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Patent Application Publication Feb. 28,2002 Sheet 6 of 6 US 2002/0026148 Al
MULTI-PATIENT FLUID DISPENSING
BACKGROUND OF THE INVENTION
 In copending application Ser. No. of even
date herewith and assigned to the same Assignee as the present invention, discussion was undertaken with regard to the problems arising from the potential cross-contamination that can occur with a multi-patient fluid dispensing system. One facet of the system provided involves prevention of contamination of the multi-use segment of the fluid path during the time the system is connected to the patient. The disclosed system utilized one of two methods: a back flow preventing valve and a sterile filter, or a physical separation achieved by filling a dose container and separating the dose container from the filling fluid path before connection to the patient.
 A back flow valve and a sterile filter combination should give sufficient protection. Bacteria cannot penetrate the filter. Viruses and proteins can penetrate the filter but are not active, and so cannot swim upstream. They can only diffuse. The drawbacks to this approach involve the pressure drop through the filter and volume of fluid remaining in the filter. Also, there is no way to verify that the filter is not leaking.
 The present invention deals with additional methods of preventing contamination of the reusable fluid path by the patient being injected. To achieve the improved methods of preventing contamination, the present invention embodies the concept of preventing back flow, by providing no open fluid path through which bacteria can migrate or viruses or pyrogens can diffuse. (If a path is open, the velocity can then be made sufficient to prevent back diffusion.) Additionally, turbulence must be avoided since turbulence necessarily involves reverse flows and eddys that can carry material against the flow, unless the flow is high enough to prevent any part of the fluid from having a net upstream velocity vector.
 Means of preventing contamination of the fluid path by contaminants other than the patient being injected
are presented in copending application . Any of the
concepts presented there may be matched with any of the embodiments presented here. The relevant feature is the "per patient" connection.
OBJECTS OF THE INVENTION
 It is a principal object of this invention to provide an improved apparatus for injecting a fluid medium into a plurality of patients while minimizing the chance of crosscontamination.
 It is another object of this invention to provide an apparatus for injecting fluid mediums into patients in which there is no continuous stream of fluid existing between the source of the fluid and the patient.
 It is another object of this invention to provide an apparatus in which a peristaltic apparatus is present which precludes the reverse flow of substances from the patient towards the origin of the fluid to be injected.
 Other objects and advantages of this invention will be in part obvious and in part explained by reference to the accompanying specification and drawings in which:
DESCRIPTION OF THE DRAWINGS
 FIG. 1 diagrammaticaily shows an apparatus and a system for injecting a fluid medium directly into a patient which minimizes the chance of patient-to-patient crosscontamination;
 FIG. 2 is a form of peristaltic control apparatus that can be used in the cross-contamination preventing system of FIG. 1;
 FIG. 3 is a front perspective of the apparatus of FIG. 2;
 FIG. 4 is another diagram showing another type of peristaltic apparatus for use in the present invention;
 FIGS. 5a and 5b are diagrammatic illustrations of an apparatus in which there is a biased element to preclude reverse flow of fluid from the patient towards the source of medical fluid;
 FIG. 6 is a diagrammatic view showing one form of an apparatus for creating a discontinuous flow of medical fluid;
 FIG. 7 is a diagrammatic showing of another type of apparatus having discontinuous flow and a plurality of patient connections;
 FIG. 8 is a diagrammatic showing of a packeted flow means;
 FIG. 9 is a diagrammatic showing of a disposable burette system; and
 FIG. 10 is a diagrammatic showing another system for packeting flow means.
DESCRIPTION OF THE INVENTION
 To better understand the present invention, reference is made to the drawings, and specifically to FIG. 1 there is provided a source of fluid medium which is contained within a bulk container 10. Numeral 11 represents a similar container that is used to hold a supply of diluent, in the event that it is desired to reduce the concentration of the fluid medium contained within source 10. A metering pump 12 draws fluid from the supply source 10 at the proper flow rate. The second metering pump 13 draws diluent (when desired) from the bulk reservoir 11 within which the supply of diluent is contained. A preferred metering pump is a precision peristaltic pump with santoprene tubing. A pump wall design similar to that of U.S. Pat. No. 5,236,014 would minimize the pulsatile flow characteristics. As the fluids are removed from containers 10 and 11, they are heated by means of heaters 14 and 15 so that they approximate body temperature. The heating, of course, can decrease the viscosity and make the fluid more comfortable for the patient. Upon leaving the metering pumps 12 and 13, the fluids meet as they are joined and flow through a static mixer 20 that contains helical vanes. The company ConProTech makes many sizes and lengths, some with polypropylene vanes and case. These static mixers are designed for mixing fluids with very different viscosities and varying dilution ratios. The exact length and diameter to be used will depend to some degree upon the viscosity of the substances being comingled. The mixture then flows through a fluid assurance device 22 which many be an ultrasonic detector so that the presence or absence of air in the fluid can be determined.
Since these types of devices cannot detect small air bubbles, by being located before a pressurization pump 25, bubbles will be as large as possible. It helps minimize the chance that a broken line or human error can inject air into the patient. From pressurizing pump 25, a supply conduit 26 leads to a rotary switch 27 that can distribute fluid between the individual or "per patient" hookups 30, 31 and 32. Each of the individual connections contains what has been diagrammatically shown as a section to mate with a peristaltic apparatus 35. Each per patient disposable tube 36 is placed in a peristaltic apparatus 35 before being connected to the patient. Then it is connected to the patient and the injection is completed. The disposable connector tube 36 is disconnected from the patient. The rotary valve is turned to seal off the opening and the tube removed from the peristaltic apparatus and the connection to the rotary valve. This portion is then discarded. The next tube should be placed in the peristaltic apparatus.
 This is a good strategy but it requires operator vigilance to make sure that the line is in the peristaltic device before being connected to the patient and that the rotary valve is moved before the line is removed from the peristaltic device. Interlocks and intermediate all/off positions on the rotary switch could be provided. The rotary valve could have a "no connection" position between each connection position. The interlocks could function such that the rotary valve cannot be moved to access an output line until the line is in the peristaltic device, and another interlock could require that the rotary valve be turned to the intermediate off before the tubing can be removed from the peristaltic pump.
 The present apparatus includes an electronic control system (ECS) 40 to assure that the needs of the patient are met safely. ECS 40 gets information on the contents of the bulk reservoirs 10 and 11. The preferred method is to read bar codes indicated by numerals 10' and 11' respectively. Another way is to quiz the operator to enter the data each time a bulk reservoir is changed, and then store that information. The operator would read the label on or packaged with the bulk reservoir, and enter the appropriate data. This need only be done when a bulk reservoir is changed.
 With each injection, the operator needs to tell the system what to do. The data most similar to present practice is: 1) the concentration desired, 2) the flow rate, and 3) the total volume to be delivered. Present practice also includes multiple phases with various flow rates during each phase. This system would allow various contrast concentrations during each flow rate as well.
 However, given the capabilities of this system, a preferred set of information is: 1) the procedure being done, and 2) the patient weight. This way the contrast dose could be optimized for the patient. The algorithm would have been previously provided information on milligrams of iodine per kilogram of patient for each procedure when the system was first installed in the hospital. It could display concentration, flow rate and volume for operator verification, if the operator desired. An electronic interface 41 is shown which can connect to the hospital information system to get information on the patient, such as weight. Then the operator would only have to input the patient number. The electronic interface could also be connected to the imaging equipment. It could send or receive information so that, for instance, the
operator only need to program the CT scanner with number of slices and body section, and this would be transmitted to the contrast delivery system to be used in determining flow rates and delays. The electronic interface would also be used to let the scanner trigger the contrast delivery system or vice versa, after the appropriate delays. A hard copy printer may be optionally part of the user interface, receiving data from the ECS. This can print a record of the actual injection for insertion into the patient records. The output may be alphanumeric or be a graphical representation of the injection.
 The operation of delivering fluid to the patient can be started by the operator with a start switch on the contrast delivery system, or from the console of the scanner. There would need to be an arming procedure similar to that of present injectors to help assure patient safety.
 In CT, usually only one injection is given, sometimes with pauses and changes in flow rates. As the end of the injection is reached, contrast can be conserved if the contrast flow is stopped and the diluent flow continued so the "bolus" of diluted contrast is flushed out of the tubing and into the patient. In angiography, several injections may be used. It is necessary to flush only after the last injection, although no harm, except injecting a little extra fluid, occurs if the flush follows each injection.
 Another form of waste is using contrast to prime the fluid path which is disposed of with each patient, especially if the concentration has not yet been decided upon. The flush or diluent fluid is much cheaper than the contrast and of lower viscosity, so it can be used to prime the line and make sure that all air has been removed from the path to the patient.
 Referring to FIGS. 2 and 3 an alternative would be to make the peristaltic mechanism be fixed with the tubing, rather than separate as shown in FIG. 1. It would be disposable, but, it could be a very simple disposable with four wheels on a cross and a band which held the tubing for one or more turns. (It could be less than one turn, but one or more is preferred to equalize the lateral forces.) This type of construction is shown in FIGS. 4 and 3 with numeral 50 indicating the wheels mounted on cross 51 and in contact with supply tubing 52. FIG. 4 shows an even simpler arrangement where the wheels form a planetary gear set 60, with the inner gear free to rotate. In this embodiment, it might be easier to have the ratchet mechanism on the band as shown at 61 in FIG. 3. This whole assembly does not need to be more than 1" across. While the peristaltic pump never has an open fluid path, turbulence can move material from the wall to the wall farther upstream. Thus, it is desirable, but not essential, that the tubing diameter be chosen to preserve laminar flow. Since the flow ranges differ by modality, the Reynolds number calculation, familiar to fluid mechanics, will need to be used to make this determination.
 The peristaltic mechanism could be used as a flow sensor. It could be coupled to a shaft on the durable equipment or an optical sensor could detect when the gears pass. Another use of the peristaltic flow sensor is as a mechanical stop. Peristaltic flow sensor could be placed on the durable equipment in such a way that the ECS 40 read the number of revolutions and stop its rotation when the appropriate volume was reached. Because the peristaltic flow sensor has some friction, it also prevents flow through