Negative pressure pump

Details Negative pressure pump Negative pressure pump

1999-02-19

2001-09-04

Nguyen, Anhtuan T. (Department: 3734)

Surgery

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

Treating material introduced into or removed from body...

C604S891100, C604S505000

Reexamination Certificate

active

06283943

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to medication infusion pumps, more particularly implantable infusion pumps.
BACKGROUND OF THE INVENTION
Medication infusion pumps that supply a medication to a patient, in particular implantable infusion pumps, are known. Known infusion pumps typically include a housing that contains a medication chamber and a propellant chamber, together with appropriate means for loading the selected medication into the medication chamber and for supplying the medication to the patient. One known type of infusion pump includes a reservoir containing a gas at a pressure below atmospheric pressure. Such infusion pumps are characterized as “negative pressure” pumps. Negative pressure pumps offer the advantage of facilitating fill of the medication chamber by acting to draw in the medication from a hypodermic needle or other supply source into the medication chamber. Such pumps also have the advantage of inhibiting undesirable leakage from the medication chamber.
Negative pressure infusion pumps are described, for example, in U.S. Pat. No. 4,191,181, to Frenetzki et al.; U.S. Pat. No. 4,373,527, to Fischell; U.S. Pat. No. 4,511,355, to Frenetzki et al.; U.S. Pat. No. 4,573,994, to Fischell et al.; and U.S. Pat. No. 5,514,103, to Srisathapat et al. In a typical negative pressure infusion pump, a medication is drawn into the medication chamber under the action of a gas maintained in a flexible reservoir at negative pressure. Once the medication is drawn into the medication chamber, the medication is subsequently delivered to the patient via a separate pumping mechanism.
Modern environmental concerns mandate that gases employed in “negative pressure” pumps be environmentally benign. It is of particular concern to avoid gases that have an adverse effect on ozone.
A need exists for a negative pressure infusion pump that employs an environmentally acceptable gas in its gas reservoir.
SUMMARY OF THE PREFERRED EMBODIMENTS
In accordance with one aspect of the present invention, there is provided a medication infusion pump that includes a housing, a medication chamber defined in the housing, a pumping mechanism for supplying the medication from the medication chamber to a patient, a reservoir defined in the housing and adapted to apply a predetermined negative pressure to a medication within the medication chamber, and a gas within the reservoir. The gas has a vapor pressure less than ambient atmospheric pressure at 37° C., more particularly less than 14.7 psia at 37° C.
The gas is preferably a non-ozone depleting, non-toxic gas.
In a preferred embodiment, the propellant is a gas selected from the group consisting of cyclopentane and dimethylbutane.
In accordance with another aspect of the present invention, there is provided a medication infusion pump adapted to be passively refilled with a medication. The medication infusion pump includes a reservoir that contains a gas having a vapor pressure less than ambient atmospheric pressure at 37° C., more particularly less than 14.7 psia at 37° C.
In accordance with another aspect of the present invention, there is provided a method of supplying a medication to a patient from an infusion pump as described herein. The method includes the steps of filling said reservoir with a propellant having a vapor pressure less than ambient atmospheric pressure at 37° C., drawing the medication into the medication chamber by exertion of the predetermined negative pressure on the medication, and dispensing the medication from the medication chamber via a pumping mechanism.
Other objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed description. It is to be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration and not limitation. Many changes and modifications within the scope of the present invention may be made without departing from the spirit thereof, and the invention includes all such modifications.


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Hawley, Gessner Goodrich, “Hawley's Condensed Chemical Dictionary: Thirteenth edition,” John Wiley & Sons, Inc. (see attached pages), 1997.

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