A DOUBLE LUMEN CANNULA AND ITS METHOD OF MANUFACTURE

Abstract: A cannula (14) includes a tubular member (36) having a bore (42) which is divided into two lumens (32, 34) by a member (38) extending in the bore (42). The divider member (38) is crimped into sealing contact against the bore sidewall (40) at the distal ends (44, 46) of the bore (42). The crimped end portions (68, 78) serve to close a different lumen at each distal end. Openings (74, 84) are formed in the sidewall (40) of the bore (42) in the vicinity of each distal end (44, 46) to establish communication with the associated sealed lumen. Mixing or recirculation between the fluid paths through the lumens (32, 34) is thereby minimized at each distal end (44, 46) as much as possible.

Description: A DOUBLE LUMEN CANNULA AND ITS METHOD OF MANUFACTURE FIELD OF THE INVENTION The invention generally relates to medical purpose cannulas. More specifically, the invention relates to medical purpose cannulas having two lumens. BACKGROUND AND OBJECTS OF THE INVENTION Instead of routinely providing infusions of whole blood to a patient, the present medical concensus is that care of a patient is improved by providing only the therapeutic components of whole blood which are required to treat the specific disease. This form of treatment is generally referred to as blood component therapy. OMPI .// WIPO ,, Because of the acceptance of blood component therapy by the medical community, the demand for therapeutic components of whole blood has been ever-increasing. Likewise, the demand for safe and effective systems and methods for collecting, separating, and storing the therapeutic components of whole has grown accordingly. The use of "continuous flow" extracorporeal blood processing procedures can help to offset the limited supply of blood components available for therapeutic purposes. In a "continuous flow" procedure, whole blood is continuously drawn from a donor. The plasma and plasma-based fractions are separated and collected. At the same time, the remaining red blood cells are returned to the donor. Because red blood cells are being continuously returned to the donor, relatively large total volumes of whole blood can be withdrawn for processing. This can result in significantly larger yields of plasma and/or plasma-based fractions, compared to the yields of a single unit, batch collection procedure. For example, in a single unit, batch collection procedure, approximately 5 x 10 platelets can be harvested. In a continuous flow procedure, however, upwards to 60 x 10 platelets can be collected. The advantage of utilizing a continuous flow procedure is apparent. O PI • ry However, there is one potential drawback to a continuous flow procedure, at least from a donor's standpoint. A continuous flow procedure requires two separate fluid paths be established between the processing device and the circulatory system of the donor: one to draw whole blood from the donor for processing, and one to return the red blood cells to the donor after processing. Typically, to accommodate these two opposite flow paths, two separate phlebotomies are performed to insert a single lumen needle into each of the donor's arms. One double lumen phlebotomy needle can, in theory, accommodate these two opposite flow paths and can thereby reduce the number of venipunctures necessary to perform a continuous flow procedure. However, in practice, the use of double lumen needles in continuous flow blood separation and collection procedures is virtually nonexistent. This is because, for the most part, blood collection and separation procedures use volunteer donors, and most conventional double lumen needles are relatively large in size and hence discomforting to a donor, both from a physical and a psychological standpoint. For example, the portion of a conventional double lumen needle assembly which enters the arm typically has an overall outside diameter which is equal to or larger than .095 inch (i.e., less than 13 gauge). In comparison, a conventional single lumen needle has an overall outside diameter of only between .059 inch (17 gauge) and .072 inch (15 gauge). It is not surprising, then, that most blood donors would not favor the use of these larger dual lumen needles. The comfort of donors, both from a physical and a psychological standpoint, is an important consideration which should not be overlooked in the use of double lumen needles in continuous flow procedures. Donor comfort cannot help but bear upon a person's willingness to volunteer to donate blood in the first place. In addition to promoting donor comfort, another desirable feature of a double lumen needle is its ability to effectively isolate the two, usually opposite, fluid flow patterns which it is designed to accommodate. To optimize the performance of the needle, it is desirable to prevent mixing or recirculation of the two opposite fluid flows. Yet another desirable feature of a double lumen cannula is its ease_ of operation. Many conventional double lumen needles include an obturator to perform the venipuncture as well as to control fluid flow through the needle. The use of an obturator can complicate the operation of the needle, as well as increase its overall size. With the foregoing considerations in mind, one of the principal objects of this invention is to provide a double lumen needle which can be used in place of two single lumen needles in a continuous flow blood separation and collection procedure without sacrificing donor comfort. Another principal object of this invention is to provide a double lumen needle which effectively isolates fluid flow patterns in a simple and straightforward manner. Still another principal object of the invention is to provide a double lumen needle which is easy to use. Yet another principal object of this invention is to provide a double lumen needle which lends itself to straightforward, economical manufacturing techniques. SUMMARY OF THE INVENTION To achieve these and other objects, the invention provides a double lumen cannula which can be conveniently used in place of two conventional single lumen needles, but which has generally the same external dimensions of one conventional single lumen needle. The cannula provided by the invention is easy to operate and lends itself to economical, large scale manufacturing methods. More particularly, the cannula which embodies the features of the invention includes a tubular member having an axial bore with opposite distal ends. The cannula also includes a member which extends inside the tubular member and which divides the bore into separate first and second lumens. OMPI_ y. - vvI _PrOv-> .e K& y ' In accordance with one aspect of the invention, the divider member includes a crimped end portion which is positioned adjacent to the one distal end of the bore which is intended to enter the donor during venipuncture. The crimped end portion is bent at an angle relative to the axis of the bore and is pressed into sealing engagement against a portion of the bore sidewall. The crimped end portion blocks fluid flow between the first lumen and the one distal end, while affording fluid flow between the second lumen and the one distal end. The cannula also preferably includes in the vicinity of the one distal end a first opening which communicates with the first lumen. The opening is axially spaced an effective distance away from the one distal end to isolate the flow of fluid through the opening from the flow of fluid through the one distal end. In accordance with another aspect of the invention, the divider member includes a second crimped end portion which is positioned adjacent to the other distal end of the bore which is intended to communicate with external tubing. The second crimped end portion blocks fluid flow between the second lumen and the other distal end, while affording fluid flow between the first lumen and the other distal end. A second opening is formed in the vicinity of the other distal end to open communication with the second lumen. This arrangement effectively isolates the fluid flow patterns in the region of the other distal end and facilitates connection of this end with individual lengths of external tubing. The invention also provides a method for manufacturing the double lumen cannula as just described. The method lends itself to economical large scale manufacturing methods. Other features and advantages of the invention will be pointed out in, or will be apparent from, the specification and claims, as will obvious modification to the embodiments shown in the drawings. DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a double lumen cannula and hub assembly which embodies the features of the invention; Fig. 2 is a partially exploded section view of the assembly taken generally along line 2-2 in Fig. 1; Fig. 3 is an enlarged top view, with portions broken away and in section, of the double lumen cannula which is associated with the assembly shown in Fig. 1 and which embodies the features of the invention; Fig. 4 is a section view of the cannula taken generally along line 4-4 in Fig. 3; Fig. 5 is a bottom view of the cannula shown in Fig. 3; -% - Fig. 6 is a cross section view of the cannula taken along line 6-6 in Fig. 4; Fig. 7 is an enlarged view, with portions broken away and in section, of the operative end of the cannula shown in Fig. 3; Fig. 8 is a diagrammatic view of the double lumen cannula and hub assembly shown in Figs. 1 and 2 in association with a continuous flow blood processing system; Fig. 9 is a alternate side opening arrangement for the cannula shown in Fig. 3; Fig. 10 is a section view taken generally along line 10-10 in Fig. 9; Fig. 11 is an alternate side opening arrangement for the cannula shown in Fig. 3; Figs. 12 and 13 are perspective views of the cannula shown in Figs. 3 through 7 in the process of being assembled; Fig. 14 is a perspective view of a double lumen cannula which embodies features of the invention but which is assembled differently than as shown in Figs. 12 and 13; Fig. 15 is a perspective view of a double lumen cannula which embodies features of the invention but which is assembled different than as shown in Figs. 12, 13, and 14; and Figs. 16 through 18 are section views of the cannula as shown in either Figs. 13, 14, or 15 in the process of having the crimped end portions formed; OMPI y Λr Fig. 19 is a section view of the cannula as shown in either Figs. 13, 14, or 15 in the process of having the side openings formed; Figs. 20a and 20b are perspective views of a double lumen cannula, respectively before and after assembly, which embodies the features of the invention but which are assembled differently than as shown in Figs. 12 and 13, 14, and 15; and Figs. 21a and 21b are perspective views of a double lumen cannula, respectively before and after assembly, which embodies features of the invention but which are assembled differently as shown in Figs. 12 and 13, 14, 15, and 20a and 20b. Before explaining the embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components as set forth in the following description or as illustrated in. the accompanying drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Furthermore, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. OMPI . -1G- DESCRIPTION OF THE PREFERRED EMBODIMENT A hub and cannula assembly 10 is shown in Figs. 1 and 2. As used herein, the term "cannula" broadly signifies a relatively small tube which is insertable into a body cavity, duct, or vessel. Examples of cannulas include catheters, phlebotomy needles, and other similar arrangements used to direct and channel blood, parenteral fluids, and medicines to and from the body. As shown in Figs. 1 and 2, the assembly includes a hub 12 and a cannula 14. The hub 12 is preferably compact in size (see Fig. 1) so it can be easily handled and manipulated between the fingertips of an attendant. As is best shown in Fig. 2, the hub 12 includes a bore 16 which accommodates the cannula 14 with an operative end 18 of the cannula 14 supported in an outwardly projecting, exposed position. The hub 12 also includes a pair of internal fluid passages 20 and 22 which, at one end (respectively 20a and 22a), communicate with the interior fluid paths of the cannula 14 and which, ' at the other end (respectively 20b and 22b), are attachable to conventional tubing 24 and 26. As shown in Fig. 2, to protect the cannula 14 prior to use, the assembly 10 preferably includes a cover 28. In the illustrated embodiment, the cover 28 is removably attachable and reattachable about a post 30 formed on the hub 12. -iL - While the hub 12 may be variously constructed, it is preferably molded of a plastic material which is capable of withstanding sterilization, such as by autoclaving, radiation, or the use of ethylene oxide, with no loss of function or evidence of distortion. The material of the hub 12 is also preferably bondable, such as by solvent bonding, to conventional polyvinyl chloride tubing. Candidates for the hub material include polyvinyl chloride, as well as a thermoplastic copolyetherester manufactured and sold by E. I. DuPont under the trademark HYTREL 4056. ' Representative ornamental configurations of the hub 12 are disclosed in copending Glash et al U.S. Design Patent Applications Serial Numbers , filed on the same date as this application. The cannula 14 is preferably made of medically approved stainless steel. The cannula 14 may be attached to the bore 16 of the hub 12 by various methods, such as solvent or induction bonding or resistance welding. In accordance with the invention, the cannula 14 includes two interior lumens 32 and 34 to accommodate two separate and independent flow patterns through the cannula 14. Attention is now directed principally to Figs. 3 through 7 and the particular construction of the double lumen cannula 14. Generally, the cannula 14 comprises a tubular member 36 and a divider member 38 (see Figs. 4, 6, and 7). As is best shown in Fig. 4, the tubular member 36 includes a sidewall 40 which circumferentially defines an axial bore 42 having oppositely spaced distal ends 44 and 46. At one distal end 44 (see, in particular, Fig. 7), a beveled surface 48 is formed having a rearward edge 50 and a forward edge 52. The forward edge 52 terminates in a sharpened point 54 It is the sharpened distal end 44 which constitutes the heretofore identified operative end 18 of the cannula 14. As shown in Fig. 2, the other distal end 46 is carried within the bore 16 of the hub 12. As is best shown in Fig. 4, the divider member 38 includes a main body portion 60 which extends generally parallel to the axis of the bore 42 between the two distal ends 44 and 46." As best shown in Fig. 3, the side edges 62 and 64 of the main body portion 60 extend along diametrically opposite portions of the bore 16. As shown in Figs. 3 and 6, one side edge 64 abuts snugly against the bore sidewall 40, while the other side edge 62 extends into the bore sidewall 40 (see also Fig. 7). A method of manufacturing the cannula 14 as shown in these figures will be described in greater detail later. By virtue of this construction, the divider member 38 forms an essentially fluid tight interface between the first and second lumens 32 and 34 along the axial length of the bore 42. As can be seen in Fig. 7, in the illustrated embodiment, the main body portion 60 preferably extends transversely of the slope of the beveled edge 48, with the centerline 66 of the main body portion 60 generally axially aligned with the centerline 56 of the sharpened point. Other interior configurations are possible, however, depending upon the environment in which the cannula 14 is to be used. Typically, the fluid flow patterns in the cannula 14 will proceed in opposite directions, with one lumen directing fluid into the cannula 14 and the other lumen directing fluid out of the cannula 14. To minimize mixing or recirculation of fluid between these opposite flow paths, the openings through which the lumens 32 and 34 direct fluids into and out of the cannula 14 are physically spaced and isolated from each other. More particularly, and in accordance with an aspect of the invention, an end 68 of the divider member 38 adjacent to the one distal end 44 is crimped into contact with an arcuate portion 70 of the sidewall 40. As can best be seen in Figs. 3, 4, and 7, the crimped end portion 68 is bent at an angle relative to the axis of the bore 42. The terminus 72 of the crimped end portion 68 is pressed into firm surface engagement against the arcuate portion 70 of the bore sidewall 40 (see, in particular, Fig. 4). The crimped end portion 68 is thereby held in a state of compression between the main body portion 60 and the arcuate sidewall portion 70, against which the terminus 72 is pressed. An essentially fluid-tight seal is thus formed at the interface between the terminus 72 and arcuate sidewall portion 70. As can be seen in Figs. 3, 4, and 7, the crimped end portion 68 is preferably bent toward the sharpened point 54. As best shown in Figs. 4 and 7, the presence of the crimped end portion 68 of the divider member 38 serves alone to block fluid flow between the first lumen 32 and the one distal end 44, while affording fluid flow between the second lumen 34 and the one distal end 44. The crimped end portion 68 obviates the need for inserting a separate plug or closure member into the bore 42 for this purpose. Also in accordance with the invention, means is provided for forming an opening 74 in the vicinity of the one distal end 44. The opening 74 communicates only with the first lumen 32. As can best be seen in Figs. 4 and 7, this opening 74 is formed in the sidewall 40 of the tubular member 36 and is purposely isolated from the distal end 44, with which only the second lumen 34 communicates, both in terms of distance and in terms of attitude. IS More particularly, as is best shown in Fig. 7, the formed opening 74 is positioned generally axially along the centerline 52 of the sharpened point 54 at a predetermined distance away from the sharpened point 54. The distance from the sharpened point 54 should be no closer than and preferably behind the rearward edge 50 of the beveled surface 48 (see Fig. 4) . Preferably, the crimped end portion 68 is formed closely adjacent to the opening 74. This relationship minimizes the size of the area lying between the opening 74 and the terminus 72 of the crimped end portion 68. This, in turn, minimizes the chance that a volume of blood could become entrapped in this "dead" area and form a clot. The axis 76 of the opening 74 (see Fig. 4) extends generally at a right angle to the fluid path in the second lumen 34. Fluid flow through the opening 74 thus proceeds away from and generally at a right angle relative to the fluid flow through the one distal end 44. Fluid flow patterns in the region of the distal end 44 are therefore not only physically spaced from each other, but they are in different directions as well (see Fig. 8). The chance of mixing or recirculation of fluids between the flow paths in this region is thereby minimized to the fullest extent possible. Further, in accordance with the invention, the opening through which the lumens 42 and 44 direct fluid into and out of the cannula 14 in the region of the other distal end 46 are also spaced and isolated from each other. More particularly, as is best shown in Fig. 4, the end 78 of the divider member 38, which is adjacent to the other distal end 46, is crimped into contact with another arcuate portion 80 of the bore sidewall 40. This second crimped end portion 78, like the first described crimped end portion 68, is bent at an angle relative to the axis 58 of the bore 42 toward the arcuate portion 80 of the bore sidewall 40. Like the terminus 72 of the first crimped end portion 68, the terminus 82 of the second crimped end portion 78 is also firmly pressed into surface engagement against the sidewall portion 80. The second crimped end portion 78, like the first crimped end portion 68, is thereby held in a state of compression between the main body portion 60 and the sidewall portion 80 against which the terminus 82 is pressed. An essentially fluid-tight seal is formed at the interface between the terminus 82 and the arcuate sidewall portion ' 80. The second crimped end portion 78 of the divider member 38 thereby blocks fluid flow between the second lumen 34 and the other distal end 46, while affording fluid flow between the first lumen 44 and the other distal end 46. Means is also provided for forming a second opening 84 in the vicinity of the other distal end 46. The second opening 84 communicates only with the second lumen 34. Like the first opening 74, the second opening 84 is formed in the sidewall 40 of the tubular member 36 and is spaced axially away from the adjacent distal end 46. The second opening 84 also has an axis 86 (see Fig. 4) which extends generally at a right angle to the fluid path through the first lumen 32. It should be appreciated that the second crimped end portion 78 can be bent against an arcuate portion of the sidewall 40 which is opposite to the one 80 shown in Fig. 4. In this arrangement, the location of the second opening 84 would likewise be switched to a diametrically opposite sidewall portion. By crimping the second end portion 78 of the divider member 38 and physically spacing the second opening 84 from the other distal end 46, external tubing can be conveniently and independently attached to the first and second lumens 32 and 34 (see Fig. 2). Significantly, by virtue of this construction, each individual lumen 32 and 34 can be relatively small in cross section, because the fluid connection points for the lumens 32 and 34 at the other distal end 46 are physically spaced apart. The overall size of the cannula 14 can thus be reduced. Furthermore, the chance of mixing or recirculation in the region surrounding the other distal end 46 is also reduced to the fullest extent possible. -la¬ in the context of the illustrated hub and cannula assembly 10 (see Figs. 1 and 2), by virtue of the above-described construction, the fluid passages 20 and 22 in the hub 12 can extend in spaced apart paths to communicate, respectively, with the other distal end 46 (i.e., with the first lumen 32) and the second opening 84 (i.e., with the second lumen 34). The double lumen cannula and hub assembly 10 as heretofore described is applicable for use in a diverse number of environments. Since the assembly 10 is particularly by well suited for use in conjunction with a continuous flow blood processing procedure, this specific use is shown in Fig. 8 for illustration purposes. In Fig. 8, the sharpened end 44 of the cannula 14 is shown inserted into a vein 88 (typically in the arm 89 of a donor). While the cannula 14 can be inserted into the vein in various ways, in the illustrated embodiment, the sharpened end 44 faces away from the heart, i.e., the one distal end 44 generally faces into the direction of venous blood flow. This attitude is generally referred to as a "reverse phlebotomy". In this insertion technique, the hub 12 (see, in addition, Fig. 2) preferably includes a generally planar base portion 90 which extends at a small acute angle (i.e., equal to or less than about 10°) away from the axis of the bore 42 of the cannula 14, designated by angle "A" in Fig. 2. This assists the operator in establishing the proper venipuncture position, as shown in Fig. 8. As shown in Fig. 1, the hub 12 also preferably includes wings 92 which extend outwardly from each side of the base portion 90. The wings 92, and thus the entire assembly 10, can be taped to the donor's arm after the venipuncture is made. As can be seen in Fig. 8, the assembly 10 can thus be maintained in the proper position while the procedure is taking place. While various flow patterns through the cannula 14 can be accommodated, in the illustrated embodiment, negative pressure is applied by the associated processing device 94 to draw whole venous blood through the one distal end 44 of the cannula 14 into the second lumen 34. The whole blood exits the second lumen 34 through the second opening 84 and enters the tubing 24 attached to the hub 12. It then proceeds into the processing device 94. An example of the continuous flow device 94 is a CS-3000® Blood Cell Separator, which is manufactured and sold by Fenwal Laboratories, a division of Travenol Laboratories, Inc. To accommodate the selective connection with this or another processing system, the assembly 10 can include conventional luer connectors 96 (see Fig. 2) at the terminus of the each of the tubing 24 and -^JREA^ OMPI IPO / 26. A icroporous barrier 98 or the like can be removably inserted within each luer connector 96 to protect the sterile integrity of the assembly 10 prior to use. In the processing device 94, the whole blood is separated by centrifugation into red blood cells and platelet-rich plasma. The platelet-rich plasma can be further separated into platelets and platelet-poor plasma. These components are retained for storage. The red blood cells are returned to the donor through the tubing 26 attached to the hub 10 and into the other distal end 46 of the cannula 14. The red blood cells proceed through the first lumen 32 and flow out into the vein through the first opening 74. As is shown by arrows in Fig. 8, the outgoing flow of red blood cells is directed away from the incoming flow of whole blood because of the purposeful positioning of the first opening 74 away from the one distal end 44. It should be appreciated that, by applying negative pressure to the first lumen 32 instead of the second lumen 34, an opposite flow of blood through the cannula 14 can be established, with whole blood being drawn into the first opening 74 through the first lumen 32, and the red blood cells being returned through the second lumen 39 and out of the distal end 44. 2\ To prevent the sidewall of the vein 88 from coming into contact with and completely blocking the first opening 74, particularly when a negative pressure is being applied to the first lumen 32, the configuration of the first opening 74 can be other than as shown in Figs. 3 through 7. For example, as shown in Fig. 11, the first opening 74 can take the form of a plurality of smaller openings 74a. Or, as is shown in Figs. 9 and 10, the first opening 74 can also include an overlying dome 100 to prevent the vein 88 from entering and completely occluding the opening 74. The above-described double lumen cannula and hub assembly 10 lends itself to large scale mass production techniques. Significantly, the double lumen cannula 14 which-embodies the features of the invention can be formed in a relatively small size, compared with conventional dual lumen cannulas. Indeed, the double lumen cannula 14 provided by this invention can equal the exterior dimensions of a conventional single lumen needle. Attention is now directed to Figs. 12 through 19 which illustrate a representative method of manufacturing the cannula 14 as heretofore described and shown in Figs. 1 through 7. Generally, this representative method includes the initial steps of forming the tubular member 36 and inserting the divider member 38 to form the two independent lumens 32 and 34. In this representative method, at most, only one side edge 62 or 64 of the divider member 38 is permanently attached in some manner to the tubular member 36. The other side edge or edges make only snug, frictional engagement with the interior sidewall 40 of the tubular bore 42. This arrangement facilitates the bending of the end portions 68 and 78 of the divider member 38 into the desired configuration during a subsequent step in the method. The initial steps of this representative method may be variously accomplished. In the illustrated embodiment (see Fig. 12), the method includes the step of forming from a sheet 102 of medically approved stainless steel the tubular member 36 having a slot 104 which extends along its axial length. The tubular member 36 can be roll formed into this configuration by conventional techniques. The tubular member 36 as shown in Fig. 12 can be formed with a relatively large outer diameter and drawn down to the desired dimension using conventional techniques. The representative method next includes the step of inserting the planar divider member 38 into the bore 42. In the illustrated embodiment, the divider member 38 takes the form of a continuous, thin strip 106 of stainless steel which is inserted through the slot 104. The strip 106 has a width (designated by the letter "W" in Fig. 12) which generally equals the ^J EA^ OMPI interior diameter of the tubular member 36 (designated by the letter "D" in Fig. 12) plus the thickness of one sidewall 40 (designated by the letter "T" in Fig. 12). The strip 106 should be rigid or semi-rigid to facilitate snug frictional engagement against the sidewall 40 of the bore 42 and resist deformation as a result of fluid pressures within the bore 42. However, the thickness of the strip 106 should be minimized to the fullest extent possible to maximize the cross-sectional area of each lumen 32 and 34. As can be seen in Fig. 13, rollers 108 or the like are preferably employed to press the divider strip 106 securely into the bore 42, so that one side edge of the strip (i.e., side edge 64) makes firm frictional sealing engagement against the sidewall portion opposite to the slot 104. In the illustrated embodiment, a laser welding machine 109 or the like is employed to weld along the junction of the strip 106 and the slot 104 to fixedly attached the other side edge 62 to the tubular member. If desired, the tubular member 36 can be drawn down again to clean the area of the weld. In this situation, the initial diameter of the tubular member 36 is slightly larger than the desired finished size, so that this additional draw down to finished size can be made. In this arrangement, the divider member 38 would be initially sized slightly smaller than heretofore described to form the desired frictional sealing engagement between the side edge 64 and the bore sidewall 40 after the additional draw down step is made. The resulting assembly 110 of the tubular member 36 and divider member 38 shown in Fig. 13 can be formed by other means. For example, as shown in Fig. 14, the divider member 38 may be force fitted into the bore 42 of a closed tubular member 36, using, for example, an interference fit up to about .005 inch. In this arrangement, neither side edge 62 and 64 of the divider member 38 is permanently attached to the tubular member 36. Instead, both side edges 62 and 64 are lodged in snug, frictional sealing engagement against the interior sidewall 40 of the bore 42. Still alternately, as shown in Fig. 15, the sheet 102 may be rolled upon itself to form the tubular body 36 and divider 38 in a single piece construction. The intersection 112 is closed by laser welding or the like. In this arrangement, the edge 64 of the divider 38 makes snug frictional engagement against the bore 40 in the tubular body 36. It should be noted that, in all of the embodiments shown in Figs. 13, 14, and 15, at most, only one edge of the divider member 38 is permanently secured by welding or the like to the tubular member 36. This construction facilitates the formation of the crimped end portions 68 and 78 in a subsequent step. The method next includes the step of cutting the tubular member 36 into individual pieces, the length of which corresponds with the desired length of the individual cannula 14. For example, if the cannula 14 is to be used as a phlebotomy needle, the cannula 14 should be about two (2) inches in length. The cutting step can be accomplished by conventional means. The method next includes the step of forming the beveled surface 48 on the one distal end 44 of the tubular member 36. Conventional grinding techniques can be used to accomplish this step. The method next includes the formation of the crimped end portions 68 and 78. As can be seen in Figs. 16 through 18, the crimp forming step includes directing a pair of crimping members 118 into each of the distal ends 44 and 46 of the assembly 110. As shown in Figs. 17 and 18, the crimping members 118 may be carried on the end of hydraulically or pneumatically actuated rams 119. The members 118 travel in a path generally parallel to the plane in which the inserted divider member 38 extends. Each crimping member 118 includes a crimping surface 120 having a surface configuration which generally approximates the desired surface configuration of the crimped end portions 68 and 78. As can be seen in Figs. 17 and 18, as the crimping members 118 are each directed progressively inwardly into the respective distal end 44 and 46, the crimping surface 120 contacts the adjacent terminus 72 and 82. Each terminus 72 and 82 is progressively bent and pressed into engagement between the crimping surface 120 and the respective arcuate sidewall portion 70 and 80. A pair of crimping members 118 may be operated simultaneously, as shown in Figs. 17 and 18. Alternately, a single crimping member 118 may be used in succession to individually form each of the crimped end portions 68 and 78. When the crimping member or members 118 are withdrawn from the distal ends 44 and 46, the terminus 72 and 82 each remain pressed in snug surface engagement against the associated sidewall portion 70 and 80 (see Figs. 4 and 7) . As before stated, in this configuration, an essentially fluid-tight seal is formed at the interface between each terminus 72 and 82 and each arcuate sidewall portion 70 and 80. To supplement this seal, each terminus 72 and 82 can be spot welded in place to the arcuate sidewall portion 70 and 80, if desired. After the crimping member 118 has been withdrawn from the one distal end 44, a finishing grind may be applied to the beveled edge 48 to bring the edge 48 closer to the crimped end portion 68, as shown in phantom line 48a in Fig. 18. As shown in Fig. 19, the method next includes the step of forming the first and second openings 74 and 84. These can be formed by conventional grinding or drilling tools 122. Chemical etching, sandblasting, electrogrinding, or laser drilling could also be used. The method finally includes the step of mounting the formed double lumen cannula 14 on the hub 12 to form the assembly 10 shown in Fig. 2. As before stated, the hub 12 can be formed separately, such as by injection molding. The cannula 14 can be solvent or induction bonded or resistance welded into the hub bore 16 with the opening 84 in proper alignment with the passage end 22a, and the other distal end 44 in proper alignment with the passage end 20a. Conventional tubing 24 and 26 can then be solvent bonded in the passage ends 20b and 22b. After attachment of the luer connectors 96 and plugs 98, and the placement of the cover 28 on the hub 10, the entire assembly 10 can be sterilized. Alternately, the assembly 110 of the tubular member and divider member can be fabricated such that, unlike the assemblies 110 shown in Figs. 13, 14, and 15, both edges of associated divider member are permanently affixed to the formed tubular member. For example, as shown in Figs. 20a and 20b, the assembly 110 can consist of two preformed parts, one of which is generally C-shaped (designated by reference numeral 126) and the other one of which is generally D-shaped (designated by reference numeral 124) . The D-shaped part 124 includes an arcuate side portion 125a and a nonarcuate side portion 125b. As shown in Fig. 20b, by joining the C-shaped part 126 against the nonarcuate side portion 125b of the D-shaped part 124, and by welding along both sides 127 of the junction, the composite assembly 110 can be formed. In the composite assembly 110 shown in Fig. 20b, the C-shaped part 126 and the arcuate side portion 125a of the D-shaped part 124 together serve as the tubular member, and the nonarcuate side portion 125b of the D-shaped part 124 serves as the divider member. Alternately, as shown in Figs. 21a and 21b, the assembly 110 can consist of three preformed parts, two of which are generally C-shaped (designated by reference numerals 128a and 128b) and one of which is generally planar (designated by reference numeral 130). As shown in Fig. 21b, by joining the two C—shaped parts 128a and 128b along opposite sides of the planar part 130, and by welding along both sides 127 of the junctions, the composite assembly 110 can be formed. In the composite assembly 110 shown in Fig. 21b, the two C-shaped parts 128a and 128b together serve as the tubular member, and the planar part 130 serves as the divider member. In the assembly 110 shown in either Fig. 20b or Fig. 21b, both side edges of the formed divider member are welded or otherwise permanently secured to the formed tubular member. In this arrangement, the crimp forming step includes applying sufficient force with the crimping J EA OMPI ~~ -23- members 118 to break or otherwise deform the material of the divider member about a portion of the weld to form the crimped end portions. Using any of the above manufacturing methods, a cannula which embodies the features of the invention can be made in which the tubular member 36 has an outside diameter of approximately .072 inch and an inner diameter of approximately .062 inch. The associated divider member 38 has a thickness of about .005 inch, i.e., about the same thickness as the sidewall 40 of the tubular member 36. The external dimensions of this cannula correspond with the dimension of a conventional 15 gauge single lumen needle. EXAMPLE A dual lumen cannula having the dimensions as just described was inserted in a reverse venipuncture position (as shown in Fig. 8) into the saphenous vein in the rear leg of a large dog. This vein was chosen because of its similarity to the antecubital veins in the human forearm, into which human venipunctures are normally made. The whole blood which was drawn into the one distal end 44 and through the second lumen 34 (as shown in Fig. 8) was introduced into a conventional hollow fiber filtration device. The device included a bundle of conventional polypropylene microporous hollow fibers, each having a maximum pore size of 0.55 μ . These microporous fibers serve to separate -gJREA. OMPI V . WIPO the cellular components of the whole blood (principally red blood cells, platelets, and leukocytes) from the noncellular components (principally plasma) . The separated cellular components were returned to the saphenous vein via the first lumen 32 and the associated opening 74, as shown in Fig. 8. The dual lumen cannula which embodies the features of the invention accommodated flow rates of whole blood to the filtration device of between approximately 20 and 75 milliliters per minute, with the resulting flux of noncellular components through the pores of the microporous material ranging between 20 and 25 milliliters per minute. No hemolysis was observed. Various of the features of the invention are set forth in the following claims.

Claims: -3L- CLAIMS 1. A double lumen cannula assembly comprising a tubular member having a sidewall circumferentially defining an axial bore having opposite distal ends, and a divider member in said bore including a main body portion extending between said distal ends and forming first and second lumens in said bore, and a crimped end portion disposed adjacent to one of said distal ends, said first crimped end portion being bent at an angle relative to the axis of said bore toward and in engagement against a portion of said bore sidewall to block communication between said first lumen and said one distal end, while affording communication between said second lumen and said one distal end. 2. An assembly according to claim 1 and further including means for forming in the vicinity of said one distal end an opening which communicates with said first lumen. 3. An assembly according to claim 1 wherein said divider member includes a second crimped end portion disposed adjacent to the other one of said distal ends, said second crimped end portion being bent at an angle relative to the axis of said bore toward and in engagement against another portion of said bore sidewall to block communication between said second lumen and said other distal end, while affording communication between said first lumen and said other distal end. 4. An assembly according to claim 3 and further including means for forming in the vicinity of said other distal end an opening which communicates said second lumen. 5. An assembly according to claim 4 and further including hub means for supporting said tubular member with said one distal end exposed, said hub means including means defining a fluid path communicating at one end with said opening and attachable at another end with a conduit, and means defining a fluid path communicating at one end with said other distal end and attachable at another end with a conduit. 6. An assembly according to claim 5 and further including means for forming in the vicinity of said one distal end another opening which communicates with said first lumen. 7. An assembly according to claim 2 or 6 wherein said opening which communicates with said first lumen has an axis which extends generally at a right angle relative to the axis of said bore. 8. An assembly according to claim 2 or 6 wherein said opening which communicates with said first lumen is spaced axially away from said one distal end. 9. An assembly according to claim 2 or 6 wherein said first opening comprises a plurality of spaced openings. 10. An assembly according to claim 2 or 6 wherein said first opening includes means defining a dome spanning a portion of said first opening. 11. An assembly according to claim 1 or 3 wherein said crimped end portion includes a terminus which is pressed into firm surface engagement against an arcuate portion of said bore sidewall forming therebetween an essentially fluid-tight seal. 12. A method for manufacturing a double lumen cannula comprising the steps of forming a generally tubular member having an axial bore and oppositely spaced distal ends and including a divider member which extends generally along the bore axis to form first and second lumens in the bore, and crimping an end portion of the divider member adjacent to one distal end of the tubular member to bring the end portion into surface engagement against an arcuate portion of the bore -gTTRE l OMP sidewall and thereby block communication between one of the lumens and the one distal end while affording flow communication between the other lumen and the one distal end. 13. A method according to claim 12 and further including the step of forming at least one opening in the tubular body which communicates with the one lumen. 14. A method according to claim 12 and further including the step of forming at least one opening in the tubular body which communicates with the one lumen in the vicinity of the one distal end. 15. A method according to claim 12 and further including the step crimping an end portion of the divider member adjacent to the other distal end of the tubular member to bring the end portion into surface engagement against an arcuate portion of the bore sidewall and thereby block communication between the other lumen and the other distal end while affording communication between the one lumen and the other distal end. 16. A method according to claim 15 and further including the step of forming at least one opening in the tubular body in communication with the other lumen in the vicinity of the other distal end. 17. A method according to claim 12 or 14 and further including the step of forming a beveled edge along the one distal end. -ZS- 18. A method according to claim 17 and further including the step of mounting the tubular member in a hub with the one distal end exposed. 19. A method according to claim 12 wherein said tubular member formation step includes the steps of forming the generally tubular member, and inserting the divider member in a friction fit within the bore of the tubular member. 20. A method according to claim 12 wherein said tubular member formation step includes the steps of forming the generally tubular member having an axially extending slot, inserting the divider member through the slot into the bore of the tubular member, such that one edge of the divider member is positioned along the interior sidewall of the bore opposite the slot and the opposite edge of the divider member is positioned within the slot, and welding the other edge of the divider member within the slot. 21. A method according to claim 20 wherein said welding step includes laser welding. -^JREX^ OMPI ' ^_ WIPO < t 5 22. A method according to claim 12 wherein said tubular member formation step includes the steps of forming two generally C-shaped members, forming one generally planar member, and joining the two C-shaped members along opposite sides of the planar member to form a composite structure in which the two C-shaped members together serve as the tubular member and the planar member serves as the divider member. 23. A method according to claim 12 wherein said tubular member formation step includes forming one generally D-shaped member have arcuate and non-arcuate side portions, forming one generally C-shaped member, and joining the generally C-shaped member against the non-arcuate side portion of the D-shaped member to form a composite structure in which the C-shaped member and arcuate side portion of the D-shaped member together serve as the tubular member and the non-arcuate side portion of the D-shaped member serves as the divider member.

Inventors: BILSTAD ARNOLD C, BROWN RICHARD I, GLASH DEAN M, KRUGER ROBERT J, BILSTAD, ARNOLD, C., BROWN, RICHARD, I., GLASH, DEAN, M., KRUGER, ROBERT, J.
Applicants: BAXTER TRAVENOL LAB, BAXTER TRAVENOL LABORATORIES, INC.
Application year: 1984
Main classification: A61M5
IPC codes: A61M1, A61M5, A61M25