Patent Publication Number: US-2017368254-A1

Title: System for controlled delivery of medical fluids

Description:
RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 14/703,186, entitled “SYSTEM FOR CONTROLLED DELIVERY OF MEDICAL FLUIDS”, filed May 4, 2015, which is currently pending, which is a continuation of U.S. patent application Ser. No. 13/065,621, filed Mar. 25, 2011, entitled “SYSTEM FOR CONTROLLED DELIVERY OF MEDICAL FLUIDS”, which is now U.S. Pat. No. 9,050,401, which claims the benefit of U.S. Provisional Application Ser. No. 61/395,892, filed May 19, 2010. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a system for safely delivering a controlled volume of a medical fluid to a patient and, more particularly to a system for delivering a controlled flow of carbon dioxide (CO 2 ) or other contrast fluid in order to obtain radiological images. 
     BACKGROUND OF THE INVENTION 
     Various types of medical equipment have been utilized to deliver controlled volumes of liquid and gaseous substances to patients. One field that involves the administration of such fluids is radiology, wherein a small amount of carbon dioxide gas or an alternative contrast media is delivered to the vascular system of the patient in order to displace the patient&#39;s blood and obtain improved images of the vascular system. Traditionally, this has required that the CO 2  or other media first be delivered from a pressurized cylinder to a syringe. The filled syringe is then disconnected from the cylinder and reconnected to a catheter attached to the patient. If additional CO 2  is needed, the syringe must be disconnected from the catheter and reattached to the cylinder for refilling. Not only is this procedure tedious and time consuming, it presents a serious risk of introducing air into the CO 2  or contrast fluid at each point of disconnection. Injecting such air into the patient&#39;s blood vessels can be extremely dangerous and even fatal. 
     Recinella et al., U.S. Pat. No. 6,315,762 discloses a closed delivery system wherein a bag containing up to 2,000 ml of carbon dioxide or other contrast media is selectively interconnected by a stopcock to either the chamber of a syringe or a catheter attached to the patient. Although this system does reduce the introduction of air into the administered fluid caused by disconnecting and reconnecting the individual components, it still exhibits a number of shortcomings. For one thing, potentially dangerous volumes of air are apt to be trapped within the bag. This usually requires the bag to be manipulated and flushed multiple times before it is attached to the stopcock and ultimately to the catheter. Moreover, this delivery system does not feature an optimally safe and reliable, foolproof operation. If the stopcock valve is incorrectly operated to inadvertently connect the carbon dioxide filled bag or other source of carbon dioxide directly to the patient catheter, a dangerous and potentially lethal volume of CO 2  may be delivered suddenly to the patient&#39;s vascular system. It is medically critical to avoid such CO 2  flooding of the blood vessels. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a system for safely and reliably delivering a controlled dosage of a fluid to a medical patient. 
     It is a further object of this invention to provide a fluid (i.e. liquid or gas) delivery system that is particularly effective for use in administering CO 2  or other contrast media in a controlled manner to a patient&#39;s vascular system to provide improved contrast for radiological imaging. 
     It is a further object of this invention to provide a fluid delivery system and particularly a CO 2 /contrast media delivery system that prevents potentially dangerous amounts of air from entering the fluid and thereby being administered to the patient. 
     It is a further object of this invention to provide a fluid delivery system that prevents accidentally flooding of the patient&#39;s vascular system with carbon dioxide or other administered gases or liquids under positive pressure. 
     It is a further object of this invention to provide a fluid delivery system exhibiting a failsafe and foolproof operation, which permits only reliable and accurately controlled dosages of a medical fluid to be administered to a patient. 
     It is a further object of this invention to provide a fluid delivery system that may be used safely and effectively with virtually any source of carbon dioxide or other medical fluid regardless of the pressure or environment under which that fluid is maintained. 
     It is a further object of this invention to provide a fluid flow system that prevents an administered medical fluid from flowing in an unintended direction through the system. 
     This invention results from a realization that an improved, foolproof system for safely delivering controlled amounts of a medical fluid such as CO 2  or other contrast media to a patient may be accomplished by utilizing a multi-part valve that delivers the fluid in precisely controlled amounts sequentially through a series of syringes such that it is impossible to directly connect the fluid source to the patient. At the same time, the delivery system does not have to be disconnected and reconnected during the administration of medical fluid. This greatly reduces the intrusion of air into the system and the fluid being administered. 
     This invention features a system for controlled delivery of a medical fluid from a source of such fluid to a patient. The system includes an inlet conduit that is communicably joined to a source of the medical fluid and an outlet conduit that is communicably joined to the patient. First and second syringes are intermediate the inlet and outlet conduits. A control valve assembly interconnects the inlet and outlet conduits as well as the intermediate first and second syringes. The control valve assembly is alternatable between first, second, and third states. In the first state, the inlet communicates with the first syringe for transmitting fluid from the source to the first syringe. In the second state, the first syringe communicates with the second syringe and is isolated from the inlet and the outlet conduits for transmitting fluid from the first syringe to the second syringe. In the third state, the second syringe communicates with the outlet conduit and is isolated from the inlet conduit and the first syringe. This allows fluid to be transmitted from the second syringe to the patient through the outlet conduit. 
     In one embodiment, the valve assembly includes a valve body having aligned inlet and outlet ports that are communicably connectable to the inlet and outlet conduits respectively. The valve body further includes a pair of first and second intermediate ports that extend axially transversely to the inlet and outlet ports and transversely to each other. A stopcock is mounted rotatably within the valve body and includes an angled channel having a pair of communicably interconnected channel segments that extend axially at an acute angle to one another. The channel segments of the stopcock are interconnected at an angle that is generally equivalent to the angle formed between each adjacent pair of non-aligned ports in the valve body such that the stopcock is rotatable to align the channel segments with a selected adjacent pair of the non-aligned ports to permit fluid communication between those ports. Each of the intermediate ports is connectable to a respective syringe. The stopcock is selectively adjusted between first, second and third positions. In the first position, the channel segments communicably interconnect the inlet port and a first one of the intermediate ports. Fluid introduced through the inlet conduit portion is thereby transmitted through the inlet port and the channel of the stopcock to the first intermediate port. This port directs the fluid to a first syringe attached thereto. In the second valve position, the stopcock aligns the channel segments with the first and second intermediate ports respectively. This isolates the fluid in the first syringe from both the inlet and outlet conduits. The first syringe is operated to direct the fluid through the first intermediate port, the stopcock channel and the second intermediate port into a second syringe joined to the second intermediate port. In the third valve position, the stopcock is rotated to align the channel segments with the second intermediate port and the outlet port respectively. This isolates the fluid in the second syringe from the fluid source, the inlet port and the first intermediate port. The second syringe is then operated to drive the fluid through the second intermediate port, the channel of the stopcock and the outlet port to the outlet conduit. The outlet conduit directs this fluid to the patient. 
     The respective longitudinal axes of the inlet and outlet ports are aligned. The first and second intermediate ports may include respective longitudinal axes that form an angle of substantially 60 degrees with one another. The first intermediate port may form an axial angle of substantially 60 degrees with the longitudinal axis of the inlet port and, similarly, the axis of the second intermediate port may form an axial angle of substantially 60 degrees with the longitudinal axis of the outlet port. 
     The angular channel formed in the stopcock preferably features channel segments with respective longitudinal axes that form an angle of substantially 60 degrees. As sued herein, “substantially 60 degrees” means that the angles are either precisely or approximately 60 degrees such that the channel segments of the stopcock are communicably and selectively interengagable with a respective pair of adjoining, non-aligned ports in each of the three valve positions. Alternative angles may be features when the inlet and outlet conduits are not aligned. A lever is attached to the valve body for adjusting the stopcock between the three alternate valve positions. 
     The inlet conduit may include a fitting for sealably interconnecting to a source of medical fluid. The fitting may include a one-way valve for limiting the flow of fluid to a single direction from the source of fluid to the valve assembly and for preventing flow in the opposite direction. The inlet conduit may include coiled tubing. A second one-way valve may be mounted within the inlet port of the valve body for restricting fluid flow from the valve body to the inlet conduit. 
     The valve assembly may further include a one-way outlet valve mounted in the outlet port for restricting fluid to flow to a single direction from the outlet port to the outlet conduit and for preventing fluid flow in the opposite direction. A second coil section of tubing is formed in the outlet section. 
     The outlet conduit may carry a downstream valve for bleeding and/or purging fluid and/or for administering an additive fluid to the controlled fluid. The outlet&#39; conduit may be communicably connected to a patient catheter. An additional one-way valve may be carried by the downstream valve to restrict flow of the fluid through the downstream valve to a single direction from the outlet conduit to the patient catheter. 
     The outlet conduit may alternatively be connected to a downstream fitting having a one-way valve for directing fluid flow from the outlet conduit through the fitting to the patient. The fitting may include a port that allows fluid to be purged or flushed from the catheter. The port may also be used to deliver medications through the fitting and the catheter to the patient. The downstream fitting may be connected to a medication or fluid administering syringe through a conduit that is attached to the downstream fitting. Respective Luer™ fittings may be used to interconnect the inlet and outlet conduits to the control valve. A Luer™ fitting may also be employed to connect the downstream valve or fitting to the catheter. 
     The system of this invention may alternatively feature sequential, multiple stage delivery of a medical fluid from a source to a patient through a pair of directional or multidirectional valves. A first such valve is operated to either deliver fluid from the source to a first syringe or to deliver fluid from the first syringe to the inlet of a second valve. The second valve is then operated to selectively deliver fluid from the first syringe through the second valve to a second syringe. Alternatively, the second valve may be operated to deliver the fluid from the second syringe to the downstream catheter or patient. A critical feature of this invention is that a precise volume or dosage of CO 2  or other medical liquid/gas is delivered sequentially in three distinct stages from the source to the patient. In each stage, the source, which is typically under pressure, remains totally isolated from the patient so that fluid is administered much more safely than in prior systems. 
     This invention further features a process for delivering medical fluid from a source of such fluid to a patient in controlled doses. The process involves providing inlet and outlet conduits that are connected respectively to a source of medical fluid and a patient. A control valve assembly and a pair of first and second syringes are interconnected between the inlet and outlet conduits. The control valve assembly is first operated to communicably join the fluid source and the first syringe and medical fluid is transmitted from the source to the first syringe. The control valve assembly is then adjusted to communicably join the first and second syringes while isolating the first syringe and the second syringe from the source of fluid. The first syringe is then operated to transmit medical fluid from the first syringe to the second syringe through the control valve assembly. The second syringe and the outlet conduit are then communicably joined by further adjusting the control valve assembly and the second syringe is operated to transmit medical fluid from the second syringe to the patient through the outlet conduit. The first syringe and the fluid source remain isolated from the second syringe. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Other objects, features and advantages will occur from the following description of a preferred embodiment and the accompanying drawings, in which: 
       FIG. 1  is a somewhat simplified plan and partly schematic view of the system for controlled delivery of medical fluids in accordance with this invention; 
       FIG. 2  is a view similar to  FIG. 1  wherein the control valve assembly is enlarged for clarity and the internal construction of the valve assembly is illustrated; 
       FIG. 3  is a simplified, schematic view of the outlet conduit and an alternative downstream fitting that may be used to interconnect the outlet conduit to the patient catheter; 
       FIG. 4  is a view similar to that of  FIGS. 1-3  which depicts a medication administering syringe being attached to the downstream fitting by means of a connecting tube; 
       FIG. 5  is a perspective view of a control valve assembly featuring a dual handle for operating the stopcock and indicating which pair of flow ports are open; 
       FIG. 6  is an elevational and partially schematic view of an alternative system in accordance with this invention utilizing a pair of multidirectional valves for the control valve assembly; and 
       FIG. 7  is a perspective view of the multidirectional valves used in the embodiment of  FIG. 5 . 
    
    
     There is shown in  FIGS. 1 and 2  system  10  for delivering controlled dosages of a medical contrast fluid such as carbon dioxide (CO 2 ) for use in the radiological imaging of arteries and veins of a patient&#39;s vascular system. Although this is a preferred application for system  10 , it should be understood that the system may be used for the controlled delivery of various other types of liquids and gases administered as part of assorted surgical and medical procedures. As used herein, the term “fluid” should be understood to include various types of medical liquids and gases. By the same token, when “gas” is used herein, it should be understood that such description is likewise applicable to various types of medical liquids. 
     System  10  includes an inlet conduit  12  and an outlet conduit  14  interconnected by a three-stage K-valve shaped control assembly  16 . Inlet conduit  12  communicably interconnects a source of carbon dioxide or other medical fluid (not shown) with valve assembly  16 . Outlet conduit  14  likewise communicably interconnects a discharge end of valve assembly  16  with a catheter  18  that is, in turn, operably connected to a patient, not shown. 
     Inlet conduit  12  includes a Luer™ fitting  20  having a G-tube seal  22 , which is selectively attached to the source of medical fluid, such as the CO 2  source. It should be understood that system  10  may be used with various sources of carbon dioxide including, but not limited to, pressurized tanks, bags and the CO 2 mmander® manufactured by PMDA, LLC of North Fort Myers, Fla. The specific source of carbon dioxide or other medical fluid is not a limitation of this invention. A one-way directional valve  24  with a Luer™ fitting  26  is communicably joined to fitting  20 . Fitting  26  is, in turn, communicably joined to a coiled medical tube  28  having a length of approximately 18″. Various alternative lengths may be employed within the scope of this invention. The distal end of tube  28  carries a Luer™ fitting  30 . 
     Three-stage control valve assembly  16  includes a generally K-shaped valve body  32 , which is preferably composed of various medical grade plastics, metals and/or metal alloys. Typically, the valve body includes a molded or otherwise unitary construction. The valve body features four fluid transmitting ports  38 ,  46 ,  48  and  40 . More particularly, valve body  32  includes aligned intake and discharge segments  34  and  36 , respectively, which, as best shown in  FIG. 2 , include respective aligned internal inlet and outlet ports  38  and  40  respectively. The valve body also includes first and second transverse legs  42  and  44 . Each leg extends at an angle of substantially 60 degrees from aligned branches  34  and  36  of valve body  32 . Leg  42  includes an interior intermediate port  46  and leg  44  includes an interior intermediate port  48 , which extend axially longitudinally through the respective legs  42  and  44 . Ports  46  and  48  form transverse angles of substantially 60 degrees apiece with respective axial ports  38  and  40  of aligned branches  34  and  36 . 
     Transverse legs  42  and  44  also extend at an angle of substantially 60 degrees to one another. By the same token, the longitudinal axes of ports  46  and  48  form an angle of substantially 60 degrees. 
     Valve assembly  16  further includes a stopcock  59  that, best shown in  FIG. 2 , which is rotatably mounted within valve body  32 . The stopcock includes an angled channel  61  comprising communicably interconnected channel segments  63  and  65  having respective longitudinal axes that extend at an angle of approximately 60 degrees to one another. As used herein, “approximately 60 degrees” should be understood to mean that angle formed between the respective longitudinal axes of the channel segments  63 ,  65  is substantially equivalent to the angle formed between the longitudinal axes of respective pairs of the non-aligned adjacent ports of valve body  32  (e.g. respective pairs of ports  38 ,  46 ;  46 ,  48 ; and  48 ,  40 ). This enables the channel segments to be communicably aligned with a selected adjacent pair of the ports in the manner described more fully below. It should be understood that in alternative embodiments the ports and channel segments may have other corresponding angles. This is particularly applicable when the intake and discharge ports and/or the inlet and outlet conduits are not aligned. 
     As shown in  FIG. 1 , a valve lever  67  is mounted to valve body  32  for selectively rotating stopcock  59  into a selected one of three positions. For example, in  FIG. 2 , the stopcock is positioned with channel segments  63  and  65  of angled channel  61  communicably aligned with adjacent ports  38  and  46  respectively. Alternately, and as described more fully below, lever  67  may be manipulated to align the channel segments  63 ,  65  with respective ports  46  and  48  as indicated by the channel shown in phantom in position  61   b.  The lever may be likewise operated to align the respective channel segments with ports  48  and  40  as indicated by the angled channel (shown cross-hatched) in position  61   c.  Such selective positioning of the stopcock provides for controlled multiple stage delivery of fluid through valve  16  from inlet conduit  12  to outlet conduit  14 . This operation is described more fully below. 
     Intake branch  34  of valve body  32  carries a complementary fitting for communicably interconnecting to Luer™ fitting  30  carried at the distal end of tubing  28 . By the same token, discharge branch  36  of valve body  32  carries a complementary fitting for operably and communicably interconnecting with a Luer™ fitting  50  carried at the proximal end of outlet conduit  14 . The remaining elements of the discharge conduit are described more fully below. Aligned ports  38  and  40  of valve body  32  include respective one-way valves  52  and  54 ,  FIG. 2 , which restrict or limit the flow of fluid within respective ports  38  and  40  to the direction indicated by arrows  56  and  58 . 
     As further illustrated in  FIGS. 1 and 2 , outlet conduit  14  features a coiled medical tube  60  that is communicably interconnected between the Luer™ fitting  50  attached to discharge branch  36  of valve body  32  and a second Luer™ fitting  62 , which is communicably joined to a downstream valve  64 . The downstream valve includes a one-way valve  66  that restricts fluid flow from tubing  14  through valve  64  to the direction indicated by arrow  68 . Valve  64  features a G-tube seal  73  that prevents air from intruding into the system prior to connection of valve  64 . Valve  64  also includes a stopcock  70  that is rotatably operated within valve  64  to selectively bleed or purge fluid from system  10  through a port  72 . Exit port  74  is selectively joined to patient catheter  18 . Various alternative two and three port stopcocks may be used in the downstream valve. 
     A reservoir syringe  80  is communicably connected to axial port  46  of valve leg  42 . Such interconnection is accomplished by a conventional Luer™ fitting  82 , the details of which will be known to persons skilled in the art. Similarly, a second, draw-push syringe  84  is releasably attached by a Luer™ fitting  86  to the distal end of valve leg  44 . This allows syringe  84  to be communicably interconnected with port  48  through second transverse leg  44 . Syringes  80  and  84  are constructed and operated in a manner that will be known to persons skilled in the art. 
     System  10  is operated to deliver CO 2  or other medical fluid to a patient in a controlled and extremely safe and reliable manner. This operation is performed as follows. 
     Inlet conduit  12  is first interconnected between a source of carbon dioxide and intake branch  34  of valve body  32 . Outlet section  14  likewise is communicably interconnected between discharge branch  36  of valve body  32  and downstream valve  64 , which is itself attached to patient catheter  18 . Syringes  80  and  84  are joined to valve legs  42  and  44  such that the syringes communicate with respective ports  46  and  48 . The syringes should be selected such that they have a size that accommodates a desired volume of gas to be administered to the patient during the radiological imaging or other medical/surgical procedure. 
     After multistage K-valve assembly  16  has been interconnected between the inlet and outlet conduit  12  and  14 , and following attachment of syringes  80  and  84  to respective valve legs  42  and  44 , stopcock  59  is operated by valve lever  67  to align legs  63  and  65  of stopcock channel  61  with valve ports  38  and  46  respectively. See  FIG. 2 . The source of CO 2  is then opened or otherwise operated as required to deliver gas through inlet conduit  12  to valve  16 . More particularly, the gas is delivered through one-way valve  24  and tubing  28  to the inlet port  38 . One-way valve  52  prevents backflow of gas into the coil tubing  28 . The CO 2  proceeds in the direction indicated by arrow  56  and is transmitted through angled stopcock channel  61  into port  46  of valve leg  42 . From there, the gas proceeds as indicated by arrow  90  through the fitting  82  and into reservoir syringe  80 . The CO 2  is introduced into reservoir syringe  80  in this manner until it fills the syringe. 
     When reservoir syringe  80  is filled, the operator manipulates lever  67 ,  FIG. 1 , and rotates the control valve into the second stopcock channel position represented in phantom by  61   b  in  FIG. 2 . In that position, channel segment  63  is communicably aligned with port  46  and channel segment  65  is communicably aligned with port  48 . The plunger  81  of reservoir syringe  80  is pushed and the gas previously deposited into syringe  80  is transmitted through port  46  and the angled stopcock channel  61   b  into port  48 . From there, the gas is introduced into draw-push syringe  84  as indicated by arrow  92 . As this operation occurs, only the transverse, intermediate ports and their attached syringes are communicably connected. Both syringes remain completely isolated from both the inlet port  38  and the discharge or outlet port  40 . By the same token, the source of carbon dioxide and communicably joined port  38  are isolated from discharge port  40  and the outlet conduit  14  connected to catheter  18 . The patient is thereby safely protected against being inadvertently administered a dangerous dosage of carbon dioxide directly from the source. 
     After the gas is transferred from reservoir syringe  80  to push-draw syringe  84 , the operator manipulates valve lever  67  to rotate stopcock  59  to the third position, which is represented by the stopcock channel in position  61   c.  Therein, channel segment  63  is communicably aligned with port  48  and channel segment  65  is similarly aligned with channel segment  40 . To administer the CO 2  in syringe  84  to the patient, plunger  83  of syringe  84  is depressed in the direction of arrow  96 . Gas is thereby delivered through port  48  and stopcock channel into port  40 . From there, the gas passes in the direction indicated by arrow  58  through one-way valve  54  and into tubing  60 . CO 2  is thereby transmitted in the direction indicated by arrow  58  through one-way valve  54  and into tubing  60  of outlet section  14 . One-way valve  54  prevents backflow of gas into the K-valve assembly. 
     Lever  67  may be configured as an arrow or otherwise marked to include an arrow that points in the direction of the intended fluid flow. With the lever pointing toward reservoir  80 , as shown in  FIG. 1 , the angled channel  61  is in the position shown in  FIG. 2  and fluid flow is directed toward reservoir  80 . Alternatively, the lever may be rotated to point toward syringe  84 . In this position, the channel is in the position  61   b  shown in  FIG. 2  and CO 2  is directed from syringe  80  to a syringe  84 . Finally, in the third stage of the process, lever  67  may be directed to point toward the discharge end of port  40  and the attached outlet section  14 . In this stage, angled channel  61  is directed to the position  61   c , shown in  FIG. 2 , such that fluid flow is directed from reservoir  84  to the outlet section  14 . 
     CO 2  is delivered through tube  60  and into downstream valve  64 . Once again, a one-way valve  66  prevents the backflow of gas into the tubing. Stopcock  70  is operated, as required, to either direct the CO 2  to catheter  18  and thereby to the patient, or to purge the gas through port  72 . The G-tube seal  73  prevents air from entering the line. 
     Accordingly, system  10  enables controlled amounts of CO 2  to be delivered to the patient in a safe and reliable manner. After the components are connected, they may remain connected during the entire medical procedure and do not then have to be disconnected and reconnected. This minimizes the possibility that air will intrude into the system and endanger the patient. Controlled and precise dosages of CO 2  are delivered, by the simple and foolproof operation of valve  16 , from reservoir syringe  80  to push-draw syringe  84  and then to the patient. At each stage of the process, the inlet and outlet ends of the valve remain totally isolated from one another so that the risk of administering an explosive and potential deadly dose of CO 2  is eliminated. 
       FIG. 3  again discloses the discharge branch  36  of valve assembly  16 . A one-way valve  54  is again installed in port  40  to prevent backflow of gas into valve assembly  16 . In this version, tube  60  is communicably connected between discharge branch  36  and a fitting  100  that may be used selectively to perform various functions. In particular, fitting  100  includes a one-way valve  102  that prevents backflow of gas into tube  60 . Fitting  100  includes a Luer™ fitting  104  that allows fitting  100  to be releasably attached to catheter  18 . A flush port  106  is communicably joined with fitting  100  and features a G-valve seal  108  that permits a syringe (not shown) to be interconnected to port  106 . This syringe may be used to administer medications through fitting  100  to attached catheter  18 . As a result, such medications may be administered to the patient without having to disconnect the individual components of the fluid delivery system. This saves valuable time in a surgical or medical environment and reduces the risk that air will be introduced into the system. A syringe may also be attached to port  106  to purge or flush the catheter as needed or desired. 
       FIG. 4  depicts still another embodiment of this invention wherein medical tube  60  is communicably interconnected between the discharge branch  36  of valve assembly  16  and a fitting  100   a.  The downstream fitting again includes a one-way valve  102   a  for preventing the backflow of gas or medication into tube  60 . A Luer™ fitting  104   a  releasably interconnects fitting  100   a  to catheter  18 . An inlet/discharge port  108   a  is formed in fitting  100   a  for selectively introducing medication into the patient catheter through fitting  100   a  or alternatively purging or flushing the catheter as required. A line  110  is communicably connected to port  108   a  and carries at its opposite end a Luer™ fitting  112  for releasably attaching the line to a syringe  114 . The syringe is attached to line  100  through fitting  112  in order to optionally deliver medication to catheter  18  through fitting  100   a  in the direction indicated by arrow  116 . Alternatively, fluid may be purged or flushed in the direction of arrow  121  from the catheter and/or from the system through line  110  by drawing plunger  120  of syringe  114  rearwardly in the directions indicated by arrow  122 . 
     In alternative versions of this invention, medical fluid may be transmitted from a source to a patient in multiple stages, as described above, but utilizing multiple valves joined to respective syringes. In particular, in a first stage operation, gas or other fluid under pressure is delivered from the source through a first directional valve to a reservoir syringe communicably connected to the first valve. The reservoir syringe is also connected through the first valve to a second valve which is, in turn, communicably joined to a second syringe. The first valve is operated so that the reservoir syringe remains isolated from the second valve as fluid is delivered from the source to the first syringe through the first valve. When a selected volume of fluid is accommodated by the first syringe, the first valve is operated to connect the first syringe with the second valve. The second valve itself is operated to communicably connect the first syringe to the second syringe while, at the same time, isolating the second syringe from the patient. The second syringe is a push-draw syringe. The first syringe is operated with the second valve in the foregoing position to transmit the fluid from the first syringe to the second syringe. During this stage of the operation, both syringes remain isolated from the source and the patient. As a result, even if fluid under pressure is “stacked” in the reservoir syringe, this pressure is not delivered to the patient. Rather, the desired volume of the fluid is delivered instead to the push-draw syringe. The second valve is then operated to communicably join the push-draw syringe to the patient/patient catheter. Once again, the patient/catheter are totally isolated from the source of fluid under pressure. As a result, a safe and selected volume of fluid is delivered from the push-draw syringe to the patient. 
     Various valve configurations and types of directional valve may be employed to perform the multi-stage delivery described above. In all versions of this invention, it is important that fluid first be delivered from a fluid source to a first syringe and then delivered sequentially to a second syringe. Ultimately, the fluid in the second, push-draw syringe is delivered sequentially to the patient. During each stage of the process, the source of fluid remains isolated from the patient. Typically, only one stage of the system operates at any given time. 
     There is shown in  FIG. 5  an alternative control valve assembly  16   a,  which again features a generally K-shaped valve body  32   a  composed of materials similar to those previously described. Aligned inlet and outlet conduit segments  34   a  and  36   a,  as well as transverse or angled conduit segments  42   a  and  44   a  are selectively interconnected to communicate and transmit fluid flow through respective pairs of the conduits by a rotatable stopcock valve analogous to that disclosed in the previous embodiment. In this version, the stopcock is rotated by a dual handle lever  67   a,  which includes elongate handles  69   a  and  71   a.  These handles diverge from the hub of the stopcock lever at an angle of approximately 60 degrees, which matches the angle between each adjacent pair of fluid transmitting conduits  34   a,    42   a,    44   a  and  36   a  in control valve  16   a.  Each of handles  69   a  and  71   a  is elongate and carries a respective directional arrow  73   a  that is printed, embossed or otherwise formed along the handle. 
     Valve lever  67   a  is turned to operate the stopcock such that a selected pair of adjoining conduits or ports are communicably interconnected to permit fluid flow therethrough. In particular, the stopcock is constructed such that the handles  69   a  and  71   a  are aligned with and extend along respective conduits that are communicably connected by the stopcock. In other words, the valve lever  67  is axially rotated until handles  69   a  and  71   a  are aligned with adjoining conduits through which fluid flow is required. The angle between the handles matches the angle between the adjoining conduits, e.g. 60 degrees. Lever  67   a  may therefore be rotated to align diverging handles  69   a  and  71   a  respectively with either conduits  34   a  and  42   a,    42   a  and  44   a,  or  44   a  and  36   a.  In  FIG. 5 , the handles are aligned with conduits  44   a  and  36   a,  and arrows  73   a  point in a direction that is substantially aligned with those conduits. This indicates that the valve lever  67   a  is rotated and adjusted such that fluid is able to flow through valve body  32   a  from transverse conduit  44   a  to outlet conduit  36   a.  The valve lever is rotated to selectively align with the other pairs of conduits and thereby open the fluid flow between the selected pair. The use of a dual handle valve lever  67   a  clarifies and facilitates usage of the control valve assembly. Otherwise, the valve lever employed in the version of  FIG. 5  is constructed and operates analogously to the valve lever disclosed in  FIGS. 1-3 . 
       FIG. 6  depicts a system  210  in accordance with this invention wherein the control valve assembly comprises a pair of multidirectional valves  216  and  316 , shown individually in  FIG. 6 . These valves are utilized to perform multi-stage delivery of a medical gas such as CO 2  or other medical fluid to a patient in a manner analogous to that previously described. Valves  216  and  316  comprise standard multidirectional valves of the type manufactured by Value Plastics, which are suitable for use in medical applications. Such valves respond automatically to a predetermined fluid pressure by allowing fluid flow through at least one path of the valve and restricting such flow through at least one other path of the valve. The construction of such multidirectional valves will be understood to persons skilled in the art. 
     Valve  216  includes ports  219 ,  221  and  223  that are communicably interconnected in a T-shaped configuration. Valve  316  similarly includes ports  319 ,  321  and  323  that are communicably interconnected in a T-shaped configuration. Port  323  comprises a Luer connector having a locking nut  331  carried thereon. 
     More particularly, port  223  of valve  216  typically comprises a male Luer fitting that is attached to a Luer lock  225  carried at the discharge end of a first, reservoir syringe  280 . Inlet port  219  is interconnected through a one way check valve  227  to an inlet conduit  212 . The opposite end of that inlet conduit is communicably joined to a pressurized supply of medical fluid in a manner analogous to that previously described. Third port  221  of valve  216  is press fit into port  319  of second multidirectional valve  316 . Port  321  of valve  316  is attached to a Luer lock  351  formed at the discharge end of a second, push-draw syringe  384 . Locking nut  331  of Luer outlet port  323  allows valve  316  to be connected to a complementary Luer fitting  357  of a downstream directional valve  364 . The downstream directional valve comprises a rotary valve that also includes ports  359  and  361 . These ports are selectively interconnected to port  357  within the body of valve  364  and collectively define a T-shaped configuration. A directional valve lever  373  is rotated as needed to communicably align two of the respective ports. More particularly, the handle of the lever is directed along and aligned with a selected one of the ports  357 ,  359  and  361  to close that port such that the other ports communicate in a known manner. 
     Port  359  of valve  364  is itself communicably interconnected through a standard Luer fitting  381  to a line  383 . Port  361  is likewise communicably joined through a Luer fitting  385  to a one-way directional valve  366 , which is itself connected to an outlet conduit, i.e. a catheter  318 , leading to the patient. 
     Downstream directional valve  364  is operated, as required, to either bleed or purge excess gas from system  210  (i.e. by turning handle  373  upwardly and aligning it with port  361 ) or to deliver a selected medication dosage, contrasting agent or other radioscopic substance to the patient (i.e. by rotating handle  373  downwardly and aligning it with port  357  so that line  383  and catheter  318  are communicably joined). Downstream directional valve  364  is adjusted in a rotatable manner that will be known to persons skilled in the art. That valve may be utilized for various functions within the scope of this invention. It should also be understood that various other types of locking, sealing and/or communicative connections may be employed between the respective components of system  210 . 
     System  210  is operated to deliver medical gas or other fluid to a patient in the following manner. In a first stage operation, gas or other fluid under pressure is delivered from the source or supply (as previously described) to reservoir syringe  280  by connecting the supply to conduit  212  and opening the supply. CO 2  or other medical fluid under pressure is delivered through inlet conduit  212  and check valve  227  into port  219  of multidirectional valve  216 . The multidirectional valve is constructed and operates in a known manner such that the pressurized medical fluid effectively opens the valve to interconnect ports  219  and  223 . The fluid therefore is transmitted through Luer fitting  225  into the reservoir of first syringe  280  and the plunger P 1  of the syringe retracts in the direction of arrow  291 . 
     When reservoir syringe  280  is filled, the operator depresses plunger P 1  in a conventional manner. This pushes the fluid from the reservoir of syringe  280  back through port  223  of valve  216 . The pressure created by depressing the plunger P 1  causes multidirectional valve  216  to open a communicating pathway between port  223  and aligned port  221 . The medical fluid from first syringe  280  is thereby pushed through valve  216  and delivered from port  221  to port  319  of second multidirectional valve  316 . At the same time, check valve  227  prevents fluid from being transmitted back through inlet conduit  212  to the gas or liquid supply. 
     When fluid under pressure is delivered through port  319  to valve  316 , the second multidirectional valve opens a communicating pathway between ports  319  and  321 . The medical fluid is accordingly transmitted through those interconnected ports and through Luer fitting  351  to the reservoir of second, push-draw syringe  384 . In the second stage of the process, the fluid is delivered from first syringe  280  to second syringe  384  while remaining isolated from the fluid supply. The plunger P 2  of the second syringe retracts in the direction of arrow  295  as its reservoir is filled. Valve  316  restricts the flow of fluid during this stage to the pathway defined by interconnected and communicating conduits  319  and  321 . 
     The third stage of the process is completed by depressing plunger P 2 . This causes valve  316  to open a communicating flow path between ports  321  and  323  and restricts the gas or liquid from being transmitted back through port  319 . Valve  316  transmits the fluid from syringe  384  through downstream directional valve  364  and check valve  366  to catheter  318 . During this third stage of the process, handle  373  is typically pointed toward and aligned with port  359  so that ports  357  and  361  of valve  364  are communicably connected. Handle  373  is depicted as pointed in a “nine o&#39;clock” position in  FIG. 6  for purposes of clarity and in order to better illustrate the ports of valve  364 . By operating syringe  384 , a selected dosage of medical gas or liquid is delivered through catheter  318  to the patient. 
     Valve  364  is operated, in a manner previously described, to perform desired functions in connection with a radioscopic procedure. For example, to add a medication or radioscopic compound (such as a contrasting substance), handle  373  is typically pointed downwardly (in a “six o&#39;clock” position) so that ports  359  and  361  are communicably joined. The desired substance to be added is then introduced through line  383  and valve  364  to catheter  318 , and is thereby administered to the patient. Alternatively, gas may be purged or bled from the system by turning handle  373  such that it points toward and is aligned with port  361  and catheter  318 . This communicably interconnects ports  357  and  359  so that excess gas may be discharged through line  383 . Accordingly, in either of the embodiments of this invention, the system may be quickly and conveniently purged and/or medication may be added to the administered gas in a quick and convenient manner. In each case, the system does not have to be disconnected, disassembled and/or reassembled. This saves considerable time and effort and greatly reduces the possibility of air intruding into the system. 
     System  210  may be modified to include particular features and components as described in the embodiment of  FIGS. 1-4 . In addition, the particular means of component interconnection, sealing, and valve operation may be modified in a manner that will be understood by persons skilled in the art in order to obtain the manner of operation and resulting benefits exhibited by this invention. 
     The use of multiple syringes is particularly critical and eliminates the risk of stacking that often occurs when a medical fluid is delivered under pressure directly from a source of fluid to a single delivery syringe. In that case, the syringe may be filled with fluid that exceeds the nominal volume of the syringe due to pressure stacking. If such fluid were to be delivered directly to the patient, this could result in a potentially dangerous overdose or fluid flooding. By transmitting the fluid from a reservoir syringe into a second, push-draw syringe, the pressure is equalized and only the fluid volume and pressure accommodated by the second syringe are delivered safely to the patient. 
     From the foregoing it may be seen that the apparatus of this invention provides for a system for safely delivering a controlled volume of a medical fluid to a patient and, more particularly to a system for delivery a controlled flow of carbon dioxide (CO 2 ) or other contrast media in order to obtain radiological images. While this detailed description has set forth particularly preferred embodiments of the apparatus of this invention, numerous modifications and variations of the structure of this invention, all within the scope of the invention, will readily occur to those skilled in the art. Accordingly, it is understood that this description is illustrative only of the principles of the invention and is not limitative thereof. 
     Although specific features of the invention are shown in some of the drawings and not others, this is for convenience only, as each feature may be combined with any and all of the other features in accordance with this invention. 
     Other embodiments will occur to those skilled in the art and are within the following claims: