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Description  |
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FIELD OF THE INVENTION
This invention relates to catheter systems for artificial insemination.
BACKGROUND OF THE INVENTION
A number of techniques are used to perform artificial insemination.
Typically, gametes or zygotes are introduced via a catheter into the
uterus or a fallopian tube. The medical community is not in complete
agreement as to the best location for placement of gametes or zygotes.
There is controversy whether uterine or fallopian tube placement is better
and, with respect to each, as to the precise location within the uterus or
fallopian tube.
One transcervical procedure described by R. Jansen in "Catheterisation of
the Fallopian Tubes from the Vagina", The Lancet, Aug. 8, 1987, page 309,
utilizes a catheterization system that is inserted through the vagina and
cervix, through the uterus and into the fallopian tube to place
reproductive cells in the fallopian tube. The system includes an
introducing catheter, an obturator, and a transfer catheter. The obturator
is used to straighten and stiffen the introducing catheter during
insertion. The introducing catheter, stiffened by the obturator, is
advanced into the vagina and through the cervix. The distal portion of the
introducing catheter is normally curved to assist positioning of the tip
at the entrance of the fallopian tube when the introducing catheter is
disposed in the uterus. After the distal portion of the introducing
catheter is within the uterus, the obturator is withdrawn and the
introducing catheter assumes its curved shape. It is manipulated to locate
the tip at the entrance to the fallopian tube.
Reproductive cells are loaded into the distal end of the transfer catheter,
and the transfer catheter then is passed through the introducing catheter
and is advanced into the fallopian tube to a desired position. The cells
then are expelled from the transfer catheter by flushing the catheter with
a liquid, such as a culture medium, e.g., Hams Solution. Preloading the
transfer catheter at its distal end avoids dilution of the reproductive
cells which would occur if the cells were delivered through the proximal
end of the transfer catheter using a large quantity of flushing fluid.
The foregoing procedure relies on the transfer catheter to force its way
through the fallopian tube until the desired position is reached. Much of
the fallopian tube normally is in a collapsed condition, however, and
manipulation of the loaded transfer catheter within the fallopian tube can
cause premature spillage of some of the reproductive cells before the
transfer catheter can be advanced fully to the desired position within the
fallopian tube. Also, the musculature of the fallopian tube can crush the
transfer catheter which may prevent its advance or cause additional
spillage of reproductive cells.
Another procedure, as disclosed in U.S. Pat. No. 4,832,681 (Lenck),
utilizes a surgical method of installing a catheter through the uterine
wall to implant an ovum or zygote in the uterine cavity. The catheter is
made of a flexible tube such as silicone elastomer reinforced with a
coiled wire. The distal end of the tubing is installed through the uterine
wall by advancing it through the vagina, making an incision in the upper
portion of the vagina, and advancing the tubing along the outside of the
uterus. An incision is made in the uterine wall and the distal end of the
tubing then is inserted through the uterine incision to communicate with
the uterine cavity. The tubing is relatively large (having an inner
diameter of between 2 and 2.5 mm and an outer diameter of between 4 and
4.5 mm) and is unsuitable for insertion within the fallopian tube. The
technique of installing the tubing involves the attendant risks and trauma
of surgery.
It would be desirable to provide an artificial insemination system usable
for both fallopian tube and uterine placement of reproductive cells.
Additionally, it would be desirable to provide such a system in which the
precise location where the reproductive cells are deposited can be
determined. Information as to the actual placement of reproductive cells
at varying depths and locations within the reproductive system of the
patient may be of importance in connection with subsequent placement of
reproductive cells in that patient. It is among the general objects of the
invention to provide such a system.
SUMMARY OF THE INVENTION
The present invention utilizes an access catheter having a single lumen
shaft and a reinforced, crush-proof segment at the distal end of the
shaft. The reinforcement resists constriction of the distal segment by the
fallopian tube. The access catheter is very flexible yet it is strong and
has a relatively thin wall and large lumen.
The distal segment of the catheter may be formed from inner and outer
tubular layers of material with a reinforcement sandwiched between the
layers. In one construction, the reinforcement comprises a helical coil
formed from rectangular cross section wire. The shaft may be formed by a
single extruded tube to which the distal segment is joined. The distal
segment has a smaller outer diameter than that of the shaft, preferably
less than 0.08 inch and most preferably less than 0.045 inch when it is
desired to advance the access catheter into the fallopian tube. It is also
preferable for the segment to have an inner diameter of at least 0.028
inch, and more preferably at least 0.030 inch. The small outer diameter
and thin wall of the distal segment results in a flexible yet strong
distal segment which is readily insertable into a fallopian tube.
It is desirable for the reinforcing material to be visible to monitoring
radiation such as ultrasound. The proximal end of the shaft of the access
catheter may include at least one visually perceptible marker for visual
alignment relative to the reproductive system or relative to an
introducing catheter in which the access catheter is insertable.
This invention further features a catheter system and method involving the
access catheter, an introducing catheter, and a transfer catheter. The
system may further include use of an obturator and a flexible guide for
assisting insertion of the introducing catheter and the access catheter,
respectively. One or more of the components may include visually
perceptible markers enabling alignment and relative measurement of the
position of the components with respect to themselves or with respect to
the patient's reproductive system.
It is among the objects of the invention to provide a novel access catheter
which may be used in combination with an introducing catheter and a
transfer catheter for delivering materials to a body cavity.
It is a further object of the invention to provide an access catheter
having a distal segment which can have both high flexibility and high hoop
strength to resist collapsing of the distal segment.
A still further object of the invention is to provide such an access
catheter which can have a very thin wall to provide a large inner diameter
and a relatively small outer diameter.
A still further object of the invention is to provide an improved catheter
system and method for accurately placing materials within a female
reproductive system.
A further object of the invention is to provide such a catheter system for
placing gametes or zygotes transcervically into the uterus or a fallopian
tube.
Yet another object of the invention is to provide methods of using such
catheters and of aligning markers on the components relative to each other
and relative to the reproductive system to accurately place the
reproductive material.
DESCRIPTION OF THE DRAWINGS
The foregoing and other objects and advantages of the invention will be
appreciated more fully from the following further description thereof with
reference to the accompanying drawings wherein:
FIG. 1 is a diagramatic illustration of an introducing catheter comprising
a portion of the catheter system according to the invention;
FIG. 2 is a diagramatic view of an obturator insertable within the
introducing catheter of FIG. 1;
FIG. 3 is a diagramatic view of an access catheter according to the
invention;
FIG. 4 is a diagramatic view of a transfer catheter insertable through the
access catheter;
FIG. 5 is a schematic view of a guide according to the invention for
assisting placement of the access catheter;
FIG. 6 is a schematic representation of a portion of a female reproductive
system;
FIG. 7 is an enlarged, fragmented, section illustration of a portion of the
distal segment of the access catheter of FIG. 3; and
FIG. 8 is an enlarged, partial, cross-sectional view of the junction of the
distal segment and the main shaft of the access catheter.
DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT
FIGS. 1-4 illustrate the elements of the catheter system of the present
invention including an introducer catheter 10 (FIG. 1), an obturator 30
(FIG. 2), an access catheter 40 (FIG. 3) and a transfer catheter 60 (FIG.
4). The catheter system may further include a guide 50 (FIG. 5). Each of
the foregoing elements may be considered as having a proximal end (to the
left in the drawings) and a distal end (to the right in the drawings), the
distal end being inserted into the patient and the proximal end remaining
outside of the patient and controllable by the physician. FIGS. 1-5 are
arranged to suggest schematically the relative lengths of the introducer
catheter 10, obturator 30, access catheter 40, transfer catheter 60, and
guide 50.
The foregoing system is intended for use in placing gametes or zygotes
selectively at a predetermined location in the fallopian tube or the
uterus nonsurgically and with vaginal access. FIG. 6 illustrates
diagramatically a portion of the human female reproductive system,
including a vagina V, a cervix C, a uterus U, a fallopian tube F, and an
ovary A. It is considered desirable by many in the medical community for
artificial insemination to simulate natural conception as closely as
possible. During natural conception, an egg is released from an ovary A
and travels into the fallopian tube F through finger like fimbria B. The
egg then travels down the fallopian tube, through narrowed isthmus I and
past entrance E into the uterus U. There is some uncertainty as to the
actual location at which sperm, traveling through the cervix C and into
the uterus U and into the fallopian tube F, unite with the egg. The
catheter system according to the invention enables accurate placement of
reproductive cells at a wide range of locations within the uterus U and
the fallopian tube F.
One of the difficulties of depositing reproductive cells in the fallopian
tube F is that the tube F normally is in a collapsed condition. The
catheter therefore must be forced through the collapsed fallopian tube F,
establishing a sufficient passage as it is advanced while minimizing
trauma to the fallopian tube F. Moreover, the most difficult portion of
the fallopian tube F to traverse is the narrow-diameter isthmus I beyond
the entrance E. Additionally, crushing of the catheter due to the
musculature of the fallopian tube must be successfully overcome.
Briefly, the catheter system of the present invention overcomes the
foregoing difficulties by an access catheter 40 having a reinforced distal
tip 44 which is readily insertable through the entrance E and the isthmus
I of a fallopian tube F. The catheter system may be provided as a kit
including the access catheter 40, the introducing catheter 10, and the
transfer catheter 60. Additionally, the system and kit may include an
obturator 30 and a guide 50.
In general, the catheter system is used as follows for accessing a
fallopian tube. The obturator 30 is inserted through the proximal end of
the introducing catheter 10 to stiffen it..sup.1 With the rigidity
provided by the obturator 30, the introducing catheter 10 is inserted into
the vagina V, through the opening 0 of the cervix C, and into the uterus
U. The obturator 30 is removed from the introducing catheter 10, and the
introducing catheter 10 resumes its curved shape to place the distal tip
14 at the entrance E to the fallopian tube F. The obturator 30 then is
withdrawn and the access catheter 40 is advanced through the introducing
catheter 10.
.sup.1 The distal 6 cm. of the obturator is malleable and can be formed by
hand to any curve desired by the doctor.
Advancement of the access catheter 40 may be assisted using guide 50 which
is inserted through the access catheter 40. The combination of the guide
50 and the access catheter 40 is more rigid (has greater column strength)
than the access catheter 40 by itself. Therefore, the pushability of the
access catheter 40 is enhanced by the guide 50 which is useful for
traversing the isthmus I of the fallopian tube F. Also, the flexible
spring tip 52 of the guide 50 can be inserted first through the entrance E
and isthmus I of the fallopian tube F, after which the access catheter 40
is advanced to "track" the path of the guide 50.
After the access catheter 40 is positioned within the fallopian tube F, the
guide 50 is withdrawn and the transfer catheter 60 is inserted through the
access catheter 40. Typically, the distal end 66 of the transfer catheter
60 is advanced approximately one cm beyond the distal end 49 of the access
catheter 40. A syringe then is mated with the luer 64 of the transfer
catheter 60, and the reproductive cells at the distal end of the transfer
catheter 60 are discharged at the desired location. Details of the
construction and use of the illustrative embodiment are as follows.
The introducing catheter 10, FIG. 1, is a single lumen catheter formed of
an inner Teflon lining, a wire reinforcing braid, an outer urethane
sleeve, and having an outer diameter of 0.104 inch (2.62 mm) and an inner
diameter of 0.072 inch (1.83 mm). In one manufacturing procedure, the
introducing catheter 10 is formed by placing a Teflon tube, having an
inner diameter of 0.072 inch and a wall thickness of 0.0025 inch, over a
mandrel having an outer diameter of approximately 0.070 inch. The Teflon
tube is mechanically roughened, and then heated to shrink it onto the
mandrel. The ends of the tube are sealed. The assembly then is placed in a
chemical bath such as Tetra-etch available from W. L. Gore & Associates,
Newark, N.J. to strip fluorine atoms from the polymer. The assembly is
removed from the bath, and oxygen and nitrogen in the air interacts with
the fluorine depleted carbon atoms to render the surface more compatible
to an adhesive which assists in securing the wire braid to the roughened,
chemically treated surface. Wire having a diameter of 0.003 inch then is
wrapped about the assembly to form the braid, and all but the distal three
to six cm of the assembly are coated with a thin layer of epoxy, such as
FDA #2 available from Tra-Com, Inc., Medford, Mass. to secure the braid in
place. The epoxy then is cured, and the ends of the braid are trimmed,
leaving approximately three to six cm of the distal tip without braid or
epoxy to provide increased flexibility. The assembly then is placed inside
a urethane tube having an inner diameter of 0.099 inch and a wall
thickness of 0.014 inch, and the urethane tube is heated and pulled to
shrink it onto the assembly. The original, straight mandrel is removed,
and a curve is established for the introducing catheter by placing it onto
a curved mandrel. The catheter is then baked to set the curve, after which
it is cooled and the mandrel removed. The luer 22 is attached, and bands
16 are placed on the outside of the shaft 12. The introducing catheter 10
is approximately 23.2 cm in usable length (i.e. length distal to the luer
fitting 22). It is desirable for the usable length to be at least 18 cm
for accessing a fallopian tube. This minimum length enables the distal tip
14 of the introducing catheter 10 to be placed close to the entrance E of
the fallopian tube F, without requiring the luer fitting 22 to be inserted
into the vagina V.
It is also desirable for the introducing catheter 10 to be provided with
visually perceptible ink bands 16 commencing with distal band 18
approximately six cm from the distal tip 14. One of the bands 16 is
aligned by a physician with the opening 0 of the cervix C to determine
easily the exact depth to which the distal tip 14 is inserted within the
uterus U. The bands 16 are approximately one mm in width and are spaced
one cm apart, culminating in proximal band 20. Permanent indelible ink is
placed directly in the exterior of the shaft 12 to form the bands. Their
use is described below in more detail.
Before insertion of the introducing catheter 10, a self-sealing device 23
such as a Tuohy-Borst type of adapter or a device such as the type
disclosed in U.S. Pat. No. 4,424,833 (Spector) is attached to the proximal
luer 22. The sealing device 23 enables an access catheter according to the
invention to be inserted through it and manipulated while maintaining a
seal to prevent the escape of liquids. Preferably, the seal is maintained
by a gasket which holds the access catheter in position after advancement
through the introducing catheter 10. The luer 22 and the sealing device 23
have a total length of approximately 7.2 cm.
The obturator 30, FIG. 2, consists of a malleable steel rod 32, shown in
dotted lines, approximately 0.030 inch in diameter and coated with
polypropylene 34. The polypropylene coating 34 adds to the volume occupied
by the rod 32 within the lumen of the introducing catheter 10 without
increasing the stiffness of the obturator 30. The obturator 30 has a
usable length of 30.3 cm, a total diameter of 0.065 inch, and assists
insertion of the introducing catheter 10 by stiffening it. .sup.1 A luer
fitting 36 serves as a handle and as a stop to limit insertion within the
introducing catheter 10.
.sup.1 This allows the doctor to form the end of the introducing catheter
into any desired curve to allow for anatomical variances.
An access catheter according to the invention is comprised of two sections,
a main shaft and a distal segment which can have both high flexibility and
high hoop strength to resist collapse. The access catheter 40, FIG. 3, is
formed of a main shaft 42 having an outer diameter of 0.057 inch (1.45
mm), and a length of 31.2 cm, and a reinforced distal segment 44 with an
0.042 inch (1.07 mm) outer diameter, and a length of approximately 8 to 9
cm. The outer diameter of the shaft 42 enables it to pass freely through
the introducing catheter 10, and the outer diameter of the distal segment
44 enables it to pass through a fallopian tube as described in more detail
below. The shaft 42 has an inner diameter of 0.041 inch (1.04 mm) and the
segment 44 has an inner diameter of 0.031 inch (0.79 mm). Approximately
six cm of the distal segment 44 projects beyond the distal tip 14 of the
introducing catheter 10 when the access catheter 40 is fully inserted
within the introducing catheter 10. Insertion is limited by luer 45 which
serves as a stop. The details of construction of the distal segment 44 are
described below.
The alignment bands 46 on the proximal portion of the shaft 42 are similar
in composition and spacing to the bands 16 of the introducing catheter 10.
The use of the bands is described below.
It is desirable to use a guide 50, FIG. 5, during insertion of the access
catheter 40 to provide extra pushability and trackability through the
fallopian tube. As described above, the guide 50 is insertable through the
lumen of the access catheter 40 to increase its column strength which is
useful for advancing the access catheter 40 through the collapsed,
narrow-diameter isthmus I of the fallopian tube F. Additionally, the
entrance E may be more easily located using the flexible spring tip 52 of
the guide 50, after which the access catheter 40 can be advanced along the
guide 50 through the entrance E and into the fallopian tube F.
The guide 50 has a spring tip 52 approximately 6 cm in length and a main
shaft 54 formed of a solid wire 0.016 inch in diameter. Preferably, the
wire 54 is coated with low friction Teflon to a thickness of 0.0003 to
0.0005 inch, to establish the total outer diameter less than or equal to
0.017 inch. The guide 50 has a useful overall length of 49.2 cm. Visually
perceptible bands 56 are provided on a proximal segment 57. Distal band 58
is 40.9 cm from the distal end 55 of the guide 50.
The segment 57 is formed of a sleeve placed over the Teflon coated wire 54
to provide a more suitable substrate for the bands 56 than would be
provided by the Teflon surface of the wire 54. An acceptable material for
the segment 57 is "K resin" (styrene butadiene) which readily accepts
permanent ink. The segment 57 is approximately 8 cm in length and has an
outer diameter of 0.026 inch. A luer 59 serves as a stop to limit
insertion through the access catheter 40. Further, the luer 59 serves as a
handle and as a visual aid for the physician to readily locate and
manipulate the proximal end of the guide 50. Additionally, the luer 59
assists securing the sleeve 57 in position on the wire 54.
The small diameter and great flexibility of the guide minimizes risk of
puncture of the fallopian tube. Unlike an artery which is substantially
round, the fallopian tube normally is in a collapsed condition which
renders insertion difficult. The combination of a guide, an access
catheter, and a transfer catheter provides a substantial advantage over
the conventional practice of using only a transfer catheter within the
fallopian tube.
The transfer catheter 60, FIG. 4, is a single lumen catheter and has a
usable length of approximately 43.3 cm. The transfer catheter 60 extends
approximately one cm beyond the distal end of the access catheter when
fully inserted into the access catheter 40. The transfer catheter 60
therefore can be inserted a maximum of 7 cm into the fallopian tube, as
described in more detail below.
The inner and outer diameters of the transfer catheter 60 are selected
based on several considerations. The minimum inner diameter is
approximately 0.014 inch (0.36 mm) to accommodate a zygote. The outer
diameter is approximately 0.027 inch (0.66 mm) so that the walls can be
thick enough to provide sufficient stiffness (column strength) for
pushability.
The transfer catheter 60 has a shaft 61 formed of an inert material such as
ethylene tetrafluroethylene (ETFE), available from DuPont, which is
compatible with the reproductive cells. ETFE is desirable because it can
be sterilized using gamma radiation. A support sleeve 62 is formed of high
density polyethylene (HDPE) to provide a strain relief section which
assists transition to the luer 64. The sleeve 62 is approximately 1.0 cm
in length, and has an outer diameter of 0.040 inch. The luer 64 accepts
the distal end of a syringe for discharging reproductive cells when the
distal tip 66 is at a desired location, as described in more detail below.
The coaxial catheter system is used as follows for depositing reproductive
material into a fallopian tube. The introducing catheter 10 is inserted
into the vagina V, FIG. 6, through the cervix C and into the uterus U with
the assistance of the obturator 30. It is desirable to place the distal
tip 14 of the introducing catheter 10 at the entrance E to the fallopian
tube F. The physician determines beforehand the depth to which the
introducing catheter 10 must be inserted by "sounding" the uterus to
determine the actual length for the particular patient. One of the bands
16 is selected by the physician for alignment with the external opening 0
of the cervix C. A short-length sleeve 21, shown in phantom in FIG. 1, may
be placed around the exterior of the shaft 12 to serve as a removable stop
and to designate the selected band. The slidable sleeve 21 has an outer
diameter of 0.375 inch and an inner diameter of approximately 0.104 inch
which fits snugly over the shaft 12. It is desirable for at least one of
the bands 16 to be positioned between 7 to 10 cm, and most preferably a
band is located at 9 cm from the distal tip 14. The illustrated
introducing catheter 10 has bands located between 6 to 11 cm from the
distal tip 14 to accomodate a wide variety of patients.
After the obturator 30 is removed and the introducing catheter 10 is in
position within the uterus, the access catheter 40 is advanced through the
introducing catheter 10 and through the isthmus I of the fallopian tube F.
The bands 46 of the access catheter 40 are aligned by the physician with
the sealing device 23 of the introducing catheter 10. When the distal band
48 is aligned with the sealing device 23, the distal tip 49 is flush with
the distal tip 14 of the introducing catheter 10. The distal band 48 is
disposed approximately 30.2 cm from the distal tip 49; it is desirable to
have one or more of the bands disposed between 28 to 30 cm from the distal
tip 49. The distal tip 49 is insertable a maximum of six cm beyond the
distal tip 14 of the introducing catheter 10 and into the fallopian tube
F, which is a sufficient depth to enable the transfer catheter to be
inserted well beyond the isthmus I of the tube F, as described in more
detail below. The sealing device 23 is then tightened to secure the access
catheter 40 in position.
When the guide 50 is used to assist insertion of the access catheter 40
into the fallopian tube F, the guide 50 is preloaded into the access
catheter 40 and the combination is then inserted through the introducing
catheter 10. According to his discretion, the physician can either advance
the guide 50 alone through the entrance E, and then subsequently advance
the access catheter 40 into the isthmus I, or the physician can advance
together the combination of the guide and the outer catheter. The distal
band 58 is disposed approximately 40.9 cm from the distal tip 55 of the
guide 50. Preferably, at least one band is located between 38 to 48 cm
from the distal tip 55.
The transfer catheter 60 is loaded according to a conventional procedure
for transfer catheters in which semen and an egg are alternately
introduced, separated by an air bubble, as described for example in In
Vitro Fertilization, Jones, Jr. et al., editors, published in 1986 by
Williams and Wilkins. A 20 microliter plug of growth media such as Hams
Solution is drawn through the distal end 56 of the transfer catheter 50. A
20 microliter air bubble then is drawn, followed by alternating 30
microliter plugs of media containing reproductive cells and 20 microliter
air bubbles. Twenty microliters of air separates the distal most plug of
media containing reproductive cells from the distal end 66. In a zygote
intrafallopian transfer procedure, one or more zygotes separated by air
bubbles are loaded into the distal end of the transfer catheter. In either
transfer procedure, the load is discharged using a minimum amount of a
culture medium, e.g. less than 100 microliters, delivered through a
syringe mated to the luer 64 of the transfer catheter 60.
After it is distally loaded, the transfer catheter 60 is advanced through
the access catheter 40 into the fallopian tube F. The depth of insertion
is determined by the physician. A fallopian tube typically has a total
length of approximately 10-11 cm, and it is considered desirable by some
physicians to deliver the gametes or zygotes at least half way along the
length of the tube to more closely simulate natural fertilization.
Visually perceptible markers may be provided on the shaft 61 of the
transfer catheter; in the illustrated embodiment, the sleeve 62 and the
luer 64 provide a reference relative to the proximal end of the access
catheter 40 for estimating the depth of insertion.
The details for the construction of the access catheter 40 are as follows.
The distal segment 44 of the access catheter, 40 is a laminate
construction including a polymeric liner 70, FIG. 7 a stainless steel
ribbon wire spring 72 and a polymeric sleeve 74. The ribbon wire 72 serves
as a reinforcing material to resist constriction of the passage 75 which
communicates with a distal opening 77. An additional advantage of the
stainless steel is that it is opaque to ultrasound which may be used to
monitor an access procedure. Alternatively, the reinforcing material is a
radiopaque material such as platinum.
The object of the laminated construction is to provide a large inner
diameter (0.031 inch) lumen to accept the transfer catheter with some
tolerance, and to provide a small outer diameter of approximately 0.040
inch to enable passage through the fallopian tube. This object is achieved
in the illustrative embodiment using a laminate construction of two tubes
which are alternately expanded and compressed, as described in more detail
below, to provide exceedingly thin walls. It is desirable for the distal
segment 44 to be less than | | |
