WO1998017340A1

WO1998017340A1 - Pressure controllable hyperbaric bag for leg wounds

Info

Publication number: WO1998017340A1
Application number: PCT/US1997/018829
Authority: WO
Inventors: Joseph R. Westwood
Original assignee: Geary, Paul, A., Jr.; Geary, Sean, M.
Priority date: 1996-10-22
Filing date: 1997-10-17
Publication date: 1998-04-30
Also published as: AU4987697A

Abstract

A hyperbaric leg bag (10) for treating a wound with therapeutic gas to expedite healing; having a maximum pressure release valve (18) that can be set at a desired maximum treatment pressure and that is not connected to the gas supply (17), and a non-elastic wide sealing tape (14) that adhesively affixes the bag to encompass the leg.

Description

PRESSURE CONTROLLABLE HYPERBARIC BAG FOR LEG WOUNDS

RELATED PATENT APPLICATIONS This Patent Application is a Continuation of my U. S. Patent Applications Serial No. 08/649,872 filed May 13, 1996 and Serial No. 08/643,486 filed May 6, 1996.

BACKGROUND OF THE INVENTION

Many difficult to heal wounds, particularly where there is damage to the blood circulation system, are now treated with a gas such as oxygen to supplement the oxygen to the wound area that is not being satisfied by the damaged blood circulation system. Initially, this was done by installing a gas chamber around the wound^nd flowing oxygen continuously over the wound area These chambers were rigid, heavy, difficult to clean between uses, and uncomfortable for the patient. Recently it has been discovered that continuous flow of oxygen is not necessary, and that effective hyperbaric treatment can be obtained by using a single adequate stationary charge of oxygen that is retained in a flexible chamber in contact with the wound for the treatment period. Unlike the continuous flow type devices, these devices do not need to be continuously attached to the oxygen supply during treatment, allowing mobility for the patient

More recently flexible topical hyperbaric devices have been developed. U.S. Patent No. 5,145,697 assigned to Topox, Inc. discloses aflexible hyperbaric bag that has a hole through the side of the bag that is to be exposed to the area to be treated. The periphery of the hole is reinforced with a strong ring. A belt structure affixes the bag over the area to be treated, and gas such as oxygen inflates the bag to the desired gas pressure. The device contains a gas inlet for charging, and a gas pressure release valve which is constructed for a fixed single maximum gas pressure. Unlike earlier hyperbaric devices, the device of this patent does not require a constant supply of gas. Although it is known that there are different narrow optimum pressures ranges for treating arterial wounds and venous wounds, the Topox bag is not designed to operate at a specific prescribed pressure. The devices cannot be adjusted to an optimum pressure in response to a wound diagnosis.

Dyson-Cantwell U.S. Patent No. 5,478,310 discloses a hyperbaric oxygen bag for use on leg wounds. It comprises a polyethylene bag to be secured around the leg and a gas supply line. This device does have a pressure control means but it is connected to the gas supply line. As shown in Fig. 3, the chamber may have a tape covering holes in the gas bag that can be pulled off the holes during treatment to decrease gas pressure. Using mis device it is difficult, if at all possible, to set and maintain the treatment pressure within the range of desired treatment pressures.

The prior art also discloses numerous topical hyperbaric devices that apply a continuous supply of gas flowing through the wound area These of course require continuous connection to the gas supply, eliminating patient mobility during treatment

Some of these prior art continuous flow devices have pressure control valves that are connected to and control the gas input. See St i val a U.S. Patent 4,224,921; Tramell U.S. Patent 5,029,479; and Freeh U.S. Patent 4,772,259.

Pressure control means connected to the gas supply have several disadvantages. When the gas supply is disconnected or shut off, the pressure control means is disconnected or shut off and so the pressure control means is no longer functional. This is particularly important for devices designed for static treatment use. Also, accurate control of the treatment zone pressure is difficult because such valves are not directly measuring the treatment zone pressure. Furthermore, putting a pressure control valve in the gas supply line requires using an additional device, in addition to the gas cylinder or hospital gas supply line. In such a device the gas supply line cannot be directly connected to the hyperbaric treatment device treatment zone. For leg wounds, recently it has been the practice to enclose all, or the lower part of the leg in a chamber or bag. See Fischer U.S. Patent 3,744,491; Freeh U.S. Patent 4,722, 259; and Dyson-Cantwell U.S. Patent 5,478,310. The Fischer device has a an expensive rigid collar that surrounds the leg, and is sealed to the leg with a stretchable elastic band. The use of elastic fastening means around the leg tends to restrict the leg circulation in the leg, where poor circulation often is already a problem. Similarly, the Freeh device employs an elastic cuff around the leg to seal the chamber. The Dyson-Cantwell device, which represents the most current art, is aflexible leg bag that has a pressure gauge connected directly to the intake line or to the bag, but is does not have any pressure release valve independent of the inlet line that can control the maximum treatment zone pressure during the course of the treatment.

SUMMARY OF THE INVENTION

The present invention relates to a topical hyperbaric device for treating a leg wound with a therapeutic gas to expedite healing. The device comprises a lexible substantially gas impermeable sheet material bag large enough to encompass at least part of a leg, the bag being capable of applying and confining the therapeutic gas to a restricted therapeutic gas treatment zone; means to affix the material to make a restricted therapeutic gas treatment zone encompassing the wound, wherein the gas is kept in contact with the wound and is restricted from escaping from the treatment zone, the affixing means comprising a non-stretchable band at least 1 1/2 inches in width having a surface coating of a pressure sensitive adhesive surface that will be in contact around the patient's leg, seal the bag, and retain the gas in the treatment zone; means for introducing the therapeutic gas into the treatment zone; and a pressure release valve capable of setting the maximum gas pressure of the treatment zone to the desired treatment pressure during treatment of a patient, which valve is not in direct communication with the means for introducing the gas. The valve automatically releases gas from the treatment zone when the maximum pressure is exceeded, which pressure can be pre-set at the desired maximum pressure in the zone. Preferably the valve is manually adjustable so that the desired maximum pressure of the treatment zone can be set accurately at the appropriate gas pressure determined by diagnosis.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

For a detailed description of the preferred embodiments of the topical hyperbaric device of the present invention, reference is made to the drawings in which:

Figure 1 is a side view of a preferred hyperbaric device of the present invention for treating lower leg wounds.

Figure 2 is a side view of the device of Figure 1 installed encompassing a patient's lower leg.

Figure 3 is a side view of the device of Figure 1 in a preferred form for putting on a patient's leg.

Figure 4 is a side view of a preferred device of the present invention for treating the entire leg of a patient

Figure 5 is a schematic cross section of a manually adjustable pressure release valve suitable for use in the device of Figure 1; and

Figure 6 is a schematic cross section of a valve having a readily replaceable fixed pressure release valve, also suitable for use in the device of Figure 1.

DEFINΓΠONS

The term "maximum gas pressure" means the not-to-be exceeded highest gas pressure.

The term "optimum gas pressure" means the most effective therapeutic gas treatment pressure for achieving desired healing. Ihe term "desired maximum gas pressure" means the highest gas pressure to be used in a particular treatment It may be the exact pressure prescribed from the diagnosis, or it may be somewhat higher than the prescribed pressure to achieve an average of close to the prescribed pressure during treatment. In continuous flow treatment the "desired maximum gas pressure" normally is the prescribed pressure.

The term "substantially maintain the gas pressure", as used herein in reference to the treatment zone gas pressure, means the gas pressure is maintained close to the desired gas pressure by restricting escape of gas and/or adding gas during treatment. "Substantially" means to include deviation from the precise desired maximum gas pressure; this deviation may be as much as 30% or more so long as the deviation is not too much for adequate treatment in the particular case.

The term "retained", as used herein with respect to gas in the treatment zone, means the gas is kept in the treatment zone (static treatment, not continuous flow treatment). "Substantially retained" refers to the normal situation in static treatment wherein some gas leakage is expected, possibly requiring period replenishment

The term "restricted", as used in reference to the treatment zone gas, means excessive uncontrolled escape of gas from the treatment zone is prevented.. In static treatment, optimally "restricted" and "retained" mean completely prevented from escaping. Of course this level of restriction is seldom, if ever achieved, and so the term "restricted" is intended to include substantial gas escape so long as adequate therapeutic gas is maintained in the treatment zone. "Restricted" also applies to continuous flow treatment, where gas is continuously fed and exited from the treatment in a controlled manner while maintaining treatment zone pressure; uncontrolled escape of gas is minimized.

The term "substantially gas impermeable", as used herein with respect to the sheet material, means gas impermeable to the extend needed to prevent excessive gas escape from the treatment zone through the sheet material. Total gas impermeability seldom is needed, particularly for continuous flow treatment devices.. However, generally high impermeability is desirable for static treatment devices.

The term "continuous flow treatment" means treatment during which gas is substantially continuously added and exited through most of the treatment period. It may include periods when the gas supply pressure is decreased, allowing treatment at a lower pressure, but the gas supply remains connected.

The term "static treatment" means treatment during which an initial charge of gas is retained in the treatment zone for a prolonged treatment time period, and there is no continuous flow of gas to the treatment zone during treatment. In static treatment, intermittent gas additions may be needed during the treatment period to replace escaped gas and maintain gas pressure.

The term "leg" means all or part of one or bom legs of a patient

The term "encompass", when referring to a leg in the hyperbaric bag, means to surround in three dimensions that portion of the leg and foot, including the bottom of the foot.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In using the hyperbaric leg bags of the present invention, before treatment the leg wound is diagnosed to determine whether arterial or venous and the desired maximum treatment gas pressure, duration and sequence of treatments. Normally, if the wound is arterial an optimum treatment pressure in the range of about 25-35 mm Hg, and if venous a desired pressure in the range of about 15-20 mm Hg, is therapeutically optimal. Typically a 7 day treatment period is prescribed comprising identical one to two hour treatments on days 1, 2, 3 and 4, followed by no treatment on days 5 through 7, which treatment usually is repeated one or more times. An appropriate topical hyperbaric device capable of receiving gas from a gas supply source is then selected. This device comprises a means not in direct communication with the gas supply to accurately set the maximum treatment zone gas pressure at the desired maximum pressure determined by the diagnosis. This desired maximum pressure will be set to give an average treatment pressure, usually within the optimum ranges set forth above. The desired maximum pressure setting is achieved either by selecting a release pressure valve that is fixed at the appropriate desired maximum pressure, or using a hyperbaric treatment device having a manually adjustable maximum pressure valve and manually setting it at the desired maximum pressure.

The leg, or legs, is then inserted into the leg bag up beyond the wound, and the bag is affixed by a sealing tape around the leg above the wound to encompass the wound and make a treatment zone including the wound. The leg bag, which has an opening much larger than the leg circumference, is folded over upon itself tightly into a pleat and the sealing tape is affixed completely around the leg (or lower body) as tightly as possible without constricting the leg. The excess length of sealing tape, which extends substantially around the periphery of the top area the bag on the inner surface, is sealed to itself to complete the closure and formation of the treatment zone, into which gas is introduced and restricted from escaping.

Sufficient therapeutic gas is then introduced into the treatment zone to maintain the gas pressure therein substantially at the desired maximum pressure. The leg bag will retain a single static gas charge for a prolonged period of time, the duration of which depends on how well the device is able to restrict the gas and retain it in the treatment zone. It has been found to be undesirable to pull the sealing tape tightly abound the leg because this can restrict blood flow. Therefore, it is necessary to add gas periodically to substantially maintain the desired maximum pressure. When gas is added, addition is continued until the pressure release valve starts to release gas, indicating that the desired maximum pressure in the treatment zone has been reached. The need for additional gas can be noted by observing diminished volume in the treatment zone, i.e. a softening or flattening bag. Alternatively the device may have a pressure gauge connected to the treatment zone.

The present invention product comprises a flexible pressure controllable topical hyperbaric device for treating leg wounds and lesions with a therapeutic gas, particularly oxygen. The device comprises aflexible substantially gas impermeable sheet material bag large enough to encompass the leg up beyond the leg wound. The bag, bounded by the sealing tape and leg, make up a restricted treatment zone that is capable of confining a therapeutic treatment gas to the therapeutic treatment zone, which zone includes the area of the wound to be treated The leg bag has means to affix the bag encompassing the leg, which means comprises a substantially non-stretchable band of tape at least 1 1/2 inches wide, which tape is affixed substantially air tight to the bag circumferentially around the upper end of the bag near its opening periphery. The bag, and its opening are larger than the leg, enabling easy insertion of the leg into a treatment zone that is larger than the leg area to be treated. The sealing tape has a pressure sensitive adhesive on its inner surface that will be in substantially air tight (hermetic) sealing contact around the leg. The sealing tape, when sealed to the leg and the excess length sealed upon itself, will retain the gas in the treatment zone. The bag has an inlet means to deliver gas to the treatment zone; and at least one maximum pressure release valve means that is in direct communication with the treatment zone but is not in direct communication with the gas supply.

Preferably a manually adjustable pressure release valve means is used because such a valve means can be set easily and accurately before use to whatever desired maximum gas pressure is prescribed, insuring the correct pressure for the particular treatment. For example, when treating arterial wounds average treatment pressures in the range of 25-35 mm Hg above atmospheric are optimum, whereas when treating venial wounds pressures in the range of about 15-20 mm Hg. are optimum. A standardized hyperbaric treatment device having a manually adjustable pressure release valve means

o- can be used for whatever desired maximum pressure is prescribed. Desirably the valve means can be set accurately (either by an adjustable valve or by selecting the appropriate fixed pressure release valve element) accurately within the range of about 3 to 60 mm Hg., with an accuracy of about 10 mm Hg., preferably 5 mm Hg.

Referring to Figure 1 and 2, a preferred leg bag treatment device 10 of the present invention comprises a bag made of flexible gas impermeable sheet material that is capable of confining gas and retaining it in a restricted therapeutic gas treatment zone 11. The bag is of sufficient size to receive the lower part of the patient's leg 12 up beyond the calf, thereby encompassing the patient's lower leg 12. The bag 10 has an access opening 13, through which the lower leg 12 is inserted, and afoot zone 15. Inside the bag 10 near the opening 13 there is a sealing tape 14 hermetically sealed to the inside surface of the baglO, which sealing tape extends circumferencially around the bag 10. On the inside surface of sealing tape 14 there is a layer of pressure sensitive adhesive of a type suitable for contact with a patient's skia Prior to use, the adhesive layer may be covered by a protective paper release layer. After the leg 12 is inserted into bag 10, the bag is adhesively sealed around the patient's leg 12 by sealing tape 14. Since opening 13 is significantly larger than leg 12, the excess sealing tape 14 that is not affixed to leg 12 is folded back upon itself forming pleat 16 in bag 10.

The lower part of bag 10, sealing tape 14, and the encompassed leg surface define a restricted therapeutic gas treatment zone 11 which including the wound, wherein therapeutic gas is retained in contact with the wound and is restricted from escaping. The treatment zone will retain treatment gas for a significant period of time, the duration of which depends primarily on the treatment zone gas pressure, the width of the sealing tape 14, and how well the tape 14 seals bag 10 to leg 12. In this device, gas inlet tube 17 has a one way valve mat permits intermittent addition of gas, but not escape thereof This fitting is adapted to connect directly with the gas supply. The gas supply can be disconnected for patient mobility without losing treatment zone pressure Maximum pressure release valve 18 is in direct communication with the treatment zone 11; it is not in direct communication with the gas supply or gas inlet 17.Therfore it is responsive to absolute treatment zone pressure, not input gas pressure. As a desirable option, there may be a pressure gauge (nor shown) in communication with bag 10 which shows the treatment zone gas pressure. If so, a single unit comprising the maximum pressure valve and the pressure gauge is preferred, although separate units can be used.

Figure 3 is a preferred form of the leg bag device particularly suited for receiving the leg without excessively contacting the wound with the bag. In addition to the aforementioned elements, this device comprises hoop 18 that surrounds, but is not attached to the bag, located near the top of the bag with the upper rim area 17, normally including sealing tape 14, folded down over the hoop 19. When bag 10 is to be put into use, hoop

19 area is at the top of bag 10, maintaining it open to easily receive leg 12. The cuff area

20 is en pulled upward, releasing hoop 19, which can then be discarded. Hoop 19 keeps the bag 10 open while placing leg 12 in position encompassed by bag 10, avoiding contact with the wound by bag 10. Hoop 19 is a closed loop about the size of the periphery of the top of the bag. It can be any desired shape and made of any inexpensive sufficiently rigid material, such as 1/4 inch rigid plastic tubing, to maintain the opening 13 open to receive the leg 12.

Figure 4 shows a leg bag device of the present invention of suitable size to accommodate the leg up to the thigh. A hoop may also be used with this larger bag device to minimize wound contact by the bag during insertion of the leg into the bag.

Figure 5 schematically shows a manually adjustable pressure release valve 18 suitable for use in the devices of Figures 1-4. This is a screw top valve that increases the treatment zone maximum pressure as screw 29 is screwed down. It comprises plastic cylindrical housing 21 that has an internal shoulder 22 at the bottom end with an opening 23 therein. Valve ball 24 seats on shoulder 22 sealing opening 23 closed. Tension spring

25 fits snugly above ball 24 along the inner sides of housing 21, and exerts the selected release pressure on ball 24. Spring 25 is designed to be able to exert about 5 - 60 mm Hg. on ball 25. Screw top 29 is threaded into the top of housing 21 so that it's plunger end abuts the top of spring 25. As screw 26 is screwed in it compresses spring 25, increasing the pressure on ball 24. When the pressure in the treatment zone exceeds the force of spring 25, ball 24 moves upward in the chamber of housing 21, allowing gas to escape from the treatment zone through opening 23 into the chamber of housing 21 and out through exhaust port 26.

Referring to Figure 6, the pressure release valve need not be adjustable. Instead the valve may be a fixed release pressure female element that is easily inserted or screwed into a male receptacle in communication with the treatment zone. This device also comprises opening 23, ball 24, spring 25 and exhaust port 26. which function the same as there counterparts of Figure 3. A selection of such fixed pressure release elements is made available, from which an element having the desired maximum release pressure setting is selected. These elements may be color coded to indicate their release pressure. When a fixed pressure release valve is used, the need for a pressure gauge is small.

The design of the pressure release valve is not critical. Many different types are suitable. For example, instead of a ball valve as shown in Figure 3 and 4, the release valve can be a baffle valve such as a flap or butterfly baffle valve. Other valves are equally suitable, so long as they are capable of accurately setting the maximum release pressure and are inexpensive and so discardable. If desired the adjustable valve can be calibrated to show the pressure setting. The preferred valve bodies are made of any rigid plastic, although metals such as stainless steel can be used. The spring preferably is steel. Very inexpensive completely plastic valves can be used.

The pressure release valves of Figs.5 and 6 are inexpensive yet reliably accurate, within the preferred accuracy ranges. The entire hyperbaric treatment device, including the valve and hoop, is inexpensive and disposable, and can be packaged in aflat pouch about

1/2 inch thick. Using a pressure release valve mat is in communication with the treatment zone and not with the gas supply eliminates the need for a separate pressure control mechanism between the hyperbaric treatment device and the oxygen source. The hyperbaric device can be connected directly to the gas cylinder or hospital gas supply line, and disconnected without losing treatment pressure.

The flexible bag sheet material can be any strong substantially gas impermeable material. Plastic sheeting material, such as polyurethane, polyethylene terephthalate, polyvinyl chloride, or ethylene/polyvinyl copolymer sheet stock, and vapor proof treated fabric such as nylon are suitable. It is highly preferably that the sheet material be transparent so that the wound can be inspected by the doctor without removing the bag from the leg..

The sealing tape is non-elastic to minimize the danger of impeding circulation. In use, it is affixed firmly around the leg of the patient, but not pulled together tightly thereby avoiding interfering with the circulation. The excess length is adhered together, again not so as to interfere with the circulation. To give a good seal for the treatment zone, the sealing tape is at least 1 1/2 inches wide and preferably from 2 to 4 inches wide. The sealing tape can be any substantially non-elastic tape such as an oriented crystalline tape or a tightly woven fabric tape. It is affixed on the inner side of the bag near the bag opening periphery extending substantially completely around the inner circumference of the upper end of the bag. The sealing tape is hermetically sealed to the bag, such as by heat bonding or use of an adhesive. The inner surface of the tape is covered with a layer of pressure sensitive adhesive, such as a hydrocolloid adhesive, that is appropriate for application to a patient's skin. It should adhere to the leg sufficiently securely so that there is substantially no gas leakage between the skin and the sealing tape, yet not so securely as to be difficult to remove from the leg. Prior to using, it is customary to cover the pressure sensitive adhesive with a paper or plastic release layer.

The devices of Figures 1-4 are normally used for static treatment of leg wounds that need hyperbaric therapeutic gas treatment, particularly with oxygen. It is known that for optimum treatment "the pressure of oxygen is regulated to be between approximately 25- 30 mm Hg. for arterial injuries, burns and pyoderma gangrenosum and preferably between 18-20 mm Hg. for venous ulcers" (U.S.Pat No. 5,478,310, Col 3, lines 65 et seq.). The treatment of a leg wound with therapeutic gas is carried out using the device of Figures 1 through 4 by inserting the wounded leg into the top end of the leg bag beyond the wound, and then securely adhering the sealing tape to the patient's leg above the wound. The excess tape length is folded back onto itself and adhered to the section of the sealing tape that is affixed to the leg. This makes a pleat in the upper portion of the leg, and creates the therapeutic treatment zone. The pressure release valve is set at the prescribed desired treatment pressure determined by diagnosis, normally slightly above the optimum treatment gas pressure. A charge of oxygen is then fed to the device though the gas inlet tube. If the device has a pressure gauge, the gas is introduced until the gas pressure gauge shows a pressure slightly above the desired treatment pressure. The pressure release valve adjusts the pressure lower until the desired maximum gas pressure level is stabilized. If there is no pressure gauge, the pressure release valve is set at the desired maximum release pressure and gas is introduced until the valve is activated, showing that the treatment zone has been charged to the desired maximum gas pressure. The gas supply then may be disconnected so that the patient has mobility. The device restricts and confines the gas, restraining it within the treatment zone and substantially maintaining pressure at the desired level for a significant period of time from the initial gas charge. Nevertheless, as the treatment continues, gas will need to be added periodically to replace leaked gas, thereby maintaining the desired maximum treatment pressure.

If a continuous gas flow treatment is prescribed, a continuous treatment hyperbaric device of the present invention can be used. It is similar to the device of Figures 1 through 4, except that it also has a gas outlet port or tube. The gas supply remains attached during the treatment, and supplies a flow of gas substantially continuously throughout treatment

The gas flows across the wound and exits out of the treatment zone through the outlet port. The rate of feed of the gas depends on the size of the outlet port, and is sufficient to substantially maintain the desired treatment pressure. More constant treatment zone gas pressure may be attainable using a continuous treatment hyperbaric device.

Although the invention herein has been described with references to particular embodiments, it is to be understood mat the embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood mat numerous modifications may be made to the embodiments and that other arrangements may be devised without departing from the spirit of the present invention as defined by the claims.

Claims

WHAT IS CLAIMED:

1. A topical hyperbaric device comprising;

(a).a flexible substantially gas impermeable flexible sheet material bag large enough to encompass at least part of a leg, said bag being capable of applying and confining gas to a therapeutic gas treatment zone;

(b). means to affix said material to make a restricted therapeutic gas treatment zone encompassing said wound, wherein said gas is in contact with said wound and is restrained from escaping from said zone;

(c) said means to affix comprising a non-stretchable sealing tape hermetically affixed to the inner periphery of the top area of said bag, said sealing tape being at least 1 1/2 inches in width and having a surface coating of pressure sensitive adhesive on the inner surface thereof which in use will be in contact around the leg and seal said bag to retain said gas in said treatment zone;

(d) means for introducing said gas into said zone; and

(e) a pressure release valve capable of setting the maximum gas pressure of said zone during treatment of a patient which valve is not in direct communication with said means for introducing said gas, automatically releases said gas from said zone when maximum pressure is exceeded, and can be pre-set at the desired maximum gas pressure in said zone.

2. The device of Claim 1 wherein said pressure release valve is fixed at a predetermined desired maximum treatment gas pressure.

3. The device of Claim 1 wherein said pressure release valve is manually adjustable to the desired maximum treatment gas pressure.

4. The device of Claim 1 wherein said pressure release valve is manually adjustable within the range of about 5-60 mm Hg.

5. The device of Claim 1 wherein said pressure release device can be set with an accuracy of 10 mm Hg.

6. The device of Claim 1 wherein said pressure release device can be set with an accuracy of 5 mm Hg..

7. The device of Claim 1 wherein said means to affix is capable of retaining said gas in said treatment zone for a prolonged period of time.

8. The device of Claim 1 comprising a pressure gauge.

9. The device of Claim 1 comprising said pressure release valve and a pressure gauge that are a single element.

10. The device of Claim 1 comprising a closed loop hoop surrounding, but not attached to said bag, positioned near the top of said bag, and having the top of said bag folded down over said hoop.

11. The device of Claim 1 wherein said sheet material is transparent.