Large-diameter expandable sheath and method

A large-diameter expandable sheath for use in introducing a catheter into a vessel in the body of a patient comprising an elongate sheath tube formed of a flexible material which has proximal and distal extremities and a passage extending therethrough of a maximum predetermined diameter. The distal extremity of the elongate sheath tube is folded longitudinally to a smaller folded diameter. A backflow adapter is secured to the proximal extremity of the elongate sheath tube. The backflow adapter has a central opening therein in registration with the passage in the sheath tube. A valve is disposed in the central opening of the backflow adapter and is movable between open and closed positions. The valve when open permits the catheter to be inserted into the sheath, and when closed serves to form a hemostatic seal about the catheter.

BACKGROUND OF THE INVENTION 
This invention relates to an expandable sheath and more particularly to a 
large-diameter expandable sheath and method. 
Expandable access catheter assemblies have heretofore been provided to 
facilitate the placement and removal of diagnostic and therapeutic 
catheters through the vascular system. Such catheter assemblies included a 
flexible variable-diameter catheter body, a diameter control stylet and a 
flexible Y-hub. The flexible Y-hub incorporates an adjustable hemostasis 
valve and a side port in one branch and a diameter control stylet guide 
wire in another branch. A flexible variable diameter catheter body is 
secured to the flexible Y-hub and can be expanded between a collapsed 
position and an expanded position by the stylet guide wire. Several 
deficiencies have been found in such a device. For example, the adjustable 
hemostasis valve is incapable of accepting large catheters. The flexible 
variable-diameter catheter body is objectionable in that it has a tendency 
to reduce in diameter and hold onto large-diameter catheters when it is 
attempted to place the same through the catheter body. In addition, the 
tip of the stylet guide wire catches a large-diameter catheter which 
causes elongation of the catheter body and reduction in its diameter to 
grab and prevent further advancement of the large-diameter catheter. There 
is therefore a need for a new and improved large-diameter expandable 
sheath which will overcome these deficiencies. 
SUMMARY OF THE INVENTION 
In general, it is an object of the present invention to provide an 
expandable sheath which can be utilized with large-diameter catheters and 
method for using the same. 
Another object of the invention is to provide a sheath of the above 
character which is folded longitudinally to a small diameter and which can 
be expanded greatly when a large-diameter catheter is to be passed through 
it. 
Another object of the invention is to provide a sheath of the above 
character which is provided with a backflow adapter which includes a 
tubular diaphragm that can be moved into an hourglass or iris-like 
configuration to create a fluid-tight barrier around any tubular device 
such as a large-diameter catheter passed through the backflow adapter and 
the tubular diaphragm. 
Another object of the invention is to provide a sheath of the above 
character in which a dilator can be utilized for expanding the sheath. 
Another object of the invention is to provide a sheath of the above 
character in which the backflow adaptor can be readily controlled.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In general, the large-diameter expandable sheath is used for introduction 
of a catheter into the body of a patient. It comprises an elongate sheath 
tube formed of a flexible material and having proximal and distal 
extremities and having passage therein of a predetermined maximum 
diameter. The distal extremity of the elongate sheath tube is folded 
longitudinally into a smaller diameter. A backflow adapter is secured to 
the proximal extremity of the elongate sheath tube. The backflow adapter 
has a central opening therein in registration with the passage in the 
sheath tube. Valve means is disposed in the central opening in the 
backflow adapter and is movable between open and closed positions. The 
valve means when in an open position permits a catheter to be introduced 
into the sheath and when closed forms a liquid-tight seal about the 
catheter extending therethrough. 
More particularly as shown in FIG. 1 of the drawings, the large-diameter 
expandable sheath 11 consists of an elongate sheath tube 12 having 
proximal and distal extremities 13 and 14 and having a flow passage 16 
having a maximum diameter extending therethrough. The expandable sheath 11 
can have a suitable length as, for example, 15-35 centimeters and 
preferably approximately 18 centimeters with a maximum outside diameter of 
1 centimeter. The elongate sheath tube is formed of a flexible material 
having a wall thickness of 0.001 to 0.020 inches and preferably about 
0.005 inches and can be formed of a suitable plastic material such as 
Teflon.TM. (a fluorinated ethylene polypropylene). An alternate material 
is Tefzel.TM. (ethylene tetrafluoroethylene). The selected material should 
have physical characteristics which will not be compromised by radiation 
sterilization. 
The distal extremity of the sheath tube, as shown in FIG. 4, is pleated or 
folded longitudinally to provide wraps or folds 17 for a distance of 
approximately 10 centimeters from the distal end to provide a distal 
extremity of reduced diameter as, for example, a reduction of the outside 
diameter from 3/8" to 3/16" or approximately one-half the original size. 
The folding or pleating of the sheath tube 12 in this manner serves two 
purposes. The first purpose is to reduce the sheath diameter to facilitate 
introduction of the sheath and to make it less traumatic for the vessel 
into which it is introduced. The second reason is that with a 
small-diameter, thin-wall tube, as represented by the elongate sheath tube 
12, there is less likelihood of kinking occurring than in a 
large-diameter, thin-wall tube. The distal extremity of the sheath tube 
12, when folded longitudinally in this manner, serves to provide kink 
resistance in the distal extremity 14 while still being relatively 
flexible. 
If it is desired to further decrease the likelihood of kinking in the 
large-diameter, thin-wall tube which forms the sheath tube 12, another 
embodiment of the sheath tube can be provided of the type shown in FIGS. 
5, 6 and 7. The sheath tube 18 shown in those figures is provided with a 
plurality of circumferentially spaced apart flexible elongate elements 19 
which are embedded in the wall of the tube 18 and extend longitudinally 
along the length thereof as shown in FIG. 5. The proximal extremities are 
offset or staggered as shown in FIG. 5 with alternate elements 19 being 
shorter. This offset relationship provides a gradation in stiffness in the 
proximal extremity of the sheath tube 18. The elongate elements 19 can be 
in the form of stainless steel wires having a diameter ranging from 0.005" 
to 0.015" and preferably a diameter of approximately 0.010". As can be 
seen from FIG. 6, the sheath tube 18 can bulge outwardly around the 
elongate elements 19 while being relatively thin between the elongate 
elements to retain the flexibility of the tube 18. As also can be seen 
from FIG. 6, the elongate elements 19 are spaced apart in the three groups 
to facilitate the formation of six folds 20 as shown in FIG. 7. Thus, by 
way of example, each set of elongate elements can have the elongate 
elements spaced approximately 35.degree. apart with each set being spaced 
approximately 85.degree. apart. Spacing of the elongate elements 19 in 
this manner facilitates the formation of the folds shown in FIG. 7. The 
elongate elements 19 also provide additional rigidity longitudinally of 
the tube 18 so as to inhibit accordioning of the tube 18 during removal of 
the introducer as hereinafter described. 
A backflow adapter 21 is secured to the proximal extremity of the elongate 
sheath tube 12. The backflow adapter 21 consists of a housing or body 22 
which is formed of a suitable material, such as plastic. The housing 22 is 
provided with a central bore 23 extending therethrough in axial alignment 
with the passage 16 of the sheath tube 12. A cylindrical sheath tube 
adapter 26 is disposed in the bore 23 and is provided with an annular 
recess 27 which receives an inwardly-extending flange 28 provided on the 
proximal extremity 13 of the sheath tube 12 (see FIG. 8). A tubular insert 
29 formed of the same material as the sheath tube 12 but of a greater wall 
thickness, as for example twice the wall thickness of the sheath tube 12, 
is secured within an annular recess 30 in the sheath tube adapter 26 by 
suitable means such as an adhesive. The insert 29 serves as a 
reinforcement and serves to prevent collapse of the proximal extremities 
13 of the sheath tube 12 when the expandable sheath 11 is used. The sheath 
tube adapter 26 is fixed within a first cylindrical collar 31 seated 
within the bore 23 and is held in place by solvent bonding the cylindrical 
collar 31 into the housing or body 22 to prevent longitudinal and/or 
rotational movement of the first collar 31 relative to the housing or body 
22. A second collar 34 is also seated in the bore 23 and is rotatable 
therein. An annular ring gear 36 having teeth 37 thereon is also rotatably 
mounted in the bore 23 as hereinafter described. 
A cylindrical or tubular valve member or diaphragm 40 is disposed between 
the first and second collars 31 and 34, and is provided with a bore or 
flow passage 41 extending therethrough. The valve member 40 is provided 
with inwardly extending annular lips or flanges 42 and 43 provided on 
opposite extremities of the same (see FIGS. 8 and 14). The flange 43 is 
seated in an annular recess 46 in the sheath tube adapter 26 and is 
retained therein by the first collar 31. The flange 42 is seated in an 
annular recess 47 provided in a retaining ring 48 and retained therein by 
the second collar 34. An annular protrusion 49 is formed integral with the 
retaining ring 48 and engages one side of the toothed ring gear 36 which 
is secured to the retaining ring 48 by suitable means such as an adhesive. 
Similarly, the retaining ring 48 functionally engages the second collar 34 
and causes the second collar 34 to rotate therewith. 
The diaphragm or valve member 40 can have a suitable size as, for example, 
a length of 0.30-0.45" inches, and preferably a length of approximately 
0.30" inches, and an inside diameter of 0.35-0.500", and preferably an 
inside diameter of 0.375", with a wall thickness ranging from 0.005" to 
0.015", and preferably a wall thickness of 0.007". The annular lips 42 and 
43 can extend inwardly for a distance of 0.032" from the outer wall 
surface and have a length of approximately 0.050". The diaphragm or valve 
member 40 can be formed of a suitable material, such as a silicone 
elastomer, as, for example, Dow Silastic 97-4720. It can have a Shore A 
hardness ranging from 20-80 and preferably a Shore hardness of 40A. 
Alternatively, a low durometer, tear-resistant rubber-like latex material 
can be utilized. 
Other diaphragm or valve members such as shown in FIGS. 15 and 16 can be 
utilized which have the same physical conformation. In the embodiment 
shown in FIG. 15, small diener polyester fibers 52 are bonded to the 
exterior surface of the diaphragm 51 with a silicone adhesive so that the 
fibers 52 extend circumferentially around the outside surface of the 
diaphragm 51. Such fibers serve to impede radial and longitudinal 
distention of the diaphragm or valve member 51. The diaphragm or valve 
member 56 shown in FIG. 16 is provided with a cylindrical wall 57 which 
increases in thickness in a direction towards the distal extremity of the 
diaphragm. This helps the diaphragm to withstand the pressures applied to 
the diaphragm during use, which may cause the diaphragm to distend and 
leak. 
Means is provided for causing relative rotation between the sheath tube 
adapter 26 and the retaining ring 48 for opening and closing the bore or 
flow passage 41 by twisting of the cylindrical valve member or diaphragm 
40. This is accomplished by fixing the first collar 31 and the sheath tube 
adapter 26 within the housing or body 22 by suitable means such as solvent 
bonding and causing rotation of the retaining ring 48 by the use of a rack 
61. The rack 61 consists of a rod 62 formed of a suitable material such as 
stainless steel which extends through a hole 63 (see FIG. 11) in the 
housing or body 22 in a direction which is tangential of the bore 23. The 
rod 62 is disposed immediately adjacent a flange 64 formed in the body 22 
against which the ring gear 36 rotates. The hole 63 opens into the bore 23 
so that rack teeth 64 provided on the one side of the rod 62 engage the 
toothed ring gear 36 whereby upon reciprocatory movement of the rack 61, 
the ring gear 36 is rotated through an angle ranging from 180.degree. to 
360.degree., and preferably an angle of at least 270.degree.. 
An actuator 66 formed of a suitable material such as plastic is mounted on 
the upper extremity of the rod 62 and is secured thereto by suitable means 
such as an Allen-head screw 67 set into the rod 62, as shown in FIG. 13. 
The actuator 66 is generally rectangular in plan and is provided with an 
upstanding lip 68 so that it conforms to the conformation of the index 
finger of the hand which is to be utilized for actuating the rack 61. The 
actuator 66 is provided with a reinforcing rib 69 along one edge of the 
same. A similar actuator member 71 is provided on the body 22 underlying 
the actuator 66 and is also provided with a downwardly extending lip 72. 
The actuator member 71 is secured to the body 22 by suitable means such as 
an adhesive. The member 71 also has a rectangular configuration in plan 
and is sized so that it is adapted to be engaged by the thumb of the hand, 
as shown in FIG. 12. Thus, one hand can be utilized for operating the 
backflow adapter 21 by the index finger of the hand grasping the actuator 
66 and the thumb of the same hand grasping the member 71. 
A stabilization and guide rod 76 extends through a tangential bore 77 (see 
FIG. 11) provided in the body 22 which is spaced apart from the bore 63 
and extends in a direction which is parallel thereto. The rod 76 is formed 
of a material such as stainless steel and is provided with a collar 78 
which extends through the reinforcing rib 69 of the actuator 66 and is 
secured therein by suitable means such as an Allen-head screw 79. 
Means is provided for yieldably returning the rack 61 into a position so 
that the valve member or diaphragm 40 is in a normally closed position and 
consists of a coil spring 81 coaxially mounted on the rod 62 and having 
one end engaging the actuator 66 and having the other end engaging a seat 
82 provided in the body 22. Means is provided for preventing the spring 81 
from urging the rod 62 out of the bore 63 and consists of a lump 83 of 
solder or a braising material provided on the rod 62 adjacent the lower 
extremity of the rack teeth 64. Thus, it can be seen by the hand engaging 
the backflow adapter 21 using the index finger to engage the actuator 66 
and the thumb to engage the actuator member 71, the rack 61 can be 
reciprocated back and forth to open and close a bore 86 extending through 
the retaining ring 48 and the sheath tube adapter 26 by forming an 
hourglass or iris-like closure as shown in FIG. 9 in which the radially 
extending lines 87 shown represents the folding over of the elastomeric 
material of the valve member or diaphragm 40. The collar 78 provided on 
the stabilization rod 76 serves to stop further travel up the rack when 
the collar 78 engage a seat 88 provided in the body 22. In this position, 
the spring 81 is almost completely compressed as shown in FIG. 10. 
Following the release of the actuator 66, the spring 81 returns the rack 
62 to its home position and causes the valve member or diaphragm 40 to be 
completely closed as shown in FIG. 9. 
The ring gear 36 can be formed of a suitable material such as stainless 
steel and can have any suitable number of teeth. Alternatively, the ring 
gear can be formed of a suitable plastic such as Nylon.TM.. The other 
portions of the backflow adapter 21 as, for example, the body 22, the 
first collar 31, the second collar 34, the retaining ring 48 can be formed 
of a suitable plastic such as polycarbonate. The metal parts such as the 
rod 62, the stabilization rod 76 and the spring 81 can be formed of a 
suitable material such as stainless steel. 
Means is provided for introducing liquid as, for example, a radiopaque 
liquid, into the bore 86 and consists of a tube 91 formed of a suitable 
material such as plastic extending through the first collar 31 and through 
the sheath tube adapter 26 so that it is in communication with the bore 
86. Flexible tubing 92 is connected to the tube 91 and has a stopcock 93 
of a conventional type mounted thereon which is provided with a Luer-type 
fitting 94. The stopcock 93 is provided with a knob 96 which can be 
utilized for moving the stopcock 93 between open and closed positions. 
A sheath introducer 101 is provided as a part of the assembly shown in FIG. 
1 and as shown in FIG. 2 consists of an elongate tubular member 102 formed 
in three sections 103, 104 and 106 of different diameters. The elongate 
tubular member 102 can be formed of a suitable plastic material such as 
Pebax.TM. which is formed of polyether Block Amides which is loaded with 
approximately 10% barium sulfate to make the same visible under X-rays. 
Section 103 can have a diameter ranging from 0.15" to 0.30" and preferably 
an outside diameter of 3/16ths of an inch. The section 104 can have a 
suitable diameter as, for example, 0.08" to 0.15" and preferably a 
diameter of 1/8 of an inch. The section 106 can have a diameter ranging 
from 0.06" to 0.12" and preferably a diameter of 0.08". The distal 
extremities of the sections 103 and 104 are provided with tapers 107 and 
108, respectively, so as to provide a tapered transition from one diameter 
to another. A Luer-type fitting 111 is mounted on the proximal extremity 
of the tubular section 103. A bore or lumen 112 (see FIG. 4) of a suitable 
size as, for example, one capable of passing a 0.038" guidewire, is 
provided in the section 106 as well as in the sections 104 and 103 
extending the length of the tubular member 102. A tube 116 is mounted on 
the section 106 and the distal extremity of the same and is formed of a 
suitable material such as silicone and is retained thereon in a suitable 
matter by the use of polyethylene shrink tubing 117. A cylindrical 
enlargement or annular bump 121 is provided on the tubular section 106 
adjacent the distal extremity of the shrink tubing 117 and serves to 
prevent the sleeve 116 and the shrink tubing 117 from accidentally 
slipping off of the distal extremity of the tubular section 106. 
When the sheath introducer 101 is disposed in the expandable sheath 11, as 
shown in FIG. 1, the proximal extremity of the silicone sleeve 116 is 
disposed over the distal extremity of the sheath tube 12 and serves to 
prevent the sharp edges of the folded sheath tube 12 from causing trauma 
to the interior wall of a vessel when it is introduced into the vessel 
when the sheath is introduced as hereinafter described. A vent hole 123 is 
provided in the sheath introducer 101 which is in communication with the 
passage 112 proximal of the silicone sleeve 116, as shown in FIG. 3. The 
vent hole 123 can be utilized for flushing the elongate sheath tube 12 
through the side port fitting 94 prior to use of the expandable sheath in 
a surgical procedure. 
Operation and use of the expandable sheath 11 in conjunction with the 
sheath introducer 101 may now be briefly described as follows. Let it be 
assumed that the patient has been prepared in a conventional manner and 
that it is desired to enter a peripheral vessel such as an artery or a 
vein of the patient. The desired vessel is exposed and a longitudinal or 
transverse incision made into that vessel. A guidewire of a suitable size 
is then selected as, for example, a guidewire having a diameter of 0.038". 
The guidewire (not shown) is introduced into the vessel and then the 
expandable sheath assembly 11 shown in FIG. 1 is placed over the guidewire 
by placing the proximal extremity of the guidewire into the lumen 112 
provided in the elongate tubular member 102 and advanced through the Luer 
fitting 111. The rounded tip and the small diameter of the section 106 of 
the tubular member 102 facilitate advancement of the sheath introducer 101 
into the vessel without traumatizing the vessel. The small-diameter tip 
section 106 is followed by the elongate sheath tube 12 which has been 
collapsed as hereinbefore described about the tubular section 106 until 
the sheath tube 12 has been introduced to the proper depth in the vessel. 
As soon as the sheath tube 12 has been positioned in the vessel, the 
sheath introducer 101 is advanced relative to the elongate sheath tube 12 
by using one hand to hold the backflow adapter 21 which is connected to 
the sheath tube 12 and the other hand to push the sheath introducer 101 so 
that the proximal extremity of the silicone sleeve 116 moves off of the 
distal extremity of the sheath tube 12 to expose the same. 
As soon as this has been accomplished, the sheath introducer 101 is pushed 
forward so that section 103 enters the collapsed section of the sheath 
tube 12 to commence opening of the same. The sheath introducer 101 is then 
removed through the backflow adapter 21. The sheath introducer can be 
removed by grasping the backflow adapter 21 by the fingers of the hand as 
hereinafter described to at least partially open the same to permit 
removal of the sheath introducer and dilator 101 while minimizing the flow 
of blood from the sheath tube 12. The backflow adapter can then be 
released. The sheath 11 and its backflow adapter is now in its normally 
closed state to provide a hemostatic seal closing the flow passage 86. 
The physician conducting the procedure then selects the desired catheter or 
other device which is desired to be introduced through the expandable 
sheath 11. Such a device should have a diameter of 8.5 mm or less or which 
is at least slightly less than the diameter of the bore 86. The physician 
grasps the actuator members 66 and 71 and presses the same to operate the 
rack 61 to open the diaphragm or valve member 40 permitting the physician 
to insert the device as, for example, the catheter through the expandable 
sheath 11. As soon as the catheter has been advanced as far as desired, 
the physician releases the pressure on the actuator members 66 and 71 
permitting the diaphragm 40 to close around the device as, for example, 
the catheter inserted through to form a hemostatic seal about the 
catheter. If it is desired to reposition the catheter, it is merely 
necessary to push or pull the catheter and it will slide freely through 
the diaphragm. When it is desired to remove the catheter, the catheter 
need only be pulled out of the sheath 101 and the diaphragm will seal 
closed forming a hemostatic seal. 
After the procedure has been completed, the expandable sheath 11 can be 
removed from the vessel and the incision which has been made in the vessel 
for permitting passage of the expandable sheath can be sutured. 
It can be seen from the foregoing that there has been provided an 
expandable sheath 11 which can be made in various sizes to accommodate 
large-diameter devices while still providing the desired hemostatic seal. 
The expandable sheath can be readily inserted and removed. The sheath 
introducer 101 facilitates this introduction. It is provided with a distal 
extremity 106 which is small in diameter to permit the sheath tube 12 to 
be wrapped about the same as hereinbefore described. The sheath introducer 
101 is provided with sections 103 and 104 of larger diameters to provide 
additional rigidity to the sheath introducer 101 to facilitate pushing of 
the sheath introducer when introducing the expandable sheath 11 into the 
vessel of the patient. 
An alternative mechanism for actuating the diaphragm 40 is shown in FIG. 17 
and consists of a pinion 131 which engages the ring gear 36 and is 
disposed in a cylindrical recess 132 provided in the body 22. The pinion 
131 is mounted on a shaft 133. Another gear 134 is mounted on the shaft 
133 and has a smaller diameter than the diameter of the pinion 131 and 
engages the rack teeth 64 provided on the rod 62. By providing such a gear 
arrangement, it can be seen that it is possible to provide a shorter rack 
to achieve the same degree of ring gear rotation for opening and closing 
of the diaphragm 40. 
As can be seen in FIGS. 18 and 19, there is shown another embodiment of a 
mechanism for actuating the diaphragm 40. As shown therein it consists of 
a flexible rack 141 that is comprised of a flexible member 142 which is 
provided with rack teeth 143 on one side of the same which are adaptable 
to engage the ring gear 36. The member 142 extends through a semicircular 
slot 144 provided in the body so that it extends through the body and 
around the ring gear 36. An actuator 146 is provided formed integral with 
the rack 141 for operating the rack 141 with the fingers of the hand. In 
this construction the rack is substantially contained within the body 22.