1. Field of the Invention
This invention relates to collapsible medical bags having a generally parabolic shape for the containment of diagnostic media and parenteral drug formulations and delivery thereof in a uniform, steady manner without retaining liquid droplets on their inside walls.
2. Reported Developments
Prior to the discovery and development of polymeric materials, parenteral liquids have been supplied to hospitals exclusively in glass bottles. The disadvantages of glass bottles, such as cost, shipping, storage and disposal, prompted the prior art to provide flexible, sterilizable containers in the forms of bags and bottles for the containment and delivery of parenteral solutions, such as diagnostic contrast media, nutritional and drug formulations. Such containers typically comprise: a flexible plastic sheet formed into a pouch, bag or bottle shape filled with a solution inside therein in a sterile environment; and one or more ports to fill and/or access the solution. Flexible tubing is also provided one end of which is connectable to a port on the container, and the other end connectable to a syringe or catheter pre-inserted into the site of delivery on the patient. Control means are also usually included with the tubing, such as valves and clamps for initiating, controlling and terminating the flow of the liquid to the delivery site. The container, tubing and control means are sterile packaged ready for use.
One of the requirements to be satisfied in flexible containers for delivering parenteral solutions to patients is that by their construction and design they deliver their total contents in a uniform, steady manner and without retaining liquid drops on their walls. By meeting such requirement the medical practitioner can determine the amount of parenteral solution delivered from the container to the patient. The prior art has addressed this requirement, as shown for example in U.S. Pat. No. 4,892,537, which discloses a bag having substantially parallel major sides or edges and converging minor sides which meet at a point forming an obtuse angle of at least 110.degree.. The converging edges are designed to guide the filled bag contents in a substantially unobstructed manner in a funnel-like fashion to an exit port.
U.S. Pat. No. 4,088,166 also addresses the problem of incomplete and non-uniform collapse of parenteral solution containers. The incomplete collapse is attributed to the stiffness of the thin-walled polypropylene container which tends to resist collapse to such a degree that the moderate suction pressure exerted on the container by weight of the parenteral solution is insufficient to cause its complete collapse. The non-uniform collapse, on the other hand, is attributed to the observed facts that on some occasions, the bags collapse along the long axis of their cross section, while on other occasions they tend to collapse along both the short axis of the cross-section as well as the long axis. As a result, the medical practitioners cannot determine exactly how much parenteral solution has been delivered out from the container. In order to solve the problem of incomplete and non-uniform delivery, the patentee incorporates gusset portions in the body portion of the container adjacent the shoulder portion. The gusset portions include lines of flexing weakness to facilitate the collapse of the container adjacent the shoulder portion as the contents thereof are withdrawn. The gussets said to facilitate both the lateral and longitudinal collapse of the container as it is emptied.
Medical practitioners have also observed fluid "hold up", i.e., when drops of parenteral solutions tend to remain on the internal walls of the flexible container as the solution is being delivered to the site of administration. The moderate suction pressure exerted on the walls of the container is insufficient to overcome the force existing between the drops of liquid and the walls of the container. Often, as the container is being drained, the emptied portion of the parallel walls adhere to each other further trapping drops of the liquid. As a consequence, the prescribed amount of parenteral solution is not delivered to the patient. Such delivery, especially in traumatic circumstances where a precise amount of a drug must be delivered into the patient, can make the difference between life and death of the patient.
The present invention addresses the problems associated with the lack of complete delivery of content, caused by incomplete and non-uniform collapse of the container during administration of the parenteral solution resulting in hold up of droplets of the solution on the walls of the container.