Improved medical grade tubing and methods for coupling same

Abstract: A medical grade tubing that includes a layer of ultra low density polyethylene that has been let down, or drawn down, in diameter approximately 10% to about 50% in an extrusion process and an inner layer of an RF responsive material, the tubing allowing for the selective connection of the tubing to another tubing using a sterile welding device.

Description: BACKGROUND OF THE INVENTION The present invention relates generally to medical products. More specifically, the present invention relates to medical grade tubing and methods of connecting same in a sterile manner. It is of course known to house medical products in containers. It is likewise known to store certain medical products, e.g., blood and blood components, in containers. It is likewise known to use tubing to: access the containers; allow for the mixing of products; and/or infuse the products into a patient. For example, it is known to collect blood products from a patient and store same in flexible plastic containers. It is also known to treat these medical products, e.g., centrifuge the blood, and combine the resultant product with other components. These products can then be infused into a patient. In order to allow one to access the container containing a medical product or fluid, either to further treat the product, combine it with another product, add a product to the container, or infuse the product into a patient, it is known to use flexible tubes. These tubes must be made from medical grade plastics, e.g., a plastic that is inert and will not contaminate the medical product so that it can be infused or used with a patient. For example, it is known to use polyvinyl chloride (PVC) to manufacture such tubing. At various times it may be desirable to connect one or more tubes together. Such connections preferably are made using a sterile process; otherwise, after the connection is made, it is necessary to re-sterilize the two tubes that have been connected. Thus, sterile connection devices have been developed. One such device is available from Baxter Healthcare Corporation, Biotech North America, Deerfield, Illinois under the name "SCD® 312 Sterile Tubing Welder". This connection device allows two tubes to be sterilely connected together. Briefly, the device utilizes a wafer (sealing head), that is heated to more than 260°C (500°F). The wafer welds two separate tubing segments together. Due to the process used, contaminants are destroyed at the welding site providing a new connection that is strong enough to withstand the rigors that the product may be subjected to, for example, with respect to a blood collection device- blood processing, infusing and collecting. In the blood collection arena, such a connection device can be used to add leukocyte filters to red cell units; pool blood products and prepare blood components using blood transfer packs; attach a sterile dock set to apheresis platelets collected with a blood cell separator; prepare aliquots for pediatric use; add different needles to sets; and other process, sample and related connection without comprising the products sterility or dating. Although the SCD® 312 Sterile Tubing Welder provides a sterile, safe, and efficient method of connecting tubes, due to its effectiveness any polyvinyl chloride tubing can be connected to any other tubing of comparable size. This may create potential issues in that any tube, even those tubes that are coupled to products that should not be connected to other products due to an incompatibility of the products, can be erroneously or improperly connected. WO-A-97/42020 discloses a method for fabricating flexible medical tubing. The method comprises orienting a tubing formed from a polymeric material along its longitudinal axis to reduce the diameter of the tubing. WO-A-98/00286 discloses a method for attaching a coextruded port tube to a medical grade container. Therefore, there is a need for an improved tubing that allows for the selective connection of a tubing to another tubing in a sterile connection device. SUMMARY OF THE INVENTION The present invention provides two medical grade tubes that are coupled together by a sterile connection comprising a first tubing which comprises a layer of a non-RF responsive material consisting of ultra low density polyethylene that has been let down, or drawn down in diameter by from 10% to 50% in an extrusion process, and an inner layer of an RF responsive material; and a second tubing that does not include polyvinyl chloride. The present invention also provides a method of connecting tubing. According to the invention the first tubing is connected to similar tubes in a sterile connection. The first tubing cannot be connected to a polyvinyl chloride tubing. Thus, the present invention allows for the selective sterile connection of the first tubing to only select other tubing. This, therefore, prevents the first tubing from being connected to a polyvinyl chloride tubing, preventing the connection of incompatible products or devices. To this end the first tubing comprises a layer of a non-RF responsive material consisting of ultra low density polyethylene that has been led down, or drawn down, in diameter by from 10% to 50% in an extrusion process and an inner layer of an RF active material. In an embodiment, the first tubing includes an outer layer of a polyvinyl chloride material. In an embodiment the ultra low density polyethylene is let down 50% in the extrusion process. In an embodiment, the inner layer of the first tubing is chosen from the group consisting of ethylene vinyl acetate, polyamide alloy, and polyvinyl chloride. In an embodiment, the first tubing is co-extruded. In an embodiment the inner layer of the first tube has a thickness of 0.025 mm (0.001 inches) to 0.25 mm (0.010 inches), the layer of a non-RF responsive material consisting of ultra low density polyethylene of the first tube has a thickness of 0.20 mm (0.008 inches) to 0.51 mm (0.020 inches) and the outer layer of the first tube has a thickness of 0.025 mm (0.001 inches) to 0.13 mm (0.005 inches). The present invention also provides a method for the selective sterile connection of medical grade tubing. This method comprising providing a first tubing as defined above which cannot be connected to a polyvinyl chloride tubing and welding the first tubing to a non-polyvinyl chloride containing tubing using a welding device. The first tube is so constructed and arranged that it cannot be sterile connected to a polyvinyl chloride tubing using a sterile connection device including a heat sealing device. An advantage of the present invention is that it allows for the selective connection of two tubes. An advantage of the first tubing is that it can be used as tubing that cannot be connected to a standard polyvinyl chloride tubing. Moreover, an advantage of the present invention is that it provides an improved method for connecting at least certain tubes and preventing the connection of standard PVC tubing. An advantage of the first tubing used in the present invention is that it is an improved tubing for use in a sterile connection device. Additional features and advantages of the present invention are described in, and will be apparent from, the Detailed Description of the Presently Preferred Embodiments and from the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figures 1A - 1C illustrate schematically a connection device for connecting two tubes in a sterile manner. Figure 2 illustrates a cross-sectional perspective view of an embodiment of the first tubing used in the present invention. Figure 3 illustrates a cross-sectional perspective view of another embodiment of the first tubing used in the present invention. DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS The present invention relates to two medical grade tubes that are coupled together and to methods for achieving this. As noted in the background of the invention, for a variety of reasons it may be necessary to connect two separate medical grade tubes to each other. As is also noted in the background of the invention, such a connection preferably should be done in a sterile manner. Such a connection may be desirable to add a device, such as a needle onto another tubing, connect two products, or allow the infusion of a product into a patient or a device. Referring generally to Figures 1A - 1C, a device 10 for the sterile connection of two tubes is illustrated. As illustrated, generally the device 10 includes two members 12 and 14, each including a channel 16 and 18 for holding a tube 20 and 22 respectively. As illustrated in Figure 1B, the members 12 and 14 can be moved in a parallel direction, opposite to each other. Accordingly, as illustrated in Figure 1A, tubes 20 and 22 are placed in each of the channels 16 and 18. A welding head 24 is then urged upwardly against and through the tubes 20 and 22. The welding head is heated to a temperature of approximately 260°C (500°F). Thus, the welding head thereby welds and separates the two tubes 20 and 22. At the same time that the welding head 24 passes through the tubes 20 and 22, the tubes are shifted because the channels 16 and 18 containing the tubings are moved in opposite directions. The welding head 24 is then lowered as a first end 30 of the second tube 22 is urged against a second end 32 of the first tube 20. This thus seals the two tubes together at a sterile connection 34. Such a device is commercially available from Baxter Healthcare Corporation, Biotech North America, Deerfield, Illinois, under the name SCD® 312 Sterile Tubing Welder. The tubing of the present invention is designed to selectively allow sterile connections using devices such as those set forth in Figure 1 including, but not limited to, the SCD® 312 Sterile Tubing Welder. Perhaps, the most commonly used medical grade tubing is polyvinyl chloride. Most medical grade tubing can be sterilely connected to polyvinyl chloride using a device such as that set forth in Figure 1. Unfortunately, a problem that can arise using a device 10 such as that illustrated in Figure 1, is that the sterile connection device 10 allows any PVC tubing to be connected to any other PVC tubing. Thus, even though a manufacturer of the product may not want certain products, and thereby certain tubing, connected to another product (tubing), because the devices or products to which the tubing is connected are incompatible, a sterile connection device would allow same to be coupled together. Pursuant to the present invention, a first tubing is provided that cannot be connected to polyvinyl chloride tubing using a sterile connection device or system. Instead, the tubing can only be connected to similar tubing in a device such as that illustrated in Figure 1. Thus, the first tubing allows the manufacturer to provide products that can only be coupled to each other and not inappropriately or inadvertently coupled to incompatible devices or products. Referring to Figure 2, an embodiment of the first tubing 40 used in the present invention is illustrated in cross-section. In the preferred embodiment the tubing 40 is co-extruded. The tubing 40 includes a first layer 42 of ultra low density polyethylene that has been let down, or drawn down, in diameter approximately 10 to about 50% in an extrusion process. In a preferred embodiment, the ultra low density polyethylene has been let down, or drawn down, in diameter 50% in the extrusion process. As used herein, a 50% let down, or drawn down, in diameter in an extrusion process means that the tubing was extruded with a much larger bushing such that during extrusion the tubing diameter was reduced to 50% of the bushing by means of take up. This thereby stretches the tubing by 50%. Ultra low density polyethylene is available from Dow Chemical Company, Exxon, and Mitsui Chemkal. Because ultra low density polyethylene is not a dielectric responsive material, and therefore cannot be RF welded, the first tubing includes a second layer 44. This second layer 44 is an RF active layer. The second layer 44 can be any material selected from the group consisting of ethylene vinyl acetate, polyamide alloy, or polyvinyl chloride. This layer is co-extruded onto the inner surface 42 of the tubing 40. Thus, the resultant tubing 40 can be RF heat sealed. Preferably the tubing 40 has a cross-sectional thickness of approximately 0.46 mm (0.018 inches) to about 0.56 mm (0.022 inches) with the thickness of the inner layer 42 being approximately 0.025 mm (0.001 inches) to about 0.25 mm (0.010 inches) and the thickness of the outer layer 44 being approximately 0.20 mm (0.008 inches) to about 0.51 mm (0.020 inches). Referring to Figure 3, a further embodiment of the first tubing used in the invention is illustrated wherein the tubing 50 includes a third layer 56 of polyvinyl chloride. To this end, the first layer 52 is a layer of ultra low density polyethylene let down, or drawn down, in diameter approximately 10 to about 50%, and most preferably 50% in the extrusion process. The second layer 54 is an RF responsive material chosen from the group consisting of ethylene vinyl acetate, polyamide alloy, and polyvinyl chloride. As previously noted, the third layer 56 is constructed from polyvinyl chloride and is co-extruded to the outer surface of the tubing using a tie layer 58 such as acid modified ethylene vinyl acetate. Preferably the tubing 50 has a cross-sectional thickness of approximately 0.46 mm (0.018 inches) to about 0.56 mm (0.022 inches) with the thickness of the inner layer 52 being approximately 0.025 mm (0.001 inches) to about 0.25 mm (0.010 inches) the thickness of the outer layer being approximately 0.025 mm (0.001 inches) to about 0.13 mm (0.005 inches), and the thickness of the middle layer is approximately 0.20 mm (0.008 inches) to about 0.51 mm (0.020 inches). An advantage of the tubing 50 is that although it cannot be sealed to a PVC tubing using a sterile connection device, such as 10 of Figure 1, it can be solvent bonded to a PVC part if needed due to the PVC layer 56. Each of the tubes 40 and 50 can be sealed to each other using a sterile connection system such as that illustrated in Figure 1. However, these tubes 40 and 50 cannot be sealed to a polyvinyl chloride tubing using such a device. In this regard, if one attempts to use to seal the tubing 40 and 50 to a polyvinyl chloride tubing using the device 10 of Figure 1, the seal will separate. This will prevent the tubes 40 and 50 from being sealed to a PVC tube. Thus, although the tubes 40 and 50 can be sterile welded to each other; they however cannot be sterile welded to polyvinyl chloride tubing. It should also be noted that the tubes 40 and 50 can be RF heat sealed. By way of example and not limitation, examples of the present invention will now be given. Tubing was extruded from the following plastic materials other than polyvinyl chloride: various ethylene vinyl acetates and various ultra low density polyethylenes. Each of the tubes was attempted to be sterile connected to each other using the SCD® 312 Sterile Tubing Welder. All of the preceding materials passed the test. After each of the tubes was welded to itself an attempt was made to pop open the seal of the tubing. It was found that only tubing made from Dow Chemical VP8770 ultra low density polyethylene material passed this test. Then an attempt was made to weld the tubing to a standard polyvinyl chloride tubing. The ultra low density polyethylene tubing would not weld to the polyvinyl chloride tubing.

Claims: Two medical grade tubes that are coupled together by a sterile connection comprising: a first tube which comprises a layer of non-RF responsive material consisting of ultra low density polyethylene that has been let down or drawn down in diameter by from 10% to 50% in an extrusion process, and an inner layer of an RF responsive material; and a second tube that does not include polyvinyl chloride. The two medical grade tubes of Claim 1 wherein the first tube includes an outer layer of polyvinyl chloride material. The two medical grade tubes of Claim 1 wherein the ultra low density polyethylene is let down, or drawn down, in diameter by 50% in the extrusion process. The two medical grade tubes of Claim 1 wherein the inner layer of the first tube is chosen from the group consisting of ethylene vinyl acetate, polyamide alloy, and polyvinyl chloride. The two medical grade tubes of Claim 1 wherein the first tube is co-extruded. The two medical grade tubes of Claim 2 wherein: the inner layer of the first tube has a thickness of from 0.025mm (0.001 inches) to 0.25mm (0.010 inches); the layer of a non-RF responsive material consisting of ultra low density polyethylene of the first tube has a thickness of from 0.20mm (0.008 inches) to 0.51mm (0.020 inches); and the outer layer of the first tube has a thickness of from 0.025mm (0.001 inches) to 0.10mm (0.004 inches). A method for the selective sterile connection of medical grade tubing which method comprises: providing a first medical grade tube as defined in Claim 1 and welding said first tube to a non-polyvinylchloride containing tube using a welding device. The method of Claim 7 wherein the first tube is as defined in any one of Claims 2 to 6.

Inventors: LING MICHAEL T K, LING, MICHAEL T. K.
Applicants: BAXTER INT, BAXTER INTERNATIONAL INC.
Application year: 1999
Main classification: B29C65
IPC codes: A61M36, B32B1, A61M39, B29C65