US3509883A - Expanding cannula - Google Patents

Description

y 5, 1970 N. R. DIBELIUS 3,509,883

EXPANDING CANNULA Filed NOV. 29, 1967 23 3/ Id 19 24 I7 Fig. 2.

/n vemor Norman 1?. Mb e/ius His Attorney- United States Patent Office 3,509,883 Patented May 5, 1970 3,509,883 EXPANDING CANNULA Norman R. Dibelius, Ballston Spa, N.Y., assignor to genfiral Electric Company, a corporation of New Filed Nov. 29, 1967, Ser. No. 686,630 Int. Cl. A61m 25/00 U.S. Cl. 128348 1 Claim ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION In order to divert the flow of blood from a patients body to an exterior treatment device, such as an artificial heart-lung machine and back, entry into and reliable connection to the patients cardiovascular system must be made. The cannula, or catheter, normally used to affect such a connection has a rigid, fixed wall dimension small enough to permit insertion into the particular blood vessel to which connection is being made. Thereafter, a tie is made to insure a close fit of the blood vessel to the outer surface of the wall of the cannula. As a result, this connection introduces a restriction to blood flow leaving the body and introduces significant turbulence in the flow, which results in damage to a significant number of the red blood cells traversing this connection.

Elimination of or reduction in the severity of such restricted regions would be a major step in reducing blood damage due to cannulation and the instant invention fulfills this need.

SUMMARY OF THE INVENTION The improved cannula of this invention consists of a fine wire double helix molded with a flexible material, such as rubber or silicone rubber, to form the wall of a thin leak-tight cylindrical tube. This much of the cannula construction bears a similarity to an amusement device known as the Chinese Finger Cuff in which double helixes of wire are woven into a fabric in the shape of a tube. By grasping the ends of the fabric and pulling thereon, the woven helixes are caused to move relative to one another (the angles between the wires change) and the diameter of the tube is decreased. Conversely, when the ends of the tube are moved toward each other and wires move in the opposite direction relative to one another and the diameter of the cull is increased. In the instant invention the device is leak-tight and means are provided for controlled lengthening or shortening of the cannula in order that the diameter of the cannula can be controlled.

Attachment of the cannula to the patients cardiovacuum system is accomplished by cutting at a slight bias across the blood vessel to a point about two-thirds of the way through the blood vessel, lengthening the cannula until the outer diameter thereof has been made small enough to insert into the blood vessel, inserting the cannula into the blood vessel, then shortening the cannula so inserted to the extent that the diameter thereof will be increasd until it exerts sufiicient radial force against the inner surface of the blood vessel to stretch the flexible wall of the blood vessel. This stretching action provides both a tight seal between the cannula and the inner surface of the blood vessel and an enlargement of the flow crosssection of the cannula to an extent in some cases, approximating the open area of the blood vessel.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages of the invention will appear more clearly from an examination of the following detailed description of the preferred embodiment thereof made with reference to the drawing in which:

FIG. 1 is a projection view partially in section showing the disposition of the fine Wire helixes and the attachment of the length modifying means thereto;

FIG. 2 is a longitudinal section through the tube wall in the vicinity of the attachment of the length adjusting means to the flexible wall construction, and

FIG. 3 is a partially cut-away sectional view taken on line 3-3 of FIG. 2 presenting additional details of the positive expansion-contraction control mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, the expanding cannula 10 comprises a generally leak-tight cylindrical wall 11 of flexible material, such as rubber or silicone rubber, ranging in nominal inside diameter from about A of an inch to about l-inch and capable of being increased in diameter by an amount ranging from about 25 percent to about 50 percent of the nominal diameter. Thus, the A inch diameter cannula would have to be expandable to about A inch or inch diameter, while the 1-inch diameter cannula might possibly have to be increased in diameter to only about 1 /8 inches.

The mechanism contributing the facility of cannula 10 for expansion and contraction is the double helical arrangement of fine wires 12 and 13. Each wire 12 extends the full length of the cannula 10 b ing disposed in a helical path within wall portion 11. Similarly, each wire 13 proceeds in a helical path extending the full length of cannula 10 in the opposite direction to the direction of wires 12. The relationship between wires 12 and 13 at th various intersections is that they are woven or braided together and pass in sequence over and under the wires encountered in the path of travel. The embedment of the double helix in a flexible wall material permits angular adjustment of wires 12 and 13 relative to each other about each point of intersection 13, while maintaining a leak-proof wall section. Thus, a change in the longitudinal dimension of the double helix is reflected by a change in angle a, which has substantially the same angular value between any two similarly disposed wires 12, 13. Although points of intersection, such as 14, 14' and 14" will move closer to or away from each other during such change in longitudinal dimension of cannula 10, the points of intersection themselves (as reflecting the intersection of wires 12, 13) remain substantially unchanged.

This change in longitudinal dimension may be readily accomplished by the application of force to the double helix system. One device 16 for controllably applying a shortening or lengthening force is shown in FIGS. 1, 2 and 3 and comprises an outer knurled threaded coupling 17 having inner threaded portions 18, 19 threaded in opposite directions, engaged with threaded portions 21, 22 on the boss-engaging members 23, 24, respectively. Segmented bosses 26, 27 are enlargements formed integral with Wall 11 and each segment may contain wire reinforcement (not shown). The segmented configuration of boss 26 is shown in FIG. 3, the configuration of boss 27 being similar with the segments being circumferentially aligned. In assembling the diameter control device the boss-engaging members 23 and 24 are first threadably engaged with coupling 17 as shown in FIG. 2, but separate from wall 11. At this point in the assembly plates 28, 29 are not yet engaged. Dogs 31 (of boss-engaging member 23) and dogs 32 (of boss-engaging member 24) are aligned axially of the assembly. As is shown in FIG. 3 one end of tube 11 is connected to a conduit 11a, the distal (free) end of tube 11 is then inserted through the preassernbly (17, 23 and 24) and the pre-assembly is moved up tube 11. Dogs 32 are lined up with slots 33 (the spaces between adjacent segments of boss 26) and, at the same time, dogs 31 are also lined up for axial movement through slots 34. The pre-assembly can now be advanced until dogs 32 and 31 are located between bosses 27 and 26. By rotating the pre-assembly the relative positioning of dogs 31 relative to the several segments of boss 26 (and, at the same time, of dogs 32 relative to the several segments of boss 27) shown in FIG. 3 is attained. Then all that remains is to attach annular plates 28 and 29 by means of screws 36, 37 and the assembly is complete.

Connection of the distal end of expandable cannula 10 into a given blood vessel (not shown) is accomplished by making an incision into the blood vessel at a slight bias from the plane perpendicular to the direction of the blood vessel with the incision extending more than half through, but less than all the way through the blood vessel, rotating coupling 17 to lengthen the cannula wall 11 and reduce the diameter thereof sufliciently to permit insertion of the distal end thereof into the blood vessel through the incision. The insertion having been made, the coupling 17 is once more actuated, this time in the opposite direction, whereby the length of the cannula wall 11 is shortened and its diameter is increased.

This increase in wall diameter is continued until the expanding cannula exerts suflicient radial force against the inside of the blood vessel to stretch the somewhat flexible wall of the blood vessel. This action produces an increase in the flow cross-section of the juncture sufficient to substantially or completely compensate for the presence of wall 11 within the blood vessel and, at the same time to form a tight seal therewith. This larger flow cross-s ction, which would not be possible with a rigid cannula, results in a reduction in damage to the red blood cells as the blood passes from the blood vessel to the cannula (and in returning through the cannula to the blood vessel) by eliminating the local high turbulence region otherwise encountered in the transit of blood from the blood vessel into a solid cannula.

In a typical construction of the expanding cannula 10 the wires 12, 13 would be about 10 mils in diameter and the range of diameters of the double helixes would range from slightly under inch to slightly under l-inch. The

convenient manner in which a reliable leak-proof connection may be made between the cannula and a surrouding flesh wall make this invention useful for the interchange of fluids other than blood, as Well, with other body cavities.

It will be understood that while the invention has been described specifically with reference to a particular embodiment thereof, various changes and modifications, as for example, in the actuating means for changing the length of the expandable cannula, wire sizes, the particular flexible matereial employed or the particular cavity to which the cannula is connected or the particular fluid transport d, may be made within the full and intended scope of the claim which follows.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a non-porous tube for insertion of the distal end thereof into a body cavity for the conduct of fluid through said tube to or from said body cavity, the improvement. in combination with said tube comprising,

(a) the distal end of said tube being flexible for a substantial length thereof,

(b) a double helix of fine wire embedded in the flexible length,

(c) a pair of outwardly directed spaced bosses formed integral with said flexible length,

(d) a pair of threaded members, each engaged with one of said bosses and (e) a member threadably interconnecting said pair of threaded members whereby due to the flexibility of said flexible length the distance between said bosses and, thereby, the pitch of the helixes may be controllably varied.

References Cited UNITED STATES PATENTS 2,711,331 6/1955 Temple 285-236 X 2,935,068 5/ 1960 Donaldson 128-348 3,154,079 10/ 1964 McKay 128348 3,416,531 12/1968 Edwards 128--348 FOREIGN PATENTS 107,272 5/ 1939 Australia. 627,278 8/ 1949 Great Britain.

DALTON L. TRULUCK, Primary Examiner US. Cl. X.R.

Images