GB2416909A

GB2416909A - Wound simulation device

Info

Publication number: GB2416909A
Application number: GB0515334A
Authority: GB
Inventors: Wayne G Gardner; Rob G Cameron
Original assignee: BRADFORD TEACHING HOSPITALS NH
Current assignee: BRADFORD TEACHING HOSPITALS NH
Priority date: 2004-07-31
Filing date: 2005-07-27
Publication date: 2006-02-08
Anticipated expiration: 2025-07-27
Also published as: GB0417138D0; GB0515334D0; GB2416909B

Abstract

A wound simulation device suitable for use in testing absorbent dressing is comprises a chamber 4 for a liquid and a porous member 6 with a wound simulation surface 8 which forms part of the exterior of the device. The wound simulation surface 8 has a plurality of pores which are in fluid communication with the chamber 4. A pressurisation device 14 is used to apply pressure to liquid in the chamber 4, thereby causing liquid to emerge from pores in the wound simulation surface 8. The dimensions of the pores can be chosen such that substantially no liquid emerges from the pores unless a pressure is applied to liquid in the chamber 4. This allows the wound simulation device to be used in various orientations, including vertical, and allows the wound simulation surface to be convex if required.

Description

J

24 1 6909 The present invention relates to a wound simulation device. The wound simulation device can be used for testing absorbent dressings and educational and training purposes.

Absorbent dressings are applied to many types of surface wounds. These include pressure sores, ulcers and wounds resulting from surgery. There exists a need to be able to test absorbent dressings in the laboratory simulating their use on a real-life wound. Such tests are useful to standardise the characteristics ol a dressing, and to confirm that the dressing performs as expected, in controlled, repeatable conditions.

In view of this, a wound simulation device has been proposed which consists of a 0 horizontal plate with a circular depression in it. The circular depression forms the simulated wound surface. A single central aperture is present in the centre of the circular depression. The dressing to be tested is placed on top of the depression, in a horizontal orientation, and simulated wound exudate liquid is supplied from the hole in the depression. It is questionable whether this device provides an accurate simulation of a wound in a patient, particularly because the wound exudate liquid is supplied from a single point. The apparatus relies on the absorbent dressing itself to distribute the wound exudate fluid across the simulated wound surface.

Another wound simulation device which has been proposed also includes a circular depression which can be used to simulate a wound. T he circular depression has an inlet aperture and an outlet aperture connected by an open channel which follows a winding route. In this device simulated wound exudate can be made to flow through the channel where it can be absorbed by an applied dressing under test. However, once again it is questionable whether this represents an accurate model of a real-life wound.

The present invention provides a wound simulation device having a porous member. The porous member has a wound simulation surface on an exterior surface of the device. The wound simulation surface includes a plurality of pores. By providing a plurality of pores on the wound simulation surface, the wound exudate can be supplied over the entire area of the wound simulation surface in a manner similar to that of a real-life wound. This results in an improved simulation and consequently more useful test results for absorbent dressings.

According to a first aspect of the present invention, there is provided a wound simulation device comprising: a chamber for a simulated wound exudate liquid; a porous member having a wound simulation surface which forms part of the exterior of the device, the wound simulation surface having a plurality of pores in fluid communication with the chamber; and l o a pressurization device for applying pressure to the liquid in the chamber; wherein applying pressure to the liquid in the chamber causes the liquid to emerge from the pores in the wound simulation surface.

The pores can be formed by channels through the porous member, or by interconnected spaces at the interstices of, for example, a sintered ceramic. The wound simulation surface can therefore give a more realistic simulation of a real-life wound, because liquid can be supplied from a plurality of pores. These pores can mimic the distribution and size of fluid outlets from which wound exudate exudes in a real-life wound. The pressurization device can apply a back pressure to the liquid in the chamber. The flow of liquid out of the pores can be varied depending on the pressure applied by the pressurization device. Thus, a more accurate simulation of a wound can be achieved.

In one embodiment, the porous member comprises: a matrix formed from an impermeable material; and a plurality of ducts extending through the matrix; wherein the ducts are in fluid communication with the chamber and have a first end opening onto the wound simulation surface thereby forming the plurality of pores.

It is therefore possible to provide a porous surface using known manufacturing techniques.

This also allows the use of a matrix formed from an impermeable material, such as a metal or plastic. This is particularly useful if it is desired to clean the wound simulation surface after testing a dressing.

Preferably, the ducts extend substantially straight through the matrix. Substantially straight ducts can be formed easily by simply drilling or otherwise boring holes in a solid s impermeable matrix. Various standard methods can be used to form the ducts depending on the precise dimensions required. This can include drilling or laser forming, amongst other techniques.

In another embodiment, the ducts are formed by a plurality of tubes having first and second ends, the tubes embedded in the matrix at or towards the first end and extending from the l o first end into the chamber. The porous member can then be easily manufacture, because the ducts are defined by tubes embedded in the matrix. This allows the production of small diameter ducts through the matrix. For example the tube diameter can he 0.2 mm or less, preferably 0.1 mm or less.

Preferably, walls of the tubes are permeable to the simulated wound exudate liquid. This enables liquid in the chamber to enter the tubes through the exposed walls of the tube which extend into the chamber.

Preferably, the device further comprises a sealing member contained in the chamber or defining a wall of the chamber, and wherein the second ends of the tubes are embedded in the sealing member to close the second end to flow of simulated wound exudate liquid.

Liquid cannot then enter the tubes through the end of the tube in the chamber and must instead enter via the walls. This provides an additional throttling effect on fluid flow, over and above that provided due to the diameter and length of the tube, which can be used to limit flow out of the pores.

Preferably, the tubes are permeable to the simulated wound exudate liquid.

2s Preferably the diameter of the pores is less than about 0.2 mm, preferably less than about 0.1 mm. The pores can therefore provide any more accurate representation of fluid outlets in a real-life wound, rather than the relatively large apertures and channels utilised in other proposed devices.

Preferably, the area of the wound simulation surface occupied by the pores is at least about 5%, more preferably at least about 10% of the total area of the wound simulation surface.

s Thus, a large proportion of the area of the wound simulation surface is open due to the presence of pores. This can provide a more accurate simulation of a real-life wound.

Preferably, the mean number of pores per cm2 is at least about l DO. Thus, the mean number of pores per cm can accurately reflect the distribution of pores in a real-life subject.

The precise distribution of pores over the surface would ideally be substantially uniform, lo although some variation is possible between particular areas on the surface. Preferably the distribution of pores over the surface is substantially the same as that of fluid outlets on a real-life wound which is to be simulated.

Preferably the wound simulation surface is polished, more preferably the surface finish of the wound simulation is finished by lapping. This reduces surface roughness and can help to ensure that the pores are not blocked. It can also reduce snagging of the absorbent dressing on the wound simulation surface. Surface roughness can also create chanucls which might duct liquid away from parts of dressing, reducing the accuracy of the simulation.

The wound simulation surface can be convex or concave. The convex or concave curve can be around a single axis, or around two or more axes. In this context, the use of convex or convex can denote a complex surface, as well as portions of the curved surface of a cylinder, an ellipsoid or sphere. This allows the wound simulation surface to more accurately model a real-life wound. Real-life wounds can be convex, for example the wound may be present on the outside of an arm, leg or neck of a patient and therefore would exhibit the curvature of that part of the body. Real-life wounds can also be concave, for example pressure sores or post-operative wounds. The previous devices were not suitable for use with convex or concave surfaces.

Preferably, the depth to which the device extends from the wound simulation surface is less than about 5cm. This allows a particularly compact wound simulation device to be created and allows the use of the device in a wide range of applications, including embedding the device in a synthetic body part or mannequin to provide an even more accurate simulation of a wound.

Preferably, the device includes a quantity of simulated wound exudate liquid within the chamber. This liquid can be aqueous solution, such that the viscosity at 37 C is between about 1.6 and about 2.4 milliPascal seconds. Thus, by using a liquid with a viscosity closely approaching that of wound exudate in real-life a more accurate simulation can be I o obtained.

In an alternative embodiment, the simulated wound exudate liquid can comprise animal blood plasma. It has been found that this also provides an accurate simulation of real-life It is preferable that the dimensions of the pores in the wound simulation surface are chosen such that, when the wound is oriented downwards and the pressurization device applies no additional pressure to the liquid, substantially no simulated wound exudate liquid emerges from the pores.

By "oriented downwards" it is meant that the wound simulation surface forms the lower surface of the wound simulation device, such that the liquid in the chamber will tend to drain from the chamber under its own weight via the pores in the wound simulation surface. Thus, it is possible to use the wound simulation device in any orientation, without the risk of uncontrolled draining of liquid through the pores. This is not possible with any of the prior proposed devices which can only be used in a horizontal position with the apertures for liquid facing upwards because otherwise the liquid in the devices would tend to drain from the apertures without control. It also allows use of the wound simulation device with a back pressure present in the chamber. It is thought that the presence of back pressure may affect the performance of an absorbent dressing, but prior devices do not allow simulation of a back pressure.

Preferably, wherein the pressurisation device is a pump, more preferably a syringe pump, and the wound simulation device preferably further comprises a controller for controlling the pump. A syringe pump can provide precise control over the pressure applied to fluid in the chamber which can translate to very precise control of the delivery rate of the liquid through the pores. If the syringe pump is controlled by a controller, which could be microprocessor or computer based, even higher accuracy is possible. Other pressurization devices could be used and choice will depend on the accuracy of pressure required. For example, it would be possible to directly use a syringe to inject fluid into the chamber, although this gives less control over the fluid pressure. Likewise, it could be envisaged 0 that liquid could be supplied into the chamber from a separate reservoir which could be varied in height relative to the chamber depending on the pressure required to be applied.

According to a second aspect of the present invention there is provided a model of a human or animal body part incorporating a wound simulation device according to the above described first aspect of the invention. This allows a particularly realistic simulation of a IS wound, because the dressing can be applied to a body part which is very similar to a real life application. The body part could then be manipulated into more realistic positions than the pure horizontal position which is possible with prior devices. It is possible that the body part could be articulated in some way to simulate natural movement of a patient while the dressing is applied.

According to a third aspect of the invention, there is provided a mannequin incorporating a body part according to the second aspect of the invention. This allows a more realistic simulation to be achieved, because the manikin could be articulated in a realistic manor, and could incorporate motors or other actuators for moving the body part including the wound simulation device in a natural manner.

2s The embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic representation of a wound simulation device according to a first exemplary embodiment the present invention; Figure 2 is a cross section of a chamber and wound simulation surface according to a first exemplary embodiment of the present invention; and Figure 3 is a cross section of a chamber and wound simulation surface according to a second exemplary embodiment of the present invention.

Figure I depicts an exemplary embodiment of the wound simulation device according to the present invention. The device incorporates a chamber 4 which can include a liquid. A porous member 6 is attached to the chamber. A wound simulation surface 8 forms part of the porous member 6 and has a plurality of pores. The pores are in fluid communication with liquid in the chamber 4 such that liquid in the chamber 4 can emerge onto the wound lo simulation surface 8 via the pores. The wound simulation surface is preferably polished to improve its smoothness. This avoids snagging of an absorbent dressing placed against the wound simulation surface. In this embodiment the wound simulation surface is polished by lapping.

The device also incorporates a back plate 10 and a liquid inlet 12. The back plate 10 seals s liquid within the chamber 4 so that the only way through which liquid can enter or leave the chamber 4 are by the liquid inlet 12 or by the pores in the porous member 6. A syringe pump 14 is connected by hose 15 to the liquid inlet 12. This allows liquid to be supplied into the chamber 4 by the syringe pump 14 and also pressurised to create a back pressure on the liquid.

The syringe pump 14 can be controlled by a computer or microprocessor based system (not illustrated) which can give precise control over the pressure applied to liquid in the chamber 4, and consequently the flow of liquid through the pores.

The construction of the wound simulation surface and its interaction with liquid in the chamber 4 will now be described in more detail with reference to Figure 2. In this 2s embodiment, the porous member 6 comprises a plurality of pores formed through an impermeable matrix. These pores can be formed by various known methods, for example by drilling, depending on the inventions of the pores required. The pores preferably have a diameter and distribution corresponding to the diameter and distribution of fluid outlets for wound exudate in the real-life subject which is to be simulated. To achieve this, the pores preferably have a diameter of less than 0.2mm, more preferably less than 0.1mm, and there are preferably at least 100 pores per cm2.

A threaded connection 16 on the porous member engages a corresponding threaded portion formed on the walls of the chamber 4. This allows the porous member to be easily removed for cleaning. It also allows a variety of porous members to be supplied with different characteristics of pores on the wound simulation surface corresponding to different real-life subjects to be simulated. Other methods of removable attaching the 0 porous member can be used in alternate embodiments, provided a seal is formed through which the fluid does not leak. Such alternative methods include press-fit and snap-fit.

An alternate embodiment of the invention will now be described with reference to Figure 3.

The construction of this embodiment is the same as the first, save as described below.

In this embodiment, the pores in the porous member are provided by a plurality of tubes 18 which are embedded in an impermeable matrix 20. One end of the tubes 18 is open and this end forms the pore in the wound simulation surface. The other end of the tube extends through the depth of the wound simulation chamber and onwards to the opposite wall 22 where it is embedded in an impermeable matrix thereby sealing that end of the tube.

The tubes are, however, permeable to the liquid and therefore liquid may enter the tubes through their walls. This is illustrated by arrows 24 in figure 3. Because the liquid can only enter the tubes by their permeable walls, there is significant resistance to the fluid flow, which acts to contain the liquid within the chamber in the absence of a pressure applied externally.

In an alternate embodiment, the tubes are sealed at one end but not embedded in an impermeable matrix at that end. This allows easy removal of the wound simulation surface from the wound simulation device, without also requiring removal of the opposite wall of the wound simulation device.

In another alternate embodiment, the tubes are open at their other end in the chamber, allowing liquid to enter the tubes via this open end. In this embodiment, the tubes can be either permeable or impermeable.

In a further alternate embodiment, the porous member is formed by adapting a dialysis filter such that the pores in the surface are provided by the capillaries in the dialysis f lter.

It is possible to use reject-grade dialysis filters for this purpose giving an easy supply of materials for the construction of the wound simulation device.

The precise dimensions of the pores used in the above embodiments can be determined by the skilled person considering that liquid should preferably not emerge from the pores l o when the wound simulation surface is oriented downwards in the absence of an applied back pressure. In that orientation the liquid will tend to drain through the pores by the action of its own weight. Suitable dimensions can be calculated with knowledge of the viscosity of the liquid in the chamber 4. A typical viscosity of the simulated wound exudate used is about 1.6 to about 2.4 milliPascal seconds.

The above embodiments all have the advantage that, as long as there is sufficient space in the chamber to hold a reserve of liquid to be supplied from the pores, the depth of the device can be minimised as much as is practical. It is possible for the device to have depths of less than 5cm and makes it suitable for implantation in synthetic body parts, allowing an absorbent dressing to be tested on a model with the same shape a real body part. This opens up a wide range of new testing possibilities which are not possible with other designs. Notably, dressings can be tested in a vertical or tilted orientation, allowing the effects of sagging on the dressing to be investigated. Furthermore, the device can be used in tests in which it is moved to simulate movement of a real-life body part, giving greater validity to experimental results.

Claims

1. A wound simulation device comprising: a chamber for a simulated wound exudate liquid; a porous member having a wound simulation surface which forms part of the s exterior of the device, the wound simulation surface having a plurality of pores in fluid communication with the chamber; and a pressurization device for applying pressure to the liquid in the chamber; wherein applying pressure to the liquid in the chamber causes the liquid to emerge from the pores in the wound simulation surface.

lo

2. A device according to claim l, wherein the porous member comprises: a matrix formed from an impermeable material; and a plurality of ducts extending through the matrix; wherein the ducts are in fluid communication with the chamber and have a first end opening onto the wound simulation surface thereby forming the plurality of pores.

3. A device according to claim 2, wherein the ducts extend substantially straight through the matrix.

4. A device according to claim 2, wherein the ducts are formed by a plurality of tubes having first and second ends, the tubes embedded in the matrix at or towards the first end and extending from the first end into the chamber.

5. A device according to claim 4, wherein the walls of the tubes are permeable to the simulated wound exudate liquid.

6. A device according to claim 4 or 5, wherein the device further comprises a sealing member contained in the chamber or defining a wall of the chamber, and wherein the second ends of the tubes are embedded in the sealing member to close the second end to flow of simulated wound exudate liquid. l

7. A device according to any one of claims 4 to 6, wherein the tubes are permeable to the simulated wound exudate liquid.

8. A device according to any one of the preceding claims, wherein the diameter of the pores is less than about 0.2 mm, preferably less than about 0.1 mm.

9. A device according to any one of the preceding claims, wherein the area of the wound simulation surface occupied by the pores is at least about 5%, preferably at least about 10% of the surface area of the wound simulation surface.

10. A device according to any one of the preceding claims, wherein the mean number of pores per cm2 is at least about 100.

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1 1. A device according to any one of the preceding claims, wherein the wound simulation surface is polished.

12. A device according to any one of the preceding claims, wherein the wound simulation surface is convex or concave.

13. A device according to any one of the preceding claims, wherein the depth to s which the device extends from the wound simulation surface is less than about 5 cm.

14. A device according to any one of the preceding claims, wherein the device includes a quantity of simulated wound exudate liquid within the chamber.

15. A device according to claim 14, wherein the simulated wound exudate liquid is an aqueous solution, such that the viscosity at 37 C is between about 1.6 and about 2.4 milliPascal seconds.

16. A device according to claim 14, wherein the simulated wound exudate liquid comprises animal blood plasma. \

17. A device according to claim 15 or 16, wherein the dimensions ofthe pores in the wound simulation surface are chosen such that, when the wound is oriented downwards and the pressurization device applies no additional pressure to the simulated wound exudate liquid, substantially no simulated wound exudate liquid emerges from the pores.

18. A device according to any one of the preceding claims, wherein the pressurization device is a pump, preferably an infusion pump, and the wound simulation device preferably further comprises a controller for controlling the pump.

19. A model of a human or animal body part incorporating a wound simulation device according to any one of the preceding claims.

lo

20. A mannequin incorporating a model of a human or animal body part according to claim l9.

21. A wound simulation device substantially as hereinbefore described with reference to the accompanying drawings.

22. A model of a human or animal body part incorporating a wound simulation device s substantially as hereinbefore described with reference to the accompanying drawings.

23. A mannequin incorporating a wound simulation device substantially as hereinbefore described with reference to the accompanying drawings.