U.S. patent number 3,889,677 [Application Number 05/417,124] was granted by the patent office on 1975-06-17 for self-contained fluid evacuator.
This patent grant is currently assigned to International Paper Company. Invention is credited to John R. Nehring.
United States Patent |
3,889,677 |
Nehring |
June 17, 1975 |
Self-contained fluid evacuator
Abstract
A self-contained wound evacuator is disclosed which provides a
substantially constant negative gauge pressure and which includes a
substantially rigid container and an air inflatable member within
the container, the container and inflatable member having a
combined configuration which avoids deformation of the inflatable
member by the container in at least one direction of expansion of
the inflatable member. Means are provided for inflating the
inflatable member and controlling the deflation thereof.
Inventors: |
Nehring; John R. (Woodcliff
Lake, NJ) |
Assignee: |
International Paper Company
(New York, NY)
|
Family
ID: |
23652673 |
Appl.
No.: |
05/417,124 |
Filed: |
November 19, 1973 |
Current U.S.
Class: |
604/142 |
Current CPC
Class: |
A61M
1/0011 (20130101); A61M 2209/088 (20130101); A61M
2209/082 (20130101) |
Current International
Class: |
A61M
1/00 (20060101); A61m 001/00 () |
Field of
Search: |
;128/276,277,278,297,302
;417/394 ;222/386.5 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Layton; Henry S.
Attorney, Agent or Firm: Finnegan, Henderson, Farabow &
Garrett
Claims
What is claimed is:
1. A self-contained fluid evacuator comprising a substantially
rigid, closed container having first and second openings
therethrough, said first opening being adapted to receive a
conduit, an inflatable member within said container, means for
inflating said inflatable member mounted on said container and
being in flow communication with the interior of said inflatable
member through said second opening, valve means responsive to the
difference in pressure between the pressure in the inflation means
and in the inflatable member such that said valve means enables
fluid to enter the inflatable member from the inflating means at a
higher rate than the fluid can leave the inflatable member, said
valve means restricting fluid from leaving the inflatable member at
a rate greater than a predetermined minimal flow rate.
2. A self-contained fluid evacuator as defined in claim 1 wherein
said valve means is a check valve having a bleed passageway
therethrough which permits restricted fluid flow through said valve
when said valve is closed.
3. A self-contained fluid evacuator as defined in claim 2 wherein
the inflating means is a manually operable pump having an outlet,
said inflatable member is a resilient bladder attached to the
outlet of said pump and said check valve is mounted across the pump
outlet.
4. A self-contained fluid evacuator as defined in claim 2 wherein
the inflating means is a resilient bulb having an air inlet and an
air outlet and wherein said inflatable member is a resilient
bladder mounted in flow communication with said air outlet, said
check valve being mounted across said air outlet to control the
flow of air between said bulb and said bladder.
5. A self-contained fluid evacuator comprising a substantially
rigid, closed container having a first port and a second port
therethrough, said first port adapted to receive a conduit, a
resilient inflatable member within said container, a resilient bulb
having an air inlet and an air outlet, said inflatable member being
mounted in flow communication with said air outlet, the exterior
surface of said bulb adjacent said air inlet being irregular to
ensure quick opening of the air inlet, on release of the bulb,
valve means responsive to the difference in pressure between the
prssure within the bulb and the pressure within the inflatable
member, said valve means enabling air to enter the inflatable
member from the bulb at a higher rate than air can leave the
inflatable member, said valve means restricting air from leaving
the inflatable member at a rate greater than a predetermined
minimal flow rate.
6. A self-contained fluid evacuator as defined in claim 5 wherein
said bulb includes a bead projecting from the exterior surface of
said bulb, said air inlet extending through said bead and said
bulb.
7. A self-contained fluid evacuator comprising:
a. a substantially rigid, closed container including a bottom wall,
first and second spaced apart opposed side walls, third and fourth
side walls joined to the opposite ends of said first and said
second side walls, said third and fourth side walls being spaced
apart a distance greater than the spacing between said first and
second walls;
b. a first port communicating with the interior of said
container;
c. an inflatable member within said container;
d. means for inflating said inflatable member;
e. means for deflating said inflatable member; and
f. said third and fourth side walls having a configuration which
substantially conforms to the shape of the natural unimpeded shape
of the adjacent portion of said inflatable member during inflation
of said inflatable member to a size substantially equal in volume
to the volume of the container effecting substantially constant
negative pressure at said first port during deflation of said
inflatable member.
8. A self-contained fluid evacuator comprising:
a. a substantially rigid, closed container including a bottom wall,
first and second spaced apart opposed side walls, third and fourth
side walls joined to the opposite ends of said first and second
side walls, said third and fourth side walls being spaced apart
further than said first and second side walls and having a
transverse outward curvature;
b. a first port communicating with the interior of said
container;
c. a resilient inflatable member with said container;
d. means for inflating said inflatable member; and
e. said third and fourth side walls having a radious of transverse
curvature which conforms to the shape of the natural unimpeded
shape of the adjacent portion of said inflatable member during
inflation of said inflatable member to a size substantially equal
in volume to the volume of the container effecting substantially
constant negative pressure at said first port during deflation of
said inflatable member.
9. A self-contained fluid evacuator as defined in claim 8 wherein
the radius of transverse curvature of said third and fourth walls
is W.sub.c /2, where W.sub.c equals the distance between said first
and second side walls.
10. A self-contained fluid evacuator as defined in claim 8 wherein
said first and second side walls are substantially flat.
11. A self-contained fluid evacuator as defined in claim 8 wherein
said bottom wall has a flat portion to facilitate standing the
container on a flat surface.
12. A self-contained fluid evacuator as defined in claim 9 wherein
said inflatable member is a substantially cylindrical bladder.
13. A self-contained fluid evacuator as defined in claim 8
including means formed on the interior surface of said container at
least a portion of which is adjacent to said first port to provide
a fluid-flow passageway thereto.
14. A self-contained fluid evacuator as defined in claim 8
including means on one of the interior surfaces of said container
and the exterior surface of said inflatable member for impeding
said inflatable member from adhering to the interior surface of
said container.
15. A self-contained fluid evacuator as defined in claim 8 wherein
said means for inflating said inflatable member is a manually
operated pump having an outlet, said inflatable member being
attached to the outlet of said pump and including valve means
responsive to the pressure differential between the interior of
said pump and the interior of said inflatable member, said valve
means enabling fluid to enter said inflatable member at a higher
rate than said valve enables fluid to leave said inflatable member
said valve means restricting fluid from leaving the inflatable
member at a rate greater than a predetermined minimal flow
rate.
16. A self-contained evacuator as defined in claim 15 wherein said
valve means is a check valve having a bleed passageway therethrough
which permits restricted fluid-flow through said check valve when
said check valve is closed.
17. A self-contained fluid evacuator as defined in claim 16 wherein
said pump is a resilient bulb having an air inlet therethrough.
18. A self-contained fluid evacuator comprising:
a. a substantially rigid, closed container including a bottom wall,
first and second spaced apart opposed side walls, third and fourth
side walls joined to the opposite ends of said first and second
side walls, said third and fourth side walls being spaced apart
further than said first and second side walls;
b. a first port communicating with the interior of said container
and adapted to receive a conduit;
c. a second port communicating with the interior of said
container;
d. a resilient inflatable member within said container;
e. means for inflating said inflatable member mounted on said
container and communicating with said inflatable member through
said second port;
f. said third and fourth side walls having an effective
configuration which conforms to the shape of the natural unimpeded
shape of the adjacent portion of said inflatable member during
inflation of said inflatable member effecting substantially
constant negative pressure of said first port during deflation of
said inflatable member.
19. A self-contained fluid evacuator as defined in claim 18
including air expulsion control means responsive to the inflation
of said inflatable member to terminate the expulsion of air from
said container during inflation of said inflatable member when said
inflatable member and said third and fourth side walls obtain a
predetermined relationship.
20. A self-contained fluid evacuator as defined in claim 19 wherein
the said second port is positioned such that said inflatable member
occludes said second port when said inflatable member and said
third and fourth side walls obtain a predetermined relationship
thereby terminating the explusion of air from said container, said
predetermined relationship being that further inflation of said
inflatable member without occlusion of said first port would
produce deformation of said inflatable bladder into a shape which
it would not take if said third and fourth walls were
nonexistent.
21. A self-contained fluid evacuator for removing fluids from a
patient including a substantially rigid container having spaced
apart first and second walls, and third and fourth walls spaced
apart further than said first and second walls, a first port
communicating with the interior of said container, an inflatable
member within said container, means for inflating said inflatable
member, means for deflating said inflatable member, said container
and said inflatable member having a combined configuration so that
said third and fourth walls conform in shape to the shape that the
natural unimpeded inflatable member obtains during inflation
effecting substantially constant negative pressure at said first
port during deflation of said inflatable member throughout said
predetermined operating range, the container and inflatable member
substantially have the following dimension ratios:
D.sub.f = diameter of bladder;
L.sub.f = length of bladder = between 3.0 - 4.0 D.sub.f
W.sub.c = width of container between said first and second walls
> 2.0D.sub.f ; and
R.sub.c = radius of transverse curvature of said third and fourth
walls = W.sub.c /2.
22. A fluid evacuator as defined in claim 21 wherein the largest
internal perimeter of said container is not greater than 22
D.sub.f.
Description
BACKGROUND
This invention relates to fluid evacuators and, more particularly,
to such evacuators which are disposable, portable and
self-contained.
The evacuation of fluids from the body of a patient is a common
medical practice. For example, the removal of fluids from the
vicinity of a wound has been found to aid faster and firmer healing
and reduce the likelihood of infection, fever and patient
discomfort. Fluid evacuation usually is accomplished through
gravity drainage, pressure dressings, compression bandages or by
negative pressure, the latter being preferred. Conventional
continuous closed wound suction devices include power driven vacuum
pumps, central suction systems or evacuated bottles. With the
exception of the evacuated bottle, each of these systems has many
disadvantages because of their cost, noise and restriction of
patient mobility resulting in the retardation of post operative
exercises, ambulation and rehabilitation.
Other suction wound drainage systems were developed to overcome
these disadvantages. Examples of more recent commonly used wound
evacuators are shown in U.S. Pat. Nos. 3,115,138 and 3,376,868. In
both of these devices the evacuator comprises an evacuation chamber
formed with resilient side walls which, after manual compression
and release, tend to return to their original extended position. In
so returning they provide a reduced pressure on the interior of the
container which, when attached to the patient by means of a tube,
effects evacuation of the wound. A potential hazard with such a
device is the possibility of accidental compression of the
container at a time when compression is undesirable. Accidental
compression when the device is attached to the patient could result
in the injection of air or previously removed fluids into the
patient. Another disadvantage with devices of this type is their
wide variation of negative pressure over the specified filling
range of the devices. When empty and fully compressed these devices
often provide a vacuum higher than necessary which might cause
lesions if tissue is sucked into or against the drainage tube. On
the other hand, as the container becomes filled with fluid the
vacuum is reduced often to a level where the vacuum is relatively
ineffective and clots or other debris may clog the drainage tube.
Wound evacuators presently commercially available have total
pressure variations of about 130% or more.
Accordingly, it is an objective of this invention to provide an
inexpensive, reliable, disposable, portable, self-contained vacuum
drainage device which evacuates fluids from wounds at relatively
constant pressure throughout the entire operating range of the
device.
It is another objective of this invention to provide an improved
self-contained wound evacuator which cannot be easily accidentally
pressurized thereby avoiding accidental injection of air or fluids
into a patient.
Additional objectives and advantages of the invention will be set
forth in part in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The objectives and advantages of the invention may be
realized and attained by means of the instrumentalities and
combinations particularly pointed out in the appended claims.
BRIEF DESCRIPTION OF THE INVENTION
To achieve the foregoing objectives and in accordance with the
purpose of the invention, as embodied and broadly described herein,
the self-contained fluid evacuator of this invention comprises a
substantially rigid, closed container having first and second
openings therethrough, the first opening being adapted to receive a
conduit, an inflatable member within the container, means for
inflating the inflatable member mounted on the container and being
in flow communication with the interior of the inflatable member
through the second opening. Valve means are provided which are
responsive to the difference in pressure between the pressure in
the inflation means and in the inflatable member such that the
valve means enable fluid to enter the inflatable member from the
inflating means at a higher rate than the fluid can leave the
inflatable member.
Preferably, the valve means is a check valve having a bleed
passageway therethrough which permits restricted fluid-flow through
the valve when the valve is closed. It is also preferred that the
inflating means is a manually operable pump having an outlet and
that the inflatable member is a resilient bladder attached to the
outlet of the pump with the check valve being mounted across the
pump outlet.
In accordance with the other embodiments of this invention, a fluid
evacuator comprises a substantially rigid, closed container
including a bottom wall, first and second spaced apart opposed side
walls, third and fourth side walls joined to the opposite ends of
the first and second side walls, the third and fourth side walls
being spaced apart a distance greater than the spacing between the
first and second sidewalls. The evacuator further includes a port
communicating with the interior of the container, an inflatable
member within the container, means for inflating the inflatable
member, means for deflating the inflatable member and wherein the
third and fourth side walls have a configuration which
substantially conforms to the shape of the natural unimpeded shape
of the adjacent portion of the inflatable member during inflation
of the inflatable member effecting substantially constant negative
pressure at the port during inflation of the inflatable member.
Preferably the configuration of the third and fourth side walls
either actually conform to the shape of the adjacent portion of the
inflatable member or effectively conform to that shape through
control of the pressure within the container.
The invention consists in the novel parts, constructions,
arrangements, combinations and improvements shown and described.
The accompanying drawings, which are incorporated in and constitute
a part of the specification, illustrate several embodiments of the
invention and, together with the description, serve to explain the
principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Of the drawings:
FIG. 1 is a perspective view of a wound evacuator formed in
accordance with this invention;
FIG. 2 is a sectional view taken along line 2--2 of FIG. 1;
FIG. 2A is a sectional view taken along line 2A--2A of FIG. 2;
FIG. 3 is a sectional view taken along line 3--3 of FIG. 1;
FIG. 4 is an enlarged, partially cutaway, perspective view of the
throat portion of a pressurized air source formed in accordance
with one form of this invention;
FIG. 5 is an empirical pressure vs. volume curve of cylindrical
latex bladder within a rigid container formed in accordance with
this invention;
FIG. 6 is an enlarged sectional view of a portion of the wall of
the wound evacuator container having a roughened interior
surface;
FIG. 7 is an enlarged sectional view of a portion of the wall of
the wound evacuator container having a coating on the interior
surface thereof; and
FIG. 8 is an enlarged, partially cutaway, perspective view of a
pressurized air source formed in accordance with a second form of
this invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Throughout the specification and claims, terms of orientation, such
as front, back, up and down are employed with respect to the
orientation shown in the drawings in order to simplify description
of the invention and are not intended to limit the location or
direction of the elements with respect to which these terms are
used.
In accordance with the invention, the wound evacuator includes a
housing and a first port serving as a fluid inlet port
communicating with the interior of the housing. The first port is
adapted to receive a tube designed to be placed internally within a
patient adjacent to a wound in order to remove fluids from the
vicinity of the wound. As here embodied, a self-contained wound
evacuator 10 is formed with a container 12 having opposed first and
second side walls 16, 18 (hereinafter called front and back walls),
opposed third and fourth side walls 20, 22 adjacent to the front
and back walls 16, 18 and a bottom wall 24. The container 12 is
relatively rigid, which means that it will not deform substantially
when it is subjected to the normal forces to which devices of this
sort are expected to be exposed. The container 12 is provided with
at least one opening, such as port 26, extending through and
communicating with the interior of the container 12. The port 26 is
adapted to receive flexible tubing 28 which is to be inserted into
a patient adjacent to the wound being treated. The tubing 28 is
conventional wound tubing which is non-toxic, non-pyrogenic, inert,
non-porous and non-degradable when used in its intended environment
and which has a plurality of openings 29 at its distal end.
While a single port 26 is sufficient for operation of the
self-contained wound evacuator 10 as described below, it is
preferred that a second opening or port 30 be provided to serve as
an outlet port to permit expulsion of air contained within the
container 12 and to permit removal of fluid which is received
within the container 12 during utilization of the wound evacuator
10. A suitable closure or cap 32 is provided to permit selective
opening and closing of the second port 30.
In accordance with the invention an air inflatable member is
mounted within the container 12 and means for inflating and
deflating the inflatable member are provided. As here embodied, the
inflatable member is a resilient bladder 40 having an opening at
one end 42 thereof. The means for inflating the bladder 40
preferably is a manually operated pump, such as a hand-operated
bulbous resilient member having a resiliency at least only slightly
greater than the resiliency of the bladder 40. Such a resilient
member is a rubber bulb 44 having an air inlet 46 and an open neck
48. The open end 42 of the bladder 40 is mounted in the neck 48 of
the bulb 44 so that air expelled through the bulb neck 48 is forced
to enter the bladder 40. While the bladder can be mounted directly
on the walls of the bulb neck 48, the embodiment illustrated in
FIG. 2 - 4 employs a plug 50 which is force-fitted within the neck
48, the plug 50 having an air passageway 52 axially therethrough.
The plug 50 is provided with an annular recess 54 to receive the
open end 42 of the bladder, the open end of the bladder being
trapped between the exterior of the plug 50 and the interior of the
bulb neck 48 to fixedly hold the bladder in place. The bulb 44
serves as the means to inflate the bladder 40 while the resiliency
of the bladder serves as the means for deflating the bladder.
While the bulb air inlet 46 is shown at the top of the bulb 44, it
could be located at any other position. For example, with a
container 12 as shown, locating the air inlet on the side has been
found particularly convenient because it is easier to block the air
inlet 46 with a finger or the heel of a hand. Furthermore, in order
to ensure quick opening of the inlet 46 on release of the bulb so
that the bulb quickly refills with air entering through the inlet
46 rather than being withdrawn from the bladder 40, an irregular
surface, such as a bead 51 is provided through which the inlet is
formed. The bead 51 prevents the finger or hand from sealing the
inlet during return of bulb to normal unsqueesed condition.
Further in accordance with the invention, valve means are provided
which are responsive to the difference in pressure between the bulb
44 and the bladder 40 so that when the pressure in the bulb exceeds
the pressure in the bladder, the valve means permit free flow of
air from the bulb to the bladder. However, when the pressure in the
bladder 40 exceeds the pressure in the bulb 44, the valve means
restrict the flow from the bladder to a predetermined minimal flow
rate.
In order to control the rate of deflation of the bladder 40, a slow
leak check valve, such as a flapper valve 56 having a small
diameter bleed vent 58 therethrough, is mounted on the bladder side
of plug 50. When the bulb 44 is squeezed, the flapper valve 56
permits air to be expelled freely from the bulb into the bladder 40
since the pressure differential across the flapper valve 56 during
such an operation forces the flapper valve away from the plug 50
thereby permitting air to flow easily into the bladder 40. However,
when the bladder is partially or totally inflated and the bulb 44
is returning from its squeezed or collapsed position to its normal
or expanded position, the pressure within the bladder is higher
than the pressure within the bulb and the flapper valve is forced
against the plug 50 thereby obturating the air passageway 52 except
for the vent 58 and preventing most of the air from leaving the
bladder 40. After the bladder is fully inflated and the wound
tubing 28 is inserted in a patient for evacuation, the small bleed
vent 58 permits air to be expelled from the bladder 40 through the
passageway 52.
To utilize the self-contained wound evacuator 10 of this invention
the distal end of the wound tubing 28 is inserted in the patient
before the proximal end is connected to the inlet port 26.
Alternatively, the wound tubing can be connected to the container
12 and closed by a conventional pinch clamp (not shown). The
closure 32 is removed from the outlet port 30 and the bladder 40 is
inflated by alternately squeezing and releasing the bulb 44. When
squeezing the bulb 44 the user covers the air inlet 46 to prevent
air from being expelled through the inlet, thereby requiring that
all air expelled from the bulb 44 passes through the air passageway
52 into the bladder 40. When the bulb is released air enters the
bulb through the inlet 46. The flapper valve 56 prevents a
substantial amount of air from flowing from the bladder 40 back
into the bulb 44. Continued pumping of the bulb inflates the
bladder 40 which forces the air within the container 12 out through
the outlet port 30 until such time as the inflated bladder
substantially fills the container 22. At that time, the proximal
end of the wound tubing 28 is connected to the inlet port 26 (or
the pinch clamp is opened) and the closure 32 is placed in the
outlet port 30 thereby closing the port. As the bladder deflates,
the air in the bladder passes outwardly through the bleed vent 58,
the air passageway 52 and the bulb air inlet 46. Deflation of the
bladder 40 produces a negative pressure at the port 26 which causes
fluids in the vicinity of the openings 29 at the distal end of the
wound tubing 28 to pass through the tubing into the container
12.
After the container 12 is filled with body fluid, the closure 32 is
removed from the port 30 and the container is emptied, either by
gravity feed (pouring the fluid out through the port) or by
attaching the port 30 to the low pressure side of a pump and
pumping the fluid out. The body fluid can also be expressed from
the container 12 by closing the pinch clamp and pumping the bulb
44. As the bladder inflates, it forces the body fluid out of the
container and, when empty the bladder is fully inflated and the
wound evacuator 10 is ready for reuse. If only a single port 26 is
used, the container is drained through the port 26.
In order to provide substantially constant negative pressure at the
inlet port 26 throughout the entire operating range of the wound
evacuator 10, and to utilize substantially the entire volume of the
container, the container 12 and the bladder 40 should have a
combined actual or effective configuration so that the container
does not physically interfere with or distort the inflation of the
bladder 40 in at least one direction of inflation. The terms
"constant pressure" and "substantially constant pressure" as used
throughout this specification and in the claims are intended for
use in a relative sense and do not imply absolute constant or
unchanging pressure. For example a total pressure variation of up
to about 20% - 30% throughout about 90% of the deflation range is
acceptable.
A low profile container 12 (relatively narrow from front 16 to back
18) is preferred because it can be more comfortably and
conveniently worn by a patient or attached to a support, such as a
bed or chair. These advantages can be obtained if the front and
back walls 16, 18 are substantially flat and relatively closely
spaced apart. Substantially flat front and back walls are walls
which either are truly flat or which have a radius of curvature
much greater than the radius of the bladder 40 when the bladder
contacts the front and back walls 16, 18. Where a substantial
vacuum is to be induced in the container 12, it may be preferred to
form the front and back walls 16, 18 with a shallow outward
curvature (large radius of curvature) to provide structural
strength without adversely affecting the low profile of the
container.
It also is desirable to be able to stand the container 12
vertically on a flat surface and, therefore, the bottom wall 24 of
the container preferably should be flat.
It has been found that satisfactorily constant pressure can be
obtained with a cylindrical bladder when the bladder is inflated in
a low profile container ("flat" front and back walls) if the side
walls 20, 22 adjacent to the "flat" front and back walls 16, 18
actually or effectively conform to the shape of the inflated
bladder 40.
In order to actually conform the side walls 20, 22 to the bladder
shape, the side walls 20, 22, are formed with a transverse outward
curvature (from front wall to back wall) as can be seen in FIG. 2A.
Preferably, the radius of transverse curvature is W.sub.c /2 where
W.sub.c is the distance between the front and back walls 16, 18. It
also is desirable to avoid corners at the top and bottom of the
side walls and, therefore, rounded upper and lower ends are formed
or, alternatively, the side walls 20, 22 can be formed with a
longitudinal curvature from top to bottom as can be seen in FIGS. 1
and 2.
While satisfactory results can be obatined over a relatively wide
range of front-to-back wall spacing, more consistently reliable
results and more useful filling volume for a given container size
while maintaining relatively constant pressure can be obtained if
the front and back walls 16, 18 are spaced apart a distance greater
than twice the diameter of the uninflated bladder (W.sub.c >
2D.sub.f).
In accordance with this invention, instead of actually conforming
the sidewalls 20, 22 to the inflated bladder shape, the side walls
20, 22 can be made to "effectively" conform to the bladder shape by
controlling the pressure within the container. More specifically,
as the bladder 40 is inflated, the air inside the container 12 is
expelled through the outlet port 30 until, after the bladder
contacts the side walls 20, 22 and continues to inflate, it reaches
a position within the container wherein the bladder is about to be
forced into a shape which is different from what it would be if the
side walls 20, 22 were nonexistent. At that time, the outlet port
is occluded to prevent further expulsion of air from the container
12. Any further pressurization of the bladder 40 by pumping the
bulb 44 results in a concommitant increase in pressure inside the
container since the air cannot escape. Upon release of the bulb 40
the pressure in the bladder and container rapidly drops to
atmospheric pressure by virtue of the air in the bladder 40
escaping through the check valve bleed port 58 and bulb air inlet
46 to the atmosphere. This concept of pressure equalization in the
container and bladder when the bladder is about to be deformed into
a shape which adversely affects a constant pressure curve is
referred to throughout the specification and claims as "effective"
conformation of the container shape with the bladder shape.
As here embodied, the outlet port 30 is occluded by the bladder 40
when it reaches its predetermined shape. This is effected by
forming the outlet port 30 with an inwardly extending protuberance
31 which projects inwardly an amount calculated to bring it in
contact with the bladder at the appropriate bladder inflation
level. The outlet port 30 and protuberance 31 can be formed as an
integral part of the container 12 or it can be formed by a separate
member mounted in an opening formed in the container 12. When this
outlet port occluding concept is employed the shape of the
container 12 is not critical.
With respect to a container which actually conforms to the bladder
shape and which has a satisfactory low profile, substantially
constant negative pressure during deflation of a bladder has been
obtained with a container and latex cylindrical bladder having the
shapes generally shown in FIGS. 2, 2A and 3 and having the
following dimension ratios.
D.sub.f = diameter of bladder;
L.sub.f = length of bladder = 3.0 - 4.0 D.sub.f
W.sub.c = width of container = 2.5 D.sub.f
R.sub.c = radius of transverse curvature of side walls = W.sub.c
/2
D.sub.c = length of container = 1.8L.sub.f
P.sub.c = container interior perimeter < 22D.sub.f
The bladder thickness (F.sub.t) together with the characteristics
of the bladder material (actually, the modulus of elasticity)
determines the vacuum level produced within the container. For a
latex bladder, a bladder thickness of 0.01D.sub.f has been found to
produce a constant negative pressure in the above described
container of approximately 30 inches of water (see FIG. 5). The
container perimeter/bladder diameter ratio is calculated to provide
not greater than a seven fold increase in bladder diameter which
has been found to be within a safe stress range for a latex
bladder. For a convenient and comfortable evacuator profile, the
bulb diameter (D.sub.b) should be approximately equal to the width
of the container (D.sub.b = W.sub.c).
These ratios provide a self-contained wound evacuator having
satisfactory performance by providing relatively constant pressure
in a desired pressure range (-29 to -35 inches of water) and a safe
stress for a bladder made of natural latex. The bladder can also be
formed from any synthetic elastomer, such as polyurethane. FIG. 5
is a pressure vs. volume curve of a latex bladder having a
three-fourth inch uninflated diameter, a 2 1/2 inches free length
and a 0.012 inch wall thickness which was inflated in a rigid
container having dimensions substantially in accordance with the
above dimension ratios. As can be seen, the vacuum within the
container remains between 31.3 inches of water at a bladder volume
of about 4.5 times the uninflated bladder volume (4.5V.sub.1) at
which time the bladder first touched the relatively close container
walls (e.g. 16, 18) and 29 inches of water. The pressure remains at
this level throughout the operating range of the wound evacuator
and satisfactory results have been obtained at bladder inflations
of over 30V.sub.1. The total pressure variation over this range was
only about 8% of the minimum pressure within the range (29 inches
of water). In connection with wound evacuators, the pressure curve
of FIG. 5 is considered to have a substantially constant
pressure.
The container 12 can be formed of any suitable material such as a
moldable plastic, for example, polyvinylchoride. The shape of the
container lends itself to being blow molded; however, it could be
formed other ways, such as by injection molding. At least a portion
59 of one of the flat side walls 16, 18 preferably is transparent
and a calibrated graduated scale 60 is placed along the side
thereof in order to enable volumetric measurement of the amount of
fluid contained within the evacuator 10. The container 12 also is
provided with mounting tabs 61 to which a belt 62 or other support
means is attached to facilitate hanging the wound evacuator 10 on a
bed or chair or to enable the evacuator to be worn by an ambulatory
patient.
Further in accordance with the invention, it is desirable to
provide means for preventing accidental sealing of a portion of the
container from the outlet port 30, especially during evacuation of
fluids within the container 12 which were removed from the patient.
One means for avoiding this blockage is to provide a recess 63 in
the interior surface of the container walls, particularly in the
area leading to and adjacent to the outlet port 30. Such a recess
63 assures the existence of a fluid flow passageway from the
interior of the container 12 to the outlet port 30. Also, the
interior surface of the container walls can be roughened, such as
by injection molding the container, to accomplish the same results
(FIG. 6).
Another means for preventing blockage of the outlet port is to
provide a surface coating 64 on the interior surface of the
container 12, (FIG. 7) or on the exterior surface of the bladder
40, which will lessen adherence of the bladder to the interior of
the container. For example, it has been found that chlorinating the
surface of a latex bladder or coating the interior surface of a
container with a conventional commercially available medical
silicon successfully lessens adherence of the bladder to the
container walls. Reduction of the adherence of the bladder 40 to
the container walls also is of substantial assistance in
maintaining the negative pressure substantially constant.
In order to operate the resilient bulb 44 illustrated in FIGS. 2
and 3, it is necessary for the user to place his finger over the
air inlet 46 while squeezing the bulb 44 to prevent air from
escaping through the air inlet 46 and thereby forcing that air into
the inflatable bladder 40. The combined operation of simultaneously
closing the air inlet 46 and squeezing the bulb 44 is a safety
feature to prevent accidental injection of air or previously
removed fluid into the patient since it is unlikely that both steps
will accidentally be performed. Furthermore, the relative rigidity
of the container 12 also precludes accidental pressurization of the
contents of the container 12 by pressing on the sides of the
container. Consequently the structure provided by this invention
reasonably assures that fluid or air will not be accidentally
injected into the patient by accidental pressuring of the
container.
With some sacrifice in safety but to simplify the utilization of
the wound evacuator 10, another form of resilient bulb such as bulb
66, illustrated in FIG. 8, may be used which eliminates the need
for the operator to cover the air inlet in order to effectively
inflate the bladder 40. An automatically operating check valve,
such as a flapper valve 68, is located on the interior surface of
the bulb 66 to normally cover the air inlet 70 and is provided with
a small diameter bleed vent 72. In order to inflate the bladder 40
the user squeezes the bulb 66 thereby increasing the pressure
within the bulb. This increased pressure forces the flapper valve
68 against the air inlet 70 restricting the amount of air passing
through the air inlet to be that small amount which can pass
through the bleed vent 72. The pressure differential across the
flapper valve 74 between the bulb 66 and the bladder 40 causes the
flapper valve 74 to open and permit the air to freely enter the
bladder 40. Upon release of the bulb 66, the resiliency of the bulb
returns it to its original position increasing the volume within
the bulb resulting in a reduced pressure within the bulb. This
produces a pressure differential across the flapper valve 68
causing the flapper valve to open and allowing atmospheric air to
enter the bulb through the inlet 70 while closing the flapper valve
74 to prevent escape of air from the bladder. After the bladder 40
is inflated sufficiently, and the bulb returns to its normal
position, air leaving the bladder 40 flows through the bleed vent
76 in the flapper valve 74, into the bulb 66 and through the bleed
vent 72 in the flapper valve 68 and to the atmosphere.
To further protect against accidental ejection of air or liquid
through the port 26, a check valve, such as a flapper valve 80, can
be mounted adjacent to the port 26 for closing the port 26 upon
pressurization of the container, such as if the bulb 44 (or bulb
66) is accidently squeezed. Of course, the check valve 80 does not
interfere with the flow of fluid into the container 12 through the
wound tubing 28. Furthermore, the port 26 can be formed such that
the bladder 40 occludes the port 26 when the bladder is inflated to
its intended volume to further ensure against leakage through the
port 26 to the patient.
It is also contemplated that a bulb can be used which has the same
capacity as a fully inflated bladder. In other words, a single
compression of the bulb would be sufficient to complete the
inflation of the bladder. With a bulb of this size there is no
requirement for an air inlet 46 and a closed system can be formed
wherein air from the bulb fills the bladder and, when the bladder
deflates, the air returns to the bulb for subsequent use. In such a
closed system, a supple bulb, less resilient than the bladder, is
used.
SUMMARY
It can be seen that the fluid evacuator of this invention is
completely self-contained,, portable and totally reliable. It is
also easy and inexpensive to manufacture and, therefore,
disposable. Of considerable significance are the safety features
which prevent the fluid evacuator from being accidentally
pressurized in a manner which will inject air or previously removed
fluids back to the patient. Furthermore, the negative pressure
formed at the inlet port which causes the forced removal of fluid
from the patient is substantially constant thereby, (a) avoiding
potential injury to the patient which could occur if the negative
pressure is too high and (b) ensuring efficient operation of the
evacuator throughout the entire operational range of the wound
evacuator.
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