MEDICAL DEVICE FOR VISUALLY REPRESENTING AN INJECTION PRESSURE OF A FLUID

Description

FIELD OF APPLICATION AND STATE OF THE ART

[0001] The invention relates to a medical device for visually or optically displaying an injection pressure of a fluid, in particular medical fluid.

[0002] Many medical procedures cannot be performed without appropriate anesthesia. A distinction is made between general anesthesia and local anesthesia. The most important part of local anesthesia is regional anesthesia, particularly peripheral regional anesthesia.

[0003] In regional anesthesia, an anesthetic is administered near the nerve responsible for transmitting impulses from so-called nociceptors located in the area of a planned medical procedure. A special cannula is usually used for this purpose. If the cannula is inserted too close to or into the nerves, temporary or even permanent nerve damage can occur. Such nerve damage can also occur if the anesthetic injection pressure is too high. Therefore, both the positioning of the cannula and the injection pressure are crucial when performing (peripheral) regional anesthesia.

[0004] A device for visually displaying the pressure of a medical fluid, such as in particular an anesthetic, is known, for example, from WO 2003 / 101526 A1. The device is inserted between a syringe and a cannula. The device has a flow channel connecting the syringe to the cannula, which communicates with a pressure chamber. The pressure chamber is delimited by a diaphragm. If the injection pressure in the flow channel and thus in the pressure chamber increases, the diaphragm is deflected and presses an indicator pin against the force of a spring, so that this indicator pin is pushed out of the housing of the device to varying distances depending on the injection pressure prevailing in the flow channel. This allows the injection pressure to be visually monitored via a color ring coding of the indicator pin.

[0005] A device for limiting the injection pressure of a medical instrument for introducing a fluid is known from WO 2017 / 071833 A1. In this device, the injection pressure is limited by a valve. When a threshold pressure is reached, further fluid supply is interrupted. The counterforce required to close the valve is also provided by a spring.

[0006] Furthermore, WO 2018 / 170231 A1 discloses an injection syringe with a piezochromic pressure indicator which indicates the pressure of a fluid discharged from the injection syringe by means of a color change.

[0007] Relatively complex devices for measuring the pressure of medical fluids are known from the documents US 2013 / 0165904 A1 and US 2018 / 0064870 A1.

[0008] From US 2014 / 0069202 A1, a medical device in the form of a syringe with a syringe barrel is known, wherein the syringe barrel can contain a piezochromic material.

[0009] Conventional devices for visually displaying the injection pressure of fluids often have the disadvantage that they either have a very complex structure or have colored pressure indicators that either only respond at higher pressures and / or have a significantly delayed pressure response, which severely limits their use for medical, especially regional anesthetic, applications. TASK AND SOLUTION

[0010] The invention is based on the object of providing a device for visually or optically displaying an injection pressure of a fluid, in particular a medical fluid such as an anesthetic, which at least partially or even completely avoids the disadvantages described in the introduction in connection with conventional devices.

[0011] This object is achieved by a medical device according to claim 1. Preferred embodiments of the invention are the subject of the dependent claims. The wording of all claims is hereby incorporated into the description by express reference.

[0012] The invention relates to a medical device for the visual or optical representation of an injection pressure, in particular injection threshold pressure, of a fluid, preferably a medical fluid, in particular an anesthetic or an anesthetic-containing liquid.

[0013] The medical device comprises a fluid path for the fluid, i.e. a fluid path through which the fluid is transported, and a piezochromic material.

[0014] The invention is particularly characterized by the fact that the piezochromic material exhibits a piezochromic color change perceptible to the human eye when exposed to a pressure of < (spoken: less than) 100 bar.

[0015] For the purposes of the present invention, the term "injection pressure" is to be understood as a pressure, preferably a static pressure, which a fluid exerts on body cells, in particular nerve cells, and / or body tissue, in particular nerve tissue, and / or other body structures when it is injected into the body of a patient.

[0016] For the purposes of the present invention, the term "pressure" is to be understood as an absolute pressure, i.e. a pressure which is related to a pressure of zero which prevails in a vacuum, in particular in the universe.

[0017] The term "injection threshold pressure" is to be understood in the context of the present invention as a pressure threshold value, preferably a threshold value of a static pressure, the exceeding of which should be avoided as far as possible, preferably from a medical point of view, in particular from the point of view of cell damage, in particular nerve cell damage, and / or body tissue damage, in particular nerve tissue damage.

[0018] For the purposes of the present invention, the term "fluid" is to be understood as meaning a liquid, preferably a medical liquid, in particular an anesthetic or a liquid containing anesthetic.

[0019] For the purposes of the present invention, the term "piezochromic material" is understood to mean a material that changes its color when subjected to pressure.

[0020] The invention is based on the surprising discovery that a piezochromic material, which changes color when subjected to a pressure of < 100 bar, is suitable for the visual or optical representation of reaching or exceeding one or more injection threshold pressures of a fluid, preferably a medical fluid, such as an anesthetic. This is particularly advantageous when performing peripheral regional anesthesia. In this type of anesthesia, the anesthesiologist brings the cannula tip as close as possible to the relevant nerve, for example, using ultrasound guidance. The anesthesiologist then checks the correct position of the cannula tip by carefully increasing the force on the syringe plunger. If the cannula tip is directly on or even in the nerve, the initial injection pressure of the anesthetic generally rises to a value of > (pronounced: greater than) 15 psi (1,034 bar).The injection pressure is static or essentially static, as the anesthetic fluid flow is negligible. The static fluid pressure, which is consistent throughout the entire fluid path, can now be visualized using the device or piezochromic material according to the invention. This allows the anesthesiologist to adjust the position of the needle tip if necessary. Thus, the risk of nerve damage during regional anesthesia can be significantly reduced.

[0021] Advantageously, depending on the type and chemical composition of the piezochromic material, threshold pressures, i.e., pressure threshold values, whose exceedance may be medically hazardous, can be visually represented very precisely, i.e., without great fluctuation, and in particular reliably and reproducibly. For example, the device according to the invention can be used to visualize injection threshold pressures whose exceedance leads to damage to body cells, in particular nerve cells, and / or body tissues, in particular nerve tissue.

[0022] A further advantage is that the medical device according to the invention, thanks to the piezochromic material, exhibits a significantly faster pressure response than pressure indicators known from the prior art. The improved pressure sensitivity of the piezochromic material compared to conventional pressure indicators further optimizes the visualization and adherence to, in particular, medically relevant injection threshold pressures.

[0023] A further advantage of the invention is that the piezochromic material can also detect pressures that are of particular relevance for medical applications, especially in the field of regional anesthesia, preferably peripheral regional anesthesia.

[0024] It is also advantageous that the medical device according to the invention can have a significantly simpler structure than conventional devices. In particular, the medical device according to the invention can have fewer components than devices known from the prior art. Particularly preferably, the device according to the invention can have no movable, in particular no mechanically movable, and / or no electronic components, apart from a possible syringe plunger. This enables cheaper production of the medical device according to the invention. The medical device according to the invention can therefore preferably be designed as a single-use or disposable product, i.e. as a product intended for single use. Alternatively, the medical device according to the present invention can be designed as a reusable product, i.e. as a product intended for multiple uses.

[0025] Finally, it is advantageous that the medical device according to the invention can be provided with any form of connectors, such as Luer connectors, NRFit ®< connectors and the like.

[0026] In an embodiment of the invention, the piezochromic material exhibits a piezochromic color change perceptible to the human eye when exposed to a pressure of < (read: less than) 50 bar, in particular (read: less than) 10 bar, preferably (read: less than) 5 bar, particularly preferably from 1 bar to 3 bar. In particular, the pressure sensitivity of the piezochromic material disclosed in this paragraph advantageously contributes to preventing the exceeding of a medically critical injection threshold pressure and thus damage to body cells and / or body tissue, in particular nerve cells and / or nerve tissue.

[0027] In a further embodiment of the invention, the piezochromic material exhibits the piezochromic color change perceptible to the human eye within a period of < (spoken: less than) 5 s, in particular within a period of < (spoken: less than) 1 s. In particular, the piezochromic material can exhibit the piezochromic color change perceptible to the human eye within a period of 0 s, in particular > (spoken: greater than) 0 s, to 2 s, preferably within a period of 0 s, in particular > (spoken: greater than) 0 s, to 1 s. This makes it possible to achieve a quasi-immediate color change of the piezochromic material upon application of pressure. This advantageously also helps to avoid exceeding an injection threshold pressure that is questionable from a medical point of view.

[0028] In principle, the piezochromic material can exhibit a reversible or irreversible piezochromic color change. A reversible color change may be preferred, for example, if the medical device is to be used multiple times or if the fluid is to be injected at time intervals, i.e., portions of the fluid are to be injected sequentially. Alternatively, an irreversible color change of the piezochromic material may be preferred. Such a color change of the piezochromic material may be advantageous, for example, for verifying that certain injection pressures have not been exceeded in a medical application.

[0029] Furthermore, when subjected to pressure, the piezochromic material can exhibit a so-called bathochromic effect, i.e., a redshift or color deepening, i.e., a shift of its absorption spectrum into the longer-wavelength, lower-energy region of the electromagnetic spectrum. Alternatively, when subjected to pressure, the piezochromic material can exhibit a so-called hypsochromic effect, i.e., a blueshift, i.e., a shift of its absorption spectrum into the shorter-wavelength, higher-energy region of the electromagnetic spectrum.

[0030] Furthermore, the piezochromic material is preferably a sterilization-resistant material, in particular a material resistant to gas sterilization, preferably sterilization with ethylene oxide.

[0031] The piezochromic material preferably comprises a polymer and / or copolymer. Alternatively, the piezochromic material may be a polymer and / or copolymer.

[0032] For the purposes of the present invention, the term "copolymer" is understood to mean a polymer which has at least two different monomer units.

[0033] In a further embodiment of the invention, the piezochromic material comprises a matrix composed of at least one polymer and / or copolymer, at least one liquid crystal, and at least one optically active substance. The at least one optically active substance is preferably distributed throughout the matrix.

[0034] Furthermore, the at least one optically active substance is preferably a chiral substance or chirally optically active substance.

[0035] In principle, all known liquid crystals can be used as liquid crystals.

[0036] In a further embodiment of the invention, the at least one liquid crystal is selected from the group consisting of N-(p-ethoxybenzylidene)-pn-butylaniline, N-(p-methoxybenzylidene)-pn-butylaniline, 4-n-alkylbenzoic acid (4-alkylphenyl ester), benzoic acid cholesteryl ester, cholesterol, tolan, alkanoic acids, stilbene, azobenzene, 4-phenylcinnamic acid, p-terphenyl, 1,2-bisbenzoethylene and mixtures of at least two of the aforementioned liquid crystals.

[0037] In a further embodiment of the invention, the at least one optically active substance is selected from the group consisting of 4-(4-hexyloxybenzoyloxy)benzoate, 4-[[4-(hexoyl)benzoyl]oxy]-benzoic acid 2-octyl ester, cholesteryl derivatives and mixtures of at least two of the aforementioned optically active substances.

[0038] In a further embodiment of the invention, the polymer and / or copolymer of the piezochromic material is / are a polyacrylate, polymethacrylate, copolyacrylate, copolymethacrylate, or a mixture of at least two of the aforementioned polymers and / or copolymers. The copolyacrylates and / or copolymethacrylates are preferably composed of at least one monofunctional monomer and / or at least one multifunctional crosslinker.

[0039] In a further embodiment of the invention, the monofunctional monomer is selected from the group consisting of benzyl acrylate, benzyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, methoxyethyl acrylate, methoxyethyl methacrylate, octadecyl acrylate, octadecyl methacrylate and mixtures of at least two of the aforementioned monomers.

[0040] In a further embodiment, the crosslinker is selected from the group consisting of 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, 1,10-decanediol diacrylate, 1,10-decanediol dimethacrylate, bisphenol A glycerol-(1-glycerol)phenol diacrylate and mixtures of at least two of the aforementioned crosslinkers.

[0041] Preferably, the crosslinker and the monofunctional monomer have a weight ratio (crosslinker to monofunctional monomer) between 0.01 and 0.8, preferably between 0.1 and 0.6, particularly preferably between 0.2 and 0.4.

[0042] Furthermore, the at least one liquid crystal preferably has a proportion of up to 90 wt.%, in particular between 15 wt.% and 60 wt.%, preferably between 25 wt.% and 32 wt.%, based on the total weight of the piezochromic material or the matrix of the piezochromic material.

[0043] Furthermore, the at least one optically active substance preferably has a proportion of up to 10 wt.%, in particular between 0.1 wt.% and 2.5 wt.%, preferably between 0.15 wt.% and 0.55 wt.%, based on the total weight of the piezochromic material or the matrix of the piezochromic material.

[0044] The piezochromic material is preferably also in the form of an elastic and highly ordered system. The system preferably has a helical structure.

[0045] With regard to further features and advantages of the piezochromic material, reference is made to WO 2011 / 012315 A1, the disclosure content of which with regard to the piezochromic material described therein is incorporated into the present description by express reference.

[0046] In a further embodiment of the invention, the piezochromic material is contained in a wall of a housing surrounding the fluid path, i.e. in a housing wall surrounding the fluid path, of the medical device. The piezochromic material can be contained in only a single wall section of the housing wall of the medical device. Alternatively, it can be preferred for the piezochromic material to be contained in several wall sections of the housing wall of the medical device. The wall sections can be arranged in the longitudinal direction and / or transverse or circumferential direction of the medical device. In the case of a medical device with a cylindrical, in particular circular-cylindrical, housing, the wall sections can also be arranged radially. In particular, the wall sections can differ from one another with regard to the piezochromic material.This makes it particularly advantageous to make different injection pressures, in particular injection threshold pressures, visible visually.

[0047] In a further embodiment of the invention, the housing wall of the medical device has, preferably in the thickness direction of the housing wall, at least one multi-layer, in particular three-layer, wall section, i.e. only one multi-layer, in particular three-layer, wall section or several multi-layer, in particular three-layer, wall sections. Preferably, an intermediate layer of the at least one multi-layer wall section comprises the piezochromic material or consists of the piezochromic material. In particular, the intermediate layer can be composed of several intermediate layer sections, preferably arranged directly next to one another, in particular in the longitudinal or circumferential direction of the housing of the medical device. The intermediate layer sections preferably differ from one another with regard to the piezochromic material.This makes it particularly advantageous to visually visualize different injection pressures. The intermediate layer preferably has a layer thickness of 0 mm, in particular > (pronounced: greater than) 0 mm, to 1 mm, in particular 0 mm, in particular > (pronounced: greater than) 0 mm, to 0.6 mm, preferably 0 mm, in particular > (pronounced: greater than) 0 mm, to 0.2 mm.

[0048] In a further embodiment of the invention, the at least one multi-layer, in particular three-layer, wall section further comprises an inner layer which covers the intermediate layer on the inside, i.e. on a side facing the fluid path, preferably directly and in particular completely. Particularly preferably, the inner layer is in direct contact with the fluid path. The inner layer preferably comprises a biocompatible, i.e. medically acceptable, material or preferably consists of such a material. This advantageously protects the piezochromic material from direct contact with the fluid and thus prevents any impairment of the piezochromic material by the fluid or components thereof.The inner layer preferably has a layer thickness of 0 mm, in particular > (pronounced: greater than) 0 mm, to 1 mm, in particular 0 mm, in particular > (pronounced: greater than) 0 mm, to 0.3 mm, preferably 0 mm, in particular > (pronounced: greater than) 0 mm, to 0.1 mm. Such a layer thickness advantageously ensures that the pressure exerted by the fluid is transferred almost directly to the piezochromic material and thus the color change of the piezochromic material can be brought about reliably and reproducibly.

[0049] In a further embodiment of the invention, the biocompatible material is selected from the group consisting of polyethylene terephthalate (PET), polyetheretherketone (PEEK), polypropylene (PP), polyphenylsulfone (PPSU), polyoxymethylene (POM) and mixtures of at least two of the aforementioned biocompatible materials.

[0050] In a further embodiment of the invention, the at least one multi-layer, in particular three-layer, wall section further comprises an outer layer which covers the intermediate layer on the outside, i.e. on a side facing away from the fluid path, preferably directly and in particular completely. Particularly preferably, the outer layer forms part of the outside of the medical device, in particular of the housing of the medical device. Preferably, the outer layer comprises a transparent, i.e. translucent, material. Alternatively, the outer layer can preferably consist of such a material. This advantageously makes it possible to achieve a visual or optical representation of the color change of the piezochromic material. The outer layer can in particular be designed as a screen or display.

[0051] For the purposes of the present invention, the term "transparent material" or "light-permeable material" is understood to mean a material that is permeable to light with a wavelength of 380 nm to 780 nm.

[0052] In a further embodiment of the invention, the transparent material is selected from the group consisting of polycarbonate (PC), polymethyl methacrylate (PMMA), polyurethane (PU) and mixtures of at least two of the aforementioned transparent materials.

[0053] Particularly preferably, the at least one multi-layer, in particular three-layer, wall section of the housing wall of the medical device is constructed from the inside to the outside from an inner layer, intermediate layer and outer layer, as described in the previous paragraphs.

[0054] As already mentioned, the piezochromic material is preferably contained in a wall of a housing of the medical device. The housing can, in principle, have any conceivable shape suitable for forming or defining a fluid path through which the fluid can be transported. For example, the housing can have a prismatic shape, in particular a cube or cuboid shape, or a cylindrical shape, in particular a circular cylindrical shape.

[0055] The medical device, in particular the housing of the medical device, preferably has a first connector device at a distal end of the medical device, in particular the housing of the medical device, for connecting the medical device, in particular the housing of the medical device, to an injection tube. The term "distal end" refers to the end of the medical device, in particular the housing of the medical device, that is located remote from the center of the body of a user, in particular an anesthesiologist.

[0056] Furthermore, the medical device, in particular the housing of the medical device, preferably has a second connector device at a proximal end of the medical device, in particular the housing of the medical device, for connecting the medical device, in particular the housing of the medical device, to a syringe body. The term "proximal end" is understood to mean the end of the medical device, in particular the housing of the medical device, that is located toward the center of the body of a user, in particular anesthesiologist.

[0057] The connector devices described in the previous sections can be designed, for example, as Luer-Lock connectors, in particular as male Luer-Lock connectors, female Luer-Lock connectors, male Luer-Lock connector and female Luer-Lock connector or as NRFit ®< connectors.

[0058] Furthermore, the medical device is preferably resistant to sterilization, in particular resistant to gas sterilization, preferably sterilization with ethylene oxide. Further features and advantages of the invention emerge from the claims and from the following description of preferred embodiments with reference to figures and examples. The embodiments described below serve to further explain the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] The following is shown schematically in the figures: Fig. 1: an embodiment of a medical device according to the invention, Fig. 2: a cross-sectional view of a further embodiment of a medical device according to the invention, Fig. 3: a plan view of the Fig. 2illustrated embodiment of a medical device according to the invention, Fig. 4: a detailed view of a housing wall of a further embodiment of a medical device according to the invention, Fig. 5: a plan view of a housing wall of a further embodiment of a medical device according to the invention, Fig. 6: an embodiment of a medical device not according to the invention, Fig. 7: a further embodiment of a medical device not according to the invention, Fig. 8: a further embodiment of a medical device not according to the invention and Fig. 9: a further embodiment of a medical device not according to the invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0060] Fig. 1shows schematically an embodiment of a medical device 1 according to the invention for visually or optically displaying an injection pressure, in particular injection threshold pressure, of an anesthetic when performing a peripheral regional anesthesia.

[0061] The medical device 1 is connected between an injection tube 2 and a syringe 3. For this purpose, the medical device advantageously has a connector device 4 for connecting the medical device 1 to the injection tube 2 and a further connector device 5 for connecting the medical device 1 to the syringe 3. The connector devices 4 and 5 can each be designed as Luer-Lock connectors, for example.

[0062] The syringe 3 has a cavity (lumen) 6 filled with an anesthetic. A cannula 7 is attached to a distal end of the injection tube 2, i.e., an end located away from the center of the body of a user, in this case an anesthesiologist.

[0063] The medical device 1 has a fluid path 8 for the anesthetic and a piezochromic material. The piezochromic material preferably exhibits a piezochromic color change perceptible to the human eye when exposed to a pressure of <10 bar, preferably <5 bar, particularly preferably from 1 bar to 3 bar. The piezochromic material can in particular be a piezochromic plastic or a piezochromic composition. The piezochromic material preferably comprises a matrix composed of at least one polymer and / or copolymer, at least one liquid crystal, and at least one optically active substance, in particular a chirally optically active substance. The optically active substance is preferably distributed throughout the matrix.

[0064] The aforementioned polymer can be, for example, a cross-linked polymethacrylate. The aforementioned copolymer can be, for example, a cross-linked copolymethacrylate. The at least one liquid crystal can be, for example, a liquid crystal mixture of four different alkylcyanobiphenyl derivatives and one alkoxycyanobiphenyl derivative. The optically active substance can be, for example, substance S-811, i.e., 4-(4-hexyloxybenzoyloxy)benzoate, cholesteryl derivatives, and / or mixtures thereof.

[0065] To perform peripheral regional anesthesia, the tip 9 of the cannula 7 is brought, for example under ultrasound control, as close as possible to a nerve 11 located in a peripheral tissue area 10. The nerve 11 is in the Fig. 1shown in cross-section. The anesthesiologist checks the correct position of the cannula tip 9 by carefully increasing the force on a piston 12 of the syringe 3. If the tip 9 of the cannula 7 is located directly on or even in the nerve 11, the opening injection pressure, which is in principle static, increases to a defined value, usually to a value greater than 1.034 bar (> 15 psi). The static pressure of the anesthetic, which is the same throughout the fluid path 8 of the medical device 1, can now be made optically visible via the piezochromic material of the medical device 1. This is achieved by the fluid path 8, which runs through the medical device 1, being fixed to a housing wall 13, ieis guided past a wall 13 of a housing 14 of the medical device 1, wherein the housing wall 13 has at least one multi-layer, in particular three-layer, wall section 15 with the piezochromic material in its thickness direction. The wall section 15 preferably has an intermediate layer which is coated with an inner layer on a side facing the fluid path 8 and with an outer layer on a side facing away from the fluid path 8. The intermediate layer preferably comprises the piezochromic material or consists of the piezochromic material. The inner layer preferably comprises a biocompatible material, preferably for protecting the piezochromic material from the fluid, or consists of such a material. The biocompatible material can be, for example, polyethylene terephthalate, polyetheretherketone, polypropylene, polyphenylsulfone or polyoxymethylene.The outer layer preferably comprises or consists of a transparent material. The transparent material can be, for example, polycarbonate, polymethyl methacrylate, or polyurethane. The inner layer is expediently in direct contact with the fluid path 8 of the medical device 1, whereas the outer layer expediently forms part of the exterior of the housing 14 of the medical device 1. The outer layer can be designed, in particular, as a screen or display.

[0066] When the injection pressure is increased to a defined value dependent on the composition of the piezochromic material, the piezochromic material changes color. The color change can be reversible or irreversible. Advantageously, the threshold pressure of the injection pressure can be adjusted very precisely and, in particular, reproducibly via the composition of the piezochromic material. In this way, reaching or exceeding a defined pressure can be visually visualized. Due to the aforementioned transparent outer layer, the color change of the piezochromic material is visible from the outside. This allows the anesthesiologist to recognize that they have positioned the cannula tip 9 either too close to or even in the nerve to be blocked, and can correct the position of the cannula tip 9 accordingly. This can advantageously prevent damage to the nerve 11.

[0067] Fig. 2shows schematically a cross-sectional view of a further embodiment of a medical device 1 according to the invention for visually or optically displaying an injection pressure, in particular injection threshold pressure, of a fluid, such as an anesthetic or an anesthetic-containing liquid.

[0068] The medical device 1 has a fluid path 8, which is surrounded by a housing wall 13, i.e. a wall 13 of a housing 14 of the medical device 1. The wall 11 has a wall section 15. The wall section 15 has a three-layer structure consisting of an inner layer 15a, an intermediate layer 15b, and an outer layer 15c. The intermediate layer 15b has a piezochromic material or consists of such a material. The inner layer 15a has a biocompatible material for protecting the piezochromic material from direct contact with the fluid or consists of such a material. The outer layer 15c has a transparent material or consists of such a material. Regarding further features and advantages of the piezochromic material, biocompatible material, and transparent material, reference is made to the previous description, in particular to the information in the description of the figures regarding Fig. 1mentioned features and advantages.

[0069] The inner layer 15a covers the intermediate layer 15b, preferably directly, on a side facing the fluid path 8. The inner layer 15a is preferably in direct contact with the fluid path 8. In contrast, the outer layer 15c covers the intermediate layer 15b, preferably directly, on a side facing away from the fluid path 8. The outer layer 15c preferably forms part of the outer side of the housing 14 of the medical device 1.

[0070] The housing 14 of the medical device 1 can further comprise, particularly in the region of the wall section 15, a reinforcement, particularly a reinforcing rib 16. Furthermore, the medical device 1 can comprise a web 17 formed on the inside in the direction of the wall section 15. The web 17 is preferably part of a part 18 of the housing 14 arranged opposite the wall section 15. The web 17 advantageously prevents the formation of air bubbles during the injection of the fluid and directs the fluid flow directly past the wall section 15 and thus the piezochromic material located therein. Furthermore, this advantageously enables a reduction in the dead space volume.

[0071] For further information on the functionality of Fig. 2 schematically shown medical device 1 is based entirely on the previous description, in particular on the description of the figures for Fig. 1, is referred to. The statements made therein apply mutatis mutandis.

[0072] Fig. 3 shows a schematic plan view of the Fig. 2 illustrated embodiment of a medical device 1 according to the invention.

[0073] A color change of the piezochromic material, and thus the reaching or exceeding of an injection threshold pressure during fluid injection, is visually detectable via the transparent outer layer 15c located on the outside of the housing 14. If necessary, an anesthesiologist can correct the position of a cannula tip, particularly when performing a peripheral regional anesthesia procedure.

[0074] Fig. 4shows schematically the detailed view of a housing wall 13 of a further embodiment of a medical device according to the invention for the visual or optical representation of an injection pressure, in particular injection threshold pressure, of a fluid, such as an anesthetic or an anesthetic-containing liquid.

[0075] The housing wall 13 has a wall section 15. This has a three-layer structure in the thickness direction of the housing wall 13, consisting of an inner layer 15a, an intermediate layer 15b, and an outer layer 15c. The intermediate layer 15b consists of several intermediate layer sections, which are arranged in the longitudinal direction of the housing wall, preferably directly next to one another. Preferably, the intermediate layer sections each have a different piezochromic material or each consist of a different piezochromic material. This advantageously allows different injection threshold pressures to be visualized. For example, the intermediate layer 15b, as shown in Fig. 4shown, consist of three such intermediate layer sections 15b 1, 15b 2 and 15b 3. For example, the piezochromic materials for the intermediate layer sections 15b 1, 15b 2 and 15b 3 can be selected such that the piezochromic material of the intermediate layer section 15b 1 shows a color change when subjected to a pressure ≥ 0.69 bar (≥ 10 psi), the piezochromic material of the intermediate layer section 15b 2 shows a color change when subjected to a pressure ≥ 1.03 bar (≥ 15 psi) and the piezochromic material of the intermediate layer section 15b 3 shows a color change when subjected to a pressure ≥ 1.38 bar (≥ 20 psi). Regarding other suitable piezochromic materials, reference is made to the information already provided in the previous description, in particular in the description of the figures for Fig. 1 , mentioned piezochromic materials.

[0076] On a side facing a fluid path, the intermediate layer 15b is covered by the inner layer 15a, preferably directly and completely. Preferably, the inner layer 15a is in direct contact with the fluid path. The inner layer 15a comprises a biocompatible material to protect the piezochromic materials of the intermediate layer 15b from direct contact with a fluid conveyed through the fluid path, or consists of such a material. Regarding suitable biocompatible materials, reference is made to the information already provided in the previous description, in particular in the description of the figures. Fig. 1 , mentioned biocompatible materials.

[0077] The outer layer 15c preferably covers the intermediate layer 15b on a side facing away from a fluid path, preferably directly and completely. The outer layer 15c preferably forms part of the exterior of the housing 14 of the medical device 1. The inner layer 15c comprises a transparent material or consists of such a material. This makes a color change in the piezochromic materials visually detectable by a user, in particular anesthesiologist. The outer layer can be designed, in particular, as a screen or display.

[0078] Regarding suitable transparent materials, reference is made to the information already provided in the previous description, in particular in the description of the figures for Fig. 1 , reference is made to the transparent materials mentioned.

[0079] Fig. 5 shows schematically a plan view of a housing wall of a further embodiment of a medical device 1 according to the invention.

[0080] The medical device 1 comprises a housing 14 with a housing wall 13. The housing wall 13 comprises a wall section 15 which is wider in the thickness direction of the housing wall than the remaining housing wall. The wall section 15 has the Fig. 4 The structure described above can be used to visualize the color changes caused by the piezochromic materials of the intermediate layer sections 15b 1, 15b 2, and 15b 3 when subjected to different pressures via the outer layer 15c, which can be designed in particular as a screen or display.

[0081] Fig. 6 shows schematically an embodiment of a medical device 1 not according to the invention for visually or optically displaying an injection pressure, in particular injection threshold pressure, of a fluid, such as an anesthetic or an anesthetic-containing liquid.

[0082] The medical device 1 is designed as a syringe with a syringe body 19 having a preferably conical or cylindrical outlet nozzle 21. The syringe body 19 is preferably cylindrical, in particular circularly cylindrical. The medical device 1 has a fluid path 8 formed by both the cavity of the syringe body 19 and the cavity of the outlet nozzle 21.

[0083] Furthermore, the syringe body 19 has a casing wall 13 with a wall section 15. The wall section 15 has a three-layer structure in the thickness direction of the casing wall, consisting of an inner layer, an intermediate layer, and an outer layer. The inner layer covers the intermediate layer on a side facing the fluid path 8, while the outer layer covers the intermediate layer on a side facing away from the fluid path 8. The inner layer is preferably in direct contact with the fluid path 8. The outer layer preferably forms part of the outer side of the syringe body 19. The intermediate layer comprises a piezochromic material or consists of a piezochromic material. The inner layer comprises a biocompatible material for protecting the piezochromic material from direct contact with the fluid or consists of such a biocompatible material. The outer layer comprises a transparent material or consists of a transparent material.With regard to suitable piezochromic materials, biocompatible materials and transparent materials as well as the functioning of the medical device 1, reference is made to the previous description, in particular to the description of the figures. Fig. 1 , reference is made.

[0084] Fig. 7 shows schematically a further embodiment of a medical device 1 not according to the invention for visually or optically displaying an injection pressure, in particular injection threshold pressure, of a fluid, such as an anesthetic or an anesthetic-containing liquid.

[0085] The medical device 1 is (also) designed as a syringe with a syringe body 19. The syringe body 19 is preferably cylindrical, in particular circular-cylindrical. The medical device 1 has a fluid path 8, which is formed by both the cavity of the syringe body 19 and the cavity of the outlet nozzle 21.

[0086] Furthermore, the syringe body 19 has an end wall 13 with a three-layer structure consisting of an inner layer, an intermediate layer, and an outer layer. The end wall surrounds an outlet opening 20, which opens into a conical or cylindrical outlet nozzle 21 of the syringe body 19.

[0087] For further features and benefits as well as further functionality of the Fig. 7shown medical device, in particular with regard to the aforementioned intermediate layer, inner layer and outer layer, is based entirely on the previous description, in particular on the figure descriptions of the Fig. 1 and 6 , reference is made.

[0088] Fig. 8 shows a further embodiment of a medical device 1 not according to the invention for visually or optically displaying an injection pressure, in particular injection threshold pressure, of a fluid, such as an anesthetic or an anesthetic-containing liquid.

[0089] The medical device 1 is (also) designed as a syringe and comprises a syringe body 19 with a preferably conical or cylindrical outlet nozzle 21 and a syringe plunger 22. The syringe body 19 is preferably cylindrical, in particular circular-cylindrical. The syringe plunger 22 comprises a rod 23, a head 24, and a plunger 25. The medical device 1 has a fluid path 8, which is formed by both the cavity of the syringe body 19 and the cavity of the outlet nozzle 21.

[0090] The outlet nozzle 21 has a branch 26 with a closed end 15. The closed end 15 thus forms a branched or branched wall section of the syringe body 19.

[0091] Preferably, the closed end or the branched or branched wall section 15 has a three-layer structure consisting of an inner layer 15a, intermediate layer 15b and outer layer 15c.

[0092] For further features and benefits as well as further functionality of the Fig. 8 shown medical device, in particular with regard to the aforementioned intermediate layer, inner layer and outer layer, is based entirely on the previous description, in particular on the figure descriptions of the Fig. 1 and 6 , reference is made.

[0093] Fig. 9 shows a further embodiment of a medical device 1 not according to the invention for visually or optically displaying an injection pressure, in particular injection threshold pressure, of a fluid, such as an anesthetic or an anesthetic-containing liquid.

[0094] The medical device 1 is (also) designed as a syringe and has a syringe body 19 with a preferably conical or cylindrical outlet nozzle 21 and a syringe plunger 22 with a rod 23, a head 24 and a plunger 25. The medical device 1 has a fluid path 8 which is formed by both the cavity of the syringe body 19 and the cavity of the outlet nozzle 21.

[0095] The plunger 25 of the syringe plunger 22 has a layer 25b covered by a layer 25a, with the layer 25a forming part of the outer surface of the plunger 25. The layer 25b comprises or consists of a piezochromic material. The layer 25a comprises or consists of a transparent material. In this way, a color change of the piezochromic material can be visualized for a user, in particular a physician.

[0096] For further features and benefits as well as further functionality of the Fig. 8 The medical device shown, in particular with regard to the aforementioned piezochromic material and the aforementioned transparent material, is based entirely on the previous description, in particular on the figure descriptions of the Fig. 1 and 6 , reference is made. EXAMPLE PART 1. Production of a piezochromic material according to the present invention (including a correspondingly constructed film) 1.1 Preparation of a mixture of a liquid crystal and a chirally optically active substance

[0097] The optically active substance S-811 was added to a liquid crystal mixture E5 (a mixture consisting of four alkylcyanobiphenyl derivatives and one alkoxycyanobiphenyl derivative) at a weight fraction of 22%. The mixture was heated to 58 °C above the clearing point of the E5 component and then cooled to room temperature. 1.2 Preparation of a mixture of a monofunctional methacrylate monomer and a crosslinker

[0098] 34 wt.% DDA was added to the monomer benzyl methacrylate. The mixture was then heated to 60 °C for 25 min.

[0099] The mixtures prepared according to steps 1.1 and 1.2 were mixed in a ratio of 1:2.4 at a temperature between 50°C and 55°C. Finally, 0.2 wt.% of the polymerization initiator Genocure LTM was added. The piezochromic material was mounted with a layer thickness of 25 µm between two 15 µm thick polypropylene films coated with polyamide (less than 1 µm) and polymerized for 15 minutes under UV light. The result was a red-reflecting film that was easily movable and flexible. When the pressure was increased by 0.4 bar, it became a film that reflected green to the eye. When the pressure was increased again by 0.7 bar, the color turned blue. The process was reversible. The color change of the film occurred in less than 1 s. 2. Production of another piezochromic material according to the present invention (including a correspondingly constructed film) 2.1 Preparation of a mixture of a liquid crystal and a chirally optically active substance

[0100] The optically active substance cholesteryl oleyl carbonate was doped into the liquid crystal EBBA at 27 wt.%. The mixture was heated to 52 °C above the clearing point of EBBA. 2.2 Preparation of a mixture of a monofunctional acrylate monomer and a crosslinker

[0101] 28 wt.% of the crosslinker polyethylene glycol diacrylate, M70, was doped to the monomer octadil acrylate, and the mixture was heated to 55 °C.

[0102] The mixtures prepared according to 2.1 and 2.2 were mixed in a ratio of 1:1.9 at a temperature between 45 °C and 50 °C. Locerin (BASF) was used as the polymerization initiator at 0.45%. The piezochromic material was mounted with a layer thickness of 30 µm between two 12 µm-thick Zeonor films. Both Zeonor films were coated with a maleic anhydride-styrene copolymer alignment layer (< 1 µm). The system was polymerized under UV light for 20 minutes. The Zeonor films were then easily removed. The result was a 30 µm-thick piezochromic layer. With a pressure increase of 0.8 bar, it changed color from red to blue in less than 1 s.

Claims

1. A medical device for visually displaying an injection pressure of a fluid, wherein the device comprises a fluid path for the fluid and a piezochromic material which exhibits a piezochromic color change perceptible to the human eye when exposed to a pressure of < 100 bar, characterized in that the medical device comprises a first connector mechanism for connecting the medical device to an injection tube and a second connector mechanism for connecting the medical device to a syringe body.

2. The medical device as claimed in claim 1, characterized in that the piezochromic material exhibits a piezochromic color change perceptible to the human eye when exposed to a pressure of < 50 bar, in particular < 10 bar, preferably < 5 bar, particularly preferably from 1 bar to 3 bar.

3. The medical device as claimed in claim 1 or 2, characterized in that the piezochromic material exhibits the piezochromic color change within a period of < 1 s.

4. The medical device as claimed in any of the preceding claims, characterized in that the piezochromic material comprises a matrix composed of at least one polymer and / or copolymer, at least one liquid crystal and at least one optically active substance, wherein the optically active substance is distributed in the matrix.

5. The medical device as claimed in claim 4, characterized in that the at least one liquid crystal is selected from the group consisting of N-(p-ethoxybenzylidene)-p-n-butylaniline, N-(p-methoxybenzylidene)-p-n-butylaniline, 4-alkylphenyl 4-N-alkylbenzoate, cholesteryl benzoate, cholesterol, tolan, alkanoic acids, stilbene, azobenzene, 4-phenylcinnamic acid, p-terphenyl, 1,2-bisbenzoethylene, mixtures of alkylcyanobiphenyls and alkoxycyanobiphenyls, and mixtures of at least two of the aforementioned liquid crystals.

6. The medical device as claimed in claim 4 or 5, characterized in that the at least one optically active substance is selected from the group consisting of 2-octyl 4-[[4-(hexoyl)benzoyl]oxy]benzoate, cholesteryl derivatives and mixtures thereof.

7. The medical device as claimed in any of claims 4 to 6, characterized in that the polymer and / or copolymer is a poly(meth)acrylate or a copoly(meth)acrylate that has preferably been synthesized from at least one monofunctional monomer and / or at least one multifunctional crosslinker.

8. The medical device as claimed in claim 7, characterized in that the monomer is selected from the group consisting of benzyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, methoxyethyl (meth)acrylate, octadecyl (meth)acrylate and mixtures of at least two of the aforementioned monomers and / or the crosslinker is selected from the group consisting of 1,4-butanediol di(meth)acrylate, polyethylene glycol diacrylate, polyethylene glycol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, bisphenol A glycerolate (1 glycerol / phenol) diacrylate and mixtures of at least two of the aforementioned crosslinkers.

9. The medical device as claimed in any of the preceding claims, characterized in that the piezochromic material is contained in a housing wall of the medical device that surrounds the fluid path.

10. The medical device as claimed in claim 9, characterized in that the housing wall comprises at least one multilayer wall section, wherein an intermediate layer of the at least one multilayer wall section comprises the piezochromic material or consists of the piezochromic material.

11. The medical device as claimed in claim 10, characterized in that the at least one multilayer wall section also comprises an inner layer which covers the intermediate layer on a side facing the fluid path and which comprises a biocompatible material or consists of such a material.

12. The medical device as claimed in claim 11, characterized in that the biocompatible material is selected from the group consisting of polyethylene terephthalate, polyetheretherketone, polypropylene, polyphenylsulfone, polyoxymethylene and mixtures of at least two of the aforementioned biocompatible materials.

13. The medical device as claimed in any of claims 10 to 12, characterized in that the at least one multilayer wall section also comprises an outer layer which covers the intermediate layer on a side facing away from the fluid path and which comprises a transparent material or consists of a transparent material.

14. The medical device as claimed in claim 13, characterized in that the transparent material is selected from the group consisting of polycarbonate, polymethyl methacrylate, polyurethane and mixtures of at least two of the aforementioned transparent materials.