WO2001026719A1

WO2001026719A1 - Pressure tolerant parenteral fluid and blood container for a warming cassette

Info

Publication number: WO2001026719A1
Application number: PCT/US2000/002630
Authority: WO
Inventors: Scott D. Augustine; Randall Charles Arnold; Keith Jay Leland
Original assignee: Augustine Medical, Inc.
Priority date: 1999-10-08
Filing date: 2000-02-02
Publication date: 2001-04-19
Also published as: AU2750600A

Abstract

A fluid container for use in a warming cassette of a fluid warming system includes two multilayered sheets joined to form a fluid path therebetween. Each sheet of the fluid container includes an outside structural layer and an inside bonding layer. The structural layers have a low coefficient of friction, so that the cassette easily slides into a warming unit. The structural layers are thin enough to transfer heat efficiently, yet strong enough to impart structural integrity to the fluid container. The inside layers have thermo-sealable properties to permit the formation of the fluid channel by heat sealing at relatively low temperatures.

Description

PRESSURE TOLERANT PARENTERAL FLUID AND BLOOD CONTAINER FOR A WARMING CASSETTE

BACKGROUND OF THE INVENTION This invention is generally related to parenteral fluid warmers and, more particularly, to a multi-layered parenteral fluid container for use in a warming cassette that is received in a warming device.

Plastic films have been used to make heat exchanger cassettes for parenteral fluid and blood warmers. Typically, two sheets of such film are joined to form a container with a fluid channel between the sheets. A warming cassette incorporates such a fluid container with other elements that impart structural support to the container and provide means for mating the container to a warming device. In use, the cassette is placed between the heated metal plates of a warming device and, as fluid flows through the channel in the container, it is warmed by heat conducted from the heated plates.

Specifics of a cassette with an integral frame structure capable of supporting the fluid container are discussed in co-pending patent application

09/415 405 Serial No. , entitled "INTRAVENOUS FLUID WARMING CASSETTE

WITH STIFFENING MEMBER AND INTEGRAL HANDLE", invented by Augustine et al„ filed on Oct . 8 ,. 1999

The material of a plastic film used in manufacturing a fluid container for a cassette is usually polyvinyl chloride (PVC), polyethylene or polypropylene. The film is a single layer of such material (a monolayer). The advantage of monolayer construction is that the film is very inexpensive and readily available. However, it is desirable that the film perform a number of functions. Film characteristics that are optimized to support one function may require a trade-off of another function.

Consider first the ability of monolayer sheets to be joined by thermo- sealing, which is a particularly desirable joining technique that is adaptable to high volume, web-based manufacture. Thermo-sealability is usually optimized when the film material has a low melting point. In fact, most of the inexpensive and common plastic film materials have a low melting point. However, simple heat sealing with a heated platen melts the plastic film to the heated platen, destroying the film and fouling the platen. Therefore, to use low melting point plastic films for the manufacture of parenteral fluid containers, the films require resealing with radio frequency (RF), ultrasonic (US) welding, or other additional manufacturing steps and equipment, rather than relying on faster, cheaper, and simpler heat sealing methods.

Nevertheless, when monolayer plastics are thermo-sealed, a strong bond is created between the sheets. However, at the edge of the bond, the melted plastic material is frequently thinned by the thermo-sealing process. The plastic film which is thinned at the edge of the seal may be weakened. When the container is pressurized by rapid infusion of fluid, the pressure in the container can be as high as 30 psi. In such cases, a seal with a weak bond can rupture, creating a leak. Pressure tolerance is especially critical when the cassette is inadvertently, or purposely, inserted only partially into the warming device, leaving some of the fluid channel unsupported by the metal plates of the warmer. In these instances, fluid containers have been known to rupture when pressurized.

A monolayer of low-melt point plastic film can be made relatively thick (greater than 8 mil) in order to make the fluid container strong enough to withstand pressurization of the fluid contained within it. When used to conduct heat from the plates of the warming device to the fluid channel of a container, however, these thicker, pressure tolerant, plastic films exhibit high thermal resistance. In fact, the thicker plastic films are very effective thermal insulators, preventing efficient heat transfer to the fluid. High melt-point plastic films are frequently stronger and, therefore, may be a thinner material. However, most of the stronger, harder plastic films are generally difficult to join using thermo- sealing.

Another desirable characteristic of container sheet material is a low coefficient of friction to support easy, sliding travel of a cassette between the plates of a warming device. In this regard, the common, lower melting point materials, such as PVC, are generally soft and flexible. However, these low melting point plastics tend to be relatively "sticky" to the touch, especially when heated. They have a high coefficient of friction and can stick to the metal plates of a warming device, making insertion and removal of a cassette much more difficult. Therefore, to insure that a cassette can easily slide into the narrow gap between the heated metal plates of a warming device, a fluid container made with a harder plastic film, having a low coefficient of friction, would seem to be indicated. However, as previously mentioned, the stronger, harder plastic films generally do not thermo-seal very well.

Consequently, it appears that all the desirable characteristics of a warming cassette cannot be satisfied through the use of a monolayer sheet of a plastic film material. Thus, there are significant problems that need to be solved in order to optimize the materials, construction, and operation of parenteral fluid containers for warming cassettes.

It would be advantageous if the film material for a parenteral fluid container for a warming cassette could be thermo-sealable for a strong, reliable seal and for fast, inexpensive, web manufacturing.

It would be advantageous if the material had a low coefficient of friction even when warm, to support easy removal and insertion between the heated plates of a warming device. It would be especially advantageous if the material had all of the above-mentioned favorable characteristics.

It would also be advantageous if a thin layer of the film material was strong enough to withstand high inflation pressures and resist thinning at the edges of the thermo-seals.

SUMMARY OF THE INVENTION

Accordingly, a parenteral fluid or blood container for a warming cassette used in a parenteral fluid warming system is provided. The fluid container comprises a first sheet including a plurality of layers and a second sheet including a plurality of layers. The first sheet is joined to the second sheet to form a fluid container with a fluid channel. When joined with other elements to form a warming cassette, the fluid container's fluid channel conducts fluid between the sheets, while the sheets contact a heat source and conduct heat to warm the fluid as it flows through the channel.

The first sheet includes at least a first layer and a second layer in a laminated structure, while the second sheet includes at least a third layer and a fourth layer in a laminated structure. Preferably, the first and third layers are flexible films formed from a first material characterized by a low coefficient of friction and a first melting point. The second and fourth layers are formed from a second material having a second melting point which is lower than the first melting point. This permits joinder of the sheets by thermo-bonding the second and fourth layers at a temperature that melts the second material of these layers, without melting the first material of the first and third layers. The second layer is joined to the fourth layer to form the fluid channel between the first and second sheets.

The first material can be selected from the group of materials consisting of polyester, polyamide, polyethylene glycol terephthalate, metal foils, and ionomer resins, while the second material can be selected from the group of materials consisting of polyolefin, polyethylene, polypropylene, polyvinyl chloride (PVC), polyurethane, and ethyl vinyl acetate (EVA) co-polymer. Because the first material is harder, and more resistant to stretching than the second material, the first and third layers act to provide structural support to the second and fourth layers. Further, because the first and third layers do not melt during the sealing process, they prevent weakening at the edge of the seal.

In another aspect, the invention is embodied in a method for forming a fluid container for a warming cassette to be used in a fluid warming system. The method comprises the steps of: forming a first sheet having at least first and second flexible layers; forming a second sheet having at least third and fourth flexible layers; and joining the first and second sheets by a seal formed between the second and fourth layers. Forming the first sheet can include joining the first and second layers to form a first laminated sheet structure, and forming the second sheet can include joining the third and fourth layers to form a second laminated sheet structure.

The first and third layers are films of a first material having a low coefficient of friction and a first melting point. The second and fourth layers are films of a second material having a lower melting point than the first melting point. Joining the first and second sheets includes joining the second and fourth layers by a thermal bond between those layers. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective illustration of the parenteral fluid or blood container ("fluid container") of this invention.

Fig. 1A is a detailed illustration of Section C of Fig. 1 showing a fluid connector.

Fig. 2 is a more detailed assembly depiction of the fluid container of Fig. 1.

Fig. 3 depicts the fluid container of Fig. 2 with the first and second sheets being joined to each other. Fig. 4a is an end view of the fluid container of Fig. 3, showing the layer outside edges.

Figs. 4b 1 through 4b3 depict the fluid container 10 where the layers are of different sizes.

Figs. 4c 1 and 4c2 depict another alternate embodiment edge alignment. Fig. 4d depicts a cutoff sectional view of another alternate embodiment edge alignment.

Fig. 4e depicts a cutoff sectional view of another alternate embodiment edge alignment.

Fig. 5 depicts the fluid container of Fig. 1, where the first sheet is comprised of three layers.

Figs. 6a and 6b detail the inlet/outlet ports of the fluid container of Fig. 1. Fig. 7 illustrates the first port of Figs. 6a and 6b with IV connection tubing.

Fig. 8 is a flowchart illustrating the present invention method for forming a cassette fluid container.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A parenteral fluid container in a warming cassette according to this invention is provided by joining at least two sheets, with each sheet including two or more layers of synthetic films. Typically, in each sheet at least one layer is functionally a structural layer, and at least a second layer is functionally a thermo- sealable layer. Fig. 1 is a perspective illustration of the parenteral fluid or blood container ("fluid container") 10 of this invention. The fluid container 10 is used in a warming cassette of a parenteral fluid warming system 12. A typical fluid warming system could include a warming unit with two heating plates 14 and 16. The fluid container 10 is incorporated into a cassette structure (not shown), which adds the element of rigidity to the fluid container 10. The cassette structure is inserted between plates 14 and 16 to heat the contents of the fluid container 10. Alternately, the cassette (and the fluid container 10) could be warmed by convection in a stream of heated air, or by conduction in a bath of heated fluid. To construct the fluid container 10, two sets of multi-layered sheets are positioned so that thermo-sealable layers are in opposition to and face each other. The outside exposed surfaces of the fluid container 10 are on the structural layers, or some additional layer, but not on the thermo-sealable layers. A heat sealing platen, RF platen, or US horn is applied to one or both of the structural layer at a temperature which is above the melting point of the material of thermo-sealable layers, but below the melting point of the material of the structural layers. The thermo-sealable layers are melted together outside of channel pattern to form the fluid container with a fluid channel 11 defined therebetween.

Fig. 1A is a detailed illustration of Section C of Fig. 1 showing a fluid connector 110. The connector 1 10 and another connector 130 (see Fig. 1) each communicate with a respective end of the fluid channel 11. These elements are described in more detail below, both as to construction and function.

Fig. 2 is a more detailed assembly depiction of the fluid container 10 of Fig. 1. A first sheet 20 is shown, including a plurality of flexible film layers; two layers 22 and 24 of the first sheet 20 are shown. A second sheet 26 includes a plurality of layers, with layers 28 and 30 of the second sheet being shown. The first sheet 20 overlies, and is at least partially joined to the second sheet 26 by a seal to form a fluid channel therebetween. The pressure tolerance of fluid container 10 is generally improved by using multiple layers of film. The first layer 22 has an outside surface 34 and an inside surface 36; the second layer 24 has an outside surface 38 and an inside surface 40. The third layer 28 has an outside surface 44 and an inside surface 46; the fourth layer 30 has an outside surface 48 and an inside surface 50. The designation of surfaces as inside or outside is arbitrary and not meant to imply that the present invention is limited to a rigidly specific order or orientation.

Fig. 3 depicts fluid container 10 of Fig. 2 with first and second sheets 20 and 26 being joined to each other. The first sheet 20 includes the first layer 22 and the second layer 24, with the second layer 24 being laminated to the first layer 22. That is, the first and second layers 22 and 24 are bonded to form the first sheet 20 as a laminated structure. Likewise, the second sheet 26 includes the third layer 28 and the fourth layer 30, with the fourth layer 30 being bonded to the third layer 28 to form the second sheet 26 as a laminated structure. Further, the second layer 24 is joined to the fourth layer 30 outside of a channel pattern to form the fluid channel 11 between the first and second sheets 20 and 26.

Fig. 3 also illustrates the form of the fluid channel 11. The fluid channel 11, in this figure, is indicated with dotted lines. The second and the fourth layers 24 and 30 are thermally bonded in a pattern to create the fluid channel 1 1, which in the figure, has a seφentine pattern. However, the present invention is not limited to any particular fluid channel shape.

Many techniques are contemplated for bonding the layers of a multi- layered sheet to create a laminated structure. These include adhesive bonding the layers, thermal bonding the layers and extruding a molten layer of one material directly onto a layer of another material layer ("extrusion coating"). A bond can be made entirely across the surface of a layer. Alternately, layer edges are bonded to create a seam, or a seam pattern may be established across the layer surfaces.

The first and third layers 22 and 28 (hereinafter, the "structural layers") generally serve two puφoses. First, the layers 22 and 28 are made from a relatively strong plastic or foil film material. A thin layer of the material is adequate to provide the necessary strength and without a significantly sacrificing thermal conductivity. Second, the structural layers 22 and 28 have a melting point that is significantly higher than the thermo-sealable material of the second and fourth layers 24 and 30 (hereinafter, the "thermosealable layers"). The temperature that is adequate to melt and seal the thermosealable layers 24 and 30 is less than the melting point of the structural layers 22 and 28. The heat from the thermo-sealing process may be applied to the structural layers 22 and 28, which then transfer the heat to the adjacent thermosealable layers 24 and 30. The thermo-sealable layers 24 and 30 never directly contact the heat source and, therefore, they cannot melt onto and foul the heat source during manufacturing. This vastly simplifies the manufacturing of the fluid container by allowing basic heat sealing techniques to be used, rather than RF or US welding. Additionally, since the melting temperature of the structural layers 22 and 28 is not reached, the structural layers 22 and 28 do not melt and thin at the edge of the thermal seal. Therefore, the structural layers 22 and 28 still retain their full strength after heat sealing the thermosealable layers 24 and 30.

In a preferred aspect, the first and third (structural) layers 22 and 28 are formed from a first material having a first melting point, and the second and fourth (thermosealable) layers 24 and 30 are formed from a second material having a second melting point which is lower than the first melting point. Reference designator 72 represents the application of heat to the first and third layers 22 and 28, respectively. The difference in melting points between the two materials permits the second and fourth layers 24 and 30 to be joined by a thermal bond.

The first and second sheets 20 and 26 may be formed by extrusion coating. That is, the second layer 24 is formed on the first layer 22 through an extrusion coating process. Likewise, the third and fourth layers 28 and 30 may be formed by extrusion coating.

Alternately, the first and second layers 22 and 24 may be laminated by adhesive bonding, as may the third and fourth layers 28 and 30. In another alternative aspect of the invention, the first and second layers 22 and 24 may be laminated by solvent bonding, as may the third and fourth layers 28 and 30. In some aspects of the invention, the first and third layers 22 and 28 are formed from a first material having a first hardness, while the second and fourth layers 24 and 30 are formed from a second material having a second hardness less than the first hardness. Thus, the structural layers 22 and 28 provide additional structural integrity to the fluid container 10. Likewise, the first and third layers 22 and 28 are formed from a first material having a first susceptibility to stretching, while the second and fourth layers are formed from a second material having a second susceptibility to stretching greater than the first susceptibility. Again, this property of the structural layers 22 and 28 provides structural integrity. In some aspects of the invention the first and third layers 22 and 28 are formed from a first material having a first coefficient of friction, while the second and fourth layers 24 and 30 are formed from a second material having a second coefficient of friction greater than the first coefficient of friction. The lower coefficient of friction of the structural layers 22 and 28 permits fluid container 10 to be more easily inserted between warming plates 14 and 16 (see Fig. 1).

In all of these cases, the first material may be selected from the group of materials consisting of polyester, polyamide (Nylon®, DuPont), polyethylene glycol terephthalate (Mylar®, DuPont), metal foils, and ionomer resins (Surlyn®, DuPont). Many other unnamed materials are also suitable. The second material may be selected from the group of materials consisting of polyolefin, polyethylene, polypropylene, polyvinyl chloride (PVC), polyurethane, and ethyl vinyl acetate (EVA) co-polymer. Many other unnamed materials are also suitable.

Fig. 4a is an end view of the fluid container 10 of Fig. 3, showing the layer outside edges. Fig. 4a depicts an embodiment where the layers, and layer edges align. In this figure, the second and fourth layers 24 and 30 have outside edges 80 and 82, respectively. In some aspects of the invention the edges 80 and 82 extend all the way around the perimeter of the second and fourth layers 24 and 30.

Likewise, the first and third layers 22 and 28 have outside edges 84 and 86, respectively. In some aspects of the invention the edges 84 and 86 extend all the way around the perimeter of the first and third layers 22 and 28. Referring briefly to Fig. 3, the first, second, third, and fourth layers 22, 24, 28, and 30 are depicted as having substantially equal sizes, meaning the surface area of the layers 22, 24,

28, and 30 are the same dimensions and shape, so that the outside edges 80, 82, 84, and 86 substantially align.

Figs. 4b 1 through 4b3 depict the fluid container 10 where the layers 22, 24, 28, and 30 are of different sizes. Fig. 4bl is a cutoff section view depicting thermosealable layers 24 and 30 having a larger size (larger surface area) than structural layer 22 and 28, so that outside edges 80 and 82 are shown extending, at least partially, past the outside edges 84 and 86. In the preferred embodiment of the invention layers 22, 24, 28, and 30 are rectangular with outside edges 80 and 82 extending beyond outside edges 84 and 86 (not shown) around all four sides 87, 88, 89, and 90, as shown in Fig. 4b2. Alternately, edges 80 and 82 only extend beyond edges 84 and 86 on either one, two, or three sides.

Fig. 4b3 depicts an alternative where only portions of second and fourth layers 24 and 30 are formed to be larger size than first and third sheets 22 and 28. That is, sheets 24 and 30 have edges 80 and 82 formed into tab sections. The invention is not limited to any particular shape of tabs, number of tabs, or the placement of tabs on any particular side of the sheet.

Returning to Fig. 4b 1, the extension of edges 80 and 82 past edges 84 and 86 results in the formation of exposed surfaces 91a and 91b. In some aspects of the invention the surfaces 91a and 91b are used to bond the fluid container 10 to a frame structure (not shown) in the construction of a warming cassette. The thermosealable property of the second and fourth layers 24 and 30 permits a convenient bonding process for this puφose.

Figs. 4c 1 and 4c2 depict another alternate embodiment edge alignment. Fig. 4c 1 is a cutout section view of the fluid container 10 where the edges 84 and 86 extend, at least partially, past the edges 80 and 82. As above, and shown in Fig. 4c2, the preferred embodiment of the invention includes layers 22, 24, 28, and 30 being rectangular, with sheets 22 and 28 being of a larger size (greater surface area) than thermosealable sheets 24 and 30. Therefore, the outside edges 84 and 86 extending beyond outside edges 80 and 82 around all four sides 87, 88, 89, and 90, as shown in Fig. 4b2. Alternately, edges 80 and 82 only extend beyond edges 84 and 86 on either one, two, or three sides. By analogy to the description of Fig. 4b3, layers 22 and 28 can be formed into tabs of various shapes and placements,

Returning to Fig. 4c 1, the extension of edges 84 and 86 past edges 80 and 82 results in the formation of exposed surfaces 91a and 91b. In some aspects of the invention the surfaces 91a and 91b are used to bond the fluid container 10 to a frame structure (not shown) in the construction of a warming cassette.

Fig. 4d depicts a cutoff sectional view of another alternate embodiment edge alignment. In this case, first layer 22 is a larger size (as measured in area) than sheets 24, 28, and 30. Edge 84 extends, at least partially, past the edges 80, 86, and 82. Here, the extension of edge 84 past edges 80, 82, and 86 results in a surface 91a which can be used for bonding to the support frame in some aspects of the invention. By analogy to the descriptions of Figs. 4b2 and 4b3 above, in the preferred embodiment of the invention, the edge 84, and therefore mating surface 91a, extends around all four sides of layer 22. Alternately, the edge 84 extends around one, two, three sides, or is formed into various tabs. Obviously, the above description would also apply to the formation of third sheet edge 86, instead of first sheet edge 84.

Fig. 4e depicts a cutoff sectional view of another alternate embodiment edge alignment. In this case, the first and second layers 22 and 24 are larger in size than the third and fourth layers 28 and 30. The edges 84 and 80 extend, at least partially, past the edges 82 and 86. Here, the extension of edges 84 and 80 past edges 82 and 86 results in surface 91a, which can be used for bonding to the support frame in some aspects of the invention. By analogy to the descriptions of Figs. 4b2 and 4b3 above, in the preferred embodiment of the invention, the edges 84 and 80, and therefore the mating surface 91a extends around all four sides of layers 22 and 24. Alternately, the edges 84 and 80 extend around one, two, three sides, or are formed into various tabs. Obviously, the above description would also apply to the formation of third and fourth sheet edges 82, instead of first and second sheet edges 84 and 80.

Returning to Fig. 4a, the second layer 24 has a thickness 92 in the range of approximately 0.5 to 3.5 mils. Likewise, the fourth layer 30 has a thickness (not shown) that is similar to the thickness of second layer 24. The first layer 22 has a thickness 94 in the range of approximately 0.5 to 1 mil. The third layer 28 has a thickness (not shown) that is similar to thickness 94 of first layer 22. These ranges of layer thicknesses permit the first and third layers 22 and 28 to afford support and protection to the second and fourth layers 24 and 30 and to the fluid channel 10.

Taking these thickness ranges into account, the first sheet 20 has a thickness 96 in the range of approximately 1 to 4 mils, and the second sheet thickness (not shown) has approximately the same thickness. Thus, the first and second sheets 20 and 26 have a combined thickness 98 in the range of approximately 2 to 8 mils.

In another variation of the embodiments illustrated and described thus far, the third layer 28 can be omitted altogether from the construction of the fluid container. The advantage of thermally bonding the second and fourth layers 24 and 30 by application of heat through the first layer 22 can be maintained by provision of a cooled roller or a disposable silicone sheet beneath the fourth layer. Some sacrifice is made in an increased coefficient of friction by exposure of the fourth sheet 30. However, the benefit gained is increased thermal conductivity to the fluid channel by deletion of the third layer 28.

Fig. 5 depicts an embodiment of the fluid container 10 of Fig. 1 where the first sheet 20 is comprised of three layers. While a preferred embodiment of the invention envisions a sheet of two layers, other designs are contemplated. If more than two layers are used, the previously noted design characteristics may be divided among the various layers. For example, a sheet comprised of three or more layers, may have an external layer made of a thermosealable material in order to support thermal bonding to a plastic frame or support structure. Further, certain types of plastics are better for bonding to printing ink, others for solvent bonding. A layer of aluminum foil may be added to either or both sheets to reduce moisture vapor transmission through the plastic materials of the sheets. As used herein, the word "layer" implies a relatively flexible film material, as opposed to a coating of adhesive between first and second layers 22 and 24, for example.

In some aspects of the invention, the first sheet 20 may further include a fifth layer 100, having an inside surface 102, overlying the second layer's outside surface 38. In some aspects of the invention (not shown), the fifth layer 100 directly overlies the second layer 24, between layers 22 and 24. Alternately (as shown), the fifth layer's inside surface 102 overlies the first sheet's outside surface 34. This permits the fifth layer 100 to be removed from the fluid container 10. In some aspects of the invention, the fifth layer 100 including markings (not shown) used to identify fluid container 10. The markings may be visible and decipherable by eye, or may be a bar code, or identifiable through other electronic means.

In other aspects of the invention, the first layer 22 is formed from a first material having a first resistance to moisture, and second layer 24 is formed from a second material having a second resistance to moisture. The first sheet 20 further includes a fifth layer 100 formed from aluminum foil having a third resistance to moisture greater than the first and second resistances. In this manner, the moisture vapor transmission rate (MVTR) of first sheet 20 is improved. In some aspects of the invention, a sixth layer 106 is bonded to the second sheet 26 in a manner similar to the fifth layer 100 of the first sheet 20. Four or more sheets (not shown) can be laminated to each sheet. Figs. 6a and 6b show construction details of the inlet/outlet ports 110, 130 shown in Fig. 1, when the fluid container 10 is incoφorated into a warming cassette 200. Fig. 6a is a plan view of the warming cassette 200 showing a cross- section A-A through a first port 110. The port 110 is operatively in fluid communication with the fluid channel 70 to permit the fluids to flow through the fluid container 10. As seen in Fig. 1A, first port 110 typically includes a fitment or insert 111. Returning to Fig. 6a, the insert 111 is substantially a cylindrical structure having proximal and distal ends 112 and 114, respectively. The insert 111 is made from materials capable of bonding with, or to, the materials of the fluid container, as well as with IV tubing (see Fig. 7). In one aspect of the invention, the insert 111 is formed by a coextrusion process, with a thermosealable material on its surface outside capable of bonding to the second and fourth layers, and a PVC-like material on its inside capable of bonding to the IV tubing. In another aspect, the insert 111 comprises concentric circular layers and is made using a two-shot injection molded part. Alternately, the choice of insert material is made less critical by mechanically fitting the insert 11 1 to the container 10, with a barb-fitting being an example in this regard. In yet another alternative, the insert 111 is mechanically interlocked between layers 24 and 30, or between layers 22 and 28.

Fig. 6b is a partial cross-sectional view along A-A of Fig. 6a. In this figure, the second and fourth layers 24 and 30 are shown with outside edges 80 and 82, respectively, which are also shown in Fig. 4a. The insert 111 has an inner sleeve 116 of PVC material. In some aspects of the invention, the outer sleeve 118 is made of EVA material. Regardless of the exact material, the outer sleeve 118 is typically joined to the fluid container 10 between said second and fourth layers 24 and 30 by thermo-bonding. Such a bond is especially effective when the second and fourth layers 24 and 30 are made from a film of a thermo-sealable material similar to the material of insert outer sleeve 118. Returning to Fig. 6a, the distal end 114 of the insert 111 is connected to the fluid channel 70. The proximal end 112 of the insert 111 extends beyond the second and fourth edges 80 and 82.

Fig. 7 illustrates the first port 110 of Figs. 6a and 6b connected with IV tubing. In this figure, a first tube 120, typically of PVC material, has a distal end 122 and an outer diameter 124. The outer diameter 124 is joined to the inner sleeve 116, which is also a PVC material. Typically, the tube 120 and inner sleeve 116 are joined by solvent bonding.

Returning again to Fig. 6a, the fluid container 10 includes the first port 110 which may serve as a fluid inlet port, and further includes a second port 130 in communication with the fluid channel 70 to permit the outflow of fluid from the fluid container 10. In a manner similar to above-described first port 1 10, the second port 130 is connected to a second tube (not shown). In some aspects of the invention (not shown) the fluid container 10 may have just a single port to dispense fluids. Fig. 8 is a flowchart illustrating a method for forming a fluid container for use in a warming cassette. Initially, Step 202 forms a first sheet including at least a first and second layer. Step 204 forms a second sheet including at least a third and fourth layer. Typically, the layers are flexible films. Step 202 joins the first and second layers together, while Step 204 joins the third and a fourth layers together. Step 206 joins the first and second sheets with a seal acting between the second and fourth layers to form a fluid container between the first and second sheets. Optionally, Step 206 includes selectively joining the first and second sheets to form a seφentine pattern fluid channel. Step 208 yields a product in the form of a fluid container having two multilayer sheets, in which a first plurality of layers (the first and third layers) add structural integrity to the fluid container.

Step 206 includes joining the second and fourth layers by thermo- bonding. Steps 202 and 204 form first and third layers from a first material having a first melting point. The second and fourth layers are formed from a second material having a second melting point lower than the first melting point. Then, Step 206 includes applying heat to the first and third layers to join the second and fourth layers by thermo-bonding. Step 202 also includes extrusion coating the second layer on the first layer, and Step 204 also includes extrusion coating the fourth layer on the third layer. Optionally, Steps 202 and 204 include selecting the second material from the group of materials consisting of polyolefin, polyethylene, polypropylene, polyvinyl chloride (PVC), polyurethane, and ethyl vinyl acetate (EVA) co- polymer. Optionally, Steps 202 and 204 include selecting the first material from the group of materials consisting of polyester, polyamide, polyethylene glycol terephthalate, metal foils, and ionomer resins.

In some aspects of the invention, Step 202 includes laminating the first and second layers by adhesive bonding, and Step 204 includes laminating the third and fourth layers by adhesive bonding. Alternately, Step 202 laminates the first and second layers by solvent bonding, and Step 204 laminates the third and fourth layers by solvent bonding.

In some aspects of the invention, Steps 202 and 204 include the first and third layers being formed from a first material having a first hardness, and include the second and fourth layers being formed from a second material having a second hardness less than the first hardness. In some aspects, Steps 202 and 204 include forming the first and third layers from a first material having a first coefficient of friction, and forming the second and fourth layers from a second material having a second coefficient of friction greater than the first coefficient of friction. Likewise, Steps 202 and 204 include forming the first and third layers from a first material having a first susceptibility to stretching, and forming the second and fourth layers from a second material having a second susceptibility to stretching greater than the first susceptibility.

In some aspects of the invention Step 200 provides a fifth layer of film, having markings for the puφose of identification, and Step 202 includes joining the fifth layer to the first sheet. Alternately, Step 202 includes forming the first layer from a first material having a first moisture vapor transmission rate (MVTR), forming the second layer from a second material having a second MVTR, and forming the fifth layer from aluminum foil which has a third MVTR lower than the first and second MVTR. In some aspects of the invention, Step 200 provides at least a first fluid port insert having proximal and distal ends, an inner sleeve of PVC material, and an outer sleeve. In some aspects of the invention the insert outer sleeve is made from an EVA material. Then, Step 206 includes joining the insert's outer sleeve between the second and fourth layers by thermo-bonding. The insert's distal end is connected to the fluid channel and the insert's proximal end extends past the second and fourth layers' outside edges.

Likewise, a second fluid port insert is provided in Step 200 having proximal and distal ends, an inner sleeve of PVC material. Step 206 includes joining the outer sleeve between the second and fourth layers by thermo-bonding, with the insert's distal end connected to the fluid channel and the insert's proximal end extending past the second and fourth layers' outside edges.

In some aspects of the invention, Step 202 includes the first and second layers having substantially the same size, an equal surface area and shape. The first and second layers are joined so that the outside edges of the first and second layers substantially align. That is, the interfacing surfaces of the first and second layers are not exposed. Likewise, Step 204 includes the third and fourth layers having substantially the same size, an equal surface area and shape. The third and fourth layers are joined so that the outside edges of the third and fourth layers substantially align. That is, the interfacing surfaces of the third and fourth layers are not exposed. Step 206 includes joining the first and second sheets so that the outside edges of the first, second, third, and fourth layers align, as defined above.

Alternately, the layers need not be the same size, with Step 202 forms the first layer be a larger size, as measured in area, than the second layer. The first layer outside edge extends, at least partially, past the second layer outside edge, and Step 204 including that the third layer be a larger size than the fourth layer, with the third layer outside edge extending past the fourth layer outside edge.

Step 206 includes joining the first and second sheets so that surfaces of the first and third layers are exposed.

In some aspects of the invention, Step 202 includes the second layer being a larger size, as measured in area, than the first layer. The second layer outside edge extends, at least partially, past the first layer outside edge, and Step 204 includes that the fourth layer is a larger size than the third layer, with the fourth layer outside edge extending past the third layer outside edge. Step 206 includes joining the first and second sheets so that surfaces of the second and fourth layers are exposed. Alternately, Step 202 includes the first layer being a larger size, as measured in area, than the second layer. The first layer outside edge extends, at least partially, past the second layer outside edge. Step 204 includes the third and fourth layer being smaller in size that the first layer. Step 206 includes joining the first and second sheets so that surfaces of the first layer are exposed.

In some aspects of the invention, Step 202 includes the second layer being a larger size, as measured in area, than the first layer. The second layer outside edge extends, at least partially, past the first layer outside edge. Step 204 includes the third and fourth layer being smaller in size that the second layer. Step 206 includes joining the first and second sheets so that surfaces of the second layer are exposed.

A fluid container, and method for forming a fluid container for use in a parenteral warming cassette have been described in terms of a number of embodiments. This description is meant to illustrate the invention. Other variations and embodiments of the invention will occur to those skilled in the art.

Claims

What is claimed is:CLAIMS

1. A fluid container for a warming cassette comprising: a first sheet including a plurality of layers; a second sheet including a plurality of layers; and said first sheet joined to said second sheet to form a fluid channel therebetween.

2. The fluid container of claim 1 in which said first sheet includes a first layer and a second layer laminated to said first layer; and in which said second sheet includes a third layer and a fourth layer laminated to said third layer.

3. The fluid container of claim 2 in which said second layer is joined to said fourth layer to form the fluid channel between said first and second sheets.

4. The fluid container of claim 3 in which said first and third layers are formed from a first material having a first melting point, and said second and fourth layers are formed from a second material having a second melting point which is lower than the first melting point.

5. The fluid container of claim 4 in which said second and fourth layers are joined by a thermo-bond.

6. The fluid container of claim 4 in which said first and second sheets are formed by extrusion coating.

7. The fluid container of claim 4 in which the second material is selected from the group of materials consisting of polyolefin, polyethylene, polypropylene, polyvinyl chloride (PVC), polyurethane, and ethyl vinyl acetate (EVA) co-polymer.

8. The fluid container of claim 4 in which said second and fourth layers each have a thickness in the range of 0.5 mils to 3.5 mils.

9. The fluid container of claim 4 in which the fluid channel has a seφentine pattern.

10. The fluid container of claim 2 in which said first and second layers are laminated by adhesive bonding, and said third and fourth layers are laminated by adhesivebonding.

1 1. The fluid container of claim 2 in which said first and second layers are laminated by solvent bonding, and said third and fourth layers are laminated by solvent bonding.

12. The fluid container of claim 2 in which said first and third layers are formed from a first material having a first hardness, and in which said second and fourth layers are formed from a second material having a second hardness less than the first hardness.

13. The fluid container of claim 12 in which said first material is selected from the group of materials consisting of polyester, polyamide, polyethylene glycol terephthalate, metal foils, and ionomer resins.

14. The fluid container of claim 12 in which said first and third layers each have a thickness in the range of 0.5 mil to 1 mil.

15. The fluid container of claim 2 in which said first and third layers are formed from a first material having a first susceptibility to stretching, and in which said second and fourth layers are formed from a second material having a second susceptibility to stretching greater than the first susceptibility.

16. The fluid container of claim 2 in which said first and third layers are formed from a first material having a first coefficient of friction, and in which said second and fourth layers are formed from a second material having a second coefficient of friction greater than the first coefficient of friction.

17. The fluid container of claim 2 in which first and third layers are larger in size than said second and fourth layers, in which said second and fourth layers have outside edges and said first and third layers have outside edges, said first and third layer outside edges extending past said second and fourth layer edges to expose surfaces of said first and third layers.

18. The fluid container of claim 2 in which second and fourth layers are larger in size than said first and third layers, in which said second and fourth layers have outside edges and said first and third layers have outside edges, said second and fourth layer outside edges extending past said first and third layer outside edges to expose surfaces of the second and fourth layers.

19. The fluid container of claim 2 in which said first, second, third, and fourth layers are substantially equal in size, in which said second and fourth layers have outside edges and said first and third layers have outside edges, and in which said first, second, third and fourth layers outside edges substantially align.

20. The fluid container of claim 2 in which said second layer is larger in size than said first, third, and fourth layers, in which said first, second, third, and fourth layers have outside edges, and in which said second layer outside edge extends past said first, third and fourth outside edges to expose surfaces of said second layer.

21. The fluid container of claim 2 in which said first layer is larger in size than said, second, third, and fourth layers, in which said first, second, third, an fourth layers have outside edges, and in which said first layer outside edge extends past said second, third and fourth outside edges to expose a surface of said first layer.

22. The fluid container of claim 2 in which said first sheet further includes a fifth layer including markings used to identify the fluid container.

23. The fluid container of claim 2 in which said first layer is formed from a first material having a first resistance to moisture, in which said second layer is formed from a second material having a second resistance to moisture, and in which said first sheet further includes a fifth layer formed from aluminum foil having a third resistance to moisture greater than the first and second resistances.

24. The fluid container of claim 3 further comprising: at least a first port operatively connected to the fluid channel to permit the communication of fluids with the fluid container.

25. The fluid container of claim 24 in which said at least first port includes a substantially cylindrical insert structure having proximal and distal ends, an inner sleeve of PVC material, and in which said at least first port insert outer sleeve is joined to the fluid container between said second and fourth layers by thermo-bonding, with at least said first port in fluid communication with the fluid channel.

26. The fluid container of claim 25 in which said at least first port insert distal end is connected to the fluid channel and said at least first port insert proximal end extends beyond said second and fourth layer outside edges.

27. The fluid container as in claim 25 further comprising: a least a first tube of PVC material having a distal end, and inner and outer diameters; and in which said at least first tube outer diameter is joined to said inner sleeve of said at least first port insert proximal end with solvent bonding.

28. The fluid container of claim 1 in which said first and second sheets each have a thickness in the range of 1 mil to 4 mils, and in which said first and second sheets have a combined thickness in the range of 2 mils to 8 mils.

29. In a parenteral fluid warming system using a warming cassette, a method for forming a fluid container comprising the steps of: a) forming a first sheet of at least a first and second layer; b) forming a second sheet of at least a third and fourth layer; and c) joining the first and second sheets with a seam acting between the second and fourth layers to form a fluid container therebetween.

30. The method as in claim 29 in which Steps a) and b) include the first, second, third and fourth layers being flexible films.

31. The method of claim 29 in which Step a) includes joining a first and second layer together, and in which Step b) includes joining a third and a fourth layer together.

32. The method of claim 29 in which Step a) includes the first layer being larger in size than the second layer, with the first layer outside edge extending past the second layer outside edge, in which Step b) includes the third layer being larger in size than the fourth layer, with the third layer outside edge extending past the fourth layer outside edge, and in which Step c) includes joining the first and second sheets so that surfaces of the first and third layers are exposed.

33. The method of claim 29 in which Step a) includes the second layer being larger in size than the first layer, with the second layer outside edge extending past the first layer outside edge, in which Step b) includes the fourth layer being larger in size than the third layer, with the fourth layer outside edge extending past the third layer outside edge, and in which Step c) includes joining the first and second sheets so that surfaces of the second and fourth layers are exposed.

34. The method of claim 29 in which Step a) includes the first layer being larger in size than the second layer, with the first layer outside edge extending past the second layer outside edge, in which Step b) includes the third and fourth layers being smaller in size than the first layer, and in which Step c) includes joining the first and second sheets so that surfaces of the first layer are exposed.

35. The method of claim 29 in which Step a) includes the first and second layer being equal in size, in which Step b) includes the third and fourth layers being smaller in size than the second layer, and in which Step c) includes joining the first and second sheets so that the first and second layer outside edges extend beyond the third and fourth layer outside edges.

36. The method of claim 29 in which Step a) includes the first and second layers being substantially equal in size and joined so that the outside edges align, in which Step b) includes the third and fourth layers being substantially equal in size, and joined so that the outside edges align, and in which Step c) includes joining the first and second sheets so that outside edges of the first, second, third, and fourth layers align.

37. The method of claim 29 in which Step c) includes joining the second and fourth layers by thermo-bonding.

38. The method of claim 37 in which Steps a) and b) include forming the first and third layers from a first material having a first melting point, and forming the second and fourth layers from a second material having a second melting point lower than the first melting point, and in which Step c) includes applying heat to at least one layer of the first and third layers to join the second and fourth layers by thermo-bonding.

39. The method of claim 38 in which Step a) includes extrusion coating the second layer on the first layer, and in which Step b) includes extrusion coating the fourth layer on the third layer.

40. The method as in claim 38 in which Steps a) and b) include selecting the second material from the group consisting of polyolefin, polyethylene, polypropylene, polyvinyl chloride (PVC), polyurethane, and ethyl vinyl acetate (EVA) co-polymer.

41. The method of claim 40 in which Steps a) and b) include selecting the first material from the group consisting of polyester, polyamide, polyethylene glycol terephthalate, metal foils, and ionomer resins.

42. The method of claim 31 in which Step a) includes laminating the first and second layers by solvent bonding, and in which Step b) includes laminating the third and fourth layers by solvent bonding.

43. The method of claim 29 in which Steps a) and b) include the first and third layers being formed from a first material having a first hardness, and forming the second and fourth layers from a second material having a second hardness less than the first hardness.

44. The method of claim 31 in which Step a) includes laminating the first and second layers by adhesive bonding, and in which Step b) includes laminating the third and fourth layers by adhesive bonding.

45. The method of claim 31 wherein a fifth layer, having markings for the puφose of identification, is provided, and in which Step a) includes joining the fifth layer to the first sheet.

46. The method of claim 31 wherein a fifth layer is provided, and in which Step a) includes forming the first layer from a first material having a first moisture vapor transmission rate (MVTR), forming the second layer from a second material having a second MVTR, forming the fifth layer from aluminum foil which has a third MVTR lower than the first and second MVTR, and in which Step a) includes joining the fifth layer to the first sheet.

47. The method of claim 29 wherein at least a first fluid port insert is provided having proximal and distal ends, an inner sleeve of PVC material, and an outer sleeve, and in which Step c) includes joining the at least first port outer sleeve between the second and fourth layers by thermo-bonding, with the at least first port insert distal end connected to the fluid channel and the at least first port insert proximal end extending past the second and fourth outside edges.

48. The method of claim 29 in which Step c) includes selectively joining the first and second sheets to form a fluid channel having a seφentine pattern.

49. The method of claim 29 in which Steps a) and b) including forming the first and third layers from a first material having a first coefficient of friction, and forming the second and fourth layers from a second material having a second coefficient of friction greater than the first coefficient of friction.

50. The method of claim 29 in which Steps a) and b) include forming the first and third layers from a first material having a first susceptibility to stretching, and forming the second and fourth layers from a second material having a second susceptibility to stretching greater than the first susceptibility.

51. A heat exchanger container for the warming of parenteral fluids comprising: thermo-sealed layers selectively joined to create a fluid channel there through; and structural layers substantially surrounding said thermo-sealed layers.