U.S. patent number 3,865,102 [Application Number 05/369,447] was granted by the patent office on 1975-02-11 for external cardiac assist apparatus.
This patent grant is currently assigned to Hemodyne, Inc.. Invention is credited to William C. Birtwell, Robert L. Norton.
United States Patent |
3,865,102 |
Birtwell , et al. |
February 11, 1975 |
EXTERNAL CARDIAC ASSIST APPARATUS
Abstract
An apparatus for providing external assistance for the
circulation of blood in a patient in which a pressure medium
forming one or more active regions is enclosed in at least a
portion of a housing which in turn encloses a part of the patient's
body, such as the legs and/or other parts thereof generally below
the waist. At least a portion of the housing is in the form of a
rigidizable means, such means being in a non-rigid state when it is
applied to or placed on the patient's body and being capable of
assuming a rigid state when the apparatus is in operation. A
pressure actuation system cyclically applies pressure to the active
regions of the patient's body via the pressure medium in
synchronism and in correct phase with the patient's heartbeat.
Inventors: |
Birtwell; William C. (North
Scituate, RI), Norton; Robert L. (Norfolk, MA) |
Assignee: |
Hemodyne, Inc. (Norfolk,
MA)
|
Family
ID: |
23455521 |
Appl.
No.: |
05/369,447 |
Filed: |
June 13, 1973 |
Current U.S.
Class: |
601/152 |
Current CPC
Class: |
A61H
31/006 (20130101); A61H 9/0078 (20130101); A61H
2230/04 (20130101); A61H 2201/1238 (20130101) |
Current International
Class: |
A61H
23/04 (20060101); A61H 31/00 (20060101); A61h
007/00 () |
Field of
Search: |
;128/24R,64,297,299,DIG.20 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Trapp; Lawrence W.
Attorney, Agent or Firm: Dike, Bronstein, Roberts, Cushman
& Pfund
Claims
What is claimed is:
1. Apparatus for providing external assistance for the circulation
of blood in a patient comprising
housing means for enclosing a portion of said patient's body;
means for cyclically applying pressure to said body portion within
at least a portion of said housing means, said pressure applying
means including
pressure actuation means;
a pressure medium positioned in said portion of said housing means
between said pressure actuation means and said portion of the
patient's body, said pressure medium being responsive to said
pressure actuation means to apply pressure to said body
portion;
means for synchronizing the operation of said pressure actuation
means to apply said pressure cyclically to produce alternating
compression and decompression of said body portion in synchronism
and in correct phase with said patient's heartbeat;
at least a portion of said housing means comprising rigidizable
means which is in a non-rigid state when applied to or placed on
said patient and which is capable of substantially conforming to
any of a plurality of different shapes of the portion of said
patient's body to which it is applied when in said non-rigid state,
said rigidizable means being further capable of assuming a rigid
state and retaining said conformity when in said rigid state;
and
means for rigidizing said rigidizable means for operation of said
apparatus.
2. Apparatus in accordance with claim 1 wherein said housing
includes
a substantially rigid means;
means for enclosing said pressure medium within said rigid means to
form an active region of said housing; and
at least one rigidizable means positioned adjacent at least one end
of said rigid means for forming a passive region of said
housing.
3. Apparatus in accordance with claim 2 wherein
said active rigid means encloses a substantial portion of each of
the legs of said patient extending from at least the ankle region
to at least the upper thigh region of each said leg; and
said passive rigidizable means are positioned on each of said legs
adjacent the ankle ends and the thigh ends of said rigid means.
4. Apparatus in accordance with claim 1 wherein said housing
includes
at least two substantially rigid means enclosing at least two
portions of said patient's body;
means for enclosing said pressure medium within each of said
substantially rigid means to form at least two active housing
regions; and
a rigidizable means forming a passive region of said housing
positioned between and adjacent each of said rigid means.
5. Apparatus in accordance with claim 4 wherein
said rigid means extend respectively from a region above the ankles
to a region below the knees and from a region above the knees to a
region at the upper portion of the thighs on each leg of said
patient; and
said rigidizable means extend from a region below the knees to a
region above the knees on each leg of said patient.
6. Apparatus in accordance with claim 5 and further including
at least one additional rigidizable means positioned on each of
said legs adjacent at least one end of one of said rigid means for
forming a passive region of said housing.
7. Apparatus in accordance with claim 6 wherein said additional
rigidizable means are positioned adjacent both the ankle ends and
the thigh ends of rigid means on each leg of said patient.
8. Apparatus in accordance with claim 1 wherein at least a part of
said housing means includes
an active housing section formed of a substantially rigid portion
and a rigidizable portion; and
means for enclosing said pressure medium within said active housing
section to form an active housing region at said patient's
body.
9. Apparatus in accordance with claim 8 and further including
at least one rigidizable means positioned adjacent at least one end
of said active housing region for forming a passive housing region
at said patient's body.
10. Apparatus in accordance with claim 9 wherein
said active housing section extends from at least the ankles to at
least the upper portion of the thighs on each of the legs of said
patient; and
said rigidizable means are positioned adjacent both the ankle ends
and the thigh ends of the active housing section on each said
leg.
11. Apparatus in accordance with claim 8 wherein said active
housing section includes means for adjusting the rigidizable
portion thereof so as to conform said active housing section
generally to the configuration of the portion of said patient's
body which is enclosed thereby.
12. Apparatus in accordance with claim 8 wherein said active
housing section includes
a pair of active housing sections on each leg of said patient
extending respectively from a region above the ankle to a region
below the knee and from a region above the knee to a region at the
upper thigh;
means for enclosing said pressure medium within said active housing
sections; and
rigidizable means positioned on each leg of said patient between
and adjacent said pair of active housing sections to form a passive
region at the knee of each said leg.
13. Apparatus in accordance with claim 12 wherein said active
housing sections on each said leg include means for adjusting the
rigidizable portions thereof so as to conform said housing sections
generally to the portions of said patient's leg which are enclosed
thereby.
14. Apparatus in accordance with claim 1 wherein said rigidizable
means substantially completely forms said housing means.
15. Apparatus in accordance with claim 14 wherein said rigidizable
housing means forms an active housing on each leg of said patient
extending from at least the upper thigh region to the ankle region
on each said leg; and
further including means for enclosing said pressure medium within
said rigidizable housing means on each said leg.
16. Apparatus in accordance with claim 15 and further including
additional rigidizable means for forming a passive region on each
said leg positioned adjacent at least one end of said active
rigidizable housing means on each said leg.
17. Apparatus in accordance with claim 16 wherein said additional
passive rigidizable means are positioned at each end of said active
rigidizable means on each said leg.
18. Apparatus in accordance with claim 14 wherein said rigidizable
housing means forms a pair of active housings on each leg of said
patient extending from at least the upper thigh region to at least
the ankle region on each said leg, said apparatus further
including
means for enclosing said pressure medium within each of said
rigidizable active housings on each said leg; and
additional rigidizable means for forming a passive region on each
said leg positioned intermediate said active housings at the knee
region thereof.
19. Apparatus in accordance with claim 18 and further including
further rigidizable means for forming at least one further passive
region on each said leg adjacent an end of at least one of said
rigidizable active housings on each said leg.
20. Apparatus in accordance with claim 19 wherein said further
rigidizable passive means includes passive rigidizable means
positioned adjacent both the ankle end and the upper thigh end of
said rigidizable active housings on each said leg.
21. Apparatus in accordance with claim 14 wherein said rigidizable
housing means is in the form of a pant-like configuration which
extends from the waist region of said patient's body to at least
the ankle regions of both legs thereof; and further including
means for enclosing said pressure medium within said rigidizable
housing means to form an active housing from the waist region of
said patient to at least said ankle regions.
22. Apparatus in accordance with claim 14 wherein said rigidizable
housing means is in the form of a pant-like configuration which
extends from the waist region of said patient's body to at least
the ankle region of both legs thereof; and further including
means for enclosing said pressure medium within said rigidizable
housing means to form one or more active regions within a portion
of said rigidizable housing means at the parts of the patient's
body enclosed thereby, the remaining portion of said rigidizable
housing means forming one or more passive regions at the remaining
parts of the patient's body enclosed thereby.
23. Apparatus in accordance with claim 22 and further including
means for enclosing said pressure medium within said remaining
portion of said rigidizable housing means, said pressure medium
therewithin not being directly connected to said pressure actuation
means.
24. Apparatus in accordance with claim 22 wherein said active
regions are formed at least at a portion of each leg of said
patient extending from the thigh region to the ankle region
thereof.
25. Apparatus in accordance with claim 22 wherein said active
regions are formed at a portion of said patient's body extending
from the patient's waist to the thigh regions of each leg and
further at portions of said patient's body extending from said
thigh regions to the ankle regions of each said leg.
26. Apparatus in accordance with claim 22 wherein an active region
is formed at least at a region of said patient's body substantially
enclosing the buttocks of said patient.
27. Apparatus in accordance with claim 26 wherein said active
regions are further formed at least at a portion of the patient's
body extending from the thigh regions to the ankle regions on each
leg thereof.
28. Apparatus in accordance with claim 1 wherein said rigidizable
means extends from the waist to the thigh regions of said patient's
body.
29. Apparatus in accordance with claim 1 wherein
said rigidizable means is in a non-rigid state when the interior
thereof is not evacuated and is capable of assuming a rigid state
when said interior is evacuated; and
said rigidizing means is a means for evacuating the interior of
said rigidizable means.
Description
INTRODUCTION
This invention relates generally to apparatus for assisting the
circulation of blood in a human being and more particularly to an
apparatus for doing so externally by the utilization of
counter-pulsation techniques.
BACKGROUND OF THE INVENTION
Apparatus for providing external assistance in the circulation of
blood in patients has been described in previously issued articles
and patents, particularly U.S. Pat. No. 3,654,919 issued to W. C.
Birtwell, wherein a rigid housing encloses a portion of the
patient's body, such as the legs, and a non-compressible hydraulic
fluid is present within such housing. A suitable hydraulically
actuated compression and decompression means is then utilized to
cycle the pressure on said body portions via the non-compressible
hydraulic fluid. Means are provided therein specifically to assure
that the environment within the rigid housing is gas free so that
no effective dead space is present and the efficiency of the
compression and decompression energy transfer is maximized.
Further, in the decompression portion of the cycle, a negative
pressure is achieved immediately adjacent the body portion and
means are provided for synchronously overriding the substmospheric
pressure which is so obtained, such overriding being in appropriate
synchronism with the patient's heartbeat.
A number of problems arise in the use of the device described in
the above Birtwell patent. First of all, it is a relatively
cumbersome structure to handle, the use of a non-compressible
hydraulic fluid, such as water, making the overall apparatus quite
heavy. Moreover, the hydraulic actuation equipment which is
required to cause the compression and decompression flow of fluid
within the housing must be placed relatively near the patient so as
to avoid excessive hydraulic pressure drops along the fluid lines
thereof, usually such actuator being placed on the table on which
the patient himself lies, often substantially centrally located
between the patient's legs, as shown in the patent.
Not only is such apparatus therein difficult to use because of the
large size and weight of the rigid housing and the hydraulic fluid,
together with the hydraulic actuation equipment therefor, but the
presence of such elaborate equipment in the direct view of the
patient may tend to produce an adverse psychological reaction on
the part of the patient when the apparatus is being applied to the
patient's limbs.
Moreover, the use of such rigid, fixed volume housing requires that
they be made sufficiently large to fit the limbs of the largest
patient to which the apparatus is expected to be applied. Thus, for
patients with relativly small limbs, substantially more hydraulic
liquid is required to fill the enclosure, a factor which only adds
to the weight of the overall device and its difficulty in use.
Alternative structures for providing effective external assistance
for the circulation of blood have been devised as shown in our
copending U.S. patent application Ser. No. 332,629, filed on Feb.
15, 1973, by the same inventors of the invention described herein,
the design thereof providing for a reduction in the disadvantages
of the device in the abovementioned Birtwell patent while still
maintaining an effective energy transfer.
In accordance therewith, the copending application discloses
apparatus which utilizes a compressible fluid, such as air, either
alone or in combination with a non-compressible fluid, such as
water, for energy transfer at the body interface. The structure
shown therein has the advantage of being lighter in weight and less
cumbersome to use than the previous Birtwell apparatus, and
further, can be designed to reduce considerably the possibility of
producing a traumatic experience for the patient. The effect of
increased interface damping which may result from the use of at
least a partially compressible fluid medium therein is taken into
account by utilizing a more efficient actuation system designed as
a "closed" system wherein energy expended in transfer to the
patient's body is effectively stored and returned to the system for
reuse with a minimization of overall energy loss during operation.
Further, the effects of such increased damping can be overcome in
other embodiments of the structure shown in our copending
application by utilizing housing units having adjustable volumes,
the adjustment thereof being arranged to reduce the volume and,
hence, the dead space which may give rise to damping at the
interface of the medium with the patient's body.
While the proposed alternatives in our copending application offset
much of the disadvantages of the previously patented Birtwell
apparatus, such alternatives do not fully provide for improvements
which can be made by reducing the many damping effects which arise
in various ways when the apparatus is in use. As discussed therein,
such damping effects can be broadly identified as arising from two
major sources. A first source is herein referred to as "system"
damping and lies in the apparatus itself which comprises the system
for producing the cyclic compression and decompression energy
transfer to the patient's body. Thus, system damping can arise
because of the distensibility of the housing which is used as well
as the distensibility of the unsupported areas of the sealed
portion of the system which contains the actuating fluid at the
interface between the system and the portion of the patient's body
to which the pulsating pressure is applied. Further, the
instability of the shape of such sealed portion (i.e., the fact
that such sealed portion does not retain its shape during the
pulsating cycle) also contributes to the overall system damping.
The compressibility of the actuating medium which gives rise to the
presence of dead space within the housing also contributes to the
system damping. Finally, both the presence of trapped air at
various points within the system as well as the failure to provide
an adequate contact between the sealed interface portion of the
system and the patient's body can introduce additional damping into
the system.
A second source of damping is herein referred to as "physiologic"
damping and relates to the physical nature of the patient's body
itself. Such damping arises, for example, from the overall motion
of the patient's body which can occur during the application of the
pressure actuation system thereto. Additional factors which
contribute to such physiologic damping include the displacement of
body tissue, both in the areas to which the pressure is directly
applied and in the areas adjacent thereto, and the compressibility
of the body in those areas thereof which can contain gas, such as
the abdomen and/or the thoracic cavity.
A primary consideration in the design of the embodiments of our
copending application is the desire to reduce the weight and
awkwardness of the apparatus which hampers the handling thereof in
use as well as to lessen the traumatic effect of the appearance of
the apparatus to the patient. The use of a compressible gas
permitted such advantages to be obtained at the expense of
increasing to some extent the damping due to such gas
compressibility, thereby requiring increased energy capacity of the
energy source. Such increased damping was compensated for by the
use of a "closed" energy actuation system, as described therein,
and by the use of variable volume housings which could be adjusted
to reduce the dead space which arises because of the use of a
wholly or partially compressible gas as the energy coupling
interface medium.
Despite the advantages which accrue as a result of the apparatus
design disclosed in our prior copending application, it has been
found that further improvements in the structure and efficiency of
operation of an overall system of this type can be achieved if
other damping factors, present therein, can be reduced or
effectively eliminated.
SUMMARY OF THE INVENTION
This invention provides for a more effective transfer of actuation
energy via the coupling medium from the actuation source to the
body portion through the reduction in damping effects both from a
system and from a physiologic viewpoint. The invention makes use of
flexible closed members having a plurality of particles, such as
plastic beads, such members being capable in their flexible state
of conforming to a surface external thereto with which they are in
contact. Further, the air within such members can be evacuated so
that the members are changed from a flexible state to a rigid state
upon such evacuation. Such rigidizable members can be utilized in
the invention in a variety of ways either as "active" housing
elements or as "passive" housing elements, as discussed in more
detail below, in order to improve the efficiency of energy transfer
from the actuator through the coupling medium to the patient's
body.
The use of such rigidizable members permits a reduction in both
system damping and in physiologic damping so as to improve the
overall efficiency of operation thereof. Moreover, the flexible
nature of such members prior to evacuation permits them to be
applied more easily to the patient's body with a minimum of effort
and a lessening of any traumatic experience to the patient due to
their use. Further, the patient's comfort is improved immeasurably
by their use and the portability and general handling of the
overall system becomes greatly improved.
The use of such rigidizable members, either alone or in conjunction
with rigid housing elements of the type discussed in our previous
application, permits a reduction in system damping which arises
because of the distensibility of the housing itself as well as
because of the distensibility of the unsupported areas of the
sealed portions of the system which contain the actuating interface
fluid medium, as explained in detail below. The fact that such
rigidizable members can be made to better conform to the
configuration of the patient's body permits an even greater
reduction in the dead space which may be present in the sealed
portions of the system containing the active fluid medium than is
possible with the use of the variable volume rigid housings of our
copending application, so that the use of a fully or partially
gaseous, or compressible, medium will not adversely affect the
overall efficiency of energy coupling. Further, such conformability
reduces the possibility of the presence of trapped air and permits
a better contact between the sealed interface portion of the system
and the patient's body.
Further, the placement of the rigidizable members can be such as to
reduce the overall motion of the patient's body during the
application of the pressure actuation system thereto. Longitudinal
tissue displacement can be minimized both in the areas to which the
pressure is directly applied and in the areas adjacent thereto so
that not only is the damping reduction due to such factors reduced
sufficiently to create improvements in the energy transfer
efficiency but also undesirable motion of the patient during the
application of the apparatus and consequent discomfort of the
patient is greatly lessened. Further, the rigidizable elements
permit the apparatus to be more easily adjusted to patients of
different sizes during use, particularly in emergency or
semi-emergency situations.
Particular embodiments of the invention are discussed in more
detail below with the help of the accompanying drawings wherein
FIG. 1 shows a side elevation view of a portion of one embodiment
of the apparatus of the invention;
FIG. 2 shows an enlarged view in cross-section of a portion of the
embodiment shown in FIG. 1;
FIG. 3 shows a view in cross-section of a portion of another
embodiment of the invention;
FIG. 4 shows a plan view of a portion of another embodiment of the
apparatus of the invention;
FIG. 5 shows a view in cross-section of a portion of the embodiment
shown in FIG. 4;
FIG. 6 shows a view in cross-section of still another embodiment of
the apparatus of the invention; and
FIG. 7 shows a plan view of still another embodiment of the
apparatus of the invention.
FIG. 1 shows a portion of one embodiment of the invention in which
a pair of rigid housing units encloses the legs of a patient from
approximately a point above the ankles thereof to a point near the
top of the thighs thereof. For convenience only one of such housing
units is illustrated in the figure and a similar unit is utilized
on the other leg of the patient. Each such rigid housing unit can
be substantially of the form shown and discussed with reference to
FIG. 1 of our above-referred to copending application and may be
made of suitable rigid material, such as plastic or aluminum. As
can be seen in FIG. 1 of this application, a rigid housing member
10 encloses a sealed flexible member 21 which contains a
pressurizable fluid medium for coupling energy from an energy
actuation system, or actuator, 11 to the patient's leg 12. The
rigid housing means 10 extends from a region near the upper portion
of the patient's thigh to the ankle region. Although not
necessarily limited thereto, the sealed flexible member within the
housing can be formed separately from the rigid housing member
itself and, as discussed and shown with reference to FIG. 3 of our
copending application, can be in the shape of a tubular sealed
container made of suitable flexible material, such as a
nylon-neoprene cloth, for example. As described in our copending
application, the container has an appropriate integrally formed
fitting 13 which is inserted through a suitable opening in the
rigid housing and which is adapted to be connected to the pressure
actuation source 11. The major portion of the patient's leg is
encased in the sealed flexible member within housing 10 so that
pressure applied to the pressurizable medium therein via fitting 13
is then coupled to the patient's leg so as to produce a
compression/decompression cycle in a manner in appropriate
synchronism and in correct phase with the patient's heartbeat, as
described in our previous application and in the references to the
literature cited therein.
The coupling medium therein can be, for example, a compressible gas
or a combination of a compressible gas with a non-compressible
liquid and appropriate manifolding means may be used within the
interior of the flexible container to prevent collapse of the outer
surface thereof against the inner surface adjacent the wall of the
housing, as discussed in our previous application. At the region
above that end of the housing 10 which encloses the patient's
thighs, a rigidizable member 14 is placed so as to encircle such
region and so as to have one end thereof suitably buttressed
against the upper end of rigid housing 10, as discussed in more
detail below. A similar rigidizable member 15 is placed around the
ankle region of the patient's leg just below and in an abutting
relationship to the lower end of the rigid housing 10 which
encloses the patient's calf region.
The rigidizable members 14 and 15 are effectively formed as tubular
members, ankle member 15 being shown in more detail in FIG. 2 as
enclosing primarily the ankle region. Waist member 14 is of
substantially the same configuration and is made large enough to
enclose the region of the patient's body from the thigh to the
waist. Ankle member 15, alternatively, may be formed so as to
completely enclose the entire foot and ankle in the form of a
"boot-like" structure, if desired.
Both rigidizable members 14 and 15 are appropriately connected
through fittings 16 and 17, respectively, to a vacuum pump 18 which
is used to evacuate the air within the rigidizable members during
use. Both rigidizable members contain a large number of plastic
beads and their structure is a modification of a structure for
similar members used for a different purpose and sold under the
trademark "VAC-PAC," for example, as made and sold by Olympic
Surgical Company, Seattle, Wash. As seen in FIG. 2 the members are
modified so as to form a rigid flange 19 which can be suitably
connected to a flange 20 on rigid housing member 10 by means of one
or more bolt elements 22 as shown.
Members 14 and 15 are normally in a flexible state and can be
manipulated manually to cause them to conform generally to the
shape of the body region over which they are placed. When the
apparatus is put into operation, the interior of the flexible
members 14 and 15 are evacuated by vacuum pump 18 via a one-way
valve in each of fittings 16 and 17 and, when evacuated, the
members then assume an extremely rigid shape so that the interior
surface thereof conforms to the body portions which they
enclose.
When the pressure actuation cycle for causing compression and
decompression of the sealed member within the rigid housing 10 is
actuated, the then rigidized members 14 and 15 serve at least two
important functions in the operation of the overall apparatus.
First of all, the ends of the sealed member 21 abut the inner ends
of the rigidized members 14 and 15. Thus, as shown in FIG. 2, end
23 of sealed member 21 abuts inner end 24 of rigidized member 15. A
similar abutment occurs at the opposite end of sealed member 21 and
the inner end of rigidized member 14. Accordingly, the rigidized
members act as barriers to the longitudinal movement of the sealed
member so as to prevent the latter from moving outwardly from the
rigid housing 10 due to its longitudinal distensibility. Thus, the
coupling fluid medium within sealed member 21 is better confined to
the region of the leg to which pressure must be applied and the
transfer of energy through the coupling medium to the body becomes
more efficient than if the thigh and ankle rigid members 14 and 15
were absent.
Another advantageous effect of utilizing such rigidized ankle and
thigh members is that by preventing longitudinal movement of the
sealed member 21 containing the coupling fluid medium, the overall
motion of the patient's body is effectively minimized and the
discomfort and potential fear engendered in the patient by such
undesirable movement is greatly lessened.
In discussing the arrangement shown in FIGS. 1 and 2 it is
convenient to refer to the rigid housing member 10 within which the
coupling medium is contained in sealed member 21 of the apparatus
as an "active" member and, further, to refer to the rigidizable
ankle and thigh members which do not enclose the coupling medium as
"passive" members. In such discussions the term "active" member
shall mean a member in which working or coupling fluid is displaced
by the actuation system in a compression/decompression cycle so as
to provide the appropriate change in pressure at the body member as
required. The term "passive" member will mean a member which does
not contain coupling fluid so that changes in pressure occur
therein not because of the displacement of working or coupling
fluid, per se, but because of the displacement of tissue in the
patient's body.
In connection with the apparatus of FIGS. 1 and 2, therefore, one
can see that the rigid housing enclosing the sealed member which
contains coupling fluid represents the "active" element present in
the "active" region from the patient's ankles to the upper portion
of the patient's thighs. Further, the rigidizable members at either
ends thereof represent the "passive" elements in the "passive"
regions which are enclosed thereby. Thus, while a change in
pressure occurs in the active region because of the direct
displacement of coupling fluid by the actuator, additional changes
in pressure also occur in the passive regions to further assist the
required pressure changes within the bloodstream because of the
presence of the rigidizable members.
Accordingly, the overall efficiency of the system is further
increased over that available with previously known apparatus of
this general type and physiologic damping which is due to
displacement of body tissue is reduced since such displacement,
particularly in the active region, is confined solely to that
region and the active tissue is not displaced longitudinally
outward therefrom to so great an extent as in prior devices.
FIG. 3 shows a modification of the structure shown in FIGS. 1 and 2
wherein the rigid housing 10 of FIG. 1 is now formed as two
separate rigid housing members, each partially shown as members 25
and 26, the former extending from a region 27 just below the
patient's knee 28 to the ankle region (not shown in FIG. 3) and the
latter extending from a region 29 just above the knee to the upper
region of the thigh (not shown in FIG. 3). In accordance with such
structure the active pressure changes required are more effectively
confined to those regions of the leg where the majority of the fat
and muscle tissues are present and little or no active pressure
changes are provided in those regions where primarily bony
structure exists. Accordingly, in the embodiment of FIG. 3, the
rigid housing being formed as two separate housings encloses the
calf and thigh regions where the primary movable fat and muscle
tissue is present and does not enclose the bony region of the knee.
In the embodiment shown, the knee region is enclosed by a
rigidizable member 30 which, in the same manner as discussed above
with reference to the rigidizable end members 14 and 15, acts as a
passive member only. Thus, during operation, actuating fluid is
supplied to sealed members 31 and 32 within each of the rigid
housing members 25 and 26, respectively, in substantially the same
manner as shown in FIGS. 1 and 2. The ends 33 and 34 of rigidizable
member 30 abut the knee ends of sealed members 31 and 32,
respectively, and assist in confining the active pressure changes
to the thigh and calf regions and, hence, reduce the system damping
due to the distensibility of the sealed members 31 and 32.
The embodiment of FIG. 3 has an additional advantage in that, when
the apparatus is first placed on the patient, the rigidizable
member 30 at the knee region is in a flexible form. The patient is
then permitted to assume a more comfortable position than he is
able to assume in the apparatus of FIG. 1, for example, by being
able to flex his knees as desired prior to the rigidizing of the
knee member 30. Moreover, if the leg is bent at the knee the forces
which tend to move the patient longitudinally (and, hence, tend to
eject the patient from the apparatus) have a greater tendency to
balance out so the tendency for longitudinal patient motion is
reduced.
In the embodiment shown in FIG. 3 the passive members at the
regions above the thighs and below the ankles may or may not be
used, as desired, in the particular application in which the
apparatus is used.
In the embodiments discussed with reference to FIGS. 1-3, the
active portions thereof are shown as comprising rigid housing
members completely enclosing the active regions of the patient's
body. FIGS. 4 and 5 show an alternative embodiment of the invention
wherein the active housing member is shown as being formed of a
rigid portion and a rigidizable portion. Thus, the active members
40 and 41 include rigid portions 42 and 43 and flexible members 44
and 45, respectively. As can be seen best in FIG. 5, with reference
to active member 40, rigid portion 42 is fixedly attached along one
longitudinal side to a base member 46 as by a plurality of
appropriate screws, two of which are shown as screws 47, or other
suitable attaching means. Rigid portion 42 has an essentially
semi-circular cross-section and thereby forms approximately
one-half of the active member along the patient's leg from
approximately the upper region of the thigh to the ankle region.
Rigid portion 42 encloses a sealed flexible member 48 which
contains the coupling fluid and which is appropriately connected to
an actuator system 55 of the type discussed above, via appropriate
connectors 56 and 57.
The remaining portion of the active member comprises flexible
member 44 containing plastic beads of the general type shown above
for the passive waist, ankle and knee members discussed with
reference to FIGS. 1-3. Flexible member 44 is fixedly attached
along one longitudinal side parallel to the fixedly attached side
of rigid portion 42. Member 44 can be attached prior to the
placement of fluid sealed member 48 via a plurality of screws one
of which is shown as screw 49, or other suitable attaching means.
Flexible member 44 can be shaped to the inner part of the patient's
leg and can be adjusted in accordance with the leg diameter to
provide for the closest conformity thereto by affixing its
non-attached side to the rigid portion along one of a plurality of
parallel spaced longitudinal regions via appropriate attaching
means 50, as shown. Both flexible members 44 and 45 are connected
to a vacuum pump 51 via connectors 52 and 53.
Flexible member 44 can be suitably shaped while in its flexible
state not only to conform to the shape of the patient's leg but
also to abut against the ends 54 and 54A of sealed member 48 so
that upon evacuation member 44 assumes a rigid shape so as to
confine the sealed member 48 to the position shown and, thereby, to
reduce the damping which arises because of the distensibility of
the member 44. Because of the presence of rigid portion 42 and the
ability of rigidizable member 44 to conform closely to the leg,
sufficient pressure changes can be achieved with the construction
shown to produce the desired pulsation effect without the need to
completely enclose the leg with sealed member 48. Alternatively,
however, a sealed member 48 completely enclosing the leg between
the leg and both the rigid and rigidizable portions may be used.
Although the embodiment shown in FIGS. 4 and 5 utilizes rigid and
rigidizable portions of the active units, each of which encloses
approximately one-half of the leg, in some applications it may be
found desirable to alter the shape of such portions to enlarge or
decrease the portion of the leg enclosed by either one. Moreover,
the construction shown in FIGS. 4 and 5 can be used with or without
the passive ankle and waist members discussed above with reference
to the embodiments of FIGS. 1-3. Further the embodiments of FIGS. 4
and 5 can be alternatively constructed so as to comprise two
separate active units at the thigh and calf regions while
simultaneously using a passive knee member as shown in FIG. 3,
either with or without the waist and ankle passive members
discussed above.
FIG. 6 shows a portion of an active housing configuration which can
be substituted for the rigid housing member of FIG. 1. As shown in
FIG. 6, the active housing member can be formed of a rigidizable
member 50 which can extend from the ankle to the upper thigh
region. A sealed member 51 is placed around the patient's leg
between the rigidizable member 50 and the leg, member 51 containing
the coupling fluid and being connected to an actuating system via a
suitable connector 52 drawn through an opening in rigidizable
member 50. In its flexible state member 50 can be appropriately
shaped around the leg and sealed member 51 to reduce the tendency
to form dead space during operation. Member 50 can be further
shaped at its end points to conform closely to the leg, as shown,
for example, at region 53. When member 50 is evacuated via a vacuum
pump (not shown) connected to connector 54, sealed member 51 is
appropriately confined within the then rigidized member 50 so as to
further reduce the system damping.
The rigidizable active housing unit of FIG. 6 can be utilized with
rigidizable passive members at the waist and ankle ends thereof in
substantially the same manner discussed with reference to FIG. 1,
or such passive end units may be omitted as desired. Further,
rigidizable active housing members of the type shown in FIG. 6 can
be substituted for the two separate rigid thigh and calf active
housing members of FIG. 3 which configuration is then usable with
the passive rigidizable member at the knee region and with or
without the passive members at the ankle and waist ends of the
active housing units.
FIG. 7 shows still another alternative embodiment of the invention
wherein a single rigidizable member 60 is formed in a pant-like
configuration which extends substantially from the patient's waist
to the patient's feet. In such a configuration, a sealed member
which contains the coupling medium may be formed as a single member
(not shown) which also is in a pant-like configuration and extends
from the ankle region to the waist and is enclosed by rigidizable
member 60. In such a case the active cycle pressure transfer via
the coupling fluid is substantially the same at all points
contacted by the inner sealed member. Accordingly, the
effectiveness of the energy transfer is enhanced because active
pressure transfer occurs not only at the muscle and fat tissue on
the leg but also at such tissues on the patient's abdomen and
buttock regions.
In some applications where sufficiently high pressures may be
utilized in the structure of FIG. 7 to produce discomfort or even
potential damage to the patient's organs within the abdomen and at
the genitalia, the rigidizable structure and interior activated
sealed member containing the active coupling medium may be shaped
so as to extend only from the ankle region to the region enclosing
the patient's buttocks, there being no structure, rigidizable or
otherwise, placed at or across the abdomen and genital region shown
by the dashed line 61 in FIG. 6, so that no pressure at all is
applied thereto. Alternatively, the rigidizable member 60 may be
arranged in its flexible state to form a bridging structure at the
region 61 to act as a non-pressurized region in that manner.
As a further alternative the entire region above the thighs from
about line 62 to the patient's waist may be made passive. In one
form thereof, an interior sealed member containing coupling fluid
may be used within rigidizable member 60 but such interior coupling
member is separate from the active coupling members at the legs and
the coupling fluid therein is not directly connected to the
pressure actuation system. Alternatively, the passive interior
coupling member above line 62 may be omitted so that the upper
portion of rigidizible member 60 can be arranged in its flexible
state to be positioned in direct conformable contact with the
entire region from waist to thigh so that in its rigid state it
confines the interior active sealed member to the region below line
62 from thighs to ankles.
The use of the configuration of FIG. 7 wherein there is passive
pressurization of the region from waist to thighs at least at the
buttock region, reduces the physiologic energy loss which is due to
damping arising from patient motion. Additionally, such passive
pressurization of the buttocks increases the potential quantity of
blood which can be caused to flow to the heart over that which is
caused to flow when such passive pressurization is not used. Such
operation will tend to permit a reduction in the stroke volume of
the actuator and, hence, a corresponding reduction in the power
requirements at the actuator source, so that equivalent overall
system efficiency at lower power inputs is obtained as compared to
systems using active housing members applied only to the patient's
legs. Such efficiency can be maintained even with the lower power
requirements because of the recapture of some of the energy which
is normally lost in moving the patient out of the leg units. In the
embodiment described any such motion causes pressurization of
buttock region against the rigidized passive container positioned
between the waist and thighs. The tissue pressure created by this
patient motion is effective in increasing retrograde blood flow in
the arterial system. The phasing of this passive tissue
pressurization is inherently correct with respect to the phase of
the external pressure on the legs.
Alternatively, a separate passive rigidizable member can be used
from waist to thighs in combination with any appropriate active or
active/passive units on the legs, such latter units being of any
convenient configuration shown in the previously described
embodiments of FIGS. 1-6 or the embodiments of the leg units shown
in our previously filed application mentioned above.
Further, while a rigidizable member in the form of the vacuum
operated containers discussed above is presently believed to be
preferable in the embodiments disclosed, other rigidizable members
may be substituted therefor. For example, a rigidizable foam which
is relatively flexible, or fluidic, in nature may be used, which
material is then allowed to harden into a rigid state upon the
addition of a catalyst. Other similar rigidizable means may occur
to those in the art.
Accordingly, the invention is not to be construed as limited only
to the specific embodiments shown and described herein except as
defined by the appended claims.
* * * * *