U.S. patent number RE32,940 [Application Number 07/194,519] was granted by the patent office on 1989-06-06 for medical appliance.
This patent grant is currently assigned to Electro-Biology, Inc.. Invention is credited to Roger H. Fox, Arthur M. N. Gardner.
United States Patent |
RE32,940 |
Gardner , et al. |
June 6, 1989 |
**Please see images for:
( Certificate of Correction ) ( Reexamination Certificate
) ** |
Medical appliance
Abstract
The invention contemplates a non-invasive technique and
apparatus for artificially stimulating the venous-return flow of
blood from the foot by inducing sharply pulsed squeezing or
necking-down of the vessels of the venous-pump mechanism within the
foot. The sitmulation results from transient flattening of the
plantar arch, in that an induced transient spread of the heel with
respect to the ball of the foot stretches, and therefore necks-down
involved blood vessels; stimulation also results from such a
squeeze of the plantar-arch region as to concurrently squeeze the
involved blood vessels. Cyclically inflatable devices, local to the
foot-pump region, are disclosed for inducing either or both of the
indicated actions.
Inventors: |
Gardner; Arthur M. N.
(Ipplepen, GB2), Fox; Roger H. (Totnes,
GB2) |
Assignee: |
Electro-Biology, Inc.
(Parsippany, NJ)
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Family
ID: |
26286453 |
Appl.
No.: |
07/194,519 |
Filed: |
May 16, 1988 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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763686 |
Aug 8, 1985 |
4614180 |
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621499 |
Jun 18, 1984 |
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751150 |
Jul 2, 1985 |
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621499 |
Jun 18, 1984 |
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Reissue of: |
794443 |
Nov 4, 1985 |
4614179 |
Sep 30, 1986 |
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Foreign Application Priority Data
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Jun 22, 1983 [GB] |
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8316959 |
Nov 11, 1983 [GB] |
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8330138 |
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Current U.S.
Class: |
601/152;
128/DIG.20 |
Current CPC
Class: |
A61H
9/0078 (20130101); A61H 2205/12 (20130101) |
Current International
Class: |
A61H
23/04 (20060101); A61H 007/00 () |
Field of
Search: |
;128/64,25B,DIG.20,40 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
"The Venous Pump of the Human Foot-Preliminary Report"; Bristol
Medico-Chirugical Journal; Gardner and Fox; pp. 109-112; Jul.
1983..
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Primary Examiner: Burr; Edgar S.
Assistant Examiner: Lamb; Tonya
Attorney, Agent or Firm: Hopgood, Calimafde, Kalil,
Blaustein & Judlowe
Parent Case Text
RELATED CASES
This application is a continuation of a first copending application
Ser. No. 763,686, filed Aug. 8, 1985, and said copending
application is a continuation-in-part of our originally filed
application Ser. No. 621,499, filed June 18, 1984; this application
is also a continuation-in-part of a second copending application
Ser. No. 751,150, filed July 2, 1985, now abandoned, and said
second copending application is a division of said original
application Ser. No. 621,499, filed June 18, 1984,.Iadd., which
claimed priority from United Kingdom application No. 8316959, filed
June 22, 1983 and United Kingdom application 8330138, filed Nov.
11, 1983. .Iaddend.
Claims
What is claimed is:
1. The method of promoting venous pump action in the leg of a
living body, which method comprises simultaneously applying (a)
upward and spreading force at longitudinally spaced plantar regions
of the sole of the foot, said regions being essentially limited by
and between the ball and heel of the foot and (b) downward force at
the region of the midtarsal joint, said forces being applied in a
cyclical pattern of relatively rapid increase to a predetermined
upper limit before relaxation for a period substantially exceeding
the application time, whereby the arch of the foot is caused to
flatten periodically and thus to stretch and neck down the internal
local sectional area of the veins of the lateral plantar complex,
with resulting venous-pump action.
2. The method of promoting venous pump action in the leg of a
living body, which method comprises simultaneously applying
vertically opposed squeezing forces between the plantar region of
the sole of the foot and the region of the midtarsal joint, said
forces being applied in a cyclical pattern of relatively rapid
increase to a predetermined upper limit before relaxation for a
period substantially exceeding the application time, thereby to
stimulate the venous pump mechanism of the foot.
3. The method of promoting venous pump action in the leg of a
living body, which method comprises establishing a peripherally
continuous confinement of the midtarsal and plantar regions of a
foot, and shrinking the confinement in a cyclical pattern of
relatively rapid short-duration shrink action followed by a
relatively long-duration release from shrink action.
4. The method of promoting venous pump action in the leg of a human
body, which method comprises the steps of (a) applying a
circumferential tie to the foot at the region of the midtarsal
joint, (b) applying upward and spreading force between the
circumferential tie and the foot at longitudinally spaced plantar
regions of the sole of the foot, said plantar regions being
essentially limited by and between the ball and heel of the foot,
(c) relaxing said force for a period of time, and (d) cyclically
repeating the force-application and the force-relaxation steps in a
pattern wherein force-application is relatively rapid, whereby the
arch of the foot is periodically caused to flatten and thus to
stretch and neck down the internal sectional area of veins of the
plantar complex, with resulting venous-pump action.
5. The method of claim 4, in which the circumferential tie is
established by wrapped application of a cloth sling.
6. The method of claim 4, in which the circumferential tie is
established by application of an orthopedic cast.
7. The method of claim 4, in which the circumferential tie is short
of enveloping the toes of the foot.
8. The method of claim 4, in which the force application is
developed in two seconds or less.
9. The method of claim 4, in which the circumferential tie is
established by securing a slipper to the foot.
10. The method of claim 4, in which said force is pneumatically
applied.
11. The method of promoting venous pump action in the leg of a
living body, which method comprises the steps of (a) applying
vertically opposed squeezing forces to the foot at the region of
the midtarsal joint and at the plantar region therebeneath, (b)
relaxing said forces for a period of time, and (c) cyclically
repeating the force-application and the force-relaxation steps in a
pattern wherein force-application is relatively rapid, whereby the
veins of the plantar complex are periodically compressed, with
resulting venous-pump action.
12. The method of promoting venous pump action in the leg of a
human body, which method comprises the steps of (a) establishing a
peripherally continuous plantar confinement of the foot at the
region of the midtarsal joint, (b) shrinking the confinement, (c)
relaxing the shrinking confinement, and (c) cyclically repeating
the shrinkage and relaxing steps in a pattern wherein the shrinkage
step is relatively rapid, whereby the veins of the plantar complex
are periodically compressed, with resulting venous-pump action.
13. The method of promoting venous pump action in the leg of a
human body, which comprises the steps of (a) selecting a relatively
stiff sole member of length to overly the ball and heel of the foot
and to span the plantar arch, (b) securing the same to the foot
with referencing support at the ball and heel, (c) applying upward
force between the sole member and the plantar arch, (d) relaxing
said force for a period of time, and (e) cyclically repeating the
force-application and the force-relaxation steps in a pattern
wherein force-application is relatively rapid, whereby the internal
sectional area of the veins of the plantar complex is periodically
reduced, with resulting venous pump action.
14. The method of claim 5 or claim 11 or claim 12 or claim 13, in
which the force application is developed in one second or less.
15. The method of claim 5 or claim 11 or claim 12 or claim 13, in
which the period of force-relaxation is in the range of 10 to 60
seconds.
16. The method of claim 5 or claim 11 or claim 12 or claim 13, in
which the force-application step is pneumatic and to a peak
pressure of at least 200-mm Hg.
Description
BACKGROUND OF THE INVENTION
The invention relates to a medical appliance, and particularly to a
medical appliance for applying pressure to a part of a human body
for the purpose of stimulating blood circulation.
Such medical appliances are known which comprise a double-walled
sheath adapted to fit over a limb, for example an arm or a lower
leg portion, to be treated, and a pump apparatus arranged to
inflate and deflate the sheath cyclically thereby to apply a
pumping action to the limb and thus assist venous blood-flow
therein.
A particular disadvantage of such known appliances is that they
cannot be used when the limb to be treated is also to be encased in
a plaster cast, or sometimes when the limb has been subjected to
surgery; neither is it possible, with any appliance which
completely encloses the extremity, for the physician to use the
pin-prick test for nerve response at the involved extremity, nor
can he carry out the essential tests to assess the state of
circulation at the extremity.
A further disadvantage of known appliances is that they are not
suited to continuous use by the patient.
These disadvantages are particularly significant in relation to
appliances for use on feet and legs where as is known stimulation
of blood flow is desirable when the limb cannot be used for
walking.
We have discovered a venous pump mechanism in the sole of the human
foot, which under normal walking conditions for the foot, serves to
return blood from the leg into the abdomen with no assistance from
muscular action.
BRIEF STATEMENT OF THE INVENTION
According to one aspect of this invention, there is provided a
medical appliance comprising an active device for engagement, in
use, with at least the sole of a human foot, said device being
operative, in use of the appliance, to apply pressure cyclically to
said sole thereby to stimulate the venous pump mechanism in said
foot.
Essentially, said active device includes means to render said
device active when said foot is not in use for ambulation.
According to another aspect of this invention there is provided a
medical appliance comprising an active device in the form of an
inflatable bag shaped for engagement with at least the sole of a
human foot; inflation means connected to the bag and capable of
inflating the bag rapidly; means to deflate the bag; and means to
secure the bag to a human foot such that when being inflated the
bag applies pumping pressure to the sole of the foot.
DETAILED DESCRIPTION
Several medical appliances embodying this invention will now be
described by way of example with reference to the drawings, in
which:
FIG. 1 is a view of a first appliance, partly broken away and in
position on a human foot;
FIG. 2 is a view similar to FIG. 1, but showing a sectional view of
a second appliance;
FIG. 3 is a sectional view on the line III--III in FIG. 2;
FIG. 4 is a partly broken-away plan view of the bag 1 as an article
of manufacture, with a phantom superposed plan view of a right
foot, positioned for wrapped application of the bag thereto;
FIGS. 5 and 6 are views similar to FIG. 4, to show
modifications;
FIG. 7 is a side view in elevation of a slipper applied over a foot
that has been fitted with one of the inflatable foot-pump bags of
the invention;
FIG. 8 is a plan view of the slipper of FIG. 7, in flattened
condition, prior to use; and
FIG. 9 is a simple graph of pressure as a function of time, in aid
of discussion of use of the invention.
Referring to FIG. 1, the appliance here shown comprises an
inflatable bag 1 formed of plastics material and shaped for
engagement with the sole 10 of a human foot 11 in the plantar arch
thereof. The bag 1 is connected by way of a flexible pipe 2 to a
pump apparatus 3 by which the bag 1 can be inflated.
The bag 1 may be secured to the foot 11 by a suitable slipper or by
adhesive means, but in the form shown a cloth sling 4 embraces the
bag 1 and is secured over the instep 12 of the foot 11. Padding
material can be located between the sling 4 and the instep 12 if
necessary or desirable, and it is generally recommended that a
porous knitted or other fabric such as stockinette be first applied
to the foot so as to be interposed between the bag 1 and the foot,
thus allowing for ventilation and preventing chafing of the
skin.
The sling 4 and bag 1 are covered by a cloth slipper 6 which covers
the majority of the foot 11.
In use of the appliance when secured to a foot as shown in FIG. 1,
the pump apparatus 3 operates rapidly to inflate the bag 1 which
when applies a pumping pressure to the sole 10 of the foot 11, and
also urges the ball and heel of the foot away from each other, thus
flattening the plantar arch as would occur if the foot 11 were
placed on the ground during normal ambulation, thereby stimulating
venous blood-flow. Preferably, an accumulator tank is part of the
pump apparatus 3, the same being continuously charged by the pump,
and having the capacity for rapid inflation of bag 1. A valve
arrangement (not shown) in the pump apparatus 3 then allows the bag
1 to deflate, whereafter the bag 1 is again inflated, the
inflation/deflation cycle being repeated as long as treatment with
the appliance is required.
Preferably inflation of the bag 1 is effected in two seconds or
less to provide a satisfactory pumping action, while deflation of
the bag 1 can take as long as is necessary for the return of blood
to the veins of the foot 11.
The treatment thus provided simulates walking on the foot 11, and
thereby improves venous blood circulation in a person being treated
who would normally be unable to walk or possibly even stand on the
foot.
As a modification of the above described appliance, the valve
arrangement in pump apparatus 3 can be dispensed with, the pump
apparatus serving only for cyclic inflation of the bag 1, and at
least the surface of the bag 1 in contact with the foot 11 being
formed with air leakage orifices thereby to be permeable to air, or
being made of a microporous material which is inherently permeable
to air. Such a surface can be provided as will give the required
period for deflation of the bag 1.
Such an appliance gives the advantages that the air leaving the
permeable surface of the bag 1 serves to prevent accumulation of
moisture between the bag 1 and the foot 11, thus enhancing the
comfort of the user of the appliance and making skin problems less
likely.
A particular advantage of the appliance of this invention is that
it can be used when a foot is to be encased in a plaster cast, or
when the leg carrying the foot 11 has been subjected to
surgery.
FIGS. 2 and 3 of the drawings show an appliance in position for use
on a human foot 11 under a plaster cast 100, the same reference
numerals as used in FIG. 1 being used for corresponding parts.
The appliance shown in FIGS. 2 and 3 is similar to that shown in
FIG. 1, but is larger and extends not only under the sole 10 of the
foot 11, but also around the inside of the foot 11 and over the
instep 12 of the foot 11.
For use, the appliance is positioned on the foot 11 and the plaster
cast 100 is then formed over the bag 1 as required, with the pipe 2
from the pump apparatus 3 passing either through a hole in the cast
100 or out of one end of the cast 100.
The bag 1 can be maintained in a partially inflated condition while
the plaster cast 100 is formed, whereby allowance for subsequent
possible swelling of the foot 11 is made.
More specifically, and referring to FIG. 4, the inflatable bag 1
may comprise two like panels 20-21 of flexible material, such as
PVC or polyurethane film, peripherally sealed to each other as
indicated at an edge seam 22. Each of the panels comprises a
plantar-aspect sole area A configurated to longitudinally lap
essentially only the region of the foot between adjacent plantar
limits of the ball and heel of the foot and to extend into
substantial register with lateral limits of the sole of the foot.
The panels 20-21 also include, within the same peripheral seal or
seam 22, an integrally formed dorsi-medial area B which extends
transversely from one edge of the sole area A to a transverse
extent which is substantially as great as the longitudinal extend
of the area A. Typically, as shown, for a foot requiring a shoe in
the size range 9 to 12, the longitudinal extent X of the bag is
about 7 inches, and the maximum transverse extent Y of the bag is
about 8 inches. The average width W.sub.X of the sole area A is
about 2.75 inches, and the reduced width W.sub.Y of the area B is
about 2 inches. Along its anterior edge C, the area B is
substantially straight and transverse to the longitudinal direction
of area A, and along its posterior edge D, the area B tapers in a
concave sweep from the heel end of area A to the narrow transverse
end at width W.sub.Y, the inlet pipe 2 having sealed entry
approximately midway along the edge D.
What has been described for bag 1 in connection with FIG. 4 will in
and of itself serve well as an article of manufacture, in the
gauze, muslin, bandage material and/or adhesive tape may be relied
upon to retain a circumferentially wrapped application of the bag
to the foot. However, to facilitate such application without
initial resort to such other instrumentalities, FIG. 4 additionally
illustrates present preference for a flexible anchor tab 23 (as of
vinyl sheet) which is integrally formed with bag 1, extending
laterally beyond seam 22 at the longitudinal edge E of area A, and
for a tie-down tab 24, also integrally formed with bag 1 beyond
seam 22 at the transverse tip F of area B. A peel-off strip 25 of
suitable release material is shown protecting a coating of
pressure-sensitive adhesive on tab 24, so that upon adhesive
exposure, tab 24 may be "tacked" to tab 23 in adjustably secured
retention of the wrapped application of bag 1 to a foot. And it
will be noted for the preferred relatively non-stretch nature of
the material of tabs 23-24, a "tacked" circumferential completion
of the wrap, involving a fastening of tab 24 in outer-end lap with
tap 23, will enable circumferential hoop-tension force to be
relatively uniformly distributed along substantially the entire
longitudinal extent of area A, i.e., along edge E, thus assisting
in the plantar-arch flattening action described above. Plural
apertures in the larger tab 23 allow ventilation of adjacent skin
but do not impair the indicated distribution of hoop-tension
force.
Although FIG. 4 happens to show bag 1 for the situation in which
the right foot is accommodated, it will be understood that the same
accommodation to the left foot may also be made by the same article
of manufacture. In application to the left foot, the plan view of
FIG. 4 is reversed, from left to right, by placing the panel 20 on
the bottom, beneath panel 21, and the pressure-sensitive adhesive
is just as "tackable" to tab 23 as before, except for being engaged
beneath tab 23.
As has already been noted, the release of pressure fluid after each
pulsed delivery of inflation pressure is suitably via pores or
apertures in one or both of panels 20-21. It may be found
convenient to manufacture the bag 1 without such pores or
apertures, using puncturable material. And the surgeon who makes
the fitted application to a patient's foot need only first blow the
bag via his mouth, then hold inlet 2 closed with a finger, while he
uses a needle or other sharply pointed instrument to make plural
punctures of the panel (20 or 21) which is to be adjacent the sole
of the patient's foot; such puncturing may proceed while the
surgeon squeezes the bag to satisfy himself that the desired degree
of fluid leakage will be achieved in use. On the other hand, we
prefer that bags 1 be marketed with existing perforations in each
of two configurations, one specifically committed to right-foot
application and the other specifically committed to left-foot
application.
The described bag 1 of FIG. 4 will be seen, in cyclically
pressurized use within the circumferential bandage or sling 4 of
FIG. 1, or within the cast 100 of FIGS. 2 and 3, to provide a
peripherally continuous confinement of the midtarsal and plantar
regions of a foot, with the action of rapidly shrinking the
confinement in a cylindrical pattern of relatively rapid
short-duration release from shrink action. More specifically, this
confinement and cyclical action may be viewed as the means of
providing (a) upward and spreading force at longitudinally spaced
plantar regions of the sole of the foot, said regions being
essentially limited by and between the ball and heel of the foot
and (b) downward force at the region of the midtarsal joint. As a
result of the indicated cyclical pattern, the arch is caused to
flatten periodically and thus to stretch and neck down the internal
sectional area of the veins of the lateral plantar complex, with
resulting venous-pump action. Viewed in a still further light, this
confinement and cyclical action will be seen as the means of
providing vertically opposed squeezing forces between the plantar
region of the sole of the foot and the region of the midtarsal
joint, to thereby stimulate the venous-pump mechanism of the
foot.
In all cases, it is important and deemed significant that neither
the distal calf pump nor the proximal calf pump, nor any other of
the significant pumps of the venous-return system of the involved
leg is actuated in time-coincidence with foot-pump actuation. This
fact illustratively enables the described invention to be operative
within a cast, or to be operative in a region remote from
orthopedic fixation of a damaged tibia, knee, or femur, or to be
similarly remote from the region of a vein-transplant operation and
thus to relatively rapidly dissipate the pain and swelling which
are the normally expected post-operative consequence of such an
operation. In spite of the remoteness of foot-pump actuation from
these other regions of trauma, the fact of no other pump
involvements means that foot-pump driven venous return flow can be
substantially unimpeded in its direct delivery to and through the
region of trauma.
FIGS. 5 and 6 are further inflatable-bag embodiments of the
invention, although they are presently of lesser preference, as
compared to the embodiment of FIG. 4.
In FIG. 5, an inflatable bag 30 is longitudinally elongate and
corresponds generally to the function and placement of area A of
the bag 1 in FIG. 4. Bag 30 thus is designed for application to the
plantar region of the sole of the foot, being cyclically inflatable
via a flexible inlet pipe 31 sealed to bag 30 via locally sealed
access through the peripheral seam 32 of the bag. A perforated
flexible tab 33 corresponds to the tab 23 of FIG. 4, and a similar
but ultimately more narrow and more extensive tab 34 is connected
to the opposite longitudinal edge of bag 30, being adhesively
coated and protected by peel-off material 35. A retaining hoop is
circumferentially completed by pressure adhesion of tab 34 to tab
33. In a cyclical application of pressure fluid to the device of
FIG. 5, it is the longitudinal flattening of the arch which is
primarily responsible for foot-pump stimulation.
In the arrangement of FIG. 6, an inflatable bag 40, served by an
inlet pipe 41 and peripherally sealed at seam 42 is generally
rectangular but elongate in the direction transverse to the
longitudinal direction of the foot (phantom outline); and end tabs
43-44 correspond to those previously described, to enable
pressure-adhered completion of a circumferential hoop or belt
around the midtarsal/plantar regions of the foot. In a cyclical
application of pressure fluid to the device of FIG. 6, it is the
generally vertical squeezing action at the midtarsal/plantar region
which is primarily responsible for foot-pump stimulation, i.e.,
virtually without any arch-flattening action.
In certain post-operative situations wherein a part of the leg
other than the foot is involved, it is therapeutically beneficial
not only to operate the foot pump but also to allow the patient a
degree of freedom to stand and walk on his installed foot-pump bag
1, or 30, or 40. In such a situation, a fitted slipper 50 is most
useful, and may take any one of a variety of forms, so that FIGS. 7
and 8 will be understood to be merely illustrative of one of these
forms.
The slipper 50 comprises a sole member 51 of relatively rigid,
porous, light-weight material, centrally adhered to a sheet 52 of
light-weight duck or canvas, leaving flexible lateral flaps M-N
projecting laterally beyond the respective longitudinal side edges
of sole member 51; flaps M-N are adapted for wrap-around fit to the
particular foot, the lap of flap M over flap N being visible in
FIG. 7. Woven-fabric straps 53-54-55-56 have centrally-sewn
connection to the underside of sheet 52, at regions marked
53'-54'-55'-56' in FIG. 8, leaving free ends for completion of
circumferential fastening of sole member 52 to the foot at each of
three longitudinally spaced locations; it is convenient to have one
end of each strap fitted with a wire bail, so that the other end of
each strap can be threaded through the corresponding bail and be
Velcro-fastened against itself, to hold each adjusted strap
connection.
A tail portion 52' of fabric sheet 52 extends rearward of a small
yieldable heel step 57 at the back end of sole member 51, and tail
portion 56 is characterized by like, oppositely directed tabs
58-59, each of which has an exposed patch of Velcro loop material
58'-59'. These patches are selectively engageable with patches
60-61 of Velcro hook material sewn to the underside of panels M-N,
as viewed in the sense of FIG. 8. A thin panel 62 of anti-skid
material is bonded to the underside of the described assembly, to
complete the slipper.
In use, and after installation of an inflatable-bag (1,30, 40) with
its inlet pipe illustratively projecting upward and rearward from
the inner lateral side of the ankle, the flaps M-N are first folded
into overlap over the midtarsal region, and the straps 53-54-55 set
to hold the overlap. Then, tail 56 is folded upward and each of the
tabs 58-59 is wrapped around the back of the heel, into completion
of Velcro engagements, at 58'-60 and at 59'-61, respectively. The
slipper and foot-pump actuator are now in readiness to accept
cyclical pressure-fluid stimulation via connection to inlet 2. It
will be understood that the relatively rigid sole member 51
provides an excellent reference against which to react, upon bag
inflation, for application of arch-flattening and/or
midtarsal/plantar squeezing action of the nature discussed
above.
As a modification of the appliances thus far shown and described,
it will be understood that inflatable foot-pump bag 1 can be
incorporated in an article of footwear, such as a conventional
boot, to be worn by a person needing to use the appliance.
An inflatable bag 1 of the nature described in connection with FIG.
4 never requires a large volume change in proceeding through its
inflation/deflation cycle. The maximum inflated volume is in the
order of 300 to 350 cc, and on deflation the inflated volume can be
expected to reduce to 100 to 120 cc. Thus, the pressure-fluid
supply equipment 3 may be relatively small and convenient for
table-top or shelf mounting, with flexible-hose and disconnectable
coupling to the inlet pipe 2; this is true, whether the supply and
control means 3 is merely timed valving to assure programmed
delivery of pressure pulses of a fluid, such as oxygen from a
locally available tank supply, or the means 3 incorporates its own
pumping and/or accumulator mechanism to provide the needed pressure
fluid. Whatever the alternative, standard regulator, bleed
orifices, time delay devices and their adjustability are all well
known and therefore the supply means 3 may take on a variety of
different physical embodiments. What is important, however, is that
delivery of pressure fluid to inlet 2 and the bleed of fluid
through pores and/or apertures and/or valving in the deflation
phase shall meet certain criteria. Presently preferred criteria
will be stated in the context of FIG. 9, which shows pressure P to
develop quickly in the inflation phase a and to dissipate somewhat
exponentially, in the deflation phase b.
Although it has been stated above that bag 1 should be inflated in
two seconds or less, it is perhaps more accurate to state that in
our experience to date the inflation should be as quick as
possible, to imitate the normal impact of the sole of the foot on
the ground when walking. Such fast inflation imparts a jerk or
sharply pulsed action in return blood flow, and such action is
likely to be helpful in preventing venous thrombosis. It is
believed that maximum velocity, however transient upon pulsed
excitation, is more important than total blood flow. The veins have
check-valve formations, and the downstream side of each check valve
is a site where stagnation and clotting may occur; it is believed
that with bag inflation as rapid as possible, the opening phase for
each check valve is correspondingly rapid, thus locally stirring
stagnant return-flow blood and reducing the chances of a clotting
constriction of return-flow passages.
The peak pressure P for any delivered inflation impulse should be
that which is sufficient to produce the appropriate venous impulse,
whilst not being too uncomfortable for the patient to tolerate.
This will of course mean a different peak pressure P which will be
various, depending upon the particular patient and his affliction.
However, it can be said that, in our experience to date, a peak
pressure within bag 1 (20, 30, or 40) of 200 to 220-mm Hg has been
satisfactory, although there may be times when it is advisable to
use a peak pressure somewhat greater than 220-mm Hg. Such peak
pressure has produced comfortable actuation of the patient's foot
pump, in the circumstance wherein the supply apparatus 3 has
provided time-switched delivery of oxygen from a pressurized tank
and wherein the inflation time a was 0.4 second.
The total period (a+b) of the inflation/deflation cycle will also
be various, depending upon the confronting pathological condition
and, in particular, on the severity of venous obstruction and on
how quickly the physiological venous pump becomes filled. As a
rough guide, it can be said that in severe venous obstruction, as
in a limb with marked swelling, the period of the cycle might be as
frequent as every 10 seconds. In moderate swelling, 30 seconds
would probably be adequate, whereas for maintenance purposes a
60-second cycle should suffice. The optimum frequency of the cycle
can be audibly determined by the clinician, listening to the flow
in the posterior tibial veins with a Doppler monitor.
Although the interval between inflation pulses is very much greater
than the indicated rapid inflation time a, deflation should
commence automatically at achievement of predetermined peak
pressure, and initial deflation should be rapid and follow an
exponential pattern. Thus, we currently recommend leakage in bag 1
to the extent that, for example, for a peak pressure P of 210-mm
Hg, deflation to 30-mm Hg should be in about one second, and to
20-mm Hg in about 1.9 seconds. A timer, within apparatus 3,
reinitiates the cycle upon predetermined time-out of the interval
b.
Operations in which the described foot-pump actuating means are
likely to be particularly useful include leg fractures and
operations around the knee joint, where the leg veins may become
compressed either during or after an operation. It has been found
very useful in arterial and vein-graft operations, where some of
the leg veins have had to be ligated and where the collateral
venous-return channel (the long saphenous vein) has had to be
removed for use as an arterial graft.
It will be seen that the described uses of the invention involve a
method of promoting venous pump action in the leg of a living body
and that, from one aspect, steps of the method comprise (a)
application of a circumferential tie to the foot at the region of
the midtarsal joint, (b) applying upward and spreading force
between the circumferential tie and the foot at longitudinally
spaced plantar regions of the sole of the foot, said plantar
regions being essentially limited by and between the ball and heel
of the foot, (c) relaxing said force for a period of time, and (d)
cyclically repeating the force-application and force-relaxing steps
in a pattern wherein force application is relatively rapid, whereby
the arch of the foot is periodically caused to flatten and thus to
stretch the neck down the internal sectional area of veins of the
lateral plantar complex, with resulting venous-pump action.
From another aspect, steps (a) and (b) of the above method are
modified to the extent that the upward and spreading force is in
reaction to downward force at the region of the midtarsal joint,
i.e., vertically opposed squeezing forces between the region of the
midtarsal joint and the plantar region therebeneath. From a still
further aspect, steps (a) and (b) may be viewed as establishing a
peripherally continuous confinement of the midtarsal and vertically
opposed plantar regions of the foot, and developing the squeezing
forces through a periodic shrinking of the confinement.
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