Note: Descriptions are shown in the official language in which they were submitted.
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Medical_Instrument
This invention relates to improvements in medical instruments.
One of the most commom medical procedures is the insertion
of a medical instrument into a body passage, for example the ;
5 insertion of a swab or catheter into the urethra, and, despite
great advances having been made in the prevention of infection
in many areas, this procedure has continued to cause introduction
of infection into organs such as the bladder.
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10 It is standard practice for catherisation to be performed
only after the area around the passage has been thoroughly
clPaned, the catheter has been sterilised and the operator
has donned surgical gloves and mask, and yet infection has still
been common. The reason for this has now been deduced as
15 resulting froln bacteria which are present within the body
passage itself particularly at its outer end, and which it
is difficult if not impossible to remove prior to insertion
of the instrument. As the instrument enters the passage,
therefore, it comes into contact with the bacteria and carries
2û them along the passage with it, thus causing infection at the
top of the passage. No amount of precleaning of the area
external of the passage will prevent this.
A similar problern has beset the operation of taking swab samples
25 from a desired position within a body passage, as the act of
introducing the swab into the passage causes the swab to pick
up bacteria before it reaches the desired position, thus
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preventing an accurate bacteria count from being obtained at
that position. Withdrawal of the swab then picks up more bacteria,
or indeed can lose sorne of the bacteria already on it. The
taking of swab samples from a passage has therefore been rather
5 haphazard and inaccurate.
Several proposals have previously been made to prevent the
instrument carrying bacteria along the passage, but none of these
has proved entirely successful. For example, U.S. Patents Nos.
10 3?332,424 (Minteer), 3,90~,635 (Vick) and 3,908,663 (Vick)
describe catheters having a tube of thin flexible material
and a rigid collar secured around one end of the catheter tube.
In use, these catheters are operated by placing the collar
around the entrance to the body passage and pushing the tube
15 through the collar so that the tube progressively everts along
the passage. In this way movement of the tuoe wall relative to
the passage wall is reduced so that bacteria are less likely
to be carried along the passage, but bacteria can nevertheless
be forced into the leading open end of the tube as it everts.
20 These bacteria are then redeposited further up the passage on
continued eversion of the tube. While these previnusly proposed
catheters are an improvement over a basic catheter tube they
still cause a degree of contamination by carrying bacteria
further up the passage.
U.S. Patent No. 3,669,û99 (Silverman) describes and claims a
similar system to the above-described prior art in that it has
everting tubing for contacting a body cavity wall, but in this
case the ends of the tubing are secured and sealed to a rigid
30 cylindrical tube surrounding the tubing, so that the tubing
forms a closed toroidal chamber which is then filled with a
fluid. A long cylindrical medical instrument can then be
pushed through the tubing, and the pressure of fluid causes
the tubing to evert as the instrument passes through it. This
35 previously-proposed arrangement is complex as a fluid inlet
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must be provided in the rigid tube for injection of
fluid to an appropriate pressure, and the presence of
the toroidal chamber makes the apparatus rather wide
and therefore somewhat uncomfortable for the patient.
5 It is also relatively expensive to manufacture.
According to the present invention there is provided a
urinary catheter assembly for use in inserting a catheter
through a urethra into a bladder, the urethra being
10 contaminated with bacteria in an outer portion of its
length, the assembly comprising a catheter, a hollow
sheath having an impervious side wall, the catheter being
slidable within the sheath and the sheath having a distal
end which is normally closed and openable to allow passage
15 of the catheter through it, and a stop member extending
outwardly from the sheath for engaging an area around the
entrance to a urethra on penetration of the sheath into
the urethra to prevent further such penetration, the stop
member being spaced from the distal end of the sheath by
20 a distance substantial~ly equal to said contaminated outer
portion of the urethra.
In use, the sheath is inserted into the urethra preferably
to an extent whereby it penetrates slightly beyond bac-
25 teria within the passage adjacent its outer end, so thatthe catheter is isolated from such bacteria by the sheath.
The catheter is then pushed through the closed end of the
sheath to continue along the passage to the bladder, and
in this way bacteria are not carried into the bladder by
30 the catheter.
The sheath is provided with a stop member, such as a
portion of increased diameter, for example in the form of
a collar, spaced from the sheath ends to engage the area
35 around tne passage entrance and thus limit the penetration
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of the sheath; the stop member can be set a predetermined
distance along the sheath depending on the usual extent of
bacteria within the urethra.
5 A very effective manner of providing the openable sheath
end is for that end portion to be slit so that in its
normal state the slit is closed to seal the sheath end,
but when the distal end of the catheter is pressed against
it from within the sheath the slit opens to define an
10 aperture for passage of the body. For this to operate
most effectively the sheath end portion should be resilient
so that the slit closes again on retraction of the catheter
into the sheath; bacteria are therefore prevented from
entering the sheath on removal of the catheter from the
15 passage~ In an alternative~arrangement the sheath can
have a membrane across its end, the membrane being
rupturable on pushing the catheter against it.
For ease of insertion as well as for effective sealing,
20 the end portion of the sheath is preferably tapered.
The sheath may be in one piece or may alternatively
comprise a number of parts which together produce the
desired features For example the sheath may have an open-
25 ended tubular body portion within which the catheter slides,and a cap enveloping one end of the body portion and having
an openable closed end. In any event it is preferable that
the sheath should be sufficiently long to allow it in use to
be held externally of the body passage thus making the
; 30 instrument easy to use.
The assembly of this invention can also be modified to
allow its use without the necessity for the user to wear
surgical gloves and other protective clothing, by making
35 the sheath longer than the portion of the catheter for
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insertion into the body passage, so that that portion of
the catheter is contained within the sheath beEore use.
In this way the user will handle the catheter only in
areas which will not enter the passage, so bacteria will
5 not be transferred into the passage from the userls hands
by the catheter.
To ensure further the isolation of bacteria a second sheath
can be provided movable with the catheter and connected
10 with the first sheath in a manner allowing relative longitu-
dinal movement between them while retaining between them a
barrier against passage of bacteria to the catheter. The
sheaths may be connected in a telescopic arrangement with
one of the sheaths being slidable within the othér.
15 Alternatively a collapsible connection may extend between
them, for example a "concertina" connection. The second
sheath may be secured to the catheter so as to be perman-
ently movable with it, or it may be of flexible material
so that the catheter can be gripped through the second
20 sheath by applying finger pressure.
The sheath should be inserted into the body passage to an
extent whereby its distal end penetrates beyond bacteria
disposed adjacent the proximal end of the passage, so
25 that bacteria are not carried further along the passage
by the catheter.
Embodiments of the invention will now be described by way
f example with reference to the accompanying drawings, in
30 which:
Fig. 1 is a schematic diagram showing the distribution
of bacteria in a female urethra;
Fig. 2 is a side sectional view of a catheter with its
introducer, in accordance with the invention;
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Fig. 3 is a side sectional view oE the catheter and
introducer of Fig~ 2 in use;
Fig, 4 is an end elevation corresponding to Fig. 2;
Fig. 5 is an end elevation corresponding to Fig. 3;
Fig. 6 is a side sectional view of an alternative
form of the introducer, for use in the assembly of
this invention; and
Fig. 7 is a side sectional view of a further alter-
native form of a urethral catheter and introducer, in
accordance with the invention.
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Referring to Fig. l, the bladder 1 communicates with the
outside through the urethra 2. The bladder 1 and upper
urethra 2 are sterile, but~the lower urethra and the area
15 surrounding it are highly contaminated by bacteria 3.
When the bladder is to be drained by catheterisation the
external area around the urethra 2 is thoroughly cleaned
but it is very difficult to clean the lower urethra inter-
nally so a considerable amount of bacteria 3 remain.
20 Insertion into the urethra 2 of an unprotected catheter,
swab or other medical instrument therefore causes the
bacteria 3 to be carried further along the urethra 2 and
contaminate the upper urethra and bladder if the instrument
is inserted sufficiently far.
Referring now to Figs. 2 to 5, the problem of bacteria 3
being carried along the urethra 2 is obviated or mitigated
by pr~viding a catheter tube 4, of conventional plastics
material, within a sheath 5 whose side walls are impervious
30 to bacteria. The sheath 5 is formed by a plastics outer
tube 6 coaxial with the catheter tube 4 and having over
its distal end a latex rubber cover 7. The
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distal end of the cover 7 is cross-cut so as to provide a seal
against passage of bacteria when in its closed position as in
Figs. 2 and 4, while allowing penetration of the outer tube
6 and catheter tube 4 on application of pressure by them, as
5 shown in Figs. 3 and 5.
In use, the catheter is inserted, cover 7 first, into the
urethra 2 until the collar 8 abuts the area around the urethra
entrance and prevents further penetration; at this stage the
10 cross-cut end of the cover is at the area marked "X" in Fig. l.
As the collar 7 is spaced from the ends of the sheath 5 the
sheath can still be easily gripped by the user when fully
inserted into the urethra, by holding the outer tube 6. The
outer tube 6 is then pushed through the cross-cut end of the cover
15 7 to extend further into the urethra but not to penetrate into
the bladder l. Because of the closed end of the cover 7 during
initial insertion the outer tube 6 becomes contaminated
with bacteria 3 only to insignificant degree, if at all, as
it extends through the cover 7.
In the final stage of insertion the catheter tube 4 is pushed
through the outer tube 6 and into the bladder l. The bladder l
can then be drained without risk of infection.
25 Instead of pushin~ the outer tube 6 through the cross-rut
end of the cover 7, the catheter tube 4 may be pushed straight
into the bladder l through the cross-cut end. In this way
there is a slightly greater risk oF bladder infection but in
fact it is insignificant.
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The inner diameter of the outer tube 6 is the same as the
outer diameter of the catheter tube 4 or slightly less, and in
this way the catheter tube 4 is retained in the outer tube 6
and will not fall out during use. In an alternative, the diameter
35 of the aperture in the rubber collar 8 can be such that it
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"pinches" the outer tube 6 and catheter tube 4 to
achieve the same object.
It is also of importance in this embodiment of the
5 invention ~hat the outer tube 6 should be of greater
length than the maximum distance through which the
catheter tube 4 will project in use from the cover 7.
In this way any contamination of the catheter tube 4
externally of the outer tube 6 will not be transferred
10 along the outer tube 6 and into the urethra 2 or bladder
1. Further when the catheter is used in the manner
described above, the outer tube 6 should not be pushed
through the cover 7 by an extent greater than the length
of the cover. This further prevents any bacteria being
15 transferred into the bladder or urethra.
Referring now to Fig. 6, instead of providing an outer
tube 6 with a rubber end cover 7, the sheath 5 is in one
piece, its distal end tapering and being cross-cut to
20 provide the same effect as the cover 7.
Referring now to Fig. 7, the catheter tube 4 has two
outer tubes 10 and 11 disposed coaxially around it. The
second outer tube 11 is of smaller diameterthan the first
25 outer tube 1~ and extends into it in telescopic fashion
at 12. The first tube 10 has at its opposite end a
rubber cover 7 held on the first tube 10 by a rubber
collar ~ whic~h also acts as a stop member as in Figs. 2
to 5; the cover 7 is cross-cut at its distal end.
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The free end of the second sheath 11 is secured to the tube 4
by a tight-fitting sleeve 13 which prevents relative movement
between the tube 4 and sheath 11.
5 The sheaths 10 and 11 are made of rigid plastics material
while the tube 4 is of pliable plastics material and the
cover 7 is of soft rubber.
The instrument of Fig. 7 is used in similar fashion to those
10 of Figs~ 2 to 5, except that ~he catheter tube 4 is not
handled directly, being protected by the tubes 10 and 11. When
the catheter tube 4 is to be pushed through into the urethra this
is achieved by gripping and pushing the second tube 11 into the
first tube 10.
The rigidity of the outer tubes 10 and 11 allows the pliable
tube 4 to be easily introduced. A thin plastics cover 14 is
secured to both outer tubes 10 ancl 11 to prevent bacteria entering ~ -
between the tubes and thus contaminating the tube 4.
The arrangement can be readily modified at the end 7 to allow ~;
it to be used in, for example,epidural operations.
