Extracorporeal membrane oxygenation (ECMO) based hematocrit and blood oxygen saturation detection method and device

Abstract

The application discloses a hematocrit and blood oxygen saturation detection method and device based on ECMO, and relates to the technical field of ECMO.The method is as follows: under a first set condition, a first electric signal and a second electric signal are acquired, the first set condition being a condition of controlling a light source to emit light source signals of different wavelengths to blood in a flow cell; under a second set condition, a third electric signal and a fourth electric signal are acquired, the second set condition being a condition of controlling the light source to be turned off; a first difference value and a second difference value are respectively calculated, wherein the first difference value is a difference value between the first electric signal and the third electric signal, and the second difference value is a difference value between the second electric signal and the fourth electric signal; and hematocrit values and blood sample saturation values are respectively calculated according to the first difference value and the second difference value.The hematocrit and the blood oxygen saturation can be detected in real time by using a non-contact and non-invasive method.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ECMO, in particular to a hematocrit and blood oxygen saturation detection method and device based on ECMO. BACKGROUND

[0002] Extracorporeal Membrane Oxygenation (ECMO) is mainly to provide continuous extracorporeal respiration and circulation function for patients with heart and lung failure and other related critical illnesses, so as to maintain the life of the critical patient, wherein the changes of blood oxygen and other indicators in the blood are important basis for the operation of ECMO system and the evaluation and diagnosis of doctors on patients.

[0003] In the implementation process of the existing ECMO system, the detection of blood oxygen saturation and hematocrit needs manual blood sampling analysis. For the detection method relying on manual blood sampling, medical staff needs to collect and test blood at regular intervals and frequently, the whole process takes a long time, and it cannot reflect the blood index situation in real time. SUMMARY

[0004] The purpose of the present application is to provide a hematocrit and blood oxygen saturation detection method and device based on ECMO, which can detect hematocrit and blood oxygen saturation in real time by non-contact and non-invasive method.

[0005] To achieve the above purpose, the present application provides the following scheme:

[0006] In a first aspect, the present application provides a hematocrit and blood oxygen saturation detection method based on ECMO, the ECMO at least comprising a flow cell, the method comprising:

[0007] Under a first set condition, a first electric signal and a second electric signal are obtained; wherein the first set condition is a condition of controlling the light source to emit light source signals of different wavelengths to the blood inside the flow cell; the first electric signal is a signal output by the first photodetector after the light source signal is reflected by the flow cell; and the second electric signal is a signal output by the second photodetector after the light source signal is reflected by the flow cell;

[0008] Under a second set condition, a third electric signal and a fourth electric signal are obtained; wherein the second set condition is a condition of controlling the light source to be off; the third electric signal is a signal output by the first photodetector when there is no light source signal; and the fourth electric signal is a signal output by the second photodetector when there is no light source signal;

[0009] calculating a first difference value and a second difference value; wherein the first difference value is a difference value between the first electrical signal and the third electrical signal; and the second difference value is a difference value between the second electrical signal and the fourth electrical signal;

[0010] calculating a hematocrit value and an oxygen saturation value according to the first difference value and the second difference value, respectively.

[0011] Optionally, the hematocrit value is calculated according to the following formula:

[0012] Hct = a1 x lg(A1 / B1) + b1;

[0013] wherein Hct is the hematocrit value, a1 and b1 are first equation coefficients, A1 is the first difference value corresponding to a wavelength, and B1 is the second difference value corresponding to the wavelength.

[0014] Optionally, the oxygen saturation value is calculated according to the following formula:

[0015] SO2 = [a2 x lg(A2 / B2) + b2] x Hct;

[0016] wherein SO2 is the oxygen saturation value, a2 and b2 are second equation coefficients, A2 is the first difference value corresponding to another wavelength, and B2 is the second difference value corresponding to the another wavelength.

[0017] Optionally, the first equation coefficients are determined according to the following method:

[0018] pre-measuring a hematocrit value of blood by using a blood gas analyzer;

[0019] determining the first difference value and the second difference value corresponding to a wavelength;

[0020] determining the first equation coefficients by linear fitting the hematocrit value of blood, the first difference value and the second difference value corresponding to the wavelength using a least square method.

[0021] Optionally, the second equation coefficients are determined according to the following method:

[0022] pre-measuring a hematocrit value and an oxygen saturation value of blood by using a blood gas analyzer;

[0023] determining the first difference value and the second difference value corresponding to another wavelength;

[0024] determining the second equation coefficients by linear fitting the hematocrit value, the oxygen saturation value, the first difference value and the second difference value corresponding to the another wavelength using a least square method.

[0025] In a second aspect, the present application provides an ECMO-based hematocrit and blood oxygen saturation detection device, comprising: a light source, a first photodetector, a second photodetector, and a controller.

[0026] The light source is configured to emit light source signals of different wavelengths to the blood in the flow cell.

[0027] The first photodetector is configured to output a first electrical signal and a third electrical signal.

[0028] The second photodetector is configured to output a second electrical signal and a fourth electrical signal.

[0029] The controller is connected to the light source, the first photodetector, and the second photodetector, and is configured to execute the ECMO-based hematocrit and blood oxygen saturation detection method.

[0030] Optionally, the ECMO-based hematocrit and blood oxygen saturation detection device further comprises a communication unit.

[0031] The communication unit is connected to the controller and is configured to complete information transmission between the controller and an ECMO host.

[0032] Optionally, the first photodetector and the second photodetector are arranged at different positions of the light source, and an optical path difference can be formed.

[0033] Optionally, the number of the first photodetector and the second photodetector is single or multiple.

[0034] Optionally, the distance from the first photodetector to the light source is not equal to the distance from the second photodetector to the light source.

[0035] According to the specific embodiments of the present application, the following technical effects are provided:

[0036] The ECMO-based hematocrit and blood oxygen saturation detection method and device provided by the application comprises the following steps: obtaining a first electric signal and a second electric signal under a first set condition, wherein the first set condition is a condition of controlling the light source to emit light source signals of different wavelengths to the blood in the flow cell, the first electric signal is a signal output by the first photodetector after the light source signal is reflected by the flow cell, and the second electric signal is a signal output by the second photodetector after the light source signal is reflected by the flow cell; obtaining a third electric signal and a fourth electric signal under a second set condition, wherein the second set condition is a condition of controlling the light source to be turned off, the third electric signal is a signal output by the first photodetector when there is no light source signal, and the fourth electric signal is a signal output by the second photodetector when there is no light source signal; calculating a first difference value and a second difference value, wherein the first difference value is a difference between the first electric signal and the third electric signal, and the second difference value is a difference between the second electric signal and the fourth electric signal; and calculating a hematocrit value and a blood sample saturation value according to the first difference value and the second difference value. The detection method and device adopt a non-contact non-invasive method to perform real-time detection on the hematocrit and the blood oxygen saturation. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0038] Figure 1 The flow chart of the ECMO-based hematocrit and blood oxygen saturation detection method of the embodiment of the present application;

[0039] Figure 2 The structural block diagram of the ECMO-based hematocrit and blood oxygen saturation detection device of the embodiment of the present application.

[0040] Symbol explanation:

[0041] The first photodetector-1, the second photodetector-2, the light source-3, the flow cell-4, the controller-5, and the communication unit-6. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0043] The purpose of this invention is to provide a method and device for detecting hematocrit and blood oxygen saturation based on ECMO, which can detect hematocrit and blood oxygen saturation in real time in a non-contact and non-invasive manner.

[0044] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] Example 1

[0046] This embodiment discloses a method for detecting hematocrit and blood oxygen saturation based on ECMO, such as... Figure 1 As shown, it specifically includes:

[0047] Before testing begins, the device needs to be installed on a flow cell 4 with a specific structure. The flow cell 4 is made of hollow tubular hard plastic. The two sides of the flow cell 4 are connected to the pagoda interfaces of the ECMO blood circulation tubing. The flow cell 4 has a plane and window with a good viewing angle in the middle, which allows the light source 3 to emit a laser beam into the blood in the flow cell 4.

[0048] Step 101: Under the first set conditions, acquire the first electrical signal and the second electrical signal. The first set conditions are the conditions for controlling the light source 3 to emit light source signals of different wavelengths into the blood inside the flow cell 4; the first electrical signal is the signal output after the light source signal is reflected by the flow cell 4 and collected by the first photodetector 1; the second electrical signal is the signal output after the light source signal is reflected by the flow cell 4 and collected by the second photodetector 2.

[0049] Step 102: Under the second set condition, acquire the third and fourth electrical signals. The second set condition is the condition for controlling the light source 3 to turn off; the third electrical signal is the signal output by the first photodetector 1 when there is no light source; the fourth electrical signal is the signal output by the second photodetector 2 when there is no light source.

[0050] Step 103: Calculate the first difference and the second difference; wherein the first difference is the difference between the first electrical signal and the third electrical signal; and the second difference is the difference between the second electrical signal and the fourth electrical signal.

[0051] Step 104: Calculate the hematocrit value and blood oxygen saturation value based on the first and second differences. Specifically, first, substitute the first and second differences corresponding to one wavelength into the formula for calculating the hematocrit value to obtain the hematocrit value. Then, substitute the obtained hematocrit value and the first and second differences corresponding to another wavelength into the formula for calculating the blood oxygen saturation value to obtain the blood sample saturation value, where:

[0052] The formula for calculating hematocrit is:

[0053] Hct = al x lg (Al / B1) + bl.

[0054] The formula for calculating the blood oxygen saturation value is:

[0055] SO2 = [a2 x lg (A2 / B2) + b2] x Hct.

[0056] In the formula, Hct is the hematocrit value, SO2 is the blood oxygen saturation value, al and bl are the first equation coefficients, a2 and b2 are the second equation coefficients, Al is the first difference value corresponding to a wavelength, B1 is the second difference value corresponding to a wavelength, A2 is the first difference value corresponding to another wavelength, and B2 is the second difference value corresponding to another wavelength.

[0057] Further, it is known that the majority of blood components are water and red blood cells, and that oxyhemoglobin and reduced hemoglobin in water and red blood cells have different absorption coefficients for different 500nm-1300nm light sources. According to the further development of Tewelsky's Lambert-Beer law, for a specific wavelength:

[0058] lg (I0 / I) = K Oxy x SO2 x L x Hct + K Deoxy x (1-SO2) x L x Hct + K p x L x (1-Hct) + S + T.

[0059] In the formula, I0 is the incident light intensity, I is the transmitted light intensity, K Oxy is the absorption index of oxyhemoglobin, K Deoxy is the absorption index of reduced hemoglobin, K p is the absorption index of plasma, L is the light path length, S is a constant depending on particle size, light source parameters, wavelength, light aperture, plasma and red blood cell refractive index, and T is a constant determined by non-blood parameters.

[0060] According to the near-infrared spectral characteristics of oxyhemoglobin, reduced hemoglobin and water, at 805nm wavelength or 1300nm wavelength, or even at the relatively flat 850nm, the absorption coefficients of oxyhemoglobin and reduced hemoglobin are almost the same, so K Oxy is equal to K Deoxy , which is K R . Therefore:

[0061] lg (I0 / I) = K R x L x Hct + K p x L x (1-Hct) + S + T.

[0062] If two photoelectric detectors have asymmetric or unequal optical paths to the same light source at the same time, then:

[0063] lg(I1 / I2) = ΔL x (K R -K p ) x Hct + ΔL x K p .

[0064] where I1 and I2 are the light intensity data received by the first photoelectric detector 1 and the second photoelectric detector 2 respectively at the same light source and the same time, ΔL is the difference between the optical path lengths formed by the first photoelectric detector 1 and the second photoelectric detector 2 respectively and the light source 3, K R is the absorption coefficient of hemoglobin.

[0065] According to the above analysis, lg(I1 / I2) and Hct have an approximate linear relationship, and thus the calculation formula of the hematocrit value can be obtained as follows:

[0066] Hct = a1 x lg(A1 / B1) + b1.

[0067] After obtaining the calculation formula of the hematocrit value, a plurality of groups of calibration data need to be collected through experiments to fit the values of a1 and b1. Specifically, the blood hematocrit value is measured in advance by using a blood gas analyzer, and the first difference and the second difference corresponding to a wavelength are determined, and the least squares method is used to linearly fit the blood hematocrit value, the first difference and the second difference corresponding to the wavelength, to determine the first equation coefficient.

[0068] In addition, according to the near-infrared spectral characteristics of oxyhemoglobin, reduced hemoglobin and water, it is known that the absorption coefficients of oxyhemoglobin and reduced hemoglobin are quite different near 660 nm, and the absorption coefficient of water is approximately 0 at 900 nm-600 nm. Then:

[0069] lg(I1 / I2) = ((K Oxy -K Deoxy ) x SO2 + K Deoxy ) x Hct x ΔL.

[0070] According to the above analysis, lg(I1 / I2) and SO2 have an approximate linear relationship, and thus the calculation formula of the blood oxygen saturation value can be obtained as follows:

[0071] SO2 = [a2 x lg(A2 / B2) + b2] x Hct.

[0072] After obtaining the calculation formula of the blood oxygen saturation value, a plurality of groups of calibration data need to be collected through experiments to fit the values of a2 and b2. Specifically, first, the blood hematocrit value and the blood oxygen saturation value are measured in advance by using a blood gas analyzer, and the corresponding first difference and second difference at another wavelength are determined, the least squares method is used to linearly fit the blood hematocrit value, the blood oxygen saturation value, and the corresponding first difference and second difference at another wavelength, and the second equation coefficient is determined.

[0073] In addition, whether I1 or I2, under the condition that the states and parameters of the blood remain unchanged, they are in an equal ratio relationship with I0. If I1 or I2 is used to fit and calculate the blood parameter index, I0 affected by the device temperature and consistency will directly affect the result accuracy of the parameter index. According to the above method, in the case of using two photodetectors to obtain I1 and I2, the states and parameters of the blood are related to the ratio of I1 and I2, and are irrelevant to I0. Therefore, the above method can effectively shield the influence of the initial incident light intensity.

[0074] Embodiment Two

[0075] In order to perform the method corresponding to the above-mentioned embodiment one, to realize the corresponding functions and technical effects, the following provides an ECMO-based red blood cell hematocrit and blood oxygen saturation detection device.

[0076] The embodiment discloses an ECMO-based red blood cell hematocrit and blood oxygen saturation detection device, as shown in the accompanying drawings, which specifically comprises: a first photodetector 1, a second photodetector 2, a light source 3, and a controller 5. Figure 2

[0077] Specifically, the light source 3 is used to emit light source signals of different wavelengths to the blood inside the flow cell 4, and the light source 3 inside includes but is not limited to LED or LD of 1300 nm, 950 nm, 940 nm, 880 nm, 850 nm, 810 nm, 805 nm, 650 nm, 660 nm, 760 nm, etc., which can be a combination of two or more multi-light sources. The two photodetectors can simultaneously cover the wavelength bands used by the light source. In addition, whether it is an LED or an LD, the light intensity has sensitive temperature characteristics, and even the devices on the circuit board also have a certain temperature influence. The aging of the light-emitting device will also cause the change of the incident light intensity, which will have a great influence on the data results in the use of a measurement device that depends on the stability of the incident light intensity.

[0078] ​Further, the first photodetector 1 and the second photodetector 2 can be on the same side or on the opposite side of the position of the light source 3, and the positional relationship of the three must be able to guarantee the formation of the optical path difference. Among them, the first photodetector 1, the light source 3 and the second photodetector 2 are arranged with a small device spacing, closely attached to the flow cell 4, and the distance between the first photodetector 1 and the second photodetector 2 and the light source 3 is kept similar but not equal, and the two distances are kept small difference, such as 3mm. In order to improve the measurement accuracy of the device, the first photodetector 1 and the second photodetector 2 can be provided with a single group or multiple groups.

[0079] Among them, the controller 5 is connected with the first photodetector 1, the second photodetector 2 and the light source 3 respectively, and is used to execute the ECMO-based hematocrit and blood oxygen saturation detection method corresponding to the first embodiment. The circuit board of the controller 5 is provided with a main control circuit, a light source control circuit, a photodetector signal amplification detection circuit, a communication control circuit and a power supply voltage stabilizing circuit.

[0080] In addition, the ECMO-based hematocrit and blood oxygen saturation detection device further comprises a communication unit 6. The communication unit 6 is connected with the controller 5, and is used to complete the information transmission between the controller 5 and the ECMO host, and upload the calculated hematocrit value and blood oxygen saturation value to the ECMO host. The connection mode of the communication unit 6 includes but is not limited to RS232, RS485 and CAN, etc.

[0081] Embodiment three

[0082] The embodiment discloses the practical application scene of an ECMO-based hematocrit and blood oxygen saturation detection method and device, and the specific operation process is as follows:

[0083] First, the device is powered through the power line in the cable, and can start working after power-on, and then the device is installed on the corresponding structure bayonet of the flow cell 4 of the ECMO blood circulation pipeline.

[0084] The controller 5 controls the light source 3 to emit light source signals of different wavelengths to the flow cell 4, and also acquires the electrical signals of the first photodetector 1 and the second photodetector 2 after amplification processing. An exposure time interval is set between the light sources to prevent mutual interference between the light sources. Taking the wavelengths of 660 nm and 950 nm as an example: first, only the 660 nm light source is lit, and the light intensity I660_1 generated by the first photodetector 1 and the light intensity I660_2 generated by the second photodetector 2 are acquired; then the 660 nm light source is turned off, and only the 950 nm light source is lit, and the light intensity I950_1 generated by the first photodetector 1 and the light intensity I950_2 generated by the second photodetector 2 are acquired. Because the two photodetectors have different light paths, the light intensity data of the first photodetector 1 and the second photodetector 2 will not be repeated.

[0085] The controller 5 controls the light source to be turned off, and acquires the ambient background light intensity I660_1b and I950_1b generated by the first photodetector 1, and the ambient background light intensity I660_2b and I950_2b generated by the second photodetector 2.

[0086] The difference between the two signal intensities can shield the influence of the background light, and acquire the light intensity component mainly affected by blood, denoted as I660_1d = I660_1 - I660_1b, I660_2d = I660_2 - I660_2b, I950_1d = I950_1 - I950_1b, and I950_2d = I950_2 - I950_2b.

[0087] The hematocrit value Hct and the logarithm of the ratio of I950_1d and I950_2d are approximately linearly related, where Hct = a1 x lg(I950_1d / I950_2d) + b1. Through experimental data collection and blood Hct index, the specific values of a1 and b1 can be calibrated and fitted, and during detection, only the obtained I950_1d and I950_2d are substituted into the above formula for calculation, thereby obtaining the hematocrit value.

[0088] Similarly, in the case of known blood Hct, the blood oxygen saturation value SO2 and the logarithm of the ratio of I660_1d and I660_2d are also approximately linearly related, where SO2 = (a2 x lg(I660_1d / I660_2d) + b2) x Hct. Through experimental data collection, blood oxygen and Hct index, the specific values of a2 and b2 can be fitted and calibrated, and during detection, only I660_1d, I660_2d and Hct are substituted into the above formula for calculation, thereby obtaining the blood oxygen saturation value. Finally, the controller 5 uploads the calculated hematocrit value and blood oxygen saturation value to the ECMO host through the communication unit 6.

[0089] In the third embodiment, only two kinds of light sources are exemplified, and the present application can be implemented for other two kinds of light sources or more kinds of light sources.

[0090] In addition, the present application is more suitable for the application scenario of ECMO, can realize the real-time noninvasive monitoring of the hematocrit value and the blood oxygen saturation value of the blood circulation pipeline, shields the error caused by the change of the initial incident light intensity due to the consistency, temperature drift and aging of the light emitting device, thereby realizing higher measurement accuracy of the index and field calibration, and bringing great convenience to the field application.

[0091] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between the various embodiments can be referred to each other.

[0092] The principles and implementation manners of the present application are described by applying specific examples herein, and the above description of the embodiments is only used to help understand the method of the present application and its core idea; meanwhile, for the general technical personnel in the field, the specific implementation manner and application range of the present application can be changed according to the idea of the present application. In conclusion, the content of the specification should not be understood as the limitation of the present application.

Claims

1. A method for detecting hematocrit and oxygen saturation based on ECMO, characterized in that, The ECMO at least comprises a flow cell, and the method comprises: under a first set condition, obtaining a first electrical signal and a second electrical signal; wherein the first set condition is a condition of controlling the light source to emit light source signals of different wavelengths to the blood inside the flow cell; the first electrical signal is a signal output by the first photodetector after the light source signal is reflected by the flow cell and collected; the second electrical signal is a signal output by the second photodetector after the light source signal is reflected by the flow cell and collected; under a second set condition, obtaining a third electrical signal and a fourth electrical signal; wherein the second set condition is a condition of controlling the light source to be turned off; the third electrical signal is a signal output by the first photodetector when there is no light source signal; the fourth electrical signal is a signal output by the second photodetector when there is no light source signal; calculating a first difference value and a second difference value; wherein the first difference value is a difference value between the first electrical signal and the third electrical signal; the second difference value is a difference value between the second electrical signal and the fourth electrical signal; according to the first difference value and the second difference value, calculating a hematocrit value and an oxygen saturation value respectively; the calculation formula of the hematocrit value is: Hct=a1×lg(A1 / B1)+b1; wherein Hct is the hematocrit value, a1 and b1 are first equation coefficients, A1 is a first difference value corresponding to a wavelength, and B1 is a second difference value corresponding to a wavelength; the calculation formula of the oxygen saturation value is: SO2=[a2×lg(A2 / B2)+b2]×Hct; wherein SO2 is the oxygen saturation value, a2 and b2 are second equation coefficients, A2 is a first difference value corresponding to another wavelength, and B2 is a second difference value corresponding to another wavelength.

2. The ECMO-based hematocrit and oxygen saturation detection method of claim 1, wherein, The determination method of the first equation coefficients is: using a blood gas analyzer to pre-measure a blood hematocrit value; determining the first difference value and the second difference value corresponding to a wavelength; using the least square method to linearly fit the blood hematocrit value, the first difference value and the second difference value corresponding to a wavelength, and determining the first equation coefficients.

3. The ECMO-based hematocrit and oxygen saturation detection method of claim 1, wherein, The determination method of the second equation coefficients is: using a blood gas analyzer to pre-measure a blood hematocrit value and a blood oxygen saturation value; determining the first difference value and the second difference value corresponding to another wavelength; using the least square method to linearly fit the blood hematocrit value, the blood oxygen saturation value, and the first difference value and the second difference value corresponding to another wavelength, and determining the second equation coefficients.

4. An ECMO-based hematocrit and blood oxygen saturation detection device, characterized by, It comprises: a light source, a first photodetector, a second photodetector, and a controller; the light source is used to emit light source signals of different wavelengths to the blood inside the flow cell; the first photodetector is used to output a first electrical signal and a third electrical signal; the second photodetector is used to output a second electrical signal and a fourth electrical signal; The controller is connected with the light source, the first photodetector and the second photodetector respectively, and is used for executing the ECMO-based hematocrit and blood oxygen saturation detection method in any one of claims 1-3.

5. The ECMO-based hematocrit and oxygen saturation detection device according to claim 4, characterized in that, Further comprising: A communication unit; The communication unit is connected with the controller, and is used for completing information transmission between the controller and an ECMO host.

6. The ECMO-based hematocrit and oxygen saturation detection device of claim 4, wherein, The first photodetector and the second photodetector are respectively arranged at different positions of the light source, and can form a light path difference.

7. The ECMO-based hematocrit and oxygen saturation detection device of claim 4, wherein, The number of the first photodetector and the second photodetector is single group or multiple groups.

8. The ECMO-based hematocrit and oxygen saturation detection device of claim 4, wherein, The distance from the first photodetector to the light source is not equal to the distance from the second photodetector to the light source.

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