Abstract:
The present invention describes IV regulators that allow interruption of normal controlled-flow for a safe and convenient bolus flush, either for a specific period of time or for a specific volume of saline flush. Two time-controlled IV regulators are shown, one employing a pneumatic cylinder counter-opposed by elastic band(s) for administering a bolus flush, and one employing a compressible lever and torsion spring counter-opposed by a rotary damper. In both cases the mechanisms disengage the roller-clamp from the IV tube for a predetermined amount of time to fully open fluid flow there through for a bolus flush before return to the regulated-flow position. The volume-controlled flow regulator employs two internal bladders and allows one bladder to fill while the other bladder drains (and vice versa) by flipping a slider paddle-type toggle, thus enabling the administration of a set volume of flush fluid.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application derives priority from U.S. provisional application Ser. No. 60/851,856 filed 13 Oct. 2006. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to flow regulators for intravenous (IV) equipment and, more particularly, to a manually-operated regulator that allows interruption of normal controlled-flow for a safe and convenient bolus flush (full flow of saline for a specific period of time or volume of flush) before returning to a “pre-flush” flow setting, eliminating the need to manually reset the roller regulator or to administer a separate saline flush. 
     2. Description of the Background 
     Intravascular or IV sets deliver fluid, medications, blood products and parenteral nutrition to patients. Most IV machines operate by gravity or by an infusion pump (a pump, usually peristaltic, used to control the flow through the IV tube).  FIG. 14  is a perspective view of a conventional IV administration set, which includes an injectable solution bag, opening to a drip chamber, connected by flexible tubing to a roller-clamp and on to a catheter adapter which can be coupled to a catheter for administration to a patient. Intravenous therapy is a complex process usually requiring the preparation of machine, IV lines and medicine before administration to the patient. This involves a number of considerations, such as air or gas bubble detection, gas removal, and flow rate control. Roller-clamps as in  FIG. 14  are the most widely used flow control device. The roller-clamp comprises a wheel trapped within a housing that compresses the IV tubing as it is slid along a gradual ramp. The flow rate is calculated by counting drops in a drip chamber. The infusion can be driven by gravity alone, or by an electronic infusion pump. The US market for roller-clamp-type IV administration sets is estimated at 1.4 billion dollars. 
     To administer a drug into a patient using an existing IV set with a roller-clamp regulator, the drug is typically injected into the IV upstream (proximal) of where it enters the patient&#39;s body. Methods of administering IV medication may include giving the medication intermittently over a specific amount of time using a secondary IV line, or giving the medication continuously mixed in the main IV solution. IV push medication techniques deliver a bolus (a dose of medication injected all at once intravenously) of medication directly into a vein or access port to produce an immediate peak drug level in the patient&#39;s bloodstream. A bolus injection is most often given through a peripheral IV line, a saline lock, or through a vascular access port. After injection, a saline “flush” is necessary to ensure delivery of the medicine to the patient&#39;s circulation. To accomplish a flush, one of two methods is typically employed. First, the user may open the roller-clamp to full flow for a brief period of time, then return it to the desired setting once the drug has been flushed into the circulation. This method leaves open the possibility that the user will forget to return the clamp to the pre-flush setting, thus causing the accidental administration of a large volume of IV fluid (an event which at best is embarrassing but innocuous, and at worst fatal). A second method of administering a flush is to draw up a separate syringe of flush solution (typically saline). The separate saline flush is administered as a “chaser” through the same port as the injected medicine. This method is fraught with its own problems ranging from wasteful use of supplies to infection control issues. 
     Manufacturers are approaching this problem by trying to develop computerized IV machines that can administer preprogrammed amounts of saline chasers. These devices include a twin-head injector equipped with two syringes, one for saline and one for medication. The devices can be preprogrammed to control the quantity and injection rate of both medication and saline. For example, U.S. Pat. No. 6,641,562 to Peterson (HPS Medical, Inc.) issued Nov. 4, 2003 shows an apparatus and method of intravenous fluid infusion that uses a microcomputer to cyclically drive a fluid control module which outputs a fixed amount of medicine for each cycle of operation. Unfortunately, this and like systems are far more complicated than the classic roller regulator, more expensive and difficult to use. Moreover, they do not supplant the need for the traditional manual roller-clamp regulator which is still used to regulate the flow rate at baseline. 
     Given the problems associated with the traditional manner of administering a saline flush, it would be much more advantageous to provide a purely mechanical (or electromechanical) device (either incorporated into or separate from the roller-clamp) capable of delivering a saline flush following a bolus of medication. 
     The foregoing has been attempted in one known case. U.S. Pat. No. 6,500,156 to Stansbury (McKinley Medical L.L.L.P) issued Dec. 31, 2002 shows a thumb-powered flushing device for catheters in which a chamber is covered with a flexible diaphragm that can be compressed by exertion of pressure on the diaphragm to propel fluid through the catheter, and a valve that regulates flow into and out of the chamber beneath the movable member that pumps fluid to deliver a bolus of medication, or to flush the catheter. Unfortunately, the thumb-pump action is hard to control and the amount of flush dosage delivered is at the mercy of the coordination of the user&#39;s thumb. This only marginally solves the aforesaid problem in administering a calibrated dosage of saline IV flush, and consequently has not been widely adopted. 
     It would be greatly advantageous to provide a simple manually-operated mechanism capable of easy integration into otherwise-conventional roller-clamp regulators that will administer an accurate flush by allowing full flow of saline for a specific period of time (or volume) before returning to a “pre-flush” setting, eliminating the need to change the setting of the roller-clamp regulator or to administer a separate saline flush injection. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a purely mechanical IV flush device capable of delivering a saline flush, in a safe and convenient manner. 
     It is another object to provide three different embodiments of an IV flush device, two of which allow interruption of normal controlled-flow for a safe and convenient bolus flush (full flow of saline or other carrier fluid) for a specific period of time, and the third of which allows a like interruption for a specific volume of saline flush. 
     It is another object to provide IV devices as described above that accomplish a semi-automatic flush using components and a form factor that are as similar as possible to existing commercial roller-clamp regulators, thereby giving a familiar look and feel to doctors and nurses in order to encourage widespread adoption. 
     In accordance with the foregoing objects, the present invention provides three embodiments of an IV regulator: two of which allow interruption of normal controlled-flow for a safe and convenient bolus flush for a specific period of time, and the other of which allows a like interruption for a specific volume of saline flush. 
     One of the time-controlled IV regulators generally comprises an elongated housing seating a roller-clamp, and through which the IV tuning passes. The housing also includes a pneumatic cylinder (much like a syringe) with a pressure chamber and plunger slidably loaded into the pressure chamber. A pair of elastic bands bias the plunger upward inside the housing. To administer a bolus flush, the plunger is thumb-depressed downward and air is freely inducted into the pressure chamber (through a check valve). This disengages the roller-clamp and allows free flow for a bolus flush. When released, the plunger is biased back by the rubber bands and eventually reengages the roller clamp (after a predetermined time interval), thereby resuming controlled flow. 
     The second time-controlled IV regulator generally comprises a main housing section having an IV tube running through it, a roller-clamp rotatably seated in the main housing section, and a compressible handle pivotally mounted to the main housing section at a pivot pin and extending past to selectively engage the roller-clamp. A torsion spring is mounted on the pivot pin to bias the compressible lever toward a normally closed position (which engages the roller-clamp), thereby allowing adjustment of the flow rate through the IV tube. In addition, a rotary damper is engaged to the compressible lever to oppose the torsion spring bias for a predetermined amount of time, thereby allowing the compressible lever to pivotally disengage the roller-clamp from the IV tube and fully open fluid flow for a time-controlled flush before returning to the regulated flow-controlled position. 
     The volume-controlled flow regulator generally comprises an enclosed housing having an inlet at one end for entry of a pair of IV tubes, and an outlet at the other end for egress of a pair of IV tubes. A pair of expandable/collapsible bladders are resident in the housing, each bladder being connected endwise between two of the IV tubes. In addition, a slider paddle is pivotally mounted to the housing and is pivotable between two positions, one clamping off the tube above one bladder and opening the tube from below that bladder, thereby allowing that bladder to drain. At the same time the slider paddle opens the inlet tube to the other bladder and clamps off its outlet tube allowing it to fill. The slider paddle is pivoted to a second position reversing the fill/drain operation of the bladders. A regular IV flow can be maintained through a roller-clamp regulator either in series with (above) the present device or in parallel with it. When a medicine is then delivered into the line distally, the slider paddle can be pivoted to empty the full bladder, thereby safely administering a bolus flush of saline in a prescribed volume. 
     All of the foregoing embodiments allow interruption of normal regulated flow for a safe and convenient bolus flush (full flow of saline), the first two for a specific period of time, and the third for a specific volume of saline flush, before returning to a “pre-flush” normal flow setting. This simplifies the process of administering a bolus medicine followed by a saline flush. Furthermore, it improves safety, eliminates over flushing, and decreases costs associated with nursing time and supplies needed to draw up saline flush syringes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiment and certain modifications thereof when taken together with the accompanying drawings in which: 
         FIG. 1  is a perspective view of a regulator  2  for IV tubing according to a first embodiment that interrupts normal flow to flush for a specific period of time before returning to roller-clamp regulated flow. 
         FIG. 2  is an exploded diagram of the regulator  2  as in  FIG. 1 . 
         FIG. 3  is a top view of the regulator  2  of  FIGS. 1-2 . 
         FIG. 4  is a cross-section of the regulator  2  taken along the lines A-A′ of  FIG. 3 . 
         FIG. 5  is a perspective view of a regulator  102  for IV tubing according to a second embodiment that interrupts normal flow to flush for a specific period of time before returning to pre-flush flow. 
         FIG. 6  is a side cross-section of the regulator  102  as in  FIG. 5 . 
         FIG. 7  is a front cross-section of the regulator  102  of  FIGS. 5-6 . 
         FIG. 8  (A-C) is a composite sequential illustration of the operation of the regulator  102 . 
         FIG. 9  (A-C) is a detailed view of the operative components of the regulator  102 . 
         FIGS. 10 and 11  are a front cross-section and side cross-section, respectively, of an alternate embodiment of the regulator  202  that administers a calibrated volume of bolus flush before returning to a “pre-flush” flow setting. 
         FIG. 12  (A-C) is a composite view with enlarged illustrations of the slider paddle  230  and internal tube  204  configuration of the regulator  202  of  FIGS. 10-11 . 
         FIG. 13  (A-C) is a composite sequential illustration of the operation of the volume regulator  202  of  FIGS. 10-12 . 
         FIG. 14  is a perspective view of a conventional IV administration set. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is a manually-operated regulator for IV tubing that allows interruption of normal controlled-flow for a safe and convenient bolus flush (full flow of saline for a specific period of time or volume of saline) before returning to a “pre-flush” flow setting, eliminating the need to manually reset the roller-clamp regulator or to administer a separate saline flush injection. Three embodiments are disclosed, two for administering a flush for a specific period of time, and one for a specific volume of flush solution. 
       FIG. 1  is a perspective view of a regulator  2  for IV tubing according to a first embodiment that interrupts normal flow to flush for a specific period of time before returning to pre-flush flow. The regulator  2  generally comprises an elongated housing with main section  10  and a plunger section  12 . The main section  10  is formed as a three-walled elongate trough, and the existing IV tubing  4  runs through the trough of main section  10 . A roller-clamp  8  is rotatably seated across the trough of the main section  10  and protrudes out of an aperture  14  in the front face of main section  10 . 
       FIG. 2  is an exploded diagram of the regulator  2  which shows that roller-clamp  8  comprises an annular hub with rubber tread mounted thereon, and opposing posts  18  forming an axle. These posts  18  of the roller-clamp  8  are carried in vertical notches  11  formed inside the trough of the main section  10 , and the roller-clamp  8  is free to slide up and down along the notches  11  within the trough of the main section  10 . In operation, the roller-clamp  8  variably constricts the IV tubing  4  to restrict flow. 
     A regulator back plate  16  is formed as an elongate ramp leading from a lower tip to a yoked mounting flange  15  at the top. The regulator back plate  16  extends downward through the trough of the main section  10  behind the roller-clamp  8 , and is pivotally mounted therein by the yoked mounting flange  15  which fits within a recess formed at the top of the main section  10  and is pivotally held therein by outwardly protruding mounting pins  41  that extend out through holes in the yoked mounting flange  15 . The regulator back plate  16  serves as a backing against which the roller-clamp  8  presses against to restrict flow. In the normally-closed position shown, the regulator back plate  16  bears against the IV tubing  4  and provides a backstop for normal operation of the roller-clamp  8  in the conventional manner of an IV roller-clamp, allowing thumb-adjustment of the flow rate from the forefront of the regulator  2 . The more the roller-clamp  8  is thumb-rotated downward along aperture  14 , the more pressure it applies against the IV tubing  4  and the more flow is restricted. Conversely, when rotated upwards, the roller-clamp  8  releases pressure on the IV tubing  4  and the flow is less restricted. 
     The plunger section  12  is defined by a central pressure chamber formed as a cylindrical cavity running up through the center. The pressure chamber leads upward to an upper outlet  22  ( FIG. 2 ) with check valve  24  mounted there atop, and two opposed-protruding mounting posts  39  flanking the outlet  22 . The check valve  24  only allows air to enter the pressure chamber in the plunger housing  12 . A plunger  30  is slidably loaded into the pressure chamber, plunger  30  bearing an upper stopper  32  mounted atop a protruding post  34 . The stopper  32  rides along the pressure chamber and seals it off. Plunger  30  further comprises an elongated plunger formed much like a syringe&#39;s, the plunger leading downward to a flat base  31 , a pair of mounting posts  33  protruding outward on either side of the plunger near the base  31 , and a forwardly/upwardly protruding wedge  35  likewise bearing a pair of opposed catch posts  37  at its tip. A pair of elastic bands  42  (one on each side) are each looped around one protruding post  39  on plunger housing  12  and downward around a corresponding mounting post  33  on that same side of the plunger near the base  31 . The elastic bands  42  serve to bias the plunger  30  upward inside the plunger housing  12 . The plunger  30  is slidably captured against the plunger housing  12  by a flange formed with opposing rails  44 , the rails  44  slidably carried within a conforming channel  46  formed vertically along the plunger section  12 . A thumb-depression tab  38  crops outward at the top of the rails  44  and this is used for manually depressing the entire plunger  30  downward out of the pressure chamber of plunger housing  12 . Two opposing ears  48  are fixedly attached toward the bottom of the plunger housing  12  and protrude laterally outward, thereby providing a manual indexing for the thumb tab  38  and of the downward extent by which the plunger  30  is depressed. The two opposing ears  48  also allow the user to squeeze them together with the thumb tab  38 . 
       FIG. 3  is a top view of the regulator  2  of  FIGS. 1-2 , and  FIG. 4  is a cross-section of the regulator  2  taken along the lines A-A′ of  FIG. 3 . As best seen in  FIG. 4 , when in its normal (undepressed) plunger  30  position, the wedge  35  remains in contact with the regulator back plate  16  and biases it forward against the IV tube  4 , sandwiching the tube  4  against the roller-clamp  8  and regulating IV flow. 
     In operation, when it is desirable to administer a bolus flush, a user depresses the thumb-depression tab  38  until limited by the opposing ears  48 , thereby fully depressing the plunger  30  downward out of the pressure chamber of plunger housing  12 . Air is freely inducted into the pressure chamber through the check valve  24 . Eventually, the wedge  35  drops beneath the ramp of the regulator back plate  16  and frees it to swing backward, thereby releasing pressure on the IV tube  4  and allowing free flow. 
     In this plunger  30 -down position the rubber bands  42  are fully extended and begin to bias the plunger upward within the pressure chamber. However, the pressure inside the pressure chamber resists this and the plunger  30  is only allowed to move slowly upward as air is slowly allowed to bleed out through the upper outlet  22 . As the pressure chamber empties and plunger  30  moves slowly upward, the wedge  35  reencounters the regulator back plate  16  and again biases it forward against the IV tube  4 , sandwiching the tube against the roller-clamp  8  and regulating further IV flow. The catch posts  37  formed on the wedge  35  of the plunger  30  eventually enter notches  49  formed in the side walls of the main section  10  and the plunger  30  thereby comes to rest. 
     Note also that backplate stops  50  formed as inwardly protruding tabs in the side walls of the main section  10  serve to restrict backward pivoting of the regulator back plate  16  and keep it from pivoting too far when the plunger is depressed, thereby ensuring that the wedge  35  will always slide properly in between the regulator back plate  16  and plunger  30  as seen in  FIG. 4 . Similarly, a lower series of protruding tabs  52  in the side walls of the main section  10  serve to maintain a crook in the IV tube  4  and prevents shifting around inside the main section  10 . 
     The size of the pressure chamber, the outlet  22 , and the resistance of the rubber bands may be determined empirically to produce a calibrated time delay during which the IV tube  4  permits a flushing free flow. To get an adequate flush volume, an adequate activation time is required and this is approximately 30 seconds of flush time. One of the advantages of the above-described regulator  2  is that it accomplishes a semi-automatic flush using components and a form factor that are similar to existing commercial roller regulators, thereby providing a familiar look and feel to doctors and nurses and encouraging widespread adoption. This also saves manufacturing cost. Moreover, by simply varying dimensions, the regulator  2  can be made compatible with most popular conventional brands and sizes of existing IV tubing sets. 
     Two additional embodiments are herein disclosed: a second that administers a flush for a specific period of time, and a third for a specific volume of flush solution. 
       FIG. 5  is a perspective view of a regulator  102  for IV tubing  104  according to a second embodiment that interrupts normal flow to flush for a specific period of time before returning to pre-flush flow. The regulator  102  generally comprises an elongated housing with main section  112  and compressible lever section  114  mounted pivotally thereon. The main section  112  is formed as a trough, and the existing IV tubing  4  runs through the trough of main section  112 . A roller-clamp  108  is rotatably seated across the trough of the main section  112  and protrudes out of an aperture  110  in the front face of main section  112 . 
     As best seen in the side cross-section of  FIG. 6  and the front cross-section of  FIG. 7 , the IV tubing  104  runs internally through the main section over roller-clamp  108 . While not explicitly shown, it is necessary to maintain a certain degree of friction between the roller-clamp  108  and the main housing section  112 , and between the tubing  104  and the housing. Conventional rubber grommets may be used for this purpose. These will prevent the respective parts from sliding freely within the housing. 
     The compressible lever section  114  extends upward above its pivot point to a lever that bears against the IV tubing  104 . The compressible lever section  114  is pivoted at a pin  117  that spans the trough of the main section  112 . Both a compression spring  116  and a rotary damper  118  are mounted on the pin  117 . The spring  116  biases the lower flange of the compressible lever section  114  away from the main section  112 , maintaining a normally closed position. However, when the lower flange of the compressible lever section  114  is squeezed toward the main section  112 , the rotary damper  118  then opposes the immediate closure of the lever  114  by the compression spring  116 , and gradually reduces its counterbalancing force to provide a slow timed closure. In the normally-closed position the compressible lever section  114  bears against the IV tubing  104  and provides a backstop for normal operation of the roller-clamp  108 , allowing thumb-adjustment of the flow rate from the front of the regulator  102 . However, when it is desirable to administer a bolus flush, the compressible lever section  114  can be compressed manually against the main section  112 , thereby lifting the backstop section of lever  114  away from the IV tubing, and opening the IV tubing  104  to full flow for a predetermined period of time. 
     This operation is shown in more detail in  FIG. 8 , which is a sequential illustration. 
     At  FIG. 8(A)  the regulator  102  is in the normally-closed position, with the upper flange of compressible lever section  114  bearing against the IV tube  104  and providing for normal operation of the roller-clamp  108 , allowing thumb-adjustment of the flow rate from the front of the regulator  102 . 
     At  FIG. 8(B)  the lower flange of the compressible lever section  114  has been squeezed against the main section  112 , thereby lifting the backstop lever section away from the IV tube  104  and removing it as a backstop for normal operation. This fully opens the IV tubing  104  and initiates unobstructed fluid flow. 
     At  FIG. 8(C)  the compressible lever section  114  gradually returns to its original home position (under the spring bias of compression spring  116 ) to once again regulate fluid flow. This return home is effected over a calibrated time interval to limit the flush of  FIG. 8(B)  to a predetermined time. 
     The calibrated time interval is determined by the rotary damper  118 , which initially counterbalances the compression spring  116  but gradually reduces its counterbalancing force, allowing the compression spring  116  to overcome it and return the compressible lever section  114  to its original home position. This returns to the configuration of  FIG. 8(A)  in which the compressible lever section  114  bears against the IV tube  104  and provides a backstop for normal flow-controlled operation. 
       FIG. 9  shows the operative components of the regulator  102  including the lever  114  (at A), torsion spring  116  (at B) and rotary damper  118  (at C). The rotary damper  118  may be any small footprint rotary damper capable of generating enough braking torque to delay the full return of compression spring  116  by approximately thirty seconds. To get an adequate flush volume, an adequate activation time is required and this is approximately 30 seconds of flush time. There are a wide variety of commercially-available fluid-filled rotary dampers that will suffice. In actuality, the braking torque of any rotary damper will depend on the size of the surface of the rotor and housing disposed in contact with the viscous fluid. Thus, the torque increases when the dimensions of these elements are made larger. Nevertheless, it is possible to build a rotary damper small enough to conform to the footprint of a conventional IV roller-regulator such as shown and described in U.S. Pat. No. 5,497,863 to Schmidt et al. issued Mar. 12, 1996. Preferably, the rotary damper  118  used herein has an adjustable reverse-torque setting to provide regulator  102  with an adjustable activation time to allow the volume of fluid flushed to be varied. Nevertheless, the regulator  102  provides consistent activation times once the rotary damper  118  is set, within a specified repeatability tolerance. It is also noteworthy that the main housing  112  is formed with an enlarged frontal window  110  to allow rough visual inspection of the internal components and tubing  104 . One of the advantages of the above-described regulator  102  is that it accomplishes a semi-automatic flush using components and a form factor that are similar to existing commercial roller regulators, thereby providing a familiar look and feel to doctors and nurses and encouraging widespread adoption. This also saves manufacturing cost. Moreover, by simply varying dimensions, the regulator  102  can be made compatible with most popular conventional brands and sizes of existing IV tubing sets. 
       FIGS. 10 and 11  are a front cross-section and side cross-section, respectively, of an alternate embodiment of the regulator  202  that administers a calibrated volume of bolus flush before return to a “pre-flush” flow setting, again eliminating the need to manually open and later reset the roller-clamp regulator or to administer a separate saline flush injection. This volume regulator  202  generally comprises an enclosed housing  224  with end-wise inlets for ingress of the plastic IV tubing  204  and opposing outlets for egress. The housing  224  may be plastic and is intended to enclose the internal components in a protected space. Two expandable/collapsible bladders  226 A &amp;  226 B reside within the housing  224 , preferably at the approximate midpoint and with ample room inside housing  224  to allow for expansion/contraction. One wall of each bladder  226 A &amp;  226 B may be affixed to a sidewall of the housing  224  by a grommet  227  or the like, provided that the grommets  227  effect a fluid tight seal. However, grommets  227  are not necessary as the bladders  226 A &amp;  226 B can hang freely inside the housing  224  since they are substantially anchored at the top and bottom by the tubing  204 . 
     The housing  224  may be elliptical in shape although other geometries are possible. An elliptical shape presents a relatively smooth inner profile and minimize cross sectional area when inline with the tubing  204 . The housing  224  is preferably formed of clear plastic to allow an operator to see the internal tubing  204  and bladders  226 A &amp;  226 B. The bladders  226 A &amp;  226 B may be formed of siliconized rubber or more conventional IV bag material (EVA, PVC, PP) or other like materials, and are preferably tinted two different colors so that the operator can also see which one is distended. The bladders  226 A &amp;  226 B are size and elasticity-calibrated to expand to predetermined volumes in the range of 5 to 10 milliliters (ml). The bladders  226 A &amp;  226 B are each coupled at both ends to plastic IV tubing  204 , such that dual IV tubes  204  enter the inlet at the top of the housing  224  (or a single tube  204  enters and bifurcates to both bladders  226 A or  226 B). Likewise, dual IV tubes  204  branch from the respective bladders  226 A &amp;  226 B and leave the bottom of the housing  224  (or a pair of IV tubes  204  branch from the respective bladders  226 A and  226 B and conjoin to a single tube  204  leaving the outlet at the bottom of housing  224 ). Any bifurcation and joining of tubes  204  may occur inside or outside the housing  224 . The tubing  204  is preferably made of relatively large bore IV tubing to allow for the rapid inflow and outflow of fluid from the bladders  226 A &amp;  226 B. A pair of rubberized tube holders  228  are situated at the top and bottom of housing  224  near the inlets and outlets to capture the tubing  204  therein without constricting fluid flow. The housing  224  is further formed with two channels  222  (top) and  223  (bottom) defined along the inner surface of the housing  224 . These channels  222  and  223  are formed as shallow concavities and serve to contain the tubing  204  as well as providing a directional guide for expansion of the bladders  226 A &amp;  226 B. 
     As best seen in  FIG. 11 , a slider paddle  230  is pivotally mounted midway along the housing  224  at a pivot joint  231 . The slider paddle  230  comprises an elongated toggle member having an arcuate upper yoke  232  and arcuate lower yoke  234 , both yokes being uniformly offset to engage the tubing  204  immediately adjacent to the tubing holders  228 . The upper yoke  232  and lower yoke  234  both embrace the bifurcated tubing  204  at the respective positions. In general operation, the slider paddle  230  may be pivoted so that the upper yoke  232  constricts one tube and opens the other, while the lower yoke  234  does the same. This effectively opens the fluid flow path into one bladder (e.g.,  226 A) while closing the output (to allow that bladder  226 A to fill) while closing flow into the other bladder  226 B and opening the output (to allow that bladder  226 B to drain). Conversely, the slider paddle  230  may be pivoted in the opposite direction so that the upper yoke  232  releases the constricted tube and closes the open tube, the lower yoke  234  doing the same. This changes the fluid flow path, allowing the previously filled bladder  226 A to drain and the previously draining bladder  226 B to fill. In effect, the slider paddle  230  works like a toggle switch by lever action to selectively fill one bladder  226 A while draining the other  226 B, and vice versa. 
       FIG. 12  is a composite view with enlarged illustrations of the slider paddle  230  and internal tube  204  configuration. As seen at  FIG. 12A , the upper yoke  232  of slider paddle  230  is formed with a groove  238  comprising opposing (offset) apertures connected by a constricted slot. The IV tubes  204  pass down through the groove  238  and, if positioned in an aperture, remain open but if moved into the slot will be closed. Thus, in one position of slider paddle  230  one tube  204  will pass through an aperture and remain open, while the other is engaged in the slot and is closed. Conversely, if the slider paddle  230  is pivoted, the tubes  204  will switch, the closed one moving into an aperture and becoming open, while the other moving into the slot and closing. 
     As seen in  FIG. 12C  the lower yoke  234  of slider paddle  230  is formed with an identical groove  238  with opposing (offset) apertures connected by a constricted slot. Similarly, the IV tubes  204  from the bladders  226 A &amp;  226 B pass down through this groove  238  and, if positioned in an apertures, remain open but if moved into the slot will be closed. Thus, in one position of slider paddle  230  one tube  204  will pass through an aperture and remain open, while the other is engaged in the slot and is closed. If the slider paddle  230  is pivoted, the closed tube  204  opens and the open tube  204  closes. 
     As seen in  FIG. 12B , the tubes  204  are twisted to form a cross-over. This ensures that in one position of slider paddle  230  one bladder  226 A has an open input and closed output (to fill), while the other bladder  226 B has a closed input and open output (to drain), the converse occurring for the other position of slider paddle  230 . 
     The details of operation are more apparent in  FIG. 13  which is a composite sequential view of the volume regulator  202 . Intravenous fluid is fed into the device by gravity from a conventional IV bag (not shown). Initially the slider paddle  230  is in one position as seen at (A), and consequently one tube  204  entering from the top is open to receive fluid into one bladder  226 A (obscured) while the other input tubing  204  is closed and pinched by the upper yoke  232  of slider paddle  230 . This allows one bladder to fill and expand into the elliptical space inside housing  224 . Since the tubing  204  to the other bladder is closed only one bladder is filling or full at any given time. The other is emptying or empty, and the draining bladder is flushing fluid into the distal output tubing  204 . Approximating the bladders  226 A &amp;  226 B as cylinders, a volume of 10 ml would necessitate bladders  226 A and  226 B of approximately of 1 cm radius and 3.3 cm height. The cross-over tubing  204  arrangement described above ensures that one bladder fills while the other drains. Regular flow is not maintained through either bladder since the bladders  226 A &amp;  226 B can only be emptying completely or filling completely. Medications must only be given distal to the device, such that it is not possible for them to become entrained within the bladders—thereby leading to unpredictable administration into the bloodstream. 
     By simply moving the slider paddle  230  back and forth as needed, the operator has a predetermined volume of fluid that flushes the tubing  204 . The bladder, when empty, collapses on itself with its walls now apposed. 
     The above-described regulator  202  may also be used in conjunction with a conventional roller-clamp as described previously to regulate fluid, and one skilled in the art should readily recognize that a roller-clamp mechanism may be incorporated inside housing  224  if desired to merge the devices for this purpose. Moreover, the slider paddle  230  may be color-coded similar to the bladders  226 A &amp;  226 B to correlate the two positions of the slider paddle with the two bladders  226 A &amp;  226 B. 
     It should now be apparent that all three of the above-described embodiments  2 ,  102 ,  202  allow interruption of normal controlled-flow for a safe and convenient bolus flush (full flow of IV fluid), regulators  2  and  102  for a specific period of time, and regulator  202  for a specific volume of saline flush, before returning to a “pre-flush”, regulated flow setting. This simplifies the process of administering a bolus medication followed by saline flush, improves safety and eliminates over flushing. 
     Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications thereto may obviously occur to those skilled in the art upon becoming familiar with the underlying concept. It is to be understood, therefore, that the invention may be practiced otherwise than as specifically set forth herein.