US20030139255A1 - Pneumatic compression device and methods for use in the medical field - Google Patents

Abstract

A multi-faceted pneumatic medical device including a pump unit. together with housing therefor, that is adapted for cyclical compression of the human foot using an expandable fluid-tight bladder formed integral within a wrap that can be securely fastened onto the foot.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention The present invention relates generally to a method and apparatus for cyclic compression of a body's extremities, as well as a related system with a housing for containing and mounting the device on the foot board of a hospital bed.[0001]
• 2. Related Art Medical devices that apply cyclic pressure to a person's legs, arms. hands and/or feet are very old and well-known in the art. Many have employed pulsating pads, pistons and plungers for improving circulation. Others have used hydraulic and pneumatic bladders for similar purposes. The shapes, sizes, and composition of such bladders, pads and the like are widely varied, depending largely on their particular application.[0002]
• Man has known the fundamental principle of most cyclic compression devices for many years. They are merely a more recent embodiment of the old art of massage, which has probably been used to stimulate circulation for ages. Use of mechanical devices to effect the massaging action is obviously more recent, but has a clear history of over a century.[0003]
• Full understanding of the mechanism involved in this form of improving blood flow is more recent but has not fundamentally changed the devices used to accomplish this result. Veins have long been known to contain a series of one-way check valves along their length. Thus, when pressure is applied, compressing a vein, the fluid expelled therefrom can only proceed in the direction of normal circulation. When such compression is relaxed, the vein returns to its normal circular cross-section and the flow of blood into the vein is increased until it reaches its normal state of back pressure. Repeating this cycle in a cyclic fashion thus increases blood flow in the normal direction of circulation.[0004]
• Such compression/decompression cycles occur naturally in humans as part of the action of the muscles and flexure of the limbs. It has been known for many decades that the foot includes a large venous plexus (or group of veins). It is also known that this venous plexus is compressed during normal walking or running, thereby stimulating circulation. This efficient circulation aid is a marvelous design by our Creator, as its effect is greatest when the leg muscles (the largest muscles in the body) are in action and need the oxygen supplied by enhanced circulation.[0005]
• For these and other reasons, the foot has long been known as an effective site for applying cyclic pressure. For instance, many devices such as Massator's “PediPulsor” improve circulation by positioning a pulsating, dome-shaped pad in the arch of the foot. Many others have targeted the arch of the foot with flexible pneumatic chambers. A partial sampling of such pneumatic devices that target the arch of the foot are described in the masters thesis of James C. W. Parrott, B. Sc., B. Sc. (Med.), M.D., entitled[0006]The Effect Of A Mechanical Venous Pump On The Circulation In The Feet In The Presenc Of Arterial Obstruction, and dated Oct. 1992 and found in the University of Manitoba library and includes Japanese Utility Model No. 72-10392, U.S. Pat. No. 4,614,180 in the name of Gardner and Fox, and U.S. Pat. No. 4,941,458 in the name of Taheri.
• Many others have long recognized that the foot contains veins that can be massaged or pumped to provide better circulation. Some examples are: U.S. Pat. Nos. 3,824,992 and 3,901,221 to Nicholson, et al; Richard Dillon M.D. whose[0007]Journal of Vascular Diseases, Jan. 1986 report on treatment of circulation-impaired patients states “compression boot therapy enjoys a 173 year history;” and P Gaskell M.D. and J. C. W. Parrott M.D. whoseSurgery, Gynecology and Obstetrics, Apr. 1978 report, which is a summary of Dr. Parrott's Master's Thesis, documented an early demonstration of the process of venous pumping with pulsed air by stating “We have found that the boot covering the foot alone is simpler, less cumbersome. and gives a greater reduction of venous pressure than either a large cuff which covers the whole calf or a boot which includes the calf and the foot.”
• Such devices and many other medical devices are typically auxiliary devices which may or may not be employed on each patient. Because of their auxiliary nature, it is beneficial for such devices to be compact, portable and easily employed and stored adjacent a hospital bed. Other devices have addressed such concerns with hooks that allow the device to be hung on the foot board of a bed. However, because of the wide range of foot board sizes that must be accommodated, such hooks either have to be customized for certain foot boards, or else the snugness and security of the fit must be compromised. Further background and many other related references are known to those of skill in this art.[0008]
• Despite the:long history of technological developments of such housings and compression devices, man continues in his manifest pursuit of the ideal system which balances maximum therapeutic benefit with practicality and patient comfort.[0009]
• Many other problems, obstacles and deficiencies faced in these fields and/or addressed by the present invention will be apparent to those skilled in that art, especially in light of the further descriptions herein.[0010]
SUMMARY OF THE INVENTION
• It is a primary object of the present invention to provide a new and improved cyclic compression system which overcomes the problems and deficiencies of the prior art.[0011]
• It is also an object of the present invention to provide a novel housing which can be conveniently handled and simply but securely mounted to a hospital bed or the like. Another object of the invention is to produce a simple, compact, inexpensive pump and housing which are capable of yielding substantial therapeutic and prophylactic benefits despite their small size and simplicity.[0012]
• The present invention is directed toward accomplishing such objects and others and improving upon the teachings of the prior art by uniquely combining. refining and modifying various concepts and features to provide a significant advancement in the field. A primary object of the invention is to provide a small, lightweight and comfortable but durable device which helps prevent and/or solve many of the problems associated with impaired or poor circulation.[0013]
• Another object includes providing a pneumatic device of simple construction which encloses as much of the foot as possible in order to squeeze as much of the foot as possible. Particularly it is an object to enclose those portions which may be readily compressed to improve circulation while allowing other less compressible portions to be open to the air. Still other objects include providing comfort and moisture control and avoiding the need for accessories such as additional stockings, wraps, sandals, straps, and the like, which have been required by the prior art.[0014]
• Another object of the present invention is to provide an intermittent compression device requiring a minimum volume of air per pulsation.[0015]
• Another object is to provide a blood circulation aid which will fit a wide variety of patients without requiring any modification or adjustments[0016]
• Another object of the present invention is to provide a disposable device of simple construction which is of a universal shape in that it can be applied to either the left or the right foot with the same effect.[0017]
• Another object is to provide a device of great simplicity and ease-of-use in contrast to other devices designed for the purpose of aiding blood flow in the feet and legs. Related objects include providing a lightweight, simple article that can be easily and quickly applied to the foot while still achieving the other objects of the invention.[0018]
• Another object of the invention is to provide a blood flow improvement device which, due to its inherent low manufacturing cost, is practical to use as a disposable item rather than cleaning and reusing.[0019]
• Still another object is to provide a cyclic compression device which achieves optimum compression and optimum blood flow enhancement in a manner that minimizes anxiety and discomfort to the patient.[0020]
• Other objects relate to the convenience of the product. It is desired to provide a complete system that can be hand carried to the patient and easily and securely deployed without concern about compatibility with the bed on which the product is to be deployed. A compact, easily-stored and minimally-obtrusive product is also sought.[0021]
• The present invention addresses the foregoing and many other objects by providing an ingenious article that integrates a compression bladder and its entire mounting, stabilizing and adjustment systems into a simple and economical construction coupled with a control system and housing that greatly surpass prior devices both in utility and ingenuity.[0022]
• The present invention will typically comprise a foot wrap device made from two sheets of fabric sewn or welded together to form an inflatable pocket or bladder that preferably constitutes as much of the device as possible without creating a bladder that is too uncomfortable or too large to be adequately inflated. One aspect of the invention relates to the roughly T-shaped or L-shaped configuration of its foot wrap, with at least one portion or segment wrapping around the bottom of the foot and a second portion or segment wrapping around the back of the heel and ankle regions of the lower leg. As will be described with reference to the preferred embodiments, the invention may include various extensions or tabs provided to operatively join with other extensions, tabs or the like, as may be beneficial for comfort and efficacy. In the preferred embodiments, both inner and outer fabric layers are cut from the same pattern.[0023]
• Fasteners formed integral with the extensions enable releasable application on the foot. Preferably, such fasteners include Velcro hook connectors, and the outer surface of the foot wrap is formed of Velcro loop material (or the equivalent) for mating with the hook connectors. The inner layer of the foot wrap is preferably a vapor permeable material having greater elasticity than the outer layer. Both fabrics are preferably impermeable to air and capable of being fused together by heat welding or the like. A filling tube may be sealed into the inflatable bladder or pocket through the outer fabric layer.[0024]
• In the first embodiment, the complete foot wrap weighs only a few, ounces and is soft and pliable. When it is properly applied, a first dimpled or segmented portion of the inflatable bladder wraps around the main part of the foot and fastens to itself. Another portion is joined integrally in fluid communication with the first but wraps around behind the heel and ankle regions of the lower leg. The second portion fastens to the outside surface of either itself or the other portion. Thus, the foot is almost completely enclosed and surrounded by the inflatable bladder, and the device securely holds itself in place on the foot in order to compress as much of the foot as feasible when the bladder is inflated.[0025]
• Fluid for such inflation may be supplied by one of the pump systems well known in the art, although the preferred embodiment includes and provides several advancements over that art. The preferred embodiment includes a pump that operates in a pulsed sequence that can be adjusted for any desired frequency and intensity according to the prescribed treatment. Preferably the pump/control is set to compress the foot to pressures in the range between 120 and 190 mm Hg and to hold it in that pressure range for two seconds every fifteen seconds. This pressure range is generally accepted by Applicant to ensure closure of the veins in the foot, although lower pressures may be partially effective as well.[0026]
• The preferred embodiments uniquely integrate more fundamental aspects of the invention together with cushioning means for minimizing localized pressure concentrations acting on the foot, thereby inhibiting skin breakdown on the foot, especially its most vulnerable areas. Optimum compression of the foot is ensured by. enclosing as much of the squeezable portion of the foot as is feasible. In the first embodiment, the inner and outer sheets are joined together at circular portions in the interior of its inflatable bladder to help prevent excessive inflation, particularly over regions of the foot that are less compressible. This further optimizes compression of the foot to ensure optimum blood flow enhancement. Holes may be provided through the wrap at those circular portions to further enhance breathability of the patient's skin.[0027]
• The present invention also includes a unique pressure source for supplying pressure to the referenced foot wraps. Pressure feedback control of the pressure supplied by the pressure source is provided even during the then-current compression cycle. The feedback system overcomes some of the difficulties inherent in its objects by incorporating spike eliminators, as well as error detection means for alarming the operator of error conditions such as kinked hoses or disconnected foot wraps. The spike eliminator may include an accumulator, possibly in combination with a flow restrictor. The accumulator and restrictor are configured in a way that helps prevent the pressure sensors from over-responding to initial surges of line pressure. Such surges are otherwise common close to the pressure source with compression devices that provide quick inflation.[0028]
• More particularly, the pressure sensing and control system may include a transducer, an analog-to-digital converter, and a digital micro-controller that controls a plurality of solenoid valves to adjust the supplied pressure in accordance with operator settings. The micro-controller is interfaced through an operator console having a liquid crystal display and programmable keys to enter operator settings, which are then stored using various memory devices including electronically erasable programmable read only memory.[0029]
• The combination of all the foregoing in an operative system is thought to be very beneficial, especially packaged in a housing that can be releasably mounted on the foot board of a standard hospital bed by means of a pair of opposite, retractable mounting hooks having sloped surfaces for biasing the source toward said foot board and having knobs at the distal ends thereof for helping retain the hooks on the foot board.[0030]
• Numerous other features, advantages, and objects of the invention are set forth and will be evident from the following more detailed descriptions of certain preferred embodiments, particularly when considered in light of the prior art together with the accompanying drawings and appended claims.[0031]
BRIEF DESCRIPTION OF THE DRAWINGS
• Presently preferred embodiments constructed according to the teachings of the present invention are hereinafter described in more detail. To those of ordinary skill in the art, the invention will become more readily understood from the specifications of those embodiments, particularly when considered in light of the appended claims and with further reference to the accompanying drawings, wherein like numerals refer to like elements throughout, and wherein:[0032]
• FIG. 1 shows a perspective view of the basic elements of one of the presently preferred embodiments.[0033]
• FIG. 2 shows the outer surface of one of the foot wraps 1A pictured in FIG. 1 as it is laid out flat.[0034]
• FIG. 3 shows a view of the inner surface of the[0035]foot wrap 1A laid flat.
• FIG. 4 shows a top view of the[0036]foot wrap 1A in place on a human foot.
• FIG. 5 shows a side view of the[0037]foot wrap 1A in place on a human foot.
• FIG. 6 shows an end-on view of the[0038]foot wrap 1A as it is laid out flat with itsbladder9 shown deflated, the view being from the end that is oriented at the top in FIG. 2.
• FIG. 7A shows a cross-sectional view from the opposite direction of FIG. 6, the section line “[0039]7A-7A” being shown in FIG. 3 andbladder9 being shown inflated in FIG. 7A.
• FIG. 7B shows a second cross-section of the[0040]foot wrap 1A, sectioned along plane “7B-7B” shown in FIG. 2, with itsbladder9 shown deflated.
• FIGS.[0041]8A-8D illustrate the manner of operatively applying afoot wrap 1A to afoot100.
• FIG. 9 shows a schematic layout of the electrical and pneumatic systems of the preferred embodiment shown in FIG. 1.[0042]
• FIGS.[0043]10-12 show flow charts which characterize the operation of the preferred embodiment shown in FIG. 1.
• FIG. 13 shows a top view of the preferred embodiment's[0044]pump housing20, which also functions as a carrying case and as a means for mounting the pump on the foot board of a hospital bed or the like.
• FIG. 14 shows a front elevation view of the[0045]pump housing20. without certain details.
• FIG. 15 shows a rear elevation view of the[0046]pump housing20.
• FIG. 16 shows a bottom view of the[0047]pump housing20.
• FIG. 17 shows a left side elevation view of the[0048]pump housing20, with retractable mounting hooks21 in their fully retracted position as in FIGS.13-16.
• FIG. 18 shows the left side elevation view of FIG. 17, except that the retractable mounting hooks[0049]21 are in their fully extended position in FIG. 18, as also pictured in FIG. 1.
• FIG. 19 shows an exploded view of the rear portion of[0050]pump20.
• FIG. 20 shows an exploded view of the front portion of[0051]pump20, illustrating many of the particular embodiments and relative configurations of the components schematically shown in FIG. 9.
• FIGS.[0052]21-23 show alternative embodiments to thefoot wrap 1A shown in FIG. 3.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
• Referring to FIG. 1 of the drawings, there is shown an isometric perspective view of the basic elements of the presently preferred embodiment. That embodiment, referred to as[0053]cyclic compression system500, basically comprises apump unit501, two foot wraps 1A & 1B,power cord24, and connectinghoses30A and30B. In many respects that embodiment is intended to be substantially identical to a product known in the marketplace as the “PlexiPulse” unit manufactured by Applicant Kinetic Concepts, Inc., San Antonio, Tex. The “PlexiPulse” unit is now available to customers of NuTech, which is affiliated with Kinetic Concepts, Inc., and also has offices in San Antonio, Tex. Although the following description is intended to be complete within itself and with reference to its corresponding Co-Pending Application (referred to previously), further reference to said PlexiPulse unit may further enrble those of ordinary skill in the art to make and use the inventions hereof.
• The[0054]pump unit501, which is AC-powered via aconventional power cord24, operates to cyclically inflate and deflatebladders9A and9B formed in foot wraps 1A and 1B, respectively, to intermittently compress the foot. The unit is described most particularly for application on the foot, as many aspects of the invention can be appreciated there. Nonetheless, regardless whether it is mounted on a patient's calf, foot, hand, or any other part of the body (especially those containing veins that can be emptied by compression), such intermittent compression may be beneficial for a wide variety of indications. Among others, the known medical indications include the following: venous stasis, poor circulation, post-operative pain and swelling, edema, cutaneous ulceration, and elevated compartmental pressures. It may also serve to prevent deep vein thrombosis and reduce wound healing times. More particular aspects of preferred operation of thesystem500 will be described further herein.
• For purposes of this description, reference may be made to “upper”, “lower”, “forward”, “backward”, “left”, “right” and “horizontal” features when referring to certain drawings. Such references and others like them are made principally to render the description more easily understood in view of the orientations in the drawings and in view of a reference orientation of[0055]system500 or its subject. As will be evident to those of ordinary skill in the art, such orientations are not necessarily maintained throughout the operation of the described embodiments, much less would they necessarily be required for utilization of the invention.
• Referring to FIGS.[0056]2-7,foot wrap 1A is shown, first laid flat and then in relation to a foot (designated asfoot100 in the drawings) during normal operation.Foot wrap 1A is preferably identical to foot wrap 1B (shown in FIGS. 1 and 9) and thus has parts which are numbered the same as in the other figures, except that the “A” and “B” designations may be used to distinguish various parts ofwrap 1A from similar parts ofwrap 1B, respectively. Variations in the shape offoot wrap 1A may be made to some degree, with commensurate sacrifices in (or enhancement of) the benefits of the invention. The angle of theinlet11 relative to thefoot wrap 1A, for instance, may be varied from one foot wrap to the next without much effect on its operation. The inlet angle pictured in FIG. 1 is considered most advantageous, tending tobias hose30A in a direction for avoiding kinking of thathose30A. The descriptions offoot wrap 1A are equally applicable to foot wrap 1B. One aspect of the invention is that the shape ofwrap 1A renders it universal in that it is thought to be applicable to either foot without significantly affecting its efficacy. As will be evident, though, thefoot wrap 1B could be made as a mirror image of itscounterpart 1A. The simplicity of the shape also allows for thewrap 1A to fit on other body portions as well even though it is ideally suited for the foot.
• In FIG. 2,[0057]foot wrap 1A is shown open (i.e., laid out flat), With the cuter surface offoot wrap1A facing the viewer. FIG. 3 is a view from the opposite side showing the inner surface of foot wrap IA. FIGS.6-7B show various views that generally illustrate the construction of the foot wrap. Thefoot wrap 1A is generally formed of twosheets2 and3 which are bonded together to form abladder9 with tabs4-7 extending generally away from each other.Foot wrap 1A also includes a fluid inlet11 (also referred to as “fitting11”) for inflating and deflating thebladder9, as well as faster8 and88 for releasably securing thewrap 1A on afoot100. These basic components (and others) ofwrap 1A are readily available through numerous manufacturers.
• Referring primarily to FIG. 7B,[0058]sheet2 is preferably cut from a robust, non-stretch fabric. The outer surface of sheet2 (i.e., the surface facing away from sheet3) has loops like those found on Velcro loop material, which are compatible to releasably engage Velcro hook material. The interior surface of sheet2 (i.e., the surface facing toward sheet3) is heat-weldable so that it can be joined tosheet3.Sheet2 is laminated with polyurethane in a conventional manner, to seal it and render it RF-weldable.Sheet2, thus, is referred to as a sheet of laminated loop fabric that forms the outer sheet ofwrap 1A. In the presently preferred embodiment,sheet2 is a Velcro-compatible, continuous-loop nylon fabric manufactured by Guilford, USA and available under the trade designation “Tricot”.
• Preferably, although each of the[0059]sheets2 and3 are air impermeable, they are each also formed of vapor permeable fabric. Other commercially-available fabrics, such as that marketed as low air loss “GoreTex” by the W. L. Gore Company, have long been known to provide similar benefits in other contexts. Their vapor-permeability serves to enable moisture fromfoot100 to evaporate despite thefoot wrap 1A. This is especially preferable forsheet3 so that perspirationadjacent bladdar9 can be evacuated from the site by the fluid that inflatesbladder9. The removal of surface moisture forming on the patient's skin beneath the foot wrap is beneficial since it helps promote the maintenance and healing of skin conditions, especially during prolonged use. As will be evident to those skilled in the art, however, some aspects of this invention can still be appreciated with materials of more limited porosity, generally so long as foot wraps 1A and 1B remain inflatable.
• [0060]Sheet3 is preferably cut from the same or a similar pattern assheet2, so that it matches neatly withsheet2. The manufacturing process may be simplified by simultaneously die-cutting thesheets2 and3, and then joining the border and appropriate other locations of each sheet to the other (as described elsewhere herein). The cutting process may also be simplified by welding the two sheets together while simultaneously heat-cutting the border of the fabric with the same die (as is common in the art with tear-and-seal dies), although this process may not always be successful due to the compositions of the sheets.
• [0061]Sheet3 is preferably also an elastic fabric, so that it expands more thanouter sheet2 whenbladder9 is inflated. The inner surface of sheet3 (i.e., the surface facing toward sheet2) is laminated with polyurethane, thereby sealing it and rendering it heat-weldable to enable bonding with the inner surface ofsheet2. It is important that the outer surface of sheet3 (i.e., the surface facing away from sheet2) is soft and comfortable against the skin, as that surface is likely to be in contact with the patient's skin during use. In the preferred embodiment,sheet3 is a laminated lycra material that meets the foregoing characteristics.
• As will be evident from this description to those of ordinary skill in the art, other fabrics may be substituted for the preferred fabrics of[0062]sheets2 and3 with related sacrifices of various aspects of this invention. Less costly, substantially inelastic nylon fabrics could be used for bothsheets2 and3 while still appreciating therapeutic value of the foot wraps 1A and 1B. Similarly, stitching or adhesives could be used rather than the more beneficial RF welding, and some benefits could still be appreciated with a PVC-like composition made of sheets appropriately welded together.
• Preferably,[0063]bladder9 is formed betweensheet2 andsheet3 byweld line10.Weld line10 is a closed line so that it completely surrounds and thereby defines a closed area on each ofsheets2 and3. Thus,bladder9 is a sealed bladder, the only inlet or outlet of which is provided by the tubular connector fitting11 (described below).Bladder9 is provided in foot wrap 1A to apply pressure on thefoot100 when thewrap 1A is secured on thefoot100 and the bladder is then inflated.Bladder9 is primarily intended for pneumatic inflation, although fluids other than air could be substituted by those of ordinary skill in the art. Althoughbladder9 would be of minimum size and volume consistent with its object of exerting compression pressure on the foot while requiring a minimum volume of pressurized air per pulse (as achieved bybladder509 shown in the alternative embodiment of FIG. 21), Applicant believes that similar pressures distributed over more of the foot provides a greater benefit for the patient. Thus,bladder9 offoot wrap 1A extends over most of the entire surface area ofwrap 1A to overlap and enclose as much of the portions of the foot which contain significant veins as is feasible. Althoughbladder9 in the preferred embodiment may not compress the veins in the toes of most patients, it is of sufficient size to compress virtually all other regions of the foot, except the most distal portion of the heels, which are thought to contain few significant veins for compression purposes.
• In contrast, it can be seen with reference to FIG. 21 that[0064]bladder509 occupies only the central sole area of thefoot100. Pressure and bladder expansion there causes the fabric enclosure around the foot to tighten and distribute limited compression forces around other portions of thefoot100 as well. In the embodiment of FIG. 21,bladder509 is circular, roughly3 to5 inches in diameter. However, other shapes of bladders may be substituted to employ many of the other aspects of the invention. For instance, FIGS. 22 and 23 show two other alternative embodiments to thefoot wrap 1A shown in FIG. 3. FIG. 22, specifically, shows a T-shapedfoot wrap401 having a similarly T-shapedbladder409 which is capable of enclosing much offoot100, with some limitations. The differences between the shape ofbladder9 andbladder409 ensure more complete enclosure of vein-containing portions bybladder9, as well as enable its universal characteristics (referenced previously). In the opposite direction from the smaller shape ofbladder409 isbladder609 shown in FIG. 23, which further ensures complete enclosure and compression of the vein-containing portions offoot100, while also further ensuring a secure attachment to foot100. Other variations and details are described in said Co-Pending Application and at least one other application referenced and incorporated therein.
• Each of the embodiments shown in FIGS.[0065]21-23 are constructed and used essentially using the same methods and materials as with the FIG. 3 embodiment, except as otherwise noted. Accordingly, like (or related) aspects of these various embodiments are numbered similarly. For instance, each embodiment has a strap that is positioned to be secured around the back of the leg of a person on which it is to be used. The respective straps are numbered7,507,407 and607, for FIGS. 3, 21,22, and23, respectively. The differences from the embodiment of FIG. 3 and those of FIGS.21-23 will be fairly evident from a comparison of those figures.
• The principal difference between the FIG. 3 embodiment and that of FIG. 21 relates to the size of the bladder. In attempts to render the[0066]wrap 1A more comfortable and more likely to ensure against skin breakdown, Applicant has found that by increasing the size ofbladder9 to that shown in FIG. 2, the resulting blood flow is improved. Although the findings are still preliminary, compressing more of the foot not only renders thewrap9 more comfortable, but informal venogram studies indicate that greater surges of blood flow tend to be produced by compressing more of the foot. The same informal studies also suggest that the placement of circular welds53-56 in the interior ofbladder9 further enhances blood flow. That cushioning effect is believed to help inhibit the breakdown of skin that might otherwise be associated withstraps507,407 and607—particularly breakdown created by stress concentrations onstrap407 and the skin around the rearward ankle area offoot100. As is also true to some degree for the embodiment of FIG. 2, the embodiment shown in FIG. 22 is provided with means for cushioning theleg strap407.
• [0067]Wrap401 achieves the cushion in part by having afoam strap407 that is inherently cushioned and in part by extending its inflatable bladder along the length of the strap507.Wrap 1A, in contrast, only achieves the cushion by extending itsinflatable bladder9 along the length of itsstrap7.Foam strap407 is an elongated patch of foam material that is secured to strap407 in an orientation coincident with the length ofstrap407. The cushion foam used in the preferred embodiments of the embodiments shown in FIGS.21-23 is commercially available in the U.S. under the trademark “Vel-Foam”, although other cushion material could also be used. Securing thefoam407 to the rest offoot wrap401 may be accomplished either by a variety of conventional means, such as by stitching, glue, or heat-welded lamination. If stitching is to be used, the stitching is preferably done at a location of the Wrap that is not inflatable, thereby avoiding leaks in the inflatable bladder. For instance. the Vel-Foam strap407 is shown stitched on three sides to the remainder ofwrap401 withstitching419 in a narrow region outsideweld410 that definesbladder409. Vel-Foam patch418 must be stitched around only three of its four edges (excludingedge418′) in order to avoid creating an air leak inbladder409. Therefore it may be preferable toglue patch418 in place using conventional glues used by seamstresses for lasting application.
• Heat-welded[0068]circular recesses417 are preferably spaced onbladder409 to minimize billowing (excessive bulging) ofbladder409 when it is inflated. Such circular recesses are best positioned at locations likely to overly bonier (or less compressible) areas offoot100.
• Many other features of the embodiments shown in FIGS.[0069]21-23 will be evident to those of ordinary skill in the art in view of the other teachings herein, and in view of the prior art.
• The preferred shape of[0070]wrap9 is unique and advantageous.Wrap9 as a whole may be referred to as T-shaped, J-shaped or L-shaped depending on which elements are focused upon. For simplicity in reference, it will simply be referred to as a “convoluted J-shape”. The convoluted J-shape ofwrap1A has four basic extensions—referred to as tabs4-7.
• Tabs[0071]4-7 are oriented to ideallysecure wrap 1A to thefoot100 of the patient. As can be seen with reference to FIGS.2-7, theheel edge6′ that spans betweentab6 andtab7 is concave and has a generally circular curve for surrounding theheel102 offoot100. Once so wrapped to encircle theheel102 offoot100,Velcro connector8 at the distal end oftab7 is naturally oriented to overlap and secure itself to the outer surface ofsheet2 oftab6. Thetoe edge4′ is also curved concavely, although only to a slight degree, to encircle thetoe region103 of thefoot100. Once so encircling the toe region of the foot,Velcro connector88 overlaps and engages the outer surface ofsheet2 oftab4. The size ofVelcro tabs8 and88 should be determined based on the degree of closure desired, which is dependent, at least in part, upon the types of Velcro materials used. Prior teachings have suggested that Velcro connectors on compression devices should be small enough to allow for release in the event of over-pressurizing an inflatable compression device; however, Applicant gives limited credence to such teachings and has found that larger tabs may be desired in order to ensure secure enclosure of the foot in normal operation. Size increases oftabs8 and88, though, should be balanced against desire not to have Velcro hock connectors overlapping to a degree that would engage the skin offoot100. Specifically, Applicant, in alternative embodiments (not shown), has utilized larger Velcro hook connectors at the location ofVelcro hook connector88 in FIG. 2, and has found that the width oftab5 can be increased to accommodate such larger Velcro connectors.
• As is evident in FIG. 2, the orientation of[0072]tab5 is substantially perpendicular to the orientation oftab7. Similarly,tabs4 and6 extend in directions generally perpendicular to one another, althoughtabs4 and6 are more rounded at theirdistal ends4″ and6″ than aretabs5 and7. The distal ends4″ and6″ oftabs4 and6 are inflatable in the preferred embodiments; whereas the distal ends5″ and7″ oftabs5 and7 are not inflatable and are provided withVelcro connectors8 and88 stitched thereto, respectively. Distal ends5″ and8″ are also considered squared relative to the morerounded ends4″ and6″. In use, the uppermost edge ofwrap 1A is provided byedge5′ which spans betweentabs5 and7. Unlike each of the other edges,5′,6′ and8′ that span between tabs4-7,edge4′(spanning between the distal ends4″ and6″) has a convex shape, although only slightly so. The inflatable ends4″ and6″ oftabs4 and6 are also convex, although more so thanedge4′.
• A blank (i.e., non-inflatable)[0073]central portion5′″ is provided at the proximal end oftab5, in the part ofwrap 1A spanning betweenweld10 andconnector88. The purpose of blankcentral portion5′″ fortab5 is to ensure thatconnector88 adequately overlapstab4 on varying sizes of feet (thereby ensuring against contact between the Velcro hooks ofconnector88 and the skin of foot100), while also limiting the size ofbladder9 by not extending it over blankcentral portion5′″. The balance was drawn principally because thetab5 is sized such that blankcentral portion5′″ will overlap tab4 (which is already inflatable) in most applications. The position ofinflatable extension7 is oriented relative to the rest ofwrap9 to wrap around more or the vein-containing portions of a patient's lower leg, as opposed to right around the back of theheel102 andankle104 ofleg105.
• Referring especially to FIGS. 1, 6 &[0074]7, fitting11 is a tubular fluid connector having an elbow form to reduce the extent of protrusion fromsheet2. Its elbow shape also enables connection of afluid hose30A (shown in FIG. 1) to the fitting11 and helps minimize the possibility of kinkinghose30A during use. A conventional,barbed hose connector18 is incorporated in the outermost end of fitting11 to enable connection withhose30A, although a properlysized hose30A could also be connected merely by a friction fit with fitting11. Fitting11 is formed of a compatible heat-weldable material and has abase flange12. This fitting is inserted from the inside ofsheet2 through ahole12′ punched infabric sheet2 and is then positioned so thatflange12 contacts the heat-weldable inner surface offabric sheet2. The engagement betweenflange12 andsheet2 is then welded fluid-tight to completely seal thebladder9A from leakage.
• As suggested above, tabs (or “extensions”)[0075]4-7 extend generally away from each other. Withwrap 1A laid flat,tabs5 and4 lie on opposite sides ofwrap1A, extending generally along the line “7A-7A” in FIG. 3. Extension ortab7 offoot wrap 1A lies substantially perpendicular to line “7A-7A” and is considerably longer thantab5. In other embodiments (not shown),tab7 is less perpendicular than pictured in FIGS.2-7.Hook connector patches8 and88 are sewn or welded at or near the distal ends of5″ and8″tabs5 and7, respectively, on the outer surface ofinner sheet3.
• As shown best in FIGS. 2 and 3, the convoluted J-shape of[0076]bladder9 includes circular recesses53-56 in the midst ofbladder9. Such recesses53-56 combine with other features ofbladder9 to optimize compression offoot100. Particularly, recesses53-56 are oriented to minimize excessive billowing ofbladder9, particularly over the less compressible areas of each lateral side offoot100.Inflatable tabs4 and6 remain inflatable despite recesses53-56 to provide compression of other regions of the foot. The preferred positions and orientations of recesses53-56 are best evident in the FIGS. 2 and 3 of the drawings.
• In part by[0077]weld10 and elsewhere bywelds10, theouter perimeter14 of theentire foot wrap 1A is RF-welded to joinsheets2 and3, thereby forming acomposite fabric wrap 1A with the singletubular fitting11 mounted therein. Such simplicity is in striking contrast to the large and complex foot wraps heretofore employed for similar purposes. This preferred embodiment weighs less than6 ounces and is approximately38 centimeters in the direction of line “7A-7A” of FIG. 2 by 39 ½ centimeters in the perpendicular direction of line “7B-7B”. Other forms of connecting the sheets may be used, such as by stitching, although commensurate sacrifices of inventive aspects will probably be associated with such a change.
• Referring to FIGS.[0078]8A-8D,foot wrap 1A also stands out for its ease and simplicity of use. First place the foot wrap in the flat position shown in FIG. 8A and place thefoot100 over the central portion ofbladder9.Foot100 should be positioned onbladder9 in a way such that the center ofheel102 offoot100 is positioned just off ofbladder9 and inside the arc ofheel edge6′. The length offoot100 should extend acrossbladder9 in a direction parallel to the length oftab7, in a path directly betweencircular welds55 and56, such that the foot lies in contact withinner sheet3 ofwrap 1A. Then, as in FIG. 8B, wraptab4 and6 around thefoot100, withtab6 naturally following and extending toward the back of theleg105.Tab4 should wrap over the top of thefoot100. Then wraptab5 overtab4 as in FIG. 8C, sotabs4 and5 overlap on the top of the foot. Adjust the tightness of the fit to the degree desired (preferably snug) and press thehook patch88 oftab5 onto the outer surface oftab4 so they form a secure connection. Then, to completely secure thebladder9 to thefoot100,draw tab7 around the back of thefoot100 as shown in FIG. 8D and pull it snug. Hooked tip8 (shown in FIG. 8A) is then pressed onto the outer surfaces oftab6 where it overlaps on the side of thefoot100. Thefoot wrap 1A is now locked in position until thefastenings8 and88 are peeled open for removal of thefoot wrap 1A. This procedure can be accomplished in a few seconds, and removal requires only pulling of the twotabs5 and7.
• Minor adjustments in the preferred position of the[0079]bladder9 relative to thefoot100, if required, may include loosening and repositioning one or bothtabs5 and7 as necessary. The relative lengths oftabs4,5,6 and7 are not fixed but must meet the requirement of overlapping sufficiently to form a secure fastening when wrapped aroundfoot100. Thustab4 may be shorter thantab5, although the general proportion illustrated in FIGS.1-8 is preferred. Thefoot wrap 1A will fit a wide range of foot sizes without change in the application technique. If necessary, feet of very small persons may be fitted through the use of firm padding above the instep and behind the heel to simulate a larger foot while allowing the bladder to act against the sole of the foot through the padding.
• The size and shape of the[0080]bladder9 andfoot wrap 1A in relation tofoot100 may also be larger than shown, even enclosing the entire foot, while still appreciating many aspects of the invention. Although not included in the pictured embodiments in view of the objects of reducing complexity, size, weight and material cost, among others it is preferred to provide a bladder which fully encloses the foot or, perhaps more practically, extends to just enclose the toes of the feet. However, larger capacity pumps and/or slower cycle times must be employed with such alternative embodiments in order to compensate for the bladders having larger volumes.
• Nonetheless, without encompassing the entire foot, air and foot moisture vapor can exchange between the foot and the foot wrap from both the front and rear areas where the[0081]foot wrap 1A wraps onto thefoot100. Circular recesses53-56 are also provided withholes53′-56′ in the central portions thereof to provide for greater ventilation for thefoot100.Such holes53′-56′ may be punched, cut or die-cut central to circular welds53-56 in the same or similar manner to the formation of theouter perimeter10′ offoot wrap 1A.
• During the deflated phase of pumping, the fit is looser and air can more easily diffuse the covered areas of skin beneath the[0082]foot wrap 1A. With proper materials as in the preferred embodiment, such diffusion is not as critical though, because the material ofsheet3 is vapor permeable—allowing moisture to vacate the skin surface throughsheet3. The soft inner surface offoot wrap 1A, which is also the outer surface ofsheet3, may be covered with a springy, open pile or other lining which promotes the entrance of air into the area betweensheet3 and thefoot100 during the decompression phase. An alternative embodiment of the invention may use a non-vaporpermeable sheet3 having an outer surface with such air movement promoting characteristics.
• This small, lightweight,[0083]inexpensive foot wrap 1A in itself is sure to fill an important need in modern medicine. Nonetheless, as will be evident from this description to those of ordinary skill in the art, many aspects of this invention may be appreciated with other compression devices, possibly in combination with other intermittent or sequential compression features or devices, and possibly employed on other parts of the body including the hand, the leg, the arm or combinations thereof—naturally, with commensurate sacrifices of certain aspects of this present invention.
• Referring again to FIG. 1, the[0084]housing20 ofunit501 will be discussed briefly.Housing20 is an injection molded plastic housing that comprisesfront housing plate27 and backhousing plate26 fastened together using any conventional means such as screws.Front housing plate27 and backhousing plate26, once connected, form handle23 which facilitates carrying ofpump unit501. The preferred embodiment'spump unit501 as a whole weighs roughly ten pounds, although the shape ofhousing20 is ideal for units of any weight that can be safely hand-carried and supported on the foot board or headboard of a patient-supporting bed. The components inside thepump unit501 are preferably arranged so the center of gravity for thepump unit501 is roughly concentric with the volumetric centroid of thehousing20, although great care need not be taken in this as long as the center of gravity is appreciably below the height where the hooks21 rest on thefoot board600. Such a location is preferred in order to distribute the weight ofunit501 between its two mountinghooks21A and21B and to ensure the unit is not top-heavy, both for ease in carrying and stability in mounting. The shape ofhousing20 and the relative positioning ofhooks21A and21B naturally help ensure that the center of gravity is centrally located.
• Referring still to FIG. 1 and also to FIG. 9, where more detailed features of[0085]system500 are shown schematically,power switch66 turns the pump unit501 (and thus thesystem500 as a whole) on and off.Power cord24 is a conventional power cord for providing standard115/120 volt,60 Hz power to thepump unit501. Preferablycord24 is a hospital grade cord.
• The links between[0086]pump unit501 and foot wraps1A and1B are principally pneumatic. Right and lefthose connectors22A and22B are the female members of conventional quick-disconnect air line connectors.Connectors22A &22B are firmly secured tofront plate27 ofhousing20 to provide a connection inlet fromfoot pump housing20 to therespective air hoses30A and30B of right and left foot wraps 1A and 1B. The ends ofhoses30A and30B that connect tohousing20 are adapted with integralmale connectors31A &31B for easy mating withconnectors22A &22B. Connection and disconnection ofconnectors31A and31B can be done easily with one hand and little effort. The connections betweenhoses30A &30B and inlets11A &11B are completed with conventional barbed line connectors18A and18B.Connectors18A and18B provide relatively permanent, sealed connections for keeping the hoses30 and wraps 1A & 1B integral.
• [0087]Operator console42 provides a user interface to the microprocessor ofunit501, allowing the user to either enter individual settings from a selection menu (discussed further herein) or select default settings.Operator console42 basically comprises an LCD (liquid crystal display)assembly46 formed in a membrane panel.LCD assembly46 comprises a two-line, twenty character alphanumeric liquid crystal display which displays programming instructions, status updates, and alarm messages to the operator. The membrane panel ofconsole42 has integral switches43-45 therein, namely: “PULSE ON/OFF”switch43; operator selection switches44A,44B,44C respectively designated “A”, “B” and “C”; and “OPTIONS”switch45. As will be evident to those of ordinary skill in the art, other switch configurations and/or options may be substituted within the scope of this invention. For instance, in one alternative embodiment the “PULSE ON/OFF” feature has been eliminated and switch43 has been dedicated to silence any alarms, with appropriate labeling ofswitch43. To eliminate that feature, thesystem500 will always be in the air pulse therapy mode (see below) when the system is empowered, i.e. whenmain power switch66 is ON.
• The operation of[0088]system500 is primarily controlled by the primary processor ofpump unit501, which ismicro-controller41.Micro-controller41 is a conventional type of control board. As will be evident to those of ordinary skill in the art, the specific characters ofmicro-controller41 are dictated by its intended operation, as described and evident further herein and in said Co-Pending U.S. Application (and other references included therein).
• PULSE ON/[0089]OFF switch43 both selects and de-selects an air pulse therapy mode for thesystem500. If PULSE ON/OFF switch43 is depressed to its ON state when themain power switch66 is Off, thesystem500 remains inoperative, but if PULSE ON/OFF switch43 is depressed ON when the main power switch is ON, the controller ofsystem500 causes delivery of pneumatic pulses to the foot wraps 1A and 1B according to the currently set operating parameters. Whensystem500 is turned on, such parameters are preset to default to the last entered parameters, but they can be adjusted at any time thereafter by appropriate selection of the OPTIONS switch45 and operator selection switches44A-C when themain power switch66 is ON, regardless whetherswitch43 is actuated. Turning the PULSE ON/OFF switch43 OFF during operation will turn off compression/decompression cycling.
• The remaining basic components of[0090]pump unit501 are shown schematically in FIG. 9, including without limitation: GPDUPower Distribution Board49,power supply board51, andair control board50. On the pneumatic side, theunit501 basically includes:compressor38,compressor cooling fan36,accumulator37, two normally-closedinflation solenoid valves36A &36B, two normally-openeddeflation splenoid valves32A &32B, manifold35, air hoses therebetween, and various other lesser components which will be clear from the drawings, particularly in view of the following more detailed descriptions of the operation ofsystem500.
• The operating protocol of[0091]operator console42 will now be described. When themain power switch66 for thesystem500 is first turned ON, the micro-controller41 (FIG. 9) displays a query on the top line ofLCD assembly46 requesting the operator to indicate whether there is a new patient. The bottom line ofLCD assembly46 displays the choices “YES” or “NO” above operator selection switches44A or44B, respectively. Upon selection of “YES” by depressingswitch44A, the operator has5 seconds to depress OPTIONS switch45 (discussed herein). Otherwise,micro-controller41 automatically stores the default values for the pump's settings (discussed herein) fromROM52 into RAM47 (see FIG. 9). A selection of “NO” or no selection within30 seconds causesmicro-controller41 to retrieve from the power down memory (discussed herein) the settings stored in memory when the unit was last powered off.
• A depression of “YES” followed by a depression of OPTIONS switch[0092]45 displays for user selection the first configuration (or “menu”) option (see Table1) on the top line ofLCD assembly46. Each subsequent depression of OPTIONS switch45 sequentially displays a different configuration option for selection by the user (see Table1). The bottom line ofLCD assembly46 simultaneously displays a selection of up to three choices for the configuration option displayed in the line immediately above. Those choices are displayed spaced across the second line ofLCD assembly46 with each choice centered above a corresponding operator selection “programming”switch44A-44C. The operator enters a choice by depressing theoperator selection switch44A,44B, or44C that is directly beneath the appropriate display corresponding to the desired selection. Depression of operator selection switches44A-44C appropriately signalsmicro-controller41 to select the specified choice or query the operator for additional information. Therefore, by progressing through the display “option” menus and selecting the desired option parameters, the system operator may program all the options required for use during the operating session. However, if default values are selected, (note that values are always stored in power down memory) the default settings preferably are: both feet selected, cycle time 15 seconds, hold time 2seconds, and left and right pressure levels of150 mm Hg. Other default combinations, such as150 mm Hg on both feet for a 3-second hold, with a 20-second cycle time have also been used with favorable results.
• Table 1 discloses the menu selection options and the parameters available for use in the preferred embodiment of the present invention. Whenever the option selection process is complete, and whenever the “HOME” option is selected, the LCD display returns to one of three HOME displays as appropriate. The three HOME displays on the first line are: “Left and Right Pulse ON”, “Left Only-Pulse ON”, and “Right Only-Pulse ON”. The second line of each HOME display has only one option—“(OFF)”—positioned above[0093]switch44C. Selection of “(OFF)” deactivates the foot compression features ofsystem500 and the “ON” and “(OFF)” LCD displays are changed to “OFF” and “(ON)”, respectively.

  TABLE 1
  MENU SELECTION OPTIONS IN THE ORDER DISPLAYED

  Option	Description
  Foot Pulse Select	Displays and allows the operator to select
  	either one or both feet for pulse therapy.
  Cycle Time Adjust?	“DECR INCR HOME”
  	allows the operator to select the foot pump's
  	cycle time; when both feet are selected, cycle
  	time is total time required for foot wraps 1A
  	and 1B (see Figure 9) to sequentially inflate,
  	hold, and deflate; cycle times range from 10
  	to 60 seconds, user selectable in 10 second
  	intervals.
  Hold Time Adjust?	“DECR INCR HOME”
  	permits the operator to adjust the amount of
  	time that the pressure is maintained in the
  	respective foot wrap after inflation occurs;
  	selections are 1, 2, 3, 4, and 5 seconds.
  Left Foot Pressure Adjust?	“DECR INCR HOME”
  	permits the user to adjust the foot pressure
  	level in the left foot wrap fromlevels 2
  	through 10.
  Right Foot Pressure Adjust?	“DECR INCR HOME”
  	permits the user to adjust the pressure level
  	in the right foot wrap fromlevels 2
  	through 10.
  View Timers?	“LEFT RIGHT HOME”
  	allows the operator to view the foot pump's
  	total therapy and operating times (Note that
  	left and right foot therapy times are
  	individually displayed).
  For Service Use Only	used by maintenance personnel to calibrate
  	the foot pump.

• The pressure levels corresponding to the range of[0094]levels 2 to 10 in the first embodiment are roughly 25-200mm Hg, although changes may be implemented within the scope of this invention. For instance, one alternative would be to change the selectable range to 1-5, corresponding to actual pressures from 120 to 190 mm Hg. For the purposes of disclosure, the timing and pressure setting ranges along with the system default settings of the preferred embodiment of the present invention have been described. The variability of such settings is highly beneficial. However, one of ordinary skill in the art will readily recognize that other ranges and default settings could be substituted.
• Referring to both FIGS. 9 and 20, the preferred system component configuration and operation will be discussed in more detail. Foot wraps 1A and 1B, designed to be securely fastened to a human foot, are constructed from two sheets of fabric sewn or welded together to form an inflatable bladder[0095]9 (described above). Alternative compression devices which are known in the art (such as compression sleeves or gloves) also could be used to appreciate many aspects of the invention.
• [0096]Power cord24 delivers the overall system power supplied from the standard 115V/120V, 60 Hz source to GPDUpower distribution board49 and, in turn, to Powersupply board51.Power supply51 converts the standard 115V/120V AC to 12V DC and supplies the 12V DC back topower distribution board49.Power distribution board49 distributes the 115V/120V AC and the 12V DC to each component according to the electrical lines pictured in FIG. 9 and according to each particular component's power requirements.
• [0097]Compressor38 provides the compressed air which is necessary to inflate theinflatable bladders9A and9B formed in foot wraps 1A and 1B.Accumulator37 stores the compressed air generated bycompressor38 before delivery to foot wraps 1A and 1B.Micro-controller41 polls PULSE ON/OFF switch43 to determine whencompressor38 should be turned on or off. In the presently preferred embodiment. the compressor is always running. When the pressure inaccumulator37 reaches its maximum,compressor38 simply turns the air without being capable of pumping it. Nonetheless, thesystem500 could be modified such that the pressure requirements of the system factor in determining the operation ofsolenoid valves32 and36.Compressor38 is turned on and off with thesystem500 as a whole by actuation ofswitch66.Fan36 also operates to continually supply a flow of air overcompressor38 to prevent it from overheating.
• In operation of the preferred embodiment, the operator may select either the right foot, left foot, or both feet for foot pulse therapy. As described before, such a selection is enabled by[0098]micro-controller41 andconsole46. If both feet are selected for therapy, foot wraps 1A and 1B alternately inflate and deflate to provide pressure against a patient's foot. However, for the purposes of disclosure, only operation of the right foot wrap will be described. However, it is to be understood that the left foot wrap operates in the same manner. In this description, the numeral designations “A” are sometimes left off the reference numerals in order to enable easier reading on either the left or right foot wrap systems.Right solenoid valve36A opens to inflateright foot wrap 1A by allowing air pressure fromaccumulator37 to be directed intomanifold35.Manifold35 simultaneously directs that air pressure to each of: (a)right foot wrap 1A viahose28A,quick connect22A, andexternal hose30A (shown best in FIG. 1); (b) rightvent solenoid valve32A; and (c) right footwrap pressure sensor40A viasensor hose29A, which has restrictor34A andexpansion tank33A along its course. Whilefoot wrap 1A is being inflated (and thereafter through the hold time) to the selected or default pressure,right solenoid valve36A is held closed, thereby maintaining the air pressure infoot wrap 1A. After the operator-selected or default hold time elapses, rightvent solenoid valve32A opens, discharging the air fromfoot wrap 1A. The above cycle then repeats after the cycle time (i.e. the time between inflation) elapses.
• The controller divides solenoid operation into four modes, as shown below:[0099]

  	Pre-inflate	Inflate	Hold	Deflate

  	INFLATE	OFF	ON	OFF	OFF
  	DEFLATE	ON	ON	ON	OFF

• An initial surge of compressed air occurs when[0100]right solenoid valve36A is first opened. If right footwrap pressure sensor40A measures the initial surge of air, an erroneous pressure measurement would occur. That is,right pressure sensor40A would measure the pressure level as being much higher than it actually is inbladder9A. To preventright pressure sensor40A from measuring such an initial pressure surge, the air flow path toright pressure sensor40A containsright restrictor34A andright expansion tank33A.Right restrictor34A restricts the flow of compressed air intoright expansion tank33A, thus decreasing the flow rate of the compressed air.Right expansion tank33A provides an increased volume for expansion of the compressed air. As the initial air surge expands intoright expansion tank33A, the air pressure decreases. Therefore, when right footwrap pressure sensor40A measures the initial surge of air pressure, that measurement approximates the actual pressure being delivered fromcompressor38 viaaccumulator37 rather than the initial surge. Hence, the combination ofrestrictor34A andtank33A (and to an extent, each of them individually) serve as means for eliminating spikes in the pressure feedback sensed bysensor40A.
• Right foot[0101]wrap pressure sensor40A, a conventional pressure transducer in the preferred embodiment, converts the pressure delivered toright foot wrap 1A fromaccumulator37 into an electrical signal representative of that pressure. An amplifier and an analog-to-digital (A/D) converter (not shown) onair control board50 convert that electrical signal to a digital signal readable bymicro-controller41.Micro-controller41 then processes that pressure signal and sends solenoid control information to solenoid drive circuits (located on control board41). Those drive circuits then control right solenoid inflatevalve36A and rightvent solenoid valve32A. Control of the solenoid inflatevalve36 and vent solenoid valve32 bymicro-controller41′ will be discussed herein with reference to the flow charts shown in FIGS.10-12.
• [0102]Pressure transducer40C is identical totransducers40A and40B but is provided to sense the pressure inaccumulator tank37—not foot wraps 1A or 1B. Specifically, the air port ofsensor40C is in direct fluid communication withtank37 through sealedline337. The ultimate function ofsensor40C is to sense the drop in pressure after each opening operation ofvalves36A or36B, thereby givingcontroller41′ an indication of whether air is flowing freely out oftank37.Micro-controller41′ uses that pressure reading for diagnostic display and audible alarm purposes.Micro-controller41′ determines if the pressure is too low, based on a digital signal from the A/D converter associated with the appropriate pressure transducer40.Micro-controller41′, in combination with thepressure transducer40C, thus, serves as a means for detecting errors in the operation ofsystem500 in its preferred embodiment—specifically errors due to obstruction in air flow to (and thus from, as well) the foot wraps 1A and 1B. If eitherline28A or28B are kinked, the pressure intank37 will not drop after opening therespective valve36A or36B. Ifcontroller41′ determines the pressure drop sensed bysensor40C does not exceed a threshold level corresponding to roughly 5mm Hg for five consecutive cycles, thecontroller41′ concludes there is a kink inline28A or28B and signals an audible alarm and visual alarm. In more detail, if the pressure drop after valve opening is too low,microcontroller41′ increments an error counter.Micro-controller41′ determines if the error counter is greater than or equal to a value of five. Then, if the error counter is greater than or equal to five,micro-controller41′ turns on an audible alarm, although thepump unit501 continues to operate as before. As will be apparent to those of skill in the art, A/D converters (not shown) are associated with eachsensor40A-40C to enable interface withcontroller41′.
• Referring to the flow chart shown in FIGS.[0103]10-12,micro-controller41′ control of the preferred embodiment of the present invention will be described. Preferably,micro-controller41′ is a conventional micro-controller such as Signetic's800552 controller, which has one RAM chip47 (along with other conventional components) integral therewith. After the power is turned on by depressingswitch66,micro-controller41′ actuates an initialization signal to its hardware components including the circuits controlling thecompressor38, thesolenoids32 and36, anddisplay46. Instep103,micro-controller41 places zeros in the variables contained in random access memory (RAM)47. When the foot pump is powered down, its present configuration settings, referred to as power down settings, are stored inEPROM48 and may be used as default settings for the next power up. Accordingly, instep104, the power down settings stored inEEPROM48 are read and stored inRAM47.
• Sequential polling of PULSE ON/[0104]OFF switch43, operator selection switches44A,44B, and44C, and OPTIONS switch45 occurs every 25 milliseconds, as shown in steps105-111. Step106 informsmicro-controller41′ to start its polling withswitch1. Instep107,micro-controller41′ stores the state of the polled switch inRAM47 and instep108 compares that state with its previous state. If the switch has changed states,micro-controller41′ advances to step109 and executes the selected switch function and stores the operator setting or default setting retrieved from ROM52 (actually a conventional EEPROM in the preferred embodiment) intoRAM47.Micro-controller41′ then advances to step110. Alternatively,micro-controller41′ advances directly to step110 if the switch did not change state. Instep110,micro-controller41′ determines if the last switch has been polled. If the last switch has not been polled.micro-controller41′ increments to the next switch instep111 and returns to step107 where it reads the state of that switch. Once all the switches have been polled,micro-controller41′ advances to step112.
• In[0105]step112,micro-controller41′ reads the settings from a status register located inRAM47 to determine which foot (if either) will be processed for the current cycle. If Pulse is switched OFF,micro-controller41′ advances to step127 and updates the operating time meter, which records total operating time. Instep128,micro-controller41′ actuates signals to bothpower distribution board49 andpressure control board50 to controlunit501. More specifically, in response to the signals ofstep128,power distribution board49 turnscompressor38 on or off, andpressure control board50 energizes or de-energizes (as necessary) the inflatesolenoid valves36A and36B and/or thevent solenoid valves32A and32B. Instep129,micro-controller41′ refreshes the present display ofLCD assembly46 as necessary. After updating the display onLCD assembly46,micro-controller41′ returns to step105 to continue the present foot function mode. This loop is repeated every 25 milliseconds.
• The four foot function modes will now be discussed. This path is followed anytime that PULSE is switched ON.[0106]Micro-controller41′ sequentially and repeatedly advances through the following foot function modes: deflate to pre-inflate, pre-inflate to inflate, inflate to hold, and hold back to deflate. The vent valve and the inflate valve in the preferred embodiment are identical body-ported three-way solenoid valves. The vent solenoid valve is fluidly connected to be normally opened, and the inflate solenoid valve is connected to be normally closed. In the deflate mode, the vent solenoid valve corresponding to the inflated foot wrap opens releasing any air pressure in the inflatable bladder. The pre-inflate mode causes the normally opened vent solenoid valve to close, while the inflate solenoid valve remains closed. Then during the inflate mode, the inflate solenoid valve corresponding to the foot wrap that is to be inflated is opened, allowing air pressure to fill the inflatable bladder while the vent solenoid is held closed. After each inflate mode, the opened inflate solenoid valve closes while the vent valve remains closed, thus maintaining the air pressure in the foot wrap during the hold mode.
• The above cycle continuously repeats during foot pump operation. However, when the[0107]pump unit501 is initially turned on, the beginning inflate modes operate under a ramping function. The ramping feature is beneficial because the pressure sensation delivered to a patient's foot during the first few inflate modes may startle the patient. Accordingly, the ramping feature reduces patient alarm by allowing the patient to gradually become acclimated to the pressure pulses delivered to the patient's foot. Upon system start-up, the initial pressure in the first inflate mode is low because the inflate solenoid valve is only briefly energized (25 milliseconds in the preferred embodiment). During each subsequent inflate mode, the inflate solenoid valve energization time increases by 25 milliseconds until that energization time reaches the operator selected or default pressure level, and the foot pump is delivering the desired pressure to the patient's foot, Other embodiments include ramping feature inflate times starting at 100 milliseconds and increasing by 50 millisecond increments.
• Again referring to step[0108]112, if the left or right foot is selected,micro-controller41′ advances to step113 and reads the value of the foot function counter. The value stored in the foot function counter represents the time remaining for the foot function in progress. Foot functions include inflate, hold, deflate and pre-inflate. Each foot function counter value is determined on the basis that micro-controller41′ requires 25 milliseconds (in the preferred embodiment) to execute steps105-129, thereby completing one processing loop, which includes a foot function counter decrement (step115). For example, if the user selects a one second hold time,micro-controller41′ places a value of40 in the foot function counter.Micro-controller41′ enters that value into the foot function counter at the beginning of a hold function because40 loops through steps105-129 equals one second (40loops times25 milliseconds equals 1000 milliseconds, or one second). Therefore, asmicro-controller41′ decrements the hold mode foot function counter during each pass throughstep115, the inflate solenoid valves and vent solenoid valves will remain closed for one second.
• The hold, deflate, and pre-inflate modes have fixed foot function counter values corresponding to each operator or default time selection as calculated above. However, because of the pressure ramping feature, the inflate mode foot function counter begins at 1 (corresponding to a real time of 25 milliseconds) and is incremented by 1 during each subsequent inflate mode until the desired pressure is reached. Thus, the solenoid valves remain open an additional 25 milliseconds through each subsequent inflate cycle. Once the desired pressure is achieved.[0109]micro-controller41′ no longer increments the inflate mode foot function counter.
• Although for the purposes of a preferred embodiment,[0110]micro-controller41′ requires 25 milliseconds to perform the functions disclosed in steps105-129, one of ordinary skill in the art will readily recognize that any delay time could be properly substituted. Variations on the ramping feature could also be substituted. As an example that other embodiments are being adapted to include solenoid energizing time at 100milliseconds is initiating inflation and incrementing it by steps of 50 milliseconds (as opposed to the 25/25 times described previously).
• In[0111]step113, if the foot function counter is not zero,micro-controller41′ advances to step115 and decrements the foot function counter by 1.Micro-controller41′ then advances to step118. If the foot function counter is zero,micro-controller41′ has completed a foot function inflate, hold, deflate or pre-inflate. Accordingly,micro-controller41′ advances to step114 and increments to the next foot function and places the value corresponding to that foot function into the foot function counter. Next, instep116,micro-controller41′ determines whether the present foot function is in the inflate mode. If the foot function is in the inflate mode,micro-controller41′ advances to step117 and increases the previous foot function inflate count by 1 (corresponding to 25 milliseconds) for use during the next inflate cycle. However, if the inflate mode has reached the user selected or default pressure as determined in step120 (discussed herein),micro-controller41′ will not increment the foot function counter. If the foot function is not in the inflate mode,micro-controller41′ advances directly to step118.
• In[0112]step118,micro-controller41′ determines whether the foot function is in the deflate, pre-inflate, hold, or inflate mode. If instep118, the foot function was in the inflate mode, microcontroller reads a pressure signal from the respecting pressure sensor and advances to step120. Instep120,micro-controller41′ determines if the pressure in the foot wrap is too high. That is,micro-controller41′ determines if the foot wrap pressure has exceeded the operator selected or default pressure. If the measured pressure is below the operator selected or default pressure,micro-controller41′ advances to step127 and updates the operating time meter. Instep128, if the solenoid valve corresponding to the foot wrap to be inflated is de-energized,micro-controller41′ energizes it viapressure control board50. However, if thesolenoid valve36 is already energized,microcontroller41′ rewrites the energization signal to pressurecontrol board50. (Note that the vent solenoid status is updated as well.)Micro-controller41′ then updatesLCD assembly46 and returns to step105 to continue the present foot function.
• However, if, in[0113]step120,micro-controller41′ determines that the actual pressure is above the desired pressure, it advances to step122. Instep122,micro-controller41′ increments to the next foot function (hold in this case) and places the foot function counter value corresponding to that foot function in the foot function counter.Micro-controller41′ then updates the operating time meter instep127. Instep128, micro-controller de-energizes, viapressure control board50, the inflate solenoid valve that had been energized during the inflate mode. The vent solenoid status is updated as well. Next,micro-controller41′updates LCD assembly46 and returns to step105 for execution of the next foot function mode.
• Micro-controller[0114]41′ is provided with two methods in the inflate mode to stop compressed air delivery to the foot wraps. First,micro-controller41′ monitors the pressure developed in the foot wrap during inflation, and if that pressure exceeds the operator selected or default pressure value,micro-controller41′ immediately increments to the next foot function and closes the energized solenoid valve (steps120,122 and128). Alternatively, if the air pressure ever exceeds the desired pressure,micro-controller41′ delivers compressed air for the incrementing interval defined in the foot function counter. That is,micro-controller41′ allows inflation of the foot wrap until the inflate mode foot function counter is decremented to zero. Once the foot function counter reaches zero,micro-controller41′ increments to the next foot function and de-energizes the energized solenoid valve, thereby stopping air pressure delivery to the foot wrap. Thus,micro-controller41′ stops compressed air delivery to the foot wrap when either the inflation pressure exceeds the user specified or default value, or the inflate mode foot function counter reaches zero, whichever occurs first. (As noted earlier in this document, the inflate time valve in the preferred embodiment is ramped up in 25 millisecond intervals.)
• Again referring to step[0115]118, if the foot function is in the hold mode,micro-controller41′ advances to step119 and determines whether at least ¾ of a second of the hold time has elapsed. If at least ¾ of a second of the hold time has not elapsed,micro-controller41′ advances to step127 and updates the operating time meter. Instep128, if the inflate mode foot function counter was completely decremented to zero,micro-controller41′ will de-energize viapressure control50 the solenoid valve energized during the preceding inflate mode. However, if the inflate mode was ended because the air pressure in the foot wrap became too high, the energized solenoid will already have been de-energized, andmicro-controller41′ will only rewrite the de-energization signal.Micro controller41′ then updates the display onLCD assembly46 instep129 and advances to step105 to continue the present foot function mode.
• If the elapsed hold time is equal to ¾ of a second,[0116]micro-controller41′ reads the pressure value measured by the respective pressure sensor and advances to step121. Step119 provides a ¾ of a second delay before pressure measurement to permit the air pressure in the foot wrap to settle so that the pressure sensor makes an accurate pressure reading.Micro-controller41′ uses that pressure reading far diagnostic display and audible alarm purposes. Instep121,micro-controller41′ determines if the pressure is too low, based on a digital signal from the A/D converter associated with the appropriate pressure transducer40.Micro-controller41′, in combination with the pressure transducer40, thus, serves as a means for detecting errors in the operation ofsystem500 in its preferred embodiment. If the pressure is toolow micro-controller41′ advances to step123 and increments an error counter. Instep124,micro-controller41′ determines if the error counter is greater than or equal to a value of 5. If the error counter is greater than or equals to 5,micro-controller41′ turns on an audible alarm instep125 and advances to step127. Although the audible alarm sounds, thepump unit501 continues to operate, and no changes are made. Instep127,micro-controller41′ updates the operating time meter. Instep128,micro-controller41′ rewrites the present actuation signals topower distribution board49 andpressure control board50. Instep129,micro-controller41′ updates the display as necessary onLCD assembly46 and returns to step105 to continue the present foot function mode. However, if the error counter is below 5,micro-controller41′ advances directly to step127 without turning on the audible alarm. In steps127-129,micro-controller41′ updates the operating time meter, rewrites the actuation signals topower distribution board49 andpressure control board50, and updates the display as necessary onLCD assembly46.Micro-controller41′ then advances to step105 to continue the present foot function.
• Again referring to step[0117]121, if the measured pressure is not too low,micro-controller41′ advances to step126, turns off the audible alarm (if it was on), and sets the error counter to zero.Micro-controller41′ then advances tosteps127. In steps127-129,micro-controller41′ updates the operating time meter, rewrites the actuation signals topower distribution board49 andpressure control board50, and updates the display as necessary onLCD assembly46.Micro-controller41′ then advances to step105 to continue the present foot function.
• Referring again to step[0118]118, if the foot function is in the deflate or pre-inflate mode,micro-controller41′ advances directly to step127 to update the operating time meter. Instep128,micro-controller41′ changes the actuation signal to pressurecontrol board50 to either energize or de-energize the vent and inflate solenoid valves dependent upon whether the foot function mode is deflate or pre-inflate. For example, if the foot function is in the deflate mode, the vent solenoid valve will open and the inflate solenoid valve will be closed to allow the deflation of the inflated foot wrap. However, if the foot function is in the pre-inflate mode, the vent solenoid valve will be closed in preparation for the next inflate foot function mode. Also instep128,micro-controller41′, viapower distribution board49, stops, starts or continues the delivery of power tocompressor38. Aftermicro-controller41′updates LCD assembly46 instep129, it advances to step105 where the loop is repeated every 25 milliseconds.
• Operation of the power down memory of the preferred embodiment of the present invention will be described in reference to the flowchart shown in FIG. 4. In[0119]step130, if the power is turned off or there is a power line transient (e.g. a power surge or noise),micro-controller41′ executes the power off interrupt. Instep131,micro-controller41′ executes a software filter loop to reduce susceptibility to power line noise transients. Instep132,micro-controller41′ determines if the power has been turned off or if the power line merely experienced a transient. If the power line experienced a transient, the interrupt routine is exited and thepump unit501 continues to operate normally. Ifmicro-controller41′ determines that AC power has been turned off,micro-controller41′ advances to step133 and determines if the power has been on for more then 3seconds. If the power has been on for more than 3 seconds,micro-controller41′ advances to step134 and writes date into EEPROM power downmemory48 values representing the last operator entered foot function settings.Micro-controller41′ then advances to step135 and exits the power down routine. However, if, the power has not been on more than 3 seconds,micro-controller41′ advances to step135 and exits the power down routine.
• FIGS.[0120]13-18 show the general shape of thepump housing20 which has also been described with reference to FIG. 1. Note though that the details ofconsole42 andconnectors22A and22B have been omitted in FIG. 14 to focus attention on the shape ofhousing20. Screws201-204 (shown in FIG. 15) are common screws which securefront plate26 torear plate27. Of course, other conventional connectors could be used instead. Spacers205-208 on the underside ofhousing20 allow for level placement of thepump unit501 on a flat surface.Spacers210 and211, along withspacers205 and206, ensure free flow of air into the pump unit'sair intake215, even when the unit is mounted snugly against a foot board600 (FIG. 18) of a hospital bed.
• Assembly of the[0121]back plate26 is best understood with reference to FIG. 19. As shown therein, airintake filter assembly220 is mounted to the inside surface ofback plate26.Assembly220 basically includes aprimary filter221 and asecondary filter222 together with mountingbracket223.Primary filter221 is fairly porous to allow free intake of air whilesecondary filter222 is positioned to surround the internally-exposed edges ofprimary filter221 to ensure that all intake air is adequately filtered even if it circumventsprimary filter221.Bracket223 is rigidly secured to theback plate26 in a manner that cagesprimary filter221 in place overintake215.Secondary filter222 is glued in place afterwards. The location ofintake215 is ideal as it is partially shielded from liquids and foreign objects whenhousing20 is operatively mounted on afoot board600 of a hospital bed. Such liquids and foreign objects, naturally, might otherwise impede the operation ofunit501, much less the free flow of air intoinlet215.Spacers210 and211 preferably provide a ⅜ inch separation between the foot board600 (shown in phantom line in FIG. 18) andintake215 to ensure free air flow therein.
• Retractable mounting hooks[0122]21A and21B are shaped as shown best in FIGS.17-19.Hooks21A and21B are similar to each other and are symmetrically mounted in a pivotal manner to plate26. The pivotal mounting is best shown in FIG. 19, with reference to hook21A. As shown therein,hook21A is pivotally mounted by means of anintegral shank230 that fits snugly through ahole231 in an irregular socket240 (numbered in FIG. 18) formed inplate26.Hole231 is substantially coaxial withhole232 so that thehooks21A & B pivot in parallel planes that are perpendicular to backplate26 in the preferred embodiment. Once inserted throughhole231,shank230 is pivotally secured therein by a lockingpush ring234. Aspring washer235 is positioned on theshank230 to spring bias the shank through the hole in the same manner as a Bellview washer. Although not clear in FIG. 19, portions ofspring washer235 are bent in a manner that provides such a spring action. The lockingpush ring234 is appropriately sized and flared around its inner circumference in a conventional manner so that it can be pushed ontoshank231 but the flare prevents it from sliding back off theshank231. Thus ring234 provides a permanent pivotal connection forhook21A.
• Although not shown very well in the drawings, it is preferred that slight tongue and groove reliefs are provided on the mating surfaces between the[0123]hook21A andplate26 so thathook21A tends to click into place in either its fully retracted or fully extended positions. The spring bias ofwasher235 helps provide such a clicking action as it tends to retainhook21A in its clicked position. FIG. 17 showshook21A in its fully retracted position, and FIG. 18 shows hook21B in its fully extended position.Socket240 is shaped to neatly receivehook21A when it travels from its fully extended to its fully retracted positions.
• The innovative shape of[0124]hook21A is best appreciated with reference to FIG. 18. Progressing fromshank230 outward, portions ofhook21A are referred to asshoulder245,elbow247,forearm243, andknob241, all formed as an integral member which is generally progressively thinner towardknob241. Theinner face252 ofhook21A approximates a planar surface (except for the protrusion of shank230) so thathook21A pivots freely intosocket240.Knob241, on the other hand, protrudes outward in a direction oppositeshank230 to roughly twice the thickness offorearm243.Knob241 is cylindrical in shape with its leading outer corner truncated and rounded to form asmooth finger pad251.Finger pad251 enables manual pivoting ofhook21A from its fully retracted to its fully extended position. The point of juncture betweenknob241 andforearm243 is referred to aswrist242.
• The forwardmost edges[0125]244 and246 offorearm243 andshoulder245 are substantially planar sections which are parallel to axis250 ofshank230 and, therefore, appear linear in FIGS. 17 and 18. Although fillets are provided atwrist242 to reduce stress concentrations, the plane ofedge244 is roughly perpendicular to the cylindrical surface ofknob241.Knob241 thus forms a protruding lip at the distal end offorearm243, and this lip helps retainpump unit501 onfoot board600 even if it is knocked outward from the foot board.
• Because standard foot boards range from ½ to {fraction (1 1/2)} inches in width, it may also be helpful to consider some of the dimensions of[0126]hook21A. The pivot axis250 for thehook21A is preferably as high as possible onhousing20 and should be at least high enough to ensure the center of gravity ofpump unit501 is lower than the center ofdistal knob241, to help ensure against tipping. To accommodate a range of foot board sizes, the distance between the crease248 ofelbow247 and theplanar surface26′ of back plate26 (whenhook21A is fully extended) is ⅞ inches, thereby snugly receiving the smallest of standard foot boards while leaving the ⅜ inch space provided byspacers210 &211. At the opposite extreme, the forwardmost edge ofknob241 is {fraction (1 7/8)} inches fromsurface26′ (when fully extended), thereby snugly accommodating the widest of standard hospital foot boards. Moreover, for any foot boards in the range of standard sizes, the weight ofpump unit501 tends to pullsurface26′ downward and thus closer to footboard600 due to the constant slope ofedge244, until each ofspacers210 &211 engage thefoot board600. Referring to angle alpha (FIG. 18) the slope ofedge244 is such that alpha is an obtuse angle less than 135 degrees. Preferably, alpha is roughly 115 degrees. With such construction,housing20 is adapted for snug, secure and neat mounting on hospitalbed foot boards600 in the full range of standard sizes.
• Although the present invention has been described in terms of the foregoing preferred embodiments, such embodiments are merely exemplary of the present invention. As will be apparent to those of ordinary skill in the art, many other alternatives, equivalents, modifications, objects, substitutions, variations and the like, of varying degrees, will fall within the scope of the present invention. For instance, the number, specifications and locations of various components or the sequence, number, and complexity of various steps can generally be modified to some degree while still serving substantially the same purposes of the present invention. As a particular example,[0127]air control board50 andcontrol board41 may be combined into a single integrated circuit board to minimize costs and space constraints, as Applicant has done in alternative embodiments. Accordingly, nothing in the foregoing detailed descriptions limits the scope of the present invention in any respect, but rather that scope is defined instead only by the claims which follow, construed as broadly as possible.

Claims (15)

I claim:

1. A medical apparatus for affecting blood circulation comprising:

a foot wrap having an inflatable bladder for applying pressure to a patient's foot;

a pressure source for supplying pressure to said foot wrap;

a line in fluid communication with said pressure source; said line having an expansion reservoir therein for simulating the pressure in the bladder caused by the pressures losses in the apparatus;

a pressure sensing means including a pressure sensor connected to said line, downstream of said expansion reservoir, for sensing the amount to pressure supplied by said pressure source and converting the sensed amount into a signal; and

a control means in communication with said pressure sensing means to adjust the amount of pressure supplied by said pressure source.

2. The apparatus ofclaim 1 wherein said line further comprises at least one restrictor to restrict the flow of air pressure to said pressure sensor.

3. The apparatus ofclaim 1 wherein said signal includes an analog voltage signal, and said pressure sensing means further comprises an analog to digital conversion means to convert said voltage signal into a digital signal.

4. The medical apparatus ofclaim 1 wherein said control means comprises:

a microcontroller; and

a plurality of solenoid valves controlled by said micro-controller to adjust the amount of pressure supplied by said pressure source to said foot wrap.

5. The apparatus ofclaim 4 wherein said micro-controller is operable to read said digital signal from said pressure sensing means and to open and close said solenoid valves in response to the read signal.

6. The apparatus ofclaim 4 wherein said control means further comprises an error detection means for determining when pressure supplied by said pressure source is either to high or to low.

7. The apparatus ofclaim 4 wherein said control means further comprises:

an operator console having programmable keys to enter user settings; and memory means for storing said user settings to be processed by said micro-controller.

8. The apparatus ofclaim 7 wherein said operator console further comprises a liquid crystal display.

9. The apparatus ofclaim 7 wherein said memory means comprises an electronically erasable programmable read only memory.

10. A medical apparatus for cyclically applying pressure to a foot, comprising:

a flexible fabric foot wrap formed from two sheets and having an inflatable bladder therein,

a connector opening into the inflatable bladder and suitable for connection to a source of pressurized fluid;

said foot wrap having a first tab formed from at least one of said two sheets for releasably securing the device to a human foot about the arch, the first tab having a releasable connector at its distal end;

said foot wrap having a second tab formed from at least one of said two sheets for releasably securing the device to a human foot about the heel, the second tab being generally perpendicular to the first tab, the second tab having a releasable connector at its distal end;

said foot wrap having an exterior surface portion on one of said sheets compatible with said releasable connectors so that a connection may be formed when said connectors are pressed against said surface;

a source for supplying pressurized fluid to said inflatable bladder;

pressure sensing means for measuring the amount of pressure supplied by said source; and

a control means in communication with said pressure sensing means to adjust the amount of pressure supplied by said source.

11. The medical apparatus ofclaim 10, further comprising:

a housing for releasably mounting said source on the foot board of a standard hospital bed, said housing comprising a pair of opposite, retractable mounting hooks having sloped surfaces for biasing the source toward said foot board and having knobs at the distal ends thereof for helping retain the hooks on the foot board; and

said hooks further having a horizontal bearing surface for engaging the top of foot boards having smaller widths.

12. An inflatable device for pneumatic compression of the foot, comprising:

an inflatable chamber for wrapping around the foot and compressing the foot when inflated;

a strap formed integral with said first member for wrapping around the lower portion of a leg and securing the first member in place; and

said strap comprising means for cushioning a skin-engaging surface of said strap for minimizing localized pressure concentrations related to said surface.

13. A medical apparatus for affecting blood circulation comprising:

a foot wrap having an inflatable bladder for applying pressure to a patient's foot;

a pressure source for supplying pressurized gas to said foot wrap;

a line in fluid communication with said pressure source;

a control means having a valve means for controlling the supply to supply of said pressurized gas;

a pressure sensing means including a pressure sensor connected to said line for sensing the amount of pressurized gas being supplied by said pressure source upon opening of the valve means and converting the sensed amount into a signal for controlling the valve means; and

said control means being operatively connected with said pressure sensing means turn off the valve means to adjust the amount of pressurized gas being supplied by said pressure source.

14. A method for affecting blood circulation comprising:

applying a foot wrap having an inflatable bladder for applying pressure to a patient's foot;

supplying pressurized gas from a pressure source to said foot wrap;

sensing the amount of pressurized gas being supplied by said pressure source in an expansion reservoir for simulating the pressure in the bladder caused by pressures losses and converting the sensed amount into a signal for controlling the amount of pressurized gas being supplied by said pressure source.

15. A method for affecting blood circulation comprising: applying a foot wrap having an inflatable bladder for applying pressure to a patient's foot;

supplying pressurized gas from a pressure source to said foot wrap;

controlling the supply of pressurized gas with a valve means;

sensing the amount of pressurized gas being supplied by said pressure source upon opening of the valve means and converting the sensed amount into a signal for controlling the valve means; and

turning off the valve means to adjust the amount of pressurized gas being supplied by said pressure source.

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