JP2019048050A - Pulse oximeter - Google Patents

Abstract

To suppress an influence of a sensor wearing pressure on a measurement result.SOLUTION: A pulse oximeter 1 comprises: a first light emitting unit 11 which generates first light; a second light emitting unit 12 which generates second light having a different wavelength from that of the first light; a light receiving unit 13 which respectively receives first return light of the first light from a living body and second return light of the second light from the living body; contact pressure detection means 14 which detects a signal relating to a contact pressure between the pulse oximeter and the living body; and output means which outputs information relating to oxygen saturation on the basis of a signal output from the light receiving unit due to each of the first return light and the second return light and a signal relating to the detected contact pressure.SELECTED DRAWING: Figure 1

Description

  The present invention relates to the technical field of pulse oximeters.

  This type of pulse oximeter is, for example, a ring-type pulse oximeter on the premise of always wearing, and for example, when there are few detectable pulsating components or blood vessels contract due to hypothermia, the measurement accuracy of oxygen saturation is There has been proposed a pulse oximeter which presses a measurement target site so as to increase the pulsation of the artery when it decreases, etc. (see Patent Document 1).

  Alternatively, a blood pressure value is determined based on the pulsation component and cuff pressure of one of the two volume signals corresponding to the light having different wavelengths, and the volume extracted from the pulsation component of each of the two volume signals There has been proposed a device which measures blood pressure and blood oxygen saturation simultaneously and continuously by obtaining blood oxygen saturation from pulse wave signals (see Patent Document 2).

JP 2007-330708 A JP-A-6-63024

By the way, in measurement of arterial oxygen saturation (hereinafter, appropriately referred to as “SpO ₂ ”) by a pulse oximeter, when the mounting pressure of a sensor constituting the pulse oximeter changes, the measurement result of SpO ₂ changes.

According to the technique described in the above-mentioned Patent Document 1, there is a possibility that the SpO ₂ value can not be measured correctly if the mounting pressure of the sensor of the ring-type pulse oximeter becomes relatively high due to, for example, the finger of the person to be measured becoming swollen. There is a technical problem that there is. Further, the technology described in Patent Document 2 has a technical problem that the sensor mounting pressure is not considered for SpO ₂ measurement.

  The present invention has been made in view of, for example, the above-mentioned problems, and an object thereof is to provide a pulse oximeter capable of suppressing the influence of the mounting pressure of a sensor.

  A first pulse oximeter according to the present invention, in order to solve the above-mentioned problems, a first light emitting unit for generating a first light, and a second light emission for generating a second light having a wavelength different from that of the first light. , A light receiving unit for receiving each of the first return light from the living body of the first light and the second return light from the living body of the second light, and a contact for detecting a signal related to the contact pressure with the living body The oxygen saturation is determined based on a pressure detection unit, a signal output from the light receiving unit due to each of the first return light and the second return light, and a signal related to the detected contact pressure. And output means for outputting information.

  A second pulse oximeter according to the present invention, in order to solve the above-mentioned problems, a first light emitting unit for generating a first light, and a second light emission for generating a second light having a wavelength different from that of the first light. A pulse oximeter comprising: a light receiving unit configured to receive the first return light from the living body of the first light and the second return light from the living body of the second light; Contact pressure detection means for detecting a signal related to the contact pressure with the living body, and output means for outputting information related to adjustment of the contact pressure according to the signal related to the detected contact pressure.

  The operation and other advantages of the present invention will be apparent from the embodiments to be described below.

It is a schematic block diagram which shows the outline | summary of the pulse oximeter which concerns on 1st Example. It is a block diagram which shows the principal part of the calculation apparatus which concerns on 1st Example. It is a figure which shows an example of the signal output from a light-receiving means for every mounting pressure. It is a characteristic view showing an example of the relation between mounting pressure and signal amplitude. Is a characteristic diagram showing an example of the relationship between the mounting pressure and SpO _2. It is a figure which shows an example of correction function F ((DELTA) p) of the amplification factor which concerns on 1st Example. The measurement result of the SpO ₂ if not corrected, a diagram showing an example of each of the measurement results of the SpO ₂ when it is corrected. It is a figure which shows the example of arrangement | positioning of each element which comprises the transmission type pulse oximeter which concerns on 1st Example. It is a figure which shows the example of arrangement | positioning of each element which comprises the reflection type pulse oximeter which concerns on 1st Example. It is a schematic block diagram which shows the outline | summary of the pulse oximeter which concerns on the modification of 1st Example. It is a schematic block diagram which shows the outline | summary of the pulse oximeter which concerns on 2nd Example. It is a schematic block diagram which shows the outline | summary of the pulse oximeter which concerns on the modification of 2nd Example.

  Hereinafter, an embodiment according to the pulse oximeter of the present invention will be described.

First Embodiment
The pulse oximeter according to the first embodiment is configured to include a first light emitting unit, a second light emitting unit, and a light receiving unit. The first light emitting unit generates a first light. The second light emitting unit generates second light having a wavelength different from that of the first light. Here, the wavelength of one of the first light and the second light is a wavelength at which absorption to oxygenated hemoglobin is dominant, and the wavelength of the other of the first light and the second light is a deoxygenated hemoglobin. It is desirable, but not limited to, that the wavelength at which the absorption of light is dominant. The pulse oximeter according to this embodiment may include three or more light emitting units.

  The light receiving unit receives each of the first return light of the first light from the living body and the second return light of the second light from the living body. Here, “return light” is a concept including not only light scattered or reflected by a living body, but also light transmitted through the living body. That is, the pulse oximeter according to the present embodiment may be a reflection type pulse oximeter or a transmission type pulse oximeter. The light receiving unit is not limited to being configured by, for example, a single light receiving element, and may be configured by a plurality of light receiving elements.

  The contact pressure detection means detects a signal related to the contact pressure between the pulse oximeter and the living body. Here, the “signal relating to the contact pressure” is not limited to a signal indicating the value of the contact pressure itself, but also, for example, an output signal of a sensor such as a pressure sensor, a signal indicating a physical quantity or parameter indirectly indicating the contact pressure, etc. It is an included concept.

  For example, an output unit including a memory, a processor, and the like may generate oxygen saturation based on a signal output from the light receiving unit due to each of the first return light and the second return light and a signal related to the detected contact pressure. Output information related to the degree. Here, the "information related to the oxygen saturation" is not limited to the information indicating the value of the oxygen saturation itself, for example, the information indicating the ratio between the return light of red light and the return light of infrared light, etc. Is a concept that also includes information that indirectly indicates.

  According to the study of the inventor of the present application, the following matters have become clear. That is, the pulse oximeter outputs the information related to the oxygen saturation based on the pulsation component of the output signal of the light receiving unit caused by the arterial blood. Here, the blood vessel pulsating in the living body is only the artery, and no pulsation occurs in the vein which leaks out from the capillary and the blood pressure is reduced to a level that can be regarded as 0 mmHg. However, in reality, arterial pulsations propagate through living tissue, causing the veins to physically vibrate. As a result, the pulsating component of the output signal of the light receiving unit includes information on veins more or less.

  When the contact pressure of the pulse oximeter on the living body changes, the physical distance between the artery and the vein in the living body changes, and the effect of arterial pulsation on the vein also changes. That is, as the contact pressure changes, the influence of the vein on the pulsation component of the output signal also changes. Pulse oximeters are often designed such that accurate oxygen saturation can be determined, assuming contact pressure. For this reason, depending on the contact pressure, the influence of the vein on the pulsating component of the output signal may be large, and erroneous oxygen saturation may be required.

  Therefore, in the present embodiment, the oxygen saturation is determined based on the signal output from the light receiving unit due to the first return light and the second return light by the output unit, and the signal related to the detected contact pressure. Information related to is output.

  Specifically, for example, the output unit corrects the signal output from the light receiving unit due to each of the first return light and the second return light according to the signal related to the detected contact pressure (for example, the signal amplitude Output information related to the degree of oxygen saturation. Alternatively, the output means may use information related to the oxygen saturation obtained based on the signal output from the light receiving unit due to each of the first return light and the second return light as a signal related to the detected contact pressure. Correct accordingly. In any case, information on oxygen saturation with or without the influence of contact pressure is output.

  As a result of the above, according to the pulse oximeter of the present embodiment, the influence of the contact pressure can be suppressed, and thus, highly reliable information on oxygen saturation can be output.

  In one aspect of the pulse oximeter according to the first embodiment, the output unit is a signal output from the light receiving unit due to the first return light and a signal output from the light receiving unit due to the second return light. The amplification factor according to at least one of the above is changed based on the signal concerning the detected contact pressure.

  For example, if the contact pressure becomes high, the physical distance between the artery and the vein in the living body becomes short, and the pulsation of the artery has a great influence on the vein. Then, the pulsation component (signal amplitude) of the output signal becomes large due to the influence of the vein.

  The output means is, as described above, output from the light receiving portion due to the signal returned from the light receiving portion due to the first return light and the second return light based on the signal related to the detected contact pressure. By changing the amplification factor of at least one of the signal and the signal, it is possible to suppress or eliminate the influence of the vein (that is, the influence of the contact pressure).

  Alternatively, in another aspect of the pulse oximeter according to the first embodiment, the pulse oximeter further includes a second output unit that outputs information related to adjustment of the contact pressure according to a signal related to the detected contact pressure.

  According to this aspect, if the contact pressure of the pulse oximeter is adjusted automatically or manually according to the information related to the adjustment of the output contact pressure, the oxygen saturation degree in which the influence of the contact pressure is suppressed is obtained. Such information can be output.

  Note that "information related to adjustment of contact pressure" is not limited to information indicating the adjustment value of the contact pressure itself, but, for example, indirectly adjusts the contact pressure such as "high contact pressure", "low contact pressure", etc. It is a concept that also includes prompting information, a physical quantity or parameter that directly or indirectly indicates the degree of contact pressure, and the like.

Second Embodiment
The pulse oximeter according to the second embodiment is configured to include a first light emitting unit, a second light emitting unit, and a light receiving unit. The first light emitting unit generates a first light. The second light emitting unit generates second light having a wavelength different from that of the first light. The light receiving unit receives each of the first return light of the first light from the living body and the second return light of the second light from the living body.

  The contact pressure detection means detects a signal related to the contact pressure between the pulse oximeter and the living body. For example, an output unit including a memory, a processor, and the like outputs information related to the adjustment of the contact pressure in accordance with the signal related to the detected contact pressure.

  If the contact pressure of the pulse oximeter is adjusted automatically or manually according to the output information on the adjustment of the contact pressure, the measurement of the oxygen saturation is carried out with the appropriate contact pressure. As a result, the oxygen saturation in which the influence of the contact pressure is suppressed can be determined.

  One aspect of the pulse oximeter according to the second embodiment further includes adjusting means for adjusting the contact pressure between the pulse oximeter and the living body in accordance with the output information relating to the adjustment of the contact pressure.

  According to this aspect, the contact pressure is automatically adjusted, which is very advantageous in practice.

  Embodiments of the pulse oximeter of the present invention will be described with reference to the drawings.

First Embodiment
A first embodiment of the pulse oximeter of the present invention will be described with reference to FIG. 1 to FIG.

  In FIG. 1, a pulse oximeter 1 outputs light from light emitting means 11, light emitting means 12, light receiving means 13 such as PD (Photodiode), mounting pressure detection means 14 such as a pressure sensor, and light receiving means 13. And calculating means 100 for processing the received signal and the signal output from the mounting pressure detecting means 14.

  The light emitting means 11 is configured to include, for example, an infrared light emitting diode (LED), and generates first light of a wavelength at which absorption into oxygenated hemoglobin is dominant. On the other hand, the light emitting means 12 is configured to include, for example, a red LED, and generates a second light of a wavelength that is dominant in absorption into deoxygenated hemoglobin.

  The first light and the second light are applied to blood vessels of a human finger (corresponding to the “living body” according to the present invention). The light receiving means 13 is a first transmitted light of the first light transmitted through the blood vessel (corresponding to "first returned light" according to the present invention) and a second transmitted light of the second light ("second returned light according to the present invention And the signal corresponding to the amount of light received is output.

Here, SpO ₂ is a signal transmitted from the light receiving means 13 due to the first transmitted light (that is, light of a wavelength at which absorption into oxygenated hemoglobin is dominant) and the second transmitted light (that is, deoxygenation) It is determined on the basis of the amplitude ratio of the signal output from the light receiving means 13 due to the light of the wavelength at which the absorption into the converted hemoglobin is dominant.

  By the way, it has been found from the research of the inventor of the present invention that the amplitude of the signal output from the light receiving means 13 is affected by the mounting pressure of the pulse oximeter 1. Specifically, for example, as shown in FIG. 3 and FIG. 4, the amplitude of the signal output from the light receiving means 13 is changed by the mounting pressure of the pulse oximeter.

  The “infrared light signal” and the “red light signal” in FIGS. 3 and 4 are “signals output from the light receiving means 13 due to the first transmitted light” and “second transmitted light”, respectively. This corresponds to the “signal output from the light receiving means 13 as a result”.

  In particular, when the mounting pressure of the pulse oximeter 1 becomes high, the proportion of absorption of the second light of a wavelength that is dominant in absorption into deoxygenated hemoglobin is increased due to venous blood. Then, the amplitude of the signal output from the light receiving means due to the second light (the second transmitted light) is lower than the amplitude of the signal output from the light receiving means 13 due to the first transmitted light. It becomes difficult (see FIG. 4).

As a result, the ratio of the amplitude of the signal output from the light receiving unit 13 due to the first transmitted light to the amplitude of the signal output from the light receiving unit 13 due to the second transmitted light is relatively small. Become. For this reason, if no measures are taken, as shown in FIG. 5, the SpO ₂ value decreases significantly as the mounting pressure of the pulse oximeter 1 increases (that is, an incorrect SpO ₂ value is output) Possible).

Therefore, in the present embodiment, in order to suppress the influence of veins, the calculation device 100 receives light according to the signal (corresponding to the “signal related to the mounting pressure” according to the present invention) output from the mounting pressure detection unit 14 The amplification factor of the signal resulting from the second transmitted light output from the means 13 is changed. Then, SpO ₂ is determined by the calculation apparatus 100 based on the amplitude ratio between the signal resulting from the second transmitted light whose amplification factor has been changed and the signal resulting from the first transmitted light output from the light receiving unit 13. Be

  Specifically, in FIG. 2, the calculation device 100 is configured to include the mounting pressure correction means 110, the amplifier 120 and the oxygen saturation output means 130.

  The mounting pressure correction means 110 determines the correction factor of the amplification factor related to the amplifier 120 according to the signal related to the mounting pressure output from the mounting pressure detection means 14.

  The correction coefficient is, for example, a function F of the difference Δp and a difference Δp between an actual mounting pressure based on a signal relating to the mounting pressure output from the mounting pressure detection means 14 and a predetermined reference mounting pressure. It is determined using (Δp).

  Such a function F (Δp) is attributable to the amplitude ratio between the signal originating in the first transmitted light and the signal originating in the second transmitted light at the reference mounting pressure, and the first transmitted light at any mounting pressure. A plurality of ratios of the amplitude ratio of the signal to the signal caused by the second transmitted light may be obtained, and may be obtained as an approximate curve for the obtained plurality of ratios (see FIG. 6).

  That is, the function F (Δp) can be expressed as the following equation.

Here, RD _std is the amplitude value of the signal originating in the second transmitted light at the reference mounting pressure, and IR _std is the amplitude value of the signal originating in the first transmitted light at the reference mounting pressure , RD is the amplitude value of the signal resulting from the second transmitted light at any mounting pressure, and IR is the amplitude value of the signal resulting from the first transmitted light at any mounting pressure.

  If the above equation is modified, the amplitude ratio between the signal resulting from the first transmitted light (that is, at an arbitrary mounting pressure) actually output and the signal resulting from the second transmitted light, and the function F (Δp) The amplitude ratio of the signal resulting from the first transmitted light and the signal resulting from the second transmitted light at the reference mounting pressure (in other words, the appropriate mounting pressure) can be determined using .

  According to the above equation, the mounting pressure correction means 110 corrects the value of F (Δp) obtained based on the signal relating to the mounting pressure output from the mounting pressure detection means 14 as the correction factor of the amplification factor according to the amplifier 120. Decide as.

The amplification factor related to the amplifier 120 is changed according to the correction coefficient determined by the mounting pressure correction means 110, whereby the amplitude (corresponding to "RD" in the above equation) of the signal caused by the second transmitted light is changed. Be done. The oxygen saturation degree output means 130 obtains SpO ₂ based on the signal resulting from the second transmitted light whose amplitude has been changed and the signal resulting from the first transmitted light.

If no measure is taken for the mounting pressure of the pulse oximeter 1, the measurement result of SpO ₂ will be as shown in FIG. 7 (a), for example. However, in the present embodiment, as described above, the amplification factor of the signal caused by the second transmitted light is corrected according to the mounting pressure of the pulse oximeter 1, so for example, the measurement results as shown in FIG. Is obtained. That is, according to the pulse oximeter 1 which concerns on a present Example, the measurement result which there is no influence of mounting pressure or hardly exists is obtained.

  The light emitting means 11 and the light emitting means 12 are driven alternately in time (that is, the first light and the second light are alternately generated in time). Then, for example, the signal output from the light receiving unit 13 is directly input to the oxygen saturation degree output unit 130 during the driving period of the light emitting unit 11 in the calculation device 100, and the light receiving unit 13 during the driving period of the light emitting unit 12. A switching circuit (not shown) is provided to input the signal output from the signal to the oxygen saturation output means 130 via the amplifier 120.

  Each of the light emitting means 11, the light emitting means 12, the light receiving means 13 and the mounting pressure detecting means 14 constituting the pulse oximeter 1 is, for example, as shown in FIG. The light receiving means 13 and the mounting pressure detection means 14 may be arranged on the inside of the finger. Alternatively, as shown in FIG. 8B, the light emitting means 11 and 12 and the mounting pressure detection means 14 may be disposed on the back of the finger, and the light receiving means 13 may be disposed on the inside of the finger. Alternatively, as shown in FIG. 8C, the light emitting units 11 and 12 and the mounting pressure detection unit 14a are disposed on the back of the finger, and the light receiving unit 13 and the mounting pressure detection unit 14b are disposed on the back of the finger. May be

  Although the transmission type pulse oximeter 1 has been described in this embodiment, the present invention is also applicable to a reflection type pulse oximeter. In this case, each of the light emitting means 11 and 12, the light receiving means 13, and the mounting pressure detecting means 14 can adopt any of the arrangements shown in FIGS. 9 (a) to 9 (c), for example.

  The “light emitting means 11”, “light emitting means 12”, “light receiving means 13”, “mounting pressure detecting means 14” and “calculating device 100” according to this embodiment are the “first light emitting unit” according to the present invention. These are examples of the “second light emitting unit”, the “light receiving unit”, the “contact pressure detecting unit”, and the “output unit”.

  In the present embodiment, as shown in FIG. 2, the amplification factor of the signal originating in the second transmitted light is changed, but the signal originating in the first transmitted light, not the signal originating in the second transmitted light The amplification factor of the signal may be changed, or the amplification factor of both the signal resulting from the first transmitted light and the signal resulting from the second transmitted light may be changed.

<Modification>
Next, a modification of the pulse oximeter according to the first embodiment will be described with reference to FIG. FIG. 10 is a schematic configuration view showing an outline of a pulse oximeter according to a modification of the first embodiment.

  In FIG. 10, a pulse oximeter 2 according to a modification of the first embodiment includes an arithmetic unit 21 and a mounting pressure in addition to the light emitting unit 11, the light emitting unit 12, the light receiving unit 13, the mounting pressure detecting unit 14 and the calculating apparatus 100. The display device 22 is provided.

  The arithmetic device 21 as one example of the “second output means” according to the present invention adjusts the mounting pressure suitable for display on the mounting pressure display device 22 based on the signal output from the mounting pressure detection means 14. Output relevant information. Here, in particular, the mounting pressure display device 22 displays such that the mounting pressure is guided within a predetermined range.

If the user of the pulse oximeter 2 adjusts the mounting pressure of the pulse oximeter 2 with reference to the display of the mounting pressure display 22, the value of SpO ₂ can be suitably measured.

  In particular, when the mounting pressure is relatively high, for example, as shown in FIG. 7, the correction amount becomes relatively large. Therefore, if configured as described above, errors due to correction can be suppressed, which is extremely advantageous in practical use.

Second Embodiment
A second embodiment of the pulse oximeter of the present invention will be described with reference to FIG. The second embodiment is the same as the first embodiment described above except that the configuration of the pulse oximeter is partially different. Therefore, in the second embodiment, the description overlapping with the first embodiment is omitted, and the same reference numerals are given to the common portions in the drawings, and only the fundamentally different points will be described with reference to FIG. explain.

  In FIG. 11, a pulse oximeter 3 according to the second embodiment comprises a light emitting means 11, a light emitting means 12, a light receiving means 13, a mounting pressure detecting means 14, a computing device 21, a mounting pressure display device 22 and a calculating device 100. It is configured.

  The arithmetic unit 21 outputs information relating to the adjustment of the mounting pressure suitable for display on the mounting pressure display device 22 based on the signal output from the mounting pressure detection means 14.

If the user of the pulse oximeter 2 adjusts the mounting pressure of the pulse oximeter 2 to a predetermined value with reference to the display of the mounting pressure display device 22, light reception as described in the first embodiment The value of SpO ₂ can be suitably measured without correcting the signal output from the means 13.

<Modification>
Next, a modification of the pulse oximeter according to the second embodiment will be described with reference to FIG. FIG. 12 is a schematic configuration view showing an outline of a pulse oximeter according to a modification of the second embodiment.

  12, the pulse oximeter 4 according to the modification of the second embodiment includes mounting pressure in addition to the light emitting unit 11, the light emitting unit 12, the light receiving unit 13, the mounting pressure detecting unit 14, the arithmetic unit 21 and the calculating unit 100. The adjustment unit 23 is configured.

  The mounting pressure adjustment unit 23 is provided between the support member that supports the light emitting units 11 and 12 and the support member that supports the light receiving unit 13 and the mounting pressure detection unit 14.

The arithmetic device 21 controls the mounting pressure adjustment unit 23 according to the signal output from the mounting pressure detection unit 14 so that the mounting pressure becomes a predetermined value. With this configuration, the SpO ₂ value can be suitably measured.

  The “calculation device 21” and the “mounting pressure adjustment unit 23” according to the present modification are examples of the “adjustment unit” according to the present invention.

  The present invention is not limited to the embodiments described above, and can be suitably modified without departing from the scope or spirit of the invention as can be read from the claims and the specification as a whole, and a pulse oximeter accompanied with such modifications. Also within the technical scope of the present invention.

  1, 2, 3, 4 pulse oximeter, 11, 12, light emitting means 13, light receiving means 14, 14a, 14b mounting pressure detecting means 21, arithmetic unit 22, mounting pressure display device 23, mounting Pressure adjustment unit, 100 ... calculation device

Claims (1)

A first light emitting unit that generates a first light;
A second light emitting unit that generates a second light having a wavelength different from that of the first light;
A light receiving unit for receiving the first return light from the living body of the first light and the second return light from the living body of the second light;
Contact pressure detection means for detecting a signal relating to the contact pressure with the living body;
An output that outputs information related to oxygen saturation based on a signal output from the light receiving unit due to each of the first return light and the second return light, and a signal related to the detected contact pressure Means,
A pulse oximeter characterized by comprising: