Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates generally to provision
of elastomeric tubing having utility for medical devices and
particularly urethral and venous catheters. Such catheters
normally are considered to be indwelling catheters in that they
are placed and retained within the urethra or a vein for an
extended period of time. Since the catheters in use comprise
a foreign body they tend to cause considerable irritation of
the tissue with which they come in contact.
The problem attendant minimizing irritation of tissue
arising from an indwelling catheter is aggravated by the fact
that it is generally preferable to provide a relatively rigid
tip for the indwelling portion to facilitate passage of the
catheter through the ur~thra or vein. It will be appreciated
that the relatively rigid tip portion of the indwelling catheter
only enhances the irritation of the adjacent~tissue, i.e.,
bladder wall or inner wall of the vein. Thus, the invention
herein resides in the proYision of catheters constructed so as
to have a tip portion that is relatively rigid so as to
facilitate placement of the catheter, which relatively rigid
tip portion in use becomes relatively less rigid whereby
irritation of adjacent tissue is minimized.
A specific example of an instance where it is
desirable to have different physical properties in various
sections of a catheter is with respect to a urethral ratheter
wherein a relatively rigid curved tip is desirable to assist
in the insertion o the catheter through the urethra which is
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curved and restrictive in the uppex seetion.
In U.S. Patent No. 3;865,666 to Shoney it is
recogni~ed that from a structural point of view a cat~eter,
such as a urinary catheter, must be sufficiently rigid to ensure
that as it traYerses the urinary tract for placement in the
bladder the catheter tube will not bend to an extent which
results in occluding or reducing the size of the drainage
lumen and the in~lation lumen utilized to expand a balloon to
retain the tip of the catheter within the bladder. While Shoney
describes a catheter having a relatively rigid tip portion a
significant problem arises by virtue of the fact that the tip
portion maintains its rigidity in use thus leading to potential
irritation of the bladder wall.
Catheters of the utility discussed herein are
generally formed of silicone polymers which due to the hydro-
phobic characteristic of the silicone may then be provided
with a hydrophilic coating derived from N-vinyl pyrrolidone
(NVP~ or acrylate and methacrylate monomers.
U.S. Patent No. 4,055, 682 to Merrill is directed to
a catheter having a silicone body portion rendered hydrophylic
by contacting it with NVP and exposing the catheter and NVP
to ionizing radiation at high dosage rates. The hydrophilic
polymeric layer of Merrill is so thin that the stiffness of the
catheter after deposition of the polymeric layer, when dry, is
not substantially greater than that of an uncoated catheter of
,
J ~ the dame composition and degree of crosslinking.
U.S. Patents Nos. 3,566,874 and 3,695,921 to Shepherd
et al are representative of indwelling Foley urethral catheters
made of natural or synthetic rubber and having an external
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coating of a hydrophilic acrylate or methacrylate polymer
grafted thereto for the stated purpose of reducing irritation
and infection considered to normally accompany the use of
catheters. Howe~er, it has been found that problems are en-
countered in use when substantially the entire outer surface
of the catheter within the urethra or vein is coated with a
hydrophilic polymer fiince as discussed in Patent No. 3,566,874
the resultant hydrophilic layers are stiff when dry.
In normal use of the conventional urethral and
veinous catheters irritation of adjacent tissue by a relatively
rigid catheter is of major concern. The present invention
provides a catheter tip structure that is relatively rigid for
purposes of placement of the catheter and which subsequent to
placement in the body is rendered less rigid so as to minimize
irritation of adjacent tissue.
The invention contemplates rendering the tip portion
of urethral and ~einous catheters formed of relatively 1exible
natural rubber or synthetic rubber, e.g. silicone rubber
relatively rigid by the application; e.g., by grafting, to such
tip portion a hydrophilic coating such as exemplified by the
referenced patents to Merrill and Shepherd et al, which coatings
render the tip portion relatively rigid.
U.S. Patent No. 3,695,921 to Shepherd et al dis-
closes the provision of hydrophilic acrylate and methacrylatecoatings that are rigid or stiff when dry. U.S. Patent No.
4,055,682 to Merrill discloses catheters having stiffness
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imparted thereto by use of a high dose of ionizing
radiation, e.g. dose to which portion 36 is subjected,
albeit the disclosure of Merrill is primarily directed
to the grafting of NVP to silicone catheter body so
that the stiffness of the catheter after coating, when
dry, is not substantially greater than that of an un-
coated catheter of the same composition and degree
of crosslinking.
The object of the invention comprising mini-
mizing irritation of tissue adjacent the tip of the
catheter is achieved by the hydrophilic nature of the
"ri~idifying" coating absorbing or adsorbing water
and thereby becoming less rigid.
The present invention provides a catheter
which comprises an elongated relatively flexible body
portion formed of a hydrophobic polymer and including
a rigidified tip portion of minor longitudinal extent,
the tip portion including a physiological fluid-
insoluble hydrophilic non-hydrated polymeric coating
for xendering the tip portion relatively rigid in a
dry state, the coating being relatively flexible when
hydrated by a physiological fluid.
Preferably, the tip portion is arcuate.
The catheter may comprise a Foley or venous catheter
and the coating may comprise a hydrophilic polymeric
coating formed from a monomer selected from the group
comprising N~vinyl pyrrolidone, acrylate and methacrylate.
Th~ invention Eurther provides a method of
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permanently reversibly rigidifying a predetermined
minor tip portion of the length of an elongated rela-
tively flexible catheter formed of a hydrophobic
polymer to facilitate insertion of the catheter into
a body cavity, comp.rising externally coating only the
tip portion with a rigidifying physiological fluid-
insoluble hydropyhilic non-hydrated polymer which is
relatively flexible when hydrated by the aqueous moiety
of a physiological fluid.
The inventi.on will be more readily apparent
from the following detailed description taken in con-
junction with the drawings in which an exemplary em-
bodiment of the invention is shown.
Figure 1 is a perspective view of an urethral
catheter embodying the invention; and
Figure 2 is an enlarged cross-section of
the tip portion of the catheter taken along the lines
2-2 of Figure 1.
Referring more specifically to Figures 1
and 2 of the drawings, there is provided an improved
conventional constant drainage bag indwelling Foley
urethral catheter 10 made of silicone rubber. The
catheter 10 includes a tubular body portion 12 ter-
minating in a tip portion indicated generally at 14.
The catheter body 10 includes a drainage lumen, not
shown, that connects a funnel 16 with a drainage port
18. An inflatable retaining
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bag or balloon 20 encompasses the tube 12, at a point
inwardly of drainage port 18, and is sealed or otherwise
connected thereto in conventional fashion. A ~ongitudinally
extending inflation lumen, not shown, terminates in an
inflation port 22 which communicates the interior of the
balloon 20 with a valve end porti~n or arm 23 for the
introduction of air to inflate the balloon 20 to retain the
catheter tip 14 in the bladder.
The body portion 12 is formed of a relatively
flexible elastom~r, e.g., silicone rubber, which is hydrophobic
and generally inert with respect to plysiological fluids it
contacts. To facilitate passage of the relatively flexible
catheter 10 through the urethra the tip portion 14 is rendered
relatively rigid by provision of a rigidifying polymeric coating
24 which is applied, in the exemplary embodiment shown, such as
from point 26 at the base of the balloon 20 to the end of the
tip portion 14. It is essential to the present invention that
the polymeric coating 24 be relatively rigid in a dry state,
generally insoluble in physiological liquids, hydrophilic, and
relatively flexible when wetted by physiological liquids such
as ~rine and blood. The coatiny 2~ thus may comprise a
hydrophilic polymer such as formed from NVP or an acrylate or
methacrylate mQnomer as set forth in the Merrill and
Shepherd et al patents. It will be understood that hydrophilic
polymers formed from NVP or acrylate and methacrylate monomers
are merely exemplary and that other hydrophilic polymers are
~ satisfactory as lon~ as they impart sufficient rigidity, in a
dry state, to the catheter tip portion 14 and are capable of
softening in use, within a reasonable time, by absorption of a
physiological fluid.
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It will thus be appreciated that the hydrophilic
coating 24 comprises means for rendering the catheter tip
portion 14 relatively rigid to facilitate placement and wherein
upon indwelling placement in the bladder the tip portion 14 is
rendered relatively flexible so as to minimize irritation of
the bladder wall.
It will be apparent that other variations may be
perceived by those skilled in the art without dPparting from
the scope of my invention as defined in the appended claims.
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