CA1079594A - Intermittent compression device for limbs - Google Patents

Abstract

INTERMITTENT COMPRESSION DEVICE FOR LIMBS

ABSTRACT OF THE DISCLOSURE
An apparatus for intermittently inflating and deflating a compression sleeve. The sleeve has a plur-ality of longitudinally disposed compression chambers which encircle a patient's limb when the sleeve is se-cured about the limb. The sleeve is inflated in a man-ner to apply a compressive pressure gradient against the patient's limb which decreases from a lower to upper portion of the patient's limb to enhance the velocity of blood flow through the limb.

Description

BACKGROUND OF THE INVENTION
The present invention relates to therapeutic an~
prophylactic devices, and more particularly t~ devices for applying compressive pressures against a ~atient's limb.
It is known that the v210city of blood flow in a patient's extremities, particularly the legs, mark-edly decreases during confinement of the patient. Such pooling or stasis of blood is particularly pronounced during surgery, immediately after surgery, and when the patient has been confined to bed for extended periods of time. It is also known that stasis of blood is a sig-nificant cause leading to the formation of thrombi in the patient's extremities, which may have a severe dele-terious effect on the patient, including death. Addition-alI~, in certain patients it is desirable to move fluid out of interstitial spaces in extremity tlssues, in order to reduce swélling associated with edema in the extremities.

SUMM~RY OF THE INVENTION
A principal feature of the present invention is the provision of a device of simplified construction for applying compressive pressures against a patient's limb in an improvea manner.
The device of the present invention comprises, an elongated pressure sleeve for enclosing a length of the patient's limb. The sleeve has a plurality of separate fluid pressure chambers progressiqely arranged longitu-dinally along the sleeve from a lower portion of -the limb , . .

;. , . ~r ~ ~ ~7 ~ ~4~ ~

to an upper portion of the limb proximal the patient's heart relative the lower portion. The device has mea~s for intermittently forming a pressure pulse from a source of pressurized fluid auring periodic compression cycles and means for separately connecting the pulse to the cham~ers. The device also has means for developing pro-gressively diminishing rates of pressure increases in pro-gressively located upper chambers duxing the compression cycles, and means-for intermittently connecting the cham-bers to an exhaust means during periodic decompression -cycles between the compression cycles.
-A feature of the present invention is that the sleeve applies a compressive pressure gradient against the patient's limb during the compression cycles which progress- -ively decreases from the lower to upper portion of the limh.
Thus, a feature of the present invention is thatthe devlce enhance~ the velocity of blood flow through the patient's limb, and deters pooling of blood in the limb.
Another feature of the invention is that the de-veloping means may comprise a plurality of flow control or-ifices of different size to vary the rate of fluid flow in-' to the separate ~hambers.
--- Still another feature of the invention is that the sleeve may have chaI~bers of varying volume to facilitate formation of the desired compressive pressure gradient.
.
A feature of the present invention is the pro-vision of an apparatus for controlling the operation of the

-2-. .

compression sleeve during the compression, decompression cycles.
Another feature of the present invention is that the sleeve may be separated between adjoining cham-bers to facilitate movement oE sleeve poxtions defining the adjoining chambers during operation of the device.
Further features will become-more fully appar-ent in the following description of the embodiments of ~his invention and from the appended claims.

,. . , . ~
DESCRIPTION OF THE DR~WINGS
: . In the drawings: .
Fig. 1 is a fragmentary perspective view of ~n intermittent compression ~evice of the present inven-ti.bn;
lS - Fig. 2 is a front plan view o a compression sleeve for the device of Fig. l; .
FigO 3 is a back plan view of the sleeve of Fig. 2;
Fig. 4 is a fragmentary sectional view taken substantially as indicated along the line 4-4 of Fig. 3;
. . FigO 5 is a sectional view of a manifold for the compression device taken substantially as indicated along the line 5-5 of Fig. l;
Fig. 6 is a graph illustrating pressure-time : ~
- : ~ 25 curves during operation of the device of Fig. l; and - Figs. 7-9 are.sch2matic diagrams o pne~matic :-- , .~ . . .

- ~ ~ . con~rol:.circuits for-the device-of FigO~
.. ~ .. ~

` ` ' DESCRIPTION OF THE PREFERRED EMBODIMENTS
-Referring now to Fig. 1, there is shown an in-termittent compression device generally designated 20 hav-ing a c~ntroller 22, a manifold 24, and a pair of elongated compression sleeves 26 for enclosing a length of a patient's extremitïes, such as the legs as shown. The controller 22 is connected through a tube 28 to a source of pressurized gas ~not shown), to an exhaust tube 30~ ancl to the manifold 24 through a conduit 320 In turn., the manifold 24 is con-nected to the separate sleeves 26 through separate sets ofconduits 34a and 34b. As will be seen below, each of the conduits 34a and b of the sets are connected to separate compression chambers in the sleeves.
As shown in Figs. 2-4, the sleeves 26 have a pair of flexible sheets 36 and 38 which are made from a fluid impervious material, such as polyvinyl chloride.
. The sheets 36 and 38 have a pair o~ side edges 4Oa and 4Ob, , . ~, and a pair of end edges 42a and 4Zh connecting the side edges 40a and b. As shown in Figs. 3 and 4, the sheets have a plurality of laterally extending lines 44, such as lines of sealing, connecting the sheets 36 and 38 together, and a pair of longitudinally extending lines 46, such as lines of sealing, connecting the sheets 36 and 38 together and connecting ends of the lateral lines 44, as shown. The : 25 connecting lines 44 and 46 define a plurality of contiguous chambers 48a, 48b, 48c, 48d, 48e, and 48f which extend lat-erally in the sheet, and which are disposed longitudinally 'i - ., :, - - ~ :

: `, "

-, -, - , .,- ~` . , - ~ ,:
... . . . . .

. ~

in the sleeve betwPen the end ed~es 42a and 42b. When the sleeve is placed on the patient's leg,. the lowermost : . chamber 48a is located on a lower.part of the leg adjacent the patient's ankle, while .the uppermost hamber is located 5 - on an upper part of the l~g adjacent the mid thigh. : :
In a preferred embodiment~ the side edges 40a ~ ~
and 40b and the connecting lines 46 are tapered from the .. :
end edge 42a toward the end edge 42b. Thus, the sleeve 26 has ~.reduced configuration adjacent its lower end to facili- :
tate placement of the sleeve on the more narrow ragion~ of . .the leg adiacent the patientls ankles. Mor~over, it will be seen.that the c~nnecting.lines 44 and 46 define chambers having volumes which progressively increase in size from the lowermost chamber 48a to the uppermost chamber 48f.
. 15 ~he.relative si.ze of the chambers facilitates the device in conjunction with orifices to develop a compressive ~ressure ..
gradient during compression or inflation which decreases from a lower part of the sl~eve adjacent the end edge 42b ~ toward an upper part of the sleeve adjacent the end edge ::
:~ 20 42a.
` As illustrated in Figs. 3 and 4, the adjoining chambers 48c and 48d may have their adjacent portions defined by spaced connecting lines 44' and 44" which extend laterally in the sleeve between the connecting lines 46. The sheets 36 and 38 may be severed, such as by slitting, along a line 50 between the lines 44' and 44" to separate the aajoining chambers 48c and 48d. As shown, severence line 50 may extend the width of the chambers between th~ connecting lines 46. The line 50 permits free relative movement between.the adjoining chambers when the sleeve is inflated to prevent hyper-! extension o~ the leg during operation of the device, and also facilitates sizing of the sleeve to the leg of a particular patient.
. The sleeve 26 may have one or more sheets S2 . 15 of a soft flaxible material for cover.ing the outside of ; the fluid impervious sheets 36 and 38 relative the patient's ` leg. The sheets 52 may be made of any suitable material, : such as Tyvek, a trademark of E.I. du Pont de Nemours, and provide an aesthetically pleasing and comfortable outer surface for the sleeve 26. The shleets 52 may beattached to the sheets 36 and 38.by any suitabie means, such as by lines 54 of stitching along the side edges 4Oa and.b and end edges 42a and ~ which pass through the sh~ets 52 and sheets 36 and 38 to secure the sheets together. As 25 shown in Fig. 2, the sheets 52 may have a plurality of open- ~
: ings 56 to receive a plurality of connectors 58 which are : :.
; secured to the sheet 36 and which communicate with the ., ~.
. ~ ' - . :
- ~ -6-. . ' ~ . ,:' ., .

~ P~

separate chambers in the sleeve 26. As illustrated in Fig. 1, the connectors 58 are secured to the conduits 34a and b, such that the conduits separately communicate with chambers in the sleeve through the connectors 58.
As best shown in Figs. 2 and 3, the sleeves 26 may have a plurality of hook and loop strips 60 and 62, re-spectively, to releasably secure the sleeves about the pa-: tient's legs. The hook strips 60 extend past one of the side--edges 4Ob of the sleeve, while the loop strips 62 are secured to the outside of the outex sheet 52. During place-ment, the.sleeves 26 are wrapped around the patient's legs, and the hook strips 60 are releasably attached to the asso-ciated loop strips 6~ on the outside of the sleeves in or-der to secure the sleeves on the legs and confine movement of the sleeves away from the patient's legs when inflatea during operation of the device.
; . Referring now to Figs. 1 and 5, the manifold 24 has a housing 64 defining an inlet port 66 and a plurality of outlet ports 68. The inlet port 66 of the housing 64 is : 20 connected to the conduit 32 by a threaded plug member 70 .. which.is secured in the housing 64, while the outlet ports 68 are..separately connected to the conduits 34a by a plur- -.
: ality of threaded plug members 72 which are secured in the housing 64. The outlet ports 68 also communicate with the conduits 34b through a plurality of threaded plug members ~: ; 74 which secure one end of the conduits 34b to the housing . :.
, . ~
64. Additionallyr a pressure.relief valve or pressure in- :

:

t~

dicating device 76, as desired, may be secured to the housing 64 such that it communicates with one of the out-le~ ports 68' through a bore 78 in the housing.
As illustrated in Fig. 5, the housing 64 has an elongated channel 80 communicating with the inlet port 66, and the channel 80 separately communicates with the outlet ports 68 through a plurality of flow control ori-fices 82. As shown, the orifices 82 preferably have in-ternal diameters of differing sizes to vary the 10w rate of gas from the common channel 80--to the different outlet ports 68. In accordance with the present invention, the . lower chambers in the sleeves are filled at a faster rate than the upper chambers to provide greater pressures in the.lower chambers. With ref,erence to Figs.1, 3, and 5, the two conduits 34a and b which are connected to the lower-., most chambers 48a in the pair of sleeves are-also connected to the joined outlet ports 68' communicating with the ori-fise 8~' of largest e~fective size to permit'the greatest ., ~, rate of ~luid flow into the lowermost chambers. Similarly, the two adjoining upper chambers 48b in the pair of sleeves ,: 26 are connected by two conduits to the joined outlet ports 68" comrnunicating with the flow control orifice 82" of next '~, -, ' smaller size, such:that the rate of gas flow into the cham-bers 48b is less than that into the chambers 48a. Corres-ponding.pairs of the remaining chambers axe separately con-, nected to the orifices 82 in a similar manner, such thatthe relative orifices cause a filling rate vf gas into ad~

!:
'. .'. , '.
: . , ' ' '' , .' ~ '' j .

- `~

joining chambers which is greater in the lower adjoining than the upper adjoining chamber. Thus, the rate of press-ure increase in each lower chamber is greater than that in the upper chambexs, such that the sleeve applies a compress-ive pres~ure gradient against the legs which decreases froma lower part of the sleeve toward an upper part of the sleeve during the inflation cycles of the device.
As previously discussed, formation of the desir-ed compressive pressure gradient is enhanced by the relative in-creasing v~lumes in the chambers from the lower to upper partof the sleeves. The sized flow control orifices 82 and cham-bexs thus operate in conjunction with each other to develop the desired compressive pressuxe gradient during the infla-tion cycles. Of course, the relative volumes of the sleeve chambers and diameters of the flow control orifices 82 may be suitably selected to obtain the desired pressure gradient exerted by the sleeves against the patient's leg during the inflation cycles such that the sleeves enhance the velocity of blood flow through the patient 1 5 legs.
A schematic diagram of a circuit for the controller i 22 is illustrated in Fig. 7. In a preferred form, the cir-cuit is composed of pneumatic components since it is a pre-ferred procedure to minimize electrical circuit components in the potentially explosive environment of an operating room.
As shown, the controller 22 has a regulator 90 w~ich is con-nected to the source S of pressurized gas. The regulator 90 serves to lower pressure supplied from the source S, and supply a ~: ' , .

. . :
', ' ' - '.' b _9_ -: - . . :-I~ ' .i regulated air supply for use in driving the circuit of the controller 22 to inflate the compression sleeves. The reg-ulator 90 is connected to a filter 91 and two-position switch 92 which is utilized to remove the ~ix supply fro~ the cir-cuit and sleeves when the switch is placed in an off posi-tion, and supply air to the circuit and sleeves when the switch is placed in an on position.
When the switch 92 is turned on, the air_supply `~ from regulator 90 passes through the switch 92 and through the port 94 of gate 96 to the inlet ports 98 and 100 of a negative output timer 102. Air will be continuously sup-plied from the regulator 90 to the ports 98 and 100 of timer 102 until air is received at the inlet port 104 of gate 96, at which time the passage of air through the inlet port 94 of the gate 96 is terminated. When actuated at port 98, the timer 102 connects the gas supply at its inlet port 100 to its outlet port 106 until the timer times out. The timer 102 may be adjusted to modify the time at which it times out after being first actuated, and the timer 102 is utilized to determine the period of time elapsed dur-ing an inflation cycle of the intermittent compression device. Accoraingly, the duration of the inflation cycles may be modified by suitable adjustment of the timer 102.`
When the timer 102 is actuated, the gas supply at the outlet port 106 of the timer is connected to port -~ 108 of gate 110 which, in this condition, prevents pass-age of gas from the switch 92 through the port 112 of gate .

,~- . . .,:

., ,. , j, 110 to a second negative output timer 114. Thus, the timer 114 is inactive at this time. However, the gas supply at outlet port 106 of timer 102 actuates a two-position or shift valve 118 at its port 116. In this conf~guration, the port 120 of the shift valve 118 is connected to the port 122 of the valve, while the port 124 of the valve is disconnected from the valve port 122. At this time the gas supply from regulator 90 is connected through switch 92, a flow control valve 1~6l ~he ports 120 and 122 of the shift valve 118, and through the flow control orifices 82 of the manifold 24 to the various chamhers in the pair of sleeves, designated 1, 2, ..., 6. The timer 102 thus actuates the shift valve 118 to initiate the inflation cycles during which air is supplied - from the source S and regulator 90 through the shift valve 118 to the manifold 24 and sleeves in ordex to simultaneously inflate the sleeves.
The flow control valve 126 is utilized to control the gas pressure supplied to the manifold 24 and the sleeves.
` Since a re~atively high pressure is required to actuate the various pneumatic components of the controller circuit, the valve 126 reduces the pressure f-rom the regulator 90 supplied through the shift valve 118 to the sleeves in order to pre-vent overinflation of the sleeves.
When the inflation timer 102 times out, the timer ~5 removes the gas supply from its outlet port iO6, and thus from port 116 of shift valve 118 and port 108 of gate 110. In thi~
con~iguration, the gate 110 passes the ~as supply from switch . ~ :

.
.
. . .

'`` ~

9~ through its inlet port 112 to the inlet ports 128 and 130 of the deflation timer 114. Thus, when the inflation timer 102 times out, the deflation timer 114 is actua~ed at its inlet port 128, such that the air supply is passed S from the inlet port 130 to the outlet port 132 of the timer ; 114. In turn, the air supply is connected to port 134 of shift valve 118 and inlet port 104 of the gate 96, causing the air supply to be removed from the inlet ports 98 and 100 of the inflation timex 102.
The air supply from timer 114 actuates shift valve 118 at its port 134, and the actuated valve 118 dis~
- connects its port 122 from port 120 and connects port 122 to port 124 o the valve. At this time, the air which was filled into the various chambers of the sleeves during the inflation cycle passes in a reverse direction through the flow control orifices 82 of the manifold 24, through the port 122 of shift valve 118 to the valve port 124, and then ~:
to the exhaust tube or port 30. In this manner, the timer 114 initiates simultaneous deflation of the sleeves through the manifold 24, the shift valve 118, and the exhaust tube 30.
When the timer 114 times out, the ~as supply i5 removed from the port 134 o~ shift valve 118 and from the inlet port 104 of gate 96, causing the gate 96 to again con-nect the gas supply from the regulator 90 and switch 92 to . the inlet ports 98 and 100 of the inflation timer 10~
- `: Ac~ording~y, when the timer 114 times out at the completion ..: - .
:. - . , ~ ,. ,:
: ~ -12~

' ~3~

of each deflation cycle, the inflation timer 102 is actuated to start another inflation cycle. In this manner, the timers 102 and 114 control the pe~iodic inflation and deflation cy-cles. The timer 114 is also adjustable to suitably modify the duration of the deflation cycles between successive in-flation cycles.
A chart of the resulting pressures P formed in the chambers in each sleeve with respect to time ~ is illustrated in Fig. 6. As shown, at the--time to an in~lation-cycle is in-itiated by actuation of the inflation timer 102 o Fig. 7.
The pr~ssures in the various chambers of the sleeve simultan- ' eously increase until approximately the time tl when a defla- -tion cycle begins responsive to actuation of the deflation timer 114 of Fig. 7. The sleeve chambers then deflate and re-main in this state until the deflation timer 114 times out and the actuated inflation timer 102 initiates another inflation cycle at the time t2. In accordance wikh the previous in- -vention, the various chambers of a given slePve are filled at varying rates during the inflation cycles~ As shown,'the curve designated a, illustrating the greatest rate of pressure change, is associated with the lowermost chambers of the sleeves, while 'the curve f, showing the smallest rate of pressure change, cor-responds to the uppermost chambers in the sleeves. The remainr-ing curves between the curves a and f illustrate the pressure profiles with respect to time in the corresponding chambers located hetween the lowermost and uppermost chambers ln the sleeves.

. .

. . - ~ ~, .~ .

-13- ~

lV'~59~

A schematic diagram of another circuit for the con- :
troller 22 of the present invention is illustrated in Fig~ 8.
As before, the controller 22 has a regulator 200 ~onnected to the .
source S, a filter 202 connected to the regulator 20Q, and a two-position switch 204 connected to the filter 202 for connecting .
the source or supply to the circuit~ .
When the swi~ch 204 i5 turned on, the air supply from regulator 200 and filter 202 passes through the switch 204 to :
port 206 of a shift valve 208. In a deflation configuration of `
the valve.208, the supply is connected through the valve ports 206 and 210 to the inlet port 212 o~ a positive output timer 214.
At the same time, the line 216, communicating with the manifold .
and sleeve, is connected through a flow control valve 218 and ports 220 and 222 of shift valve 208 to the exhaust line 30. Thus, with the shift valve 208 in this configuration, the chambers in . .
the sleeve are deflated through the exhaust line 30 during a ~
:, .:.
de1ation cycle. When the timer 214 times out, the su~ply is con- :
~ nected from port 210 of valve 208 through the timer 214 to the - . port 224 of shift valve 208. In turn the shift valve 208 connects -:
its port 206 to port 220 in order to initiate an inflation cycle, while disconnecting its port 222 from port-220 and disconnecting :
its port 206 from port 210. The deflation cycle is terminated at . this ti~e, and the duration of the deflation cycle may be modlfied by suitable adjustment of the timer 214. ~
During the inflation cy~le, the supply is connected .
through valve port 220 to inlet port 226 of a positive ou~pu~ :
timer 228, as well as through the flow control valve 218 to the :
:~ line 216, the manifold, and sleeve in order to inflate the cham- :
. . :
,. , . ::
., . :

:. . . . - ....... .
14- ~ ~ .

`` ( ( bers in the sleeve. The control valve 218 reduces the supply pressure from the relatively high pressure required to actuate the pneumatic components of the circuitry to a lower pressure for use in inflating the sleeve.
When the inflation timer 228 times out, the supply is connected from port 220 of valve 208 through the timer 228 to port 230 of the shift valve 208. In turn, the actuated valve 208 again connects the supply through its-ports 206 and 210 to the deflation timer 214, and connects its port 220 to port 222 and the exhaust line 30 in order to initiate another deflation cycle. Thus, the timer 228 controls the duration of the inflation cycles, which may be modified by suitable adjustment of the timer 228.
A schematic diagram of another circuit for the controller 22 of the present invention is illustrated in Fig. 9. As before, the source S is connected to a two-position switch 300 through a reyulator 302 and a filter 304~ When the switch 300 is turned on, the source is connected through the switch 300 to port 306 of a shift valve 308. In a deflation configuration of the valve 308, the supply is connected through ports 306 and 310 of valve 308 to - 20 inlet port 312 of a positive output timer 314, and to port 316 of a ~econd shift valve 318. In turn, the actuated valve 318 con-nects the line 320, which communicates with the manifold and sleeve, through its ports 322 and 324 to the exhaust line 326 at this time. Accordingly,~with the shift valve 308 in this configu- `
ration, the sleeve is deflated through line 320, valve ports 322 and 324, and the exhaust line 326.
When the de~lation timer 314 times out, the supply is connected from port 310 of valve 308 through the timer 314 to port . .
:: : , ' ' .
.,~: ~ . ' ~ -lS- -328 of shift valve 308. In turn, the actuated valve 308 discon-nects its port 306 from port 310, and connects its port 306 to port 330 in order to terminate the deflation or decompression .:
cycle and initiate an inflation or compression cycle. The dura-5 tion of the deflation cycles may be modified by suitable adjust-ment of the deflation timer 314.
During the inflat.ion cycle, the supply i.s connected through ports 306 and 330 of valve 308 to inlet port 332 of a positive output timer 334, and to port 336 of the shift valve 318, In turn~ the actuated valve 318 ~isconnec-ts its port 322 from port 324, and connects the port 322 to its Port 338. Thus, at this time,.the supply is connected.through a flow control valve 340, the ports .338 and 322 of valve 318 to the line 320, in order . -to inflate the chambers of the sleeve through the manifold during the inflation cycle~ As before, the flow control valve 340 ~owers the supply pressure from the relatively high pressure required to actuate the pneumatic components of the circuit to a lower pressure for inflatin~ the sleeve. It should be noted in this . regard that the portio~ of the supply utilized to inflate the :.sleeve is connected separately from the portion of the supply .`
utilized.to actuate the pneumatic components.of the circuitry.
When the inflation timer..334 times out, the supply is .connected through ports 3D6 and 330 of valve 308 and through the timer.334:to port 342 of valve 308. In turn, the actuated val~e 308 disconnects its po~t 306.from port 330, and again connects . its .port 306 to port 310 in order to terminate the infla~ion cycle and initiate another deflation cycle. The duration of the . : :
. inflation cycles may be modified by suitable adjustment of the : . ~imer 334~
... . . . .
... . .
-'' ' - - ~. ' ' , ' ' ' ,: ',' ....
- . , ~,: . - . : .
-, . , i In summary, the compression device of the present invention intermittently forms a pressure pulse and supplies the pulse to chambers in the sleeves during periodic infla-tion cycles. At the same time, the device developes pro gressively diminishing rates of pressure increases in pro-gressively located upper chambers during periodic inflation cycles to apply a compressive pressure gradient against the patient's limb which progressively decreases from a lower -to upper portion o the limb. The device also intermittently deflates the sleeves during periodic deflation cycles between : the inflation cycles.
The foregoing detailed description is g.iven for clearness of understanding only, and no unnecessary limita-j tions should be understood therefrom, as modifications will ~e obvious to those skilled in the art.

, :

, , .
.:

. . . .

. -~17- -~ ~ , . . .

Claims (4)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A sleeve for applying compressive pressures against a patient's limb, comprising:
a pair of flexible sheets of fluid impervious mate-rial having a pair of side edges, and a pair of end edges connect-ing the side edges;
means for connecting said sheets together along lines, with said sheets intermediate the lines defining fluid impervious sidewalls of a plurality of separate pressure chambers extending laterally between said side edges, said chambers being arranged in a contiguous relationship longitudinally along the sleeve between the end edges with the volume of said chambers pro-gressively decreasing in size from one of said end edges toward the other end edge;
a third sheet of flexible material secured to said fluid impervious sheets and defining an outer surface of the sleeve relative the patient's limb; and means for releasably securing the sleeve about the patient's limb with said chambers encircling the limb, and with said one end edge being located proximal the patient's heart relative the other end edge.

2. The sleeve of claim 1 wherein said end edges are generally aligned, and said side edges are tapered from said one end edge toward the other end edge.

3. The sleeve of claim 1 wherein the securing means comprises a plurality of hook and loop fastening strips.

4. The sleeve of claim 1 including a plurality of con-nectors secured to the sleeve and communicating with separate chambers.