The prior art is generally cognizant of methods for inserting catheters of varying degrees of flexibility into blood vessels or other enclosed parts of the body. Stanley, U.S. Pat. No. 3,714,945, describes a device for inserting a semi-rigid catheter. In the Stanley device, a hollow needle or other rigid, piercing member is placed within a semi-rigid catheter prior to its insertion into the patient's body. The needle guides and supports the catheter while it creates the opening through which the catheter is passed. Once the needle with accompanying catheter has been properly placed in the blood vessel or other cavity, the needle is withdrawn, leaving the catheter behind and ready for use.
Smith, U.S. Pat. No. 3,826,256 and Smith, U.S. Pat. No. 3,703,174, show means for injecting a small, limp, and elastic catheter into a blood vessel or similarly enclosed part of the body. In both Smith devices a catheter having the characteristics described is wound in a small coil contained within the barrel of a syringe or similar fluid-tight holder that is filled with a suitable sterile fluid. The end of the catheter that is to be injected into the patient extends into the hollow interior of the needle of the syringe. Once the needle has been inserted into the blood vessel or other body cavity, the plunger of the syringe is depressed and a portion of the sterile fluid is injected into the patient through the needle. The friction between the fluid passing through the needle and the catheter contained therein is sufficient to flush the end of the cathether through the needle and into the blood vessel. As the end of the catheter is injected, it draws with it the trailing parts of the catheter, which uncoil and pass through the hollow needle. The trailing end of the catheter is provided with an enlargement of a size sufficient to prevent the entire catheter's being injected into the patient. The needle may be withdrawn from the patient, leaving the injected portions of the limp catheter in place.
For various reasons set forth in full in Smith, U.S. Pat. No. 3,703,174, a limp, flexible catheter is especially advantageous for use in situations in which a catheter must be left in place over an extended period of time. However, more rigid catheters of the sort described in Stanley may be adequate or even preferable when, for example, shortterm use is anticipated or a large diameter catheter is desired. Similarly, it may be desired to replace a large bore needle or a trocar already in place with a flexible and less trauma-producing catheter. For example, one way to determine the proper positioning of the end of a probing needle is to withdraw some of the fluid into which it extends to verify penetration to a particular cavity characterized by that fluid. The prior art, including the Smith patents referred to above, does not show a method or device for first withdrawing fluid through a needle and then, subsequently, inserting a limp and flexible catheter into the cavity penetrated by the needle with subsequent withdrawal of the needle in such a manner as to leave the catheter in place.