GB2431351A - Wound dressing vacuum system and vacuum regulator - Google Patents

Abstract

A wound dressing vacuum system has a mechanical vacuum generator <B>80,</B> which may be one or more bellows <B>82, 84</B> either naturally biased towards an extended position or separately biased for example by a spring or springs. The bellows <B>82, 84</B> are connected to a manifold <B>86</B> and the manifold is connected to an adjustable vacuum regulating element <B>100</B>. The bellows produce a vacuum, directed to a dressing via tube <B>12,</B> due to their extension bias which is controlled by the regulator <B>100</B>. Any exudates sucked up tube <B>12</B> passes into the chamber or chambers of the bellows <B>82,84</B> and the unit may be disposed of after use. The vacuum regulator <B>100</B> may have a valve element <B>112</B> biased to a closed configuration by the force of the vacuum generated and an actuator <B>102</B> loads a spring bias member <B>136</B> which acts to open the regulator valve <B>112</B> against the vacuum force.

Description

VACUUM CONTROLLER AND VACUUM DRESSING SYSTEM

The present invention relates to wound management apparatus and in particular to a vacuum apparatus and vacuum dressing system for treating open wounds.

Open wounds, in particular incisional and cutaneous fistulae which are too large to close rapidly, pose particular treatment problems. More specifically, it is necessary to treat sepsis at the wound and to drain the fistula during the healing process. Furthermore, the wound is an area stasis in which there is swelling of the tissues, resulting in insufficient flow of blood to the tissues and thus a reduction in the amount of nutrients to the wound area.

The closure of such wounds by suturing, for example, is far from an ideal solution because this causes stressing of the surrounding skin tissue, does not treat sepsis or allow proper healing. Often, such covered wounds become infected and there is substantial scarring.

Another approach, practised since the 1950's, has been to drain wounds of their exudate, particularly by the use of ostomy pouches and more recently by pouches specifically designed for such purposes.

In 1989, Mark E Chariker et al, in "Effective Management of Incisional and Cutaneous Fistulae with Closed Suction Wound Drainage", Contemporary Surgery, Volume 34, June 1989, published the results of research they carried out on such prior art systems. They discovered that healing is substantially improved if exudate from the wound is continually removed, which can contribute to a significant reduction in inflammation at the wound and of necrosis of the localised tissue. Inflammation of the tissue and the formation of eschar produce a mechanical barrier to wound healing.

Chariker et al developed a closed suction system in which a gauze moist dressing is applied over the open wound. The gauze dressing is sized and shaped to fit into the open wound area. A vacuum drain is then placed over the gauze and a closed suction system then fitted over the wound and dressing, operated continuously during treatment. They found that this prevents eschar formation which in turn decreases the degree of fibroplasia, with an increased rate of reepitheliazation. The conformation of the gauze dressing to the wound bed can prevent overgrowth of surrounding tissue, reduce inflammation of the wound and contribute to the natural formation of new skin tissue at the wound area.

WO-93/09727 discloses a similar closed suction system, in which the gauze is replaced by a flat porous semi-rigid element, made for example from an open cell polymer foam material configured to overlie the wound. This foam element, as the gauze, acts to absorb exudate form the wound bed, which is then removed by the vacuum drain.

The systems to date are expensive and cumbersome. The present invention seeks to provide an improved vacuum dressing system and vacuum apparatus for such a system.

According to an aspect of the present invention, there is provided wound treatment vacuum apparatus for a dressing system including mechanical vacuum generator means and adjustable regulator means for controlling the mechanical vacuum generator means.

The provision of a mechanical vacuum system means that it is not necessary to have, for example, an electrical power supply to power the system. The adjustable regulator means provides control of the vacuum generatable by the mechanical vacuum means. In the preferred embodiment, the adjustable regulator means is incorporated in a pressure regulator.

Preferably, the apparatus includes storage means for storing exudate collected by virtue of the vacuum generated by the vacuum means. In the preferred embodiment, the vacuum means includes one or more bellows operable to generate the vacuum and which in use collect such exudate. The bellows may be self-sprung.

Advantageously, the adjustable regulator is located between an outlet port to the vacuum means and an inlet port for coupling to a vacuum dressing. In the preferred embodiment, the regulator includes a regulator element movable between open and closed positions on the basis of pressure differential between the outlet port and the inlet port.

The preferred embodiments can provide a system which has one of more of the following advantages: low cost, self-powered, light weight, portable, disposable and simple. It is preferred that the system itself can contain clinical waste with minimal risk of contamination. The preferred systems are also designed to be used in the home or on the move, which can free up hospital beds and shorten treatment times.

Although in some embodiments it is envisaged that the system itself can contain clinical waste, other embodiments has been devised in which all exudate is absorbed in a high absorbency dressing, leaving the vacuum supply unit free of clinical waste. This can provide a reusable vacuum supply unit and can simplify regulatory approval.

An alternative approach incorporates all functions of the controller into one unit.

The concept is to sense the vacuum level in the dressing circuit and shut off the vacuum from the supply (spring/bellows) when the required level is reached.

Embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of an embodiment of vacuum dressing system; Figure 2 shows an example of wound shroud; Figure 3 shows another example of wound shroud; Figure 4 shows an example of wound dressing; Figure 5 is a perspective view of an embodiment of pump mechanism casing; Figure 6 is a view of the pump mechanism of Figure 5 with part of the casing removed; Figure 7 is an enlarged view of an upper section of the casing of Figure 5; Figure 8 is a plan view of the internal components of the pump mechanism of Figure 5; and Figure 9 is a cross-sectional view of the preferred embodiment of regulator assembly for the pump mechanism of Figures 5 to 8.

The devices of the embodiments disclosed herein were designed to facilitate negative pressure therapy used, for example, in treating open wounds. The preferred embodiments provide a system having a vacuum supply unit with integral vacuum control and, secondary to this, means for applying the vacuum to a wound via the provision of tubes and a shroud which is sealed to the skin via the application of a self-adhesive film.

The shroud serves the purpose of creating a non-collapsing cover for the wound and dressing therebelow; which ensures that vacuum is evenly applied to the wound. If required, exudate can be drawn away from the wound through this system.

In some embodiments, the vacuum supply unit requires no external power. It is driven by pre-loaded springs which are specified (length, stiffness and so on) to yield the force required to generate the required vacuum for the required duration. The springs could be compressed at the point of manufacture or at the point of use.

In a prototype 5OKpa of vacuum (5OKpa absolute pressure) was generated by the spring force and this was regulated to give 3OKpa (70 Kpa absolute) to OKpa vacuum at the outlet. The specification required a 24Hr duration after which a minimum 3OKpa to remain available for the therapy.

As described below, in the preferred embodiment, the vacuum is created within two polymeric moulded bellows. Springs surround the bellows and are anchored to them at each end by two sets of clamps. This assembly could be referred to as a cartridge which can be placed in a reusable housing for use. However, in some embodiments the complete device could be disposable as the likely (low) cost of manufacture would make this feasible. This is also attractive from the point of view of handling.

Preferably, the status of the device (in terms of capacity or time remaining) is simply indicated by a sliding colour graduated scale which is pulled along with the expanding bellows and viewed through a transparent window in the device housing. A more complex powered electronic sensing system could instead be provided.

The bellows have a moulded nozzle which allows connection directly to a manifold which makes the connection between bellows and the regulator. It is planned that the bellows cartridge could be supplied compressed within the housing. Latches that protrude through the housing allow release of the springs in order that vacuum is created. The system is primed in order to minimise the expansion of the springs as they take up free volume in the system. Once released, the flow restriction provided by the regulator arrests/controls the expansion of the springs/bellows.

Integral to the system is a vacuum regulator. The preferred regulator is infinitely adjustable, in this case between 0 and 3OKpa of vacuum, although this could be engineered to provide any level of vacuum. Furthermore, the adjustment could be made incremental to simplify use. Adjustment is made via a knob which protrudes through the bottom of the housing. It is possible to isolate completely the supply via the regulator but in practice this could be achieved via the use of an isolating regulator in the tube leading to the dressing.

The control characteristics of the regulator can be tailored to suit a particular application.

For example, the spring rate or the cross-sectional area of the regulator seat could be changed. The regulator could be designed to handle fluid (exudate) but in the described embodiments was developed to handle air only as the exudate was to be captured in the dressing. The benefit here is that the bellows can be used to store safely the fluid and the whole device can be disposed of (for example by incineration) with little risk of contamination. However, there are advantages with absorbing all exudate in the dressing with respect to CE marking, device classification and regulatory approval.

It is envisaged that the vacuum supply unit can be housed within a moulded case designed to be worn around the patient's waist.

Referring now to Figure 1, there is shown an early prototype of vacuum system 10.

Not shown in the Figure is a dressing which is applied to a wound. That dressing is provided with a tube 12 which feeds into the vacuum system 10. The tube 12 feeds into an inlet chamber of a pump assembly. In the inlet chamber there is provided a diaphragm sensing element 14 which transmits, via tube 20 and second diaphragm 18, the pressure in the dressing line 12 to the flow restrictor (shown in the dotted outline circle).

A sprung loaded vacuum generating bellows 16 is coupled to the inlet chamber while two control bags 22, 24 abut the bellows 16. The bags 22 and 24 are in essence one fluid filled flexible vessel. The flow restrictor sits between the two elements 22, 24 of this vessel and regulates the flow from the upper element 22 to lower element 24 when the force of the spring 28 acts upon the upper element 24. In this way the rate of expansion of the compression spring 24 can be controlled, thus controlling also the level of the vacuum generated in the bellows 16. Piston element 26, located between the bellows 16 and the upper bag 22, is designed to transmit the load evenly. The arrangement is such that pumping pressure can be provided over a reasonable period of time, such as one day.

While the above system has shown that it can work, the embodiment described below provides a system which has more preferable characteristics such as smaller dimensions, easier use and the like, as will become apparent.

Prior to describing the vacuum system itself, it is useful to describe some examples of suitable wound dressing. Of course, the Chariker et al dressing described above may be used.

Figure 2 shows an example of a 10 cm x 10 cm alginate shroud 30 which is fitted over an open wound. Such a shroud gives a good seal against the skin, particularly when bonded to the skin a self-adhesive film. As can be seen in the Figure, the shroud 30 is provided with a plurality of protrusions 32 extending downwardly (towards the wound) and is connected to the tube 12 leading to the vacuum system. The protrusions leave a cavity over the wound which prevents total collapse of the membrane onto the wound and thereby a loss of effective suction. A border 34 around the protrusions creates a seal over the wound. Within the confines of this shroud there is typically placed a dressing in contact with the open wound, as is known in the art.

Another example of wound shroud is shown in Figure 3 which has a first wound dressing contacting perforated membrane 40 over which a multi-tube suction membrane 42 is placed. The membrane 40 is preferably nonpermeable and sufficiently flexible to conform to the wound surface. It is preferably resistant to biological agents and other compounds. The membrane can be cut to shape and size.

The multi-tube suction membrane 42 can also be shaped and cut to size and includes an array of upstanding tubes 44 open at the lower extremity so as to provide suction at the membrane 40 and thus at the wound surface. The tubes 44 provide substantially even suction throughout the wound area, which can be particularly advantageous in ensuring good exudate removal over the whole wound area. The multiplicity of tubes 44 can be manifolded back to a single port through a manifold, the design of which will be readily apparent to the person skilled in the art.

Another example of dressing is a spiral dressing as shown in Figure 4, which is covered and described in detail on our co-pending British patent application no. 0502650.5 filed on 9 February 2005. The dressing 50 is intended to be placed on a wound bed such that the lower surface 60 of the dressing is placed against the open wound, preferably directly on the wound. The tubing 54 is in this embodiment a half tube, as shown particularly at its outer end 56. Adjacent coils 52 of the tubing 54 are weakly connected together such that the tubing 54 keeps the arrangement shown but the tubing can be separated from its outer end 56 for sizing purposes.

The tubing 54 is provided with a plurality of apertures 58. It is preferably made from a polymeric material, such as silicone, polyurethane or PVC. It could also be made from materials more conventionally used in dressings, such as cotton, and could be in the form of a fabric, mesh or the like.

The dressing 50 is preferably flexible so as to conform to the wound surface, thereby to maximise contact at the wound while minimising patient discomfort.

Figures 5 to 8 show the preferred embodiment of pump mechanism. Referring first to Figure 5, there is shown the casing of a preferred embodiment of pump mechanism. The casing is intended to be portable.

The casing is formed in two parts secured together by release latches 72 (only one of which is shown). A belt anchor 74 is provided for securing the casing to a support, including on a patient where appropriate.

The casing is provided with a adjustment means 76 for controlling the generation of the vacuum, as described in further detail below.

Figure 6 shows the casing of Figure 5 opened and lying therewithin a double bellows pump unit 80, described in further detail below. Figure 6 also shows the tube 12, coupled to a dressing shroud 30 (the example shown in Figure 6 being the shroud of Figure 2). Figure 7 shows the top end of the casing in better detail.

Referring now to Figure 8, the preferred embodiment of the bellows pumping unit is shown in better detail. Unit 80 includes first and second vacuum bellows elements 82, 84 (although it is not necessary to have two bellows in all embodiments of the invention). The bellows 82, 84 are either naturally biased towards the extended position shown in Figure 8, for example by being moulded in the extended configuration, or are separately biased, for example by coil springs (not shown) fitted around the bellows 82, 84 and which urge the bellows to their extended positions.

The bellows 82, 84 are sealingly connected to a coupling manifold 86 of suitable design which would be apparent to the person skilled in the art. The coupling manifold also couples the bellows 82, 84 to control regulator element 100 described in detail below in connection with Figure 9. The coupling member 86 also sealingly connects the tube 12 to the regulator 100, described in further detail below.

The bellows 82, 84 produce a vacuum therein by their extension bias and thereby, under control by the regulator 100, a suction force in the tube 12 and thus at the dressing 30. The generation of the vacuum is entirely mechanical, thereby requiring no other source of power. Moreover, in the preferred embodiment, exudate from the wound is able to be sucked through the tubing 12 into the chambers of the two bellows 82, 84. Thus, not only do the bellows create the required vacuum but also provide exudate chambers for storing exudate in a sealed and thus non-contaminating manner. The unit of this embodiment is such that it can be and is intended to be disposed of after use.

The unit 8 is provided with a supporting frame 88 which has the function of guiding movement of the bellows 82,84 and also includes first and second apertures 90 (only one of which being visible in Figure 9) which couple to a latching member (not shown) for the purpose of keeping the bellows 82, 84 in a compressed state until deployment.

The regulator member 100 is shown in better detail in Figure 9.

Figure 9 is a view in partial section of the preferred embodiment of regulator controller 100 with the control knob 102 at the top and the ports 104, 106 (sectioned through their centres) shown to the right in the drawings.

The main housing block 108 (also known as the regulator seat holder) contains all the ports and fixing points for most of the other components. At the bottom, the moulded regulator seat 100 is screwed into place in fluid connection with the bellows 82, 84. Above this, and held concentric by the main housing 108, is the regulator/piston assembly 110.

The regulator/piston assembly includes a moulded hollow regulator 112 with "X" seal sealing between the regulator and, push-fit thereunto, the mid regulator body 114. The mid regulator body 114 features communicating vacuum ports 104, 106 and location for three further parts, namely the retaining pin 116, the diaphragm 118 and the upper regulator body 120.

The retaining pin 116 is a push fit into the mid regulator body 114 and provides: a) control over rotation due to the slot 122 in the main housing; and b) axial control, to stop the piston assembly coming too far out, by a retaining screw fitted to the main housing (not shown).

The diaphragm 118 locates around a boss 124 at the top of the mid regulator body 108 and is clamped and sealed by the upper regulator body 120. The upper regulator body also locates on the mid regulator body boss 124 and is held in place by a central screw (not shown) screwed into the mid regulator body 108. On the outside of this part is a thread 126 (two-start thread shown) which engages with the internal thread (not shown) of the nut 138. This causes the nut 138 to move axially when rotated as the regulator is stopped from rotating by the retaining pin 116.

Rotation of the nut is achieved by two drive pins 128, 130 which are a sliding fit in the nut 138 but rigidly mounted in the knob 102. The knob 102 is free to rotate about the housing, where a groove 130 locates a ring 132 used to retain the knob 102 in the axial direction. The housing is fixed by screws 134 to the main housing and thus clamps and seals the diaphragm 118.

Finally a compression, possibly coil, spring 136 is fitted between the nut 138 and housing. A compression spring is preferred instead of a tension spring as it offers a more compact solution, although a tension spring could be used in some applications.

In use, the lower vacuum port 106 is connected to the vacuum supply (both bellows 82, 84), while the upper vacuum port 104 is connected to the dressing. Tracing the route from the dressiiig, a connecting port 140 can be seen to the cavity below the diaphragm 118. This ensures the vacuum at the dressing communicates directly with the underneath of the diaphragm 118, tending to pull the regulator 112 down due to the higher atmospheric pressure above the diaphragm 118.

The port 104 aligns with an opening 142 in the regulator. The opening is oversized so that flow can continue whatever the regulator position. The regulator opening 142 connects to the hollow regulator centre which finishes at the middle of the regulator seal.

If the regulator is open, the circuit continues across the regulator seat (360 degrees) into the chamber 144 in the bottom of the main housing then out via the vacuum supply port 106.

The starting setting is with the nut 138 screwed right up (just below the internal ceiling of the knob 102). At this point there is no compression on the spring 136 so the regulator is resting shut.

By rotating the knob 102 clockwise, the drive pins 130 rotate the nut 138. As the regulator is prevented from rotating by the retaining pin 116 the nut 138 moves down the thread 126.

As the nut 138 is screwed down the regulator, the spring 136 is compressed and an axial force is generated. This pushes back on the nut 138 which in turn transfers an upwards load to the regulator assembly 112.

The initial state for the regulator assembly 100 is with the nut 138 fully up so there is no spring load. It is anticipated that the vacuum circuit would be evacuated at manufacture with a shut off regulator (not shown) closed near the dressing and a mechanical restraint holding the bellows springs 82, 84 closed. This vacuum would hold the regulator 112 closed as the atmospheric pressure on the top of the diaphragm 118 is greater than the internal pressure generating a downward force on the regulator 112, thereby sealing it.

Once the vacuum dressing is applied and connected, the bellows springs 82, 84 are released and the shut off valve 112 opened. The valve 112 should still stay shut as there is vacuum under the diaphragm 118 and no opposing force from the spring 136.

To start the equipment working the knob 102 is rotated to the position for the desired vacuum level. Rotating the knob 102 clockwise causes the drive pins 130 to turn the nut 138, compressing the spring 136 and apply an upwards force on the valve 112.

The valve 112 will stay closed until the spring 136 pushes the valve 112 up with greater force than the vacuum pulls it down.

Once the knob 102 has been set at the desired position, the valve 112 remains open until sufficient fluid (that is, gas in a gas only system or gas and liquid in a system which collects exudate) has flowed into the bellows 82, 84, reducing the vacuum to a point where the vacuum force exceeds the spring force and the valve 112 closes.

Subsequently, inflow that reduces the dressing vacuum will reduce the downward force and cause the valve 112 to open until the vacuum level is restored.

The spring 136 should fit within the cavity without binding even when compressed (its outside diameter increases when compressed). Stiffer springs will work more quickly (less knob rotation) but may provide less repeatable vacuum application. A middle rate spring should preferably have an operating range (off to full vacuum) ofjust over 1 turn of the knob for the initial thread.

The best pitch for the thread 126 needs to be considered in conjunction with the spring rate.

Claims (14)

1. Wound treatment vacuum apparatus for a dressing system including mechanical vacuum generator means and adjustable regulator means for controlling the mechanical vacuum generator means.

2. Wound treatment vacuum apparatus according to claim 1, wherein the vacuum means includes one or more bellows operable to generate the vacuum.

3. Wound treatment vacuum apparatus according to claim 2, wherein the bellow or bellows in use collect exudate.

4. Wound treatment vacuum apparatus according to claim 2 or 3, including means to bias the or each bellows in an extended configuration.

5. Wound treatment vacuum apparatus according to claim 4, wherein the bias means includes one or more sprung elements.

6. Wound treatment vacuum apparatus according to claim 2 or 3, wherein the bellows are self-sprung.

7. Wound treatment vacuum apparatus according to any preceding claim, wherein the adjustable regulator is located between an outlet port to the vacuum means and an inlet port for coupling to a vacuum dressing.

8. Wound treatment vacuum apparatus according to claim 7, wherein the regulator includes a regulator element movable between open and closed positions on the basis of pressure differential between the outlet port and the inlet port.

9. Wound treatment vacuum apparatus according to claim 8, wherein the regulator element includes a flexible diaphragm.

10. Wound treatment vacuum apparatus according to any preceding claim, including storage means for storing exudate collected by virtue of the vacuum generated by the vacuum means.

11. Wound treatment vacuum apparatus for a dressing system including vacuum generator means, adjustable regulator means for controlling the mechanical vacuum generator means and storage means for storing in the apparatus exudate collected by virtue of the vacuum generated by the vacuum means.

12. Wound treatment vacuum apparatus according to claim 11, wherein the storage means is integral with the vacuum generator means.

13. Wound treatment apparatus including vacuum apparatus according to any preceding claim and a wound dressing designed to be coupled to the vacuum apparatus.

14. A vacuum regulator for regulating a vacuum supply including a valve element located on a movable member and biasable to a closed configuration by the force of a vacuum provided by a vacuum source, an actuator coupled to a control member and operable to load a sprung bias member which acts to bias to an open configuration the valve element against the vacuum force.