Apparatus for advancing oversized catheter through cannula, and the like

#This invention relates to a new and improved catheter, and more specifically to a catheter which occupies a larger cross sectional area than the cannula through which it fits. This enables the catheter to be inserted through a cannula having a smaller cross section than the catheter itself and into a vein orifice of smaller size than the catheter.

#The problem which occurs when using a conventional catheter and cannula arrangement is the possibility that because the cannula has a larger diameter than the catheter, it will obviously create a larger perforation in the vein than the catheter; consequently, the catheter may slip out of the oversized perforation. Another problem associated with catheters is the fact that veins tend to be elliptical in cross section, however, catheters are manufactured with a circular configuration. Hence, even if a somewhat undersized catheter does not present a problem, where a catheter and vein have mismatched shapes, a potentially loose fit is possible. A loose fit may result in intravenous leakage or in the catheter simply slipping out from a vein, even when seemingly adequately secured.

#According to the invention, there is provided an assembly of a cannula, needle or the like and a folded catheter, the cross sectional area of the catheter being greater than the interior cross sectional area of the cannula. Following penetration of a vein by the cannula, the catheter is inserted into the vein in a folded condition. The resiliency of the catheter material, which is usually a rubber, elastomer, or similar material enables the fold to expand, and the catheter then assumes its normal shape in the vein. After the catheter has been inserted into the vein, the cannula is retracted from the vein, removed from the patient, and then separated from the catheter. Since the puncture in the vein is smaller than the catheter diameter, the possibility of the catheter slipping from a vein is greatly reduced.

#FIG. 1 is a side elevation view showing one embodiment of a device attached to a cannula for producing a folded catheter, and a roller drive for advancing the catheter through the cannula;

#FIGS. 2(A) and 2(B) are cross sectional views in end elevation of an elliptical shaped catheter in an unfolded condition, and when folded for insertion into a cannula, needle or the like;

#FIG. 3 is a cross sectional view in side elevation showing another embodiment of a device for producing a folded catheter;

#A portion of the catheter advance apparatus 10 of this invention is shown in FIG. 1, and includes roller drives 11, 12 positioned on either side of a catheter 20 which it drives through a cannula 14. A suitable cannula is disclosed in my U.S. Pat. No. 4,100,393 and provides a cannula body 15 having a distal end 15a, leading edge 15b, and holder wings, one wing 16 being shown welded to the cannula body.

#As illustrated in FIGS. 1 and 5, one embodiment of the catheter folding device 25 provides compression arms, one arm 26 being shown. The compression arm 26 is slotted 27, 28 to engage the edges of the wing 16. The compression head 29 for folding the catheter is of a resilient sheet structure similar to that shown in FIG. 4., and is integral with the arms and extends rearwardly thereof.

#After leaving the cannula 14, the folded catheter tube 13 is advanced by the roller drives 11 and 12 through the cannula after the latter has been inserted into the vein of a patient. Following insertion of the catheter into the patient's vein, the catheter advance apparatus 10 and catheter folding device 25 are disengaged from the cannula 14; the cannula is then withdrawn from the patient and the holder wings are folded together. This causes the cannula to split longitudinally and be disengaged from the catheter.