CA1191760A - Infusate pump - Google Patents

Abstract

Abstract of the Disclosure Infusion apparatus includes a housing with an infusate chamber in the housing and means for conducting infusate from the chamber through a restrictive outlet passage to an additional small chamber having an entrance port closed by a self-sealing penetrable septum. An exit tube from the small chamber leads directly to a cannula at the infusion site so that liquid can be injected into the small chamber through its septum and delivered directly to the infusion site without backflowing into the infusate chamber.

Description

This invention relates to infusion apparatus. It relates especially to such apparatus which can be implanted and refilled and recharged periodically so that it can remain in the patient's body for a prolonged period.

Background Df the Invention Relatively recently infusion apparatus has been developed which can be implanted in the body and remain there for a prolonged period. The apparatus can be refilled with infusate without having to remove the apparatus from the body. This refilling is accomplished by injecting additional infusate through a penetrable septum in the apparatus which septum is located directly under the patient's skin. In some cases, the act o~
refilling the apparatus with infusate also recharges the apparatus's power source so that the device can operate uninterruptedly to dispense infusate such as insulin, heparin or a chemotherapeutic agent at a very small rate over a long time. ~xamples of infusion apparatus of this

2~ general type are disclosed in U.S. Patents 3,951,147 and 4,258,711, both owned by the assignee of the present application.
Some infusion apparatus of this type such as the one described in the latter patent have the capability of dispensing a continuous basal dose of infusate to the patient as well as larger bolus doses when the occasion demands it. For example, a patient may receive a continuous dose of insulin based on the average glucose level in his blood. Then, right after mealtimes, when the glucose level usually rises, the pump can be made to dispense a bolus dose of insulin to compensate for that increased glucose level due to the ingestion of food. In order to provide such dual dosage capability for any 7~

reasonable length of time, the pump must have a large infusate reservoir to provide both the basal and bolus requirements or two smaller reservoirs, one o:E which contains the infusate at the basal concentration and the other of which contains infusate at a higher bolus concentration. In either event, the inclusion of the bolus dispensing capability inc.reases the overall size of the pump envelope.
In some instances, however/ a supplement to the basal infusate flow is required relatively infrequently. For example, it may only be introduced to add an angiographic solution to the infusate so that the area distribution in the body being infused can be monitored from time to time. It would be desirable in such cases to provide this capability in a pump having a minimum overall size or envelope. It is also essential that this added capability be provided without adversely affecting the basal infusate contained in the apparatus or its flow to the patient.
Summary of the Invention Accordingly, the present invention provides implantable infusion apparatus comprising: A. an infusate reservoir; B. an entry port into said infusate reservoir; C. a self-sealing penetrable sep-tum closing said entry port; D. a small fixed-volume chamber; E. an entry port into said chamber; F. a second self-sealing penetrable septum closing -the entry port in-to said chamber, the exposed surfaces of both septa being located near one another in substantially the same plane or in parallel planes so that, when the apparatus is implanted in -the body, both said septa are access:ible extracorporeally by transcutaneous injection at nearby locatlons on the body surface; G. means defining a Fluid i.n]et passacJe extending :from said reservoir -to said chamber; ~1. means for mov:ing the contents of said reservoir to said chamber; and I. means defining a substan-t.ially unres-trie-ted fluid outlet passage crom saicl chamber ~or connec-t,ion to a conduit leading to an intusion si-te so tha-t an injection of inEusate i.nto said chamber flows substan-t:ially immecliately -to the infusion site.
The invention also provides infusion apparatus cornprising A. a housing; B. a container moun-ted inside the housing, said container defining along with the housing (1) a first chamber inside the container, and (2) a second chamber outside the eon-tainer, but inside the housing; C. an entry port into one of said ehambers; D. a self-sealing penetrable septum elosing said en-try por-t; E. a third small fixed-volume chamber; F. an en-try por-t into the third chamber; G. a seeond self-sealing penetrable septum closing the entry port into the third ehamber; H. means defining a fluid inlet passage extending from said one ehamber to the third chamber; I. means in -the other of said first and second ehambers for moving the eontents of said one chamber -to said third ehamber;
and J. means defining a substan-tially unrestricted fluid outlet passage from the third chamber for conneetion to a eannula leading to an infusion site so tha-t an injeetion of infusate into the third chamber flows substantially immediately to the infusion si-te.
In general, -the present pump ean be situated ou-tsi.de or inside the body. Basieally, it eomprises an infusate reservoir, a pump for eonduc-ting infusa-te from that reservoir to a catheter positioned at an infusion site in the patient and a septum-sealed por-t in fluid communication with -the flow path from the reservoir downstream frorn-the pump whieh allows the fluid output from the '7~

pump to be supplementecl by ~luid injected into the por-t -thxough its septum. 'i'he invention has par-ticular applicat:ion to implant-able infusion apparatus. Accordingly, it will be clescribed in tha-t con-tex-t. :Lt should be unders-tood, however, that it can also be applied -to external infusion devices.
The pump includes a housing containing an inEusate reservoir, preferably in -the form of a metal bellows capsule. An entrance port into the interior of the bellows is closed by a pene-trable septum mounted in the housing wa]l so that, when the apparatus is implanted, the septum is located directly under the patient's skin. An outlet port leading from the in-terior of the bellows capsule communicates with an outle-t conduit which extends exteriorly of the housing. The bellows capsule is filled with infusate by percutaneous injection through the penetrable septum.

3a Means are provided inside the housing and outside the bellows for compressing the bellows, thereby to expel the infusate therein through the outlet conduit. One preferred means for exerting compressive force on the bellows capsule is a fluid pressure power cell such as disclosed in the aforesaid patents. Of course, various other battery-operated or mechanical devices may be employed to progressively compress the bellows. Flow of infusate from the capsule is maintained constant by a l~ flow restriction in the outlet conduit.
Instead of leading directly to a catheter at the infusion site as described in those prior patentsl the restricted outlet conduit from the bellows reservoir connects to the catheter by way of a small chamber located inside or outside the housing. The chamber is formed with an entry port containing a septum which is also located directly under the patient's skin when the apparatus is properly implanted. Various types oE
liquids can be introduced into this chamber by percutaneous injection through its septum. Those fluids will mix with the infusate being dispensed from the bellows reservoir and be conducted by the catheter to the same infusion site in the patient's body. These additive liquids may comprise radio-opaque material, higher concentrations of infusate or various other types of liquids depending upon the particular patient's medical problem. Since the chamber is located downstream from the flow restriction leading from the infusate reservoir, in practice almost all liquid injected into that chamber

3~ flows through the catheter to the infusion site.
Thus, the present pump has the capability of dispensing infusate for a prolonged period, with that infusate being supplemented when needed by slugs of other liquids which might be desirable for proper patient '74~
. ~

s treatment. Yet this capability is achieved by a single device which is contained in a small envelope so that its implantation in the patient does not cause undue patient discomfort.

~rief 4es~criptiP-n~-p-f~the D~awing For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description, taken in connection with the accompanying drawing, in which:
FIG. 1 is a diagrammatic view illustrating the infusion apparatus implanted in the body; and FIG. 2 is a sectional view on a much larger scale illustrating the elements of the FIG. 1 apparatus in greater detail.

Des~riptiPn~-p~the~pFeferFed ~mbPdiment Referring to FIG. 1 of the drawing, the present apparatus indicated generally at 10 is shown implanted into a subcutaneous pocket in the abdominal wall of a patient P. The apparatus includes a generally cylindrical housing 12 which contains a supply of infusate. That infusate is dispensed from the apparatus through an unrestricted delivery cannula 14 leading from the housing 12 to an infusion site. In this case the cannula is shown implanted into the hepatic artery H via the gastroduodenal artery G.
When the supply of infusate in the housing 12 is exhausted, the apparatus can be refilled by subcutaneous injection through a self-sealing septum 16 in housing 12.
When the apparatus is properly implanted, that septum is located directly under the patient's skin and is thus accessible to a syringe needle. In some pumps of this general type, that refilling operation also recharges the '7~

96A~076 power source which expels the infusate from the housing 12 to the patient.
For some patients, the physician may wish to deliver a bolus dose of infusate to the patient or momentarily infuse another substance into the patient such as a radio-opaque material for an angiogram, tracer dye microspheres which are opaque to X-rays or gamma rays.
In the present apparatus, this is accomplished by subcutaneous injection through a second septum 18 located in an extension 12a of housing 12. Septum 18 is spaced from septum 16 on the same side of housing 12.
Accordingly, it is also located directly under the skin and is equally accessible to penetration by a syringe needle.
The substance injected through septum 18 does not mix with the infusate in housing 12. Rather, i~ is delivered directly to cannula 14 so it flows immediately to the infusion site through the cannula. Accordingly, the patient receives the benefit of that substance immediately after its injection. The inclusion of the additional septum 18 gives the apparatus 10 the ability to deliver a slug of infusate or other liquid when needed without materially increasing the overall size of the apparatus. Accordingly, it makes the apparatus quite useful for those cases where it is desirable to deliver a second substance to a patient on an occasional basis.
Turning now to FIG. 2, the housing 12 is a generally cylindrical container which is about the size of a small hockey puck. The container is made of a suitable material such as titanium which is compatible with the human system. Positioned in the container is a bellows capsule 24 having an open end mounted to a header 12b at the top of the container 12, the opposite end of the bellows capsule being closed. Thus the bellows defines a '7~

first chamber 26 inside the bellows and a second chamber 28 outside the bellows, but inside the housing 12.
Formed in header 12~ is an entry port 32 which extends from chamber 26 through header 12b. The outer end of port 32 is closed by the septum 16. A porous needle stop 33 is positioned at the inner end of port 32.
Also formed in the header is an exit port 34 containing a filter 36. That port communicates with an outlet tube 38 containing a fluid restricter 38a and whose opposite end communicates with an inlet tube 40 leading to a small chamber 42 in the housing extension 12a. An exit tube 43 leads from the chamber 42 to cannula 14. Also, an entry port 44 is formed in the top of chamber 42 which port is closed by septum 18. Additionally, a needle stop 46 is positioned at the bottom of chamber 42.
Normally, chamber 26 is filled with infusate by injection of the infusate through septum 16. Chamber 28, on the other hand, is filled with a two-phase fluid which vaporizes at physiological temperatures so that it exerts a pressure on the bellows capsule 24 tending to collapse it, thereby expelling the infusate through the exit port 34 and the restrictive outlet tube 38 to chamber 42.
From that chamber the infusate flows through the cannula 14 to the infusion site, to wit, artery H
(FIG. 1).
When the supply of infusate in chamber 26 is exhausted, it can be refilled by injecting additional infusate through septum 16 using a hypodermic syringe.
The extension of the bellows capsule 24 during this refilling operation exerts a pressure on the two-phase fluid in chamber 28 which condenses that fluid thereby recharging the fluid power cell. The operation of such a fluid power cell is fully described in the aforesaid two '7~

patents as well as in patent 3,731,681. Thus the infusate in chamber 26 can be dispensed to the patient at a very low flow rate to meet his long term requirements, the apparatus being refilled periodically, e.g. every thirty days, as needed.
In those situations where it would be desirable to infuse a larger concentration of the same infusate or a different liquid altogether into the patientls artery H, this is accomplished by injecting that additional liquid through septum 18 directly into chamber 42 using a standard hypodermic syringe shown in dotted lines at N in FIG. 2. That liguid then flows without restriction through outlet tube 43 and cannula 14 directly to the infusion site. Since chamber 42 is located downstream from restriction 38a, that additional substance is forced to flow directly through the cannula. Very little upstream flow through the restricted tube 38 into infusate chamber 26 will occur. Accordingly, substantially the entire volume (i.e. 99.99%) of the substance injected into chamber 42 flows immediately to the infusion site as a slug, rather than being dispensed to the pa-tient over a longer term along with the infusate from chamber 26.
In those apparatus 10 having a very low restriction 38a in the outlet tube 38, such backflow from chamber 42 into chamber 26 may be prevented by a check valve in the outlet tube upstream from chamber 42. Such a valve is indicated in dotted lines at 48 in FIG~ 2.
It can be seen therefore that the incorporation of chamber ~2 with its septum 18 into the apparatus downstream from the restrictive outlet tube from the infusate reservoir 26 provides a convenient means for injecting additional liquids directly into the patient's arterial system whenever that is required. The 3::~'7~

incorporation o r that adcli-tional chamber in-to the appara-tus does no-t materially increase the vo:lume of housing 12 or the overall cos-t or complexity of the apparatus. Ye-t it makes the appara-tus much more versatile.
I-t will thus he seen tha-t the objec-ts set forth above, among those made apparent from the preceding description, are efficiently at-tained. Also, cer-tain changes may be made in the above construction withou-t departing from the scope of the inven-tion. For example, a mechanical pump such as a peristaltic pump may be employed in lieu of -the vapor pressure pump to conduct infusate from chamber 26 -to ca-theter 16. Therefore, it is intended -that all matter contained in the above descrip-tion or shown in the accompanying drawing be interpreted as illustrative and not in a limiting sense.
It is also to be ~nderstood that -the following claims are intended to cover all of the generic and specific features of the invention herein described.

Claims (7)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Implantable infusion apparatus comprising:
A. an infusate reservoir;
B. an entry port into said infusate reservoir;
C. a self-sealing penetrable septum closing said entry port;
D. a small fixed-volume chamber;
E. an entry port into said chamber;
F. a second self-sealing penetrable septum closing the entry port into said chamber, the exposed surfaces of both septa being located near one another in substantially the same plane or in parallel planes so that, when the apparatus is implanted in the body, both said septa are accessible extracorporeally by trans-cutaneous injection at nearby locations on the body surface;
G. means defining a fluid inlet passage extending from said reservoir to said chamber;
H. means for moving the contents of said reservoir to said chamber; and I. means defining a substantially unrestricted fluid outlet passage from said chamber for connection to a conduit lead-ing to an infusion site so that an injection of infusate into said chamber flows substantially immediately to the infusion site.

2. Infusion apparatus comprising A. a housing;
B. a container mounted inside the housing, said container defining along with the housing (1) a first chamber inside the container, and (2) a second chamber outside the container, but inside the housing;
C. an entry port into one of said chambers;
D. a self-sealing penetrable septum closing said entry port;
E. a third small fixed-volume chamber;
F. an entry port into the third chamber;
G. a second self-sealing penetrable septum closing the entry port into the third chamber;
H. means defining a fluid inlet passage extending from said one chamber to the third chamber;
I. means in the other of said first and second chambers for moving the contents of said one chamber to said third chamber;
and J. means defining a substantially unrestricted fluid outlet passage from the third chamber for connection to a cannula leading to an infusion site so that an injection of infusate into the third chamber flows substantially immediately to the infusion site.

3. The apparatus defined in claim 2 wherein said inlet passage defining means include a fluid restriction.

4. The apparatus defined in claim 2 wherein the inlet pass-age defining means include check valve means for preventing fluid flow from said third chamber to said one chamber.

5. The apparatus defined in claim 2 wherein A. the container is collapsible; and B. the moving means comprise a fluid power cell con-tained in said other chamber for collapsing the container.

6. The apparatus defined in claim 2 wherein the first and second septa are spaced apart from one another on the same outside wall of said housing.

7. The infusion apparatus defined in claim 1 and further including means for inhibiting back-flow of fluid from said chamber to said reservoir.