US 2770235 A
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Nov. 13; 1956 N. M. NESSET ET AL PARENTERAL ADMINISTRATION OF LIQUIDS Filed June 29, 1953 11V VEN T0125 BY ATTORNEYS United States Patent PARENTERAL ADMINISTRATIONOF LIQUIDS Naurice M. Nesset, Palatine, and Cyrus R. llroman, Evanston, 11]., assignors to Baxter Laboratories, Inc., Morton Grove, III., a corporation of Delaware Application June 29, 1953, Serial No. 364,684
4 Claims. (Cl. 128214) This invention relates to the parenteral administration of liquids, and more particularly, to a device for dispensing an intravenous liquid at a controlled rate, and .for visually determining that the flow is proceeding atthe selected rate. The dispensing device or parenteral administration set of this invention has its greatest utility when used to dispense substantially transparent aqueous solutions, such as saline solutions, glucose and invert sugar solutions, and plasma. However, it can also be advantageously used for relatively opaque fluids such as whole blood.
In the design and operation of parenteral administration sets, it has been found necessary to provide means to admit air to the space above the liquid in the container as the liquid is dispensed for the purpose of equalizing the pressure within and without the container, thereby preventing a negative pressure fromthe building up within the container and stopping the flow of liquid. The usual practice is to provide an air tube extending from the air inlet opening in the stopper to a point adjacent the bottom of the container so that when the container is inverted the free end of the tube will project above the surface of the liquid and communicate directly with the airspace above the liquid. It is also desired to provide means which permit the rate of flow to be selectively varied, and which also makes possible a visual determinationthat the selected rate is being maintained. In other words, one of the desired elements of the administration set is some type of flow indicator. The customary flow indicator takes the form of a drip chamber interposed in the conduit from the container to the point of administration. The upper portion of the drip chamber is provided with a nozzle from which the liquid falls a drop at a time into the lower portion of the chamber which is partially filled with the liquid, thus permitting the drops to be counted as a measure of the rate of flow for a given time.
The use of air tubes and drip chambers of the type described has a number of disadvantages both from operational and economic standpoints, but heretofore no satisfactory alternative has been developed.
It is therefore an object of this invention to provide a parenteral administration set which eliminates both the conventional air tube and drip chamber. More particularly, it is an object of this invention to provide a simplified air inlet structure for a container of an intravenous liquid which performs the functions of both the conventional air inlet tube and drip chamber, that is, which both admits air to the space above the liquid and also provides an accurateindication of the rate at which the liquid is being dispensed. It is a further object of this invention to provide means for admitting air from .the exterior of an intravenous solution container to a point beneath the surface of the solution when the container is inverted, While at the same time preventing the liquid from leaking out of the container through the air inlet passage. 'It is a stillfurther object of this invention to provide a means for admitting air in the manner described which is charac- 2,770,235 Patented Nov. 13, 1956 "ice 2 terized by the further fact that the air is admitted in discrete increments, i. e., separate bubbles, which are of sufiiciently large size and sufliciently spaced apart to be easily countable, thereby permitting the air bubbles per minute to be cou-nted as a direct measure of the rate of liquid flow. In this connection, it is another object of this invention to provide an air inlet structure of the fluid during the administration without any substantial variation in the mass of air within each bubble during the course of the administration, and which will therefore compensate for the release of an equivalent volume of fluid at a uniform ratio, for example, say one air bubble per .1 cc. of liquid. Another specific object of this invention is to provide a parenteral administration set having an air inlet structure of the type described which also is adapted to maintain the number of airbubbles liberated per minute at a substantially constant rate during the entire administration, and which is unaffected by the decreasing liquid level in the container. Further objects and advantages will appear as the specification proceeds.
Specific embodiments of this invention are illustrated in the accompanying drawings, in which- Fig. 1 is an elevational view of a parenteral administration set embodying the principles of this invention; Fig. 2, a cut-away perspective view of the container closure and air inlet structure which are largely responsible for the new results achieved; Fig. 3, a perspective. view of the air inlet tube of Figs. 1 and 2; and Fig. 4, a cut-away view similar to Fig. 2, but showing a modified form of the invention.
Looking first mainly at Fig. 1, there is shown an apparatus for the parenteral administration of an aqueous base liquid including a liquid supply container or bottle A and a conduit means or assembly B, providing a communicating passage extending from container A to the point of administration of the liquid, which, for example, could be at C. By way of specific example, container A contains an intravenous saline solution which flows downwardly through conduit assembly B into the vein of the patient at C.
In the specific illustration given, in. order to provide for the supporting of container A in an inverted position,
as shown, it is provided with a recessed ring 10 having a support bail 11 pivotally connected thereto. Container A is also provided with a neck portion 12 enclosing an open month which is covered by a closure or cap assembly 13 having a retaining ring 14 which holds plug or stopper member 15 in place.
Stopper 15 is preferably constructed of a resilient flexible material such as soft rubber and is provided with an air inlet opening 16 and a liquid outlet opening 17, as shown more clearly in Fig. 2. When openings 16 and 17 are of the type illustrated, it is customary to provide a diaphragm or seal (not shown) on the outside of the stopper 15, which is removed to prepare the container for the administration. Usually a hollow plug-in connection 18 is inserted in opening 17 with its lower end secured to a flexible hose 19. The other end of hose 19 can be connected through an adaptor 20 to an administration needle 21. It is preferable to provide hose 19 with an adjustable clamp for constricting the hose to regulate the rate of flow, for example, a control clamp 22 of malleable metal can be disposed about a portion of hose 19.
Air inlet passage 16 is shaped or provided with a passage-shaping member which provides means for admitting air to container A beneath the surface of the liquid therein when the container is inverted, while at the same time preventing the leaking of liquid through the air inlet passage. To accomplish these results, as well as other of the objects set out above, it has been found desirable to provide the air inlet passage with a restricted capillary portion and an enlarged portion inwardly thereof providing a collection chamber for the air passing through the capillary portions. Preferably, this is accomplished by providing an air inlet tube 23 which is insertable, at least part way, into passage 16, as illustrated in Fig. 2. In the illustration given, and preferably, air inlet tube 23 provides a capillary portion 24 and inwardly therefrom an air collection chamber portion 25. For proper operation, it has been found desirable to have the air inlet passage through tube 23 gradually enlarge in cross-sectional area above capillary portion 24 into air collection chamber 25. Preferably, the enlarging passage portion is of conical shape. When the structure is assembled as illustrated in Fig. 2, air inlet tube 23 provides the entire air collection chamber 25. Alternatively, the modified structure shown in Fig. 4- can be employed, in which the inner end portion of stopper passage 16 provides an extension of air collection chamber 25, and thereby can be considered as part of the air collection chamber. However, it is preferable to have the air collection chamber, whether it is provided in part by stopper passage 16' or entirely by tube 23, terminate at approximately the level of the inside surface of stopper so that the air collection chamber will be below the surface of the liquid throughout the entire course of the administration.
Air inlet tube 23 and stopper 15, where the stopper provides part or all of the air inlet passage, can be formed of a wide variety of different materials, including plastics, glass, rubber, metals, wood, etc. In other words, the material of construction is not especially critical. However, for simplicity of manufacture it is convenient to mold the air inlet tubes from a suitable plastic. Stopper 15 is preferably made of soft rubber. It is desirable to have the interior walls of inlet tube 23 relatively smooth to minimize the pressure drop across the inlet tube. This may be done in practice if a molded finish is too rough by coating with an oil or silicone film. It is also desirable to minimize the attraction between the walls of air collection chamber 25 and the aqueous parenteral solution. The less the liquid to surface attraction within chamber 25, the more rapid is the recovery of flow rate in the event the bubble flow is accidentally disrupted by bumping or shaking container A. Also, the harder it is to disrupt the flow. Therefore, it is preferred to have at least the walls of the air collection chamber substantially hydrophobic.
Although it is not essential for the operation of the structure, it is preferred to provide outwardly of capillary passage 24 a filter chamber 26. The purpose of filter chamber 26 is to receive a Wad or ball 27 of air permeable fibrous material such as loosely intermeshed fibers of cotton, etc. In other words, the air entering filter chamber 26 must pass through filter plug 27 before entering container A, thereby removing particles of dirt or other solid contaminants in the air which might otherwise enter the solution. To prevent filter plug 27 from being forced into the outer end of capillary passage 24, it is preferable to provide a reduced passage portion 28 between capillary portion 24 and filter chamber 26 so that filter plug 27 is held at a spaced distance from capillary portion 24. In actual practice, it has been found desirable to have filter plug 27 formed so that there is substantially no pressure drop across the filter plug, while at the same time achieving a satisfactory filtering action. This can readily be accomplished with a loosely packed cotton ball.
It is desirable to provide the outer end of tube 23 with a removable cap or closure. In the illustration given, the outer end of tube 23 is provided with an attached cap 29 of flexible resilient material having a hinge portion 30 which permits cap 29 to be seated and unseated without separating it from tube 23. This cap structure forms the subject matter of co-pending application United States Serial No. 326,702, filed De- 4 cember 18, 1952, now Patent Number 2,705,955 granted April 12, 1955.
Air inlet tube 23 can be adapted tocooperate with stopper 15 in positioning the tube relative to the stopper. For example, air inlet tube 23 is shown provided with laterally-extending arms 31 and 32, which abut the outer end of stopper 15 when the tube 23 is correctly positioned, as shown more clearly in Fig. 2. In the modified structure shown in Fig. 4, tube 23' is provided with an abutment shoulder 33' for the same purpose.
Operation In practicing this invention, the parenteral administration set is assembled in the manner indicated in Fig. 1. The container A is suspended in inverted position, as shown, except that cap 29 is seated on the outer end of tube 23. Before the introduction of needle 21 to the vein of the patient, it is desirable to clear the set of air by passing a portion of the liquid downwardly through conduit assembly B. Usually this can be accomplished while cap 29 is seated on the outer end of air inlet tube 23 by opening clamp 22. The liquid will drain out through hose 19 until sufiicient vacuum is built up in the air space above the liquid in container A to hold up the column of liquid in the conduit assembly B. After this preliminary step, the needle is inserted in the vein of the patient, and cap 29 is removed from the air inlet tube to start the administration. At first, bubbles will rise rapidly and close together from the air inlet tube until the pressure within the container air space plus the hydrostatic head of liquid in the container is sufficient to balance the atmospheric pressure in tube 23. Then at this equilibrium condition, for each increment of liquid passing out through needle 21, there will be a definite mass of air transferred to the air space above the liquid in the form of relatively large bubbles and the bubbles will be spaced apart, thus making them easily countablej The number of air bubbles per minute can be selectively controlled by adjusting clamp 22, since the number of air bubbles are in direct proportion to the quantity of outfiowing liquid. Moreover, air inlet tube 23 can be constructed so that each air bubble is equivalent to a convenient amount of liquid for the purpose of determining the rate of flow, say one bubble for each .1 cc. of liquid. In actual operation, it has been observed that the air collects within chamber portion 25 of the air tube, and that the liquid is normally prevented from entering this space.
It has been found that the rate of liquid administration can be maintained substantially constant during the entire course of administration, and that if the operation of the set is interrupted in any manner, the desired rate will be automatically re-established. If the container is accidentally disturbed by bumping or shaking, the flow will only be temporarily disrupted. The disturbing of the container may cause the liquid to move downwardly within the air collection chamber, but it will usually not pass beyond capillary passage 24 unless the movement of the container is extremely violent. As soon as the container is stabilized, the air readily displaces the liquid from collection chamber 25, thereby re-establishing the desired conditions for equilibrium operations of the set. This recovery is particularly rapid when the walls of collection chamber 25 are substantially hydrophobic.
It will be apparent from the described mode of operation of this invention that container A, or at least the walls thereof, should be transparent, and that best results are obtained when the liquid within the container is transparent or at least sufiiciently translucent to permit the air bubbles to be viewd as they rise through the solution. However, it is possible to use the invention in dispensing relatively opaque liquids such as whole blood, since the air bubbles can be observed as they break through the upper surface of the liquid. Moreover, with liquid suspensions such as blood, the air bubbles perform the addi-:
tional function of continuously agitating the liquid. Parental solution containers are usually constructed of glass.
While in the foregoing specification specific embodi ments of this invention have been described in considerable detail for purpose of illustration, it will be apparent to those skilled in the 'art that many of the details set forth can be variedwidely without departing from the spirit of the invention.
1. In combination with a transparent-walled container at least partially filled with an intravenous liquid, said container being supported in a mouth-downward position, a closure mounted in said mouth, a passage-providing means extending through said closure for admitting air bubbles beneath the surface of said liquid While at the same time preventing the escape of liquid through said passage, said passage including a capillary portion and an enlarged portion inwardly thereof providing a collection chamber for the air passing through the capillary portion, said passage gradually enlarging in cross-sectional area from said capillary passage portion into said collection chamber portion, said passage-providing means being adapted to admit separate air bubbles beneath the surface of said liquid, said bubbles being of suificiently large size and sufliciently spaced as to be readily countable.
2. An air inlet structure for admitting air bubbles to an inverted container of an intravenous liquid, including a member providing a passage communicating at its outer end with the atmosphere and at its inner end with said liquid beneath the surface thereof, said passage including a capillary portion and an enlarged portion inwardly thereof providing a collection chamber for the air passing through the capillary portion, said passage gradually enlarging in cross-sectional area from said capillary portion into said collection chamber portion, and wherein the walls of said collection chamber are substantially hydrophobic.
3. In combination with a transparent-walled container for the parenteral administration of an aqueous solution, said container being supported in an inverted position and having a mouth at its lower end equipped with a closure, said closure having an air inlet opening and a liquid outlet opening beneath said solution, an air inlet tube received in said air inlet opening and terminating at a point closely spaced to the inner end of said closure, said air inlet tube providing a passage having a capillary portion, and a collection chamber inwardly of said capillary passage portion connected thereto by a passage portion of gradually increasing cross-sectional area, and wherein the walls of said collection chamber portion are substantially hydrophobic.
4..An air inlet tube insertable in the air inlet opening of a container of the type described, said air inlet tube providing a passage for the admission of air, said passage including a capillary portion and an enlarged portion inwardly thereof providing a collection chamber for the air passing through the capillary portion, and wherein at least the walls of said collection chamber are substantially hydrophobic and said passage gradually enlarges in crosssectional area from said capillary passage portion into said collection chamber portion.
References Cited in the file of this patent UNITED STATES PATENTS 2,214,260 Ravenscroft et al Sept. 10, 1940 2,573,637 Bender Oct. 30, 1951 FOREIGN PATENTS 987,076 France Apr. 11, 1951