JPH0524006U - Reflective oximeter probe - Google Patents

Abstract

(57) [Summary] [Purpose] Oxygen saturation can be measured accurately regardless of individual differences of measurement subjects and differences in measurement sites, and oxygen saturation can be measured accurately and stably regardless of a decrease in peripheral circulation. Provided is a probe for a reflection-type oximeter that can be measured. [Structure] The light emitting elements 18 and 20 are alternately arranged around the light receiving element 16 so that the distance between the light emitting element 18 and the light receiving element 16 gradually differs.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a probe used in a reflection oximeter.

[0002]

[Prior Art]

 A photoelectric pulse wave that represents the intensity of the reflected light from multiple types of light-emitting elements that sequentially irradiate multiple types of light with different wavelengths on the surface of the living body and detects the reflected light from the living body with a common light-receiving element. Reflection oximeters are known that measure oxygen saturation in blood based on signals. For example, the one described in Japanese Patent Application Laid-Open No. 2-111344, which was previously filed by the applicant of the present application, is that, and the measurement of the oxygen saturation by such a reflection type oximeter constitutes a part of the skin. It is usually done in the vascular bed within the dermis.

In the reflection type oximeter described in the above publication, two kinds of light emitting elements having different emission wavelengths are alternately arranged on the circumference of a predetermined radius centered on the light receiving element over a whole circumference at predetermined intervals. In addition, a cylindrical light-shielding member for shielding the light reflected from the light emitting element to the light receiving element toward the light receiving element is provided with a probe provided between the light receiving element and the light emitting element. In addition to obtaining a large photoelectric pulse wave signal that represents the intensity of the reflected light that is detected, the oxygen saturation can be accurately measured even when the composition of the vascular bed is non-uniform or the probe is tilted. It has advantages such as stable measurement. Further, in the reflection type oximeter described in the above publication, the oxygen saturation is determined based on the ratio between the AC component and the DC component of the photoelectric pulse wave signal.

[0004]

[Problems to be solved by the device]

 However, the probe of the reflection type oximeter described in the above publication still has a problem to be solved. That is, since the distance between the light receiving element and each light emitting element is constant, the width of the optimum detection depth, which represents the depth from the surface of the living body where the intensity of the reflected light from the living body is sufficiently large, becomes narrow. Therefore, if the depth position of the blood vessel bed from the surface of the living body varies due to individual differences of the subject and differences in the measurement site, the size of the photoelectric pulse wave signal decreases and it becomes impossible to measure the oxygen saturation accurately. In addition, if the peripheral circulation is reduced due to a shock applied to the living body and reflected light is detected only from a deeper position in the vascular bed, the magnitude of the photoelectric pulse wave signal decreases and the There is a possibility that the elementary saturation cannot be measured accurately and stably.

The present invention has been made in view of the above circumstances, and its purpose is to accurately measure oxygen saturation regardless of individual differences of measurement subjects and differences in measurement sites. It is another object of the present invention to provide a reflection-type oximeter probe that can measure oxygen saturation with good accuracy and stability regardless of a decrease in peripheral circulation.

[0006]

[Means for Solving the Problems]

 The gist of the present invention for achieving the above-mentioned object is to sequentially irradiate the surface of a living body with a plurality of types of light having different wavelengths from a plurality of types of light emitting elements and to use a common light receiving element for the reflected light from the body. In the reflection-type oximeter that measures the oxygen saturation in blood based on the photoelectric pulse signal that indicates the intensity of the reflected light, each of the light-emitting elements has a plurality of light-receiving elements around the light-receiving element. A probe of a type in which an annular light-shielding member is arranged between the light-emitting element and the light-receiving element and that blocks the light reflected from the light-emitting element on the surface of the living body and traveling toward the light-receiving element. The light emitting element is provided around the light receiving element so that the distance between the light emitting element and the light receiving element gradually differs.

[0007]

[Effect of action and device]

 According to the probe for a reflection-type oximeter having such a configuration, a plurality of light-emitting elements that emit light of a plurality of types of wavelengths are provided around a common light-receiving element and the distance between the light-receiving elements and the common light-receiving element. Since they are arranged so as to be gradually different, a wide range of optimum detection depth of reflected light can be obtained. As a result, even if the depth position of the vascular bed from the surface of the living body varies due to individual differences in measurement subjects and differences in measurement sites, the magnitude of the photoelectric pulse wave signal can be sufficiently obtained and oxygen saturation can be accurately measured. In addition, even if the peripheral circulation decreases and reflected light is detected only from a deeper position in the vascular bed, the magnitude of the photoelectric pulse wave signal is sufficiently obtained to measure oxygen saturation accurately and stably. You can

[0008] Preferably, each minimum detection depth of the reflected light of each light emitting element detected by the light receiving element from the surface of the living body is equal to or more than the thickness of the epidermis constituting a part of the skin of the living body. Is decided. Thus, even if the distance between the light receiving element and each light emitting element is different, the minimum detection depth for each light emitting element is set to be equal to or greater than the thickness of the epidermis, so that the reflected light from the epidermis where blood vessels do not exist is received. Since it can be suitably avoided from being detected by the element, a large ratio of the AC component and the DC component of the photoelectric pulse wave signal can be secured, and the measurement accuracy of oxygen saturation can be further improved.

[0009]

【Example】

 An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 2 is a view showing an example of the configuration of a reflection oximeter including a probe to which the present invention is applied. The probe 10 is attached in a state of being in close contact with a body surface 12 such as a finger of a living body. To be done. As shown in FIGS. 1 and 2, the probe 10 includes a container-shaped housing 14 that is open in one direction, and a portion of the housing 14 that is located on the outer peripheral side of the inner surface of the bottom of the housing 14 alternately and annularly at predetermined intervals. For example, nine first light emitting elements 18 and second light emitting elements 20 each composed of LEDs and the like, and a bottom inner surface of the housing 14 on the inner peripheral side of the first light emitting element 18 and the second light emitting element 20. And a transparent resin 22 that is integrally provided in the housing 14 and covers the light receiving element 16 and the light emitting elements 18 and 20, and the light receiving element 16 in the housing 14. Is provided between the light emitting element 18 and the light emitting element 20, and the light emitted from the light emitting elements 18 and 20 travels from the body surface 12 toward the light receiving element 16. It is constituted by an annular light shielding member 24 for blocking light.

The first light emitting element 18 emits red light having a wavelength of, for example, about 660 nm, and the second light emitting element 20 emits infrared light having a wavelength of, for example, about 800 nm. There is no limitation, and any light having a wavelength at which the absorption coefficient of hemoglobin and the absorption coefficient of oxyhemoglobin differ greatly and light at a wavelength at which the absorption coefficients of both are substantially the same may be emitted. The first light-emitting element 18 and the second light-emitting element 20 are caused to sequentially emit light at a predetermined frequency for a certain period of time, and the light emitted from both the light-emitting elements 18 and 20 forms a vascular bed under the body surface 12, that is, That is, the reflected light from the portion where the thin blood vessels are densely arranged in the dermis that constitutes a part of the skin is received by the common light receiving element 16.

The light receiving element 16 outputs an electric signal SV having a magnitude corresponding to the amount of received light to the low pass filter 32 via the amplifier 30. This electric signal SV contains a fluctuation component due to the pulsation of the artery. The low-pass filter 32 removes noise having a frequency higher than the frequency of the pulse wave from the input electrical signal SV, and outputs the noise-removed signal SV to the demultiplexer 34. By demultiplexer 34 is switched in synchronism with the emission of the first light emitting element 18 and the second light emitting element 20 by switching signal SC will be described later, the electrical signal SV _R by the red light sample hold circuits 36 and A / D converter The electric signal SV _IR by infrared light is sequentially supplied to the I / O port 40 via the sampler circuit 38 and the I / O port 40 via the sample / hold circuit 42 and the A / D converter 44. The sample hold circuits 36 and 42, when sequentially outputting the input electric signals SV _R and SV _IR to the A / D converters 38 and 44, A / D the previously output electric signals SV _R and SV _IR. The electric signals SV _R and SV _IR to be output next are held respectively until the conversion operations of the converters 38 and 44 are completed.

The I / O port 40 is connected to the CPU 46, the ROM 48, the RAM 50, and the display 52 via a data bus line. The CPU 46 executes the measurement operation according to the program stored in the ROM 48 while utilizing the storage function of the RAM 50, and outputs the irradiation signal SLD from the I / O port 40 to the drive circuit 54 to output the irradiation signal SLD to the first light emitting element 18 and the first light emitting element 18. By causing the two light emitting elements 20 to sequentially emit light at a predetermined frequency for a certain period of time, the switching signal SC is output in synchronization with the light emission of the first light emitting element 18 and the second light emitting element 20 to switch the demultiplexer 34. the pre-Symbol electrical signal SV _R to a sample-and-hold circuit 36 distributes each said electrical signal SV _IR to sump Ruhorudo circuit 42. Further, CPU 46 may display the electrical signal SV _R and the electric signal SV _IR is based on the photoelectric pulse waveform representing respectively determining the oxygen saturation in the blood and the determined oxygen saturation according to a program stored in advance 52 To display. The method of determining the oxygen saturation is similar to the method of determining the oxygen saturation described in Japanese Patent Application Laid-Open No. 3-15440, which was filed by the applicant of the present application and published, for example. The oxygen saturation is determined on the basis of the actual ratio from the previously determined relationship with the saturation.

[0014]

[Equation 1]

In the above formula 1, V_dR, V_SRAre the upper peak value and the lower peak value of the photoelectric pulse waveform due to red light, respectively._dIR, V_SIRAre the upper and lower peak values of the photoelectric pulse waveform due to infrared light, respectively. Also, V_dR-V_SRAnd V_dIR-V_SIRRepresents the amplitude of the AC component of each photoelectron pulse waveform, and V_dR+ V_SRAnd V_dIR+ V _SIR Indicates that the DC component of each photoelectric pulse waveform is doubled.

Here, in this embodiment, further, the peripheral wall of the housing 14 and the light shielding member 24 each have an oval shape, and the light receiving element 16 has one end portion side on the inner peripheral side of the light shielding member 24. It is provided at a position biased to. As a result, the light emitting elements 18 and 20 are provided around the light receiving element 16 such that the distances between the light emitting element 18 and the light receiving element 16 are gradually different. Therefore, the intensity of the reflected light from the living body can be sufficiently high. The width of the optimum detection depth d _suit representing the depth from the body surface 12 to be obtained is wide. FIG. 3 shows a state in which the reflected light detection characteristics of the probe 10 are tested using a biological model in which a reflecting mirror 60 is placed on the bottom of a container 58 containing a suspension 56 of milk or the like. In the suspension 56, the distance d _model (corresponding to the detection depth of the reflected light from the living body) between the probe 10 and the reflecting mirror 60 is gradually changed from the light emitting elements 18 and 20 toward the reflecting mirror 60. When the light is irradiated, the intensity of the reflected light detected by the light receiving element 16 changes as shown in FIG. 4, for example, and the intensity of the reflected light from the reflecting mirror 60 is maximized. Was given. Therefore, it is estimated that the optimum detection depth d _suit can be wide even when the probe 10 is attached to the body surface 12.

Further, as the distance between the light receiving element 16 and the light emitting elements 18 and 20 increases, the thickness t 2 of the light shielding member 24 on the straight line connecting the light receiving element 16 and the light emitting elements 18 and 20 becomes, for example, It is gradually increased as indicated by t _{1 to} t _{4 in} FIG. As a result, the minimum detection depth d _min of the reflected light from each of the light emitting elements 18 and 20 detected by the light receiving element 16 from the body surface 12 is, for example, as shown in FIGS. At 20 they are identical to each other and are determined to be, for example, 0.35 mm.

As described above, according to this embodiment, the light emitting elements 18 and 20 are provided around the light receiving element 16 such that the distances between the light emitting elements 18 and 20 are gradually different, so that the optimum detection depth of the reflected light is obtained. d_suitSince a wide range can be obtained, the photoelectric pulse wave signal (SV _R , SV_IR) Is sufficient to measure oxygen saturation with high accuracy, and shock is applied to the living body by a scalpel or drug, which reduces peripheral circulation and causes reflection only from a deeper position in the vascular bed. Even if the light is not detected, the magnitude of the photoelectric pulse wave signal is sufficiently obtained, and the oxygen saturation can be measured accurately and stably.

By the way, the thickness of the epidermis of the human body is 0. Although it is known to be 3 mm or less, according to the present embodiment, the minimum detection depth d _{min for} each of the light emitting elements 18 and 20 is slightly smaller than 0.3 mm which is the maximum thickness of the skin of most of the parts. Since it is determined to be 0.35 mm, which is large, it is possible to surely prevent the light receiving element 16 from detecting the reflected light from the epidermis where the blood vessel does not exist. As a result, the ratio between the AC component and the DC component of the photoelectric pulse waveform, that is, (V _dR −V _SR ) / (V _dR + V _SR ) and (V _dIR −V _SIR ) / (V _dIR + V _SIR ) is large. As a result, the measurement accuracy of oxygen saturation is further improved.

In the above embodiment, the minimum detection depth d _{min for} each of the light emitting elements 18 and 20 is determined to be 0.35 mm, but this is not always necessary. For example, most parts of the human body Even if the maximum thickness of the skin is 0.3 mm or more, it is possible to obtain substantially the same effect as that of the above-mentioned embodiment.

Further, in the above-described embodiment, even when the minimum detection depth d _min is smaller than the thickness of the skin of the measurement subject, the distance between the light emitting elements 18 and 20 and the light receiving element 16 is gradually different from each other. By arranging around 16, the oxygen saturation can be measured accurately regardless of the individual difference of the subject and the difference of the measurement site, and the oxygen saturation can be measured with high accuracy regardless of the decrease of the peripheral circulation. The effect of the present invention that stable measurement can be obtained.

Further, in the above-described embodiment, the light receiving element 16 is provided at a position that is biased toward one end portion side on the inner peripheral side of the light shielding member 24 having an oval annular shape. The effect of the present invention can be obtained even when it is provided in the central portion on the side or when a cylindrical light shielding member is used.

Further, in the above-mentioned embodiment, the light emitting elements 18 and 20 are arranged so that the arrangement shape is an elliptical shape, but this is not always necessary, and for example, they may be arranged in a rhombic shape or a circular shape. Good. When the light emitting elements 18 and 20 are arranged in a circular shape, the light receiving element 16 is arranged at an eccentric position within the circumference. In short, the light emitting element may be provided around the light receiving element so that the distance between the light emitting element and the light receiving element gradually differs.

Further, in the above-described embodiment, the first light emitting element 18 and the second light emitting element 20 which emit two kinds of light having different wavelengths are alternately arranged, but this is not always necessary. A plurality of three or more types of light emitting elements that emit three or more different types of light may be arranged in a plurality such that the various types are substantially evenly distributed over the entire circumference.

Besides, the present invention can be variously modified without departing from the spirit thereof.

[Brief description of drawings]

FIG. 1 is an enlarged view of the probe of FIG. 2 viewed from the opening side of its housing.

FIG. 2 is a block diagram showing a configuration example of a reflection oximeter including a probe according to an embodiment of the present invention.

FIG. 3 is a diagram showing a state in which a reflected light detection characteristic of the probe of FIG. 2 is tested using a biological model having a reflecting mirror in suspension.

FIG. 4 is a diagram showing an example of reflected light detection characteristics of the probe of FIG. 2 obtained using the biological model of FIG.

5 is a diagram showing a minimum detection depth d _min of reflected light in a portion having a thickness t ₁ of the light shielding member in FIG.

FIG. 6 is a diagram showing a minimum detection depth d _min of reflected light at a thickness t ₂ portion of the light shielding member in FIG.

7 is a diagram showing a minimum detection depth d _min of reflected light in a portion of the light shielding member having a thickness t ₃ in FIG.

FIG. 8 is a diagram showing a minimum detection depth d _min of reflected light at a thickness t ₄ portion of the light shielding member in FIG.

[Explanation of symbols]

 10 probe 12 body surface 16 light receiving element 18 first light emitting element 20 second light emitting element 24 light shielding member

Claims (2)

[Scope of utility model registration request] 1. The intensity of the reflected light is obtained by sequentially irradiating the surface of a living body with a plurality of types of light having different wavelengths from a plurality of types of light emitting elements and detecting the reflected light from the living body with a common light receiving element. In a reflection-type oximeter for measuring oxygen saturation in blood based on a photoelectric pulse wave signal that represents, a plurality of light emitting elements are arranged around the light receiving element for each type, and the light emitting element and the light receiving element are arranged. A probe of a type in which an annular light shielding member that shields the light reflected from the light emitting element on the surface of the living body toward the light receiving element is provided between the light emitting element and the light receiving element. A probe for a reflection-type oximeter, characterized in that it is provided around the light-receiving element so that the distance between and is gradually different. 2. The reflection type oximeter probe according to claim 1, wherein the minimum detection depth from the living body surface of the reflected light for each light emitting element detected by the light receiving element is defined as one of the skins of the living body. A reflection type oximeter probe, characterized in that the thickness is equal to or greater than the thickness of the skin constituting the part.