Multi-cavity central venous catheter capable of intelligently measuring temperature and measuring method thereof

Abstract

The invention discloses an intelligent temperature measuring multi-cavity central venous catheter and a measuring method thereof.The intelligent temperature measuring multi-cavity central venous catheter comprises a catheter body and a displayer, a catheter main cavity, a temperature measuring cavity and an infusion cavity are formed in the catheter body, a first temperature sensor is arranged at the front end of the temperature measuring cavity, and a second temperature sensor is arranged at the tail end of the temperature measuring cavity; the first temperature sensor and the second temperature sensor are electrically connected with the display; by arranging the independent temperature measuring cavity, the temperatures of the two positions of the catheter can be accurately measured, the core temperature of the human body is inverted in combination with the flowing state of fluid and the heat conduction rule, the core temperature in the body of the patient is continuously and accurately monitored, and medical workers are helped to accurately judge the state of the patient.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, in particular to an intelligent temperature-measuring multi-lumen central venous catheter and a measurement method thereof. Background Art

[0002] Central venous catheters are widely used in clinical emergency, anesthesia, ICU and other departments. Through direct infusion into the central vein, patients can be quickly and effectively supplemented with blood, liquid medicine or nutrient solution. During the patient's treatment process, how to quickly and effectively monitor the patient's core body temperature is a major technical challenge. In the existing technology, a temperature sensor is embedded in the secondary cavity of a multi-lumen central venous catheter. However, in actual clinical operation, the initial temperature of the infused liquid to the patient through the central venous catheter is much lower than the normal body temperature of the human body (such as 4°C blood used in emergency), and the speed of infusion also varies according to the patient's needs. However, different liquid infusion temperatures, infusion speeds, and infusion methods will seriously affect the measurement accuracy of the temperature sensor in the secondary cavity of the central venous catheter for human blood temperature, making it impossible for the temperature sensor to accurately represent the core body temperature of the human body when the patient undergoes liquid infusion. This will cause medical staff to make inaccurate judgments on the patient's condition, resulting in accidents where rescue and treatment are not timely. Summary of the Invention

[0003] The purpose of the present invention is to provide a multi-lumen central venous catheter with intelligent temperature measurement and a measurement method thereof. By providing a separate temperature measurement cavity, the catheter can accurately measure the temperature in the main cavity and infusion cavity of the catheter, thereby realizing continuous and precise monitoring of the core temperature in the patient's body and helping medical staff to accurately judge the patient's condition.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a multi-lumen central venous catheter with intelligent temperature measurement, including a catheter body and a display, wherein the catheter body is provided with a catheter main lumen, a temperature measurement lumen and an infusion lumen, a first temperature sensor is provided at the front end of the temperature measurement lumen, and a second temperature sensor is provided at the end of the temperature measurement lumen, and both the first temperature sensor and the second temperature sensor are electrically connected to the display.

[0005] Optionally, a fixing boss matching the first temperature sensor and the second temperature sensor is provided on the inner wall of the temperature measurement cavity.

[0006] Optionally, three fixing bosses are provided corresponding to each temperature sensor, the three fixing bosses are arranged in a Y shape, and the first temperature sensor and the second temperature sensor are provided at the center of the fixing bosses.

[0007] A method for measuring a multi-lumen central venous catheter for intelligent temperature measurement comprises the following steps:

[0008] 1) Calculation of heat flux

[0009] When there is no fluid infusion in the central venous catheter, the temperature measured by the two sensors is the same, which is the human core body temperature T0;

[0010] When a drug solution is infused inside the main lumen of a central venous catheter, the temperature T of the drug solution is lower than the core temperature of the human body. At this time, the temperatures measured by the sensors are different. The temperature measured by the first temperature sensor is T1, and the temperature measured by the second temperature sensor is T2. Heat is transferred from the blood to the first temperature sensor and the second temperature sensor through two processes: heat conduction and heat convection, which occur inside the catheter wall and outside the flow channel, respectively.

[0011] For the heat conduction process within the wall, heat is conducted from the wall to the first and second temperature sensors, and then from the first and second temperature sensors to the liquid medicine. The wall thicknesses between the temperature sensors and the outer wall of the catheter body and the inner wall of the main lumen are equal, so the heat flux density at the two locations can be expressed as:

[0012]

[0013] Where q1 is the heat flux density at the first temperature sensor during heat conduction, q2 is the heat flux density at the second temperature sensor during heat conduction, λ is the thermal conductivity, T w1 is the wall temperature at the first temperature sensor location, T w2 is the wall temperature at the position of the second temperature sensor, t1 is the inner wall temperature at the position of the first temperature sensor, t2 is the inner wall temperature at the position of the second temperature sensor, and δ is the wall thickness of the central venous catheter for heat exchange;

[0014] The process of heat transfer from blood to the wall is thermal convection, forming a very thin temperature boundary layer outside the wall. During the thermal convection stage, the heat flux density at the wall can be expressed as:

[0015] q1'=h×(T0-T w1 ) (3)

[0016] q2'=h×(T0-T w2 ) (4)

[0017] Wherein, q1' is the heat flux density at the first temperature sensor position during heat convection, q2' is the heat flux density at the second temperature sensor position during heat convection, T0 is the human body core temperature, and h is the convection heat transfer coefficient;

[0018] The wall temperature at the same position in the two processes of heat conduction and heat convection is the same, that is:

[0019] q1=q1' (5)

[0020] q2=q2' (6)

[0021] 2) Calculation of human core temperature

[0022] Take a microelement with a length of Δx in the main lumen of the catheter as the research object. This microelement flows from the second temperature sensor position to the first temperature sensor position. The amount of heat the microelement temperature rises is equal to the heat received by the periphery of the main lumen of the microelement area. The relationship can be expressed as:

[0023] C×Δm×ΔT=q×S×τ (7

[0024] Where c is the specific heat capacity, Δm is the mass of the microelement, ΔT is the temperature difference between the second temperature sensor and the first temperature sensor; q is the heat flux density outside the main cavity of the microelement region. The microelement flows from the second temperature sensor to the first temperature sensor. The magnitude of q is expressed by the average of the heat flux densities q1 and q2 at the two sensor positions. S is the surface area outside the main cavity of the microelement region. τ is the flow time of the microelement from the second temperature sensor to the first temperature sensor.

[0025] According to formulas (1)(2)(7), we can get:

[0026]

[0027] Where ρ is the density of the input liquid, R0 is the radius of the main lumen of the catheter, L is the distance between the first temperature sensor and the second temperature sensor, and v is the flow rate of the liquid;

[0028] During the heat conduction process, the temperatures T1 and T2 measured by the sensor are regarded as the average of the wall temperature and the inner wall temperature on the liquid side, then:

[0029]

[0030] According to formulas (5)(6)(10)(11)(12), the theoretical calculation formula for human core temperature T0 can be obtained:

[0031]

[0032] By integrating the constants in formula (11), the expression of human core temperature is obtained as follows:

[0033]

[0034] K ρ The temperature coefficient is related to the density of the infused liquid and the type of main or side cavity selected;

[0035] 3) Temperature coefficient K ρ Calibration

[0036] Under different materials, specifications and infusion methods, K ρ The values ​​are different and need to be calibrated before the product is shipped. The calibration method is as follows:

[0037] Place the central venous catheter in a constant temperature box. The liquid in the constant temperature box is simulated blood, and the temperature of the simulated blood is T 01 , the value of which is set to 37.5℃, the drug solution is input into the main lumen of the central venous catheter at a constant flow rate ν1, the temperature of the two temperature sensors in the central venous catheter is measured, and the measured temperatures T1 and T2 are obtained;

[0038] Substituting the measured data into formula (12) can calibrate the temperature coefficient K for the infusion of the central venous catheter main cavity. ρ1 .

[0039] According to the same calibration method, the temperature coefficient K of the infusion cavity during infusion can also be obtained. ρ2 , Temperature coefficient K when the main cavity and the infusion cavity are infused at the same time ρ3 .

[0040] The intelligent temperature measurement multi-lumen central venous catheter and its measurement method of the present invention have the following advantages:

[0041] (1) The catheter body of the central venous catheter has a three-cavity structure. Two temperature sensors are set at the front and end of the temperature measurement cavity. By calculating the temperatures measured by the two temperature sensors, the core temperature of the patient's body can be continuously and in real time displayed on the display. The measurement results are accurate and reliable.

[0042] (2) The data measurement, processing, and display functions are integrated into one device, which does not rely on clinical monitors and other equipment. Patients can carry it with them and monitor the core temperature of the human body around the clock. It is small in size and portable.

[0043] (3) The temperature coefficient K can be obtained by calibration method ρ During clinical operation, there is no need to input each parameter one by one. It is only necessary to confirm the flow rate, the type of medium for the input liquid, and the selection of the infusion cavity. The interface is simple and clear, and the operation is convenient. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a structural schematic diagram of the present invention.

[0045] Figure 2 It is a schematic diagram of the cross-sectional structure of the catheter body.

[0046] Figure 3 It is a schematic diagram of the cross-sectional structure of the temperature measurement cavity.

[0047] Figure 4This is a schematic diagram of the selection of the infinitesimal element Δx. DETAILED DESCRIPTION

[0048] The present invention is further described below with reference to the accompanying drawings. In the description of the present invention, terms such as "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, they should not be understood as limiting the present invention.

[0049] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features.

[0050] like Figures 1-4 As shown, a multi-lumen central venous catheter with intelligent temperature measurement includes a catheter body 2 and a display 4. The catheter body 2 is inserted into the central vein 1, and the outside of the catheter body 2 is filled with blood 11. The catheter body 2 is provided with a catheter main cavity 211, a temperature measurement cavity 212 and an infusion cavity 213. The front end of the temperature measurement cavity 212 is provided with a first temperature sensor 31, and the front end refers to the end close to the inside of the human body. The end of the temperature measurement cavity 212 is provided with a second temperature sensor 32, and the end refers to the end close to the outside of the human body. The first temperature sensor 31 and the second temperature sensor 32 are both electrically connected to the display 4.

[0051] The display 4 is equipped with three submodules: liquid flow rate and medium parameter input, data acquisition and post-processing, and temperature display. The liquid flow rate and medium parameter input submodule has an external input function, which can be used to select whether liquid infusion is required. When liquid infusion is required, the flow rate of the infused liquid needs to be input, and the type of medium (usually ordinary liquid medicine or blood) needs to be input. Figure 4 The direction of the arrow in the middle is the flow direction of the liquid medicine or blood), and the main lumen 211 or the infusion lumen 213 of the catheter is used for liquid medicine infusion;

[0052] The data acquisition and post-processing submodule is connected to the first temperature sensor 31 and the second temperature sensor 32 through wires to continuously collect data. After obtaining the external input of the type of medium and chamber type of this infusion, the corresponding calibrated temperature coefficient K is called. ρ When this module performs post-processing, it will perform logical operations based on the core temperature calculation formula embedded in the product before leaving the factory. After obtaining the human body core temperature T0, it will be sent to the temperature display submodule for real-time display.

[0053] The temperature display submodule accurately, in real time and continuously displays and records the current core temperature T0 of the human body.

[0054] Furthermore, a fixed boss 2121 matching the first temperature sensor 31 and the second temperature sensor 32 is provided on the inner wall of the temperature measuring cavity 212. The cross-sectional shapes of the first temperature sensor 31 and the second temperature sensor 32 are both circular structures. A thin layer of fixing glue is evenly coated on the outer column surface of the temperature sensor, and the temperature sensor is fixedly connected to the fixed boss 2121 by gluing.

[0055] Furthermore, three fixed bosses 2121 are provided corresponding to each temperature sensor, and the end of the fixed boss 2121 is a semi-elliptical structure. The extension line of the long axis of the fixed boss 2121 points to the axis center of the temperature measuring cavity 212. The three fixed bosses 2121 are distributed in a Y-shaped axisymmetric manner. The vertex 311 of the fixed boss 2121 contacts the outer side of the temperature sensor. The outer diameter of the first temperature sensor 31 and the second temperature sensor 32 is slightly larger than the diameter of the circle formed by the three fixed bosses 2121, forming an interference fit, thereby improving the stability of the temperature sensor.

[0056] A method for measuring a multi-lumen central venous catheter for intelligent temperature measurement comprises the following steps:

[0057] 1) Calculation of heat flux

[0058] When there is no fluid infusion in the central venous catheter, the temperature measured by the two sensors is the same, which is the human core body temperature T0;

[0059] When a drug solution is infused into the central venous catheter main lumen 211, the drug solution temperature T is lower than the human body's core temperature. At this time, the temperatures measured by the sensors are different. The temperature measured by the first temperature sensor 31 is T1, and the temperature measured by the second temperature sensor 32 is T2. Heat is transferred from the blood to the first temperature sensor 31 and the second temperature sensor 32 through two processes: heat conduction and heat convection, which occur inside the catheter wall and outside the catheter, respectively.

[0060] Regarding the heat conduction process within the wall, heat is conducted from the wall to the first temperature sensor 31 and the second temperature sensor 32, and then conducted from the first temperature sensor 31 and the second temperature sensor 32 to the liquid medicine portion. The wall thicknesses between the temperature sensors and the outer wall of the catheter body 2 and the inner wall of the main cavity are designed to be equal, so the heat flux density at the two locations can be expressed as:

[0061]

[0062] Where q1 is the heat flux density at the position of the first temperature sensor 31 during heat conduction, q2 is the heat flux density at the position of the second temperature sensor 32 during heat conduction, λ is the thermal conductivity, R0 is the radius of the catheter main cavity 211, T w1 is the wall temperature at the location of the first temperature sensor 31, T w2 is the wall temperature at the position of the second temperature sensor 32, t1 is the inner wall temperature at the position of the first temperature sensor 31, t2 is the inner wall temperature at the position of the second temperature sensor 32, and δ is the wall thickness of the central venous catheter for heat exchange;

[0063] The process of heat transfer from blood to the wall is thermal convection, forming a very thin temperature boundary layer outside the wall. During the thermal convection stage, the heat flux density at the wall can be expressed as:

[0064] q1'=h×(T0-T w1 ) (3)

[0065] q2'=h×(T0-T w2 ) (4)

[0066] Wherein, q1' is the heat flux density at the position of the first temperature sensor 31 during heat convection, q2' is the heat flux density at the position of the second temperature sensor 32 during heat convection, T0 is the core temperature of the human body, and h is the convection heat transfer coefficient;

[0067] The wall temperature at the same position in the two processes of heat conduction and heat convection is the same, that is:

[0068] q1=q1' (5)

[0069] q2=q2' (6)

[0070] 2) Calculation of human core temperature

[0071] Take the microelement 5 with a length of Δx in the main lumen 211 of the catheter as the research object. This microelement 5 flows from the position of the second temperature sensor 32 to the position of the first temperature sensor 31. The amount of heat that the temperature of the microelement 5 increases is equal to the heat received by the periphery of the main lumen in the microelement 5 area. The relationship can be expressed as:

[0072] c×Δm×ΔT=q×S×τ (7)

[0073] Wherein, c is the specific heat capacity, Δm is the mass of the infinitesimal element 5, ΔT is the temperature difference between the second temperature sensor 32 and the first temperature sensor 31; q is the heat flux density at the periphery of the main cavity in the region of the infinitesimal element 5, and the heat flux density of the infinitesimal element 5 flowing from the second temperature sensor 32 to the first temperature sensor 31 is represented by the average of the heat flux densities q1 and q2 at the two sensor positions; S is the surface area of ​​the periphery of the main cavity in the region of the infinitesimal element 5, and τ is the flow time of the infinitesimal element 5 flowing from the second temperature sensor 32 to the first temperature sensor 31;

[0074] According to formulas (1)(2)(7), we can get:

[0075]

[0076] Where ρ is the density of the input liquid, L is the distance between the first temperature sensor 31 and the second temperature sensor 32, and v is the liquid flow rate;

[0077] During the heat conduction process, the temperatures T1 and T2 measured by the sensor are regarded as the average of the wall temperature and the inner wall temperature on the liquid side, then:

[0078]

[0079] According to formulas (5)(6)(10)(11)(12), the theoretical calculation formula for human core temperature T0 can be obtained:

[0080]

[0081] By integrating the constants in formula (11), the expression of human core temperature is obtained as follows:

[0082]

[0083] K ρ The temperature coefficient is related to the density of the infused liquid and the type of main or side cavity selected;

[0084] 3) Temperature coefficient K ρ Calibration

[0085] Under different materials, specifications and infusion methods, K ρ The values ​​are different and need to be calibrated before the product is shipped. The calibration method is as follows:

[0086] Place the central venous catheter in a constant temperature box. The liquid in the constant temperature box is simulated blood, and the temperature of the simulated blood is T 01 , which is set to 37.5°C, the drug solution is input into the main lumen 211 of the central venous catheter at a constant flow rate ν1, and the temperature of the two temperature sensors in the central venous catheter is measured to obtain the measured temperatures T1 and T2;

[0087] Substituting the measured data into formula (12), the temperature coefficient K applicable to the infusion of the central venous catheter and the main lumen 211 of the catheter can be calibrated. ρ1 .

[0088] According to the same calibration method, the temperature coefficient K of the infusion cavity 213 during infusion can also be obtained. ρ2 , the temperature coefficient K when the main cavity and the infusion cavity 213 are infused at the same time ρ3 .

[0089] Temperature coefficient K ρ After the calibration is completed, it will not change. Enter the flow rate of the infusion liquid, the type of medium, and the type of chamber selected on the display 4, and the display 4 can automatically call the corresponding temperature coefficient K ρ , and performs logical operations based on the formula (12) embedded in the display before the product leaves the factory to obtain the current core temperature T0 of the human body and display it in real time on the display 4. The interface is simple and clear and the operation is convenient.

[0090] The embodiments described above are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

Claims

1. A multi-lumen central venous catheter with intelligent temperature measurement, characterized by: The device comprises a catheter body and a display. The catheter body is provided with a catheter main cavity, a temperature measurement cavity and an infusion cavity. The front end of the temperature measurement cavity is provided with a first temperature sensor, and the end of the temperature measurement cavity is provided with a second temperature sensor. Both the first temperature sensor and the second temperature sensor are electrically connected to the display.

2. The multi-lumen central venous catheter with intelligent temperature measurement according to claim 1, characterized in that: A fixing boss matching the first temperature sensor and the second temperature sensor is arranged on the inner wall of the temperature measuring cavity.

3. The multi-lumen central venous catheter with intelligent temperature measurement according to claim 2, characterized in that: There are three fixed bosses corresponding to each temperature sensor, and the three fixed bosses are arranged in a Y shape. The first temperature sensor and the second temperature sensor are arranged at the center of the fixed bosses.

4. The method for measuring a multi-lumen central venous catheter for intelligent temperature measurement according to claims 1-3, characterized in that: The following steps are involved: 1) Calculation of heat flux When there is no fluid infusion in the central venous catheter, the temperature measured by the two sensors is the same, which is the human core body temperature T0; When a drug solution is infused inside the main lumen of a central venous catheter, the temperature T of the drug solution is lower than the core temperature of the human body. At this time, the temperatures measured by the sensors are different. The temperature measured by the first temperature sensor is T1, and the temperature measured by the second temperature sensor is T2. Heat is transferred from the blood to the first temperature sensor and the second temperature sensor through two processes: heat conduction and heat convection, which occur inside the catheter wall and outside the flow channel, respectively. For the heat conduction process within the wall, heat is conducted from the wall to the first and second temperature sensors, and then from the first and second temperature sensors to the liquid medicine. The wall thicknesses between the temperature sensors and the outer wall of the catheter body and the inner wall of the main lumen are equal, so the heat flux density at the two locations can be expressed as: Where q1 is the heat flux density at the first temperature sensor during heat conduction, q2 is the heat flux density at the second temperature sensor during heat conduction, λ is the thermal conductivity, T w1 is the wall temperature at the first temperature sensor location, T w2 is the wall temperature at the position of the second temperature sensor, t1 is the inner wall temperature at the position of the first temperature sensor, t2 is the inner wall temperature at the position of the second temperature sensor, and δ is the wall thickness of the central venous catheter for heat exchange; The process of heat transfer from blood to the wall is thermal convection, forming a very thin temperature boundary layer outside the wall. During the thermal convection stage, the heat flux density at the wall can be expressed as: q1'=h×(T0-T w1 ) (3) q2'=h×(T0-T w2 ) (4) Wherein, q1' is the heat flux density at the first temperature sensor position during heat convection, q2' is the heat flux density at the second temperature sensor position during heat convection, T0 is the human body core temperature, and h is the convection heat transfer coefficient; The wall temperature at the same position in the two processes of heat conduction and heat convection is the same, that is: q1=q1' (5) q2=q2' (6) 2) Calculation of human core temperature Take a microelement with a length of △x in the main lumen of the catheter as the research object. This microelement flows from the position of the second temperature sensor to the position of the first temperature sensor. The amount of heat the microelement temperature rises is equal to the heat received by the periphery of the main lumen of the microelement area. The relationship can be expressed as: c×Δm×ΔT=q×S×τ (7) Where c is the specific heat capacity, △m is the mass of the microelement, △T is the temperature difference between the second temperature sensor and the first temperature sensor; q is the heat flux density outside the main cavity of the microelement region, and the microelement flows from the second temperature sensor to the first temperature sensor. The magnitude of q is expressed by the average of the heat flux densities q1 and q2 at the two sensor positions. S is the surface area outside the main cavity of the microelement region, and τ is the flow time of the microelement from the second temperature sensor to the first temperature sensor. According to formulas (1)(2)(7), we can get: Where ρ is the density of the input liquid, R0 is the radius of the main lumen of the catheter, L is the distance between the first temperature sensor and the second temperature sensor, and v is the flow rate of the liquid; During the heat conduction process, the temperatures T1 and T2 measured by the sensor are regarded as the average of the wall temperature and the inner wall temperature on the liquid side, then: According to formulas (5)(6)(10)(11)(12), the theoretical calculation formula for human core temperature T0 can be obtained: By integrating the constants in formula (11), the expression of human core temperature is obtained as follows: K ρ The temperature coefficient is related to the density of the infused liquid and the type of main or side cavity selected; 3) Temperature coefficient K ρ Calibration Under different materials, specifications and infusion methods, K ρ The values ​​are different, so the product needs to be calibrated before leaving the factory. The calibration method is as follows: Place the central venous catheter in a constant temperature box. The liquid in the constant temperature box is simulated blood, and the temperature of the simulated blood is T 01 , the value of which is set to 37.5℃, the drug solution is input into the main lumen of the central venous catheter at a constant flow rate ν1, the temperature of the two temperature sensors in the central venous catheter is measured, and the measured temperatures T1 and T2 are obtained; Substituting the measured data into formula (12) can calibrate the temperature coefficient K for the infusion of the central venous catheter main cavity. ρ1 . According to the same calibration method, the temperature coefficient K of the infusion cavity during infusion can also be obtained. ρ2 , Temperature coefficient K when the main cavity and the infusion cavity are infused at the same time ρ3 .

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