Note: Descriptions are shown in the official language in which they were submitted.
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DE5CRIPTION
FLOW REGULATING DEVICE FOR ARTERIAL CAT~TER SYSTEMS
Technical Field
-
This invention pertains generally to intravenous
: catheter systems used in monitoring arterial functions
and in the infusion of medical fluids to a patient. In
5 particular, the invention relates to flow apparatus for
controlling the flow of fluid at a desired continuous
rate and to provide for intermittent, manually controlled
larger flows of fluid to rapidly flush the catheter system.
Background
Intravenous catheterization is a very useful pro-
; cedure available for clinical monitoring of blood system
; and related parameters including arterial pulse waveform,
stroke volume, heart rate, cardiac output, duration of
; systole, and systolic, diastolic and mean pressures. In
15 addition, blood can be withdrawn for blood gas analysis.
To provide reliable operation over periods which may
amount to several days, it has been found essential to flush
the catheter continuously during its use with a regulated,
continuous infusion of a relatively small flow of a liquid to
20 prevent occlusion of the intravascular end of the catheter
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by blood c~agul~tion, Continuous flushing s~stems have
been proposed which utilize capillary tubes as flow
resistors, wlth the flushing solution ~lowing therethrough
under pressure. See, for example, U.S. Patent No 3,675,~91
issued to Gordon S ~eynolds, et al on September 18, 1970,
and an article appearing on pages 675-678 of the Journal
of Thoracic and Cardiovascular Surgery, Volume 57, No. 5,
May 1969.
Generall~, the prior systems employed an objectionable
large amount of apparatus including numerous stopcocks,
with resulting loss of fidelity in the operation of the
system. The device disclosed in U.S. Patent No. 3,675,891
overcomes many of the deficiencies inherent in the earlier
systems by providing a relatively small unitary piece o~
apparatus which was constructed so as to eliminate the use
of all stopcocks. A resilient valve was provided to control
a bypass around the capillary flow resistor, with the valve
being operated by manually pulling a valve stem which
extends longitudinally from the apparatus. The valve and
stem system of such device, however, has certain drawbacks.
For example, the protruding stem is subject to entanglement
in tubing, bedding, or other paraphenalia resulting in
possible undesired opening of the valve or breakage of the
valve stem so as to preclude proper operation of the device.
The valve stem can also be broken by pulling the stem to one
side or the other rather than longitudinal, and the valve
has also been found to occasionally fail in the open
positlon. In addition, the valve and stem system is
generally difficult to operate with one hand, and for all
practical purposes, requires two-handed manipulation.
The principal objective of the present invention is
to provide an improved regulating device which is reliable
and easy to operate, as well as being simple in construction.
A particular objective of the invention is to provide a
small, streamlined device for connection in the catheter
system which can be operated easily with one hand and
which does not include stopcocks or stem actuated valves
as in the devices of the prior art.
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Sum~ary of the Invention
~According to the invention there is a flow xegulating
device which provides a continuous regulated flow of a
medical fluid to an intravenous catheter system used in
S monitoring arterial functions and in the in~usion of medical
f~uids to an artery or vein, and which also provides for
an intermittent, manually controlled, larger flushing flow
of fluid to the catheter system, said device comprising
a control member having an inlet means adapted to be
connected to a source of a medical fluid and an outlet
means adapted to be connected to an intravenous catheter;
a first passaye connecting said inlet and outlet means for
fluid flow communication therebetween, said first passage
at least in part comprising a section of flexible conduit
having valve means positioned therein, said valve means being
adapted to open and permit said larger, flushing flow of
fluid to pass through said first passage when the conduit
is squeezed and to close when the conduit is released; and
a second passage by-passing said valve means and connecting
said inlet and outlet means, said second passage containing
flow restriction means which limits the flow of fluid there-
through, under a given pressure to a desired amount.
Description of the Drawings
Fig. 1 is a diagramatic illustration of a device in
accordance with this invention in operative association with
a catheter system which is inserted into the arm of a patient,
the device itsel being exaggerated for purposes of illus-
tration;
Fig. 2 is a perspective view of a preferred embodiment
of the device;
Fig. 3 is a central, vertical section through the
device shown in Fig. 2; and
Fig. 4 is a vertical section of a modified version of the
plug valve of Fig. 3.
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Detailed Desc~iPtion
. ,
The deyice of the present invention is adapted to --
be incorporated in various catheter systems~ As used
throughout the specification and claims, the term "catheter
S systems" is meant to include syste~s using catheters, cannulas,
or other tubes inserted into the arterial system of a pa-tient
and used to monitor arterial functions and parameters as
- well as withdrawing blood from or infusing medical fluids
into the arterial system.
By way of example, the flow control device is shown in
the drawing and will be described herein as incorporated
into a catheter system for monitoring arterial pressure and
recording of arterial pulse waveforms. The catheter used
in such a system is very thin, having an inside diameter of
about one-half millimeter~ The catheter must be maintained
in open and operable condition for transmitting pressure
pulses. T'ne tendency for a blood clot or other occlusion
to form at the end of the catheter positioned within the
arterial system is greatly reduced by continuously infusing
a sterile solution into the arterial system through the
catheter in an amount which will not harm the patient but
will retard the formation of occlusions in the catheter.
Generally, depending on the size of the patient, from
about 2cc to about 7cc of solution per hour has been found
to be safe and beneficial.
In accordance with the present invention, means are
also provided for manually flushing the catheter system from
time to time with a momentary increase in the flow of solution
through the catheter. The increased 10w of fluid clears the
catheter of any clots or occlusions which have formed or
are being formed. In addition, the increased flow of
fluid permits rapid clearing of all air from the system
during the installation of the catheter into the arterial
system of the patient, as will be discussed more fully here-
inafter.
A preferred embodiment of the flow control device isshown in the four figures of the drawing, wherein similar
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componen~s of the device are identified with the same
refere~ce nu~eral, The device comprises a control member
10, which as shown in Fig, 1 is adapted to be connected
by tube 11 to a suppl~ of a medical fluid in con~ainer 12
The control member 10 is also connected by tube 13 to a
catheter which has been positioned within the arm of a
patient 14. Means are provided for connecting the control
member 10, in fluid flow communication through tube 15, to
diagnostic apparatus (not shown in the drawing) which is
capable of monitoring various arterial functions such as those
mentioned previously. A variety of diagnostic apparatus is
well known to the medical art and does not, per se, constitute
part of the present invention. As will be more fully des-
cribed hereinafter, the means which are provided for
connecting tube 15 to control member 10 can also be used for
hypodermic injections to and for withdrawing of blood samples
from the patientO
The construction of the control member 10 is best shown
in Figs. 2-4, and will be described with reference thereto.
As illustrate~, the control member 10 consists of a bo~y
member 16 having upstanding end caps 16a and 16b, respect-
ively, such that in side elevation, the body member 16 has a
broad, generally U-shaped profile. The end cap 16a is pro-
vided with inlet means for connect:ing the control member 10
to the tube 11 which, in turn, is connected to a supply
of medical fluid, such as the container 12 shown in Fig. 1.
The inlet means as shown in Figs. 2 and 3 comprises a short
piece of tubing 17 which is securely af~ixed to the end cap
16a at one of its ends and has a male fitting 18 attached
to its other end. The fitting 18 is adapted to releasably
engage a female fitting 19 on ~he end of tube 11. Various
types of fittings, some being, as illustrated, adapted for
interlocking engagement between lugs on the male fitting
and internal thread-like receptacles on the female fitting,
and some being adapted for simple sliding engagement, are
commercially available for use in the present invention.
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The other end cap 16b is provided with outlet means
which is adapted to be connected to an intravenous catheter
by way of an appropriate tube, such as tube 13 shown in Fig.
1. As illustrated in Figs. 2 and 3, the outlet means com-
prises a fitting 20 which is adapted for connection to amutually corresponding fitting on a fluid conveying tube lead-
ing to the catheter. The fitting 20 can be any of various
type fittings conventionally used for connecting medical
tubing together or to other medical apparatus. As shown, the
fitting 20 is of the type having an internally threaded
receptacle 20a (Fig. 3) adapted to receive a male fitting
having lugs thereon for engagement with the threads of the
receptacle.
The outlet means at end cap 16b preferably also includes
a second fitting 21, which, as shown, is a male fitting
having side lugs 21a which are adapted to releasably engage
the threads of a mutually corresponding fitting on a tube,
such as tube 15 shown in Fig. 1, for connecting the control
member 10 to diagnostic apparatus capable of monitoring various
functions such as blood pressure, etc., as mentioned pre-
viously. The fitting 21 could be of the female type such
as fitting 20; however, inasmuch as the fitting on the diag-
- nostic apparatus is likely to be oE the female type, and
connecting tubing conventionally has a male fitting at one
end and a female fitting at the other end, it is advantageous
to make the fitting 21 of the male type, as shown.
A fluid flow passage connects the inlet and outlet means
in the end caps 16a and 16b of body member 10. As illus~ra-
ted in Figs. 2 and 3, the flow passage comprises bores 16c
and 16d through the respective end caps 16a and
16b which are in flow communication with the tube 17 and
fitting 20, respectively. The end caps 16a and 16b have
inwardly facing hubs 16e and 16f, which are adapted to
receive the respective ends of a flexible conduit 22, so
that the conduit 22 connects the bores 16c and 16d for fluid
flow communication therebetween. The flow passage thus
comprises the bores 16c and 16d of the end caps 16a and
16b together with the flexible conduit 22.
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A ~alve ~eans is positioned within the 1exible
conduit 22 and is adapted to open and permit the intexmittent,
larger, flushing flow of fluid to pass through the flexible
conduit 22 when the conduit 22 is squeezed, and to close
when the squeezing action on the conduit 22 is terminated.
Preferably, the valve means comprises a substantially cy-
lindrical plug member 23 (Fig. 3) positioned coaxially
within the flexible conduit 22. The plug member 23 has a
raised band 23a thereabout intermediate its ends, with the
band 23a having a sufficient diameter that its exposed sur-
face forms a substantially flow tight seal with the interior
wall of the flexible conduit 22, so that when the flexible
conduit is not being squeezed, fluid is subtantially
completely prevented from flowing around the plug between
the raised band 23a and the interior wall of flexible con-
duit 22. The portion of the plug member on either side of
the raised band 23a is of a reduced diameter and thus an
open flow space 24 is formed between the flexible conduit
22 and the portions of the plug member 23 on either side of
the raised band 23a.
When the flexible conduit 22 is subjected to a squeezing
action in the vicinity of the raised band 23a, the seal
between the raised band 23a and the interior wall of the
flexible conduit 22 is broken, due to deformation of the
flexible conduit 22 which creates flow channels extending
across the raised band 23a. Fluid can then flow around the
plug member 23 and through the flexible conduit 22. Upon
termination of the squeezing action on the flexible conduit
22, the seal between the raised band 23a and the interior
wall of the flexible conduit 22 is automatically re-established,
thereby terminating the flow of fluid around the plug member
23. Advantageously, the base portion of the body member 16 has
concave depressions 16g (Fig. 2) in the side thereof facing
-the flexible conduit 22 and the two sides thereof extending
from the flexible conduit, respectively. The concave de~-
pressions form finger guides on each side of the control
member 10 which aid in positioning one's fingers for squeezing
the flexible conduit 22.
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A sec~nd pass~ge is ~royided in the control member 10
for by-passing the valve ~eans in the flexible conduit 22 and
connecting the inlet and outlet means of bod~ member 16,
Such a by-pass passage could be routed through the body
5 member 16 from the inlet means in end cap 16a to the outlet
means in end cap 16b. Preferably, however, the second passage
is combined in the valve means itself as shown in Figs. 3 and
5. In the preferred mode, the plug member 23 is positioned
concentrically in the flexible conduit 22 and is provided
10 with a bore extending longitudinally through the plug member
23 which by-p~asses the valve means in the flexible conduit
22.
Flow restriction means is provided in the second passage
for limiting the amount of fluid passing through the second
15 passage to a desired relatively small rate.
As illustrated in Fig. 3, the flow restriction is
advantageously provided by forming at least a portion of the
bore 25 into a capillary section 25a having a very small
diameter in the order of several hundredths of a millimeter.
20 The capillary section 25a of bore 25 is shown in Fig. 3 in
greatly exaggerated proportions for purposes of clarity,
since the portion 25a in reality is so small in diameter as
to be practically invisible without the use of some type
magnification. By incorporating capillary sections 25a of
25 different diameters and lengths, a broad series of appara-
tus can be readily produced from which individually sized
units can be chosen which will deliver the desired amount
of fluid under the given upstream pressure which is to be
utilized in the particular application.
In an alternate embodiment of the plug member 23 shown
in Fig. 4, the flow restriction is provided by positioning
a resistance element 26 in the bore 25 of the plug member
23. The resistance element 2~ comprises a marine-bore
capillary tube, with the diameter of the bore in the ele-
35 ment 26 being very small, in the order of hundredths of
a millimeter. The bore in the element 26 of Fig. 4 is
shown in greatly exaggerated proportions for purposes of
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illustration. To aid in positioning the marine-bore
resistance element 26 in the bore 25 of plug member 23,
the bore 2~ has a downstream section having a reduced
diameter as shown in Fig. 4. The capillary tube 26 is
5 then forced into bore 25 from the upstrea~ end there-
of until it abuts the edges of the reduced diameter
section of bore 25. The outside diameter of the resist-
ance element 26 is sufficient so that a tight, non-
leaking seal is made between the external surface of the
10 element 26 and the bore 25.
Preferably, the second passage extending through
the plug member 23, i.e., the bore 25 is coaxial with
the longitudinal axis of the plug member 23. Also, the
downstream end of the plug member 23 is advantageously
tapered as shown in Figs. 3 and 4. The tapered end of
the plug member 23 is received in a flared receptacle
in the end of hub 16f. The flared receptacle is formed
symmetrically about the a~is of the first passage, and,
thus, when the tapered end of the plug member 23 is
20 received therein, the bore 25 of plug member 23 is main-
tained in axial alignment with the bore 16d in end cap
16b.
In use, the flow device of this invention is
efficient, reliable, and easy to manipulate. Prior to
the insertion of the catheter into an artery or vein of
the patient, the flow device of this invention is connected
between the catheter and a source of medical fluid. The
medical fluid can be contained in a pressurized vessel,
or a container which is elevated sufficiently above the
patient s~ as to provide for the working upstream pressure
necessary for proper flow of fluid through the bore 25 of
the device.
All air bubbles are eliminated from the catheter
system by squeezing the flexible tube 22, thereby flushing
the system with a relatively large flow of fluid which
flows past the valve plug 23. When all air bubbles have
been eliminated, the squeezing action on tube 22 is termin-
ated and the relative large flow of fluid stops, with only
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the limited~ small ~lo~ o fluid through the second
passage or bore 25 continuing, The catheter is then
inserted into the patientls body, with the small flow of fluid
passing through the catheter into the vein or arter~ of the
patient. This continuous flow of fluid through the catheter
reduces the occurrence of blood clotting or other occlusions
occuring in the end of the catheter positioned within the
patient's body.
The Eitting 21 on the end cap 16b of the flow control
device is, of course, connected to whatever indicating or
recording means is desired, or to a pressure transducer
for oscilloscopic observations. To assure quality of
the information obtained from the catheter system, the system
is manually flushed from time to time with a relatively rapid
flushing flow of fluid by simply squeezing the flexible
tube 22 of the flow control apparatus to permit fluid to
flow around the valve plug 23. When the squeezing action
is terminated the relatively rapid flow of fluid through
- the catheter ~tops, and the smaller flow of fluid from the
bore 25 continues in its ~ormal course. The periodic flushing
of the catheter system is accomplished quickly and easily,
using only one hand of the person handling the apparatus.
The~device of this invention can also be advantageously
used in combination with a stopcock downstream of the unit 10
to obtain blood samples from the patient or to infuse a
desired amount of medication or blood samples to the patient
without requiring a second catheterization, cannulation or
hypodermic injection of the patient.
Although the apparatus has been shown and described in
connection with a catheter system wherein the catheter is
placed ïn the arm of a patient, it is to be understood that
the catheter may be entered into various veins or arteries
of the body as the general medical situation requires. It
is further to be understood that the present disclosure,
including the detailed description o~ a preferred embodiment
of the invention, is made by way of example and that various
other embodiments are possible without departing from the
subject mattar coming within the scope of the following
claims, which subject matter is regarded as the invention.
