Circulating fluids and lubricating modifiers

Abstract

The present invention realizes a lubrication characteristic that can withstand a pressing force equivalent to that at the time of inserting a catheter into a blood vessel of a real human body, even when a water-based circulation liquid is applied to a blood vessel model.　This circulation liquid is to be used in a catheter simulator and contains a water-soluble polymer. The water-soluble polymer includes a water-soluble polymer having both a hydrophilic group and a hydrophobic group, and / or a mixture of a polymer having a hydrophilic group and a polymer having a hydrophobic group.

Description

Technical Field

[0001] The present invention is suitable for use as a circulating fluid for a catheter simulator using a blood vessel model made of silicone rubber, urethane rubber, or the like. Further, the lubricity adjuster of this invention improves the lubricity between crosslinkable polymer materials.

Background Art

[0002] The inventor has developed and marketed a catheter simulator that mimics the human body (see Patent Document 1). In this catheter simulator, a partition member is built into a mannequin body made of a transparent material, a blood vessel model as a three-dimensional model is supported on one surface of the partition member, and an auxiliary device for operating the blood vessel model is arranged. The blood vessel model is formed of silicone rubber, and the auxiliary device includes a tank, a pump, and a connecting tube. A circulating fluid is stored in the tank, and this circulating fluid circulates through the blood vessel model via the connecting tube by the pump. When a catheter is inserted into this blood vessel model, the lubricity between the silicone rubber surface and the catheter surface becomes a problem. Further, refer to Patent Document 2 as a document that discloses a technique related to the present invention.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the catheter simulator disclosed in Patent Document 1, it is possible to insert a catheter into a blood vessel model made of silicone rubber while circulating a circulating fluid through the blood vessel model. As circulating fluids, silicone oil-based fluids (oil-based circulating fluids) and water-based fluids (water-based circulating fluids) are used, but water-based circulating fluids are preferred due to their similarity to blood. If water is simply circulated through the vascular model, the contact resistance of the catheter against the inner wall of the vascular model becomes large, making it difficult to insert the catheter smoothly. Therefore, a surfactant is mixed with water as a lubrication modifier. This reduces frictional resistance between the catheter and the inner surface of the vascular model, allowing the catheter to be inserted smoothly into the vascular model.

[0005] However, even when a circulating fluid, made by mixing a surfactant with water, is circulated through a vascular model, it does not reproduce the blood vessels in which actual blood circulates. Therefore, in simulations using such a circulating fluid, it was undeniable that the sensation of catheter insertion felt unnatural compared to actual surgery. For example, when the catheter passed through tortuous sections of the vascular model, the frictional resistance was extremely large compared to actual surgery. In addition, when the inserted catheter was left undisturbed for several seconds, the static friction coefficient between the catheter and the vascular model became abnormally large, and a phenomenon (hereinafter referred to as "adhesion") was observed where it became difficult to push the inserted catheter in or out.

[0006] The lubricity modifier disclosed in Patent Document 2 was developed to improve this problem. By using a surfactant and a water-soluble metal salt in combination as a lubricity modifier, the sensation of inserting a catheter into a vascular model can be made closer to the sensation of inserting a catheter during actual surgery. Using the lubricity modifier disclosed in Patent Document 2, adhesion between the vascular model and the catheter can be prevented even in the tortuous parts of the vascular model, and the problem of a sudden increase in insertion resistance during catheter manipulation can be solved.

[0007] Even when using the lubricity modifier disclosed in Patent Document 2, adhesion sometimes occurred when the force pressing the catheter against the blood vessel wall (hereinafter referred to as "pressure force") increased to about 5N (approximately 0.5kg) or more. In human blood vessels, similar adhesion occurs when the pressure increases, but as a result of evaluation by the inventors, it was confirmed that even when using the lubricity modifier, adhesion occurred with a smaller pressure compared to human blood vessels. In an attempt to avoid adhesion, attempts were made to increase the amount of surfactant and water-soluble ionic compound added, but the effect saturated even when the amount added was increased, and it was not possible to reproduce properties equivalent to those of human blood vessels. Furthermore, increasing the amount of surfactant mixed in is undesirable because it causes a slimy feeling in the circulating fluid.

[0008] While using silicone oil as a circulating fluid was effective in preventing adhesions, so-called oil-based silicone oils (including those dispersed in water using emulsifiers, etc.) and water-soluble silicone oils such as polyether-modified silicones had properties that differed too much from blood, resulting in an unrealistic feel when handling the catheter during insertion. [Means for solving the problem]

[0009] The inventors have diligently conducted research to achieve lubrication properties that can withstand the same pressing force as when inserting a catheter into an actual human blood vessel, even when applying a so-called aqueous circulating fluid to a vascular model. As a result, they discovered that by using a specific water-soluble polymer, the catheter's resistance to adhesion to the vascular model is significantly improved, approaching the characteristics of human blood vessels during actual surgery. This allows the catheter to pass through areas where large pressing forces are likely to occur during surgery, such as the common iliac artery, aorta, and common carotid artery, without adhesion between the inner surface of the vascular model and the catheter, providing a similar feel to actual surgery.

[0010] In other words, the first aspect of this invention is defined as follows: A circulating fluid used in a catheter simulator, comprising a water-soluble polymer, wherein the water-soluble polymer comprises a water-soluble polymer having both hydrophilic and hydrophobic groups, and / or a mixture of a polymer having hydrophilic groups and a polymer having hydrophobic groups.

[0011] According to the circulating fluid in the first phase as defined above, in the case of a water-soluble polymer possessing both hydrophilic and hydrophobic groups, the hydrophobic (lipophilic) group of the water-soluble polymer is linked to the inner surface of the blood vessel model, exposing its hydrophilic group. Another hydrophilic group of the water-soluble polymer is linked to this hydrophilic group, exposing its hydrophobic group. Another hydrophobic group of the water-soluble polymer is linked to this hydrophobic group, exposing its hydrophilic group, and so on, forming multiple layers of water-soluble polymer on the inner surface of the blood vessel model. Although the bonding force between each layer of such water-soluble polymer is weak, the complex entanglement of polymer chains of a certain length forms a robust lubricating layer that is difficult to separate from the inner surface. Therefore, the inner surface of the blood vessel model acquires physical properties similar to those of endothelial cells present inside human blood vessels, and lubrication can be maintained without adhesion even when a large pressing force is applied to the catheter. As a result, the catheter exhibited the same passability and handling sensation (friction) as in actual surgery, both in areas where small compressive forces are typically applied, such as the cerebral artery region, and in areas where large compressive forces are applied, such as the aorta.

[0012] While it was possible to reproduce lubrication properties similar to those of human blood vessels by pre-treating the inner surface of a blood vessel model with hydrophilic properties using various methods, the hydrophilic layer formed in this way was prone to changes in properties due to deterioration over time, adhesion of foreign matter to the surface, and wear during use. According to the method of the present invention, even if the water-soluble polymer attached to the inner surface of the blood vessel model is lost due to wear, etc., the water-soluble polymer dissolved in the circulating fluid will reattach to the inner surface of the blood vessel model and replenish it, thus maintaining a constant set of properties. Furthermore, after use, the water-soluble polymer is discharged and removed along with the circulating fluid, and then replenished with new circulating fluid at the next use, so that a new water-soluble polymer is always supplied, and no fluctuations in properties occur.

[0013] As a result, in a catheter simulator equipped with a vascular model in which the first phase circulating fluid is flowing, the sensation of inserting a catheter into the vascular model becomes closer to the sensation of inserting a catheter into a human blood vessel. Furthermore, the multiple layers of water-soluble polymers ensure that adhesion resistance is maintained even when a large pressing force is applied to the catheter.

[0014] Examples of water-soluble polymers possessing both hydrophilic and hydrophobic groups include PVA (polyvinyl alcohol) and methylcellulose. In addition to natural polymers such as proteins and starch, other examples include synthetic polymers such as polyacrylic acid, polyacrylamide, polyethylene oxide, poly(vinylpyrrolidone), polyvinylamide, and polyamines. The molecular weight (degree of polymerization) and amount of these water-soluble polymers can be arbitrarily selected according to the diameter and area of ​​the inner surface of the vascular model used in the catheter simulator, the type of catheter, etc. The amount of water-soluble polymers is preferably about 0.5 to 8.0% by mass relative to water.

[0015] From the standpoint of material cost, decomposition after use, and ease of cleaning, the use of PVA is preferred. In the case of PVA, The degree of polymerization is approximately 500 to 2000. It is preferable to do so, and it is preferable that the degree of saponification be 75 or higher. In the case of PVA, it is preferable to maintain the pH in the range of weakly basic to weakly acidic, both from the standpoint of ensuring its dispersibility and from the viewpoint of making it as close as possible to human blood, and for this purpose, it is preferable to incorporate a pH buffering agent.

[0016] Since PVA is essentially a liquid glue, after use in a catheter simulator, the water evaporates and forms a film that adheres to various substrates, potentially causing blockages and adhesion, which could hinder subsequent use. To prevent the formation of films by water-soluble polymers such as PVA, it is preferable to mix sugars (such as sucrose or fructose) into the circulating fluid. By mixing in sugars, film formation is suppressed when the circulating fluid containing water-soluble polymers such as PVA dries (evaporates), and even if it becomes powdery after drying and adheres to various substrates, it can be easily removed. The amount of sugars can be appropriately selected depending on the properties of water-soluble polymers such as PVA, but it is preferable to blend 50 to 200 parts by mass of sugars per 100 parts by mass of PVA.

[0017] In the case of a mixture of a water-soluble polymer with hydrophilic groups and a water-soluble polymer with hydrophobic groups, the two polymers are thought to intertwine with each other in the circulating fluid, forming molecules that outwardly possess both hydrophilic and hydrophobic groups. Such molecules possessing both hydrophilic and hydrophobic groups, like the previously described water-soluble polymers such as PVA and methylcellulose which possess both hydrophilic and hydrophobic groups on their own, overlap in multiple layers on the inner surface of the vascular model, forming layers of molecules that exhibit lubricity and toughness similar to PVA and methylcellulose.

[0018] Here, the mixing ratio of the water-soluble polymer having hydrophilic groups to the water-soluble polymer having hydrophobic groups is preferably 1:1 for the total amount of hydrophilic groups to the total amount of hydrophobic groups, but is not particularly limited. In order for water-soluble polymers with hydrophilic groups and polymers with hydrophobic groups to be reliably intertwined, the main chain constituting the polymer needs to have a predetermined length.

[0019] In addition to the water and water-soluble polymers mentioned above, it is preferable to add a lubricity modifier as described in Patent Document 2 to the circulating fluid. The contents of Patent Document 2 are quoted here for reference. As previously mentioned, water-soluble polymers possessing both hydrophilic and hydrophobic groups, and mixtures of water-soluble polymers with hydrophilic groups and polymers with hydrophobic groups, are also lubricity modifiers. As a lubricity adjuster, it can be blended alone, together with a surfactant, or together with a surfactant and a water-soluble ionic compound into the circulating fluid of the catheter simulator.

[0020] In the lubricity adjuster, the role of the surfactant is mainly to reduce the kinetic friction coefficient between objects (such as between the silicone rubber surface and the catheter surface), and to promote the bonding (multilayer formation) of the water-soluble polymer by the interaction (ionic bond, hydrophobic bond, hydrogen bond, covalent bond, etc.) between the surfactant and the water-soluble polymer. Thereby, for example, when the catheter contacts the surface of a silicone rubber vascular model, the resistance when inserting the catheter is reduced, and the operator can smoothly insert the catheter into the vascular model.

[0021] On the other hand, the role of the water-soluble ionic compound is, in addition to reducing the above-mentioned kinetic friction coefficient, to prevent adhesion between the silicone rubber and the member in contact with the silicone rubber (that is, to reduce the static friction coefficient), and to further promote the bonding (multilayer formation) of the water-soluble polymer by the interaction (ionic bond, hydrophobic bond, hydrogen bond, covalent bond, etc.) between the water-soluble ionic compound, the surfactant, and the water-soluble polymer, and to enhance the toughness of the formed lubricating layer.

[0022] When the layer composed of this surfactant and water-soluble ionic compound does not contain a water-soluble polymer, it is likely to collapse when the pressing force of the catheter increases, and the surfaces of the catheter and the vascular model come into direct contact and adhesion occurs. Water-soluble polymers (same molecules) having both hydrophilic and hydrophobic groups, like surfactants, have the effect of reducing the coefficient of dynamic friction by forming a lubricating layer between objects (such as between the surface of silicone rubber and the surface of a catheter). When a water-soluble polymer is added to a circulating fluid that already contains a surfactant and a water-soluble ionic compound, the interaction between the surfactant and the water-soluble ionic compound (ionic bonds, hydrophobic bonds, hydrogen bonds, covalent bonds, etc.) creates a multilayer structure similar to a lamellar structure, and the molecular chains of the water-soluble polymer become intricately intertwined over a wide area, forming a robust lubricating layer. As a result, the adhesion resistance of this lubricating layer is significantly improved compared to when only surfactants and water-soluble ionic compounds are used, and adhesion does not occur even when a large pressing force of 15N (approximately 1.5kg) or more is applied to the catheter, maintaining lubrication properties similar to those of human blood vessels. When water-soluble polymers are not added, a lubricating layer that can withstand a pressing force of 15N for more than a few seconds is not formed.

[0023] According to the inventor's evaluation, the lubricating layer formed on the inner surface of the blood vessel model becomes remarkably resistant to the pressure of a catheter, especially when a surfactant, a water-soluble ionic compound, and a water-soluble polymer (same molecule) having both hydrophilic and hydrophobic groups are present together, and was able to withstand a catheter pressure comparable to that of human blood vessels.

[0024] In actual living blood vessels, catheters and guidewires are designed to slide well against the inner wall of the vessel. Conversely, aneurysm embolization coils and the like, because they are implanted in the body after surgery, need to maintain a stable position and are therefore designed not to slide (move) within living blood vessels (aneurysms).

[0025] When only surfactants and water-soluble ionic compounds were added, as with conventionally used circulating fluids, the lubricity of the catheter, guidewire, and aneurysm embolization coil inserted into the vascular model improved similarly with increasing amounts of additives, and no difference in the tendency towards improved lubricity was observed among them. As a result, when the coil was placed in an aneurysm attached to the vascular model, unlike during actual surgery, the coil continued to move unstably both during and after placement due to catheter manipulation during placement and blood flow after placement.

[0026] In contrast, when three substances—a surfactant, a water-soluble ionic compound, and a water-soluble polymer (same molecule) having hydrophilic and hydrophobic groups—are added as in the present invention, the slipperiness of the catheter and guidewire improves with increasing amounts (the coefficient of friction decreases significantly), but no change is observed in the slipperiness of the aneurysm embolization coil (the coefficient of friction hardly changes). As a result, when the aneurysm embolization coil was placed in an aneurysm formed in a vascular model, the catheters exhibited good slipperiness similar to that in living blood vessels, while the coil remained stably positioned without moving much due to catheter manipulation or blood flow, both during and after placement, just as in actual surgery.

[0027] Thus, experimental results clearly demonstrate that the lubrication mechanism of the circulating fluid of the present invention is different from that of conventionally used circulating fluids (which only contain surfactants and water-soluble ionic compounds). As a result, by using the circulating fluid of the present invention, the frictional characteristics of catheters and aneurysm embolization coils can be differentiated, adjusted, and reproduced, and lubrication characteristics similar to those in living blood vessels can be well reproduced.

[0028] Another characteristic of the circulating fluid of the present invention is its improved water retention (resistance to drying). While the addition of conventional circulating fluids (containing only surfactants and water-soluble ionic compounds) did not significantly affect the water retention (resistance to drying) of the liquid (usually water), the circulating fluid of the present invention shows a significant improvement in water retention (resistance to drying) because a network is formed through the interaction between the surfactant, water-soluble ionic compounds, and water-soluble polymers, allowing moisture to be stored within it.

[0029] Furthermore, another characteristic is that when the circulating fluid of the present invention is added to a liquid (usually water), the gas dissolved in the liquid does not precipitate on the surface of the container holding the liquid or on the surface of objects such as vascular models or catheters immersed in the liquid. Even the bubbles that were initially present dissolved into the circulating fluid and disappeared over time. Also, when a liquid such as water is placed in a sealed container with gaps remaining (not liquid-tight), clouding generally occurs on the surface of these gaps due to the evaporation of the liquid. However, when using the circulating fluid of the present invention, such clouding did not occur (whether the circulating fluid adhered to and removed the gaps or not). Conventional circulating fluids did not affect this bubble generation and adhesion phenomenon (although the addition of surfactants made bubbles smaller and easier to adhere, there was no change in bubble generation itself, and no effect was obtained to incorporate bubbles into the liquid and make them disappear).

[0030] In conventional circulating fluids, or when no circulating fluid is used, air bubbles dissolved in the circulating fluid precipitate and adhere to the surface of the object, reducing visibility during catheter simulations. Therefore, it was necessary to periodically remove the air bubbles by stirring or other means. In contrast, when using the circulating fluid of the present invention, no air bubbles are generated during the simulation. Air bubbles that were present from the beginning during the preparation stage, as well as air bubbles that entered the fluid via the catheter, automatically disappear. A bubble-free state is naturally formed and maintained at all times in the fluid and on the surface of the object, resulting in significantly improved visibility and eliminating the need for air bubble removal, allowing for comfortable surgical simulations. This effect is considered to be applicable to uses other than catheter surgical simulations as a lubricant.

[0031] Furthermore, when three components—a surfactant, a water-soluble ionic compound, and a water-soluble polymer (same molecule) having both hydrophilic and hydrophobic groups—were added as in the present invention, the viscosity of the lubricating fluid increased. When only a surfactant and a water-soluble ionic compound were added to water, as in conventional lubricating fluids, no significant change in viscosity was observed (tap water: 1.25 mPa·s, compared to 1.28 mPa·s for tap water with a surfactant (0.4 wt%) and saturated water-soluble ionic compound (2 wt%) added). However, when a water-soluble polymer (PVA 1.1 wt%) was added, the viscosity increased significantly (2.91 mPa·s), resulting in a large discrepancy with the viscosity of biological blood (approximately 1.3-1.7 mPa·s). As a result, when a catheter was inserted into a vascular model and a pressure equivalent to blood pressure (120 mmHg) was applied to the circulating fluid filling the vascular model, changes were observed in the flow rate, etc., of the fluid passing through the inside of the catheter and flowing out from the other end of the catheter (using the Excelsior 1018 microcatheter and applying 120 mmHg, the outflow rate when using conventional circulating fluid was 0.83 ml / min, and the outflow rate when using the lubricating fluid of the present invention was 0.33 ml / min).

[0032] In the case of adding a surfactant, a water-soluble ionic compound, and a water-soluble polymer (same molecule) having hydrophilic and hydrophobic groups, as in the present invention, we diligently investigated methods to reduce the viscosity to a value similar to that of blood while maintaining its excellent lubrication properties. As a result, we found that the viscosity can be adjusted by further adding a pH adjuster (buffering agent) and changing the pH, and that even when using the lubricant of the present invention, it is possible to reproduce a viscosity similar to that of blood without impairing its excellent lubrication properties (without pH adjuster: pH 6.1, viscosity 2.91 mPa·s; in contrast, with pH adjuster (carbonate ions, etc.) added: pH 6.8, viscosity 1.44 mPa·s). This is presumed to be because the addition of a pH adjuster causes a change in the polymer network composed of the surfactant, water-soluble ionic compound, and water-soluble polymer having hydrophilic and hydrophobic groups, and it was found that a pH adjuster can be effectively used to adjust the polymer network formed when the lubricant of the present invention is used.

[0033] Here, depending on the material of the catheter sheath, one or more surfactants from the group consisting of cationic surfactants, anionic surfactants, nonionic surfactants, and amphoteric surfactants can be used as appropriate. In the above, it is preferable to use deionized water, but tap water may also be used. It is preferable to select the type of surfactant according to the catheter material. For example, when the sheath is made of Teflon® or polyethylene, which tend to become negatively charged when rubbed, it is preferable to use an anionic surfactant. On the other hand, when the sheath is made of a material that tends to become positively charged, such as polyamide, it is preferable to use an amphoteric surfactant.

[0034] In endovascular treatment training, it is difficult to determine the charge tendency of the catheter sheath and other materials used (such as the zeta potential and the effects of the triboelectric series during triboelectric charging). When using tap water, the electrolyte components and amounts are not constant, and the pH fluctuates accordingly, making it even more difficult to determine the charge tendency. For this reason, it is preferable to adjust the type and amount of surfactant added as appropriate before or during the simulation by confirming the characteristics during actual use. As the surfactant, a single amphoteric surfactant, a cationic surfactant with an amphoteric surfactant added, or an anionic surfactant with an amphoteric surfactant added can be used. This ensures that the surfactant is stably adsorbed onto the surface of the catheter sheath, regardless of the material of the catheter sheath. The recommended mixing ratio of anionic surfactants (or cationic surfactants) to amphoteric surfactants is 100% anionic surfactants (or cationic surfactants). quality It is preferable to blend 1 to 100 parts by mass of an amphoteric surfactant with the total volume of the product.

[0035] The concentration of the surfactant can be adjusted as appropriate depending on the type of surfactant, the type and concentration of other solvents, and the intended use, but a range of 0.005 mmol / L to 100 mmol / L is preferred. Within this range, low contact resistance is ensured, and desirable physical properties for a circulating fluid are obtained (no slimy feeling). A range of 0.05 mmol / L to 10 mmol / L is even more preferred.

[0036] As water-soluble ionic compounds, water-soluble metal salts and water-soluble ammonium salts (e.g., ammonium chloride and ammonium sulfate) can be used. As water-soluble metal salts, one or more from the group consisting of alkali metal salts, alkaline earth metal salts, aluminum salts, and iron salts can be used. Examples of water-soluble alkali metal salts include sodium chloride, potassium chloride, cesium chloride, sodium sulfate, potassium sulfate, cesium sulfate, sodium nitrate, potassium nitrate, and cesium nitrate. Examples of water-soluble alkaline earth metal salts include magnesium chloride, calcium chloride, barium chloride, magnesium nitrate, calcium nitrate, and barium nitrate. Examples of aluminum salts include aluminum chloride, aluminum sulfate, and aluminum nitrate. Examples of iron salts include ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, ferrous nitrate, and ferric nitrate. In addition to the above, it is also possible to use water-soluble alkali metal salts, alkaline earth metal salts, organic acid salts of metals (e.g., sodium acetate), and complexes.

[0037] The concentration of water-soluble metal salts in the circulating fluid is preferably between 1 mmol / L and 100 mmol / L. More preferably between 2 mmol / L and 50 mmol / L. Although the function of these water-soluble ionic compounds is not clear, in the absence of these compounds, when a large pressing force of 5N (approximately 0.5kg) or more is applied to the catheter, the degree to which the catheter adheres to the inner surface of the vascular model increases.

[0038] As water-soluble polymers having both hydrophilic and hydrophobic groups, those that structurally combine hydrophilic and hydrophobic groups, such as polyvinyl alcohol and methylcellulose, or complexes thereof, can be used. Furthermore, similar effects were obtained by mixing a water-soluble polymer material having only hydrophilic groups, such as sodium polyacrylate or carboxymethylcellulose, with a water-soluble polymer material having only hydrophobic groups, such as alginic acid. However, the effects of the present invention were not observed when a water-soluble polymer material having only hydrophilic groups (e.g., sodium polyacrylate or carboxymethylcellulose) or a water-soluble polymer material having only hydrophobic groups (e.g., alginic acid) was used alone. This is thought to be because when both are dispersed in water, they become entangled and outwardly behave as molecules possessing both hydrophilic and hydrophobic properties. [Brief explanation of the drawing]

[0039] [Figure 1] Figure 1 is a perspective view of the measuring device for measuring the characteristics of the circulating fluid according to this invention. [Figure 2] Figure 2 shows the sinusoidal trajectory of the reciprocating motion of the catheter as measured by the measuring device. [Figure 3] Figure 3 shows the change in the reaction force on the catheter when it is moved back and forth as shown in Figure 2. [Figure 4] Figure 4 shows the rectangular wave trajectory of the reciprocating motion of the catheter as measured by the measuring device. [Figure 5] Figure 5 shows the change in the reaction force on the catheter when it is moved back and forth as shown in Figure 4, in comparison to the reciprocating motion speed. [Figure 6] Figure 6 shows the change in the reaction force on the catheter when it is moved back and forth as shown in Figure 4, for various circulating fluids. [Figure 7] Figure 7 shows the change in reaction force on the catheter when it is moved back and forth as shown in Figure 4 in relation to various circulating fluids, while keeping the concentrations of the surfactant and water-soluble ionic compound constant. [Figure 8] Figure 8 shows that the reaction force against the catheter is maintained even in circulating fluids containing sugars. [Modes for carrying out the invention]

[0040] The inventors created the measuring device 20 shown in Figure 1 to measure the difference in lubricity. This measuring device 20 comprises a substrate 21, a fixing part 25, and a clip part 30. Two sets of a pair of poles 37, 37 are erected on a plastic substrate 21 as fixing parts 25. The clip part 30 comprises a pair of bars 31, 31 and a pair of elastic sheets 32, 32.

[0041] The pair of bars 31, 31 fixed by the fixing part 25 are biased by rubber bands 35, 35 to be close to each other when gripping the blood vessel model 5. Elastic sheets 32, 32 are interposed between the bars 31, 31 and the blood vessel model 5. These elastic sheets 32, 32 are set to a thickness of 6 mm and a hardness of HC12.5 to mimic the human aortic wall. The fastening force generated by the rubber bands 35, 35 presses the catheter 1 against the inner surface of the blood vessel model 5 via the bars 31, 31 and the elastic sheets 32, 32, thereby generating the aforementioned pressing force between the catheter and the inner surface of the blood vessel model.

[0042] The plastic substrate 21 is fixed to the workpiece mounting surface of a general-purpose machine tool. By operating the machine tool, the substrate 21 moves together with the workpiece mounting surface. As a result, the entire measuring device 20, excluding the catheter 1, moves in any direction and at any speed according to the operation set by the machine tool. The left end of the catheter 1 inserted into the blood vessel model 5 is connected to a force sensor, and the force sensor is fixed to the machine tool body or a mounting base for the machine tool body so as to move relative to the mounting surface. In this example, the measuring device 20 excluding the catheter 1 was moved by fixing the substrate 21 to the workpiece mounting surface of the machine tool. Conversely, the same measurement could also be performed by fixing the force sensor connected to the catheter 1 to the workpiece mounting surface of the machine tool, thereby fixing the measuring device 20 excluding the catheter 1 in space and moving the force sensor (i.e., the catheter 1). When installing a video camera or the like to take fixed-point photos of the fixing part 25, etc., in the configuration of this example, it is good to fix the video camera to the workpiece mounting surface in the same way as the measuring device 20 via a fixing device such as a camera arm.

[0043] In this example, the entire measuring device 20, excluding the catheter 1, is moved back and forth perpendicular to the bars 31, 31 (i.e., in the axial direction of the catheter 1). The catheter 1 is fixed to the movable part of a linear slider 3 attached to the base plate 21 and can move in only one direction. This ensures that the catheter 1 and the entire measuring device 20 can perform relative linear motion reliably and stably. Furthermore, by sandwiching the blood vessel model 5 between the bars 31, 31 via the elastic sheets 32, 32, it was possible to reproduce the state in which human blood vessels are flexibly supported from the surrounding tissue within the body, and the pressing force of the catheter is widely distributed to the surrounding tissue. This allowed us to obtain catheter and blood vessel dynamics and measurement results that are close to those during actual catheter surgery.

[0044] The circulating fluid of the present invention was prepared by dissolving PVA as a water-soluble polymer having hydrophilic and hydrophobic groups in a circulating fluid using a lubricity modifier introduced in Patent Document 2 (comparative circulating fluid), that is, a mixture of a surfactant and a water-soluble ionic compound dissolved in water. This circulating fluid was then filled into a blood vessel model made of silicone rubber, and a catheter with a polyethylene sheath was inserted into the blood vessel model. The measurement was then performed by applying a sinusoidal reciprocating motion trajectory A shown in Figure 2 to the measuring device, and the results are shown in Figure 3. This reciprocating motion trajectory A was set to reproduce the "dithering motion," which is a motion in which adhesion is likely to occur (the lubrication layer is easily lost) during actual surgery. The section with a small amplitude in the middle of the reciprocating motion A is the section specifically intended to reproduce this motion. The horizontal axis in Figure 2 represents time, and from the change in frequency of the graph, it can be seen that the speed of the reciprocating motion by the arm gradually increases from slow to fast, and then slows down again.

[0045] Here, by adjusting the tension of the rubber band, we applied a maximum pressure of 15N (approximately 1.5kg) to the catheter, which is the maximum pressure that may be applied to the catheter between the catheter and the blood vessel wall during actual surgery, and performed the measurement under these conditions. As shown in Figure 3, under a large pressing force of 15 N, the circulating fluid without water-soluble polymers (containing only surfactants and water-soluble ionic compounds) generated a very large reaction force exceeding 10 N on the catheter during reciprocating motion. When this circulating fluid was used, the lubricating layer was lost and adhesion occurred throughout the entire measurement section, and the reciprocating motion continued in this adhered state. Such adhesion occurred when the pressing force exceeded approximately 5 N when using this circulating fluid. In contrast, with a circulating fluid containing water-soluble polymers in addition to surfactants and water-soluble ionic compounds, the lubricating layer was maintained throughout the entire measurement section without loss, and the reciprocating motion continued throughout the entire section while maintaining lubrication similar to that of human blood vessels.

[0046] The results in Figure 3 show that by incorporating PVA, a water-soluble polymer, a robust lubricating layer with excellent lubricity is formed, and the frictional resistance between the catheter and the vascular model is significantly suppressed even when a large catheter pressing force is applied.

[0047] Figure 5 shows the results of measurements taken using the rectangular wave-shaped reciprocating motion trajectory B shown in Figure 4, in order to measure the reaction force (insertion force) generated in the catheter during its reciprocating motion in a manner that can be compared with the speed of the reciprocating motion. It also explains the method of organizing the measurement data from Figure 6 onward. In this reciprocating motion trajectory B, the catheter is moved back and forth in a step-like manner, and in order to measure the presence and degree of adhesion when the catheter is stationary, a 0.25-second pause (movement stop section) is provided at each time point indicated by a circle on the graph in Figure 4, allowing for the evaluation of adhesion after four types of pauses: (1) catheter forward movement followed by a pause and then forward movement, (2) forward movement followed by a pause and then backward movement, (3) backward movement followed by a pause and then backward movement, and (4) backward movement followed by a pause and then forward movement. Furthermore, in order to make it easier to identify the differences and characteristics of the reaction forces for multiple water-soluble polymers, as shown in Figure 5, the difference between the maximum value (tensile force applied to the catheter) and the minimum value (compressive force applied to the catheter) of the reaction force in each reciprocating cycle (the section combining forward and backward movement) (the range indicated as Peak to Peak in Figure 5) was extracted from measurement data for each movement speed from 150 mm / min to 7200 mm / min, and converted into a set of 14 numerical values.

[0048] Figure 6 shows the measurement data obtained when the measuring device 20 is subjected to the rectangular wave-shaped reciprocating motion trajectory B shown in Figure 4, and the obtained measurement data is expressed using the method described with reference to Figure 5. This figure shows the reaction force (insertion force) applied to the catheter for eight types of circulating fluids with different combinations of (1) water, (2) surfactant, (3) water-soluble ionic compound, and (4) water-soluble polymer (PVA). The reaction forces shown in the bar graphs of 14 bars in Figure 6 are the peak-to-peak values ​​of the reaction force (catheter insertion force) for each movement speed described with reference to Figure 5. For each set, the bar graphs from left to right show the reaction force values ​​at 150, 300, 600, 1200, 1800, 2400, 3000, 3600, 4200, 4800, 5400, 6000, 6600, and 7200 mm / min.

[0049] As shown in the measurement results in Figure 6, the overall trend is that the reaction force (catheter insertion force) is greater in the region of slow movement speed than in the region of fast movement speed. This trend can be suppressed by adding ionic compounds. It can also be confirmed that lubricity is not exhibited by ionic compounds alone. Furthermore, it can be confirmed that the lubricity obtained by surfactants and water-soluble polymers can be enhanced by adding ionic compounds.

[0050] Furthermore, the results in Figure 6 show that the circulating fluid with both surfactant and water-soluble polymer added generates a greater reaction force than the circulating fluid with only water-soluble polymer added. This confirms that not only is the synergistic effect of mixed addition not achieved, but the lubricating properties of the water-soluble polymer are impaired by the mixing. In circulating fluids to which surfactants, ionic compounds, and water-soluble polymers are added, it can be confirmed that a significant synergistic effect on lubrication occurs without any impairment of the properties of each component.

[0051] Furthermore, unlike the sinusoidal trajectory A (Figure 2), the toughness of the lubricating layer is not easily expressed as a characteristic in the measurement results using this rectangular wave trajectory B (Figure 4). For this reason, the differences may appear small, but in the liquids to which the three types are added, the toughness of the lubricating layer is significantly improved compared to other circulating fluids. This difference in the toughness of the lubricating layer can be explicitly measured using the measurement method that uses the sinusoidal trajectory A (Figure 2, dithering). When the toughness is low, in the section where the amplitude of the sinusoidal trajectory A is small, the lubricating layer collapses, the catheter and the inner surface of the vascular model come into direct contact, and a large reaction force is generated in the same section due to protrusion.

[0052] Figure 7 shows the results of measuring and organizing circulating fluids obtained by changing the type of water-soluble polymer while keeping the concentrations of surfactants and water-soluble ionic compounds constant, using the same measurement method as in Figure 6. In Figure 7, No. 1 is a circulating solution that does not contain water-soluble polymers, but only surfactants and water-soluble ionic compounds. The water-soluble polymer used in No. 2 is PVA (saponified type), and the amount added is 0.8 wt%. The water-soluble polymer used in No. 3 is PVA (fully saponified type), and the amount added is 0.8 wt%. The water-soluble polymer used in No. 4 is PVA (degree of polymerization 2000), and the amount added is 0.8 wt%. The water-soluble polymer used in No. 5 is PVA (degree of polymerization 500), and the amount added is 0.8 wt%. The water-soluble polymer used in No. 6 is PVP, and the amount added is 0.8 wt%. The water-soluble polymer used in No. 7 is vinyl acetate, added at a concentration of 0.8 wt%. The water-soluble polymer incorporated into No. 8 is PEG (molecular weight 200), and the amount added is 0.8 wt%. The water-soluble polymer incorporated in No. 9 is PEG (molecular weight 200), and the amount added is 1.6 wt%. The water-soluble polymer incorporated in No. 10 is PEG (molecular weight 200), and the amount added is 4.0 wt%. The water-soluble polymer incorporated in No. 11 is PEG (molecular weight 200), and the amount added is 8.0 wt%. The water-soluble polymer incorporated in No. 12 is PEG (molecular weight 200), and the amount added is 16.0 wt%. The water-soluble polymer incorporated in No. 13 is PEG (molecular weight 1000), and the amount added is 0.8 wt%. The water-soluble polymer incorporated in No. 14 is PEG (molecular weight 2000), and the amount added is 0.8 wt%. The water-soluble polymer incorporated in No. 15 is PEG (molecular weight 6000), and the amount added is 0.8 wt%. The water-soluble polymer included in No. 16 is hyaluronic acid, added at a concentration of 0.8 wt%. The water-soluble polymer used in No. 17 is guar gum, added at a concentration of 0.8 wt%. The water-soluble polymer included in No. 18 is xanthan gum, added at a concentration of 0.8 wt%. The water-soluble polymer used in No. 19 is carrageenan, added at a concentration of 0.8 wt%. The water-soluble polymers included in No. 20 are carrageenan and sodium polyacrylate, with a total addition amount of 0.8 wt%. The water-soluble polymer used in No. 21 is sodium alginate, added at a concentration of 0.8 wt%. The water-soluble polymer incorporated in No. 22 is alginic acid, added at a concentration of 0.8 wt%. The water-soluble polymers used in No. 23 are alginic acid + sodium polyacrylate, added at a concentration of 0.8 wt%. The water-soluble polymer used in No. 24 is sodium polyacrylate, added at a concentration of 0.8 wt%. The water-soluble polymer incorporated in No. 25 is carboxymethylcellulose, added at a concentration of 0.8 wt%. The water-soluble polymer used in No. 26 is methylcellulose, added at a concentration of 0.8 wt%.

[0053] The following can be confirmed from the measurement results shown in Figure 7. The effects of the present invention are realized when using water-soluble polymers having both hydrophilic and hydrophobic groups, such as PVA No. 2 to No. 5 and methylcellulose No. 26, and lubricity is greatly improved. Furthermore, in this state, the toughness of the lubricating layer is also greatly improved for each circulating fluid. As can be seen from No. 3, industrially used PVA is not completely saponified, so even fully saponified PVA has both hydrophilic and hydrophobic groups and exhibits the effects of the present invention on its own.

[0054] On the other hand, when using water-soluble polymers such as No. 6 to No. 22, and No. 24 and No. 25, which consist only of hydrophilic groups or only of hydrophobic groups (including hydrophilicity and hydrophobicity resulting from molecular arrangement, etc.), it is clearly confirmed that the effects of the present invention are not exhibited at all. In particular, when water-soluble polymers No. 6 to No. 22, and No. 24 and No. 25 are added, it can be confirmed that the lubricity is significantly reduced compared to when they are not added (No. 1). Furthermore, as can be seen from the results for No. 23, when No. 22 (having only hydrophobic groups) and No. 24 (having only hydrophilic groups), which do not exhibit the effects of the present invention on their own, are added together, the effects of the present invention are remarkably manifested.

[0055] In this specification, a water-soluble polymer is a polymer that dissolves in water, and includes not only those that dissolve on their own, such as PVA, but also those that exhibit water solubility when dissolved in a water-soluble solvent (such as a crosslinked product of PVA and a polysaccharide dissolved in it). For example, alginic acid No. 22 has only hydrophobic groups and is therefore insoluble in water on its own, but it becomes soluble in water when added together with PVA Nos. 2 to 5.

[0056] The effect of the present invention is that, by considering the type and material of the catheter used, and by blending multiple types of surfactants, water-soluble ionic compounds, and water-soluble polymers, the lubrication properties (including their relationship to the catheter's movement speed) and tendencies associated with the zeta potential can be further finely adjusted. This makes it possible to improve functionality or create circulating fluids specialized for specific purposes or conditions. Figure 8 shows an example in which measurements were taken using the same method as in Figure 6 with a circulating fluid (far right in Figure 8) created with the aim of keeping the reaction force applied to the catheter constant regardless of the catheter's movement speed. In this example, an anionic surfactant (0.2 wt%) and an amphoteric surfactant (0.12 wt%) were used in combination, along with PVA (0.32 wt%), alginic acid (0.08 wt%), and fructose (0.45 wt%) as water-soluble polymers. In addition, a pH buffer (0.02 wt%) was added to make the tendency of the zeta potential closer to that of living blood and to bring the characteristics exhibited by the catheter closer to those of human blood vessels.

[0057] Furthermore, the results in Figure 8 confirm that the effects of the present invention are not lost due to the inclusion of sugars. When PVA is added alone as a water-soluble polymer, when the circulating fluid containing it dries, the remaining PVA forms a film, which may clog or adhere to the inside of the vascular model or to equipment such as catheters and pumps, potentially hindering subsequent use. When sugars are present, no polymer film is formed upon drying, resulting in a fine powder, which allows for easy cleaning by wiping.

[0058] The circulating fluid's molecular bonding state and size can be altered by heating or cooling, thereby allowing for adjustments to its lubrication properties. For example, in a circulating fluid containing PVA, heating it at a predetermined temperature (e.g., 35°C) for a predetermined time (e.g., 2 minutes) removed turbidity, increased transparency, and significantly improved lubrication properties compared to before heating. Even after returning the circulating fluid, from which turbidity had been removed by heating, to room temperature (approximately 25°C), its high transparency and excellent lubricity were irreversibly maintained.

[0059] When using water-soluble polymers such as PVA, it is preferable to maintain the pH of the circulating fluid within a range from weakly basic to weakly acidic in order to reproduce an environment similar to that of blood. For this reason, pH buffering agents can be added to the circulating fluid as auxiliary agents. In particular, when an acidic circulating fluid with a pH below 5.0 was used, the hydrophilic coating covering the surface of the catheter quickly became inactive, resulting in adverse effects such as a significant decrease in the lubricity of the catheter.

[0060] According to our investigations, after bringing the circulating fluid of each example containing a water-soluble polymer into contact with the inner wall of the vascular model and the outer circumference of the catheter sheath, good lubrication was maintained between the vascular model and the catheter even when using other circulating fluids (for example, those containing only surfactants). This is because the circulating fluid of the examples forms a layer of water-soluble polymer material on at least the inner circumferential wall of the vascular model. In other words, it is believed that the circulating fluid in each embodiment forms some kind of lubricating layer on the surface of the silicone rubber and the resin material constituting the sheath, and that lubrication is obtained by maintaining this layer. Furthermore, metal ion chelating agents were effective in cleaning and removing the residual lubricating layer. Edetates and the like can be used as chelating agents.

[0061] When forming a blood vessel model with silicone rubber, if a large amount of unreacted parts remain in the siloxane molecules constituting the silicone rubber, the lubricating function of the present invention may not be fully expressed. Therefore, by promoting the reaction through heating or other means to reduce the unreacted parts, or by using a TMS agent (trimethylsilylation agent), chemically modifying the unreacted parts of the silicone rubber with functional groups such as hydroxyl groups, carboxyl groups, and amino groups, the effects of the present invention can be further enhanced.

[0062] Therefore, this invention can be extended as follows. (1) A lubricant that provides lubrication between a first member containing a crosslinked polymer material and a second member containing a crosslinked polymer material, A lubricant comprising water, a surfactant, a water-soluble ionic compound, a first water-soluble polymer having hydrophilic and hydrophobic groups, a mixture of a second water-soluble polymer having hydrophilic groups and a third polymer having hydrophobic groups, and one or more selected from the mixture of the first water-soluble polymer and the third polymer. Here, an example of the first component is a vascular model made of silicone rubber or urethane rubber, and an example of the second component is a catheter sheath made of polyethylene. This lubrication modifier is not limited to the combination of vascular models and catheters, but improves the lubricity between crosslinkable polymer materials. (2) The lubricant according to (1), wherein the surfactant includes an amphoteric surfactant. (3) The water-soluble polymer is a lubricant according to (1) or (2), comprising polyvinyl alcohol. (4) The lubricant according to (3), wherein the water-soluble polymer is a crosslinked product of polyvinyl alcohol and polysaccharide. (5) The lubricant described in (4), further containing monosaccharides. (6) The lubricant described in (1) further containing a pH adjuster.

[0063] Such lubricants have value as surface coating agents for catheters. In other words, (11) A lubricant applied to the surface of a catheter sheath, comprising water, a surfactant, a water-soluble ionic compound, and one or more selected from a first water-soluble polymer having both hydrophilic and hydrophobic groups, a mixture of a second water-soluble polymer having hydrophilic groups and a third polymer having hydrophobic groups, and the mixture of the first water-soluble polymer and the third polymer. (12) The lubricant according to (11), wherein the surfactant includes an amphoteric surfactant. (13) The water-soluble polymer comprises polyvinyl alcohol as described in (11) or (12). (14) The lubricant according to (13), wherein the water-soluble polymer is a crosslinked product of polyvinyl alcohol and polysaccharide. (15) The lubricant described in (14), further comprising monosaccharides. (16) The lubricant described in (11), further comprising a pH adjuster. A catheter comprising a membrane formed of one of the lubricants (17)(11)~(16).

[0064] The measuring device shown in Figure 1 is a newly created device for evaluating the lubricity between a vascular model and a catheter. The invention of this device can be understood as follows: (21) A device for evaluating the lubricity between a vascular model and a catheter, With the catheter inserted into the blood vessel model, a clip portion is provided to clip the blood vessel model via an elastic material, A fixing part for securing the clip part, A catheter drive unit that moves the catheter in the axial direction of the blood vessel model at a predetermined rhythm, A measuring device comprising: a resistance measuring unit for measuring the resistance applied to the catheter drive unit when moving the catheter. (22) The measuring device according to (21) wherein the elastic modulus of the elastic material is equal to the elastic modulus of human tissue. (23) The measuring device according to (22), wherein the elastic material is a silicone gel. (24) The measuring device according to any one of (21) to (23), wherein the catheter drive unit makes the movement speed of the catheter variable.

[0065] This invention is not limited in any way to the embodiments and examples described above. Various modifications that do not depart from the scope of the claims and are easily conceivable by those skilled in the art are also included in this invention. The following matters are disclosed below. (101) A circulating fluid for use in a catheter simulator, comprising one or more selected from a first water-soluble polymer having both hydrophilic and hydrophobic groups, a mixture of a second water-soluble polymer having hydrophilic groups and a third polymer having hydrophobic groups, and a mixture of the first water-soluble polymer and the third polymer. (102) The circulating fluid according to (101), wherein the amount of the water-soluble polymer is 0.5 to 8.0% by mass relative to the water component of the circulating fluid. (103) The circulating fluid according to (101), wherein the first water-soluble polymer is one or more selected from natural polymers such as PVA (polyvinyl alcohol), methylcellulose, protein, and starch, as well as synthetic polymers such as polyacrylic acid, polyacrylamide, polyethylene oxide, poly(vinylpyrrolidone), polyvinylamide, and polyamine. (104) The circulating fluid according to (101), wherein the first water-soluble polymer is PVA or methylcellulose. (105) The circulating fluid according to (104), wherein the first water-soluble polymer is PVA. (106) The circulating fluid according to (105), wherein the number-average molecular weight of the PVA is 500 to 2000, and its degree of saponification is 75 or higher. (107) The circulating fluid according to (105), further comprising a pH buffering agent. (108) The circulating fluid described in (105), further containing sugars. (109) The circulating fluid according to (108), wherein 50 to 200 parts by mass of sugars are added per 100 parts by mass of PVA. (110) The mixing ratio of the second water-soluble polymer and the third polymer in the mixture is: The circulating fluid described in (101) is in a 1:1 ratio. (111) The circulating fluid according to (101), wherein the second water-soluble polymer is sodium polyacrylate and the third polymer is alginic acid. (112) The circulating fluid described in (101), further comprising a surfactant and a water-soluble ionic compound. (113) The circulating fluid described in (110) further contains a pH buffer. (114) The circulating fluid according to (110), wherein the surfactant is an amphoteric surfactant alone, a cationic surfactant with an amphoteric surfactant added, or an anionic surfactant with an amphoteric surfactant added. (115) A lubricating modifier that is added to aqueous circulating fluids used in catheter simulators, A lubricity modifier comprising a first water-soluble polymer having both hydrophilic and hydrophobic groups, a mixture of a second water-soluble polymer having hydrophilic groups and a third polymer having hydrophobic groups, and one or more selected from the mixture of the first water-soluble polymer and the third polymer. (116) A first aqueous solution containing the lubricity modifier described in (113), A second aqueous solution containing a surfactant, A set of lubrication-modifying agents containing a third aqueous solution containing a water-soluble ionic compound. (117) (101) The step of circulating the circulating fluid described in the vascular model, A catheter simulation method comprising the step of inserting a catheter into the aforementioned vascular model. (118) The method according to (115), wherein, when the blood vessel model is made of silicone rubber, the step of chemically modifying the functional groups of the silicone rubber before circulating the circulating fluid is further included. (119) A cleaning method comprising removing the catheter described in (115) from the blood vessel model and then cleaning it with a cleaning solution containing a chelating agent. (120) An aqueous lubricity modifier that provides lubricity between a first member containing a crosslinked polymer material and a second member containing a crosslinked polymer material, A lubricity modifier comprising a first water-soluble polymer having both hydrophilic and hydrophobic groups, a mixture of a second water-soluble polymer having hydrophilic groups and a third polymer having hydrophobic groups, and one or more selected from the mixture of the first water-soluble polymer and the third polymer. (121) The lubricity modifier according to (118), wherein the first member is a vascular model and the second member is a catheter sheath. (122) water, Surfactants, Water-soluble ionic compounds, and An aqueous composition comprising: a first water-soluble polymer having both hydrophilic and hydrophobic groups; a mixture of a second water-soluble polymer having hydrophilic groups and a third polymer having hydrophobic groups; and one or more selected from the mixture of the first water-soluble polymer and the third polymer. (223) A water-based circulating fluid used in a catheter simulator equipped with a vascular model, comprising a first water-soluble polymer having both hydrophilic and hydrophobic groups, a surfactant, and a water-soluble ionic compound, wherein the first water-soluble polymer forms a lubricating layer on the inner surface of the vascular model by intricately intertwining its polymer chains. The first water-soluble polymer is polyvinyl alcohol, and the process involves preparing a stock solution of the circulating fluid, A step of heating the undiluted solution to increase its transparency, A method for producing a circulating fluid containing [the specified substance].

[0066] I dedicate this patent, which I have finally been able to file, to my father, Moritaka Ikeda, with heartfelt gratitude for his unwavering and kind support in every aspect of the development process, including the design, prototyping, and experimentation of measuring devices and methods. [Explanation of symbols]

[0067] 1 Catheter 5. Vascular Models 20 Measuring devices

Claims

1. A water-based circulating fluid used in a catheter simulator equipped with a blood vessel model, comprising a first water-soluble polymer having both hydrophilic and hydrophobic groups, wherein the polymer chains of the first water-soluble polymer are intricately intertwined on the inner circumferential surface of the blood vessel model to form a lubricating layer.

2. The circulating liquid according to claim 1, wherein the amount of the water-soluble polymer is 0.5 to 8.0% by mass relative to the water component of the circulating liquid.

3. The circulating fluid according to claim 1, wherein the first water-soluble polymer is PVA or methylcellulose.

4. The circulating fluid according to claim 3, wherein the first water-soluble polymer is PVA.

5. The circulating liquid according to claim 4, wherein the degree of polymerization of the PVA is 500 to 2000 and its degree of saponification is 75 or higher.

6. The circulating liquid according to claim 4, further comprising a pH buffering agent.

7. The circulating fluid according to claim 4, further comprising sugars.

8. The circulating liquid according to claim 7, wherein 50 to 200 parts by mass of sugars are blended with 100 parts by mass of PVA.

9. The circulating fluid according to claim 1, further comprising a surfactant and a water-soluble ionic compound.

10. The circulating liquid according to claim 9, further comprising a pH buffering agent.

11. The circulating fluid according to claim 9, wherein the surfactant is an amphoteric surfactant alone, a cationic surfactant with an amphoteric surfactant added, or an anionic surfactant with an amphoteric surfactant added, and the water-soluble ionic compound is a water-soluble metal salt or a water-soluble ammonium salt.

12. A lubricity modifier set for use in an aqueous circulating fluid used in a catheter simulator equipped with a vascular model, comprising a first water-soluble polymer having both hydrophilic and hydrophobic groups, wherein the first water-soluble polymer contains a first aqueous solution containing a lubricity modifier, the polymer chains of which become intricately intertwined on the inner surface of the vascular model to form a lubricating layer, A second aqueous solution containing a surfactant, A set of lubrication modifiers containing a third aqueous solution containing a water-soluble ionic compound.

13. The steps of circulating the circulating fluid described in claim 1 through a vascular model, A catheter simulation method comprising the step of inserting a catheter into the aforementioned vascular model.

14. The method according to claim 13, wherein, when the blood vessel model is made of silicone rubber, the method further includes the step of chemically modifying the functional groups of the silicone rubber before circulating the circulating fluid.

15. The method according to claim 13, wherein the catheter is removed from the blood vessel model and then washed with a washing solution containing a chelating agent.

16. An aqueous composition for use in a catheter simulator equipped with a blood vessel model, water, Surfactants, Water-soluble ionic compounds, and An aqueous composition comprising a first water-soluble polymer having both hydrophilic and hydrophobic groups, wherein the polymer chains of the first water-soluble polymer are intricately intertwined on the inner surface of the blood vessel model to form a lubricating layer.

17. A water-based circulating fluid used in a catheter simulator equipped with a vascular model, comprising a first water-soluble polymer having both hydrophilic and hydrophobic groups, a surfactant, and a water-soluble ionic compound, wherein the first water-soluble polymer forms a lubricating layer on the inner surface of the vascular model through the complex intertwining of its polymer chains. The first water-soluble polymer is polyvinyl alcohol. A circulating fluid in which the frictional properties of catheters and aneurysm embolization coils are differentiated and adjusted for the aforementioned vascular model.

18. A water-based circulating fluid used in a catheter simulator equipped with a vascular model, comprising a first water-soluble polymer having both hydrophilic and hydrophobic groups, a surfactant, and a water-soluble ionic compound, wherein the first water-soluble polymer forms a lubricating layer on the inner surface of the vascular model through the complex intertwining of its polymer chains. The first water-soluble polymer is polyvinyl alcohol. A circulating fluid that is always bubble-free.

19. The circulating fluid according to claim 11, wherein the concentration of the surfactant is 0.005 mmol / L or more and 100 mmol / L or less, and the concentration of the water-soluble metal salt is 1 mmol / L or more and 100 mmol / L or less.

20. The circulating fluid according to claim 11, wherein the water-soluble metal salt is one or more selected from alkali metal salts, alkaline earth metal salts, aluminum salts, and iron salts.

21. A water-based circulating fluid used in a catheter simulator equipped with a blood vessel model, comprising a first water-soluble polymer having both hydrophilic and hydrophobic groups, wherein the first water-soluble polymer is excluding protein-fatty acid complexes, and the polymer chains of the first water-soluble polymer are intricately intertwined on the inner surface of the blood vessel model to form a lubricating layer.

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