U.S. patent number 3,559,644 [Application Number 04/690,440] was granted by the patent office on 1971-02-02 for liquid infusion apparatus.
This patent grant is currently assigned to N/A. Invention is credited to Robert F. Shaw, Paul E. Stoft.
United States Patent |
3,559,644 |
Stoft , et al. |
February 2, 1971 |
LIQUID INFUSION APPARATUS
Abstract
Liquid infusion apparatus provides reliable administration of
liquids and blood transfusions into the body (intravenous,
intraarterial or subcutaneous) at a preset and regulated rate in a
convenient, inexpensive and completely safe manner. The apparatus
includes liquid pumping an valving mechanisms and gas relief means
which prevent both the back flow of liquid into the liquid
reservoir and the injection of air into the blood stream of the
patient.
Inventors: |
Stoft; Paul E. (Menlo Park,
CA), Shaw; Robert F. (San Francisco, CA) |
Assignee: |
N/A (N/A)
|
Family
ID: |
24772473 |
Appl.
No.: |
04/690,440 |
Filed: |
December 14, 1967 |
Current U.S.
Class: |
604/123; 222/380;
417/240; 604/151; 222/203; 222/644; 417/435; 604/153 |
Current CPC
Class: |
A61M
5/14216 (20130101) |
Current International
Class: |
A61M
5/142 (20060101); A61m 005/00 () |
Field of
Search: |
;128/213--216,274,273
;103/203 ;222/76,202,203,380 ;23/258.5 ;417/240,435 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Berkow Med. Jour. & Record - July 1925 p. 529.
|
Primary Examiner: Truluck; Dalton L.
Claims
We claim:
1. Liquid infusion apparatus for use with source means containing a
liquid to be administered to a patient, the apparatus
comprising:
a chamber for confining a volume of fluid;
compressor means coupled to said chamber and having a movable
boundary wall disposed to communicate with fluid within said
chamber for changing the volume of fluid within said chamber at a
selected rate in response to movement of said boundary wall;
outlet valve means coupled to said chamber for providing outlet
flow of fluid therethrough only for values of fluid pressure
exerted thereon above a selected value of bias pressure;
conduit means coupled to said outlet valve means for supplying the
outlet flow of fluid to a patient; and
fluid inlet means connecting said source means with said chamber,
said fluid inlet means consisting only of an aperture in the upper
portion of said chamber for permitting bilateral flow of fluid
therethrough between said source means and said chamber in response
to movement of said secondary wall, the size of said aperture
introduces less resistance to flow therethrough of gas than of
liquid:
a. the selected change of volume of fluid within said chamber in
response to movement of said boundary wall with said chamber filled
with liquid exceeds the back flow of liquid through said aperture
for producing a buildup of pressure within said chamber to overcome
said selected value of bias pressure of said outlet valve and
permit outlet flow of liquid through said conduit means to a
patient, and
b. the selected change of volume of fluid within said chamber in
response to movement of said boundary wall with gas enclosed in the
upper portion of said chamber in the region of said aperture is
less than the backflow of the gas through said aperture for
preventing buildup of pressure within said chamber adequate to
overcome said selected value of bias pressure of said outlet
valve.
2. Liquid infusion apparatus for use with source means containing a
liquid to be administered to a patient, the apparatus
comprising:
a chamber for confining a volume of fluid and including converging
walls forming an internal region of decreasing cross-sectional area
with length of the chamber for focusing a pressure wave at an
outlet disposed near the end of said chamber of smallest
cross-sectional area;
outlet valve means disposed at said outlet and coupled to said
chamber for providing outlet flow of liquid therethrough only for
values of pressure exerted thereon above a selected value;
fluid inlet means connected for receiving liquid from the source
means and coupled to said chamber for supplying fluid therethrough
to said chamber;
transducer means disposed with respect to said chamber near the end
thereof of largest cross-sectional area for increasing the fluid
pressure in the internal region of said chamber to a value above
said selected value for producing outflow of liquid through said
outlet valve means in response to an electrical signal applied to
said transducer means;
gas relief means including an aperture of selected cross section
disposed at the fluid inlet in a wall of said chamber near the end
thereof of largest cross-sectional area; and
conduit means coupled to said outlet valve means for supplying the
outlet flow of liquid to a patient.
3. Liquid infusion apparatus as in claim 2 wherein:
said transducer means is a piezoelectric element arranged on a wall
of said chamber disposed near the end thereof of largest cross
section to displace a portion of said wall in response to
electrical signal applied to said element for producing a pressure
increase in the infusion liquid within said chamber near the end
thereof of smallest cross section in excess of said selected
value.
4. Liquid infusion apparatus as in claim 3 wherein:
said chamber is conically shaped;
said transducer means includes a toroidally shaped piezoelectric
element disposed on the upper wall of said chamber remote from said
outlet valve for producing a pressure wave in infusion liquid
within said chamber in response to electrical signal applied to
said piezoelectric element, whereby the pressure wave is confined
and focused by the conically shaped chamber to exert liquid
pressure on said outlet valve in excess of said selected value;
and
said aperture is disposed in said upper wall of said chamber within
the inner area of said toroidally shaped piezoelectric element.
Description
BACKGROUND OF THE INVENTION
Conventional infusion apparatus for administering fluids to a
patient intravenously, intraarterially, or the like, commonly
includes a fluid reservoir, an infusion needle or catheter
connected to the reservoir by a drip chamber and a tubing clamp
positioned along the length of the plastic tubing. The fluid
reservoir is typically elevated well above the patient to provide
fluid pressure and the fluid flow rate, observed in the fluid drip
chamber as the number of drops per unit time, is set by squeezing
the plastic tube a selected amount in the tubing clamp. The
disadvantages encountered in conventional infusion apparatus of
this type are that the fluid flow rate may decrease and stop due to
formation of blood clots in or about the infusion needle, due to
variations in resistance to flow through the needle or catheter
caused by patient motion or change of bodily position and also due
to variation in resistance to flow through the tubing within the
tubing clamp caused by the cold flow of the plastic material
forming the walls of the tubing within the tubing clamp. These
effects tend to vary the flow rate of fluid administered to the
patient, thereby requiring frequent inspection and readjustment of
the apparatus.
SUMMARY OF THE INVENTION
The apparatus of the present invention overcomes these
disadvantages by providing liquid-pumping means which provides the
required pressure and flow rates independent of variations in the
resistance to flow encountered. The liquid-pumping means includes
apparatus for introducing sufficiently large pressure pulse in the
liquid within a storage chamber to overcome the resistance to flow
through an outlet valve and thereby provide the selected liquid
infusion pressure and flow rate. The liquid pressure pulses may be
generated by a mechanically actuated plunger or may be generated by
an electromechanical element which is electrically pulsed to pump
the infusion liquid from a storage chamber. In these and other
embodiments of the invention, gas relief means are coupled to the
storage chamber for preventing the buildup of liquid pressure
within the chamber sufficient to produce liquid flow through the
outlet valve when the chamber is not filled entirely with the
infusion liquid.
DESCRIPTION OF THE DRAWING
FIG. 1 is a side view of the liquid infusion apparatus according to
one embodiment of the present invention showing a cross section of
the disposable pumping subassembly;
FIGS. 2 and 3 show alternate embodiments of the flotation of valve
of FIG. 1; and
FIG. 4 is a pictorial view of liquid infusion apparatus according
to another embodiment of the present invention which includes an
electromechanical pumping element.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIG. 1 the liquid infusion apparatus includes a
conventional drip chamber 9 connected to receive the infusion
liquid from reservoir 11. Liquid from the drip chamber 9 is
supplied to the storage chamber 13 of the pumping means 15 through
the inlet valve 17 which includes a ball or other valve element
that floats into closed position in the infusion liquid within the
chamber 13.
A pump cylinder 19 with a slidable piston 21 therewithin is
connected to receive the liquid in the chamber 13 and an outlet
valve 23 is coupled to the chamber 13 to control the outflow of
liquid from the chamber. A suitable length of flexible tubing 25
connects the outlet end of chamber 13 to the infusion needle or
catheter 27. Actuating means 29 for the piston 21 may include a
spring motor or electric motor 31 coupled to the piston 21 through
a connecting rod 32 which is pivotally attached to the crank arm 33
on the rotatable shaft of the motor 31 at a selected distance from
the shaft. Of course, the actuating means may also include other
suitable prime movers such as electrical solenoids or the like for
reciprocatingly actuating the piston 21 within the cylinder 19.
In operation, the actuating means 29 moves the piston 21 within the
cylinder 19 in a direction away from the chamber 13 to draw fluid
from the chamber 13 into the cylinder 19. This causes fluid to be
drawn from the drip chamber 9 past the inlet valve 17 into the
chamber 13 and cylinder 19 while the outlet valve 23 remains
closed. When the piston 21 is moved toward the chamber 13 by the
actuating means 29, the increase in liquid pressure produced
thereby aids in closing the inlet valve 17 and opens the outlet
valve 23 when the liquid pressure in chamber 13 overcomes the
slight bias against outflow through the outlet valve 23 produced by
the spring 24. This spring bias against outflow through the outlet
valve 23 assures that liquid does not flow to the needle under the
pressure head provided by the elevation of the reservoir above the
outlet valve. A selected amount of liquid thus flows past the
outlet valve 23 and through the tubing 25 to the needle 27 only
upon the return stroke of piston 21. For a cylinder 19 of given
internal diameter, the amount of liquid supplied to the needle 27
may thus be regulated by altering the stroke of the piston, for
example, by altering the position along crank arm 33 of the
connecting rod 32 coupling to the crank arm or by altering the
rotational speed of the motor 31.
The inlet valve 17 is selected to displace on amount of the
infusion liquid which weighs more than the valve element 17 so that
the element is urged into the closed position by the buoyant force
thus produced. Thus, if air is drawn into the chamber 13 and the
liquid level drops, for example, when the reservoir 11 and drip
chamber 9 are empty, the floating element 17 is no longer urged
into closed position and thereby provides a gas relief opening back
to the reservoir and drip chamber for air within the chamber 13.
The return stroke of piston 21 thus is unable to create sufficient
liquid pressure in chamber 13 to overcome the bias against outflow
provided by outlet valve 23 and thus no air can be administered to
the patient. Other embodiments of floating inlet valve means
according to the present invention are shown in FIGS. 2 and 3. In
these embodiments, the floating element 18 may actuate a
nonfloating valve 20 or may be the valve element 18 which forms the
sealing engagement with the upper walls of the chamber. In each of
these embodiments, when the liquid level in the chamber 13 drops
due to air being drawn into the chamber, the floating inlet valve
is no longer buoyed into closed position and the air within the
chamber is thus vented back toward the reservoir 11 so that liquid
pressure cannot build up within the chamber 13 to overcome the bias
against liquid outflow through outlet valve 23.
Referring now to FIG. 4, there is shown another embodiment of the
present infusion apparatus in which the liquid pressure to overcome
the bias against outflow of liquid through outlet valve means 35 is
provided by a mechanical or electromechanical element 37. This
element 37 is disposed on the top 38 of a conical or nozzlelike
chamber 39 remote from the outlet means 35 positioned at the apex
41 of the conical chamber 39 for mechanically displacing the top 38
in response to an applied electrical signal. The element 37 may
thus be a solenoid having a movable armature coupled to the surface
38 or, preferably, may be a piezoelectric element. A fluid conduit
including tube 43 and drip chamber 9 connects the reservoir 11 to
the internal region of the conical chamber 39 through an aperture
36 in the top surface 38 of the chamber 39. The element 37 may have
a toroidal shape to facilitate symmetrical location of the inlet
aperture 36 and fluid conduit 43 substantially at the center of the
top surface 38. Suitable excitation signals 45 are applied to the
element 37 by the timer and pulser 47. The top surface 38 of the
conical chamber 39 is flexible in the direction along the central
axis of the conical symmetry of the chamber 39 to enable the
mechanical displacement produced by the element 37 to establish a
pressure pulse in the liquid within the chamber 39. The mounting
bracket 49 which supports the chamber 39 also supports the element
37 in engagement with the top surface 38 so that longitudinal
extension of the element 37 in response to excitation signal
applied thereto from timer and pulser 47 are coupled to the fluid
within the chamber 39 through the diaphragmlike or plungerlike
movement of top surface 38. The conduit 43, drip chamber 9, chamber
39, outlet valve 35 and the tubing 25 and needle 27 may all be
conveniently disposable and replaceable with similar presterilized
replacement parts.
In operation, the element 37 displaces the top surface 38 upward in
response to an excitation signal of sufficient amplitude and proper
polarity applied to the element 37 by the timer and pulser 47. This
upward movement of the top surface 38 with respect to the chamber
39 increases the internal volume of the chamber 39. The drop in
internal pressure produced thereby causes liquid to be drawn
through the aperture 36 in the top surface 38 from the chamber 39.
OUtlet valve 35 remains closed so no liquid is administered to the
patient during this phase of operation. When the polarity of the
drive signal applied to the element 37 from timer and pulser 47
reverses, the top surface 38 is suddenly driven downward. This
causes a pressure wavefront to propagate through the liquid in
chamber 39 in a focused or converging direction predominantly
toward the outlet valve 35 at the apex end of chamber 39. This
pressure wave momentarily overcomes the bias against outflow
through valve 35 and expels a small amount of liquid into the tube
25 and out through needle 27. If this pressure wavefront is
suitably focused there will be no expulsion of liquid from the
chamber 39 back toward the drip chamber 9 through the small
aperture 36.
If, however, focusing of this pressure wavefront is inadequate to
assure unidirectional propagation of the pressure pulse, then a
small amount of liquid may be expelled from the chamber 39 back
toward the drip chamber 9 through the small aperture 36. However,
since the element 37 may produce short pulses and since the
aperture 36 may be very small in diameter, such backflow is
negligibly small and produces no deleterious effects. Thus, the
flow rate of infusion liquid into a patient may thus be regulated
by setting the pulse amplitude and repetition rate of signals 45
applied to the element 37 by the timer and pulser 47. This latter
element 47 may include a conventional multivibrator circuit
arranged to operate from a power source 46 to provide the necessary
driving signals 45 at variable pulse amplitude and repetition
rate.
The embodiment of FIG. 4 also includes gas relief means which
prevents infusion of air when the reservoir 11 is empty. If liquid
is expelled from chamber 39 to an extent that air is present in the
chamber, then the compressibility of the air and the gas relief
opening at aperture 36 which presents negligible resistance to gas
flow prevent the movement of element 37 and surface 38 from
establishing a sufficient pressure wave 42 within the remaining
liquid in the chamber 39 to overcome the bias against outflow
through valve 35.
Therefore, the apparatus of the present invention may be left
unattended without risk of administering air into a patient when
the reservoir is empty and without risk of the liquid infusion rate
changing due to such factors as the formation of blood clots about
the needle. Also, if blood clots tend to develop about the needle
tending to block the infusion of liquid, the liquid pressure within
the tubing and needle builds up with each pumping phase until the
blockage is cleared by the liquid under pressure.
* * * * *