110. The green light source 111, the red light source 112, and the infrared light source 113 are, for example, LEDs (light-emitting diodes) or laser diodes. Preferably, the emission wavelength of the green light source 111 is 500nm to 600nm, the emission wavelength of the red light source 112 is 600nm to 800nm, and the emission wavelength of the infrared light source 113 is 800nm ​​to 1000nm. The photodetector 110 is, for example, a silicon photodiode. The green light source 111, red light source 112, infrared light source 113, and photodetector 110 of the sensor unit 10 are covered on their surfaces with a cover (not shown) made of a transparent resin molded plate such as acrylic or polycarbonate.

[0011] In the sensor unit 10, the green light source 111, the red light source 112, and the infrared light source 113 each emit light sequentially under the control of the control device 20, and the light rays from each are reflected by the subcutaneous tissue of the subject 9 and returned to the photodetector 110. The control device 20 acquires the detection signals from the photodetector 110 as a detection signal for green light, a detection signal for red light, and a detection signal for infrared light, based on the light emission timing of each light-emitting element. The green light source 111 and the photodetector 110 constitute the green light sensor 11, the red light source 112 and the photodetector 110 constitute the red light sensor 12, and the infrared light source 113 and the photodetector 110 constitute the infrared light sensor 13. The sensor unit 10 further includes an acceleration sensor 14 installed inside the case 2.

[0012] The control device 20 is composed of a small computer system and includes a memory for storing various data, and a processor that executes programs stored in the memory to realize the intended function (see Figure 3). In Case 2, in addition to storing a battery that powers the sensor unit 10 and the control device 20, input / output terminals of the control device 20 and the like are provided (not shown).

[0013] The display unit 30 is connected to the control device 20 by signal means, either wired or wireless, and can display measurement results and the like by the control device 20. As the display unit 30, for example, in addition to a general-purpose image display panel, a portable information terminal such as a so-called smartphone can be used.

[0014] In FIG. 3, the control device 20 functions as a saturation measurement unit 21, a detection index calculation unit 22, an abnormal value detection unit 23, a measurement data processing unit 24, and a display control unit 25 when a processor executes a program.

[0015] The saturation measurement unit 21 controls the green light sensor 11, the red light sensor 12, and the infrared light sensor 13 of the sensor unit 10 connected to the control device 20, and acquires (receives) a detection signal. The saturation measurement unit 21 measures the blood oxygen saturation of the subject 9 from the detection signals of the red light sensor 12 and the infrared light sensor 13, and records it in the memory as a measurement data group 211. The detection signals of the red light sensor 12 and the infrared light sensor 13 are photoplethysmogram signals based on the red light and infrared light transmitted through the subcutaneous tissue of the subject 9, and the saturation measurement unit 21 measures the oxygen saturation from the pulse signals of the red light and infrared light, and records it in the memory as a measurement data group 211.

[0016] The detection index calculation unit 22 is connected to the detection signals of the same green light sensor 11, the red light sensor 12, and the infrared light sensor 13 as those of the saturation measurement unit 21. The detection index calculation unit 22 calculates the respective pulse signal intensity ratios (2, 222, 223) for the detection signals of the green light sensor 11, the red light sensor 12, and the infrared light sensor 13.[[ID=X]] In Figure 4, the detection signal for each color is a pulse wave with a DC component superimposed on an Oscillating component. The amplitude signal strength AC is detected from the amplitude of the Oscillating component, and the DC signal strength DC is detected at the center of the amplitude. Once the amplitude signal strength AC and DC signal strength DC are obtained, the pulse wave signal strength ratio of the detected signal can be obtained by the ratio AC / DC of the amplitude signal strength AC to the DC signal strength DC. Based on these, the green light pulse wave signal intensity ratio 221, which is the pulse wave signal intensity ratio (ratio AC / DC) of the detection signal from the green light sensor 11, the red light pulse wave signal intensity ratio 222, which is the pulse wave signal intensity ratio of the detection signal from the red light sensor 12, and the infrared light pulse wave signal intensity ratio 223, which is the pulse wave signal intensity ratio of the detection signal from the infrared light sensor 13 are calculated.

[0017] The detection index calculation unit 22 uses the obtained pulse wave signal intensity ratios for each color to calculate the green-red signal ratio 224, which is the ratio of the green light pulse wave signal intensity ratio 221 to the red light pulse wave signal intensity ratio 222, and the green-infrared signal ratio 225, which is the ratio of the green light pulse wave signal intensity ratio 221 to the infrared light pulse wave signal intensity ratio 223. For a green-red signal ratio of 224, the ratio of the red light pulse wave signal intensity ratio ACr / DCr to the green light pulse wave signal intensity ratio ACg / DCg is calculated as Rrg = (ACr / DCr) / (ACg / DCg). For a green-infrared signal ratio of 225, the ratio of the infrared pulse wave signal intensity ratio ASi / DCi to the green pulse wave signal intensity ratio ACg / DCg is calculated as Rig = (ACi / DCi) / (ACg / DCg). The detection index calculation unit 22 uses at least one of the green-red signal ratio 224 and the green-infrared signal ratio 225 as the detection index 226. The detection index 226 may be either the specified green-red signal ratio 224 or the green-infrared signal ratio 225, the larger or smaller of the two, or the sum or average of both.

[0018] The abnormal value detection unit 23 detects abnormal values ​​231 (see Figures 7 and 8) that appear in the measurement data group 211 based on the detection index 226. The abnormal value detection unit 23 refers to the time-dependent change in the detection index 226, detects data fluctuations that occur when the subject 9 is in a specific posture, and determines that an abnormality has occurred in the oxygen saturation measurement by the saturation measurement unit 21. Then, it detects the measurement data group 211 for the period in which an abnormality has been determined as an abnormal value 231. The detection process will be described in detail later with reference to Figures 5 to 8.

[0019] The measurement data processing unit 24 removes the abnormal values ​​231 detected by the abnormal value detection unit 23 from the measurement data group 211, and then connects the removed portion with interpolated data 241 to create a corrected data group 242. Any data interpolation method, such as linear interpolation or spline interpolation, can be used for the data interpolation process. The processing performed by the measurement data processing unit 24 will be described in detail later with reference to Figures 9 and 10.

[0020] The display control unit 25 displays various data obtained by the control device 20 on the display unit 30. The display content may include the corrected data group 242 obtained by the measurement data processing unit 24, the original measurement data group 211 obtained by the saturation measurement unit 21, and the detection index 226 (green-red signal ratio 224 or green-infrared signal ratio 225), and alerts based on these may also be displayed. Furthermore, based on the detection index 226, the unit may calculate the intervals in which oxygen saturation decreased over a predetermined period of time (intervals T1, T2, etc.) or the number of times oxygen saturation decreased, and display the calculation results on the display unit 30. The display by the display control unit 25 will be described in detail later with reference to Figure 11.

[0021] [Detection of abnormal values] Next, we will explain in more detail how the detection index calculation unit 22 detects abnormal values. Figures 5 and 6 show the measurement data set 211 for normal oxygen saturation, the pulse wave signal intensity ratios for each color light (221, 222, 223), the green-red signal ratio 224, and the green-infrared signal ratio 225. In Figure 5, the measurement data group 211 is oxygen saturation data acquired by the saturation measurement unit 21. Although there are occasional decreases in oxygen saturation, the values ​​are basically within a constant range. The green light pulse wave signal intensity ratio 221 and the infrared light pulse wave signal intensity ratio 223 both show an upward trend, but the data fluctuations are small. The red light pulse wave signal intensity ratio 222 shows an upward trend, but also exhibits fluctuations that correlate with the decrease in oxygen saturation in the measurement data group 211.

[0022] In Figure 6, a green-red signal ratio of 224 mitigates the upward trend observed in green pulse wave signal intensity ratios of 221 and red pulse wave signal intensity ratios of 222, and also suppresses fluctuations due to decreased oxygen saturation. A green-infrared signal ratio of 225 mitigates the upward trend and fluctuations observed in infrared pulse wave signal intensity ratio 223. Thus, under normal circumstances, each data point shows nearly continuous values, and no unusual fluctuations are observed.

[0023] Figures 7 and 8 show the measurement data set 211 for normal oxygen saturation, the pulse wave signal intensity ratios for each color light (221, 222, 223), the green-red signal ratio 224, and the green-infrared signal ratio 225. In Figure 7, the measurement data group 211 is basically within a constant numerical range, but there are outlier values ​​231 in intervals T1 and T2 where the values ​​have dropped significantly. The green light pulse wave signal intensity ratio of 221 is slightly lower than normal in intervals T1 and T2. The red pulse wave signal intensity ratio of 222 is significantly higher than normal in intervals T1 and T2. The infrared pulse wave signal intensity ratio of 223 shows no change in intervals T1 and T2.

[0024] Possible causes of the abnormal value 231 in measurement data group 211 include a temporary decrease in blood flow to the detection site due to compression caused by a change in the posture of the subject 9. Furthermore, if the green light sensor 11, the red light sensor 12, and the infrared light sensor 13 detect the limbs of the subject 9, and the limbs that are the target of detection of the subject 9 while the subject 9 is lying supine are hanging down below the torso of the subject 9, or the limbs that are the target of detection of the subject 9 while the subject 9 is lying supine are being pinned under other parts of the subject 9, then the blood flow of the subject may be compressed. Alternatively, if the green light sensor 11, the red light sensor 12, and the infrared light sensor 13 detect the head of the subject 9, and the blood vessels in the neck of the subject 9 are compressed, this can also be considered a state of compression of the subject's blood flow. Unlike the decrease in oxygen saturation that should be measured, abnormal values ​​of 231 caused by these factors tend to appear continuously.

[0025] In Figure 8, the values ​​for the green-red signal ratio of 224 and the green-infrared signal ratio of 225 are significantly higher than normal in intervals T1 and T2, respectively. In particular, the green pulse wave signal intensity ratio 221 is low and the red pulse wave signal intensity ratio 222 is high in intervals T1 and T2, and both show a change, making the change in values ​​at the end of the interval for the green-red signal ratio 224 even clearer. Thus, during abnormal conditions, a clear change is observed in the green-red signal ratio 224 or the green-infrared signal ratio 225 used as the detection index 226. Therefore, the detection index calculation unit 22 can identify the intervals T1 and T2 in which the abnormal value 231 occurred by detecting these green-red signal ratios 224 or green-infrared signal ratios 225. The detection index calculation unit 22 can use a predetermined threshold L to identify intervals T1 and T2. When using the green-red signal ratio 224 or the green-infrared signal ratio 225 as the detection index 226, a threshold L larger than the normal values ​​for each can be set, and when this threshold L is exceeded, it can be determined to be an abnormal value 231.

[0026] [Data processing and display processing] Next, the data processing performed by the measurement data processing unit 24 and the display control performed by the display control unit 25 will be explained in more detail. Figures 9 and 10 show the removal or interpolation of abnormal values ​​231 by the measurement data processing unit 24. In Figure 9, the measurement data processing unit 24 deletes the data for intervals T1 and T2 in the measurement data group 211 based on the abnormal value 231 detected by the abnormal value detection unit 23. In Figure 10, the measurement data processing unit 24 interpolates the intervals T1 and T2 in the measurement data group 211 where data has been deleted using interpolated data 241, and the measurement data group 211 interpolated with the interpolated data 241 is designated as the corrected data group 242.

[0027] Figure 11 illustrates a display screen 31 displayed on the display unit 30 by the display control unit 25. The display screen 31 shows, along the time axis 32 displayed at the bottom, an oxygen saturation graph 33 showing the corrected data group 242 generated by the measurement data processing unit 24, a detection index graph 34 showing the detection index 226 (green-red signal ratio 224 or green-infrared signal ratio 225) used by the abnormal value detection unit 23, and a threshold display 35 showing the threshold L for determining the abnormal value 231. The oxygen saturation graph 33 may also display an anomaly value graph 331 showing anomaly values ​​231 in intervals T1 and T2, and an interpolated data graph 332 showing interpolated data 241. On both sides of the display screen 31, a vertical axis display 36 showing the values ​​of the oxygen saturation graph 33 and the detection index graph 34 is displayed.

[0028] The oxygen saturation graph 33, the detection index graph 34, the anomaly value graph 331, the interpolated data graph 332, and the vertical axis display 36 are each displayed in different display modes that are easy to distinguish, such as different display modes for saturation, brightness, transparency, line type, etc., or combinations thereof. In particular, the oxygen saturation graph 33 displays the intervals T1 and T2, i.e., the range where the detection index 226 exceeds the threshold L, and the range outside of intervals T1 and T2 where the detection index falls below the threshold L, using different display modes, such as different saturation, brightness, transparency, line type, or combinations thereof. Among these, the anomaly value graph 331 and interpolated data graph 332 displayed in intervals T1 and T2 may be displayed in gray, which has lower identifiability than other parts. The threshold indicator 35 showing the threshold L is not limited to a straight line; it may also be displayed by a mark or shape added to a part of the display of the detection index 226.

[0029] The display screen 31 may show the original measurement data group 211 in addition to the corrected data group 242, and may also display alerts about the posture of the subject 9 based on the detection index 226 (green-red signal ratio 224 or green-infrared signal ratio 225). The alert display may also be an audible alarm. Data from the measurement data group 211 that have been determined to be abnormal values ​​231 (abnormal value graph 331) have been excluded from the corrected data group 242 and may be excluded from alerts. Furthermore, based on the detection index 226, the system may calculate the intervals in which oxygen saturation decreased over a predetermined period of time (e.g., intervals T1, T2), or the number of times oxygen saturation decreased, and display the calculation results on the display unit 30.

[0030] [Pulse oximeter operation] Figure 12 shows an overview of the processing performed by the pulse oximeter 1 of this embodiment. In the pulse oximeter 1, the processor of the control device 20 executes a program, which causes the following processes to be performed by the sensor unit 10 and the control device 20. In process S1, the sensor unit 10 irradiates the subject 9 with green light, red light, and infrared light and detects the green light, red light, and infrared light that have been transmitted through or reflected from the subject 9. In process S2, the saturation measurement unit 21 measures the oxygen saturation of the subject 9 from the detection signals of red light and infrared light, and records it as a group of measurement data 211 (see Figures 5 and 6). In processing S3, the detection index calculation unit 22 calculates the pulse wave signal intensity ratios (221, 222, 223) for each color of light from the detection signals of green light, red light, and infrared light, and further calculates the green-red signal ratio 224 and the green-infrared signal ratio 225, and uses one of them as the detection index 226. In process S4, the abnormal value detection unit 23 detects an abnormal value 231 that appears in the measurement data group 211 based on the detection index 226 (see Figures 7 and 8). In processing S5, the measurement data processing unit 24 removes the data of abnormal values ​​231 from the measurement data group 211 (see Figure 9), and then interpolates the portion from which the data was removed with interpolated data 241 to generate a corrected data group 242 (see Figure 10). In process S6, the display control unit 25 displays the correction data group 242 and the detection index 226 on the display unit 30 (see Figure 11).

[0031] In the pulse oximeter 1 of this embodiment, whether or not it is functioning normally can be confirmed by the following operation. A film or sheet capable of suppressing the transmission of light at the inspection wavelengths of the green light sensor 11, the red light sensor 12, and the infrared light sensor 13 is prepared and placed between the sensor part 10 of the pulse oximeter 1 and the subject 9 for measurement. When pulse oximeter 1 detects a green-red signal ratio of 224, the ability to detect abnormal posture of subject 9 is impaired when a film that suppresses red light is placed between the pulse oximeter and the subject 9. However, the function is restored when the film is removed. When pulse oximeter 1 detects a green-infrared signal ratio of 225, the ability to detect abnormal posture of subject 9 is impaired when an infrared light-suppressing film is placed between the oximeter and the subject 9. However, the function is restored when the film is removed. When a film that suppresses green light is inserted, the pulse oximeter 1's ability to detect abnormal posture of the subject 9 is impaired, regardless of whether it is using a green-red signal ratio of 224 or a green-infrared signal ratio of 225. However, the function is restored by removing the film. In this way, the function of the pulse oximeter 1 can be determined by blocking the inspection light.

[0032] [Effects of this embodiment] The pulse oximeter 1 of this embodiment includes a green light sensor 11 that detects green light transmitted or reflected from a subject 9 when green light is irradiated onto the subject 9, a red light sensor 12 that detects red light transmitted or reflected from a subject 9 when red light is irradiated onto the subject 9, an infrared light sensor 13 that detects infrared light transmitted or reflected from a subject 9 when infrared light is irradiated onto the subject 9, and a control device 20 that processes the detection signals of the green light sensor 11, the red light sensor 12, and the infrared light sensor 13. The control device 20 includes a saturation measurement unit 21 that generates a group of measurement data 211 indicating the oxygen saturation of the subject 9 from the detection signals of the red light sensor 12 and the infrared light sensor 13, and calculates the ratio of the detection signals of the green light sensor 11, the red light sensor 12, and the infrared light sensor 13 as a detection index 226. The system comprises a detection index calculation unit 22 and an abnormal value detection unit 23 that detects an abnormal value 231 of oxygen saturation based on the detection index 226. The detection index calculation unit 22 calculates at least one of the following as the detection index 226: a green light pulse wave signal intensity ratio 221, which indicates the ratio of the amplitude of the vibration component in the detection signal output by the green light sensor 11 to the signal intensity of the detection signal; a red light pulse wave signal intensity ratio 222, which indicates the ratio of the amplitude of the vibration component in the detection signal output by the red light sensor 12 to the signal intensity of the detection signal; a green-red signal ratio 224, which is the ratio of the green light pulse wave signal intensity ratio 221 to the signal intensity of the detection signal; and a green-infrared signal ratio 225, which is the ratio of the green light pulse wave signal intensity ratio 221 to the signal intensity of the detection signal; and an infrared light pulse wave signal intensity ratio 223, which indicates the ratio of the amplitude of the vibration component in the detection signal output by the infrared light sensor 13 to the signal intensity of the detection signal.

[0033] In such a pulse oximeter 1, a group of measurement data 211 of the blood oxygen saturation of the subject 9 is obtained by the red light sensor 12, the infrared light sensor 13, and the saturation measurement unit 21 of the control device 20. In addition, a detection index calculation unit 22 calculates a detection index 226. Based on the detection index 226, the abnormal value detection unit 23 detects an abnormal value 231 in the measurement data group 211, thereby eliminating measurement errors caused by the subject 9's body movement and improving measurement accuracy. The detection index 226 is calculated based on the ratio of the detection signals from the green light sensor 11, the red light sensor 12, and the infrared light sensor 13. In processing the detection signals from each color light sensor (11, 12, 13), the ratio of the signal intensity of each color light pulse wave (221, 222, 223), that is, the ratio of the amplitude of the vibration component in the detection signal output by each sensor to the signal intensity of the detection signal, is used to relativize the rate of change of the vibration component of each detection signal, making it a suitable value for comparison. The detection index 226 uses at least one of the following: the green-red signal ratio 224, which is the ratio of the green light pulse wave signal intensity ratio 221 to the red light pulse wave signal intensity ratio 222; and the green-infrared signal ratio 225, which is the ratio of the green light pulse wave signal intensity ratio 221 to the infrared light pulse wave signal intensity ratio 223. Green light, which is used in common for the green-red signal ratio 224 and the green-infrared signal ratio 225, is easily absorbed by hemoglobin in the blood, and the detection signal of the green light sensor 11 indicates the amount of hemoglobin in the blood. During sleep, oxygen saturation decreases due to shallow breathing caused by sleep apnea syndrome. Even if oxygen saturation decreases due to sleep apnea syndrome, if there is no change in blood flow, there will be no change in the detection signal of the green light sensor 11. On the other hand, if blood flow is suppressed due to a change in the posture of the subject 9, the detection signal of the green light sensor 11 decreases in accordance with the decrease in hemoglobin flow. Therefore, by using at least one of the green-red signal ratio 224 and the green-infrared signal ratio 225 as the detection index 226, abnormal values ​​caused by the subject's body movement can be detected.

[0034] The pulse oximeter 1 of this embodiment includes a green light sensor 11 that detects green light transmitted or reflected from a subject 9 when green light is irradiated onto the subject 9, a red light sensor 12 that detects red light transmitted or reflected from a subject 9 when red light is irradiated onto the subject 9, an infrared light sensor 13 that detects infrared light transmitted or reflected from a subject 9 when infrared light is irradiated onto the subject 9, a control device 20 that processes the detection signals from the green light sensor 11, the red light sensor 12, and the infrared light sensor 13, and a display unit 30 that displays the information obtained by the control device 20. The control device 20 processes the detection signals from the red light sensor 12 and the infrared light The system generates a group of measurement data 211 showing the oxygen saturation of the subject 9 from the detection signal of the sensor 13, calculates a detection index 226 for abnormal values ​​231 in the group of measurement data 211 from the detection signals of the green light sensor 11, the red light sensor 12, and the infrared light sensor 13, displays the group of measurement data 211 and the detection index 226 on the display unit 30 on the same time axis, displays a predetermined threshold L for the detection index 226 on the display unit 30, and displays the range in which the detection index 226 exceeds the threshold L and the range in which it falls below the threshold L in different display modes within the group of measurement data 211 displayed on the display unit 30.

[0035] In such a pulse oximeter 1, a red light sensor 12, an infrared light sensor 13, and a control device 20 provide a group of measurement data 211 of the blood oxygen saturation of the subject 9. The control device 20 displays a detection index 226 indicating an abnormal value 231 along with the measurement data group 211 on the display unit 30. In particular, the display unit 30 displays the range in which the detection index 226 exceeds a threshold L and the range in which it falls below a threshold L in different display modes, thereby allowing the user to eliminate measurement errors caused by the subject's body movement and improve measurement accuracy.

[0036] [Other embodiments] Figure 13 shows another embodiment of the present disclosure. In Figure 13, the pulse oximeter 3 has a flat, disc-shaped case 4 and a belt 5, and can be worn on the user's wrist. A display unit 40 is formed on the surface of case 4, and the display unit 40 displays the current time 41, oxygen saturation level 42, main alert 43, and alert details 44. A control device 20A is housed inside case 4, and a sensor unit 10A is formed on the back side of case 4.

[0037] The sensor unit 10A, like the sensor unit 10 of the previously described embodiment, includes a green light sensor 11, a red light sensor 12, and an infrared light sensor 13. The green light sensor 11, the red light sensor 12, and the infrared light sensor 13 are positioned to be in close contact with the surface of the wrist when the pulse oximeter 3 is attached to the user's wrist with the belt 5, and this surface of the wrist becomes the subject 9. The control device 20A is configured in the same way as the control device 20 described above. It measures the blood oxygen saturation of the subject 9 from the detection signals of the green light sensor 11, the red light sensor 12, and the infrared light sensor 13 to generate a group of measurement data 211. It also calculates a detection index 226 for the group of measurement data 211 and detects an abnormal value 231.

[0038] The control device 20A, upon user operation, displays oxygen saturation data (including abnormal values ​​231) from the measurement data group 211 at the current time or any past time on the oxygen saturation display 42, and also displays a main alert display 43 and an alert detail display 44 corresponding to the detection index 226 at the same time. For example, if the detection index 226 at the time of display of the measurement data group 211 indicates an abnormal value 231, a highly identifiable string such as "Posture abnormal value" is displayed as the main alert display 43, and specific instructions such as "Please raise your hands to the same height as your heart" are displayed as the alert detail display 44. If the detection index 226 is within the normal range, the main alert display 43 may display a string such as "Normal value," or a cautionary message such as "Slightly low value" may be displayed depending on the data value of the oxygen saturation display 42.

[0039] In such a pulse oximeter 3, the blood oxygen saturation of the subject 9 can be measured using the red light sensor 12, the infrared light sensor 13, and the control device 20A, and the measurement results can be displayed on the display unit 40. The control device 20A detects abnormal values ​​231 in the measurement data group 211 based on detection indicators 226 obtained from the green light sensor 11, the red light sensor 12, and the infrared light sensor 13, and can display warning messages, etc., on the main alert display 43 and the alert detail display 44 according to the detection indicators 226.

[0040] The pulse oximeter 3 of this embodiment includes, as a sensor unit 10A, a green light sensor 11 that detects green light transmitted or reflected from a subject 9 when green light is irradiated onto the subject 9, a red light sensor 12 that detects red light transmitted or reflected from a subject 9 when red light is irradiated onto the subject 9, an infrared light sensor 13 that detects infrared light transmitted or reflected from a subject 9 when infrared light is irradiated onto the subject 9, a control device 20A that processes the detection signals from the green light sensor 11, the red light sensor 12, and the infrared light sensor 13, and a display unit 40 that displays the information obtained by the control device 20A. The control device 20A has the following configuration: it generates a group of measurement data 211 indicating the oxygen saturation of the subject 9 from the detection signals of the red light sensor 12 and the infrared light sensor 13, calculates a detection index 226 for abnormal values ​​231 in the group of measurement data 211 from the detection signals of the green light sensor 11, the red light sensor 12, and the infrared light sensor 13, displays the group of measurement data 211 on the display unit 40, and issues an alert (main alert display 43 and alert detail display 44) regarding the posture of the subject 9 when the detection index 226 exceeds a predetermined threshold L.

[0041] In such a pulse oximeter 3, a red light sensor 12, an infrared light sensor 13, and a control device 20A provide a group of measurement data 211 of the blood oxygen saturation of the subject 9. The control device 20A displays a detection index 226 indicating an abnormal value 231 on the display unit 30 along with the measurement data group 211. In particular, when the detection index 226 exceeds a predetermined threshold L, the control device 20A issues an alert regarding the posture of the subject 9, thereby eliminating measurement errors caused by the subject's body movement and improving measurement accuracy.

[0042] [Differentiation] The present invention is not limited to the embodiments described above, and any modifications that can achieve the objectives of the present invention are included in the present invention. The present invention is not limited to the reflective pulse oximeter described in the embodiments, but can also be used with a transmissive pulse oximeter.

[0043] In this specification, the pulse oximeter is described as a device that measures blood oxygen saturation. However, it goes without saying that the present invention can also be used with a blood oxygen wellness device that displays the measurement result as "blood oxygen level," rather than a device called a pulse oximeter. In this specification, the term pulse oximeter should be understood to include a blood oxygen wellness device.

[0044] [Summary of this disclosure] A pulse oximeter according to a first aspect of this disclosure includes: a green light sensor that detects green light transmitted or reflected from a subject after irradiating the subject with green light; a red light sensor that detects red light transmitted or reflected from a subject after irradiating the subject with red light; an infrared light sensor that detects infrared light transmitted or reflected from a subject after irradiating the subject with infrared light; and a control device that processes the detection signals of the green light sensor, the red light sensor, and the infrared light sensor, wherein the control device includes a saturation measurement unit that generates a group of measurement data indicating the oxygen saturation of the subject from the detection signals of the red light sensor and the infrared light sensor. The system includes a detection index calculation unit that calculates the ratio of the detection signals of the green light sensor, the red light sensor, and the infrared light sensor as a detection index, and an abnormal value detection unit that detects an abnormal value of the oxygen saturation based on the detection index, wherein the detection index calculation unit calculates at least one of the following as the detection index: a green light pulse wave signal intensity ratio, which is the ratio of the amplitude of the vibration component in the detection signal output by the green light sensor to the signal intensity of the detection signal, and a red light pulse wave signal intensity ratio, which is the ratio of the amplitude of the vibration component in the detection signal output by the red light sensor to the signal intensity of the detection signal; and a green infrared signal ratio, which is the ratio of the green light pulse wave signal intensity ratio and an infrared light pulse wave signal intensity ratio, which is the ratio of the amplitude of the vibration component in the detection signal output by the infrared light sensor to the signal intensity of the detection signal.

[0045] In such a pulse oximeter, a set of measurement data on the subject's blood oxygen saturation is obtained by a red light sensor, an infrared light sensor, and a saturation measurement unit of the control device. Furthermore, a detection index calculation unit calculates a detection index. Based on the detection index, an abnormal value detection unit detects abnormal values ​​in the measurement data set, thereby eliminating measurement errors caused by the subject's body movement and improving measurement accuracy. The detection index is calculated based on the ratio of the detection signals from the green light sensor, red light sensor, and infrared light sensor. In processing the detection signals from each color light sensor, the ratio of the signal intensity of each color light pulse wave, i.e., the ratio of the amplitude of the vibration component in the detection signal output by each sensor to the signal intensity of the detection signal, is used. This relativizes the rate of change of the vibration component in each detection signal, making it a suitable numerical value for comparison. The detection indicators used are at least one of the following: the green-red signal ratio, which is the ratio of the green light pulse wave signal intensity ratio to the red light pulse wave signal intensity ratio; and the green-infrared signal ratio, which is the ratio of the green light pulse wave signal intensity ratio to the infrared light pulse wave signal intensity ratio. Green light, which is used in common for both the green-red signal ratio and the green-infrared signal ratio, is easily absorbed by hemoglobin in the blood, and the detection signal of the green light sensor indicates the amount of hemoglobin in the blood. During sleep, shallow breathing due to sleep apnea syndrome reduces oxygen saturation. Even with such a decrease in oxygen saturation due to sleep apnea syndrome, if there is no change in blood flow, the detection signal of the green light sensor will not change. On the other hand, if blood flow is suppressed due to a change in the subject's posture, the detection signal of the green light sensor decreases along with the decrease in hemoglobin flow. Therefore, by using at least one of the green-red signal ratio and the green-infrared signal ratio as the detection indicator, abnormal values ​​caused by the subject's body movement can be detected.

[0046] In a pulse oximeter according to a first aspect of this disclosure, it is preferable that the abnormal value detection unit determines an abnormal value when the detection index is in a state where the blood flow of the subject is compressed.

[0047] In a pulse oximeter according to a first aspect of the present disclosure, the green light sensor, the red light sensor, and the infrared light sensor detect the limbs of the subject, and it is preferable that the state in which the blood flow of the subject is compressed is such that the limbs that are the target of detection of the subject, who is in a supine position, hang down below the torso of the subject, or the limbs that are the target of detection of the subject, who is in a supine position, are buried under other parts of the subject.

[0048] In a pulse oximeter according to a first aspect of this disclosure, it is preferable that the detection target of the green light sensor, the red light sensor, and the infrared light sensor is the head of the subject, and that the state in which the blood flow of the subject is compressed is a state in which the blood vessels in the neck of the subject are compressed.

[0049] In a pulse oximeter according to a first aspect of this disclosure, it is preferable that the abnormal value detection unit determines that an abnormal value exists when the detection index exceeds a predetermined threshold.

[0050] In a pulse oximeter according to a first aspect of this disclosure, the control device further comprises a measurement data processing unit, and it is preferable that the measurement data processing unit deletes the data determined to be an abnormal value from the measurement data group.

[0051] In a pulse oximeter according to a first aspect of this disclosure, the control device further includes an alert issuing unit that issues an oxygen saturation decrease alert based on the measurement data group, and it is preferable that the alert issuing unit excludes the data determined to be abnormal from the alert target.

[0052] A pulse oximeter according to a second aspect of this disclosure includes: a green light sensor that detects green light transmitted or reflected from a subject after irradiating the subject with green light; a red light sensor that detects red light transmitted or reflected from a subject after irradiating the subject with red light; an infrared light sensor that detects infrared light transmitted or reflected from a subject after irradiating the subject with infrared light; a control device that processes the detection signals from the green light sensor, the red light sensor, and the infrared light sensor; and a display unit that displays information obtained by the control device, wherein the control device is A set of measurement data indicating the oxygen saturation of the subject is generated from the detection signals of the red light sensor and the infrared light sensor, an abnormality detection index in the set of measurement data is calculated from the detection signals of the green light sensor, the red light sensor, and the infrared light sensor, the set of measurement data and the detection index are displayed on the display unit on the same time axis, a predetermined threshold for the detection index is displayed on the display unit, and the range in which the detection index exceeds the threshold and the range in which it falls below the threshold are displayed in different display modes within the set of measurement data displayed on the display unit.

[0053] In such a pulse oximeter, a red light sensor, an infrared light sensor, and a control device obtain a set of measurement data on the subject's blood oxygen saturation. The control device displays a detection index indicating an abnormal value along with the measurement data set on the display unit. In particular, by displaying the range in which the detection index exceeds a threshold and the range in which it falls below a threshold in different display modes, the user can eliminate measurement errors caused by the subject's body movement and improve measurement accuracy.

[0054] In a pulse oximeter according to a second aspect of the present disclosure, the control device preferably displays the threshold value by a mark or graphic added to the display of the detection index.

[0055] In a pulse oximeter according to a second aspect of the present disclosure, the control device preferably has different display modes for the range above the threshold and the range below the threshold, which are one or a combination of saturation, brightness, and transparency.

[0056] In a pulse oximeter according to a second aspect of the present disclosure, it is preferable that the control device displays the measurement data group on the display unit and issues an alert regarding the posture of the subject when the detection index exceeds the threshold.

[0057] A pulse oximeter according to a third aspect of this disclosure includes: a green light sensor that detects green light transmitted or reflected by a subject after irradiating the subject with green light; a red light sensor that detects red light transmitted or reflected by a subject after irradiating the subject with red light; an infrared light sensor that detects infrared light transmitted or reflected by a subject after irradiating the subject with infrared light; a control device that processes the detection signals of the green light sensor, the red light sensor, and the infrared light sensor; and a display unit that displays information obtained by the control device. The control device generates a group of measurement data indicating the oxygen saturation of the subject from the detection signals of the red light sensor and the infrared light sensor, calculates an abnormality detection index in the group of measurement data from the detection signals of the green light sensor, the red light sensor, and the infrared light sensor, displays the group of measurement data on the display unit, and issues an alert regarding the posture of the subject when the detection index exceeds a predetermined threshold.

[0058] In such a pulse oximeter, a red light sensor, an infrared light sensor, and a control device obtain a set of measurement data on the subject's blood oxygen saturation. The control device displays a detection index indicating an abnormal value along with the measurement data on the display unit, and in particular, when the detection index exceeds a predetermined threshold, it issues an alert regarding the subject's posture, thereby allowing the user to eliminate measurement errors caused by the subject's body movement and improve measurement accuracy. [Explanation of Symbols]

[0059] 1,3…Pulse oximeter, 2,4…Case, 5…Belt, 9…Subject, 10,10A…Sensor unit, 11…Green light sensor, 110…Photodetector, 111…Green light source, 112…Red light source, 113…Infrared light source, 12…Red light sensor, 13…Infrared light sensor, 14…Accelerometer, 20,20A…Control device, 21…Saturation measurement unit, 211…Measurement data group, 22…Detection index calculation unit, 221…Green light pulse wave signal intensity ratio, 222…Red light pulse wave signal intensity ratio, 223…Infrared light pulse wave signal intensity ratio, 224…Green-red signal ratio, 225…Green-infrared signal ratio, 226…Detection index, 23… Anomaly detection unit, 231... Anomaly value, 24... Measurement data processing unit, 241... Interpolation data, 242... Correction data group, 25... Display control unit, 30... Display unit, 31... Display screen, 32... Time axis, 33... Oxygen saturation graph, 331... Anomaly value graph, 332... Interpolation data graph, 34... Detection index graph, 35... Threshold display, 36... Vertical axis display, 40... Display unit, 41... Current time display, 42... Oxygen saturation display, 43... Main alert display, 44... Alert details display, AC... Amplitude signal strength, DC... DC signal strength, L... Threshold, Rig... Ratio, Rrg... Ratio, S1~S6... Processing, T1, T2... Interval.

Claims

1. The system includes: a green light sensor that detects the green light transmitted or reflected by irradiating a subject with green light; a red light sensor that detects the red light transmitted or reflected by irradiating a subject with red light; an infrared light sensor that detects the infrared light transmitted or reflected by irradiating a subject with infrared light; and a control device that processes the detection signals from the green light sensor, the red light sensor, and the infrared light sensor. The control device is A saturation measurement unit that generates a set of measurement data indicating the oxygen saturation of the subject from the detection signals of the red light sensor and the infrared light sensor, A detection index calculation unit that calculates the ratio of the detection signals of the green light sensor, the red light sensor, and the infrared light sensor as a detection index, The system includes an abnormal value detection unit that detects an abnormal value of the oxygen saturation based on the aforementioned detection index, The aforementioned detection index calculation unit is: The green-red signal ratio is the ratio of the green light pulse wave signal intensity ratio, which represents the ratio of the amplitude of the vibration component in the detection signal output by the green light sensor to the signal intensity of the detection signal, and the red light pulse wave signal intensity ratio, which represents the ratio of the amplitude of the vibration component in the detection signal output by the red light sensor to the signal intensity of the detection signal. The green-infrared signal ratio is the ratio of the green light pulse wave signal intensity ratio to the infrared light pulse wave signal intensity ratio, which represents the ratio of the amplitude of the vibration component in the detection signal output by the infrared light sensor to the signal intensity of the detection signal. A pulse oximeter that calculates at least one of the following as the detection index.

2. The pulse oximeter according to claim 1, wherein the abnormal value detection unit determines that the detection index is an abnormal value when the blood flow of the subject is compressed.

3. The green light sensor, the red light sensor, and the infrared light sensor detect the limbs of the subject, The pulse oximeter according to claim 2, wherein the state in which the blood flow of the subject is compressed is such that the limbs targeted for detection of the subject, who are in a supine position, hang downward below the torso of the subject, or the limbs targeted for detection of the subject, who are in a supine position, are buried under other parts of the subject.

4. The green light sensor, the red light sensor, and the infrared light sensor detect the head of the subject, The pulse oximeter according to claim 2, wherein the state in which the blood flow of the subject is compressed is the state in which the blood vessels in the neck of the subject are compressed.

5. The pulse oximeter according to any one of claims 1 to 4, wherein the abnormal value detection unit determines that the detection index is an abnormal value when it exceeds a predetermined threshold.

6. The control device further includes a measurement data processing unit, The pulse oximeter according to claim 5, wherein the measurement data processing unit deletes the data determined to be an abnormal value from the measurement data group.

7. The pulse oximeter according to claim 5, wherein the control device issues an oxygen saturation decrease alert based on the measurement data group and excludes the data determined to be abnormal from the alert target.

8. The system includes: a green light sensor that detects the green light transmitted or reflected by irradiating a subject with green light; a red light sensor that detects the red light transmitted or reflected by irradiating a subject with red light; an infrared light sensor that detects the infrared light transmitted or reflected by irradiating a subject with infrared light; a control device that processes the detection signals from the green light sensor, the red light sensor, and the infrared light sensor; and a display unit that displays the information obtained by the control device. The control device is From the detection signals of the red light sensor and the infrared light sensor, a set of measurement data indicating the oxygen saturation of the subject is generated. From the detection signals of the green light sensor, the red light sensor, and the infrared light sensor, an index for detecting abnormal values ​​in the measurement data group is calculated. The measurement data set and the detection index are displayed on the display unit on the same time axis, A predetermined threshold for the detection index is displayed on the display unit. A pulse oximeter that displays, in a different display manner, the range in which the detection index exceeds the threshold and the range in which it falls below the threshold, among the group of measurement data displayed on the display unit.

9. The control device is The pulse oximeter according to claim 8, wherein the threshold is displayed by a mark or figure added to the display of the detection index.

10. The control device is The pulse oximeter according to claim 8, wherein the different display modes of the range of the detection index above the threshold and the range below the threshold are any or a combination of saturation, brightness, and transparency.

11. The control device is The pulse oximeter according to claim 8, wherein when the detection index exceeds the threshold, the display unit displays the measurement data group and issues an alert regarding the posture of the subject.

12. The system includes: a green light sensor that detects the green light transmitted or reflected by irradiating a subject with green light; a red light sensor that detects the red light transmitted or reflected by irradiating a subject with red light; an infrared light sensor that detects the infrared light transmitted or reflected by irradiating a subject with infrared light; a control device that processes the detection signals from the green light sensor, the red light sensor, and the infrared light sensor; and a display unit that displays the information obtained by the control device. The control device is From the detection signals of the red light sensor and the infrared light sensor, a set of measurement data indicating the oxygen saturation of the subject is generated. From the detection signals of the green light sensor, the red light sensor, and the infrared light sensor, an index for detecting abnormal values ​​in the measurement data group is calculated. A pulse oximeter that displays the measurement data group on the display unit and issues an alert regarding the posture of the subject when the detection index exceeds a predetermined threshold.

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