WO2009016603A2

WO2009016603A2 - Reduced pressure wound treatment apparatus

Info

Publication number: WO2009016603A2
Application number: PCT/IB2008/053075
Authority: WO
Inventors: Malan De Villiers; Karl Grimsehl
Original assignee: Blackbeard, Graham Alan
Priority date: 2007-08-01
Filing date: 2008-07-31
Publication date: 2009-02-05
Also published as: WO2009016603A3

Abstract

The invention concerns a reduced pressure wound treatment apparatus (10). The apparatus has a disposable and replaceable vacuum pump (28) which includes a suction chamber (44) and a suction line (24) which is connected between the suction chamber of the vacuum pump and a porous wound contact means (16) placed in contact with a wound (12) from which wound exudate is to be drawn. The apparatus also includes a re-usable pump actuator (42) arranged externally of the vacuum pump, out of fluid communication with the suction chamber. The actuator is operated to actuate the vacuum pump in order to generate a reduced pressure in the suction chamber. This draws wound exudate from the wound through the wound contact means and suction line into the suction chamber. At the end of a treatment or when the suction chamber is full, the suction chamber can be disposed of and replaced, while the actuator can be re-used.

Description

"REDUCED PRESSURE WOUND TREATMENT APPARATUS"

BACKGROUND TO THE INVENTION

THIS invention relates to a reduced pressure wound treatment apparatus.

In the treatment of open wounds the application to the wound of controlled levels of negative pressure, i.e. a pressure which is reduced with respect to ambient pressure, or suction, has been shown to accelerate wound debridement and to promote healing. It is believed that the applied suction assists in the removal of interstitial fluid from the wound site, thereby decreasing localised oedema and increasing blood flow.

In the co-called V.A.C.® (Vacuum Assisted Closure) system, as described for instance in ZA95/6968, a porous pad of open cell foam material is placed in contact with the wound and a sealing membrane or drape is located over the pad. The drape has an adhesive underside by means of which it can be adhered to the skin of the patient around the outside of the pad, thereby providing a seal. One end of a vacuum hose is placed in communication with the pad, for instance by sandwiching it between two layers of the pad or by embedding it in the pad. The opposite end of the hose is connected to a canister. A separate vacuum pump is provided to generate a negative pressure in the canister so that wound exudate is drawn from the wound into the canister, where it accumulates. The canister is disposed of when it is full or after a predetermined period of wound treatment. The pump can be re-used with a new canister.

It is obviously highly undesirable for there to be any cross-contamination through re-use of components which may be contacted by the exudate. For this reason, the known V.A.C.® system requires a filter between the canister and the vacuum pump. SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a reduced pressure wound treatment apparatus comprising:

a disposable and replaceable vacuum pump including a suction chamber and a suction line which is connectable between the suction chamber of the vacuum pump and a porous wound contact means placed in contact with a wound from which wound exudate is to be drawn, and

a re-usabie pump actuator arranged externally of the vacuum pump, out of fluid communication with the suction chamber, which is operable to actuate the vacuum pump in order to generate a reduced pressure in the suction chamber, thereby to draw wound exudate from the wound through the wound contact means and suction line into the suction chamber.

This apparatus accordingly differs significantly from conventional V.A.C.® apparatuses inter alia in that the vacuum pump is a component which is disposable in entirety, whereas in the conventional V.A.C.® apparatus, the pump is re-used. The disposabiiity of the pump in accordance with the present invention is advantageous in that it reduces the risk of exudate cross-contamination.

In one apparatus according to the invention the vacuum pump is a diaphragm pump which includes a reciprocable diaphragm and the pump actuator includes a drive operable to reciprocate the diaphragm of the vacuum pump and thereby generate reduced pressure in the suction chamber. The vacuum pump may comprise a rod connected to the diaphragm and the actuator may comprise a lever arranged to engage the rod, a shaft carrying a cam which engages the lever, means for rotating the shaft such that corresponding rotation of the cam rocks the lever and causes reciprocation of the diaphragm. Coπveniently the rod is hollow and communicates with the interior of the suction chamber in order to serve as an air outlet from the suction chamber. A filter may be fitted to the rod. The lever may include a clevis arranged to engage the rod, and there may be valves for controlling air flow from the suction chamber through the rod.

The apparatus may further comprise a pressure sensing line for contacting the wound contact means, a pressure transducer which is arranged to sense the pressure at the wound through the pressure sensing line and which is arranged to produce an output related to the sensed pressure, and control means responsive to the output of the pressure transducer to control the operation of the pump actuator and thereby control suction applied to the wound through the suction line and wound contact means.

The apparatus may also comprise a connector which can be placed on the wound contact means and which has a first opening therein for receiving the suction line and for locating the suction line in fluid communication with the wound contact means. The connector may have a second opening therein for receiving the pressure sensing line. The preferred connector has a flat, flexible base with the first and second openings spaced apart therein, and hollow upstanding spigots extending from the base and communicating with the openings, the suction and pressure sensing lines being receivable in the spigots.

According to another aspect of the invention there is provided a method of operating a reduced pressure wound treatment apparatus having a porous wound contact means locatable in or on a wound, a vacuum pump including a suction chamber, a suction line connectable between the wound contact means and the suction chamber of the vacuum pump and a pump actuator arranged externally of the vacuum pump, out of fluid communication with the suction chamber, the method comprising the steps of operating the pump actuator to actuate the vacuum pump in order to generate a reduced pressure in the suction chamber, thereby to draw wound exudate from the wound through the wound contact means and -A-

suction line into the suction chamber and, after treatment of the wound or when the suction chamber is container is full of exudate, disposing of the wound contact means, suction line and vacuum pump while retaining the pump actuator for re-use.

The preferred method comprises the further steps of sensing the pressure at the wound and controlling the operation of the pump actuator in response to the sensed pressure. Typicaliy the pump actuator is controfled in such a manner as to maintain a substantially constant negative pressure at the wound. In practice, this may involve periodically switching the actuator off and on.

BRiEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:

Figure 1 diagrammatical Iy illustrates a reduced pressure wound treatment apparatus according to this invention;

Figure 2 shows a perspective view of a hose connector forming part of the apparatus seen in Figure 1;

Figure 3 shows a perspective view of the vacuum pump and actuator of the apparatus seen in Figure 1 ;

Figure 4 shows an exploded perspective view of the vacuum pump seen in Figure 3;

Figure 5 shows a diagrammatic cross-sectional view of the vacuum pump; and

Figure 6 graphically represents the operation of the vacuum pump. DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

The reduced pressure wound treatment apparatus 10 seen in Figure 1 is used to treat an open wound 12, for example a burn wound or ulcer, at the surface of a body part 14 of an injured patient.

The apparatus 10 includes a porous wound contact means 16 which is placed in contact with the wound and which is shaped in situ to fill the wound cavity. A hose connector 18, illustrated in Figure 2, is located on the wound contact member 16 as illustrated. A flexible sealing cover or drape 19 is placed over the wound contact member and connector. The underside of the cover 19, or at least peripheral edge regions 17 of that underside, carry adhesive material by means of which the periphery of the cover can be adhered to the patient's skin around the wound contact member. This establishes a sealed cover over the wound contact member and connector.

Referring to Figure 2, the connector 18 has a flat base 20 formed with spaced apart openings 21 communicating with hollow, upstanding spigots

22.

Extending through a first of these spigots is one end of a flexible, tubular suction line 24, as shown in Figure 1. The opposite end of the line 24 is connected to the inlet 26 of a vacuum pump 28 which has an outlet 30.

One end of a tubular pressure sensing line 32 is connected to the other of the spigots 22 of the connector 18. The line 32 extends to a pressure sensor in the form of a pressure transducer 36. A hydrophobic filter 38 is located in the line 34 between the connector 18 and the pressure transducer 36.

In this embodiment, the wound contact means 16 is provided by a porous bag accommodating a large number of discrete, rigid or semi-rigid particles 40 which are preferably of spherical shape. The wound contact means 16 is described in more detail in a copending international patent application entitled "Wound Contact Means for a Reduced Pressure Wound Treatment Apparatus" filed simultaneously with the present application by the present applicant. The suction line 24 extends through the relevant spigot 22 and opening 21 into the bag such that its inner end resides amongst the particles 40. As described in the copending international patent application, the suction line 24 could alternatively terminate at the surface of the bag without actually entering it.

The vacuum pump 28, which is driven by an external actuator 42, is illustrated in Figures 3 to 5. The actuator 42 is itself illustrated in Figure 3. The vacuum pump includes a suction chamber 44 defined by a moulded plastics canister 46 with a threaded upper end 48 onto which a moulded plastics lid 50 can be screwed. The inlet 26 is provided by a nipple 52 to which the suction tube 24 is connected and which communicates with the interior of the chamber through an opening 54.

A circular disc 56 spans across the interior of the canister 46 above the inlet 26. A first non-return valve closure 58 has a central stem 62 which locates in a central hole 63 in the disc and a peripheral, flexible skirt 64 which locates in a recess 66 around the hole. The base of the recess is perforated by apertures {not visible) surrounding the hole beneath the skirt 64.

A flexible diaphragm 68 of rubber or other suitable elastomeric material is located over the disc 56. The diaphragm has a recess on its underside which receives a rigid disc 70. The disc 70 is formed integrally with an upstanding, hollow, externally threaded plunger rod 72. A rigid, threaded locking disc 82 is threaded onto the rod 72 over the diaphragm and sandwiches a central portion of the diaphragm between itself and the disc 70. The diaphragm has a peripheral lip 73 which wraps over the periphery of the disc 56 and which is engaged in sealing fashion by the lid 50 when the lid is connected to the canister 46.

The rod 72 has a small, central hole located in a recess 74 at its upper end. The base of the recess is perforated by apertures surrounding the central hole. The central hole and surrounding apertures are not visible in Figure 4. A second non-return valve closure 76 has a central stem 78 which locates in the central hole and a peripheral skirt 80 which locates in the recess 74 over the surrounding apertures.

The assembly described above is held together by threaded engagement of the lid 50 on the canister 46.

Referring to Figure 3, the pump actuator 42 has a motor 84 which drives an output shaft 86 carrying a cam 88 acting on a roller 90 at the end of a lever arm 92 pivoted at 94 to a frame 96 which fits over the lid 50 of the vacuum pump. A clevis 98 at the opposite end of the lever arm 92 engages the underside of a nut 100 threaded on the rod 72 as illustrated.

In use, with the motor 84 running, the cam 88 rotates and applies a vertical rocking action to the lever arm 92 which causes the diaphragm 68 to flex up and down. On each upward stroke of the diaphragm the non-return valve closure 58 opens by upward flexing of its skirt 64 to expose the associated apertures in the recess 66 of the disc 56.

At the same time the non-return valve closure 76 closes by downward flexing of its skirt 80 to seal on the associated apertures in the recess 74. Suction is accordingly applied to the suction chamber 44. When there is sufficient pressure differential between the interior of the canister 46 and the wound site, wound exudate is drawn into the chamber 44 from the wound through the wound contact means 16 and suction tube 24.

On each downward stroke of the diaphragm, the non-return valve closure 58 closes by downward flexing of its skirt 64 and the non-return valve closure 76 opens by virtue of upward flexing of its skirt 80, with the result that air is exhausted from the suction chamber 44 to atmosphere through the apertures surrounding the central hole in the recess74, and through the open upper end of the rod 72. The rod 72 accordingly serves as the outlet 30. In Figure 3, the clevis 98 acts on the underside of a washer 83 beneath the nut 100 such that upward movement of the clevis causes upward movement of the rod 72 and hence upward flexing of the diaphragm. A spring (not shown) may be provided to bias the diaphragm 68 downwardly again when the clevis 98 moves downwardly.

A filter 102 (Figure 1) may be provided at the open upper end of the rod 72. This wϋl typically include a liquid absorbing medium the function of which is to arrest any wound exudate which might otherwise exit through the rod 72. As an added benefit, if the canister 46 fills with exudate to the extent that the filter 102 becomes blocked, the power drawn by the motor 84 will increase and appropriate sensing of this may be used to initiate operation of an automatic cut off switch terminating the supply of power to the motor and, possibly, also initiating the generation of an alarm to indicate that the canister is full.

The pressure transducer 36 senses the pressure at the wound site through the line 32. The transducer may be arranged to output a signal related to the sensed pressure to a control unit 104 which controls the operation of the motor 84, and hence of the vacuum pump, in order to maintain a desired pressure at the wound site. It is accordingly possible to regulate the suction pressure applied to the wound site in response to the feedback received by the transducer through the line 32.

In practice, actuation of the vacuum pump will typically be maintained until a desired, predetermined pressure is achieved at the wound site. Then, in response to the feed back signal at that time, the control unit switches the motor off. As pressure bleeds back into the system, the pressure applied to the wound site will gradually increase.

When a predetermined pressure is sensed by the transducer the motor is again switched on to reduce the pressure once more to the desired level. This is represented in Figure 6 in which the line 106 represents the initial build-up of vacuum, i.e. reduced pressure, the lines 108 represent gradual increases in pressure after the motor is switched off and the lines 110 represent the build-up once more of vacuum or negative pressure each time the motor is again switched on.

It is envisaged that the apparatus may operate continuously under the control described above and, of course, subject to replacement of the canister 46 when full. However it is also within the scope of the invention for the control unit to be set to an intermittent setting in terms of which the apparatus will operate only periodically, for example five minutes on and two minutes off.

After a treatment has been completed, or when the suction chamber 44 is full, the vacuum pump 28 is detached from the actuator 42 and is disposed of. If further treatment is required, a fresh vacuum pump is mounted to the actuator and the process described above is repeated.

An important advantage of the invention as exemplified above is the fact that the vacuum pump 28 is a disposable item along with other components, namely the wound contact means 16, connector 18 and suction and pressure sensing tubes 24 and 32, which come into contact with the wound exudate. The reusable actuator 42 does not come into contact with the exudate in any way so contamination of this component is excluded. The hydrophobic filter 38, which is also a disposable component, prevents exudate from coming into contact with the pressure transducer 36.

In the described embodiment, the design of the actuator is such that it allows for adjustment of operating parameters such as the stroke of the diaphragm. In this design it will be understood that the rod 72 forms part of the outlet from the vacuum pump and is accordingly exposed to exudate. It must therefore be disposed of along with the rest of the vacuum pump. In other embodiments, the outlet could be arranged in a different position so that the rod or other drive for the diaphragm is not exposed to exudate. In one potential arrangement, the drive could be a solenoid drive having a reciprocable piston which acts externally on the diaphragm and which is accordingly not exposed to exudate.

In the example described above, the lid 50 screws onto the canister 46. In other embodiments, there may be a lid which connects to the canister by a snap fit, or the lid may be glued or otherwise fixed onto the canister.

Claims

A reduced pressure wound treatment apparatus comprising:

a re-usable pump actuator arranged externally of the vacuum pump, out of fluid communication with the suction chamber, which is operable to actuate the vacuum pump in order to generate a reduced pressure in the suction chamber, thereby to draw wound exudate from the wound through the wound contact means and suction line into the suction chamber.

2.

An apparatus according to claim 1 wherein the vacuum pump is a diaphragm pump which includes a reciprocabie diaphragm and the pump actuator includes a drive operable to reciprocate the diaphragm of the vacuum pump and thereby generate reduced pressure in the suction chamber.

3.

An apparatus according to claim 2 wherein the vacuum pump comprises a rod connected to the diaphragm and the actuator comprises a lever arranged to engage the rod, a shaft carrying a cam which engages the lever, means for rotating the shaft such that corresponding rotation of the cam rocks the lever and causes reciprocation of the diaphragm.

4.

An apparatus according to claim 3 wherein the rod is hollow and communicates with the interior of the suction chamber in order to serve as an air outlet from the suction chamber.

5.

An apparatus according to claim 4 and comprising a filter fitted to the rod.

6.

An apparatus according to claim 4 wherein the lever includes a clevis arranged to engage the rod.

7.

An apparatus according to any one of claims 4 to 6 and comprising valves for controlling air flow from the suction chamber through the rod.

8.

An apparatus according to any one of the preceding claims further comprising a pressure sensing line for contacting the wound contact means, a pressure transducer which is arranged to sense the pressure at the wound through the pressure sensing line and which is arranged to produce an output related to the sensed pressure, and control means responsive to the output of the pressure transducer to control the operation of the pump actuator and thereby contro! suction applied to the wound through the suction line and wound contact means.

9.

An apparatus according to claim 8 and further comprising a connector which can be placed on the wound contact means and which has a first opening therein for receiving the suction line and for locating the suction line in fluid communication with the wound contact means.

10.

An apparatus according to claim 9 wherein the connector has a second opening therein for receiving the pressure sensing line.

11.

An apparatus according to claim 10 wherein the connector has a flat, flexible base with the first and second openings spaced apart therein, and hollow upstanding spigots extending from the base and communicating with the openings, the suction and pressure sensing lines being receivable in the spigots.

12.

An apparatus according to any one of the preceding claims and further comprising a sealing cover which can be placed over the wound contact means and connector and which can be adhered to the skin of a patient around the wound contact means with the suction line passing through the cover.

13.

A method of operating a reduced pressure wound treatment apparatus having a porous wound contact means locatable in or on a wound, a vacuum pump including a suction chamber, a suction line connectable between the wound contact means and the suction chamber of the vacuum pump and a pump actuator arranged externally of the vacuum pump, out of fluid communication with the suction chamber, the method comprising the steps of operating the pump actuator to actuate the vacuum pump in order to generate a reduced pressure in the suction chamber, thereby to draw wound exudate from the wound through the wound contact means and suction line into the suction chamber and, after treatment of the wound or when the suction chamber is container is full of exudate, disposing of the wound contact means, suction line and vacuum pump while retaining the pump actuator for re-use.

14.

A method according to claim 13 comprising the further steps of sensing the pressure at the wound and controliing the operation of the pump actuator in response to the sensed pressure.