Retention cannula or catheter and applicator
United States Patent 3890970

A self-retaining surgical cannula comprises a catheter formed as a tube of elastic material, semirigid in character, such as polyethylene, polyvinyl chloride or silicone rubber, etc., with a perforate membranous front end tough, firm and sharp enough to be inserted into body tissue without being itself cut or torn by an internal rigid injection stylet or needle. A thin membranous ballooning portion of the tube contracts or deflates on insertion into the tissue and expands on application of fluid pressure within the catheter tube to lock the cannula in place. A rigid stylet or hollow needle, somewhat dull at its front end, is provided over which the catheter is placed for insertion into the tissue. A limit stop fixed on the catheter prevents over-insertion. The application stylet, which is formed to allow fluid to flow along it into the catheter front end, is withdrawn after the catheter tube is in place, leaving the latter flexible enough to permit movement of the patient and allowing needed surgical procedure while it remains in place in the tissue.

Application Number:
Publication Date:
Filing Date:
Primary Class:
Other Classes:
International Classes:
A61M5/32; A61M25/04; (IPC1-7): A61M5/32
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US Patent References:
3630198CATHETER PLACEMENT DEVICE1971-12-28Henkin
3613684TROCAR CATHETERS1971-10-19Sheridan
3435826EMBOLECTOMY CATHETER1969-04-01Fogarty
2512569Hypodermic needle1950-06-20Saffir
1444714Medical appliance of suction type1923-02-06Teshima

Primary Examiner:
Gaudet, Richard A.
Assistant Examiner:
Mcgowan J. C.
Attorney, Agent or Firm:
Cahill, Sutton & Thomas
What is claimed is

1. A cannula for penetration into and retention within soft body tissue, for injecting treating fluid into said tissue, comprising:

2. The combination set forth in claim 1 wherein said catheter includes a stop member formed integrally therewith and comprises an annular ring positioned to limit the depth of penetration of said catheter.


There is a recognized need for a flexible cannula or catheter mechanism suitable for either intermittent or continuous injection of fluids, such as anaesthetics, into body tissues while surgical treatment is being given. In obstetrics practice, for example, it is often desired to provide paracervical anaesthesia over a prolonged period of time. It is obviously necessary that the applicator or cannula remain in place, while not unduly restricting movement of the patient or interfering with the necessary medical or surgical procedures. Thus, there is need for a cannula or catheter which can penetrate body tissue with minimal injury and supply periodically or over a sustained time period the necessary fluid anaesthetic, etc., while remaining securely in place and without requiring use of complicated fastening means.

Suggestions have been made in the prior art, as in U.S. Pat. No. 3,508,545 to Reif, et al, for a flexible self-securing catheter. The patentees have described a cannula in the form of a slender tube of silicone rubber which has at its forward end a small retaining barb. This device is inserted into the tissue to be treated by means of an outer tubular needle which surrounds the catheter and which itself is guided in an outer tube of rigid plastic construction. After the catheter is secured in the tissue, the inserting means are withdrawn. Thereafter, treating fluid is injected as needed through the slender flexible tube. The barb or retaining element in this case is necessarily soft, flexible and quite small. It may not be retained in soft tissues as well as is required for some cases.

Other references in the prior art have described expansible or inflatable securing means for retaining a catheter or silimar cannula in tissue or especially in a body cavity. Some of these are complex mechanical devices. Thus, U.S. Pat. No. 3,692,029 described spring-actuated mechanical wings which are pushed outwardly from the tubular body of a trocar or injection device for retaining that device inside of a body cavity. Other self-retaining catheters or trocars are suggested in U.S. Pat. Nos. 1,922,084; 2,230,150; 2,320,157, and 3,438,375. See also U.S. Pat Nos. 3,544,668; 3,606,889, and 3,734,100 for other devices having relevance in some respects to the present invention. Still other retention means are described in U.S. Pat. Nos. 3,713,447 and 3,039,468. The latter shows finger members or expandable membranes which, on application of pressure or other manipulating means, serve to spread or expand and hold the device in place against premature withdrawal or displacement.

Most of the devices mentioned in the prior art, in the above patents and in others, are subject to the objection that they are rigid, either causing considerable discomfort to the patient or requiring that the patient be restrained against movement or at least against certain kinds of movement. In many cases, also, they interfere with procedures or operations by the surgeon or physician.

Other devices for special application have been specially designed or shaped so as to be self-retaining, as in the case of an ear drum penetrating device, described in U.S. Pat. No. 3,645,268. Such devices are not suitable for the purposes of the present invention which are to make use of flexible cannular means which are reliably retained in the tissue being treated, as, for example, in the tissues commonly requiring anaesthetic treatment in childbirth and in analogous situations.

The use of flexible catheters or catheter tips is, of course, well known. Some of these have been applied or inserted in tissues by use of a more rigid guiding or inserting tool such as an interior stylet or an external tubular guide. In some cases the guiding means have been separate and withdrawable, as in the case of U.S. Pat. No. 3,508,545, mentioned above. However, most of the prior art devices do not meet the required criteria of the present invention, that is, they lack one or more of the features of being flexible, of being insertable into soft tissue directly, of being retained in that tissue reliably in spite of tissue softness and/or being designed to permit manipulation of that tissue or movements of the patient, voluntary or involuntary, while permitting intermittent or continuous medication, as by injection of anaesthetic fluids or the like. A further requirement, for the present case, is that the depth of insertion into tissue should be accurately controllable in each case. A further and important aspect of the present invention is the discovery that by proper design of the flexible catheter member, although of thin elastic membranous structure, it can be formed with a firm and sharp enough front end that it may be inserted into the tissue to be treated. Penetration is effected while the catheter is shrouded over a rigid stylet or hollow needle. Moreover, this can be done without tearing or cutting the cannula and without undue pain or injury to the patient. All rigid elements used for application of the catheter in the present invention, can be withdrawn and the catheter will remain securely in place until intentionally removed.

Other objects of the invention will be further illustrated and explained in connection with the detailed description which follows.


FIG. 1 shows a plan view of the cannula, which comprises a catheter and applicator means, with certain parts cut away or shown in section.

FIG. 2 shows an enlarged fragmentary sectional view of the front edge of a catheter and the inserting end of a rigid stylet, for a typical application.

FIG. 3 shows a similar enlarged fragmentary sectional view of the flexible catheter inserted in soft tissue and secured therein by an enlarged balloon section, the inserting stylet having been withdrawn.


Referring first to FIG. 1, the flexible catheter 11 itself is shown as being in the form of a hollow tube of firm but flexible sterile material, such as polyethylene, vinyl chloride, silastic, or silicone rubber. At its left or rear end this tube 11 is secured by a flange 13 in a nipple or coupling element 14 by means of which the catheter may be attached to the outlet 15 of a syringe 20. Towards its forward or left end, the catheter is provided with a fixed or integral stop member or limit device in the form of a ring 16. In front of the stop member 16, the tube body is reduced in thickness at 17 to form a normally expanded or expandable "balloon" member when the catheter is in place in tissue 40, FIG. 2. Stop member 16, of course, serves to limit the depth of penetration to which tube 11 can be inserted into tissue 40.

In its front end portion, the tube 11 is formed as a thin membrane at 21 with a sharp cutting edge 22; being made of very tough and strong film material, its body can be stretched over the dull point of a stylet or needle 25 without being cut or torn by the needle. The stylet 25 is blunt at its front end 29 but the tube 11 at its front end 21 is firm and sharp enough that the assembly can be inserted in tissue such as that involved in obstetrics without cutting or tearing the film. The front end part 21 is provided with perforations 23. Needle 25 may be hollow, if desired, in which case similar perforations 27 in its forward end allow injection of fluid through the front of the catheter from the syringe 20 or from any other soruce. If stylet 25 is not hollow, it is shaped or sized so that fluid from source 20 may flow along it into the front end of the catheter 11.

The stylet 25 is flanged at 28, at its rear or right end, FIG. 1; this flange fits within the coupling connection 14 to syringe 20; the syringe or fluid supply source may be of any suitable type, as will be obvious. When the catheter 11 is attached to the syringe 20 through outlet coupling 14, and the rigid stylet 25 is in place within the catheter as in FIG. 1, the thin but penetrating membrane part 21 being stretched over the end of the needle, the balloon part 17 may be normally expanded somewhat as shown in dotted lines in FIG. 1. However, this balloon part 17 smooths out as the needle or stylet carrying the outer membrane cover is forced into the tissue 40, as seen in FIG. 2. Outlets 23 in the membrane, and openings 27 in the stylet or needle, if the latter is hollow, permit the injection of anaesthetic fluid or other medication into the tissue from the syringe 20. This action of injecting fluid moreover, assists in expanding and holding the balloon section 17 in expanded tissue-locking position, as shown in FIG. 3. The membrane at 17 may expand somewhat, even without this internal pressure, as the stylet is withdrawn from the tube 11, tending also to lock the latter in place within the tissue 40.

An important aspect of the present invention is the discovery, mentioned above, that the thin membrane end of the catheter can be drawn over the stylet and retain sufficient sharpness to penetrate the tissue without undue difficulty and without tearing or cutting the thin membrane part 21, so that the catheter front end is neatly inserted into the tissue and locked there with minimum damage to the tissue. Experience has shown that the flexible catheter element, in the cannula, when made of a high grade, relatively firm synthetic rubber or stretchable plastic of sterile and sanitary type, can be inserted smoothly with the needle and is readily stripped off to remain securely in place when needle 25 is withdrawn. However, by applying some fluid pressure from the syringe as the needle or stylet is withdrawn from the tube 11, FIG. 3, the stripping of the tube 11 off the needle is further facilitated and the balloon part 17 is kept fully expanded. Thus, the device is locked firmly and reliably in place. To withdraw tube 11 from the tissue, stylet 25 is reinserted to deflate the balloon part; the dull point on the stylus prevents cutting the catheter. This permits the balloon 17 to collapse. Then, the whole device can be withdrawn from the tissue without injury to the latter.

The original syringe 20 is employed while continuing to supply treating fluid, or the tube 11 may be attached to another fluid source after the stylet has been withdrawn from the catheter, as in FIG. 3. If desired, the stylet may be made retractable without requiring that it be completely removed from tube 11, but wherever a stiff needle or stylet would cause discomfort to the patient or would restrict the patient's movements undesirably, or would interfere with proper medical or surgical procedures, it should be removed. This may be done by disconnecting the connection or coupling 14, removing the stylet from the catheter 11, and reconnecting the latter to the syringe or to some other source of treating fluid, thus repressuring the balloon part 17 to hold the catheter in place.

While reference has been made to treatment of cervical tissue or related tissue with anaesthetic fluids, it will be understood that the invention is suitable for treatment of other soft tissue with anaesthetics or with other treating agents, according to good medical practice and with appropriate skill. It will be obvious that various modifications can be made in the apparatus and in its application, without departing from the spirit and purpose of the invention. The particular materials employed for the various parts may be varied, in accordance with good practice in the medical instrument field. Thus, the tubes 11 will ordinarily be expendable, used only once, while the applicator means 25 and other mechanical parts may be of stainless steel or the like and sterilized and reused as often as needed. Obviously, any of the parts may be expendable or they may be made of materials suitable for sterilization and reuse.

It is intended by the claims which follow to cover the invention and its obvious variations and modifications as broadly as the state of the prior art properly permits.