Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1998-11-16
2001-03-27
Seidel, Richard K. (Department: 3762)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C604S132000, C604S247000, C604S407000
Reexamination Certificate
active
06206850
ABSTRACT:
The present invention relates to a flow regulating means that forms a portion of the patient controllable drug delivery system. The present invention also relates to a patient controllable drug delivery system and in particular relates to a system which allows for continuous infusion of a drug, while also allowing for separately controlled (by patient, physician or nursing staff) intermittent surges of the same drug. The system is particularly useful in the administration of analgesics.
BACKGROUND OF THE INVENTION
It has been recognised for some time that patient controlled drug administration is desirable in many situations of chronic or temporary (such as post operative) pain. Before the advent of patient controlled analgesia, analgesia relied on periodic injections of drugs by a physician or nurse, typically at four hour intervals. This has the disadvantage that for long periods the patient's analgesic level is significantly above or below the optimum level.
Patient controlled analgesia improves on that prior art by enabling the infusion of small quantities of analgesics at regular intervals as perceived to be required by the patient. That prior art has also further developed to include apparatus and devices which allow for the continuous infusion of analgesics, with or without the need for patient control.
One form of such a device is described in the applicant's published international patent application WO 93/00944. In that publication, there is described an apparatus for patient controlled infusion of a drug, the apparatus allowing for intermittent administration of an analgesic or the like, the intermittency of the administration being controlled by the use of a small bore tube in the controlled refilling of a metering device, such that the patient may not administer further doses too rapidly after previous doses.
However, this system does not provide for the apparatus to be also used to continuously infuse analgesics or the like. The apparatus also would not prevent a patient from administering a dose earlier than recommended, albeit a dose of smaller volume than a full dose.
Another problem with prior art patient controllable drug delivery systems relates to the actuation of the metering device that delivers the drug. In general, metering devices in prior art systems must be actuated for prolonged periods to deliver the drug to the patient via relatively narrow conduits or tubing. In this respect, the prior art metering devices must be actuated for a sufficient time to deliver the drug to the patient against the pressure produced by the narrow conduits or tubing. The prolonged actuating periods of the prior art metering devices prevents their use by certain patients who are weakened or otherwise unable to actuate the metering device for a sufficient length of time Furthermore, when the prior art systems are controlled by nursing staff or the like they are required to remain with the patient for as long as it takes to actuate the metering device.
The system of the present invention aims to provide for separately controlled intermittent surges of a drug, such as an analgesic. Preferred forms of the present invention aim to provide for the continuous infusion of the drug as well as for separately controlled intermittent surges of the same drug. The system also aims to provide for the control of the intermittent surges so as to ensure the necessary time delay between surges, particularly where the system is patient controlled, as opposed to being controlled by a physician or by nursing staff. Finally, the present invention also aims to provide a separately controllable (by patient, physician or nursing staff) system with a relatively short actuation time.
SUMMARY OF THE INVENTION
Thus, the present invention provides a patient controllable drug delivery system capable of delivering a drug to a patient via a patient line, the system including: (i) a main reservoir for holding the drug; (ii) a metering device comprising an intermittent dose reservoir and a plunger biased towards a retracted position; (iii) a fill-line located between the main reservoir and the intermittent dose reservoir which allows continuous fluid communication between the main reservoir and the intermittent dose reservoir via a metering device fill-point; and (iv) a flow regulating means located in-line between the metering device and the patient line, wherein the flow regulating means comprises:
(a) a pressure set one-way valve; and
(b) a means for receiving and dispensing a dose of drug, said
means having an inlet means and an outlet means through which a drug may pass;
characterised in that the one-way valve is located prior to the inlet, the valve is closed when the flow regulating means is dispensing a drug and open when receiving a drug.
Preferably, the flow regulating means comprises a deformable reservoir. The remainder of the description in respect of the flow regulating means itself will be limited to this preferred form.
The deformable reservoir may be a length of elastomeric tubing or an elastomeric balloon member. In this configuration, the dispensation of the drug via the outlet is achieved by the pressure applied by the deformable reservoir and is at least partially dependent on the amount of deformation of the reservoir and the rate at which the reservoir returns to its pre-deformed state.
The flow regulating means may further comprise a housing which preferably acts as a limiting means for restricting the deformation of the deformable reservoir. Preferably. the housing at least partially surrounds the deformable reservoir. In one particular form, the housing is transparent and is capable of being dismantled to allow the deformable reservoir to be serviced or replaced as required.
Alternatively, the flow regulating means may comprise a cylinder, such as a syringe, having a piston therein for moving the drug in the cylinder to an outlet at one end of the cylinder; the piston and cylinder being relatively movable under the action of a spring which may be disposed internally or externally of the cylinder. In this configuration, the dispensation of the drug is preferably achieved by a syringe with a sprung plunger which exerts a predetermined pressure on the drug.
The pressure set one way valve may be any type of suitable valve that will only open when a predetermined pressure has been met. Preferably, the valve is provided proximal to the inlet of the deformable reservoir. In one particular form, the valve is provided integrally with the inlet of the deformable reservoir. It will be appreciated that the valve controls the passage of the drug to the deformable reservoir and is preferably adapted to allow a surge of drug to the deformable reservoir.
As indicated above the flow regulating means of the present invention is adapted for use in patient controllable drug delivery system. Whilst this specification makes repeated reference to “patient controllable” it will be appreciated that the drug delivery systems of the present invention may be operated by persons other than the patient such as medical staff or the like.
After actuation of the metering device by a patient, physician or nursing staff, so as to empty the intermittent dose reservoir and cause a surge of drug to the patient, the biasing of the plunger towards its retracted position causes a vacuum to be formed therewithin, the vacuum assisting in drawing drug via the fill-line from the main reservoir. By predetermining the strength of the bias on the plunger of the metering device, together with the amount of force being applied to the main reservoir to force drug therefrom, and more importantly by predetermining the diameter of the bore of the fill-line (which may itself be an inline flow resistor of the type mentioned above), the speed with which the intermittent dose reservoir is refilled may be controlled. With this in mind, and due to the pressure-set one way valve only being openable once the intermittent dose reservoir is completely refilled, the speed with which the metering device refills will determine the frequ
Merchant & Gould P.C.
O'Neil Christine
Seidel Richard K.
Thissell Jeremy T
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