JP2019097771A - Pulse oximeter and probe for biological information measurement - Google Patents

Abstract

To provide a pulse oximeter which can improve measurement accuracy and can simplify an operation circuit.SOLUTION: A pulse oximeter has: an LED 103 that simultaneously emits red light and near infrared light; a first photodetector 104 for receiving transmitted light of light of a light emitting unit, which has been transmitted through a measurement site, and detecting red light contained in the transmitted light; a second photodetector 105 for receiving the transmitted light of the light of the light emitting unit, which has been transmitted through the measurement site, and detecting near infrared light contained in the transmitted light; and a signal processing unit 203 that obtains SpObased on detection results of the first and second photodetectors 104, 105.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pulse oximeter and a biological information measuring probe.

A pulse oximeter is a medical device that can non-invasively measure arterial blood oxygen saturation (hereinafter simply referred to as SpO ₂ or oxygen saturation) that represents the ratio of oxygenated hemoglobin to total hemoglobin in arterial blood (eg, patented) Reference 1 and 2).

  The pulse oximeter is configured to attach a probe to a measurement site such as a finger, a foot pad or an earlobe. The probe is provided with a light emitting element such as a light emitting diode and a photodetector such as a photodiode.

  Then, by alternately emitting a light emitting element emitting red light and a light emitting element emitting near infrared light, the red light and the near infrared light are alternately irradiated toward the measurement site, and the light is transmitted through the measurement site Or light reflected from the measurement site is detected by a photodetector. The pulse oximeter calculates the oxygen saturation using a detection signal of transmitted light or reflected light obtained by a photodetector. Specifically, the fluctuation of the light detection level synchronized with the pulse of arterial blood is compared between the case of red light and the case of near infrared light, and the oxygen saturation is calculated from the ratio. The pulse oximeter displays the calculated arterial blood oxygen saturation on the display unit.

JP, 2001-78990, A JP, 2015-107152, A

  By the way, in the conventional pulse oximeter, the light emitting unit is composed of an LED for emitting red light and an LED for emitting near infrared light, and the light receiving unit is a single PD for detecting these lights transmitted through the living body. (Photo-Diode) is configured. As described above, since the light receiving unit is configured of one PD, when red light and near infrared light simultaneously enter the PD, it becomes impossible to distinguish between red light and near infrared light, so red light and near infrared light can not be distinguished. The light is alternated (precisely red light → off → near infrared light → off → ...).

  As a result, in the conventional pulse oximeter, since red light and near infrared light LEDs are alternately emitted, measurement in each color can not be performed at the same time, and a delay of, for example, several milliseconds is generated. There is a drawback that the measurement accuracy is reduced. In addition, since it is necessary to light the LEDs of red light and near infrared light alternately at predetermined timing, there is a drawback that the operation circuit of the LED becomes complicated.

  The present invention has been made in consideration of the above points, and provides a pulse oximeter and a biological information measuring probe which can improve measurement accuracy and can simplify an operation circuit.

One aspect of the pulse oximeter of the present invention is
A light emitting unit that simultaneously emits red light and near infrared light;
A first photodetector for receiving transmitted light of the light of the light emitting portion transmitted through the measurement site and detecting red light contained in the transmitted light;
A second photodetector which receives transmitted light of the light of the light emitting part transmitted through the measurement site and detects near infrared light contained in the transmitted light;
A signal processing unit for obtaining arterial blood oxygen saturation based on detection results of the first and second photodetectors;
Equipped with

One embodiment of the biological information measuring probe of the present invention is
A light emitting unit that simultaneously emits red light and near infrared light;
A first photodetector for receiving transmitted light of the light of the light emitting portion transmitted through the measurement site and detecting red light contained in the transmitted light;
A second photodetector which receives transmitted light of the light of the light emitting part transmitted through the measurement site and detects near infrared light contained in the transmitted light;
An output unit that outputs detection results of the first and second photodetectors;
Equipped with

  According to the present invention, the light emitting unit simultaneously emits red light and near infrared light, and the transmitted light is detected by the two photodetectors that detect red light and near infrared light, respectively. Since the delay does not occur, the measurement accuracy is improved, and the red light and the near infrared light may be emitted simultaneously, so that the operation circuit can be simplified.

The figure which shows the whole structure of the pulse oximeter which concerns on embodiment. Cross section for explaining the configuration of a probe unit of the embodiment Sectional view showing the configuration of the first photodetector Sectional view showing the configuration of the second photodetector Sectional view showing another configuration example of the probe unit The figure which shows the light emission operation of LED by embodiment A plan view showing another configuration example of the probe unit Diagram showing the sensitivity characteristics of a common photodiode

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing an entire configuration of a pulse oximeter according to the present embodiment. The pulse oximeter 10 has a probe unit 100 and a main body unit 200. The probe unit 100 and the main unit 200 are connected via a cable 300. The probe unit 100 is attachable to the subject's finger, and the main body unit 200 is attachable to the subject's wrist using a wrist band (not shown).

  The main unit 200 uses the detection signal of the transmitted light input from the photodetectors 104 and 105 (FIG. 2) of the probe unit 100 to perform the measurement processing of the oxygen saturation degree (FIG. 2), the display unit 201 And an operation unit 202 and the like.

  FIG. 2 is a cross-sectional view for explaining the configuration of the probe unit 100 according to the present embodiment. FIG. 2 is a cross-sectional view of the probe unit 100 as viewed from the side direction of the finger in a state where the probe unit 100 is attached to the finger.

  The probe unit 100 has a case 101, and the case 101 is shaped so as to wrap the fingertip so as to prevent external light from entering the inside as much as possible.

  An LED 103 is provided in the case 101. The LED 103 is provided at a position facing the measurement site of oxygen saturation. In the example of FIG. 2, the LED 103 is provided at a position facing the nail.

The LED 103 has a chip that emits red light and a chip that emits near infrared light, and at the time of measuring SpO ₂ , these chips simultaneously emit red light and near infrared light. . Note that the LED 103 does not necessarily have to have a chip that emits red light and a chip that emits near infrared light, and in short, as long as it can simultaneously emit red light and near infrared light. For example, it may be configured by a white LED that emits white light including a red light component and a near infrared light component.

Generally, red light in SpO ₂ measurement is defined as 660 nm ± 5 nm, and near infrared light is defined as 800 to 950 nm. Thus, red light and near infrared light in the present specification mean light in this range.

  In the case 101, photodetectors 104 and 105 are provided. The photodetectors 104 and 105 are provided at positions in the case 101 opposite to the LED 103 with respect to the measurement site. The photodetectors 104 and 105 are disposed at positions abutted against the belly of the subject's finger when the probe unit 100 is attached to the finger.

  As shown in FIG. 3A, the photodetector 104 is composed of a photodiode 104a and a color filter 104b that transmits red light (for example, a wavelength of 660 [nm]) contained in transmitted light. Further, as shown in FIG. 3B, the photodetector 105 is composed of a photodiode 105a and a color filter 105b for transmitting near infrared light (for example, wavelength 940 [nm]) contained in the transmitted light. Thus, the photodetector 104 detects red light contained in the transmitted light of the measurement site, and the photodetector 105 detects near infrared light contained in the transmitted light of the measurement site.

The photodetectors 104 and 105 may be arranged side by side in the longitudinal direction of the finger as shown in FIG. 2, and the cross-sectional view of the probe unit 100 seen from the fingertip direction in a state where the probe unit 100 is attached to the finger. It may be arranged side by side in the width direction of the finger as shown in FIG. However, it is preferable that the photodetectors 104 and 105 be disposed adjacent to each other. In other words, in consideration of the measurement accuracy of SpO ₂ , it is preferable that the photodetectors 104 and 105 be provided at positions that can receive transmitted light of substantially the same path.

  The signal processing unit 203 is provided in the main unit 200 (FIG. 1), receives the detection result of the red light and the detection result of the near infrared light from the photodetectors 104 and 105, and the red light and the near infrared light Calculate the oxygen saturation based on the ratio of In FIG. 2, it is shown that one line is emitted from each of the photodetectors 104 and 105, but actually, a plurality of conducting wires including plus and minus lines are emitted from each of the photodetectors 104 and 105. There is.

FIG. 5 is a diagram showing the light emitting operation of the LED 103 according to the present embodiment. The LED 103 repeats the operation of simultaneously emitting red light and near-infrared light in a period of 1 ms and turning off the next period of 1 ms. Of course, for example, the red light and the near infrared light may be simultaneously emitted in a period of 3 msec, and the operation of extinguishing the next 3 msec may be repeated. Alternatively, the red light and the near infrared light may be continuously emitted at the same time until the measurement of SpO ₂ is completed.

As described above, according to the present embodiment, the transmitted light of the light of the light emitting unit that transmits the red light and the near infrared light at the same time and the light emitting unit that has transmitted the measurement site is received, A first photo-detector 104 for detecting red light contained in the light, and a second photo for receiving transmitted light of light from the light emitting portion transmitted through the measurement site and detecting near-infrared light contained in the transmitted light Since the detector 105 and the signal processing unit 203 for obtaining SpO ₂ based on the detection results of the first and second photodetectors 104 and 105 are provided, there is no delay in the detection of each color, so the measurement accuracy is improved. At the same time, the operation circuit can be simplified since red light and near infrared light may be emitted simultaneously.

  The above-described embodiment is merely an example of embodying the present invention, and the technical scope of the present invention should not be interpreted in a limited manner by these. That is, the present invention can be implemented in various forms without departing from the scope of the present invention or the main features thereof.

  Although the above-mentioned embodiment described the case where probe part 100 was constituted by case 101, the present invention is applicable not only to this but to the probe constituted by the tape wound around a finger. In this case, as shown in FIG. 6, the LED 103 and the photodetectors 104 and 105 may be provided at predetermined positions inside the tape 300 (that is, on the side facing the finger when the tape 300 is wound).

  In the above embodiment, the pulse oximeter 10 of the type in which the probe unit 100 is attached to a finger is described as an example, but in the present invention, the probe unit is attached to a measurement site such as a foot or earlobe It is equally applicable to pulse oximeters.

  In the above-described embodiment, although the separate type pulse oximeter in which the probe unit 100 and the main body unit 200 are separated has been described as an example, the present invention is not limited to this, and an integrated pulse oximeter It can also be applied.

  In the above embodiment, the case where the detection signal obtained by the probe unit 100 is output to the signal processing unit 203 of the pulse oximeter 10 has been described, but the detection signal obtained by the probe unit 100 is another biological information You may output to a processing apparatus. That is, the probe unit 100 of the above-described embodiment is applicable to devices other than the pulse oximeter. For example, the detection signal obtained by the probe unit 100 may be output to a biological information processing apparatus that measures a photoelectric pulse wave. In practice, the probe unit 100 has an output unit such as a cable or a connector for outputting the detection result of the photodetectors 104 and 105, and therefore, the probe unit 100 is connected to an external biological information processing apparatus via the output unit. In this way, the probe unit 100 can be widely used as a biological information measurement probe.

Furthermore, in addition to the above embodiment, the passband of the color filter 104b of the photodetector 104 for detecting red light is made wider than the passband of the color filter 105b of the photodetector 105 for detecting near infrared light. Is preferred. Hereinafter, this point will be described. FIG. 7 shows the sensitivity characteristics of a general photodiode. As can be seen from the figure, the sensitivity of the photodiode to red light (around 660 nm) is lower than the sensitivity to near infrared light (around 900 nm). Taking this into consideration, the passband of the color filter 104b of the photodetector 104 for detecting red light is made wider than the passband of the color filter 105b of the photodetector 105 for detecting near infrared light. By compensating for the poor sensitivity, the detection accuracy of the photodiode 104b can be made approximately the same as the detection accuracy of the photodiode 105b, and the measurement accuracy of the final SpO ₂ can be improved. In addition, since the transmittance of red light transmitted through the measurement site is smaller than the transmittance of near-infrared light transmitted through the measurement site, the photodetector 104 for detecting red light also ensures the desired amount of light. It is effective to make the pass band of the color filter 104 b wider than the pass band of the color filter 105 b of the photodetector 105 that detects near-infrared light.

  In the above embodiment, for example, as shown in FIG. 5, when emitting red light, near infrared light is always emitted at the same time. However, infrared light and near infrared light are not always required. And may not always emit light simultaneously. For example, red light and near infrared light may be emitted simultaneously for the first one second, and only red light may be emitted for the subsequent one second. That is, it may have a period in which measurement is performed by simultaneously emitting red light and near infrared light, and a period in which measurement is performed by emitting only either red light or near infrared light. The point is to have a period for simultaneously emitting red light and near infrared light.

  The present invention can achieve the effects of improving measurement accuracy and simplifying the operation circuit, and is suitable for, for example, a portable pulse oximeter.

10 pulse oximeter 100 probe unit 101 case 103 LED
DESCRIPTION OF SYMBOLS 104, 105 Photodetector 104a, 105a Photodiode 104b, 105b Color filter 200 Main-body part 203 Signal processing part

Claims (3)

A light emitting unit that simultaneously emits red light and near infrared light;
A first photodetector for receiving transmitted light of the light of the light emitting portion transmitted through the measurement site and detecting red light contained in the transmitted light;
A second photodetector which receives transmitted light of the light of the light emitting part transmitted through the measurement site and detects near infrared light contained in the transmitted light;
A signal processing unit for obtaining arterial blood oxygen saturation based on detection results of the first and second photodetectors;
Pulse oximeter equipped with. The first photodetector has a color filter for transmitting red light contained in the transmitted light, and the second photodetector has a color filter for transmitting near-infrared light contained in the transmitted light.
The passband of the color filter of the first photodetector is wider than the passband of the color filter of the second photodetector,
The pulse oximeter according to claim 1. A light emitting unit that simultaneously emits red light and near infrared light;
A first photodetector for receiving transmitted light of the light of the light emitting portion transmitted through the measurement site and detecting red light contained in the transmitted light;
A second photodetector which receives transmitted light of the light of the light emitting part transmitted through the measurement site and detects near infrared light contained in the transmitted light;
An output unit that outputs detection results of the first and second photodetectors;
A probe for measuring biological information comprising the

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