Sheath remover

A hollow, open-ended sheath is removed from a position enclosing a catheter which has been inserted through the sheath with a close tolerance and introduced into a human body thereby. A cutting blade is mounted in a deforming and guiding mechanism connected to the blade and engageable with the sheath for exerting pressure on the sheath in such a manner as to deform the sheath away from the catheter at a point immediately adjacent to the cutting blade and into contact with the cutting blade while maintaining the catheter beyond the reach of the blade. The device guides the blade for lengthwise movement relative to the sheath. The blade cuts the sheath in a lengthwise direction for removal from the catheter while the catheter remains in place.

BACKGROUND OF THE INVENTION 
This invention relates to the removal of sheaths from catheters and, more 
particularly, to a novel and highly-effective method and apparatus for 
removing a hollow, open-ended sheath from a position enclosing at least a 
portion of a catheter which has been inserted through the sheath with a 
close tolerance and introduced into a human body thereby. 
The technique of percutaneously entering the human vascular system with a 
thin walled flexible sheath was first described by Desilets and Hoffman in 
1965. The sheath is hollow and open at both ends and placed into the blood 
vessel with the aid of a relatively stiff introducer which is initially 
housed within the sheath and which is removed after the sheath has been 
inserted. The sheath then acts as a passageway for the insertion of many 
types of catheters into the vascular system. This includes the placement 
of intra-aortic balloons, for example, of the types as described in U.S. 
patent to Hanson and Wolvek U.S. Pat. No. 4,327,709. 
The percutaneous introduction of catheters via introducer sheaths has 
become an established practice in angiography. Angiography catheters in 
the neighborhood of 4 to 7 French (0.053"-0.092" in diameter) are 
routinely introduced through introducer sheaths. The advent of the 
percutaneous intra-aortic balloon has increased dramatically the use of 
introducer sheaths, as well as their size. These sheaths now accommodate 
balloon catheters ranging from 8.5 French to 12.5 French (0.112"-0.164" in 
diameter). 
When the introducer sheath is permitted to remain within the artery, 
surrounding the treatment catheter, the total diameter of the device 
within the blood vessel is increased by twice the wall thickness of the 
sheath plus twice the required catheter clearance. In practice, the 
presence of the introducer sheath may add up to 0.050" to the diameter of 
the catheter. 
Since many treatment catheters such as intra-aortic balloon catheters or 
ECG pacing lead catheters have enlarged hubs or electronic connections at 
their proximal ends, the sheath cannot be removed simply by pulling it 
back along and beyond the catheter and discarding it. In these cases the 
sheath must actually be cut away or split away from the enclosed catheter. 
This is generally done by using a scalpel or scissors to cut the sheath 
away from the catheter. However, the risk of damaging the catheter is 
always present in such a procedure. The problem being recognized, several 
attempts have been made to develop a sheath that can be peeled away from 
the catheter. 
The Desilets-Hoffman "Peel Away" introducer sheath has a split proximal end 
which terminates in two soft flexible "handles." The length of the sheath 
is scored to encourage splitting away of the sheath simply by pulling the 
two handles in opposite directions. Another split sheath is the 
Littleford/Spector introducer (U.S. Pat. No. 4,166,469). This introducer 
sheath has a T-shaped handle which is reduced in thickness at its 
centerline, thereby allowing the T-shape to be split by manual pressure. A 
small punched hole in the sheath material immediately below the splittable 
portion of the "T" handle, shallow longitudinal groove in the sheath 
material, perforations, holes, through cuts and reduced wall thicknesses 
have been described to encourage the longitudinal tearing of the sheath. 
Other peelable catheter introducer sheaths have been disclosed which are 
scored so as to be splittable and which comprise a slidable sleeve to 
prevent the splitting until the sleeve is slid down the catheter by the 
physician. These are described by King et al in U.S. Pat. No. 4,412,832 
and Boarini et al in U.S. Pat. No. 4,411,654. In both patents no hub 
assembly is present to form a portion of the introducer sheath. 
All of these attempts to solve the problem deny the physician the use of a 
conventional introducer sheath having a hub containing a female luer at 
its proximal end. The female luer is present in all non-splittable, 
conventional introducers and serves multiple important functions. Among 
these functions is the ability to lock the introducer dilator within the 
introducer sheath during the actual insertion, by means of their 
respective luer tapers. After removal of the introducer dilator, the 
female luer of the introducer sheath can be used for the attachment of a 
three-way stopcock and syringe for such purposes as blood sampling, the 
injection of radiographic contrast material, or merely to close the 
introducer off from the atmosphere. The female luer hub also serves as a 
"handle" to support the introducer sheath while inserting the catheter 
within it and helps to control bleeding during the insertion of the 
catheter. 
In addition, the splittable sheaths described above have the potential of 
splitting accidentally, either because of the internal pressure generated 
by the passage of a tightly fitting catheter or because of the accidental 
separation of the splittable handles by the physician. Accidental 
premature splitting of the sheath while in an artery could result in loss 
of blood because of the high blood pressures and flows in the arterial 
system. 
SUMMARY OF THE INVENTION 
An object of the present invention is to remedy the problems outlined above 
and, in particular, to permit the physician to use a conventional 
introducer sheath which may be inserted and used in a conventional manner 
with no danger of accidental splitting, while reserving to the physician 
the option to split the sheath for removal from the catheter, should he 
desire to do so, with no danger of puncturing or otherwise damaging the 
contained catheter. 
The foregoing and other objects are attained in accordance with the 
invention by providing an attachable and detachable apparatus which can be 
used when desired for removing a hollow, open-ended sheath from a position 
enclosing at least a portion of a catheter which has been inserted through 
the sheath with a close tolerance and introduced into a human body 
thereby. The apparatus comprises a cutting device and a deforming and 
guiding device, to which the cutting device is connected, and engageable 
with the sheath for exerting pressure on the sheath in such a manner as to 
deform the sheath away from the catheter at a point immediately adjacent 
to the cutting device and into contact with the cutting device while 
maintaining the catheter beyond the reach of the cutting device and for 
guiding the cutting device for lengthwise movement relative to the sheath. 
As the deforming and guiding means are moved lengthwise along the sheath, 
the cutting device thus cuts the sheath in a lengthwise direction for 
removal from the catheter while the catheter remains in place.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1-3 show a preferred embodiment of the sheath removing apparatus 10 
constructed in accordance with the invention. The apparatus 10 is adapted 
to remove a conventional, hollow, open-ended sheath 12 from a position 
enclosing at least a portion of a catheter 14 which has been inserted 
through the sheath 12 with a close tolerance and introduced into a human 
body 16 thereby (see the diagrammatic illustration in FIGS. 5 and 6). A 
luer fitting 28 is shown attached to the proximal end of the sheath. 
Cutting means such as a blade 18 is mounted in the apparatus 10. The blade 
18 is adapted to split the sheath 12, such as by cutting, from a strip 20, 
in a manner described below, to enable removal of the sheath 12 from the 
catheter 14 as the apparatus is moved along the length of the sheath in a 
direction shown by the arrow in FIG. 1. 
The apparatus includes deforming and guiding means which in the embodiment 
of FIGS. 1-3 comprises a first or upper body portion 22 and a second or 
lower body portion 24 (see FIG. 3) with the blade 18 being mounted in the 
upper portion 22. The body portion can be of plastic on any other suitable 
material. 
The upper body portion 22 is formed with a groove, or bore 33, with a 
reduced diameter entrance boss 33a, for receiving the sheath 12 and the 
catheter 14 it encloses. The first and second body portions 22 and 24 are 
separable and the sheath is laid in the bore 33 when the two pieces are 
apart. As shown in FIG. 3, the two body portions are held together by a 
plastic hinge 50. A latch 40 formed on one, and a mating boss 42 formed on 
the other, of the body portions 22 and 24 provide a means for securing the 
two together. The engaged position of the two body pieces is shown in 
FIGS. 1-3. 
The second body portion has an interior wall 35 in the area where the 
sheath enters the apparatus and a flat 36 stepped below the wall 35, in 
the area beneath the blade 18. When the second body portion 24 is in 
engagement with the first body portion 22 and the sheath is laid in the 
bore 33, the boss 33a of the first portion 22 and the interior wall 35 of 
the second piece squeeze against and deform the sheath 12 in the area of 
the flat 36, the portion above the flat where the blade 18 is located 
being called a cutting zone 26, to separate it from the catheter to 
provide a free space of the blade to contact the sheath and a disengaged 
position. Further, as seen in FIG. 3, the interior side walls 31 of the 
first body portion 22 engage the sheath and squeeze it in a horizontal 
direction, making it somewhat elliptical in shape. As seen in FIG. 3, a 
bubble is formed in the sheath below the blade 18 in the cutting zone so 
that it can cut the sheath without touching the catheter. 
The cutting blade 18 is preferably mounted in the first body portion 22 in 
the area where the sheath is most separated from the catheter. An epoxy 
cement 18' may be provided for securing the blade 18 therein (FIG. 3). 
Alternatively, the blade may be secured by heat staking, by potting with 
an appropriate cement, or by any other suitable means. 
The apparatus 10 is separated into its two parts, placed around the sheath 
12 adjacent the luer 28 and then the two parts are fastened together. The 
blade 18 cuts a strip 20 from the sheath 12 as the apparatus 10 is 
advanced in a distal direction (from the physician towards the patient). 
The strip 20 is ejected through an exit channel 46 formed in the rear of 
the first body portion 22. The exit channel 46 discharges the strip 20 in 
a direction substantially parallel to the lengthwise relative movement of 
the apparatus 10 with respect to the sheath 12 (FIG. 1). 
In practicing the method of the invention, pressure is exerted on the 
sheath 12 at at least one pressure point in such a manner as to deform the 
sheath away from the catheter 14 in a given deformation, or cutting, zone 
such as 26 (FIG. 1 and 2). As seen in FIG. 2, the interior wall portion 34 
of the first body portion 22 aids in accomplishing this by squeezing the 
sheath into a generally elliptical shape after it has been pushed upwardly 
by the step 30. Relative movement of the apparatus along the sheath 12 
continually changes the location of the pressure point, deformation zone 
and blade 18 in a direction lengthwise of the sheath 12. In this way, the 
strip 20 is cut from the sheath and the sheath is removable in two 
separate pieces from the catheter, as shown in FIGS. 5 and 6. 
The blade 18 thus cuts the sheath 12 in a lengthwise direction from a 
proximal location 20' (FIG. 7) to the most distal portion 12' thereof. In 
this way, the sheath 12 is removed from the catheter 14 while the catheter 
14 remains in place (see FIGS. 5 and 6). A knife or scissors may be used 
to separate the sheath 12 at or near the beginning 20' of the cut which 
forms the strip 20, thereby leaving the hub 28 residing on the catheter 
14. 
As FIG. 7 shows, there is normally only a very small clearance 29 between 
the catheter 14 and sheath 12. Typically the clearance may be about 0.01'. 
By deforming the sheath 12 in accordance with the invention, the normal 
clearance is increased in the zone 26 so that the blade 18 can cut the 
sheath 12 with no risk of cutting or otherwise damaging the catheter 14. 
As seen from FIGS. 1-3, the upper and lower body portions 22, 24 enclose 
the blade 18, thereby maintaining the hands of the physician or other 
operator or user of the apparatus beyond the reach of the blade 18. 
The blade 18 has a cutting edge 18a (FIG. 2) which intersects the sheath 12 
along two generally parallel lines 32, thereby cutting the sheath into two 
lengthwise portions, namely the strip 20 and the remainder of the sheath 
12 (FIG. 1), which are separately removable from the catheter 14. As 
described below, other types of cuts can be made. 
FIG. 4 shows another embodiment in which the entire groove 33 is formed 
with a keyway type bore 33 in the upper body portion 22. The sheath and 
catheter are placed into the apparatus by laying them into the bore 33 and 
then engaging the two pieces. The bore 33 has a neck 33a for retaining the 
introducer sheath 12 in the groove 32 when the body portions 22 and 24 are 
in the disengaged position as shown in FIG. 4. The embodiment of FIG. 4, 
has snap ribs 36 formed on one, and mating snap grooves 38 formed in the 
other, of the body portions 22 and 24 to fasten the two pieces together. A 
length of plastic tubing 48 is connected to each of the two pieces to keep 
them attached to each other. 
The second body portion 24 has a pressure rib 42 (FIG. 4) formed with a 
pressure plate 44 which bears against and deforms the sheath 12 when the 
body portions 22 and 24 are in the engaged position. The pressure rib 42 
is of reduced height in the cutting zone below the blade 18 to reduce the 
friction inherent in the lengthwise movement of the device 10 with respect 
to the sheath 12. If desired, the interior wall of the upper piece also 
can be formed with the side walls 34 to exert pressure to squeeze the 
sheath into the elliptical shape. 
In the embodiment of FIG. 4, an angled exit channel 46 is formed in the top 
body portion 22 to discharge the strip 20 in a direction forming an upward 
angle away from the catheter, but parallel with such lengthwise relative 
movement. 
In the embodiment of FIG. 8, the body portion 22 includes at least one 
movable portion 52. The movable portion is manually engageable by the user 
who presses it inwardly to cause it to bear against and deform the sheath 
12. A hinge 54 connects the movable portion 52 to the remainder of the 
body portion 22. 
In the embodiment of FIGS. 9 and 10, the body portion 22 comprises a pair 
of movable portions in the form of buttons 56 slidably arranged in bores 
58 respectively on opposite sides of the sheath. Each of the buttons is 
manually engageable and movable inwardly of the body whereby they are 
caused to bear against opposite sides of the sheath and deform it upwardly 
toward the blade 18 to better define the free space between the catheter 
and the sheath. 
Relative movement between the apparatus 10 and the sheath 12 is effected by 
traction exerted on the sheath or strip 20. The physician exerts such 
traction by steadying the apparatus 10 with one hand and pulling on the 
strip 20 or on the other severed portion of the sheath 12, as illustrated 
in FIG. 6. The sheath 12 is removed without having to pass over enlarged 
portions of the sheath or catheter which are located proximally with 
respect to the sheath 12 and which are represented schematically at 28 and 
61 in FIG. 5. 
FIG. 11 shows another embodiment of the invention. Here, the blade 18a is 
configured as a V-shaped plow to extend down vertically and forwardly to 
engage and cut the sheath in the zone 26 where it is deformed away from 
the catheter. In this embodiment, a single slit is made. A blade 
arrangement also can be used with two or more vertically downwardly 
extending blades so that two or more cuts can be made at the same time. 
Thus, there is provided in accordance with the invention a novel and 
highly-effective method and apparatus for removing a sheath from a 
position enclosing a catheter which has been inserted through the sheath 
with a close tolerance and introduced into a human body thereby. In 
accordance with the invention, there is no possibility of accidental 
cutting of the catheter, since the device in accordance with the invention 
is constructed so that the catheter remains beyond the reach of the blade. 
Similarly, since the blade is totally enclosed, the hands of the physician 
operating the device are also beyond the reach of the blade. 
Many modifications of the preferred embodiments of the invention disclosed 
above will readily occur to those skilled in the art. For example, the 
materials of which the apparatus 10 is constructed, the orientation of the 
blade 18 and its spacing from the sheath 12 before the latter is deformed 
by the apparatus 10, the details of the retaining means for retaining the 
body portions in the engaged position and of the connecting means for 
connecting the body portions in the disengaged position can all be varied, 
as those in the art will readily understand. Accordingly, the invention is 
to be construed as including all apparatus and methods which fall within 
the scope of the appended claims.