Implantable infusion pump

Details Implantable infusion pump Implantable infusion pump

2001-01-04

2003-12-23

Mendez, Manuel (Department: 3763)

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

C604S892100

Reexamination Certificate

active

06666845

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The present invention concerns an implantable infusion pump, and in particular, an implantable infusion pump as well as independent components therefor that enable securing the pump within a living body, multi-stage filtration, and protection of a fluid-delivery catheter in and about the pump housing while improving volumetric efficiency of the pump configuration.
BACKGROUND OF THE INVENTION
The present invention relates to an implantable infusion pump for infusing drugs or other chemicals or solutions into a body wherein the infusion pump is implanted. Further, in at least one embodiment, the present invention relates to an implantable infusion pump that compensates for changes in both ambient pressure and ambient temperature so as to accurately control the flow rate of infusates from the implantable infusion pump into the body.
Infusion pump designs were rarely seen in medical literature until the 1950s. Most of these early infusion pumps were extracorporeal devices of various designs. One such device included a reciprocating air pump driven by an electric motor. Yet another design considered comprised a metal housing for a glass syringe and a compression chamber fed by a tank of nitrogen gas. Yet another such infusion pump included a motorized syringe pump which included an electric motor connected to the worm drive that moved a syringe plunger by a gear box. The gears were interchangeable such that replacement of the gears permitted different delivery rates. Yet another infusion pump included a syringe plunger driven by a rider on a threaded shaft. While this is but a sampling of such devices, it should be appreciated that numerous other designs were considered and used for extracorporeal infusion devices.
Modern constant-flow implantable infusion devices, or implantable pumps, for delivering an infusate (e.g., medicaments, insulin, etc.) commonly have a rigid housing that maintains a collapsible infusate reservoir. The housing includes a needle-penetrable septum that covers a reservoir inlet. A flow passage is provided between the reservoir and an exterior surface of the device, such flow passage includes, or defines, a restrictor to establish a maximum output infusate flow rate. At the flow passage outlet, a flexible delivery catheter is provided.
Practically, such a device is implanted at a selected location in a body so that (i) the inlet septum is proximate to the patient's skin and (ii) a distal end of the catheter is positioned at a selected delivery site. Infusate can then be delivered to the infusion site by forcing such fluid from the device reservoir. When the infusate reservoir becomes empty, the reservoir is refillable through the septum inlet by injecting a new supply of infusate through the apparatus' inlet septum. Due to the location of the device in relation to the skin of the patient, injection can be readily accomplished using a hypodermic needle (or cannula).
Infusate is expelled from the reservoir to an infusion site by collapsing the reservoir. While some infusion pumps use an electrically powered mechanism to force infusate from the reservoir, other such devices commonly use a two-phase fluid, or propellant, that is contained within the rigid housing and is further confined within a fluid-tight space adjacent to the infusate reservoir.
The propellant is both a liquid and a vapor at patient physiological temperatures, e.g., 98.6° F., and theoretically exerts a positive, constant pressure over a full volume change of the reservoir, thus effecting the delivery of a constant flow of infusate. More particularly, when the infusate reservoir is expanded upon being refilled, the propellant is compressed, where a portion of such vapor reverts to its liquid phase and thereby recharges the vapor pressure power source of the pump. The construction and operation of implantable infusion pumps of this type are described in detail, for example, in U.S. Pat. Nos. 3,731,681 and 3,951,147.
Gas-driven infusion pumps typically provide a cost-effective means to deliver a consistent flow of infusate throughout a delivery cycle. Notwithstanding, the rigid housing of the gas-driven infusion pump allows both environmental temperature and atmospheric pressure to affect an output fluid flow. With some drugs, particularly those having small therapeutic indices, such changes in drug infusion rates are undesirable and, in certain situations, unacceptable.
Circumstances readily exist where either environmental temperature or pressure can rapidly change a significant amount. For example, in regard to temperature, an internalized pump pressure can change as much as 0.5 psi for each 1° F. change in body temperature. Thus, for example, assuming a pump driving force of 8 psi at 98.6° F., a twenty-five percent (25%) increase in pressure and drug flow rate can result from a fever of only 102.6° F.
An even more serious situation results from changes in atmospheric pressure. Although minor variations in atmospheric pressure at any given location on earth does not significantly affect delivery flow rates, with modern modes of transportation, a patient can rapidly change altitude during travel, such as when traveling in the mountains or when traveling by plane.
Again, the rigid housing of the conventional, gas-driven infusion pump is intended to produce a constant internal pressure (at constant temperature) independent of the external pressure. Largely due to compliance by the lungs and venous circulatory system, hydrostatic pressure within the human body closely follows atmospheric pressure. The net effect is a pressure differential across the fluid flow restrictor of infusion pump (typically a capillary tube or the like) which changes linearly with external pressure. Consequently, a delivered infusate flow rate can increase as much as forty percent (40%) when a patient takes a common commercial airline flight.
A viable solution to address changes in atmospheric conditions for constant-flow infusion pumps is disclosed in U.S. Pat. No. 4,772,263, herein incorporated by reference in its entirety. Specifically, in place of the conventional rigid enclosure that maintains a two-phase fluid, the disclosure teaches forming the fluid reservoir between a rigid portion (which maintains at least the inlet septum and the restrictor) and a flexible drive-spring diaphragm. The diaphragm is exposed to the body of the patient and “senses” internal body pressure so as to compensate for changes in the internal body pressure caused by changes in atmospheric pressure and temperature.
While the disclosure of U.S. Pat. No. 4,772,263 provides a foundational description for a pump having a drive-spring diaphragm capable of constant-flow delivery, such patent does not fully consider alternatives for restrictor and/or flow passage outlet placement that may provide for a safer practical configuration as well as capitalize on the unique structure of the drive-spring diaphragm.
Moreover, U.S. Pat. No. 4,772,263 is silent to a means to incorporate a conventional bolus port with its unique drive-spring diaphragm design. A bolus port enables direct infusion of a fluid through the delivery catheter. A bolus port is typically a separate septum that is in fluid communication with an outlet of an associated infusion pump and a delivery catheter therefor. Typically, certain one-way valving structures can prevent fluid that is injected through the bolus port from-flowing upstream to the infusate reservoir of the infusion pump.
SUMMARY OF THE INVENTION
The present invention relates to an infusion pump for implantation in a living body. The infusion pump includes a housing having a fluid chamber, wherein the housing includes a spring-energy source for driving an infusate (e.g., medicaments, insulin, etc.) out of the fluid chamber and compensating for changes in internal body pressure and/or internal body temperature. The housing further includes an inlet conduit in communication with the fluid chamber and an outlet conduit in communication with the fluid chamber that leads to an infusion

Affiliated with

Also associated with

Rating

Implantable infusion pump does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Implantable infusion pump, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Implantable infusion pump will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3124430