WO2015161687A1

WO2015161687A1 - Method for measuring blood oxygen saturation and portable device

Info

Publication number: WO2015161687A1
Application number: PCT/CN2015/070723
Authority: WO
Inventors: 辛勤
Original assignee: 辛勤
Priority date: 2014-04-24
Filing date: 2015-01-15
Publication date: 2015-10-29
Also published as: CN104068865B; CN104068865A

Abstract

Disclosed is a method for measuring blood oxygen saturation, wherein the method comprises: sending a first measurement light, a second measurement light and a reference light to the body surface skin (10) of the object to be measured, and receiving the reflected light of the first measurement light, the second measurement light and the reference light (S101); obtaining a first difference value and a second difference value, wherein the first difference value is the difference in the rate of change of the light intensity between the first reflected light and the reference reflected light, and the second difference value is the difference in the rate of change of the light intensity between the reference reflected light and the second reflected light (S102); and obtaining, by calculation, the ratio x of the first difference value and the second difference value, and calculating the blood oxygen saturation y in accordance with the ratio x (S103). Accordingly, disclosed is a portable device (20) for measuring blood oxygen saturation. Using the above-mentioned method and the portable device (20), the real-time accurate measurement of blood oxygen saturation can be achieved.

Description

Method for measuring blood oxygen saturation and portable device

Technical field

The invention belongs to the field of physiological parameter measurement, and in particular relates to a method for measuring blood oxygen saturation and a portable device.

Background technique

Oxygen is an important element in maintaining normal physiological activities of the human body. Oxygen in the air enters the bloodstream after being exchanged with the lungs of the human body, and is transmitted to the whole body by binding to hemoglobin. Hemoglobin consists of four chains, two alpha chains and two beta chains, each of which has a cyclic heme containing an iron atom. Oxygen is bound to the iron atoms and transported by the blood. Each gram of hemoglobin can bind 1.34 ml of oxygen, which is 70 times the amount of dissolved oxygen in plasma.

The oxygen saturation (SO2) based on oxyhemoglobin (HbO2) and reduced hemoglobin characterizes the state of oxygen circulation in human body and is an important parameter for judging human respiratory and circulatory systems. Oxygen saturation is the percentage of oxygen-bound oxyhemoglobin in the blood that accounts for the total capacity of the combined hemoglobin (Hb), the concentration of blood oxygen in the blood. The blood oxygen saturation of normal human arterial blood is 98%, and venous blood is 75%. Generally, the normal value of SpO2 should be no less than 94%, and below 94% is insufficient oxygen supply.

The hazard of hypoxia is related to the degree of hypoxia, the rate of occurrence and duration. The first thing that occurs during hypoxia is compensatory heart rate acceleration, increased heart rate and cardiac output, and the circulatory system compensates for the lack of oxygen in a high-power state. At the same time, blood flow redistribution occurs, and the brain and coronary vessels are selectively expanded to ensure adequate blood supply. Severe hypoxia, endocardial lactic acid accumulation, ATP (adenosine triphosphate) synthesis is reduced, resulting in myocardial inhibition, leading to bradycardia, premature contraction, decreased blood pressure and decreased cardiac output, and arrhythmia such as ventricular fibrillation Even stop. Therefore, real-time monitoring of blood oxygen saturation is very important.

In order to avoid damage to the human body caused by blood sampling, it is now mainly used to detect blood oxygen saturation by non-invasive detection methods that do not cause damage to the human body. Non-invasive blood oxygen saturation detection is divided into two methods: transmissive and reflective. Among them, the transmissive method analyzes blood oxygen saturation by acquiring transmitted light passing through human tissues, and since the transmitted light signal is strong and the measurement accuracy is high, the method is currently in use. The bed has been widely used. However, the transmissive method is suitable for applications where the skin is thin, so that the light is transmitted, and thus the application site is limited. The reflective method acquires the light intensity signal reflected by the human tissue, so that the probe is not limited by the placement position, and has a broader application prospect. However, the current method for measuring blood oxygen saturation by reflection is not accurate and the error is large.

Summary of the invention

In order to solve the problem of low accuracy and low efficiency of the existing method for reflective measurement of blood oxygen saturation, the present invention provides a method for measuring blood oxygen saturation.

According to an aspect of the invention, a method of measuring blood oxygen saturation is provided, wherein the method comprises the steps of:

a) transmitting first measurement light, second measurement light and reference light to the body surface skin of the object to be measured, and receiving the first measurement light, the second measurement light, and the reflected light of the reference light;

b) obtaining a first difference and a second difference, wherein

The first difference is a difference between a light intensity change rate of the first reflected light and the reference reflected light;

The second difference is a difference between a light intensity change rate of the reference reflected light and the second reflected light;

c) obtaining a ratio x of the first difference value and the second difference value by calculation, and calculating a blood oxygen saturation y according to the ratio value x.

According to a specific embodiment of the present invention, the step c) is further:

Obtaining a ratio x of the first difference value and the second difference value by calculation, and calculating a blood oxygen saturation degree y according to the ratio x by using a formula y=nx+m; wherein n>0; 0< m<100.

According to another embodiment of the invention,

The wavelength of the first measurement light is 660 nm ± 3 nm;

The wavelength of the second measurement light is 940 nm ± 10 nm;

The wavelength of the reference light is 820 ± 10 nm.

According to still another embodiment of the present invention, the body surface skin is a wrist surface skin corresponding to the radial artery of the measured object.

According to another aspect of the present invention, a portable device for measuring blood oxygen saturation is provided, wherein the portable device comprises: a light emitting and light receiving module, a computing module, and a processing module;

The light emitting and receiving module is configured to send a first measurement to a body surface skin of the object to be measured Light, second measurement light and reference light, and received light of the first measurement light, the second measurement light, and the reference light;

a calculating module, configured to calculate and obtain a first difference value and a second difference value, wherein the first difference value is a difference between a light intensity change rate of the first reflected light and the reference reflected light,

The second difference is a difference between a reference reflected light intensity and a second reflected light intensity change rate;

And a processing module, configured to calculate and obtain a ratio x of the first difference value and the second difference value, and calculate a blood oxygen saturation y according to the ratio value x.

According to an embodiment of the present invention, the processing module calculates the blood oxygen saturation y according to the ratio x, specifically: calculating the blood oxygen saturation y according to the ratio x by using the formula y=nx+m ;

Where n>0; 0<m<100.

According to another embodiment of the invention,

The wavelength of the first measurement light is 660 nm ± 3 nm;

The wavelength of the second measurement light is 940 nm ± 10 nm;

The wavelength of the reference light is 820 nm ± 10 nm.

According to yet another embodiment of the invention, the portable device has a wrist-worn structure.

According to still another embodiment of the present invention, the portable device further includes:

A display module for displaying the blood oxygen saturation.

The present invention firstly transmits measurement light and reference light to the body surface skin of the object to be measured, and then receives the reflected light of the measurement light and the reference light, and calculates the blood oxygen of the measured object by using the light intensity change rate of each of the reflected light beams. saturation. The reflection method is used to obtain the light intensity signal reflected by the test part of the object to be tested, and the light intensity signal is strong, so the test probe is not limited by the placement position, and is more flexible. The reference light is added during the test, which can effectively remove the absorption of the test light by the inherent absorption rate of the object to be measured, so that the measurement result is more accurate.

DRAWINGS

Other features, objects, and advantages of the present invention will become more apparent from the Detailed Description of Description

1 is a schematic flow chart showing a specific embodiment of a method for measuring blood oxygen saturation according to the present invention;

Figure 2 shows the relationship between wavelength and absorption coefficient;

3 is a block diagram showing the construction of a portable device for measuring blood oxygen saturation according to the present invention.

The same or similar reference numerals in the drawings denote the same or similar components.

detailed description

The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. In order to simplify the disclosure of the present invention, the components and arrangements of the specific examples are described below. Furthermore, the present invention may repeat reference numerals and/or letters in different examples. This repetition is for the purpose of simplicity and clarity, and is not in the nature of the description of the various embodiments and/or arrangements discussed. It is noted that the components illustrated in the drawings are not necessarily drawn to scale. The description of the known components and processing techniques and processes is omitted to avoid unnecessarily limiting the present invention.

Referring to Figure 1, there is shown a flow diagram of one embodiment of a method of measuring blood oxygen saturation provided in accordance with the present invention.

The oxygen saturation measurement is based on the amount of light absorbed by arterial blood as a function of arterial pulsation. When the arterial blood vessels in the light-transmitting region pulsate, the absorption of light by the arterial blood will change, and the absorption of light by other tissues such as skin, muscle, bone and venous blood will remain unchanged. Specifically, the method for measuring blood oxygen saturation provided by the present invention is mainly applied to humans, and thus the measured object is mainly referred to herein as a human in need of blood oxygen saturation measurement. Those skilled in the art will appreciate that the method of measuring blood oxygen saturation provided by the present invention can also be applied to the measurement of blood oxygen saturation of a mammal having the same or similar physiological characteristics as humans.

Step S101, transmitting first measurement light, second measurement light and reference light to the body surface skin of the object to be measured, and receiving the first measurement light, the second measurement light, and the reflected light of the reference light.

The reflection method used in the present invention measures blood oxygen saturation, and the specific principle is to transmit light to human tissues. The wave, which is reflected by the human body to generate reflected light, then receives the reflected light and analyzes the physiological condition of the human body reflected by the reflected light, thereby achieving the purpose of measuring blood oxygen saturation of the human body.

Referring to Fig. 2, the absorption peak of oxyhemoglobin in the red region (600 nm to 700 nm) is weak. The absorption peak of reduced hemoglobin in the infrared region (850 nm to 1000 nm) is weak. The rate of change of light intensity caused by transmission and reflection is equal and proportional to the absorption coefficient. Therefore, preferably, the first measurement light has a wavelength of 660 nm ± 3 nm, for example: 657 nm, 660 nm or 663 nm. Preferably, the second measuring light has a wavelength of 940 nm ± 10 nm, for example: 930 nm, 940 nm or 950 nm.

In order to eliminate the error, a third beam of light is added as a reference light during the measurement. At the wavelength of the third beam, oxyhemoglobin and reduced hemoglobin have the same light absorption rate, which can eliminate the interference of the inherent state of the human body on the change of light intensity. Preferably, the reference light has a wavelength of 820 ± 10 nm, for example: 810 nm, 820 nm or 830 nm.

Preferably, the body surface skin is the wrist surface skin corresponding to the radial artery of the object to be measured.

The emission of the two beams of measurement and one beam of reference light can be achieved using three different lasers or with an integrated laser. In addition, the light emission and reception can also be realized by a photoelectric sensor, for example, by using an NJL5501R chip, which is a photoelectric sensor that can generate red light and infrared light.

Step S102, acquiring a first difference value and a second difference value, wherein the first difference value is a difference between a light intensity change rate of the first reflected light and the reference reflected light; and the second difference is a reference reflected light and The difference in the rate of change of the intensity of the second reflected light. It can be understood that the first reflected light is the reflected light of the first measuring light; the second reflected light is the reflected light of the second measuring light; and the reference reflected light is the reflected light of the reference light.

The above calculation process requires the digital reflected mode chip or device to convert the first reflected light, the second reflected light and the reference reflected light into a digital signal. There are many types of chips that can implement digital-to-analog conversion. If the NJL5501R chip is used to implement light emission and light reception in step S101, since the hardware structure for digital-to-analog conversion is already included in the NJL5501R chip, no additional chip or device is needed. Implement digital to analog conversion.

After the conversion, the light intensity change rate of the first reflected light is denoted by a, the light intensity change rate of the reference reflected light is denoted by b, and the light intensity change rate of the second reflected light is denoted by c. Then the first difference is b-a and the second difference is c-b.

Step S103, obtaining a ratio x of the first difference value and the second difference value by calculation, and Based on the ratio x, the blood oxygen saturation y is calculated. Preferably, blood oxygen saturation is calculated using the formula y=nx+m; wherein n>0; 0<m<100. As can be seen from the description of step S102, the ratio x = (b - a) / (c - b). According to the ratio x, the blood oxygen saturation y can be obtained by using a single chip microcomputer. In the prior art, a plurality of single-chip microcomputers can realize calculation of digital signals to generate physiological parameters, for example, MK20DN512VLK10 chip. It can be understood that in the present invention, the physiological parameter refers to blood oxygen saturation y, blood oxygen saturation y = nx + m.

Where n>0, for example, may take values of 1, 3, 5, etc.; 0 < m < 100, for example, may take values of 2, 40, 57, and the like.

Referring to Figure 3, there is shown a block diagram of a portable device for measuring blood oxygen saturation in accordance with the present invention.

The portable device 20 includes a light emitting and light receiving module 21, a computing module 21, and a processing module 22.

The light emitting and receiving module 21 is configured to send first measurement light, second measurement light and reference light to the body surface skin 10 of the object to be measured, and receive the first measurement light, the second measurement light, and The reflected light of the reference light. Preferably, the body surface skin 10 of the object to be measured is the skin surface of the wrist corresponding to the radial artery of the object to be measured.

Preferably, the wavelength of the first measurement light is 660 nm±3 nm, for example: 657 nm, 660 nm or 663 nm. Preferably, the second measuring light has a wavelength of 940 nm ± 10 nm, for example: 930 nm, 940 nm or 950 nm.

Preferably, the light emitting and receiving module 21 is a photoelectric sensor, for example, an NJL5501R chip, which is a photoelectric sensor that can generate red light and infrared light.

The calculating module 22 is configured to calculate and obtain a first difference value and a second difference value, wherein the first difference value is a difference between a light intensity change rate of the first reflected light and the reference reflected light, and the second difference is The difference between the light intensity change rates of the reference reflected light and the second reflected light. The first reflected light is the emitted light of the first measuring light; the second reflected light is the emitted light of the second measuring light; the reference reflected light is the reflected light of the reference light.

The computing module 22 can be a chip or device capable of digital to analog conversion, such as the NJL5501R chip. In the NJL5501R chip, there is a hardware structure that can realize digital-to-analog conversion. After the conversion, the light intensity change rate of the first reflected light is denoted by a, the light intensity change rate of the reference reflected light is denoted by b, and the light intensity change rate of the second reflected light is denoted by c. Then the first difference is b-a and the second difference is c-b.

The processing module 23 is configured to calculate and obtain a ratio x of the first difference value and the second difference value, and calculate a blood oxygen saturation y according to the ratio value x. Preferably, blood oxygen saturation is calculated using the formula y=nx+m; wherein n>0; 0<m<100. The ratio x = (b - a) / (c - b), blood oxygen saturation y = y = nx + m. Where n>0, for example, may take values of 1, 3, 5, etc.; 0 < m < 100, for example, may take values of 2, 40, 57, and the like.

The blood oxygen saturation y is obtained according to the ratio x, which can be implemented by using a single chip microcomputer. Therefore, the processing module 23 can be a single chip microcomputer or other embedded device that can implement digital signal calculation. Preferably, the processing module 23 is a MK20DN512VLK10 chip.

In addition, the above calculation module 22 and the processing module 23 can also be implemented by a dedicated calculator or a dedicated processor such as a CPU.

In order to meet the requirement of measuring blood oxygen saturation in real time, the portable device 20 needs to be carried at any time, and has an artery under the skin to which it is attached, and further, it cannot affect the normal activity of the measured object by carrying the portable device 20. Thus, preferably, the portable device 20 has a wrist-worn structure.

Preferably, the portable device 20 further includes: a display module for displaying the blood oxygen saturation to provide a real-time blood oxygen saturation value for the carrier. In addition, the display module can also display general parameters such as time.

The method of measuring blood oxygen saturation provided by the present invention and using the portable device provided by the present invention can accurately and in real time measure the blood oxygen saturation of a test object by a reflective method.

While the invention has been described with respect to the preferred embodiments and the embodiments of the present invention, it is understood that various changes, substitutions and modifications may be made to the embodiments without departing from the spirit and scope of the invention. For other examples, those of ordinary skill in the art will readily appreciate that the order of process steps may vary while remaining within the scope of the invention.

Further, the scope of application of the present invention is not limited to the process, mechanism, manufacture, composition of matter, means, methods and steps of the specific embodiments described in the specification. From the disclosure of the present invention, It will be readily understood by those skilled in the art that the processes, mechanisms, manufactures, compositions, means, methods, or steps that are presently present or later will be developed, wherein they are substantially identical to the corresponding embodiments described herein. The functions are either substantially the same, and they can be applied in accordance with the invention. Therefore, the appended claims are intended to cover such modifications, such structures, structures,

Claims

A method of measuring blood oxygen saturation, wherein the method comprises the steps of:

a) transmitting first measurement light, second measurement light and reference light to the body surface skin of the object to be measured, and receiving the first measurement light, the second measurement light, and the reflected light of the reference light;

b) obtaining a first difference and a second difference, wherein

The first difference is a difference between a light intensity change rate of the first reflected light and the reference reflected light;

The second difference is a difference between a light intensity change rate of the reference reflected light and the second reflected light;

c) obtaining a ratio x of the first difference value and the second difference value by calculation, and calculating a blood oxygen saturation y according to the ratio value x.
The method of claim 1 wherein said step c) is further:

Obtaining a ratio x of the first difference value and the second difference value by calculation, and calculating a blood oxygen saturation degree y according to the ratio value x by using a formula y=nx+m;

Where n>0; 0<m<100.
The method of claim 1 wherein

The wavelength of the first measurement light is 660 nm ± 3 nm;

The wavelength of the second measurement light is 940 nm ± 10 nm;

The wavelength of the reference light is 820 ± 10 nm.
The method according to claim 1, wherein the body surface skin is a wrist body surface skin corresponding to the radial artery of the measured object.
A portable device for measuring blood oxygen saturation, wherein the portable device comprises: a light emitting and light receiving module, a computing module, and a processing module;

The light emitting and receiving module is configured to send first measurement light, second measurement light and reference light to the body surface skin of the object to be measured, and receive the first measurement light, the second measurement light, and the The reflected light of the reference light;

a calculating module, configured to calculate and obtain a first difference value and a second difference value, wherein the first difference value is a difference between a light intensity change rate of the first reflected light and the reference reflected light,

The second difference is a difference between a light intensity change rate of the reference reflected light and the second reflected light;

And a processing module, configured to calculate and obtain a ratio x of the first difference value and the second difference value, and calculate a blood oxygen saturation y according to the ratio value x.
The portable device according to claim 5, wherein the processing module calculates the blood oxygen saturation y according to the ratio x, specifically: calculating blood oxygen using the formula y=nx+m according to the ratio x Saturation y;

Where n>0; 0<m<100.
The portable device according to claim 5, wherein

The wavelength of the first measurement light is 660 nm ± 3 nm;

The wavelength of the second measurement light is 940 nm ± 10 nm;

The wavelength of the reference light is 820 nm ± 10 nm.
The portable device according to claim 5, wherein the body surface skin is a wrist body surface skin corresponding to the radial artery of the measured object.
The portable device of claim 5, wherein the portable device has a wrist-worn structure.
The portable device of claim 5, wherein the portable device further comprises:

A display module for displaying the blood oxygen saturation.