A method for heating medical liquid

Abstract

The present invention discloses a method for heating medical liquids, which measures the liquid flow rate by heating and measuring the temperature of the speed measuring section, and calculates the energy required for heating to the target temperature, and then controls the second heater to preheat the liquid flowing through the heating section, and finally controls the second heater in real time to perform temperature compensation by measuring the difference between the actual liquid outlet temperature and the target temperature. The present invention measures the flow rate, is separated from the active flow control device of the peristaltic pump, does not need to worry about the destruction of red blood cells, can be adapted to gravity or pressurized chamber infusion, and the control is directly related to the liquid outlet temperature, can achieve temperature compensation, and makes the temperature control precise.

Description

Technical Field

[0001] The invention belongs to the field of infusion heating technology, and in particular relates to a method for heating a medical liquid. Background Art

[0002] Intraoperative hypothermia is one of the common complications during anesthesia and surgery, especially for patients who need to infuse a large amount of frozen stored blood, cryogenic fluids, and a large amount of body cavity flushing during long-term surgery, major surgery, surgery on the elderly and children. When the body temperature is <36°C during surgery, it is called intraoperative hypothermia. It is reported that the incidence of intraoperative hypothermia can reach 50% to 70%. Although hypothermia can reduce the body's metabolic rate, reduce oxygen consumption, and increase the tolerance of tissues and organs to ischemia and hypoxia. However, it still leads to a variety of complications, such as postoperative chills, increased incision infection rate and cardiovascular complications, abnormal coagulation function, delayed anesthesia awakening, etc., which have an adverse effect on the patient's surgical safety. Therefore, maintaining the patient's normal intraoperative body temperature through infusion and warming is one of the important measures to ensure the success of anesthesia surgery and reduce postoperative complications.

[0003] At present, the domestic market is mainly based on constant temperature box heating and medical electronic equipment to heat transfer heating of infusion lines. In these systems, the internal heating of the equipment is mainly achieved in the following ways:

[0004] 1. Water bath heat transfer: There is a dedicated water bath component on the consumables, which is cylindrical, hollow in the middle, and the infusion pipeline is spirally wound. The equipment has a built-in water bath heating device. When the consumables are installed, circulating hot water passes through the hollow pipe to transfer heat to the infusion pipeline for heating. The pressurized chamber squeezes the liquid bag and adjusts the flow rate through the flow regulator.

[0005] 2. Dry heat transfer: There are dedicated heat-receiving parts on the consumables, and a constant temperature heating plate on the equipment. The heat-receiving parts are installed in the equipment. The system periodically monitors the temperature of the heating plate and controls the power of the heating plate to achieve constant temperature of the heating plate and transfer heat to the infusion line. The pressurized chamber squeezes the liquid bag and adjusts the flow rate through the flow regulator.

[0006] 3. Electromagnetic heating: Electromagnetic heating requires that the consumables that come into contact with blood or liquid contain metal. Through electromagnetic induction, the metal heats up the liquid, and the heating efficiency is high. The equipment needs to cooperate with the peristaltic pump to actively control the flow rate, and the heating power is adjusted by monitoring the inlet and outlet temperatures to achieve heating.

[0007] The above three methods all have their own shortcomings:

[0008] For water bath heat transfer, it uses water bath heating, which is easy to breed bacteria and increases the maintenance work of water bath circulating water; the heating temperature is not adjustable, the outlet liquid temperature varies with the flow rate, and the temperature control is not accurate; the circulating water needs to be preheated, which takes a long time.

[0009] For dry heat transfer, the heating temperature cannot be adjusted, the outlet liquid temperature varies with the flow rate, and the temperature control is not precise; the heating area of ​​the consumables is limited and cannot support large flow rates.

[0010] For electromagnetic heating, it uses a peristaltic pump to apply pressure, which can easily lead to the destruction of some red blood cells; metal precipitation enters the blood and may cause allergic reactions; the heating components have a complex structure and high production process requirements, resulting in high costs. Summary of the invention

[0011] The technical problem to be solved by the present invention is to provide a method and device for heating medical liquid, which can accurately control the outlet temperature of the liquid according to needs.

[0012] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0013] A method for heating a medical liquid comprises the following steps:

[0014] A. a liquid heating flow path is provided, which includes a velocity measuring section and a heating section in sequence, and a first heater is used to heat the liquid in the velocity measuring section entering the liquid heating flow path;

[0015] B. Use the first temperature sensor to measure the temperature of the liquid before it enters the speed measuring section, use the second temperature sensor to measure the temperature of the heated liquid entering the speed measuring section, and calculate the reference flow rate of the liquid based on the temperature rise difference of the liquid measured by the two sensors;

[0016] C. calculating the energy required for heating to the target temperature according to the reference flow rate, and using the energy to control the initial heating power of the second heater to preheat the liquid flowing through the heating section;

[0017] D. Use the third temperature sensor to measure the temperature of the liquid at the end of the heating section in real time, and use the difference between the measured liquid outlet temperature and the target temperature to provide real-time feedback to adjust the heating power of the second heater.

[0018] In step A, the speed measuring section is intermittently heated by the first heater, and the temperature is measured by the second temperature measuring sensor to detect whether liquid flows in.

[0019] In step B, the reference flow rate is obtained by:

[0020] The average specific heat capacity of the heated liquid is selected as the reference value, and through simulation experiments, the comparative relationship between the flow rate and the liquid temperature rise difference is obtained, and then the reference flow rate corresponding to the reference value is obtained.

[0021] The calculation formula of the reference flow rate is:

[0022] V1=(K2*P+K3*B*ΔT) / (K3*ΔT+K1*K2*P)

[0023] V1: reference flow rate;

[0024] P: power of the first heater;

[0025] ΔT: liquid temperature rise;

[0026] K1, K2, K3, B: are constants obtained by experimental test calculations.

[0027] In step C, the calculation formula of the initial heating power is:

[0028] Pwm1=C*V1 / ΔT

[0029] C: experimental calibration parameters;

[0030] V1: reference flow rate;

[0031] ΔT: liquid temperature rise;

[0032] Pwm1: initial heating power.

[0033] In step D, the heating power calculation formula is:

[0034] Pwm2=Kp*e(k)+Ki*∑e(k)+Kd[e(k)-e(k-1)]+Kb

[0035] Kp, Ki, Kd, ​​Kb: constants measured experimentally, corresponding PID adjustment parameters are set through experiments according to different reference flow rates;

[0036] e(k): the difference between the current liquid outlet temperature and the target temperature, k is 1, 2, ..., k;

[0037] e(k-1): the difference between the last outlet temperature and the target temperature;

[0038] ∑e(k): the cumulative sum of e(k) and previous differences;

[0039] Pwm2: heating power.

[0040] In step D, a fourth temperature measuring sensor disposed near the third temperature measuring sensor is also used to perform redundant temperature measurement.

[0041] The liquid heating flow path adopts a serpentine channel structure, with one side being a transparent surface and the other side being a light-shielding surface.

[0042] The first heater adopts an infrared halogen tungsten lamp tube, which is arranged outside the transparent surface of the liquid heating flow path, and has a length corresponding to the speed measuring section, and is covered with the speed measuring section by a metal light-shielding cover with a reflective coating on the inner wall.

[0043] There are several second heaters, all of which are independently controllable infrared halogen tungsten lamps and are evenly arranged outside the transparent surface of the serpentine channel.

[0044] The medical liquid heating method and device of the present invention have the following advantages:

[0045] 1. Through flow rate measurement, the peristaltic pump active flow control device is separated, and there is no need to worry about red blood cell damage. It can be adapted to gravity or pressurized chamber infusion;

[0046] 2. It uses infrared heating, no medium is required, and the high-quality infrared halogen tungsten lamp has a long life and is almost maintenance-free during the life cycle of the equipment;

[0047] 3. The control is directly related to the outlet temperature, which can achieve temperature compensation and make the temperature control accurate;

[0048] 4. It can automatically detect the inflow of liquid and then turn on the heating to prevent dry burning;

[0049] 5. Use two temperature sensors to perform redundant temperature measurement on the outlet liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The invention is described in detail below with reference to the accompanying drawings and specific embodiments:

[0051] Figure 1 is a flowchart of the medical liquid heating method of the present invention;

[0052] Figure 2 It is a structural schematic diagram of a heating device in one embodiment of the heating method of the present invention;

[0053] Figure 3 yes Figure 2 A schematic diagram of the back side of the heating device;

[0054] Figure 4 is an exploded schematic diagram of an embodiment of the present invention applied to a heating device;

[0055] Figure 5 It is a three-dimensional schematic diagram of the positioning mechanism of the heating consumable material of the present invention;

[0056] Figure 6-Figure 8 The schematic diagrams are respectively the structural diagrams of the heating consumables of the present invention before, during and after being loaded into the box. DETAILED DESCRIPTION

[0057] The medical liquid heating method of the present invention is as follows Figure 1 As shown, the following steps are included:

[0058] A. A liquid heating flow path (for heating consumables) is provided, which includes a velocity measuring section and a heating section in sequence, and a first heater is used to heat the liquid in the velocity measuring section entering the liquid heating flow path; as an embodiment, the liquid heating flow path can specifically adopt the following method: Figure 2 As shown, one side is a shell 1, and the other side is a transparent film sealed on the shell 1, and a serpentine channel 2 is formed in the internal cavity of the shell 1. The inner wall of the shell 1 adopts a black light-shielding surface, and the speed measuring section 5 is located at the front end of the bottom of the serpentine channel 2, and its length is shorter than that of a single serpentine channel. The first heater 3 can adopt an infrared halogen tungsten lamp tube, which is arranged on the outside of the transparent surface of the liquid heating flow path, and its heating length corresponds to the speed measuring section 5, and is covered with a metal light-shielding cover 4 with a reflective coating on the inner wall to reduce energy leakage and improve efficiency.

[0059] B. Using the first temperature sensor 6 (see Figure 3 ) The temperature of the liquid before entering the speed measuring section 5 is measured, and the temperature of the heated liquid entering the speed measuring section 5 is measured by the second temperature measuring sensor 7, and the reference flow rate of the liquid is calculated by the difference in the temperature rise of the liquid measured by the two. The principle is as follows: When the equipment is used, due to different use occasions, the liquid flow rate is different and unknown. When the liquid flows into the liquid heating flow path, the first temperature measuring sensor 6 first measures the inlet temperature as t1. After being heated by the first heater 3, this small section of liquid is heated, and the second heater 10 measures the temperature of the heated liquid as t2. Since the whole is covered with a metal light-shielding cover, it is less affected by the external environment temperature. Therefore, under a certain period of time, the heat energy obtained by the liquid passing through this section of the cavity is almost the same, so the liquid flow rate can be calibrated by Δt1=t2-t1. Usually, the heated liquid is mainly blood or liquid medicine, and its specific heat capacity is about 3800-4200J / (kg·K). Therefore, the reference value can be taken as 4000J / (kg·K). By configuring this type of liquid in a laboratory environment and conducting simulation tests, the relationship between flow rate and Δt1 can be obtained. In this way, a reference flow rate v1 can be obtained before the liquid is formally heated. The calculation formula for the reference flow rate can be specifically adopted:

[0060] V1=(K2*P+K3*B*ΔT) / (K3*ΔT+K1*K2*P)

[0061] V1: reference flow rate;

[0062] P: power of the first heater;

[0063] ΔT: liquid temperature rise;

[0064] K1, K2, K3, B: are all constants obtained by experimental test calculation, among which K2 is the experimental calibration coefficient of the reference value of the associated specific heat capacity.

[0065] C. Calculate the energy required to heat to the target temperature based on the reference flow rate, and use this to control the initial heating power of the second heater 10 to preheat the liquid flowing through the heating section. Figure 2 As shown, the second heater 10 also adopts an infrared halogen tungsten lamp, and according to the number and length of the serpentine channel after the speed measuring section 5, the corresponding number and length of the second heater 10 (the length is greater than the first heater 3) are selected, and are evenly arranged outside the transparent surface of the serpentine channel, and can be independently controlled. Figure 2 There are four second heaters 10 shown in the figure. Since the pipes of the liquid heating flow path are all the same, when the reference flow rate is obtained in advance, the energy required for heating to the target temperature can be calculated based on the cavity volume, the liquid inlet temperature and the reference flow rate. The specific formula that can be used is:

[0066] Pwm1=C*V1 / ΔT

[0067] C: experimental calibration parameters;

[0068] V1: reference flow rate;

[0069] ΔT: liquid temperature rise;

[0070] Pwm1: initial heating power.

[0071] In addition, the heating power is controlled by several independent lamp tubes. Since each lamp tube also supports individual power adjustment, energy control can be made more precise.

[0072] D. Use the third temperature sensor 8 to measure the temperature of the liquid at the end of the heating section in real time, and use the difference between the measured liquid outlet temperature and the target temperature to adjust the heating power (temperature compensation) of the second heater 10 in real time. After running step C, a temperature close to the target temperature can be output, but due to the different specific heat capacities of the heated liquids, the liquid outlet temperatures after heating are also different. For liquids with low specific heat capacities, the actual temperature will exceed the target value, while for liquids with high specific heat capacities, the actual temperature will be lower than the target value. Therefore, in order to make the liquid outlet temperature consistent with the target value, temperature compensation needs to be introduced. The third and fourth temperature sensors 8 and 9 can be used to measure the liquid outlet temperature, wherein the liquid outlet temperature is mainly measured by the third temperature sensor 8, and the fourth temperature sensor 9 is a redundant temperature measurement to enhance the reliability of the device. If the temperature difference between the two is too large, it means that the device is faulty. After the initial heating in step C, the actual temperature measured by the third temperature sensor 8 is t3, which is compared with the target temperature t4 to obtain e=t4-t3. After multiple measurements, an array e(k) is generated. The heating power is adjusted according to the historical e(k) calculation to make the value of e as close to 0 as possible, that is, the liquid outlet temperature tends to the set target temperature, so as to achieve the purpose of accurate heating. The specific formula that can be used is:

[0073] Pwm2=Kp*e(k)+Ki*∑e(k)+Kd[e(k)-e(k-1)]+Kb

[0074] Kp, Ki, Kd, ​​Kb: constants measured experimentally, corresponding PID adjustment parameters are set through experiments according to different reference flow rates;

[0075] e(k): the difference between the measured liquid temperature and the target temperature, k is 1, 2, ..., k;

[0076] e(k-1): the difference between the last measured liquid temperature and the target temperature;

[0077] ∑e(k): the cumulative sum of e(k) and previous differences;

[0078] Pwm2: heating power.

[0079] For the energy required for heating, if it is small, you can choose one or several of them for heating. If you choose four to heat together, generally four are used for heating with the same power.

[0080] In addition, in step A, the speed measuring section 5 can be intermittently heated by the first heater 3, and the temperature measured by the second temperature sensor 7 is used to detect whether liquid flows in. Once heated, the temperature measured without liquid flowing in is much higher than the temperature with liquid flowing in, so a corresponding threshold can be set, and once the measured temperature is lower than the threshold, the entire heating method is automatically started.

[0081] The four temperature sensors 6-9 can all be digital infrared thermopile sensors. Figure 2 11 is a metal sensing sheet of each sensor, and the temperature is measured by the sensor from the corresponding opening of the shell through the heat conduction of the liquid.

[0082] Please combine Figure 4-Figure 5 As shown, the medical liquid heating method of the present invention can be applied to the following heating device, including a box 111 and a heating consumable 112 (that is, the above-mentioned liquid heating flow path), and the front side of the box 111 is provided with an insertion port ( Figure 1The box 111 is provided with a positioning assembly, including a movable lever 114, a movable pressing piece 115 and an elastic clamp 116 arranged at the rear side of the consumable cavity, the movable lever 114 is provided with a button 117 at the front end, the button 117 is arranged at the front end of the box 111, the movable lever 114 is provided with a winding shaft 41 installed on the box 111 in the middle, and the rear end is a prying head 42, the movable pressing piece 115 is provided with a first step 51 at the front end and overlapped on the prying head 42 through the first step 51, and a circular arc guide surface 52 is provided below the first step 51, and the circular arc guide surface 52 extends backward and has an upward second step 53, the rear end of the movable pressing plate 115 is arranged on the box body 111 through a rotating shaft with a torsion spring 54; the heating consumable 112 can be designed to have a serpentine liquid heating flow channel inside. When the liquid is passed in, it is heated by an infrared heating lamp tube 118 (119 is a circuit board) arranged in the box body 111 and located outside the consumable. The top rear end of the heating consumable 112 is provided with a protrusion 110, the front end of the protrusion 110 is used to engage with the second step 53, and the rear end is used to lift the arc guide surface 52. Preferably, the top of the rear end of the protrusion 110 can be designed to be an arc surface, which is smoother when contacting and passing with the arc guide surface 52. The upper end of the elastic clamp 116 is provided with an elbow 61 that can abut against the rear end of the protrusion 110, and the lower end is connected to the chassis at the bottom of the consumable cavity. In addition, the front end of the heating consumable 112 is also provided with a handle 120 for easy pushing and pulling.

[0083] Please combine Figure 6 As shown, during installation, the consumables can be inserted from the insertion port of the box body 111 using the handle 120. When the protrusion 110 contacts the arc guide surface 52 (see Figure 7 ), the movable pressing plate 115 will continue to push up and pass under the raised movable pressing plate 115, until the protrusion 110 completely passes, the movable pressing plate 115 falls down and resets under the action of the torsion spring 54 and makes the second step 53 just engage with the front end of the protrusion 110, and at the same time, the other end of the protrusion 110 pushes the elbow 61 of the elastic clamping plate 116 backward for a distance (see Figure 8 ), at this time, the consumables are positioned and fixed by the reaction forces in two directions of the second step 53 of the movable pressing plate 115 and the elastic clamping plate 116, and the loading is completed. When disassembling, it is only necessary to press the button 7 to drive the prying head 42 of the movable lever 114 to tilt upward, drive the movable pressing plate 115 and its second step 53 to lift up, so that the consumables are free from the lock of the second step 53, and pop outward under the rebound force of the elastic clamping plate 116 to get out of the position of the second step 53. At this time, the consumables can be easily pulled out of the box body 111 through the handle 120.

[0084] However, those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for heating a medical liquid, characterized in that: The following steps are involved: A. a liquid heating flow path is provided, which includes a velocity measuring section and a heating section in sequence, and a first heater is used to heat the liquid in the velocity measuring section entering the liquid heating flow path; B. Use the first temperature sensor to measure the temperature of the liquid before it enters the speed measuring section, use the second temperature sensor to measure the temperature of the heated liquid entering the speed measuring section, and calculate the reference flow rate of the liquid based on the temperature rise difference of the liquid measured by the two sensors; C. calculating the energy required for heating to the target temperature according to the reference flow rate, and using the energy to control the initial heating power of the second heater to preheat the liquid flowing through the heating section; D. Using a third temperature sensor to measure the temperature of the liquid at the end of the heating section in real time, and using the difference between the measured liquid outlet temperature and the target temperature to provide real-time feedback to adjust the heating power of the second heater; In step B, the reference flow rate is obtained by: The average specific heat capacity of the heated liquid is selected as the reference value, and the comparison relationship between the flow rate and the temperature rise difference of the liquid is obtained through simulation tests, and then the reference flow rate corresponding to the reference value is obtained; The calculation formula of the reference flow rate is: V1=(K2*P+K3*B*ΔT) / (K3*ΔT+K1*K2*P), V1 is the reference flow rate, P is the power of the first heater, ΔT is the liquid temperature rise, K1, K2, K3, and B are all constants obtained by experimental test calculations; In step C, the calculation formula of the initial heating power is: Pwm1=C*V1 / ΔT, C is the experimental calibration parameter, Pwm1 is the initial heating power; In step D, the calculation formula of the heating power is: Pwm2=Kp*e(k)+Ki*∑e(k)+Kd[e(k)-e(k-1)]+Kb, Kp, Ki, Kd, ​​and Kb are constants measured experimentally. The corresponding PID adjustment parameters are adjusted through experiments according to different reference flow rates. e(k) is the difference between the measured liquid temperature and the target temperature, k is 1, 2, ..., k, e(k-1) is the difference between the last measured liquid temperature and the target temperature. ∑e(k) is the cumulative sum of e(k) and the previous difference, Pwm2 is the heating power.

2. A method for heating medical liquid according to claim 1, characterized in that: In step A, the speed measuring section is intermittently heated by the first heater, and the temperature is measured by the second temperature measuring sensor to detect whether liquid flows in.

3. A method for heating medical liquid according to claim 1, characterized in that: In step D, a fourth temperature measuring sensor disposed near the third temperature measuring sensor is also used to perform redundant temperature measurement.

4. A method for heating medical liquid according to claim 1, characterized in that: The liquid heating flow path adopts a serpentine channel structure, with one side being a transparent surface and the other side being a light-shielding surface.

5. A method for heating medical liquid according to claim 4, characterized in that: The first heater adopts an infrared halogen tungsten lamp tube, which is arranged outside the transparent surface of the liquid heating flow path, and has a length corresponding to the speed measuring section, and is covered with the speed measuring section by a metal light-shielding cover with a reflective coating on the inner wall.

6. A method for heating medical liquid according to claim 4, characterized in that: There are several second heaters, all of which are independently controllable infrared halogen tungsten lamps and are evenly arranged outside the transparent surface of the serpentine channel.

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