the advantages of the present invention will be apparent to those skilled in the art from the following specification . accordingly , it will be recognized by those skilled in the art that changes or modifications may be made to the below - described embodiments without departing from the broad inventive concepts of the invention . it should therefore be understood that this invention is not limited to the particular embodiments described herein , but is intended to include all changes and modifications that are within the scope and spirit of the invention . the words “ proximal ” and “ distal ” refer to directions away from and closer to the insertion tip , respectively , of a catheter of the present invention . fig2 depicts a representative multiple - lumen catheter 200 employing the present invention lumen configuration . the catheter comprises an elongated body portion 220 . in the distal end , the body portion 220 connects to a tip structure 210 . the internal space of the body portion 220 is divided into several lumens . each of the lumens has an opening in the tip structure 210 . in the embodiment shown in fig2 , each of the lumens opens at the same point of the tip structure 210 . in other embodiments of the present invention , openings of each of the lumens may be placed at different locations along the tip structure 210 , thereby minimizing mixing and the possibility of adverse reactions when incompatible drugs or therapeutic agents are delivered at the same time through separate lumens of the catheter . other tip structures well know in the art can also be used with the present invention . the proximal end 230 of the body portion 220 of the catheter connects to a plurality of extension tubes 231 232 233 . each of the internal lumen forms a fluid tight connection to an extension tube 231 232 233 . in some embodiments of the present invention more than one lumen can be connected to a single extension tube . each of the extension tubes 231 232 233 further may connect to a connector of a type commonly used in medical applications 241 242 243 , such as luer - lock type connecters , which provides easy linkage to other medical instruments or devices . connectors for the present invention multiple - lumen catheter may be manufactured separately from the catheter , and are attached during insertion of the catheter assembly . clamps 251 252 253 may be placed on the extension tubes to stop fluid flow when the catheter is not in use . the pressure generated by injection of fluid though a rigid tube can be described by poiseuille &# 39 ; s law , which states that : q =( ρ 4 δp )/( η8l ). the rate of flow through a rigid tube ( q ) is proportional to the fourth power of the radius of the tube ( r ) and the difference in pressure at the two ends of the tube ( δp ), and is inversely related to the viscosity of the fluid ( η ) and the length of the tube ( l ). the body portion 220 of catheter is usually made of material that is flexible , such as silicone or polyurethane or other tissue compatible polymers . although not directly applicable , poiseuille &# 39 ; s law provides important guidance to approximate fluid flow characteristics within a multiple - lumen catheter where the walls may flex and expand slightly under pressure . fig3 shows a cross section view of the catheter body of one embodiment of the present invention . two septa 304 divide the internal space of the body portion 220 into three lumens 302 303 . the lumens are arranged in a side - by - side configuration . the central lumen 303 is located essentially in the center of the catheter body , and the two side lumens 302 are located on each side of the central lumen 303 . the central lumen 303 is defined by the two septa 304 and the outer wall 301 of the catheter , and is positioned between the two side lumens 302 . the central lumen 303 has a generally stadium shape in cross section . in the embodiment shown in fig3 , the central lumen 303 is formed by septa with essentially planar side surfaces 306 , and rounded top and bottom surfaces 305 . in other embodiments , the central lumen 303 may have a cross section of an elongated circle , an ellipse , or other shapes that efficiently utilize the internal space of the catheter . in the embodiment shown in fig3 , the side lumens 302 have a crescent or “ d ” shape in cross section . in other embodiments , the side lumens 302 can have circular , elliptical , “ c ” shaped , or other suitable cross sections . the shape of the cross sections of the central lumen 303 and side lumens 302 is chosen so that it provides optimal utilization of the internal space of the body portion 220 of the catheter . the rounded top and bottom surfaces 305 of the central lumen 303 and the outer surface 307 of the catheter body portion 220 form the outer wall 301 of the catheter body portion 220 . the rounded top and bottom interior surfaces 305 of the central lumen 303 connect smoothly to the side surfaces 306 . the inner surface 305 306 of the central lumen 303 is free from any sharp corners . the smooth inner surface 305 306 of the central lumen 303 is optimal for catheter placement along a guide wire . the radius of curvature of the inner surface 305 is chosen to minimize the possibility that any corner within the central lumen 303 can catch the guide wire and hinder the advance of the catheter 200 along the guide wire . for example , if a guide wire of 0 . 018 in . diameter is intended , the radius of curvature for any corner in the central lumen 303 would preferably be equal to or larger than 0 . 009 in . accordingly , in one aspect of the invention , the radius of curvature within the central lumen 303 ( and / or within the side lumens 302 ) is in all locations ( i . e ., at all points along the inner wall of the central lumen 303 and / or the side lumens 302 ) equal to or greater than the radius of curvature of the outer wall ( or outer perimeter surface ) of an associated guide wire . fig4 shows a cross section view of a second embodiment of the present invention . in this particular embodiment , the two side lumens 402 are of a generally circular shape . and the central lumen 403 is of a “ dog bone ” shape . the top and bottom interior surfaces 405 of the central lumen of the embodiment shown in fig4 connect smoothly to the side surfaces 406 . the entire interior surface 405 406 of the central lumen 403 is free of sharp corners . the septa 404 between the two side lumens 402 and the central lumen 403 protrude into the central lumen 403 at normal atmospheric pressure , i . e ., the septa 404 are of generally concave shape . when under pressure , such as during a power injection procedure , the septa 404 are capable of deforming and may be pushed outward . the side lumens 402 , as a consequence , may have reduced size under pressure . thus , the septa 404 may adopt a convex shape under pressure . the potential to deform and expand the diameter of the central lumen 403 provides the present invention excellent flow performance when the overall exterior diameter is of a small size . the outer wall 401 of the catheter can be made thicker at the top and bottom of the central lumen than the septa 404 . this configuration would help to provide stronger mechanical strength to the exterior wall of the catheter body 220 . fig5 shows a cross section view of a catheter body of a third embodiment of the present invention . in this particular embodiment , the central lumen 503 is of an “ hour glass ” shape . the two side lumens 502 are of irregular elliptical shape having interior surfaces 508 following the general shape of the side surfaces 506 of the central lumen 506 . similar to the embodiment shown in fig4 , the septa 504 between the two side lumens 502 and the central lumen 503 protrude into the central lumen 503 under normal atmospheric pressure , i . e ., the septa 504 are of generally concave shape . when under pressure , such as during power injection procedure , the septa 504 are capable of deforming and may be pushed outward . thus , the septa 504 would adopt a convex shape under pressure . similarly , the outer wall 501 of the catheter can be made thicker at the top and bottom of the central lumen 503 than the septa 504 . this configuration would help to provide stronger mechanical strength to the exterior wall of the catheter body 220 . fig6 shows a cross section view of the catheter body of a fourth embodiment of the present invention . in this particular embodiment , instead of one side lumen on one side of the central lumen 603 , two smaller side lumens 608 609 are formed . this lumen configuration can be adapted to all embodiments of the present invention , which include , but are not limited to , the embodiments disclosed in fig3 , and 5 . for the lumen configurations shown in fig4 , and 6 , a guide wire is preferably traversed through one of the respective side lumens 402 502 602 when used to advance the catheter . the radius of curvature within the side lumen 402 502 602 is in all locations ( i . e ., at all points along the inner wall of the side lumen 402 502 602 ) equal to or greater than the radius of curvature of the outer wall ( or outer perimeter surface ) of an associated guide wire . the central lumen 303 403 503 603 of the present invention , has a large cross section ( or cross - sectional area ) relative to the available space ( or cross - sectional area ) within the body portion 220 of the catheter . because the flow rate is proportional to the fourth power of the radius of a tube , even a small increase in the cross section of the central lumen 303 403 503 603 greatly increases the flow rate achievable though the tube when all other parameters are constant . the present invention optimizes space utilization within the body portion 220 of the catheter , allowing the body portion 220 to have a relatively thick outer wall 301 401 501 601 . this increases the mechanical strength of the body portion 220 , and in turn allows a higher pressure rating for the catheter 200 . when the catheter 200 is under pressure , each of the septa 304 404 504 604 may flex outward , resultantly increasing the cross section of the central lumen 303 403 503 603 , and thereby further facilitating fluid flow . one shortcoming of existing multiple lumen catheter designs is that the exterior wall of the respective catheter tends to rupture first ( relative to other catheter walls ) when under pressure . in one aspect of the invention , the septa 304 404 504 604 of the present invention are designed to have less mechanical strength than the outer wall 301 401 501 601 of the catheter body portion 220 . in another aspect , the septa 304 404 504 604 are of a thickness less than the minimal thickness of the outer wall 301 401 501 601 . in still another aspect , the rupture characteristics of the septa 304 404 504 604 and the outer wall 301 401 501 601 are optimized by modifying both the thickness and the shape . this provides a fail - safe mechanism . in the event of catheter malfunction , such as a blockage , one or both of the septa 304 404 504 604 would be first to rupture ( relative to the outer wall 301 401 501 601 ). when a septum 304 404 504 604 breach occurs , the fluid within the central lumen 303 403 503 603 would therefore leak into a side lumen 302 402 502 602 608 609 . accordingly , the integrity of the body portion 220 of the catheter 200 is retained . this configuration effectively protects against extravastation of the fluid within the central lumen 303 403 503 603 in the event of a septa 304 404 504 604 breach . the configuration of the present invention central lumen 303 403 503 603 provides high flow rate and fail safe protection under pressure . it is , therefore , suited for power injection of diagnostic or therapeutic agents . the catheter of the present invention can be safely used at a flow rate of 5 cc / sec at 300 psi . the configuration of the lumens also provides added benefits such as kink resistance and flexibility . the lumens of the present invention catheter are intended to be used independently to deliver drugs , therapeutic or diagnostic agents . the dimensions of the lumens are not necessarily constrained in relation to one another . the cross sectional area of the central lumen 303 403 503 603 may or may not be equal to the sum of the cross sectional areas of respective side lumens 302 402 502 602 608 609 . in one embodiment of the present invention , the sum of the cross sectional areas of respective side lumens 302 402 502 602 608 609 is greater than the cross sectional area of respective central lumen 303 403 503 603 . in another embodiment , the sum of the cross sectional areas of respective side lumens 302 402 502 602 is less than the cross sectional area of respective central lumen 303 403 503 603 . the present invention catheter can be manufactured to various sizes suitable for picc applications . the unique lumen configuration of the present invention makes it possible to manufacture a triple lumen picc with small outer diameters such as french size 5 or 6 . the catheters of the present invention can be made from existing thermal plastics presently used for intravenous catheters , such as silicone and polyurethane or other tissue compatible polymers . the body portion of the catheter of the present invention can be manufactured using existing molding or extrusion manufacturing processes . placement of the catheters of the present invention also does not require any special modification to present medical procedures .
a multi - lumen catheter comprising a longitudinally extending elongated body portion , with at least two septa extending longitudinally through the entire body portion , and defining a central lumen and two side lumens . the central lumen is oblong shape in cross section and positioned between the side lumens . the septa forming the central lumen are configured to flex outwards when the central lumen is under pressure , whereby a cross sectional area of the central lumen resultantly increases to increase flow capacity through the central lumen . in some embodiments , the central lumen has a defining inner surface such that a radius of curvature of the central lumen inner surface is , in all locations , equal to or greater than a radius of curvature of an outer surface of a guide wire used for insertion of the multi - lumen catheter . the septa are each configured to fail under pressure before failure of the outer wall .