Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1997-11-12
2001-06-19
Silbaugh, Jan H. (Department: 1732)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S272200, C156S294000, C156S296000, C264S248000, C029S450000, C029S451000
Reexamination Certificate
active
06248196
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the field of surgical devices, specifically cannulas.
Cannulas are hollow tube instruments used to deliver fluids to or remove fluids from blood vessels, ducts or other hollow organs of animals. While many sizes of cannulas are available commercially, microcannulas suitable for use in surgery on small animals are of limited design and utility. The smallest commercially available cannulas are generally flat tipped and are large enough to accommodate a 14 to 24 gauge needle in the lumen of the cannula, which needle is used as a trochar. Small cannulas are generally made of small bore polyethylene or PTFE tubing and usually require an incision to be made in the vessel being cannulated. They can be supplied with a hypodermic needle which is used to create an incision and to block the cannula to prevent fluid contained in the vessel of the hollow organ from draining until the cannula is in place in the vessel or other hollow organ.
As cannulas decrease in size, they become more flexible and easily bent, and therefore difficult to manipulate. The flexibility of small cannulas occurs because of the decreasing absolute wall thickness of the cannula as they get smaller in diameter, and concomitant loss of rigidity of the cannula wall.
Conventional cannulas are supplied with trochars that move freely in the lumen of the cannula since it is conventionally desirable to be able to quickly remove the trochar once a vessel is cannulated.
Conventional small cannulas appropriate for use in cannulation of small blood vessels in microsurgery are notoriously difficult to use. The smallest cannulas available frequently require many minutes of patient and skilled manipulation to prepare a micro-incision in a blood vessel and properly place the cannula in small blood vessels. Furthermore such small cannulas suitable for microsurgery are frequently supported by an outside surrounding heavy gauge needle or auxiliary tube and the microcannula is placed inside the supporting tube. One of the main disadvantages of this conventional arrangement of microcannula and surrounding-supporting tube is that the wound made by the larger supporting hollow tube is larger than that which would be required if the microcannula were more robust. Large incisions weaken the vessel wall and damage the vessel.
It would be useful to provide a cannula suitable for microcannulation of small blood vessels in animals such as mice with sufficient rigidity to be easily manipulated and which does not require a vessel incision larger than the microcannula.
SUMMARY OF THE INVENTION
The present invention features a microcannula having a very small bore tube with a beveled tip and a sharp pointed trochar tightly but removably placed in the lumen of the small bore tube. This microcannula has sufficient rigidity to be relatively easily manipulated. Furthermore by means of using a sharp pointed trochar and bevel tipped tube, it is possible to cannulate a small blood vessel without the necessity of incising the blood vessel wall before inserting the cannula and trochar. The microcannula of the invention is also provided with a segment having an expanded outer diameter distal to the beveled tip of the microcannula useful for securing the cannula in a blood vessel or other hollow anatomical structure, as is described herein below.
It is an object of the invention to provide an easily manipulated microcannula which can be used to cannulate small hollow organs and blood vessels in a short period of time with a minimum of blood loss.
It is yet another object of the invention to provide a microcannula and trochar that can be used to cannulate a blood vessel without making a preparatory incision before inserting the trochar and cannula into the blood vessel.
It is still another object of the invention to provide a microcannula that can be easily secured in the cannulated blood vessel or other hollow anatomical structure.
In one embodiment of the microcannula of the invention, the microcannula is adapted to use with fluid supply systems such as syringes and pumps by being welded at the end distal to the tip to a tube having a larger diameter than that of the microcannula. The microcannula tube and the larger tube are welded together such that an area of reduced inside diameter at the weld site is produced at a site distal to the tip. The area of reduced diameter provides friction contact with the solid trochar such that the trochar is immobilized during insertion of the microcannula unit into a blood vessel.
In one aspect, the invention provides a process of producing a microcannula having an area of reduced inside diameter distal to the tip and which is adapted for use with supply systems such as syringes and pumps.
These and other objects, advantages such as ease of manipulation, and features such as an outside diameter of about 0.016 inch of the present invention will become apparent to those persons skilled in the art upon reading the details of the microcannula and process of producing the microcannula as more fully set forth below.
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Cohen Bruce
Segall Paul E.
Sternberg Hal
Waitz Harold D.
BioTime, Inc.
Bozicevic, Field & Francis
Field Brent E.
Silbaugh Jan H.
Staicovici Stefan
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