Disposable cassette for connection to a liquid drug infusion pum

Details Disposable cassette for connection to a liquid drug infusion pum Disposable cassette for connection to a liquid drug infusion pum

1998-03-18

2000-08-22

Coggins, Wynn Wood

Surgery

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

Treating material introduced into or removed from body...

604247, A61M 100, A61M 500

Patent

active

06106498&

DESCRIPTION:

BRIEF SUMMARY
SUMMARY OF THE INVENTION

This invention relates to a disposable cassette for use with a liquid drug infusion pump according to the preamble of claim 1.
There is significant need for infusion devices to deliver therapeutic medicaments to patients. There has been and continues to be several important trends in the field of infusion therapy. Among these are the need for greater safety as the therapies and drugs evolve, the combination of ever more therapeutic capabilities into one infusion device, the desire to lower operation costs the inclusion of ever more functional features into the devices, and the increasing use of ambulatory and home therapy methods.
The prior art devices exhibit a number of weaknesses and lack a number of features, all of which contribute to being less than optimal devices for their intended purpose.
For example, some devices exhibit an unsafe failure mode called free flow. In this situation, the drug reservoir is above the patient and, due to this reservoir elevation, the drug flows uncontrolled into the patient resulting in an overdose. The usual causes of this condition are pumping mechanism failures or, more often, inadvertent removal of the cassette from the pump. Measures used in previous devices to minimize this problem are warning labels, alarms, and normally closed active valves (e.g. pinch valves) that are activated only by the pump.
In the past it has also been necessary to have a variety of different pumps, each with different therapeutic capabilities. This brings with it higher costs, more extensive personnel training, logistics problems, and the like. One major reason for this is the extremely wide range of infusion rates necessary to accomplish all the common therapies. Such a wide range is difficult to obtain in a single device without compromising one or the other therapies for such factors as accuracy, continuity of flow, battery life (if battery operated), and so on.
Most modern infusion pumps are capable of detecting an occlusion of the patient's IV line. Typically, these are pressure detectors with a preselected trip point which cause an alarm. These function adequately to detect an occlusion down line from the pump. The detection of an occlusion up line of the infusion pump is more difficult to accomplish and is done in the prior art by use of a drip chamber and drop sensor, both of which add cost and inconvenience to the devices. Further, such drop sensors are wholly unsuitable for ambulatory use.
A number of techniques are employed to sense pressure in the infusion line and are well known in the art. Nevertheless, existing systems compromise performance parameters such as reliability, accuracy, sensitivity, and repeatability against the production costs of the infusion pump and disposable cassette.
Many infusion pump cassettes and most ambulatory infusion pump cassettes have a flexible tube which is squeezed by the pumping mechanism to effect a peristaltic or displacement pumping action. These tubes must have special characteristics to be suitable for this use, which characteristics then make them difficult to reliably bond to the other cassette components. Such difficulties result in either increased assembly costs, leaking bond joints, or both. Further, the infusion rate accuracy is related to the accuracy of the internal diameter. Because these tubes are fabricated by extrusion, which is relatively inaccurate, production costs increase due to inspection and culling procedures.
Passive check valves are known in the prior art, including those that have a positive forward crack pressure, examples of which are disclosed in U.S. Pat. No. 4,856,340 to Garrison, U.S. Pat. No. 4,646,781 to McIntyre, et al., and U.S. Pat. No. 4,535,820 to Raines, et al. If constructed to have the correct range for forward crack pressure, they can be used to prevent free flow due to reservoir/patient elevation differences. Nevertheless, prior art valves often require costly inspection and culling procedures due to part and assembly process variability. For example, the housings of s

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