Portable medical device system

Abstract

The present invention provides an apparatus comprising a wound dressing connected to a fluid container via a pump, wherein the wound dressing is in communication with a mechanical pressure control valve, the fluid container is provided with an inlet and an outlet. Also provided are (i) flexible fluid containers comprising of at least two layers of film with an integrated vent, (ii) wound dressings and (iii) a multi-compartment wound fluid container comprising at least two internal compartments and provided with an outlet and an inlet, in which the container comprises a microporous fluid separator which divides the at least two internal compartments, wherein the microporous fluid separator permits gas flow between the compartments and prevents fluid flow to the outlet of the container. Other apparatus provided comprises a means for detecting the level of fluid within a multi-compartment wound fluid container as described. The invention also provides a system for applying a sub-atmospheric pressure to a wound dressing on a patient using devices and apparatus of the invention and methods of treatment of wounds using such apparatus, devices and systems of the invention.

Claims

1. An apparatus comprising a wound dressing, a fluid container having an inlet and an outlet, tubing which interconnects the wound dressing and the fluid container and which forms a fluid flow path therebetween, a filter on the fluid flow path downstream of the inlet, a peristaltic pump which accommodates said tubing so as to be isolated from the fluid flow path; and a mechanically automatic pressure control valve on the fluid flow path interposed between the wound dressing and the peristaltic pump to encourage flow away from the wound site, wherein the mechanically automatic pressure control valve is upstream of the filter.

2. The apparatus as claimed in claim 1, wherein said mechanically automatic pressure control valve comprises a port to atmosphere which is set to open at a predetermined pressure to maintain a constant pressure by permitting airflow into the tubing.

3. The apparatus as claimed in claim 2, wherein said mechanically automatic pressure control valve further comprises a seal downstream of the port and a spring downstream of the seal.

4. The apparatus as claimed in claim 3, wherein the port, seal and spring are spaced away from the fluid flow path to prevent blockage whilst regulating air flow through the mechanically automatic pressure control valve to the tubing.

5. The apparatus as claimed in claim 1, wherein the fluid container is flexible.

6. The apparatus as claimed in claim 1, wherein the wound dressing has a porous layer covered by a flexible film layer enabling direct-contact wound compression.

7. The apparatus as claimed in claim 1, wherein the filter has at least one of hydrophobic and oleophobic properties to prevent or inhibit liquid passing but allowing gas to pass.

8. The apparatus as claimed in claim 1, wherein the flier is encapsulated by the fluid container to prevent undue expansion of the fluid container.

9. The apparatus as claimed in claim 1, wherein the peristaltic pump is separate and upstream of the fluid container.

10. The apparatus as claimed in claim 1, In which the pressure control valve is one of: a check valve and a duck bill valve.

11. The apparatus as claimed in claim 1, in which the outlet of the fluid container is a gas vent.

12. The apparatus as claimed in claim 1, in which the outlet of the fluid container is a valve.

13. The apparatus as claimed in claim 1, in which the fluid container comprises at least two layers of a polymeric film and a vent which comprises the filter.

14. The apparatus as claimed in claim 1, further comprising a pressure pad or pressure sensitive switch for detecting the level of fluid within the fluid container, in which the container is constrained by a flexible strap.

15. The apparatus as claimed in claim 1, further comprising a pressure sensitive switch for detecting the level of fluid within the fluid container.

16. The apparatus as claimed in claim 15, in which the pressure sensitive switch is a micro-switch.

17. The apparatus as claimed in claim 14 in which the flexible strap has a correct position, wherein the correct position of the flexible strap is detected by a proximity switch.

18. A system for applying a sub-atmospheric pressure to a wound dressing on a patient, wherein the system comprises an apparatus as claimed in claim 1 and an electric circuit which operates the pump.

Description

(1) In the application reference is made to a number of drawings in which:

(2) FIG. 1a and FIG. 1b show systems of the invention

(3) FIG. 2 shows a system of the invention

(4) FIG. 3 shows a flexible fluid container of the invention.

(5) FIG. 4 shows a flexible fluid container of the invention

(6) FIG. 5 shows an alternative embodiment of a flexible canister of the invention

(7) FIG. 6 shows an alternative embodiment of a flexible canister of the invention

(8) FIG. 7 shows an alternative embodiment of a rigid canister of the invention

(9) FIG. 8 shows an isometric view of an embodiment of an apparatus of the invention

(10) The invention will now be further described in detail with reference to the following Figures and Examples which are not to be construed as being limitations to the invention.

(11) FIG. 1a and FIG. 1b show systems of the invention whereby a wound dressing is connected to a fluid container (11) via tubing (5) which is suitable for use with a peristaltic pump. Connected in proximity to the wound dressing is a pressure control valve (13) which limits the negative pressure produced at the wound site to a predetermined value. The fluid container (11) can either be rigid or may be flexible to allow conformity to the patient (this is described in further detail in FIG. 3 below). The container has an inlet (2) and an outlet (4). Between the container (11) and wound dressing (15) a peristaltic pump (3) is used. The tubing (5) is connected through the peristaltic pump. The container has a means to allow the gas to escape such as a vent or valve (1) positioned at the outlet (i.e. an air control valve), thereby preventing over inflation of the container in its flexible form and would typically incorporate a hydrophobic filter to ensure the fluid is contained. The container could also contain a means of reducing odour such as an activated charcoal filter or a superabsorbent gel to solidify the fluid. An example of a suitable style of container for this purpose is a 540 ml vented urinary bag such as that manufactured by Hollister Inc., USA.

(12) FIG. 1a shows one embodiment of the invention of a system in which the outlet (4) comprises a vent suitably composed of a gas permeable hydrophobic membrane as described herein. FIG. 1b shows an alternative embodiment in which the outlet (4) comprises an air control valve (1) as described herein.

(13) FIG. 2 shows a wound dressing (15) connected via tubing to a container (11) where the wound dressing is provided with a negative pressure control valve (13). The container (11) is connected to a hydrophobic filter (7) via tubing (9). The filter is connected to an air control valve (1) by tubing (5) that is suitable for use with a peristaltic pump (3). The container (11) can either be rigid with a hydrophobic filter integrated within, or a flexible container as described in FIGS. 3 and 4. In the latter two embodiments, the hydrophobic filter (7) is no longer present externally since a corresponding filter is present within the container.

(14) A pressure control valve (13) as shown in FIGS. 1 and 2 is positioned in reverse to its normal orientation between the fluid container (11) and the wound site dressing (15) to provide better pressure control, due to the closer proximity to the area requiring regulated pressure and therefore is not prone to the hydrostatic head effect caused by pulling fluid upwards. Additionally by placing the pressure control mechanism on the wound side of the hydrophobic filter then the effect of the pressure drop across the filter is eliminated. Typically the pressure control valve would be set at a pre-determined pressure such as 2.5 PSI (129 mmHg) with a 5 to 15% crack tolerance. A standard arrangement for this type of valve is 3 ports with the control element consisting of a polymeric seal such a silicone and a stainless steel spring inside a Polypropylene or similar injection moulded body.

(15) An example of this is available from Qosina Part No. D002501. A large range of alternative valve arrangements could be used including Duck Bill style valves orientated in a reverse configuration i.e. with the valve seal lips on the fluid side. Another alternative is an Umbrella style control valve. A traditional style ball and spring valve could also be used. It is envisaged a purpose made vacuum valve could also be used. Typically a range of dressings will be available for differing wounds such as leg and pressure ulcers and the dressings will be matched in size and pressure settings to accommodate this. Additionally valves will be available that can be adjusted by the user and may be situated at various positions from the dressing to the negative pressure source.

(16) One method of negative pressure generation is by a peristaltic pump (3) as shown in FIGS. 1 and 2. This pump allows for a combined, disposable set of components to be used. No fluid comes into contact with the pump and this omits the requirement for protective filter systems for the pump. With the use of the pressure control valve (13) that limits the pressure at the wound site, the control system for the pump is limited. A potential peristaltic pump could be the 400F/A Single Channel Precision Pump by Watson Marlow Alitea. Other types of positive displacement pumps could be used and integrated into the tubing set such as a disposable pump head, an example of this type of pump is the CAPIOX® Disposable Centrifugal Pump manufactured by Terumo, USA. Another example of a pump that could be used is a Kamoer KPP Peristaltic dosing pump that has additional advantages of a small size and low power requirements.

(17) An alternative to a peristaltic pump is a small diaphragm vacuum pump with a flow rate of between 1.5 litres and 2 litres per min at free flow with a maximum vacuum of 370 mmHg an example of this would a pump manufactured by KNF Neuberger GmbH of Frieburg, Germany Model number NMS020L. A range of other vacuum pumps could be utilised with a range of flow rates up to 10 litres per min if required. For the community application minimum user controls are required so normally the device would be pre-set at a vacuum level slightly above the required wound site pressure level to account for variances in pressure due to height differences etc. In practice this will result in a small constant flow of air at the wound site which will ensure there is mobility of the wound fluid from the dressing to the container.

(18) FIGS. 3 and 4 show flexible fluid containers of the invention. The hydrophobic filter (29) is encapsulated between the two films (21, 23) that form the container and this effectively produces a wet side and dry side over the entire area of the filter. Sections of a spacer material (25, 27) prevent the film collapsing and occluding the filter and also provide a means of manifolding the fluid evenly within the container. Because the filter covers the entire area of the container in any orientation a section of the filter will be open until the container fills to its full capacity. The filter surface is treated to ensure it is both Hydrophobic and Oleophobic and therefore will resist wetting by either water based liquids or fats and lipids. This means that splashing of fluids will bead on the surface and not spread over the surface of the filter. The super absorbent gel also immobilises the fluids and prevents splashing.

(19) The fluid container consists of two layers of Polyurethane film (21, 23) such as that manufactured by Chorino Grade UE80 or Epurex Platilon Grade U073 manufactured by Bayer. PVC material could also be used, the material used in the construction of blood bags is particularly suitable, an example of this type of material is Renolit Solmed Transufol Seta 3224 manufactured by Renolit, located in the Netherlands. Within these two layers a hydrophobic filter (29) such as Versapor filter membrane 0.8 micron manufactured by Pall Corporation is encapsulated by RF welding, Ultrasonically welding, heat impulse welding or bonding to the film layers. Alternative membrane pore sizes could be used ranging from 0.2 micron to 10 micron could be used. Either side of this filter is sections of a spacer material (25, 27)); an example of this is manufactured by Mueller textiles of Germany, Grade 5754. Another example is Stimulite® manufactured by Supracor® of USA, which is a flexible bonded honeycomb polymer which provides resistance in one plane but allows flexibility in the others. Additionally other materials may be added such as an active carbon filter to reduce odour or a super-absorbent gel such as a Sodium Polyacrylate composition to partially solidify the fluid (this would be incorporated into 27). Connected to the flexible container assembly an inlet (19) and outlet (31) tube or port is hermetically joined by RF welding, UV or solvent bonding or by a similar process.

(20) The outlet tube or port is connected to a negative pressure air source (indicated by air flow direction arrow (33)) that evacuates the air within the system and at the wound site dressing. Typically the pressures will vary between 25 mmHg and 200 mmHg.

(21) The inlet tube (19) is connected to a wound dressing (and air flow direction arrow (17) shows the flow of liquid from the wound into the dressing). Various volumes of the flexible container can be produced according to the required clinical application but for the homecare application then this typically would be 100 ml. Utilising this principle, containers with different capacities could be produced between 50 ml and 5 litres.

(22) FIG. 5 shows an end section of an alternative flexible container. FIG. 6 shows a front section of the fluid container (35) is a flexible sealed container of a PU film which is RF Welded together. A fluid inlet (49) is bonded into the film. A vacuum source outlet (37) is fitted into the fluid container at (45). Within the sealed fluid container is a flexible, non-compressible material (47) that prevents the fluid container from self-sealing, thereby preventing fluid to be drawn into the fluid container. The vacuum source tube (37) fits into a cylindrical plastic component called the filter housing (39). This has a series of ribs along the length that prevents the film of the fluid container from adhering to the hydrophobic filters (41) when subjected to negative pressure. Holes (43) in the housing (39) allow gas to pass between the interior of the filter housing and the space around the housing. The benefit of this design is to allow for a multidirectional fluid container whereby only until the canister is completely full will the filter membrane be occluded which will prevent further fluid uptake.

(23) FIG. 7 shows a cross sectional front view of a rigid fluid container (63) with fluid inlet port (59) and outlet port (51). The outlet port passes through (63) and is fixed at the intersection. The outlet port (51) is connected to a coiled, flexible tube (53). This is fixed to a hollow sphere (53) which has a plurality of holes allowing gas communication between the hollow interior of the sphere and the fluid container. Surrounding the sphere (57) is a hydrophobic filter (55) which covers the holes and prevents fluid passing into the sphere but allows gas to pass from the inlet (59) through the sphere and through the outlet (51) to a vacuum source. When fluid (61) is present in the fluid container, the sphere is allowed to float on the level at any orientation whilst still being connected via the coiled tubing (53).

(24) The embodiment as shown in the drawings has been prototyped and tested on the bench. This proved that pressures could be maintained within a small tolerance at the wound site utilising a mechanical valve arrangement over a range of conditions which simulated real clinical conditions. Additionally it was proved that a flexible fluid container could be produced with a hydrophobic filter barrier. The prototype was able to function under 200 mmHg of negative pressure and uptake fluid into the fluid chamber. No fluid passed through the filter barrier. The following test results show the invention in practice.

(25) FIG. 8 shows an isometric view of an apparatus of the invention in which a wound dressing (15) is in communication with a mechanical pressure control valve (13). The wound dressing is connected via tubing (5) to a fluid container (11) via a pump (3).

EXAMPLES OF THE INVENTION

(26) Testing was carried out utilising the arrangement as described in FIG. 1. The test equipment and components used were as follows: Watson Marlow 102U Bench top Peristaltic Pump Watson Marlow Peristaltic tubing Pumpsil 913A (4.8 mm bore×1.6 mm Wall) Test dressing (100 mm×50 mm×30 mm) 150 cc Volume Pressure control Valve. Qosina D002501. 2.5 PSI Cracking pressure+1-15% Manual Vacuum Gauge. SM Gauge. 1.6% Accuracy over Full Scale Deflection.

(27) Test 1 (Pump Between Dressing and Fluid Container) See FIG. 1

(28) TABLE-US-00001 Test 1a: Closed system, no pressure control valve Pump Fluid Pressure speed flow at dressing Comment 200 RPM  0 >350 mmHg Closed system 30 RPM 0 >200 mmHg 30 RPM to   200 mmHg Pressure not reduced by reducing 5 RPM pump speed. System needs to be opened to achieve pressure decay

(29) TABLE-US-00002 Test 1b: Pressure relieve valve (inverted) placed at dressing Pump Fluid Pressure speed flow at dressing Comment  30 RPM 0 120-125 mmHg Reached 150 mmHg (cracking pressure) in 60 seconds stabilised to 120 mmHg 200 RPM 0 120-130 mmHg Valve compensated for increased flow to maintain constant pressure

(30) TABLE-US-00003 Test 1c: Fluid introduced, Pressure valve fitted Pump speed set to maintain a constant fluid flow Pump Fluid Pressure speed flow at dressing Comment 30 RPM 12.5 ml/hour 120-125 mmHg 30 rpm maintains constant flow rate

(31) TABLE-US-00004 Test 1d: Height difference introduced (dressing set at 0.5 metres below the pump unit) Pump speed Fluid flow Pressure at dressing Comment 30 RPM 12.5 ml/hour 120-125 mmHg No pressure drop off due to height difference

(32) TABLE-US-00005 Test 1e: Overnight test using realistic wound exudate flow rates Pump speed Fluid flow Pressure at dressing Comment 5 RPM 2.25 ml/hour 120-125 mmHg Test run for 20 hours, 45 ml fluid removal

(33) TABLE-US-00006 Test 2: Inline container test. See FIG. 2 Pump Pressure speed Fluid flow at dressing Comment 62 RPM 210 120 mmHg Rapid filling test, 14 minutes to full ml/hour canister (50 ml). Pressure maintained at dressing side

(34) Conclusion of Testing

(35) Test 1a). With a closed system (air only) utilising a peristaltic pump it was demonstrated that the pressure could not be controlled adequately, as the pump speed increased the pressure correspondingly increased to in excess of 350 mmHg. Decreasing the pump speed did not effectively reduce the pressure and it remained at over 200 mmHg even at the lowest setting used of 5 RPM. Any pressure decrease was only due to connector leakages and the breathability of the drape.

(36) 1b). With the pressure valve fitted at the dressing site at full speed of 200 mmHg the wound site pressure was limited to 120 mmHg+/−2.5 mmHg with a momentary maximum of 150 mmHg as the valve initially opened.

(37) 1c). With fluid introduced at 30 rpm a constant flow rate was achieved. The fluid flow was aided by small amounts of air being drawn through the valve which allowed mobility of the fluid from the dressing to the container.

(38) 1d). Changing the height of the dressing relative to the pump (0.5 metres) did not result in any measurable pressure change at the website.

(39) 1e). A longer duration test (20 hrs) showed over an extended period a low level of fluid (2.25 ml per hour) was withdrawn at a constant rate without any issues or alterations in parameters, the flow rate was set at a very low flow rate (5 rpm) which results in very low noise levels and power consumption.

(40) This flow rate is equable to certain types of leg and foot ulcers.

(41) Test 2). The inline container configuration was tested at a relative high flow rate 210 ml/hour to stress the filter. The container filled to capacity, maintained the target pressure and the filter was not breached.

(42) Results of the Testing:

(43) A standard pressure control valve was used in the reverse orientation i.e. the normal outlet to atmosphere was connected to the fluid side, the variance of negative pressure readings was well within the stated manufacturers tolerance of +/−15%, which would normally relate to a total tolerance of 38 mmHg at the normal working pressure. The pressures measured after the valve originally opened and the pressure stabilised to be in the order of 10 mmHg total working tolerance.

(44) This is believed to be significantly more accurate than electronic control systems that rely on multiple conduit pathways and multiple electronic components.

(45) The introduction of the pressure valve had a second effect beyond pressure control that was not anticipated, this was to allow the introduction of small amounts of air into the system at the dressing site. This had two effects, the first was to allow constant flow of fluid from the dressing at a very low flow rates, the second was to provide a mechanism to reduce pressure at the wound site when sealed pump systems such as a peristaltic pump is used. Additionally the valve had the effect of aerating the fluid evenly causing mobility which appeared to be different in nature when a basic leak is introduced through an orifice. One explanation for this may be due to the design of the valve and the characteristics of the sprung loaded component and seat, although this valve is designed to relieve positive air pressure it has an advantageous effect in regulating air inflow under negative pressure when fitted in reverse. A second major advantage of the valve arrangement is due to the reverse nature of the sprung loaded action when fluid is forced back into the dressing the valve will be forced closed effectively sealing the dressing. Several scenarios exist when this can happen; one example is when therapy is paused for when the patient is taken a shower, in this case gravity or pressure against the dressing could cause fluid to pool in the dressing. Normally if the dressing contained any passage to atmosphere then fluid could leak out causing an infection risk.

(46) In the case of devices that contain sensing tubes or conduits to the control unit to control pressure these can potentially fill with fluid when negative pressure is paused that may cause blockages, this situation is eliminated in the present invention.