fig1 a illustrates a prior art injection device 10 which includes a dual - lumen catheter 12 and an extension piece 52 . the catheter 12 has a common tube portion 13 having a set of lumens 24 , 26 ( see fig2 a also ) and a distal end 16 which is adapted to be placed in a blood vessel of a patient . a pair of extension tubes 18 , 20 extend from a proximal end 22 of the common tube 13 with each extension tube 18 , 20 having a single lumen in communication with a respective one of the lumens 24 , 26 . the proximal end of each extension tube 18 , 20 includes a luer - type connector 6 , 8 for connection to the extension piece 52 . the extension piece 52 includes a common extension line 53 having a through lumen , a distal connector 54 connected to the extension tube 18 of the catheter through the connector 6 and a proximal connector 56 for connection to a fluid source 32 . in such a conventional injection device 10 , only one lumen of the multi - lumen catheter 12 is used to inject the contrast media . one disadvantage of such a conventional method is that the amount of fluid flow is limited due to the size of the lumen . in many instances the maximum flow rate that can be obtained is not adequate . another disadvantage of the conventional injection method is that it creates unequal pressures on the lumen walls , which causes distension of the inner septum that can lead to catheter weakening or failure . still another disadvantage of injecting through a single lumen is that the injection results in an eccentric thrust at the distal tip / end of the multi - lumen catheter . this can cause catheter tip movement or whipping . eccentric thrust is defined as an impulsive fluid force with a line of action which does not pass through the center of gravity of a body , such as a catheter , thereby causing angular acceleration which may result in a bending moment of the body . by contrast , the injection device according to the present invention involves simultaneously using multiple lumens , rather than a single lumen , of the multi - lumen catheter . one embodiment of the present invention is shown in fig1 b in which a multi - lumen picc 12 has been inserted into a patient &# 39 ; s blood vessel . the multi - lumen catheter of the present invention may be connected to a coupler device 28 / 58 capable of receiving multiple lumens , as illustrated in fig1 b and 1c . instead of the extension piece 52 , which connects to only a single lumen of the multi - lumen catheter 12 , a fluid injection device 50 of fig1 b includes a coupler device 28 which provides a fluid communication pathway between the fluid source 32 and the lumens 24 , 26 of the extension tubes 18 , 20 of the catheter 12 . in relation to the fluid source 32 , the coupler device 28 can also be viewed as a splitter device that splits the common extension line portion 29 into two separate extension lines 40 and 42 , which are in fluid communication with extension tubes 18 , 20 . in fig1 b , the coupler device 28 is a multi - lumen extension line that includes a common line portion 29 having a single lumen 30 and a proximal connector 38 for connection to the fluid source 32 , such as a contrast media injector . a pair of extension lines 40 , 42 extend from a distal end 31 of the common line 29 with each extension line 40 , 42 having a distal connector 34 , 36 that connects to the proximal connectors 6 , 8 of the catheter 12 . thus , the lumen 41 of the extension line 40 is in communication with the lumen 24 of the catheter extension tube 18 , while the lumen 43 of the extension line 42 is in communication with the lumen 26 of the catheter extension tube 20 . the coupler device 28 is connected to the multi - lumen catheter 12 so that the lumens 18 , 20 of the catheter 12 are combined into a single lumen 30 by the coupler device 28 . a fluid source 32 is connected to the coupler device 28 through the proximal connector 38 . the fluid source 32 is then turned on so that the fluid is simultaneously injected into the two lumens 24 , 26 of the multi - lumen catheter 12 . fig1 c shows an alternative injection device 60 . in this embodiment , the coupler / splitter device 58 is designed for a triple lumen catheter 64 similar to the two - lumen catheter 12 of fig1 b . the lumen 30 splits into three lumens 41 , 43 , 45 respectively contained in three extension lines 40 , 42 , 44 . these lines , in turn , are respectively in communication with three lumens 24 , 26 , 27 of the catheter extension tubes 18 , 20 , 46 . the distal connectors 34 , 36 , 37 of the coupler device 58 are connected to proximal connectors 6 , 8 , 9 of the triple - lumen catheter 64 . as can be seen , the design of the present invention can be expanded to a multi - lumen catheter of any number of lumens . the catheter of the present invention may be composed of any suitable plastic material , such as but not limited to , urethane , nylon , or silicone . the catheter may be of any useable length , i . e ., from the proximal end of the catheter 22 to the distal end of the catheter 16 , up to about 65 cm . such a device provides an increased flow rate of the fluid by delivering the fluid into all lumens of the catheter 12 simultaneously and proportionately . this can be accomplished by using a coupler 28 / 58 that connects the extension lines 40 , 42 with the extension tubes 18 , 20 , thereby providing a single continuous fluid pathway . this expands the overall flow area of the catheter 12 by the cross sectional area of the added lumen or lumens . this also increases the amount of fluid that can be delivered as is described by the controlling equation , known as poiseuille &# 39 ; s law , which states that : the hydraulic diameter d equals 4 * a / p , where a = the cross sectional area of the catheter lumen , and p equals the perimeter of the lumen . the rate of flow through a rigid tube ( q ) is equal to the fourth power of the diameter and the difference in pressure at the two ends of the tube and is inversely related to the viscosity of the fluid and the length of the tube . although this equation is accurate only for laminar flow in a rigid tube , this is a reasonable approximation for fluid flow through a catheter tube , as in the device and method of the present invention . the elasticity of the picc used in the embodiments of the present invention will result in somewhat lower actual pressures . by way of example , in the above equation , if all other parameters stay the same , an increase in the diameter of the catheter will cause the flow rate to increase . for higher viscosity fluids , increasing the diameter of the flow area will cause the flow rate to remain the same . table 1 below illustrates the effect on the flow rate of different hydraulic diameters . for example , as the cross - sectional area of the catheter increases , the flow rate increases . any suitable therapeutic fluid may be injected from the fluid source 32 into the catheter 12 using the method of the present invention . such therapeutic fluids include , but are not limited to , contrast media or dye , chemotherapeutic agents or drugs , anti - thrombotic agents , parenteral nutritional fluids , antibiotic and antiviral fluids , iv fluids , and others . these fluids may be of differing viscosities and may be injected simultaneously through different lumens of the catheter . contrast agents such as contrast media or dye may be combined with these other agents , before being injected into the catheter 12 , to provide additional clinical advantages , or alternatively , the contrast agent may be injected separately from any additional fluids . the contrast agents will mix within the blood flow once the fluid has exited from the distal end of the catheter 16 , thereby providing an enhanced contrast image . any suitable contrast media may be used . examples of contrast agents that may be used may include , but are not limited to , gadolinium , isovue ®- 370 , hexabrix - 320 , isovist - 240 , optiray - 320 , omnipaque - 350 , and ultravist - 370 , 43 % meglumine iothalamate , lohexol 240 , and 60 % meglumine iothalamate . a typical contrast media has a viscosity in the range of 0 . 07 - 0 . 11 poise . by way of example , if a contrast media with a viscosity of 0 . 10 poise were to be injected through a catheter with a 60 cm length , a flow hydraulic diameter of 0 . 0118 inches , and an injection pressure of 250 psi , the flow rate would be 5 . 6 ml / sec . if the contrast media is injected through two lumens at the same time while doubling the hydraulic diameter and keeping all other variables constant , the flow rate will increase to 11 . 2 ml / sec . alternatively , the hydraulic diameter of the catheter can be doubled by using two catheter lumens , and the flow rate can be kept the same by decreasing the amount of pressure needed to obtain the flow rate . for example , using the equation above , to obtain 5 . 2 ml / sec with a doubled diameter , a pressure of 125 psi would be needed , rather than 250 psi , to obtain the necessary flow rate . low pressure injections provide additional clinical advantages of decreased incidence of catheter weakening or failure and less potential trauma to the vein of the patient . yet another alternative to increase the flow rate would be to maintain the pressure and increase the viscosity . using fluids of higher viscosities provides an advantage in ct injections because the higher viscosity fluids provide higher contrast of images . the injection method of the present invention has advantages over current methods in that it is able to provide flow rates in excess of 6 cc / sec with a catheter that has a similar outer diameter to prior art catheters . the method allows for smaller caliber catheters to be used that would provide equal or greater flow rates than catheters of larger calibers . the benefits of smaller diameter catheters are well known . for instance , the amount of blood flow area in the vein where the catheter is placed can be increased , thereby reducing the incidence of thrombus formation , and providing less trauma to the patient . as discussed earlier , the prior art injection catheter , illustrated in fig1 a , can place excessive stress on the walls between the lumens 24 , 26 and the interior walls of the common tube portion 13 . fig2 a illustrates the excessive stress being placed ( see direction of arrows ) on the internal wall and septum 66 between the lumens 24 , 26 when the lumen 24 is being used for injection of fluid in a two - lumen catheter , while the same figure also shows the excessive stress being placed on the internal walls and septum 66 between the three lumens 24 , 26 , 27 of a three - lumen catheter . by contrast , the present injection system reduces the pressure of the fluid into the catheter , while maintaining the flow rate and increasing the diameter , which results in a substantial reduction in pressure on the catheter &# 39 ; s interior walls . as illustrated in fig2 b , the present injection device injects the fluid through all lumens of the catheter simultaneously which results in equal pressure on the internal catheter walls and septum 66 . this removes the tendency for the internal septum ( s ) 66 in the catheter , which over time may cause the catheter to distend and fail . this also allows for a thinner septum ( s ) 66 to be used , which provides more flow area and increases the catheter flow rate . fig3 a depicts the movement of the common tube portion 13 when only one lumen 24 of the catheter is used for injection . flow exits eccentrically resulting in an unequal thrust force at the distal end 16 and / or a whipping movement of the common tube portion 13 . fig3 b shows injection of a fluid through all catheter lumens 24 , 26 simultaneously . due to the equal thrust , movement of the distal end 16 remains stable . an experiment was conducted to test the distal end 16 whip effect of one lumen of a dual lumen 5f catheter ( see fig1 b ) compared to a dual lumen 5 f bifurcated catheter . a 64 % glycerin / 36 % water mixture at body temperature was separately injected at a flow rate of 2 . 5 cc / sec into both the one lumen of the dual lumen catheter and the dual lumen catheter using an e - z - em empowerct ™ injector . the water / glycerin mixture was chosen in order to simulate the viscosity of isovue ®- 370 , a common contrast agent , which has a viscosity of 9 . 4 centipoise ( cp ) at body temperature . data was recorded using a computer program called labview ™ ( available from national instruments of austin , tex .). in both the one lumen of the dual lumen catheter and the dual lumen catheter testing , the distal end 16 of the catheter 12 was unrestrained , and the injection pressure limit was set at 300 psi at the proximal end 22 of the catheter . this pressure value was chosen with the expectation that 300 psi is an upper limit of what injection pressures may reach during ct injections . when the glycerin / water fluid mixture was injected into the one lumen of a dual lumen 5f catheter at a flow rate of 2 . 5 cc / sec , the distal end 16 of the catheter 12 started whipping immediately . as fluid began flowing through the catheter 12 , the pressure , as detected at the proximal end of the catheter 22 adjusted to approximately 140 psi . the glycerin / water mixture was then injected into the dual lumen 5f bifurcated catheter 12 at the same flow rate of 2 . 5 cc / sec and initial pressure of 300 psi . as fluid began to flow through the catheter 12 , and the pressure reached about 140 psi , the distal end 16 of the dual lumen catheter 12 did not whip . the 5f catheter used in the above - mentioned experiment has an outer diameter of approximately 0 . 066 inches , a septum 66 and wall thickness each of approximately 0 . 008 inches , a lumen width of approximately 0 . 020 inches , and a lumen height of approximately 0 . 046 inches . although a 5f catheter was used in the above - mentioned experiment , a catheter of any size may be used in the method of the present invention , depending on the patient &# 39 ; s needs and the desired treatment outcomes . the internal diameter of the coupler device &# 39 ; s common line 29 is approximately 0 . 072 inches . the outer diameter is approximately 0 . 142 inches . the bifurcate coupling element 47 has an internal diameter of approximately 0 . 138 inches . the extension lines 29 , 40 , 42 , 44 on each side of the bifurcate coupling element 47 may be between approximately 2 and 12 inches in length . the total length of the coupler device 28 / 58 may be between approximately 4 . 25 and 14 . 25 inches . the dimensions of the coupler device , bifurcate coupling element , and associated tubing are given herein for illustrative purposes only . these dimensions may be adjusted depending on the patient &# 39 ; s need and the type of catheter used . however , the overall diameter of the bifurcate extension lines and coupler must be larger than the individual lumens of the catheter 12 . otherwise , the diameter of the coupler device 58 / 28 will limit the flow rate . the above disclosure is intended to be illustrative and not exhaustive . other modifications and changes in the details of the method illustrated herein can be made by those skilled in the art without departing from the spirit of the present invention . for example , multiple injectors may be used to deliver different fluids through a single catheter using the flow splitter or to vary pressures within the lumens to achieve specific flow patterns of the fluid or to direct the catheter tip in a desired location . gas injected through one lumen may also be used to displace blood , allowing a liquid agent from another lumen to fill the space left in the blood vessel by the gas displacement . all connectors 6 , 8 , 9 , 34 , 36 , 37 38 as shown in the drawings are luer type connectors although other types of connectors may be used . accordingly , the scope of the invention is not limited to the foregoing specification , but instead is given by the appended claims along with their full range of equivalents .
a fluid injection device including a multi - lumen catheter and a coupler is provided . the catheter has a common tube portion containing a set of lumens and a distal end adapted to be placed in a blood vessel . at least two extension tubes extend from the common tube portion . output connectors of the coupler are coupled to the catheter &# 39 ; s extension tubes such that they are combined into an input lumen which is coupled to a fluid source to simultaneously inject the fluid into the catheter &# 39 ; s extension tubes . the simultaneous injection of the fluid into the multi - lumen catheter &# 39 ; s extension tubes provides an even pressure on the lumen walls of the catheter , a higher flow rate and a balanced thrust at the exit of the catheter .