CN115530817A - Method and device for measuring central venous blood oxygen saturation - Google Patents
Method and device for measuring central venous blood oxygen saturation Download PDFInfo
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- CN115530817A CN115530817A CN202110735932.0A CN202110735932A CN115530817A CN 115530817 A CN115530817 A CN 115530817A CN 202110735932 A CN202110735932 A CN 202110735932A CN 115530817 A CN115530817 A CN 115530817A
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- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
- A61B5/1455—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters
- A61B5/14551—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue using optical sensors, e.g. spectral photometrical oximeters for measuring blood gases
Abstract
A measuring device and a measuring method for the degree of blood oxygen saturation of a central venous blood comprise a central venous catheter, a first wafer, a second wafer and a photoelectric device, wherein the first wafer and the second wafer are arranged on the central venous catheter, the photoelectric device is used for collecting optical signals, the first wafer and the second wafer are respectively used for emitting at least two paths of light rays with different wavelengths to blood to be measured so as to obtain a corresponding first light intensity ratio and a corresponding second light intensity ratio, and a signal processing circuit is used for calculating the degree of blood oxygen saturation of the blood to be measured according to the first light intensity ratio and the second light intensity ratio; among the light rays emitted by the first wafer and the second wafer, the value of the optical signal intensity corresponding to at least one path of light ray is smaller than the values of the optical signal intensities corresponding to other paths of light rays, so that at least one light intensity ratio to be obtained is increased. The measuring method improves the measuring accuracy of the blood oxygen saturation by increasing at least one light intensity ratio to be obtained.
Description
Technical Field
The invention relates to the technical field of medical machinery, in particular to a method and a device for measuring the oxygen saturation of central venous blood.
Background
Blood oxygen saturation (SaO) 2 ) Is oxyhemoglobin (HbO) bound by oxygen in blood 2 ) The percentage of total bindable hemoglobin (Hb) volume, i.e. the concentration of blood oxygen in the blood, is an important physiological parameter of the respiratory cycle. Wherein the central venous oxygen saturation (ScvO) 2 ) Is the blood oxygen saturation measured by using a central venous catheter. The oxygen saturation of the venous blood is directly measured by using a specific device in the central venous catheter, and the method has the advantages of no increase of any risk of a patient, simple and convenient operation, economy, applicability and the like. In measuring the oxygen saturation of blood with a central venous catheter, a catheter containing monitoring ScvO may be used 2 Continuously monitoring ScvO 2 So as to dynamically reflect the oxygen supply consumption level of tissues and organs, accurately evaluate whether the cell function and the internal environment are stable, further guide the clinical treatment to avoid the tissue hypoxia and the consequent organ failure, and also can be based on ScvO 2 The effectiveness of the treatment and the prognosis of the treatment are established, and therefore, the use of the central venous catheter to measure the oxygen saturation of the central venous blood has irreplaceable clinical value.
The existing method for measuring the oxygen saturation of central venous blood is mainly to arrange an optical fiber penetrating through a medical instrument cavity in a central venous catheter, the optical fiber is contacted with blood at the tail end of the central venous catheter, then, a transmitting optical fiber in the optical fiber can periodically transmit red light and infrared light, the red light and the infrared light are reflected by cells, then, a receiving optical fiber in the optical fiber carries out digital processing on the received light intensity, and further, scvO (scattered oxygen) is calculated 2 . But due to factors such as blood flow velocity and Hct value (hematocrit) on ScvO 2 The effect is large, and when the state of the patient fluctuates greatly, the measurement result needs to be calibrated. Since the intensity of light reflected by the red blood cells in the body that it receives will be much less than the intensity of light emitted towards the red blood cells, the receiving fiber will receive lightThe intensity of the received light is affected by many factors, such as blood flow rate, blood PH, and hematocrit (Hct), in addition to the different absorption characteristics of oxygenated hemoglobin and reduced hemoglobin. Particularly, hct has a large influence on the measured value at low oxygen saturation, and how to further improve the measurement accuracy of the central venous blood oxygen saturation is one of the problems to be solved or improved at present.
Disclosure of Invention
According to a first aspect, an embodiment discloses a device for measuring central venous blood oxygen saturation, comprising:
a central venous catheter having a distal end for insertion into a central vein, the central venous catheter comprising a lumen;
the first wafer is positioned on the outer wall of the cavity and used for emitting at least two paths of light rays with different wavelengths to blood to be detected, the at least two paths of light rays are used for forming optical signals through reflection of the blood to be detected, and the at least two paths of light rays are used for obtaining a first light intensity ratio through the ratio of the respective optical signal intensities;
the second wafer is positioned on the inner wall of the cavity and used for emitting at least two paths of light rays with different wavelengths to blood to be detected, the at least two paths of light rays are used for penetrating the blood to be detected to form optical signals, and the at least two paths of light rays are used for obtaining a second light intensity ratio through the ratio of the respective optical signal intensities;
the photoelectric device comprises a first sensor and a second sensor, wherein the first sensor is positioned on the outer wall of the cavity body, the second sensor is positioned on the inner wall of the cavity body, the first sensor and the first wafer are arranged in parallel and used for collecting and outputting optical signals formed by reflection of blood to be detected, and the second sensor and the second wafer are arranged oppositely and used for collecting and outputting optical signals formed by transmission of the blood to be detected;
the signal processing circuit is respectively coupled to the output ends of the first sensor and the second sensor, and is used for receiving and processing the optical signals output by the first sensor and the second sensor to obtain a first light intensity ratio and a second light intensity ratio and calculating the blood oxygen saturation of the blood to be detected according to the first light intensity ratio and the second light intensity ratio; among the light rays emitted by the first wafer and the second wafer, the value of the optical signal intensity corresponding to at least one path of light ray is smaller than the values of the optical signal intensities corresponding to other paths of light rays, so that at least one light intensity ratio to be obtained is increased.
According to a second aspect, an embodiment provides a central venous blood oxygen saturation measurement method, comprising:
emitting at least two paths of light rays with different wavelengths to blood to be detected in the central vein;
obtaining optical signals obtained by at least two paths of light rays after the action of blood to be detected, wherein the at least two paths of light rays are used for obtaining at least one light intensity ratio according to the ratio of the respective optical signal intensities;
calculating the ratio of the light signal intensity of the light with larger wavelength to the light with smaller wavelength in the at least two paths of light so as to increase at least one light intensity ratio to be obtained;
and calculating the blood oxygen saturation of the blood to be detected according to at least one light intensity ratio.
According to a third aspect, an embodiment provides a central venous blood oxygen saturation measurement apparatus, comprising:
a central venous catheter, the end of which is for insertion into a central vein:
the wafer is positioned at the tail end of the central venous catheter and used for emitting at least one path of light to blood to be detected;
the photoelectric device is positioned at the tail end of the central venous catheter and used for receiving the at least one path of light acted by the blood to be detected so as to obtain at least one optical signal;
and the signal processing circuit is in signal connection with the photoelectric device and is used for calculating the blood oxygen saturation of the blood to be measured according to the intensity of at least one optical signal.
In the above embodiment, at least two light beams with different wavelengths are emitted to the blood to be measured in the central venous catheter, and the ratio of the light signal intensity of the light beam with the larger wavelength to the light signal intensity of the light beam with the smaller wavelength in the at least two light beams is calculated to increase at least one light intensity ratio to be obtained, and then the central venous blood oxygen saturation is calculated according to the at least one light intensity ratio. In the calculation of the central venous blood oxygen saturation, the higher the light intensity ratio, the lower the blood oxygen saturation of the same blood to be measured and the closer the blood oxygen saturation to the true value, so the method improves the measurement precision of the central venous blood oxygen saturation.
Drawings
FIG. 1 is a schematic view of a central venous catheter of one embodiment;
FIG. 2 is a schematic view of a first base according to an embodiment;
FIG. 3 is a schematic view of a second base according to an embodiment;
FIG. 4 is a schematic view of a third base according to an embodiment;
FIG. 5 is a schematic diagram of a signal processing circuit of an embodiment;
FIG. 6 is a schematic diagram of a computational processing circuit according to an embodiment;
FIG. 7 is a flow chart of a method of measuring central venous blood oxygen saturation according to an embodiment;
100. a central venous catheter;
110. a cavity; 120. a first base; 130. a second base; 140. a third base;
200. a first wafer;
300. a second wafer;
410. a first sensor;
420. a second sensor;
500. a signal processing circuit;
510. a signal amplifying/conditioning circuit; 520. an analog-to-digital conversion circuit; 530. and a calculation processing circuit.
Detailed Description
The present invention will be described in further detail with reference to the following detailed description and accompanying drawings. Wherein like elements in different embodiments have been given like element numbers associated therewith. In the following description, numerous details are set forth in order to provide a better understanding of the present application. However, those skilled in the art will readily recognize that some of the features may be omitted or replaced with other elements, materials, methods in different instances. In some instances, certain operations related to the present application have not been shown or described in this specification in order not to obscure the core of the present application with unnecessary detail, and it is not necessary for those skilled in the art to describe these operations in detail, so that they may be fully understood from the description in the specification and the general knowledge in the art.
Furthermore, the features, operations, or characteristics described in the specification may be combined in any suitable manner to form various embodiments. Also, the various steps or actions in the description of the methods may be transposed or transposed in order, as will be apparent to a person skilled in the art. Thus, the various sequences in the specification and drawings are for the purpose of describing certain embodiments only and are not intended to imply a required sequence unless otherwise indicated where such sequence must be followed.
The numbering of the components as such, e.g., "first", "second", etc., is used herein only to distinguish the objects as described, and does not have any sequential or technical meaning. The term "connected" and "coupled" when used in this application, unless otherwise indicated, includes both direct and indirect connections (couplings).
The most important concept of the invention is that: (1) the oxygen saturation of the central venous blood is calculated through the light intensity ratio, and at least one path of light with smaller wavelength is emitted, so that the measurement precision is improved; (2) the wafer is used as a light-emitting piece, so that errors are reduced; (3) the transmission type oxyhemoglobin saturation measuring method and the reflection type oxyhemoglobin saturation measuring method are combined, and the measuring precision is further improved.
Referring to fig. 1 to 5, the present embodiment provides a central venous blood oxygen saturation measurement apparatus, which includes a central venous catheter 100, a first wafer 200, a second wafer 300, an optoelectronic device, and a signal processing circuit 500.
The central venous catheter 100 is one of the intravascular tubes, and has a distal end for insertion into a central vein and contact with blood. The central venous catheter 100 may have one or more lumens 110 as is known in the art, and the central venous catheter 100 will be described below as having a single lumen 110.
The first wafer 200 is located on the outer wall of the chamber 110, and the first wafer 200 is used to emit two paths of light with different wavelengths to the blood to be measured. In other embodiments, the first wafer 200 may also emit more than two light beams, that is, the first wafer 200 may emit at least two light beams. As shown in fig. 1 to 2, a first pedestal 120 is mounted on an outer wall of the chamber body 110, and two first wafers 200 are mounted on the first pedestal 120. In this embodiment, the wavelength of one light emitted from the first wafer 200 is λ 1, and the wavelength of the other light emitted from the first wafer 200 is λ 2. The two light beams are used for forming two optical signals collected by the photoelectric device through the reflection of blood to be measured.
The second wafer 300 is located on the inner wall of the cavity 110 and is used for emitting two paths of light with different wavelengths to the blood to be measured. In other embodiments, the second wafer 300 may also emit more than two light beams, that is, the second wafer 300 may emit at least two light beams in this application. As shown in fig. 1 and 3, a second pedestal 130 is mounted on the inner wall of the chamber 110, and two second wafers 300 are mounted on the second pedestal 130. In this embodiment, the wavelength of one light emitted from the second wafer 300 is λ 3, and the wavelength of the other light emitted from the second wafer 300 is λ 4. The two paths of light are used for transmitting blood to be detected to form optical signals collected by the photoelectric device.
The optoelectronic device includes a first sensor 410 positioned on an outer wall of the chamber 110 and a second sensor 420 positioned on an inner wall of the chamber 110, respectively. As shown in fig. 2, the first sensor 410 is also installed on the first pedestal 120, the first sensor 410 is installed in parallel with the first wafer 200, the first sensor 410 is used for collecting and outputting an optical signal formed by reflecting blood to be measured to the signal processing circuit 500, that is, light emitted from the first wafer 200 will be transmitted through the blood to be measured and reflected by the blood to be measured, and the first sensor 410 only collects the optical signal formed by reflecting blood therein. For example, as shown in fig. 1 and 4, a third base 140 opposite to the second base 130 is disposed on one side of the inner wall of the cavity 110, the second sensor 420 is mounted on the third base 140, the second sensor 420 is configured to collect and output an optical signal formed after transmission of blood to be measured to the signal processing circuit 500, that is, light emitted from the second wafer 300 can pass through the blood to be measured and can be reflected by the blood to be measured, and the second sensor 420 only collects the optical signal formed by the light passing through the blood.
The existing measuring device for the central venous blood oxygen saturation is mainly to arrange a transmitting optical fiber and a receiving optical fiber in a cavity 110 of a central venous catheter 100, wherein the transmitting optical fiber is in contact with blood and periodically transmits red light and infrared light, and the transmitted light is reflected by cells and then received by the receiving optical fiber. Since blood flows in a pulsating manner through the blood vessel, the optical fiber in the central venous catheter 100 can move uncontrollably, which in turn affects the intensity of light received by the receiving optical fiber.
Compared with the existing measuring device for the central venous blood oxygen saturation, the structure of the measuring device has the following advantages:
(1) The wafer is used as a light emitting member. The volume of the wafer is small, so that the light emitting element in the measuring device can be directly disposed at the end of the central venous catheter 100, that is, the first wafer 200 is located on the outer wall of the cavity 110, and the second wafer 300 is located on the inner wall of the cavity 110. Because the light-emitting component is arranged on the central venous catheter 100, uncontrolled swinging can not occur, thereby avoiding the light intensity received by the photoelectric device from being influenced and causing the calculation error of the subsequent central venous blood oxygen saturation.
(2) The transmission type blood oxygen measuring mode and the reflection type blood oxygen measuring mode are combined in the same measuring device, so that the error possibly brought by a single measuring mode is further reduced.
The signal processing circuit 500 is coupled to the output ends of the first sensor 410 and the second sensor 420, respectively, and is configured to receive and process the optical signals output by the first sensor 410 and the second sensor 420, and the signal processing circuit 500 is configured to obtain a first optical intensity ratio according to the optical signal intensity of the light emitted from the first wafer 200 and obtain a second optical intensity ratio according to the optical signal intensity of the light emitted from the second wafer 300. Then, the signal processing circuit 500 calculates the blood oxygen saturation of the blood to be measured according to the first light intensity ratio and the second light intensity ratio. In the light emitted from the first wafer 200 and the second wafer 300, the value of the optical signal intensity corresponding to at least one path of light is smaller than the value of the optical signal intensity corresponding to other paths of light. As an example, the first wafer 200 emits light with wavelengths λ 1 and λ 2, and the second wafer 300 emits light with wavelengths λ 3 and λ 4. Wherein, the optical signal intensity of the light with the wavelength λ 1 is I1, the optical signal intensity of the light with the wavelength λ 2 is I2, the optical signal intensity of the light with the wavelength λ 3 is I3, the optical signal intensity of the light with the wavelength λ 4 is I4, and the relationship between the four optical signal intensities may be that I1 > I2 and I3 > I4, then the first optical intensity ratio may be: I1/I2, the second light intensity ratio may be: I3/I4, where I3 may equal I2, or I4 may equal I2.
Through the setting of the light signal intensity, the signal processing circuit 500 can increase the obtained light intensity ratio, and through theoretical and actual verification, the measurement precision under the low oxygen saturation can be improved after the light intensity ratio is increased, so that the measurement accuracy of the central venous blood oxygen saturation is improved. The above method for calculating the blood saturation according to the light intensity ratio may adopt an existing algorithm or an algorithm which may appear in the future.
In some embodiments, the wavelength of at least one of the light beams emitted from the first wafer 200 and/or the second wafer 300 is smaller than the wavelength of the other light beams, and the signal processing circuit 500 is further configured to increase the ratio of the light signal intensities of the light beams with the larger wavelength and the light beams with the smaller wavelength in the at least two light beams of the same wafer. For example, in the light emitted from the first wafer 200 and the second wafer 300, λ 1 is smaller than λ 2, λ 3 and λ 4, respectively, so that the first light intensity ratio may be: I2/I1.
The measuring device in the above embodiment emits at least one path of light signals with low wavelength, and theoretical and practical verification proves that in cell biology, the absorption degree of light with small wavelength, such as oxyhemoglobin and reduced hemoglobin, is larger, and the signal processing circuit 500 determines the calculation mode of the light intensity ratio according to the wavelength, so that the light intensity ratio to be obtained can be increased.
In some embodiments, as shown in fig. 5 (which shows the coupling of the signal processing circuit 500 to the second sensor 420), the signal processing circuit 500 includes a signal amplifying/conditioning circuit 510, an analog-to-digital conversion circuit 520, and a calculation processing circuit 530, which are connected in series.
The signal amplifying/conditioning circuit 510 is connected to the output terminals of the first sensor 410 and the second sensor 420, respectively. After the first sensor 410 and the second sensor 420 collect the optical signals, the optical signals are sent to the signal amplifying/conditioning circuit 510 in the form of electrical signals, the signal amplifying/conditioning circuit 510 may amplify and otherwise process (e.g., filter) the electrical signals, and the analog-to-digital conversion circuit 520 performs analog-to-digital conversion on the amplified signals and then outputs the signals to the calculation processing circuit 530.
One specific structure of the calculation processing circuit 530 is shown in fig. 6, and the calculation processing circuit 530 includes a plurality of dividers (1 a, 2a, 3a, and 4 a), multipliers (1 b and 2 b), amplifiers (1 c, 2c, 3c, 4c, 5c, 6c, 7c, 8c, 9c, and 10 c), adders (1 f, 2f, 3f, and 4 f), and other necessary electronic components. In the figure, the analog-to-digital conversion circuit 520 outputs the optical signal intensity I1 and the optical signal intensity I2 to the divider 1a, and outputs the optical signal intensities I3 and I4 to the divider 2a, wherein the wavelength λ 1 of the light corresponding to the optical signal intensity I1 is greater than the wavelength λ 2 of the light corresponding to the optical signal intensity I2, and the wavelength λ 3 of the light corresponding to the optical signal intensity I3 is greater than the wavelength λ 4 of the light corresponding to the optical signal intensity I4. With the divider 1a, a first intensity ratio can be obtained, which is: I1/I2. A second intensity ratio can be obtained by means of the divider 2a, the second intensity being I3/I4.
The signal output by divider 1a is applied to multiplier 1b to obtain the square of the first intensity ratio and the signal output by divider 2a is applied to multiplier 2b to obtain the square of the second intensity ratio. The amplifier 1c processes the signal output from the multiplier x with an appropriate gain and a calibration factor A2, thereby obtaining a signal A2 (I1/I2) 2 Similarly, the amplifier 2c processes the signal output from the multiplier by a calibration factor B2 to obtain a signal B2 (I1/I2) 2 Similarly, the amplifier 3c and the amplifier 4c are respectively provided with appropriate onesThe gain and calibration coefficients A1 and B1 amplify the first light intensity ratio to obtain a signal A1 (I1/I2) and a signal B1 (I1/I2). Similarly, the amplifier 5C, the amplifier 6C, the amplifier 7C, and the amplifier 8C output signals C2 (I3/I4), respectively 2 、D2(I3/I4) 2 C1 (I3/I4) and D1 (I3/I4). Voltage source 1d works with resistor 1e and resistor 2e to generate signal A0. An output signal is then generated at adder 1 f: a0+ A1 (I1/I2) + A2 (I1/I2) 2 . Similarly, the output signals are generated by the adder 2f, the adder 3f, the adder 4f, and the adder 5 f: b0+ B1 (I1/I2) + B2 (I1/I2) 2 、C0+C1(I3/I4)+C2(I3/I4) 2 And D0+ D1 (I3/I4) + D2 (I3/I4) 2 。
Further outputting a first calculation value of oxygen saturation of blood by the divider 3a, and outputting a second calculation value of oxygen saturation of blood by the divider 4a, wherein the first calculation value of oxygen saturation of blood is:
the second calculated blood oxygen saturation value is:
after obtaining the first calculated value of blood oxygen saturation and the second calculated value of blood oxygen saturation, the signal processing circuit 500 further performs weighted average on the first calculated value of blood oxygen saturation and the second calculated value of blood oxygen saturation through the amplifier 9c and the amplifier 10c to obtain the blood oxygen saturation of the blood to be measured. In fig. 6, the central venous oxygen saturation is:
wherein Q1 and Q2 are weight coefficients of the first blood oxygen saturation calculated value and the second blood oxygen saturation calculated value, respectively, and the sum of Q1 and Q2 is 1. In some embodiments, the weighting coefficients are determined based on historical trends of the blood oxygen saturation of the blood under test. For example, over a plurality of measurements, the measurement device can obtain a true average of the historical trend, and if the obtained calculation value of the blood oxygen saturation is largely different from the true average, the weight coefficient is small.
The signal processing circuit 500 having the above-described configuration can eliminate measurement errors caused by various factors as much as possible by performing weighted averaging on the calibration coefficients and the obtained calculated value of the blood oxygen saturation level, thereby obtaining a more accurate measurement result.
Referring to fig. 7, the present invention further provides a method for measuring central venous blood oxygen saturation, including the steps of:
and S10, emitting at least two paths of light rays with different wavelengths to the blood to be detected in the central vein.
In this step, the light with different wavelengths may be emitted by the existing emitting optical fiber, or the light with different wavelengths emitted by the wafer in the previous embodiment may be used.
And S20, obtaining optical signals obtained by the action of at least two paths of light rays on blood to be detected, wherein the at least two paths of light rays are used for obtaining at least one light intensity ratio through the ratio of the respective optical signal intensities.
In this step, the optical signal obtained by the action of the blood to be measured may be an optical signal obtained after the blood to be measured is transmitted through the blood to be measured, or an optical signal obtained after the blood to be measured is reflected. In some embodiments, the optical signal obtained by the action of the blood to be measured includes both the optical signal obtained after the blood to be measured passes through and the optical signal obtained after the blood to be measured reflects, so that the method for obtaining the blood oxygen saturation in the transmission type and the reflection type can be combined to obtain a more accurate measurement result.
Step S30, calculating the ratio of the light signal intensity of the light with larger wavelength to the light with smaller wavelength in the at least two paths of light so as to increase at least one light intensity ratio to be obtained.
In some embodiments, in step S10, one path of light with a wavelength λ 1 and another path of light with a wavelength λ 2 are emitted to the blood to be measured, where λ 1 > λ 2, the optical signal intensity of the light with the wavelength λ 1 is I1, and the optical signal intensity of the light with the wavelength λ 2 is I2, then the light intensity ratio obtained according to the two paths of light is: I1/I2.
In other embodiments, in addition to the light with the wavelengths λ 1 and λ 2, the light with the wavelength λ 3 is emitted to the blood to be measured in step S10, the light has the corresponding optical signal intensity I3, and there is a relationship: λ 1 > λ 2 > λ 3. Then, based on the obtained intensity ratio of the three rays, in addition to the above I1/I2, two other intensity ratios can be included: I1/I3 and I2/I3.
How to obtain the corresponding light intensity ratio when the light is multiplexed can be deduced reasonably from the above two examples, and the description thereof is omitted here.
And S40, calculating the blood oxygen saturation of the blood to be detected according to at least one light intensity ratio.
In this step, the method of calculating the blood saturation according to the light intensity ratio may adopt an existing algorithm or an algorithm that may appear in the future.
In some embodiments, when the light with different wavelengths includes at least three light rays, the at least three light rays can form at least N light ray groups, where N is greater than or equal to 2, each light ray group can obtain a corresponding light intensity ratio, and the light intensity ratio corresponding to each light ray group is a ratio of light signal intensities of light rays with larger wavelengths to light rays with smaller wavelengths in the light ray group. One way to calculate the central venous oxygen saturation is to:
firstly, calculating according to each light intensity ratio to obtain a corresponding calculated value of the blood oxygen saturation, and then carrying out weighted average on the calculated values of the N blood oxygen saturation to obtain the blood oxygen saturation of the blood to be detected.
Specifically, the formula for obtaining the calculated value of the blood oxygen saturation according to the ith light intensity ratio is as follows:
wherein Si is calculated value of blood oxygen saturation obtained according to ith light intensity ratio, i is greater than or equal to 1 and less than or equal to N, A i0 、A i1 、A i2 、B i0 、B i1 And B i2 The calibration coefficients are preset calibration coefficients respectively, and each calibration coefficient can be obtained through clinical tests. R is i For the ith intensity ratio, the calculation formula of the ith intensity ratio is as follows:
wherein, I i1 The light intensity I of the light with larger wavelength in the ith light group after the blood to be measured acts on i2 The light intensity of the light with smaller wavelength in the ith light group is obtained after the blood to be measured acts on the light. And then, carrying out weighted average on the S to finally obtain the blood oxygen saturation of the blood to be measured. For example, the finally obtained central venous blood oxygen saturation can be obtained by the following formula:
wherein, scvO 2 The Qi is the weighting coefficient corresponding to the ith calculated value of blood oxygen saturation. In some embodiments, the weighting coefficients are determined based on historical trends of the blood oxygen saturation of the blood under test. For example, over a plurality of measurements, the measurement device can obtain a true average of the historical trend, and if the obtained calculated value of blood oxygen saturation differs greatly from the true average, the weight coefficient is small.
The embodiment improves the measurement precision of the central venous blood oxygen saturation by increasing the light intensity ratio, and in addition, the wafer is used as a light-emitting piece, and transmission measurement and reflection measurement are combined, so that the measurement error is further reduced, and the calibration times are reduced or subsequent recalibration is not needed.
Those skilled in the art will appreciate that all or part of the functions of the methods in the above embodiments may be implemented by hardware, or may be implemented by a computer program. When all or part of the functions of the above embodiments are implemented by a computer program, the program may be stored in a computer-readable storage medium, and the storage medium may include: a read only memory, a random access memory, a magnetic disk, an optical disk, a hard disk, etc., and the program is executed by a computer to realize the above functions. For example, the program may be stored in a memory of the device, and when the program in the memory is executed by the processor, all or part of the functions described above may be implemented. In addition, when all or part of the functions in the above embodiments are implemented by a computer program, the program may be stored in a storage medium such as a server, another computer, a magnetic disk, an optical disk, a flash disk, or a portable hard disk, and may be downloaded or copied to a memory of a local device, or may be version-updated in a system of the local device, and when the program in the memory is executed by a processor, all or part of the functions in the above embodiments may be implemented.
The present invention has been described in terms of specific examples, which are provided to aid in understanding the invention and are not intended to be limiting. For a person skilled in the art to which the invention pertains, several simple deductions, modifications or substitutions may be made according to the idea of the invention.
Claims (11)
1. A device for measuring central venous blood oxygen saturation, comprising:
a central venous catheter having a distal end for insertion into a central vein, the central venous catheter comprising a lumen;
the first wafer is positioned on the outer wall of the cavity and used for emitting at least two paths of light rays with different wavelengths to blood to be detected, the at least two paths of light rays are used for forming optical signals through reflection of the blood to be detected, and the at least two paths of light rays are used for obtaining a first light intensity ratio through the ratio of the respective optical signal intensities;
the second wafer is positioned on the inner wall of the cavity and used for emitting at least two paths of light rays with different wavelengths to blood to be detected, the at least two paths of light rays are used for forming optical signals through the blood to be detected, and the at least two paths of light rays are used for obtaining a second light intensity ratio through the ratio of the respective optical signal intensities;
the photoelectric device comprises a first sensor and a second sensor, the first sensor is positioned on the outer wall of the cavity body, the second sensor is positioned on the inner wall of the cavity body, the first sensor and the first wafer are arranged in parallel and used for collecting and outputting optical signals formed by reflection of blood to be detected, and the second sensor and the second wafer are arranged oppositely and used for collecting and outputting optical signals formed by transmission of the blood to be detected;
the signal processing circuit is respectively coupled to the output ends of the first sensor and the second sensor, and is used for receiving and processing the optical signals output by the first sensor and the second sensor to obtain a first light intensity ratio and a second light intensity ratio and calculating the blood oxygen saturation of the blood to be detected according to the first light intensity ratio and the second light intensity ratio; among the light rays emitted by the first wafer and the second wafer, the value of the optical signal intensity corresponding to at least one path of light ray is smaller than the values of the optical signal intensities corresponding to other paths of light rays, so that at least one light intensity ratio to be obtained is increased.
2. The measurement apparatus according to claim 1, wherein the wavelength of at least one of the light beams emitted from the first wafer and/or the second wafer is smaller than the wavelengths of the other light beams, and the signal processing circuit is further configured to increase the ratio of the optical signal intensities of the light beams with the larger wavelength and the light beams with the smaller wavelength in the at least two light beams of the same wafer, so as to increase the ratio of the light intensities to be obtained.
3. The measuring device according to claim 1, wherein calculating the blood oxygen saturation level of the blood to be measured according to the first light intensity ratio and the second light intensity ratio comprises:
calculating a first blood oxygen saturation calculation value according to the first light intensity ratio;
calculating a second calculated value of the blood oxygen saturation according to the second light intensity ratio; and
and carrying out weighted average on the first blood oxygen saturation calculation value and the second blood oxygen saturation calculation value to obtain the blood oxygen saturation of the blood to be detected.
4. A central venous blood oxygen saturation measurement method is characterized by comprising the following steps:
emitting at least two paths of light rays with different wavelengths to blood to be detected in the central vein;
obtaining optical signals obtained by at least two paths of light rays after the action of blood to be detected, wherein the at least two paths of light rays are used for obtaining at least one light intensity ratio through the ratio of the respective optical signal intensities;
calculating the ratio of the optical signal intensity of the light with larger wavelength to the optical signal intensity of the light with smaller wavelength in the at least two paths of light so as to increase at least one light intensity ratio to be obtained;
and calculating the blood oxygen saturation of the blood to be detected according to at least one light intensity ratio.
5. The method of claim 4, wherein the light of different wavelengths emitted toward the blood under test comprises at least three light rays, the at least three light rays being used to form at least two light ray groups, each light ray group comprising two light rays of different wavelengths, each light ray group being used to obtain an intensity ratio, the method further comprising:
calculating the ratio of the light signal intensity of the light with larger wavelength to the light with smaller wavelength in the at least two light ray groups so as to increase the at least two light intensity ratios to be obtained;
and calculating the blood oxygen saturation of the blood to be detected according to the at least two light intensity ratios.
6. The method of claim 5, wherein calculating the blood oxygen saturation level of the blood to be measured from the at least two intensity ratios comprises:
calculating at least two calculated values of the blood oxygen saturation according to at least two light intensity ratios, wherein one calculated value of the blood oxygen saturation is obtained based on one light intensity ratio;
and carrying out weighted average on the at least two calculated values of the blood oxygen saturation to obtain the blood oxygen saturation of the blood to be detected.
7. The method of claim 6, wherein in the weighted averaging to obtain the blood oxygen saturation, the weight coefficient of each calculation value of the blood oxygen saturation is determined based on a historical trend of the blood oxygen saturation of the blood to be measured.
8. The method of claim 6, wherein the calculated value of the blood oxygen saturation is obtained from the ith intensity ratio by the following formula:
wherein Si is a calculated value of the oxygen saturation of blood obtained from the ith light intensity ratio, i is not less than 1 and not more than the number of the obtained light intensity ratios, A i0 、A i1 、A i2 、B i0 、B i1 And B i2 Respectively, a preset calibration coefficient, R i For the ith light intensity ratio, the calculation formula of the ith light intensity ratio is as follows:
wherein, I i1 The light intensity, I, of the light with larger wavelength in the ith light group after the blood to be measured acts i2 The light intensity of the light with smaller wavelength in the ith light group is obtained after the light with smaller wavelength is acted by the blood to be measured.
9. The method according to claim 5, wherein at least one of the at least two light beams with different wavelengths is used for transmitting the blood to be measured to form an optical signal, and at least one of the at least two light beams is used for reflecting the blood to be measured to form an optical signal.
10. The method of claim 4, wherein emitting at least two different wavelengths of light to the blood to be measured in the central vein comprises:
and emitting two paths of light rays with different wavelengths to the blood to be detected in the central vein by using the wafer at the tail end of the central venous catheter inserted into the central vein.
11. A central venous oxygen saturation measurement device, comprising:
a central venous catheter, the end of which is for insertion into a central vein:
the wafer is positioned at the tail end of the central venous catheter and used for emitting at least one path of light to blood to be detected;
the photoelectric device is positioned at the tail end of the central venous catheter and used for receiving the at least one path of light acted by the blood to be detected so as to obtain at least one optical signal;
and the signal processing circuit is in signal connection with the photoelectric device and is used for calculating the blood oxygen saturation of the blood to be measured according to the intensity of at least one optical signal.
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