Patent Application
20150320926
Not Applicable.
Not Applicable.
The present invention relates in general to a perfusion cannula for insertion into the cardiovascular system, and, more specifically, to a vented cap retained on a proximal end of a cannula that is easily removed for connection into a perfusion circuit after priming.
During cardiac bypass surgery, a patient's blood is redirected through an extracorporeal perfusion circuit typically including various items such as a venous cannula, PVC tubing, a reservoir, a pump, an oxygenator, an arterial filter, and a return cannula. The most common type of return cannula is the arterial (e.g., aortic) cannula with a tapered plastic tip at the distal end for insertion through an incision in the aorta.
A connector or adapter at the proximal end is initially covered by a sealed cap to prevent significant blood loss once the tip is inserted into the aorta. Vent holes in the cap (and/or a manually-controlled luer lock vent adjacent the cap) may be provided to remove air from the cannula as it initially fills with blood (known as priming). After priming, the cap is removed by the surgeon, and then the connector/adapter is connected to tubing that provides oxygenated blood from the pump/oxygenator.
The proximal connector of the arterial cannula may be comprised of a barbed fitting. A typical cap is made of a flexible elastomer in the shape of a cylinder which is closed at one end and has an internal sealing ring that engages a barb on the cannula connector. A tear strip and tear tab are formed on the cap to facilitate removal of the cap when desired. The conventional tear strip is defined by seams or grooves extending from the open end and up a portion of the side of the cap. By pulling the tear tab, the tear strip splits partly away from the cap on one side so that a lower portion of the cap no longer grips the cannula.
In a conventional cap, the tear seams or grooves may extend across the internal sealing ring. Even when they extend that far, however, the resiliency of the upper portion of the cap tends to continue to hold it in place on the cannula because the sealing function of the cap dictates a sufficiently snug fit to avoid leakage prior to tearing of the cap. Thus, removal of prior art caps has required a second step in which the surgeon grasps the cap to pull the remaining portion off of the cannula. It would be desirable to provide for a one-step removal of the cap by merely pulling on the tear tab, while maintaining robust sealing characteristics before initiating removal of the cap.
In one aspect of the invention, a removable cap is provided for a cardiovascular cannula. The cap has a sleeve section with an inner surface adapted to receive a connector end of the cannula. The cap has a top section closing a closed end of the sleeve section and extending substantially perpendicular to the sleeve section. The cap has a pull tab extending radially from an open end of the sleeve section and having first and second edges. A pair of tear seams are sunk into the sleeve section and the top section defining a tear strip in the cap. The tear seams include a sleeve portion extending substantially in parallel and substantially axially from the first and second edges of the pull tab to the top section. The tear seams have a top portion continuous with the sleeve portion and partially circumscribing the top section. The sleeve section includes a segmented snap ring protruding radially inward on the inner surface of the sleeve section except at a pair of gaps coinciding with the pair of tear seams. The top section includes a seal cylinder projecting concentrically from the top section to seal against an inside surface of the cannula connector end.
Referring now to
A top section 26 of cap 20 includes a plurality of small apertures 27 for venting air. Thus, when the distal tip is inserted into the cardiovascular system (e.g., into the aorta), blood enters the cannula lumen and flows toward connector end 21. As blood enters the cannula, air exits through apertures 27. Apertures 27 may taper to an exit diameter of about 0.004 inches so that they are large enough to vent air but are sufficiently small that little if any blood can leak through them once the lumen is fully primed.
When the surgeon is ready to attach other tubing to the primed cannula, the cap must be first be removed. Removal is achieved as shown in
Embodiments of the present invention shown in
The perspective view of
A pull tab 47 extends radially from open end 44 of cap 40 and has first and second edges 48 and 49 that align with tear seams 42 and 43. Pull tab 47 preferably includes a grasping pad 50 that widens out from edges 48 and 49 to provide a size appropriate for grasping between the thumb and index finger of the user. A plurality of dimples 51 on the surface of pad 50 help establish a firm grasp for pulling tear strip 41 away from sleeve section 45. Since tear seams 42 and 43 extend all the way between the ends of sleeve section 45 and into top section 46, it is not necessary to peel the remaining portion of the sleeve section off of the cannula connector end.
As shown in
As shown in the bottom view of
As a result of the segmentation of snap ring 55, a possibility of leakage of liquid past the snap ring may be increased. To compensate for such possibility, the present invention further adds a sealing cylinder 60 that projects concentrically from top section 46 as shown in
Cap 40 is preferably formed as a single integrated unit. It is preferably comprised of polyethylene, which can be shaped using injection molding. The tear seams preferably have a U-shaped profile instead of the conventional V-shape, which results in a smoother tearing with a better controlled tearing force.
