JPH0549625A - Sensor for bloodless reflection type oximeter which can control optical detection depth - Google Patents

Abstract

PURPOSE:To optimize the range of the detection depth in the skin by setting the min. detection depth between the intersected point of a straight line connecting the 1st end of a light emitting chip and the 1st end of a light shielding wall and a straight line connecting the 2nd end of the light shielding wall and the 2nd end of a light receiving chip and the top face of the shielding wall larger than the skin thickness of the patient's skin. CONSTITUTION:A 1st ray 30 emitted from the upper left end of the light emitting chip 12 passes the upper left end of the light shielding wall 16 and is then partially reflected in the position of 0.35mm depth within the skin 18. The 1st reflected ray 32 passes the upper right end of the upper part of the light shielding wall 16 and is then received at the upper right end of the light receiving chip 10. This 0.35mm distance regulates the min. detection depth D which is the bottom end of the detection depth range 6. The 2nd ray 34 emitted from the upper right end of the light emitting chip 12 passes the upper left end of the light shielding wall 16 and is then partially reflected in the position of 0.70mm depth within the skin 18. The 2nd reflected ray 36 passes the upper right end of the light shielding wall 16 and is then received at the upper left end of the light receiving chip 10. This 0.79mm distance regulates the upper end M.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monitor device that can be used for measuring the oxygen saturation of arterial blood, and more particularly to adjusting the optical detection depth to measure the blood oxygen saturation in tissue with high accuracy. The present invention relates to an oximeter sensor including a geometric configuration capable of performing.

[0002]

2. Description of the Related Art A pulse oximeter is a device for measuring the oxygen saturation of hemoglobin in arterial blood. Recent devices employ optical techniques for non-invasive sensors used for measurement. The oximeter sensor illuminates a portion of the well-perfused tissue with at least two different wavelengths of light. The irradiated light reaches the hemoglobin contained in the red blood cells, and part of it is absorbed by the hemoglobin. The amount of light absorbed depends on the wavelength of the light applied and the degree of oxidation of hemoglobin. Therefore, by knowing the wavelength of the used light and the relative amount of the absorbed light, the blood oxygen saturation can be calculated.

Most of the currently available oximeters that employ optical techniques to measure blood oxygen saturation are transmission measurements. These devices transmit at least two kinds of wavelengths of light through a protrusion of a living body such as a finger or an ear lobe.
The oxygen saturation can be calculated by comparing the characteristics of the light transmitted to one side of the protrusion with the characteristics of the light detected on the opposite side. A major problem with transmission measurements is that they can only be used in living parts that are thin enough to allow the transmission of light. Further, when the patient is in a shock state, the terminal portion of the living body loses blood flow first, and the oxygen saturation cannot be measured.

Recently, there has been a great deal of interest in developing an oximeter capable of measuring oxygen saturation by utilizing reflected light of at least two kinds of wavelengths. In this device, the light source and the photodetector are located on the same side of the tissue and the photodetector receives only the light reflected in its own direction.

[0005]

The reflection type oximeter is advantageous in that it can measure the oxygen saturation even in a living body part which is not suitable for the transmission type measurement. In the conventional reflection type sensor, the reflected light signal is weaker than the transmitted light signal, but the reflection intensity is higher at the part closer to the surface of the skin, but the epidermis located on the surface of the skin is keratinized and capillaries. Since there is almost no blood vessel network, the reflected light from it does not contain pulsating components. For this reason, the measurement accuracy of blood oxygen saturation was not sufficiently obtained.

The present invention overcomes the problems of existing oximeter sensors. Therefore, the object of the present invention is to
It is an object of the present invention to provide a sensor for a reflection type oximeter, which has an optimized detection depth range in the skin.

[0007]

The gist of the present invention for achieving such an object is to provide a sensor for a reflection type oximeter having an adjusted light detection depth range in the skin of a patient. , (A) a light emitting chip having a first end and a second end located on the opposite side thereof and outputting light of a predetermined wavelength from between the first end and the second end,
(b) It has a first end on the light emitting chip side and a second end located on the opposite side, and receives the light reflected by the skin between the first end and the second end. A light-receiving chip; and (c) a first end portion on the light-emitting chip side and a second end portion on the light-receiving chip side, and a light-shielding wall arranged between the light-emitting chip and the light-receiving chip. An intersection of a straight line connecting the first end of the light emitting chip and the first end of the light shielding wall and a straight line connecting the second end of the light shielding wall and the second end of the light receiving chip, The minimum detection depth between the light shielding wall and the top surface is set to be larger than the epidermal thickness of the patient's skin.

[0008]

With this configuration, since the minimum detection depth is set to the abnormal skin thickness, the reflected light from inside the skin has a large reflection intensity and does not contain a pulsating component. Since the reflected light from is not included, the S / N ratio is enhanced and the measurement accuracy is suitably enhanced.

Here, as described above, the detection depth range of light in the skin is an important parameter when considering the reflection type measurement. For example, 0.35 to 0.70 m in the skin.
A detection range of a depth of m or more is considered to be optimal.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a detection depth range 6 defined by the illustrated configuration of the oximeter sensor as an embodiment of the present invention. Light emitting chip 12 such as LED
Has a rectangular cross section with approximately 0.5 mm on each side. Shading wall 16
Are arranged close to the light emitting chip 12 and have a width of about 0.
The height is 75 mm and the height is 1.9 mm. Further, the light-receiving chip 10 is arranged close to the light-shielding wall 16 and has a height of about 0.5 mm and a width of 2.0 mm.
It has a photosensitive portion with a width of about 1.0 mm centered on the center of.
The distance between the centers of the light emitting chip 12 and the light receiving chip 10 is about 3.0 mm, and the light shielding wall 16 and the light receiving chip 1
The center-to-center distance of 0 is about 2.0 mm.

In FIG. 1, the first light ray 30 emitted from the upper left end of the light emitting chip 12 passes through the upper left end of the light shielding wall 16 and is then partially reflected at a depth of 0.35 mm in the skin 18. It The first reflected light beam 32 due to this reflection passes through the upper right end of the light shielding wall 16 and is then received by the upper right end of the light receiving chip 10. The distance of 0.35 mm defines the lower end of the detection depth range 6, that is, the minimum detection depth D.

The second light ray 34 emitted from the upper right end of the light emitting chip 12 passes through the upper left end of the light shielding wall 16 and then the skin 1
It is partially reflected at a depth of 0.70 mm within 8.
The second reflected light ray 36 due to this reflection passes through the upper right end of the light shielding wall 16 and is then received by the upper left end of the light receiving chip 10. The distance of 0.70 mm defines the upper end M of the detection depth range 6.

Although only one LED of the light emitting chip 12 is shown in FIG. 1 as an example, as is well known to those skilled in the art, the reflection type pulse oximeter has at least two types of light emitting lights of different wavelengths. A light source is needed. The second light source is also arranged to have the above geometric relationship. For example, the light shielding wall 16 may be a right cylindrical columnar member provided around the light receiving chip 10, and at least two light sources having different wavelengths are provided outside the light shielding wall 16 at positions facing each other with respect to the light receiving chip 10. May be provided.

The invention is not limited to the use of two light sources. If it is desired to use a greater number of light sources, they may be arranged in a circle outside the cylindrical light shield wall 16 as shown in FIG. For example, the first group of light emitting chips 12 (LEDs) that emit light at the first predetermined wavelength are arranged at equal intervals on the circumference, and
Of the second group of light emitting chips 14 (LE
D) are arranged adjacent to each light emitting chip 12 of the first group on the same circumference and at equal intervals. Thus, until the light sources of all desired wavelengths are alternately arranged on the same circumference, the light sources 15 and 17 of the third and fourth wavelengths are arranged.
(LED) is similarly provided. In the embodiment shown in FIG. 2, four LEDs are used for each of the four wavelengths, and a total of 16 light sources are installed on the same circumference. However, as long as the above-mentioned geometrical relation for obtaining the desired detection depth range is ensured, the number of light sources or the number of kinds of wavelengths to be used can be changed from the embodiment of FIG.

FIG. 3 shows the positional relationship between the skin 18 and the light-receiving chip 10 and the protection made of an optically transparent and mechanically hard material provided to protect the light-emitting chip 12 and the light-receiving chip 10. The position of the member 20 is shown.

The skin 18 is composed of an epidermis whose surface is keratinized, a dermis which is a strong fibrous connective tissue under the epidermis, a subcutaneous tissue which holds skin fat in a mesh under the dermis and the like. The arteries form an arterial vascular network at the boundary between the subcutaneous tissue and the dermis and in the dermis, and enter the papilla as capillaries, bent into a loop and transferred to the vein.
The veins form a network of veins within the dermis and at the border between the dermis and the subcutaneous tissue, some of which enter the deep veins along the arteries and some of which enter the cutaneous veins. There is a particularly dense network of capillaries around the hair follicles and sweat glands. Further, in measuring the oxygen saturation, it is premised that the reflected light reflected by hemoglobin contains a pulsating component (AC component), and the pulsating component is weak compared to the direct current component, In order to maintain the measurement accuracy, it is necessary to clearly detect the pulsating component, and therefore it is desirable to detect the reflected light from the dermis and subcutaneous tissue where the arterial network exists. However, the reflected light from the inside of the skin 18 decreases exponentially as it goes deeper from the surface, and the reflected light from the epidermis without the vascular network is the strongest.
In some cases, the / DC ratio was not sufficiently obtained, and it was difficult to maintain the accuracy of oxygen saturation.

In this embodiment, as described above, the minimum detection depth D is 0.35 which is at least larger than the epidermis thickness of the skin 18.
It is set to mm, and the AD / DC ratio of reflected light is increased. In humans, the skin is 0.1 to 0.3 (excluding Heibonsha World Encyclopedia), except for the extra thick parts such as soles and palms.
Is 0.35 mm or less at the site where the oxygen saturation is measured. In addition, since the density of the blood vessel network is low and the blood vessels are thin near the boundary between the epidermis and the dermis, the minimum detection depth D is
Desirably, it is 0.5 mm or more, more desirably 1.2 mm or more, and especially when it is limited to an adult, the reflected light having a higher AD / DC ratio can be obtained when it is limited to around 1.5 mm.

As is apparent from the above description, according to the present invention, the detection depth range can be obtained at a desired depth and thickness. The distance between the light emitting chip 12 and the light receiving chip 10, the respective heights of the light emitting chip 12 and the light receiving chip 10, the height and width of the light shielding wall 16, and the like define various nominal values of the detection depth range in the skin 18. Be understood.

From the above disclosure and teachings, other embodiments and modifications of this invention will be readily apparent to those skilled in the art. That is, it should be understood that the present invention can be carried out in addition to the above description within the technical scope thereof. The present invention, in addition to the specific embodiments detailed above,
Various changes can be made without departing from the spirit and scope of the invention.

[Brief description of drawings]

FIG. 1 is a geometrical explanatory view of a detection depth range defined by a light source, a light shielding wall, and a photodetector to which the present invention is applied.

FIG. 2 is a plan view of an embodiment of the sensor for a reflective oximeter of the present invention.

3 is a cross-sectional view of the embodiment of FIG. 2 taken along the line AA.

[Explanation of Codes] 6: Detection depth range 10: Photodetector 12: Light emitting chip 14: Light emitting chip 16: Light shielding wall 30: First light beam 32: First reflected light beam 34: Second light beam 36: Second Reflected rays of

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ronald El Brands Tetter United States Texas 78240 San Antonio Traceback 7226

Claims (1)

[Claims] 1. A sensor for a reflective oximeter having an adjusted light detection depth range in a patient's skin, the sensor having a first end and a second end located opposite the first end.
A light emitting chip that outputs light of a predetermined wavelength from between the first end portion and the second end portion; a first end portion on the light emitting chip side and a second end portion on the opposite side; A light-receiving chip for receiving the light reflected by the skin between the first end and the second end, a first end on the light-emitting chip side and a second end on the light-receiving chip side
A light-shielding wall that is provided between the light-emitting chip and the light-receiving chip, and a straight line that connects the first end of the light-emitting chip and the first end of the light-shielding wall. The minimum detection depth between the intersection of the second end of the light shielding wall and the straight line connecting the second end of the light receiving chip and the top surface of the light shielding wall is smaller than the epidermal thickness of the patient's skin. A reflective oximeter sensor characterized by being set large.