U.S. patent number 3,675,891 [Application Number 05/073,314] was granted by the patent office on 1972-07-11 for continuous catheter flushing apparatus.
This patent grant is currently assigned to Le Voy's, Inc.. Invention is credited to Karl A. Pannier, Jr., Gordon S. Reynolds, James L. Sorenson.
United States Patent |
3,675,891 |
Reynolds , et al. |
July 11, 1972 |
CONTINUOUS CATHETER FLUSHING APPARATUS
Abstract
An apparatus effecting continuous flushing of intravascular
catheters in systems for monitoring conditions in the thoracic
cavity during surgery in the intensive care ward, cardio vascular
diagnostic laboratories, etc. The apparatus embodies a small block
having therein passages for a flushing solution in one of which is
a flow resistor to limit the flushing to a small amount, a
fail-safe valve in another passage connected by a bypass to the
first passage for fast flushing with a much larger amount of
solution, and means for connecting the catheter to a monitoring
apparatus.
Inventors: |
Reynolds; Gordon S. (Salt Lake
City, UT), Pannier, Jr.; Karl A. (Salt Lake City, UT),
Sorenson; James L. (Salt Lake City, UT) |
Assignee: |
Le Voy's, Inc. (Salt Lake City,
UT)
|
Family
ID: |
22113018 |
Appl.
No.: |
05/073,314 |
Filed: |
September 18, 1970 |
Current U.S.
Class: |
251/117;
251/335.3; 604/118; 604/249; 600/486 |
Current CPC
Class: |
A61B
5/0215 (20130101); A61M 39/225 (20130101) |
Current International
Class: |
A61B
5/0215 (20060101); A61M 39/22 (20060101); A61M
39/00 (20060101); F16k 051/00 (); A61m
005/00 () |
Field of
Search: |
;251/117,38,335
;128/214F,214R |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Klinksiek; Henry T.
Claims
What we claim is:
1. A continuous flow control apparatus highly desirable for use in
a liquid flow system for pressure monitoring of hemodynamics, such
system including a catheter which must be kept patent by continuous
flushing when in use, comprising
a block having passages therein defining continuously open
inlet-outlet path through the block,
a flow resistor in the form of a marine-bore capillary tube in said
path to limit flow of liquid under pressure therethrough to a
desired minimum amount,
said block having other passages therein defining a by-pass around
the part of said path containing said resistor which by-pass is of
a size to permit a fast flow of liquid,
said by-pass being interiorly shaped to provide a valve seat,
and
a resilient valve means having a stem projecting out of said block
positioned in said by-pass and so mounted as to forcefully press
against said valve seat and automatically and instantaneously close
when said stem is released.
2. The apparatus of claim 1, wherein
said block is less than 1 inch in any direction and sufficiently
light in weight to be suspended in a fluid line.
3. The apparatus of claim 1, including
a flexible tube anchored at one end in said path, and
a fitting on the other end of said tube for connection to a
pressurized fluid source.
4. The apparatus of claim 1, wherein
said valve comprises a solid body shaped to fit against said valve
seat, and
a tubular extension on said body sealed at its outer end and which
is compressible when the valve is opened.
5. The apparatus of claim 1, including
a hollow nipple projecting from said block into said by-pass at the
end opposite said valve seat, and
said valve comprises a solid body shaped to fit against said valve
seat, and
a tubular extension on said body sealed around said nipple and
which is compressible to open said valve.
6. The apparatus of claim 5, wherein
said valve and extension are slightly longer than the space
occupied whereby there is continuous pressure urging the valve
against said seat, and
said stem extends from the valve body through said extension for
actuating said valve.
7. The control apparatus of claim 6 wherein said valve body,
extension and stem are all integral.
8. The control apparatus of claim 1, wherein
said block has a passage therethrough with one end thereof in
communication with the outlet end of said path, and
a fitting at the other end of the last said passage for connection
to monitoring means or to be plugged for hypodermic injection.
9. The control apparatus of claim 1, wherein
said resistor is sized to permit a flow not exceeding 4 cubic
centimeters per hour.
10. The control apparatus of claim 1, wherein
said by-pass narrows at one point to form said valve seat, and
a guide projection on said valve extends through the valve seat
into the narrower part of said by-pass to insure accurate seating
of the valve.
Description
SUMMARY OF THE INVENTION
Catheter cannulation of an artery or a vein for pressure
monitoring, particularly of central pressure in the thoracic
cavity, has become an indispensable technique in modern hospitals.
For example, from a central arterial catheter introduction system
and a continuous and intermittent flush system which allow high
quality clinical recording of central arterial pulse waveforms, it
is possible to measure a number of parameters from the central
pulse contour. Such parameters include stroke volume, heart rate,
cardiac output, duration of systole, and systolic, diastolic and
mean pressures. In addition, blood for intermittent arterial blood
gas analysis can be withdrawn.
It has been found necessary to continuously flush the catheter to
prevent occlusion of the intravascular catheter end by blood
clotting, and maintain catheter patency for continuous recording
over periods which may amount to several days. Continuous flushing
systems utilizing marine-bore capillary tubes as flow resistors and
applying the flushing solution under pressure have heretofore been
devised, one such being described in an article appearing on pages
675-678 of the Journal of Thoracic and Cardiovascular Surgery,
Volume 57, No. 5, May, 1969. Formerly known systems for the
intended purposes embodied an objectionably large amount of
apparatus complicated to set up and these former systems presented
a major problem in maintaining a high quality of pulse waveform.
That resulted in a loss of fidelity of recording due to clots and
high viscosity blood being in the catheter system, and the largest
contributor to this problem was stopcocks, a number of which were
used in every prior system of which we are aware. Stopcocks have
minute leaks, and although great pains were taken to maintain high
quality stopcock integrity, it was found that that was almost
impossible to achieve in practice. Even with a perfect stopcock
system there is still a small volume displaced with each pressure
pulse, and, therefore, a small amount of blood enters the catheter
tip with each pressure pulse, and even with a perfectly tight
system it was virtually impossible to keep blood out of the tip of
the catheter. Blood once entering the tip of the catheter, can
then, by a process of diffusion, penetrate further and further into
the catheter and finally an occlusion results and pressure pulse
fidelity decreases. Further, if the system were to be filled in a
reasonable time, which is essential before operation can begin, an
additional stopcock and fluid source was required.
The instant invention overcomes the foregoing deficiencies in the
provision of a small unitary piece of apparatus for connection in
the catheter flushing system and which is so constructed so as to
eliminate the use of all stopcocks in that flushing system. The
instant invention includes a resilient valve controlling a bypass
around the flow resistor and this valve is leak-proof, fail-safe,
and quick acting and permits the measurement of dynamic
characteristics of a catheter transducer system, that is, allowing
fast shut-off for square wave testing of a catheter system on an
oscilloscope or the like. With this simple form of structure, much
of the apparatus along with a complicated setup, heretofore
required, has been eliminated. Consequently, with the instant
invention, it is possible to monitor the central arterial pulse
waveform with its various derived parameters with much greater
ease, flexibility, and accuracy than was heretofore possible. The
reliability of the pressure measuring system has been increased and
the competence of the nurses, physicians and auxiliary personnel in
determining the patient's vital signs and conditions from the
central arterial waveform have also been materially increased.
Other objects, features and advantages of the invention will be
readily apparent from the following description of a preferred
embodiment thereof, taken in conjunction with the accompanying
drawing although variations and modifications may be effected
without departing from the spirit and scope of the novel concepts
of the disclosure.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
FIG. 1 is a diagrammatic disclosure illustrating a device embodying
principles of the instant invention in operative association with a
catheter cannulated patient and a source of flushing solution, the
device itself being exaggerated in the showing for purposes of
clarity;
FIG. 2 is an enlarged central vertical sectional view through the
device itself, with the valve in closed position;
FIG. 3 is a transverse sectional view taken substantially as
indicated by the line III--III of FIG. 2;
FIG. 4 is a plan sectional view taken substantially as indicated by
the line IV--IV of FIG. 2; and
FIG. 5 is a view similar to FIG. 2 but showing the valve in open
position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
While the instant invention may be incorporated in various catheter
systems and even in certain other systems for the purpose of
governing flow through the system, and is highly useful in systems
for monitoring venous and arterial pressures, by way of example,
the system is shown and will be described herein with regard to a
catheter system for monitoring central arterial pressure and permit
high quality clinical recording of central arterial pulse
waveforms. The catheter used in such a system is a thin catheter
having an inside diameter in the neighborhood of one-half a
millimeter and which is preferably made of polytetrafluoroethylene.
Such a catheter must be kept patent during use by preventing the
formation of a blood clot or other occlusion at the body end of the
catheter and sufficient infusion solution must be continuously
passed through the catheter for that purpose, but not in such
amount as to be harmful to a patient during a relatively long
period of monitoring. It has been determined that in the case of an
infant 1 cc. of infusion solution per hour is sufficient, and in
the case of an adult 2 to 3 cc. per hour of solution is sufficient.
Accuracy of the system must therefor be insured at all times, but
at the same time means must be provided to establish a rapid flush
in the first instance to clear out the system of all air and fill
the system quickly, and a rapid flush is necessary from time to
time to check the dynamics of the entire system in a manner to
avoid deceiving the observer and confusing the records.
With the foregoing in mind, in FIG. 1 we have given a diagrammatic
showing of a control device 1 embodying principles of the present
invention installed in a system for monitoring cardiovascular
pressure. The overall system includes a pressurized infusion
container 2 connected by a tube 3 to a micron filter 4 which
prevents clogging of the flow resistance element to be later
described and eliminates bacteria that may be in the infusion
solution, the filter being connected to one end of a tube 5, the
other end of which is securely affixed in the device 1. The device
is also provided with a fitting 6 to which the catheter 7 is
connected. In the illustrated showing the catheter is advanced into
the thoracic cavity of a patient 8 by way of entrance into the
radial artery. Another fitting 9 is provided on the device 1 for
connection to an indicating mechanism such as a manometer, as
diagrammatically indicated at 10, or to a pressure transducer
associated with an oscilloscope, or the fitting may be equipped
with a self-sealing plug for hypodermic injection in case such
becomes indicated. It will be understood that the instant invention
is usable in catheter systems wherein the catheter may be entered
into various veins or arteries of the body.
The device 1 may be fabricated of several parts molded of rigid
plastic material, preferably transparent, and the parts may be
secured together cementitiously, by fusing or welding, with the use
of a solvent, or in any other suitable manner. In the illustrated
showing the device consists of a housing in the form of a block
composed of a body 11, an end cap 12 carrying the catheter fitting
6, and an opposite end cap 13 carrying the fitting 9 as well as
other points of entry into passages in the body. When it is
considered that the body and end caps, exclusive of the fittings 6
and 9, may be sized as little as seven-eighths inch long,
three-quarter inches wide, and one-quarter inch thick, the
advantage of the instant invention in eliminating apparatus
utilized herebefore, including all stopcocks, in providing an
easily connectable structure and one which may be suspended from
the tubing since it weighs extremely little, and performs all the
above desired operations in controlling flow through the system,
will be at once appreciated.
The body 11 is molded to provide a passage 14 connecting the hollow
fittings 7 and 9, the fitting 9 being internally shaped as
indicated at 15 to provide a connection for a Luer fitting. Another
and larger passage 16 is provided in the body 11 and cap 13 and
this passage communicates with a cross-passage 17 by way of a
reduced outlet opening 18, the passage 17 connecting at one end
with the aforesaid passage 14. Still a further passage 19 is
provided in the body 11 and the inner end of the passage 19 tapers
inwardly to a reduced size 20 and establishes a valve seat at 21,
the reduced passage 20 also communicating with the cross-passage
17. Along the side of the passage 19 nearest the passage 16 a small
bypass passage 22 is provided in open communication with the
passage 19 and this passage connects with the passage 16 by way of
a side branch 22. The aforesaid tube 5 for connection to the
infusion system has its end portion permanently connected inside
the passage 16, the cap 13 being provided with a stop element 23
thereon to prevent the tube from blocking the branch passage 22
when the tube is initially being assembled to the cap 13.
Within the passage 16 is a flow resistance in the form of a tube 24
having a resilient apertured sealing washer 25 at each end thereof.
The resistance 24 is what is referred to as a marine-bore tube and
the actual bore 26 through the tube is but several hundredths of a
millimeter in diameter so as to afford a high resistance to the
flow of infusion solution through the resistance element. It will
be appreciated that the showing in the drawing is highly
exaggerated insofar as the instant invention is concerned for
purposes of clarity since the bore 26 in the tube 24 is virtually
invisible to the naked eye when gazing at an end of the tube.
The capillary tube 24 with its minute bore 26 provides a high
resistance to flow therethrough. An increase or decrease in the
length of tube 24 will decrease or increase the rate of flow in a
linear fashion. Since this flow is laminar, Poiseuille's law is
applicable, and therefore small variations in the radius of the
bore 26 in the resistance tube will cause relatively large
variations in the amount of flow. In calculating flow through the
system, not only the resistance afforded by the tube 24 must be
considered, but the resistances of the catheter and the filter 4
must also be taken into consideration. Those resistances are known,
that of the catheter being relatively high, namely about eighty
millimeters of mercury per cubic centimeter per minute, and that of
the 0.22 micron filter is 130 millimeters of mercury per cubic
centimeter per minute. By way of example, using a resistance tube
having a bore of a diameter of 0.05 millimeter and a length of 1
centimeter, with 300 millimeters of mercury pressure on the
infusion solution source 2 a flow of 3 cubic centimeters per hour
is obtained, and the effective resistance of the infusion system
would be about 6,000 milli-meters of mercury per cubic centimeter
per minute. Back pressure from the patient's body has no adverse
effect on the flow, and a flow of about 3 cubic centimeters per
hour will constantly flush the catheter to avoid any occlusion
therein, and will not interfere with or lessen the high quality of
the clinical recording of the central arterial pulse waveforms.
Obviously, to initially fill the system by way of such a small flow
through the resistance tube would require an objectionable amount
of time. To that end, means are provided in the passage 19 to
provide for a rapid flushing or quick filling of the entire system.
Such means comprise a valve 27 of resilient material, such as
rubber or synthetic rubber, which seats on the seat 21. The valve
has a cylindrical extension 28 extending from the valve body and
the outer end of this extension is seatingly engaged over an
inwardly extending nipple 29 on the cap 13. The length of the valve
body and extension 28 is slightly greater than the distance from
the valve seat to the cap 13 so that the valve is sealed against
its seat under its own pressure and blocks any bypassing of
solution through the passages 20 and 21. The valve is actuated
manually by means of a valve stem 30 extending from the valve body
through the extension and through the cap 13. When that valve stem
is manually pulled outwardly the valve is drawn away from the seat
21 opening the bypass and the extension 28 of the valve will assume
a corrugated effect as indicated at 31 in FIG. 5. The structure of
the valve makes it fail-safe, in that it cannot accidentally be
left in open position because when the stem 30 is released the
valve will automatically and forcefully close quickly. The valve
will also seat accurately because of a guiding projection 34
extending from the valve body into the smaller passage 20.
In use, the flow control device 1 is extremely efficient. Prior to
the insertion of the catheter in the patient's body, but after the
connection of the device 1 to the pressurized infusion solution
source, the stem of the valve 30 is pulled to open the valve and
flush out the system including the catheter so as to eliminate any
possible air bubbles. During such flushing infusion solution will
follow the line of arrows 32 through the bypass passageways and out
the fitting 6. The valve is closed after the initial flushing out,
but the catheter may be inserted in the patient's body while the
flow flushing infusion through the resistance tube 24, as indicated
by the arrows 33 in FIG. 2, continues. The fitting 9 is, of course,
connected to whatever indicating or recording means may be desired,
or to a pressure transducer for oscilloscopic observations, and the
catheter will be maintained patent throughout a long interval of
time. It is essential for assuring waveform quality to determine
the dynamic response of the entire system from time to time. This
is simply accomplished by opening the valve 27 and permit it to
quickly close. Such a rapid flush will cause what is termed a
square wave to appear on an oscilloscope and such will not mislead
the observer nor will it confuse any permanent record. The valve is
amply rapid in its action to perform that function.
During the use of the instant flow control and flushing device 1,
there can be no backflow because the blood pressure of the patient
is insufficient to force liquid through the capillary tube 24 in
the reverse direction. The device is extremely light in weight,
highly efficient as to its functioning, eliminates complicated
setups of apparatus, and makes it possible to monitor the central
arterial pulse waveform with its various derived parameters with
much greater ease, flexibility and accuracy than was heretofore
possible. Also, the device is sufficiently economical to warrant
its disposition along with the catheter after a single usage, if
such may be indicated, although the device may be repeatedly used,
sterilized if deemed necessary, if the conditions of the patients
permit.
* * * * *