CA2068563A1 - Method and apparatus for infusing medical solutions - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An IV infusion method and apparatus includes a plurality of fluid pumps mounted within a portable support housing and coupled to an IV tube. Each separate fluid pump is adapted to deliver fluid at a substantially constant delivery pressure predetermined by the characteristics of the pump. Each fluid pump includes an elastomeric membrane stretched into its region of nonlinear elasticity over a contour surface. Check valves located between the pumps and the IV tube control sequential dispensing of fluids from the pumps. The method and apparatus are especially adapted to a SASH process.

PATENT: 10700.168

Description

~$3~3 1 FIELD OF _HE INVENTION
The present invention relates to methods and apparatus 3 for infusing medical solutions in a predetermined sequence 4 into patients. The present invention is particularly, but not ~5 exclusively, useful for infusing medical solutions in 6 accordance with a SASH or SAS process automatically and in the , correct sequence.
8 .`

~o Current intravenous IV site flushing techniques for Il antibiotics and other medicaments use saline and heparin 12 solutions to maintain an IV site. One such technique is known 13 in the art as a SASH process. The term SASH refers to the 14 sequential infusion of a saline (S) solution for initially flushing an IV site, followed by the infusion of a medicant 16 such as an antibiotic (A), followed by another saline (S) 17 solution flush, and for those IV sites that require it a final 18 infusion of a heparin (H) solution as an anti-coagulant. The 19 dosage of the saline and of the heparin is typically in the range of 3-5 ml. The dosage of an antibiotic in a diluent may O ~ ~~ 21 vary from about 20-250 ml.
,'o-~ 22 In the past the SASH process has typically been performed ~ g~O~ 23 using pre-filled medical syringes. This requires separate o ~ 24 syringes each having a separate needle. Additionally/
multiple site access and a sequential site cleaning are also 26 required. This relatively complicated procedure is difficult l for homecare and ambulatory patients to perform. It is 2 critical that the procedure be carried out in a proper 3 sequence to insure a non-clogged access to the IV site.

4 For maximum flexibility in the implementation of an , extended and comprehensive infusion therapy program there is 6 a recognized need for a SASH method and apparatus that can be _ performed by a greater number of untrained personnel such as 8 outpatients. Preferably such a SASH method and apparatus 9 could also be set up and operated by an ambulatory patient, with little or no additional training from medical personnel.
11 One such SASH delivery system that requires additional 12 training is marketed by Block Medical, Inc. of Carlsbad, 13 California under the trademark of Auto-SASH~O This system 14 includes thre~ separate reservoirs that contain two doses of ~ a saline solution and one dose of a heparin solution. Each of 16 the reservoirs is coupled to a single IV line and is 17 discharged by a manually operated press pump formed integrally 18 with the reservoir. The system is designed for treating an IV
9 site while an antibiotic is being administered using a separate IV delivery system. Prior to dispensing of an O ~ ~~ 21 antibiotic into the IV site the IV line of the Auto-SASH~ is ,~o~ 22 coupled to the site. A patient first dispenses a dose of 23 saline solution into the site (for flushing the site) by O ~ ~ 24 manually-pressing the press pump for that reservoir. The antibiotic is then dispensed followed by a dose of saline from 26 the Auto-SASH~. Finally, a dose of a heparin solution can be ~$~3 administered in the same manner. A deficiency of this prior ~ art system is that a patient must manually discharge each :~ valve in the proper sequence. This requires attentiveness and 4 some training on the part of the patient. Additionally, this S Auto-SASH~ system must be used in combination with a separate 6 delivery system, such as a pump or IV pole for the antibiotic.
_ The present invention is directed to a portable SASH infusion 8 apparatus and method that overcomes these prior art 9 limitations.
In light of the above it is an object of the present l invention to provide a method and apparatus to simply and 12 safely infuse medical solutions in the proper sequence 13 especially for a mobile or ambulatory patient. Another object 14 of the present invention is to provide a method and apparatus for infusing medical solutions that can automatically dispense 16 solutions in the proper sequence for a SASH process. Still 17 another object of the present invention is to provide a 18 portable IV infusion apparatus which provides for the complete 19 discharge of separate solutions and for a substantially uniform delivery pressure for each separate solution. Yet 21 another object of the present invention is to provide a 22 portable IV infusion apparatus for multiple solutions which ~ 0 a~
K ~O~ 23 can be reused and pre-filled in a ready-to-use configuration 3 ~ 24 for a relatively extended period of time while maintaining sterility of the solutions held in the apparatus. Another 26 object of the present invention is to provide a portable IV

2 ~ $ 3 infusion apparatus for multi,ple solutions in the proper sequence which is easy to use, relatively simple to :~ manufacture and comparatively cost effective.

~5 SUMMARY OF T~E INVENTION
<, In accordance with the present invention a portable IV
7 infusion apparatus includes a plurality of separate fluid pumps for sequentially dispensing medical solutions at 9 different fluid delivery pressures to an IV site. In an illustrative embodiment for a SASH process four separate fluid 11 pumps are mounted within a transportable support housing and 12 are coupled to a single IV tube~ The IV tube may include an 13 on-off valve constructed as a conventional slide clamp. Each 14 separate fluid pump is adapted to deliver solution at a delivery pressure pre-determined by the characteristics of the 16 fluid pump. Check valves are located between the separate 17 pumps for sequentially dispensing solution from each pump into 18 the IV tube after the previous pump is emptied. In use, a 19 patient may use the device by first priming the IV line, opening the on-off clamp to occlude the IV line, and then 2~ hooking'the line to a venous access device. The infusion 22 apparatus of the invention then automatically delivers the 23 fluid solutions in a proper sequence as a result of the pre-24 determined delivery pressures o~ the infusion apparatus.
In a broad sense, the portable IV infusion pump may be 26 loaded with the operative solutions at a hospital or pharmacy 2 ~

and is then adapted to dispense multiple solutions to an IV
2 site by a method that generally stated includes the steps of:
~3l. connecting a first and a second reservoir to a single 4 IV line;
52. pressurizing the first reservoir with a first fluid 6 to a pressure of Pl and completely dis~harging the firstreservoir at a substantially constant delivery pressure;
83. pressurizing the second reservoir with a second fluid 9to a pressure of P2 and completely discharging the second 10reservoir at a substantially constant delivery pressure with Pl > P2;
124. controlling fluid flow such that the first reservoir 13 is completely discharged of fluid prior to the second 14 reservoir initiating discharge of fluid and the second reservoir is then completely discharged of fluid.
16For a SASH process four separate reservoirs are involved, 17 a saline containing reservoir at a pressure of Pl, an 18 antibiotic containing reservoir at a pressure of P2, a saline 19 containing reservoir at a pressure of P3, and a heparin ~ 20containing reservoir at a pressure of P4, with Pl > P2 > P3 >
O O ~~ 21 P4- (For a SAS process three separate reservoirs are ~O~ required.) For sequentially controlling flow from the K ~0~ 2~separate reservoirs into the IV tube~ check valves may be U 3 .located between the reservoirs and IV line.
~ 25In an illustrative embodiment each separate fluid pump 7~includes a pressurized reservoir or fluid chamber formed by an elastomeric membrane permanently stretched into a region of nonlinear elasticityO such a fluid pump is disclosed in copending U.S. Patent Application entitled "Portable Infusion Pump" and commonly owned by the Assignee of the present application. This type of pump is characteri2ed by a 6 substantially constant fluid delivery pressure and by a , substantially complete discharge of fluid from the pumping 8 chamber. For a SASH process four separate pumps may be 9 provided to pressurize and deliver fluid at four different substantially constant pressures. For a SAS process three pumps are required. Alternately, in place of four separate 12 pumps a single pump having four separate chambers each 13 pressurized to a different pressure by a single elastomer 14 formed with areas of different thicknesses, corresponding to the different chambers may be provided.
16 The novel features of this invention, as well as the 17 invention itself, hoth as to its structure and its operation, 18 will be best understood from the accompanying drawings, taken 19 in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in O ~> ~ 21 which:
-~ 22 ~ 5~wO~ 23 BRIEF DESCRIPTION OF THE DRAWINGS
U ~ ~u~ 24 Figure l is a perspective view of a portable infusion apparatus constructed in accordance with the invention shown 26 operatively connected to a patient;

~ 3 Figure 2 is an isometric view of a portable infusion ~ apparatus constructed in accordance with the invention;
:3 Figure 3 is a schematic diagram of a portable infusion 4 apparatus constructed in accordance with the invention;
Figure 4 is a perspective view of a single pump of the 6 portable infusion apparatus;
_ Figure 5 is an exploded isometric view of the components 8 of a single pump of the portable infusion apparatus;
9 Figure 6A is a cross sectional view of a single pump of the portable infusion apparatus as seen along line 6-6 in Il Figure 5 with an elastomeric membrane of the pump collapsed;
12 Figure 6B is a cross sectional view of a single pump of 13 the portable infusion apparatus as seen in Figure 6A with the 14 elastomeric membrane of the pump expanded to establish a pressurized fluid chamber;
16 Figure 7A is a modeled and empirically obtained Pressure 1, versus Volume graph for the separate pumps of the infusion 18 apparatus;
9 Figure 7B is a Pressure v. Volume Delivered graph showing the discharge of fluids in a SASH process in a timed sequence;
21 Figure 8 is schematic diagram of a check valve component 22 for the infusion apparatus;
23 Figure 9 is a schematic view of an alternate embodiment 24 portable infusion apparatus;

~$~3 l Figure lOA is a plan view of another alternate embodiment 2 portable infusion apparatus for a SAS sequence; and :3 Figure 11 is a schematic view of yet another alternate embodiment portable infusion apparatus having a generally ~S cylindrical construction.

8 Referring now to Figure 1, an infusion apparatus for 9 infusing medical solutions in accordance with the invention is l shown and generally designated as 10. As indicated in Figure 1 the infusion apparatus 10 may be worn by a patient 12 during 12 ambulation and can be attached to the patient 12 by any well 13 known means, such as a belt 14. Further, Figure 1 shows that l4 the infusion apparatus 10 can be connected in fluid communication with the patient 12 for the infus~on of fluids l6 into the patient 12 through an IV line 16. It is also shown 17 that the IV line 16 can include an in-line air filter 18 of a 18 type well Xnown in the pertinent art which will prevent the 19 infusion of air to the patient 12. Additionally, an on-off ¢ 20 valve 20 can be operatively associated with the IV line 16 to O O ~~ 2l initiate or terminate the flow of fluid from the infusion >'~2~ 22 apparatus 10 through the IV line 16. Although the particular ~8 23 on-off valve 20 which is shown in the Figures is a standard o 3 ~w~ 24 slide clamp, it is to be appreciated that any on-off valve 20 that is well known in the pertinent art will suffice for 26 purposes of the present invention.

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that is well known in the pertinent art will suffice for purposes of the present invention.
3 Referring now to Figure 2 the infusion apparatus 10 is 4 shown. The infusion apparatus 10 includes four fluid pumps ;, 22a-d mounted within a single carrier housing 24. The 6 infusion apparatus 10 shown is adapted to perform a SASH
7 process. Alternatively a lesser or greater number of fluid 8 pumps 22a-d may be assembled within the carrier housing 24.
9 As shown schematically in Figure 3, the fluid pumps 22a-d are coupled in flow communication to the IV line 16.
Il Additionally, each pump 22a~d is coupled to a check valve 25a-! 12 d. The check valves 25a-b are located between the IV line 16 and the fluid pumps 22a-d to regulate a sequence of fluid flow 14 from the fluid pumps 22a-d. Each fluid pump 22a-d is adapted to deliver fluid at a substantially constant pressure until l6 the pump 22a-d is substantially completely disrharged.
l7 Delivery pressure bands, Pl through P~ of the pumps 22a-l~ d are selected such that Pl band, corresponding to pump 22a is l9 greater than P2 band correspondin~ to pump 22b. Likewise P2 band is greater than P3 band corresponding to pump 22c band o ~ 21 and P3 band is greater than P4 band corresponding to pump 22d.
'o~ 22 (P1 band > P2 band > P3 band > P4 band).
K ~0~ 23 As used herein the terms P1, P2, P3, and P4, refer to a ~ o zw~ 24 delivery p~essure band. P1, P2, P~ and P4 are not discreet R 25 values but bands of pressure which includes the difference in .

2 ~ ~ ~ c3~

I The check valves 25a-d are each constructed to open at a preselected low differential pressure ~P sensed between the :~ downstream pressure in the IV line 16 and an upstream pressure 4 determined by the pump delivery pressure of a fluid pump 22a-d. The check valves 25a-d can thus be constructed and 6 arranged to allow fluid flow sequentially from pump 22a at 7 pressure P1, pump 22b at Pressure P2, pump 22c at pressure P3, 8 and pump 22d at pressure P~.
: 9 The infusion apparatus 10 is thus constructed to operate in a SASH process that includes the steps of:
1. connecting a first reservoir with a dosage of a saline solution, a second reservoir with a dosage of an l3 antibiotic solution, a third reservoir with a dosage of l4 a saline solution, and a fourth reservoir with a dosage of a heparin solution, to an IV line; and 16 2. sequentially discharging a dose of saline from the first reservoir at a pressure of Pl, a dose of 18 antibiotic from the second reservoir at a pressure of P2, l9 a dose of saline from the third reservoir at a pressure of P3, and a dose of heparin from the fourth reservoir at O O ~- 21 a pressure of P4 with P1 > P2 ~ P3 ~ P~-¢ >~o~3 22 A suitable fluid pump 22a-d for pumping or discharging :;~ ~bo~ 23 fluid solutions at a substantially constant pressure is shown o 3 ~ 24 in Figures 4, 5, 6A and 6B. In general each of the fluid pumps 22a-d will be of the same construction but the pumps 26 will be sized differently. For example each pump 22a-d may be :
; ' ~ 3 l sized to contain a predetermined volume or dosage of solution 2 which may be different. As an example the volumetric capacity 3of a pump 22a-d may be in the range of 20-250ml for an 4 antibiotic and 3-S ml for saline depending on a required S dosage. It is anticipated that the pump will be charged with 6 a solution at the pharmacy although it is contemplated that a , patient may charge some solutions.
8With reference to Figure 4 a pump 22a-d is shown. Each 9 pump 22a~d includes a housing 27a-d. An elastomeric membrane 26a-d is clamped between rings 40a-d and 44a-d and is then Il attached to the housing 27a-d and to a shell (not shown), or 12 to the carrier housing 34. Figure 4 also shows that the 13 housing 27a-d is formed with an inlet port 28a-d and an outlet 14port 30a-d. Each outlet port 30a-d of the pumps 22a-d is IS coupled to an outlet conduit 31a-d which in turn is coupled to 16 the IV line 16. Each check valve 2Sa-d is located in an 17 outlet conduit 31a-d situated between the outlet port 30a-d of 18 a pump 22a-d and the IV line 16. The individual components of l9 a pump 22a-d, however, are best seen in Figure 5.
20In Figure 5 the various components of a pump 22a-d are 21 shown in an exploded isometric and are arranged generally in the order in which they are to be assembled. Preferably, the 23 housing 27a-d is made of a hard plastic, such as 24 polycarbonate, and is of a material which is chemically compatible with the fluid to be infused into the user 12. For 26 purposes of the present invention, a contour surface 32a-d of 2 ~ 3 ho~sinq 7~-d can have any topology which will stret h the ~ membrane 26a-d into its nonlinear region of elasticity when ;~ these components are assembledO Preferably, however, the 4 contour surface 32a-d of housing 27a-d will follow and conform to the natural topology of the inflated membrane 26a-d as it transitions from linear to non linear. For the case shown in , the Figures, contour surface 32a-d is substantially hemispheric~al. On the other hand, as shown in the Figures, 9 the periphery 34a-d of housing 27a-d is folded outwardly from lo the contour surface 32a-d in order to facilitate the connection of the membrane 26a-d onto the housing 27a-d. The 12 housing 27a-d can be manufactured using any well known 13 manufacturing procedures, such as injection molding.
14 A thin wall tube which forms valve sleeve 36a-d, and a lo valve insert 38a-d are shown in Figure 3 in their positions 16 for insertion into the lumen of inlet port 28a-d. When 17 inserted into the lumen of inlet port 28a-d, the sleeve 36a-d 8 and valve insert 38a-d establish a one-way valve for the 19 housing 27a-d which permits the flow of fluid in only one direction through the inlet port 28a-d. Specifically, it is 21 important that each fluid pump 22a-d will be filled with fluid 22 through the inlet port 28a-d of each chamber but that fluid 23 not be able to leave the fluid pump 22a-d through the inlet 24 port 28a-d. A fluid may be loaded into an inlet port 28a-d under pressure utilizing a medical syringe ~not shown).
26 Additionally, it is important that during filling of the 2 ~

1 separate fluid pumps the sequence of filling be accomplished 2 from the highest to the lowest pressures.
:~Each pump 22a-d also includes an upper top ring 40a-d 4 which is engageable with a rib 42a-d that is located on the O circumference of membrane 26a-d. Upper ring 40a-d is also 6 engageable with a lower bottom ring 44a-d to effectively grip _ and hold the rib 42a-d of membrane 26a-d between the rings 8 40a-d and 4.4a d. These rings 40a-d and 44a-d can be of any 9 suitable rigid material such as polycarbonate which, when the rings 40a-d and 44a-d are joined together to support the flexible membrane 26a-d, will provide a firm foundation for 12 the membrane 26a-d.
13With specific regard to the membrane 26a-d, it is seen in 14 Figure 3 that the membrane 26a-d is substantially a circular sheet when in its unstretched condition. Further, this sheet 16 is formed with a raised rib 42a-d which, as mentioned above, 17 can be gripped between the rings 40a-d and 44a-d. Although it 18 will be appreciated that most elastomeric materials may be 19 suitable for the purposes of the present invention, the membrane 26a-d is preferably made of a natural rubber or 21 isoprene having a high elastic memory. Regardless of the 22 particular material used for membrane 26a-d, however, it is 23 important that the membrane 26a-d be chemically compatible ~ with the fluid medicament which is to be infused to the user 12 from each pump 22a-d. If there is no compatibility between 26 the membrane 26a-d and the fluid medicament a drug barrier ~13-2 ~ c~

1 needs to be created between the two. To establish such a drug 2 barrier, the membrane 26a-d can be appropriately coated so 3 that the particular surface of membrane 26a-d which is to be 4 placed in contact with the contour surface 32a-d of housing , 27a-d will not chemically interact with the fluid medicament 6 in the pump 22a-d. Alternatively, though not shown in the _ Figures, a medicament compatible membrane can be held with the 8 membrane 26a-d between the rings 40a-d and 44a-d. With this 9 combination, the medicament compatible membrane is positioned between the membrane 26a-d and the contour surface 32a-d of housing 27a-d when these components are assembled. For 12 purposes of the present invention, the portion of membrane 13 26a-d which is circumscribed by the rib 42a-d is preferably of 14 uniform thickness. It is recognized, however, that thickness ~5 may be varied across the membrane 26a-d as long as the 16 resultant topology creates a nonlinear elastomeric behavior 17 for the membrane 26a-d. In addition, the thickness of the 18 membranes 26a-d will in part be different for each pump 22a-d 19 for achieving a different operating pressure for each pump 22a-d.
O 0 0~ 2i The cooperation of the various structural elements ofe 0 ~ 22 each pump 22a-d will be best appreciated with reference to ~0~ 23 both Figures 6A and 6B. First, in Figure 6A it is seen that 3 ~ ~ ~ 24 the upper top ring 4Oa-d is joined to the lower bottom ring 2S 44a-d to grip and hold rib 42a-d of membrane 26a-d 26 therebetween. The rings 40a-d and 44a-d can be joined ~ 3-~ ~

1 together by any of several means, such as ultrasonic welding 2 or solvent bonding. Additionally, as seen in Figure 6A, the 3 periphery 34a-d of housing 27a-d is joined to upper top ring 4 40a-d. When housing 27a-d is joined to upper top ring 40, the contour surface 32a-d of housing 27a-d stretches membrane 26a-6 d substantia]ly as shown. Importantly, the dimensions of both 7 membrane 26a-d and contour surface 32a-d are such that this 8 stretching takes the membrane 26a-d into its nonlinear region 9 of elasticity. The joining of housing 27a-d to upper top ring 40a-d also establishes a potential chamber or reservoir 50a-d Il between the membrane 25a-d and contour surface 32a-d.
12 Referring now to both Figures 6A and 6B, it can be 13 appreciated that as fluid is introduced through the inlet port 14 28a-d of housing 27a-d and into the potential chamber 50a-d under the pressure of a syringe, or some other pumping means, 16 any air in the system will first be vented to the outlet port l7 30a-d along the indentation 52a-d which is formed into contour 18 surface 32a-d. This, of course, always happens when the air ~ 19 pressure is less than the pressure necessary to distend the ¢ 20 membrane 26a-dO Then, with outlet port 30a-d blocked to > NO prevent the flow of liquid medicament from chamber 50a-d, the ~o~ 22 elastomeric membrane 26a-d will begin to expand as additional K ~0~ 23 liquid medicament is introduced into the potential chamber 50.
~ 2~ It is important to the present invention that in order to ,~ 25 create a substantially constant fluid pumping pressure in the 26 chamber 50a-d, the expansion, and subsequent contraction, of ~ membrane 26a-d be entirely accomplished with the exception of 2 the last or lowest pressure fluid pump 22d while membrane ~ 26a-d is in its nonlinear region of elasticity. As previously 4 stated the elastomeric membrane 26a-d is initially stretched into its nonlinear region of elasticity during assembly of 6 each pump 22a-d. It can be appreciated that during subsequent 7 loading or a fluid into chamber 50a-d, a pump means such as a 8 medical syringe must overcome the force which is exerted by 9 the elastomeric membrane 26a-d. There must then be additional lo non-linear stretching of the membrane 26a-d to form and expand 11 the chamber 50a-d as shown in Figure 6B.

12 Viewed from an energy standpoint, a fluid must be 13 introduced under a pressure sufficient to overcome the 14 potential energy of the initially stretched membrane 26a-d and form the chamber 50 a-d. This total amount of energy minus 16 what has been lost through heat loss and elastomeric 17 hysteresis is thus available for displacing fluid from the 18 chamber 50a-d at a substantially constant delivery pressure.
19 Further, because of the initial non-linear stretching of the membrane 26a-d, even after complete discharge of a fluid, a ~ ~c 21 residual force is maintained by the membrane 26a-d acting upon ~o~ 22 the contour surface 32a-d.
K ~0~ 2~ As previously stated each pump 22a-d must be sized to U ~ ~w~ 2~ deliver a predetermined volume of fluid solution over a substantially constant predetermined delivery pressure. A
26 size of the pump 22a~d may thus be adjusted to achieve a .

~ 3 l predetermined volume. For achieving a predeter~ined delivery 2 pressure a thickness of the elastomeric membrane 26a-d as well .3 as thP material may be selected as required.
4 In general, the delivery pressure of a pump 22a-d will vary with the thickness of t~e elastomeric membrane 26a-d.
6 Likewise the delivery pressure will vary with the modulus of 7 elasticity of the material selected for the elastomeric 8 membrane 26a-d.
9 Figures 7A and 7B illustrate representative volume versus pressure characteristics of the four fluid pumps 22a-d.
11 Curves Ca_d of Figure 7A illustrate the volume versus pressure 12 characteristics of pumps 22a-d respectively. In general each 13 pump 22a-d is constructed to deliver fluid over a relatively 14 constant pressure band. As is apparent pump 22a operates at the highest pressure band followed by pump 22b, 22c and 22d ~6 respectively. These operating pressures correspond to the 17 operating pressures or pressure bands Pl > P2 > P3 > P4 shown 18 in Figure 3. An illustrative range of pressures may be in the 19 range of 1-20 psig. Figure 7B illustrates a volume delivered ~ 20 by the separate chambers over a time sequence.
O ~ ~0 21 The check valves 25a-d for each pump 22a-d must be O Z n ~ configured to crack with a relatively small pressure ,ou 23 differential ~Y between the respective operating pressures Pl 3 ~ . P4 for the pumps 22a-d. Such check valves 25a-d are commercially available and in general function as shown in the 26 schematic il]ustration of Figure 8. Additionally, the check I valve 25a downstream of pump 22a may be eliminated if desired.
2 In addition the configuration noted in Figure 2 with four 3 separate fluid pumps 22a-d may also be varied, as long as four 4 separate reservoirs or chambers each at a different pressure ~5 are provided. As an example, a single pump having a single 6 elastomeric membrane that covers a plurality of juxtaposed 7 chambers may be provided. The thickness of the elastomeric % membrane ma,y be varied to provide a pressure differential 9 between the separate chambers.
Figure 9 illustrates such an alternative embodiment Il infusion apparatus. Alternate embodiment infusion apparatus l2 51 includes a housing 53 having a plurality of contour l3 surfaces 54a-d formed thereon. A single concentric 14 elastomeric membrane 56 is mounted in operative alignment with the contour surfaces 54a-d substantially as previously 16 described for elastomeric membrane 26a-d. Concentric 17 elastomeric membrane 56 is formed however, with a varying l8 thickness for providing chambers corresponding to contour , 19 surfaces 54a-d. The pumping or delivery pressure from each '~ 20 chamber can thus be varied as required.
O 0 0~ 21 As shown in plan view in Figure 10 a single infusion ~'0-~ 22 apparatus 60 for a SASH process may include four separate K ~0~ 23 chambers S,A,S,~, concentrically arranged and divided. Figure ~ 3 ~ 24 lOA illustrates a single infusion apparatus 62 having three % 2s separate and concentrically arranged chambers (S,A,S). In 26 either case the largest chamber (A) is in the center.

, .

l Figure ll illustrates yet another infusion apparatus 64 2 formed with a shell 68 and separate chambers formed by a 3 single elastomeric membrane 66. The shell 66 may be sized to 4 contain a fixed volume for each separate chamber.
Thus the invention provides a method and apparatus for 6 infusing a plurality of medical solutions in a controlled _ sequence. The apparatus of the invention is simple in 8 construction and may operate automati_ally in a SASH process.
9 Moreover the method and apparatus of the invention is suitable for use by a mobile or ambulatory patient.
11 While the particular portable IV infusion apparatus as 12 herein shown and disclosed in detail is fully capable of 13 obtaining the objects and providing the advantages herein 14 before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the 16 invention and that no limitations are intended to the details 17 of the construction or design herein shown other than as 18 defined in the appended claims.

~8 Y o o ~ ,7 S ! ~S ~'7 (~7 7 ~j ~ 8 23 ~ 25 i ~z;

Claims (23)

1. A method for infusing a plurality of medical solutions comprising connecting a first and a second reservoir to a single IV line;
pressurizing a first fluid in the first reservoir to a pressure band of P1 with an elastomeric membrane;
pressurizing a second fluid in the second reservoir to a pressure band of P2 with an elastomeric membrane with P1 > P2;
sequencing fluid flow such that the first reservoir is effectively discharged of fluid prior to the second reservoir discharging fluid.

2. The method as recited in claim 1 and further comprising:
discharging the first reservoir at a substantially constant pressure P1; and discharging the second reservoir.

3. The method as recited in claim 2 and wherein:
pressurizing the first and second reservoirs is with an elastomeric membrane attached to a contour surface to stretch the membrane into a nonlinear region of elasticity to form a chamber therebetween.

4. The method as recited in claim 3 and wherein:
sequencing fluid flow is by sensing a differential pressure between the first and second chambers and the IV
line with a check valve to provide a sequential flow from the first reservoir to the IV line and then from the second reservoir to the IV line.

5. A method for infusing medical solutions in a SASH
process comprising:
pressurizing with an elastomeric membrane a first reservoir for a fluid saline solution to a pressure band of P1, a second reservoir for a fluid antibiotic solution to a pressure band of P2, a third reservoir for a fluid saline solution to a pressure band of P3, and a fourth reservoir for a fluid heparin solution to a pressure band of P4, with P1 > P2 > P3 > P4;
connecting each reservoir in flow communication to an IV line for a patient;
discharging fluid sequentially from the first reservoir, then the second reservoir, then the third reservoir, and then the fourth reservoir with each reservoir substantially discharged of fluid prior to a next reservoir discharging fluid.

6. A method as recited in claim 5 and further comprising:
discharging each reservoir but the fourth reservoir at a substantially constant pressure.

7. A method as recited in claim 6 and wherein:
pressurizing the first, second, third, and fourth reservoirs is with an elastomeric membrane by nonlinear contraction of the membrane while the membrane remains in a region of nonlinear elasticity.

8. A method as recited in claim 7 and further comprising:
sequentially discharging fluid is by sensing a pressure differential between reservoirs for sequentially valving the reservoirs.

9. The method as recited in claim 8 and wherein:
the elastomeric membrane is stretched over a contour surface substantially hemispherical in shape.

10. The method as recited in claim 8 and wherein:
the pressures P1, P2, P3 and P4 are controlled by a predetermined thickness of the elastomeric membrane.

11. The method as recited in claim 8 and wherein:
different elastomeric membranes are utilized for each reservoir and the pressures P1, P2, P3 and P4 are controlled by a modulus of elasticity of the elastomeric membrane.

12. The method as recited in claim 8 and wherein the pressures P1, P2, P3 and P4 are controlled by a pre-determined thickness and modulus of elasticity of the elastomeric membrane.

13. An apparatus for infusing medical fluids comprising:
a first and second fluid pumping means coupled to an IV line for discharging fluid from a first chamber at a substantially constant pressure of P1 and for discharging fluid from a second chamber at a substantially constant pressure of P2; and valving means for controlling fluid flow sequentially from the pumping means such that the first chamber is substantially discharged prior to initiating and discharging flow from the second chamber.

14. The apparatus as defined in claim 13 and wherein each pumping means comprises:
a housing having a fluid port, the housing being formed with a surface having a periphery and a predetermined contour circumscribed by the periphery; and an elastomeric membrane attached to the periphery over said contour surface to stretch the membrane into a nonlinear region of elasticity and create a potential chamber between the stretched membrane and the housing for receiving fluid therein through the port and expelling fluid therefrom through the port by nonlinear contraction of the membrane at a substantially constant pressure.

15. The apparatus as defined in claim 14 and wherein:
four of the pumping means are coupled to the IV line for use in a SASH process.

16. The apparatus as defined in claim 15 and wherein:
the valving means comprises a plurality a check valves located between the fluid pumping means and the IV
line to sense a differential pressure between the pumping means and IV lines and initiate a sequential fluid flow from the fluid pumping means.

17. An infusion apparatus for infusing medical fluids comprising:
first, second, third, and fourth pumping means for pumping fluids at a substantially constant pressure bands of P1, P2, P3 and P4 respectively from first, second, third and fourth chambers with Pl > P2 >P3 > P4;
means for mounting and coupling said pumping means to an IV conduit; and valving means for sequentially completely discharging fluid from the first then the second then the third, and then the fourth chambers.

18. An infusion apparatus as defined in claim 17 and wherein each pumping means comprises:
means for stretching the membrane into its region of nonlinear elasticity;
means for mounting the membrane on said stretching means to create a potential fluid chamber therebetween;
and means for expelling fluid from the potential chamber by nonlinear contraction of the membrane while the membrane remains in the region of nonlinear elasticity.

19. An infusion apparatus as recited in claim 18 wherein the stretching means is a housing formed with a surface having a periphery and a predetermined contour circumscribed by the periphery and wherein the elastomeric membrane is attached to said periphery over the contour.

20. An infusion apparatus as defined in claim 19 and wherein:
the valving means comprises three check valves located between the second, third and fourth pumping means and the IV line.

21. An infusion apparatus as defined in claim 18 and wherein:
the chambers are formed on a single housing and a single membrane of a varying thickness covers the reservoirs.

22. An infusion apparatus as defined in claim 21 and wherein:
the chambers are concentrically arranged and divided.

23. An infusion apparatus as defined in claim 21 and wherein:
the chambers are formed by a cylindrical shell separated into separate chambers by the elastomeric membrane and sized to contain a fixed volume per chamber.