WO2015082955A1

WO2015082955A1 - Vacuum-stiffening device for use in applying pulsating pressure therapy to a patient

Info

Publication number: WO2015082955A1
Application number: PCT/IB2013/003189
Authority: WO
Inventors: Iacob Mathiesen; Oystein Helle HUSBY; Per-johan SANDLUND; Linda Natalia TUNHEIM
Original assignee: Otivio As
Priority date: 2013-12-07
Filing date: 2013-12-07
Publication date: 2015-06-11

Abstract

A device for applying pulsating pressure to a patient can include a pressure chamber and a pressure control unit. The pressure chamber may include a variable- stiffness structural element to allow the chamber to be flexible during transport and assembly yet also be rigid during application of pulsating pressure therapy. In use, the pressure chamber can be resized and reshaped based on the anatomy of the particular patient undergoing treatment. The pressure chamber can then be transformed to a different operating state in which the variable-stiffness structural element is rigid. This may prevent the pressure chamber from substantially changing dimension, such as internal volume, while generating non-atmospheric pressures inside of the chamber.

Description

VACUUM-STIFFENING DEVICE FOR USE IN APPLYING PULSATING PRESSURE THERAPY TO A PATIENT

TECHNICAL FIELD

[0001] This disclosure relates to a device for use in applying a pulsating pressure to a region of a body of a patient and, more particularly, to a conformable device that stiffens upon application of a vacuum.

BACKGROUND

[0002] A variety of medical conditions can be treated with controlled application of pressure to a patient's body. For example, applying pulsating pressure to a patient's body can increase blood velocity in the region where the pulsating pressure is applied. This can be beneficial in providing therapeutic treatment to patients suffering from conditions such as open wounds, diabetes, ulcers, conditions caused by stroke, heart attack, or cancer, and the like. Pulsating pressure treatment can provide therapeutic benefits, for example, by increasing peripheral circulation and/or lymphatic circulation, promoting blood flow, redistribution of blood flow and diffusion, promoting healing of tissues by increased blood flow, and increasing the flow of substances between vessels and cells through increased diffusion. For patients suffering from overheating or overcooling, such as heat stroke or hypothermia, pulsating pressure therapy can be combined with external heating or cooling to help regulate a patient's temperature. For example, a patient's limb can be heated or cooled while simultaneously applying a pulsating pressure to the limb. The pulsating pressure can increase the rate at which temperature changes to the patient's limb are transferred to the patient's core, more effectively regulating the patient's core temperature than if the patient's limb was heated or cooled without pressure control.

[0003] To effectively apply pressure therapy to a patient, a controlled pressure environment typically needs to be established around the region of the patient where the pressure is to be controlled. In instances where pulsating pressure is to be applied to a patient's arm, for example, a controlled pressure environment may be established around the patient's hand and up the forearm toward the shoulder. This may involve positioning the patient's arm in a pressure chamber that pressure isolates the arm from the ambient environment. Pressure can then be adjusted within the closed environment of the pressure chamber. [0004] In applications where a pressure therapy device is intended to be used with multiple different patients, it can be difficult to provide a pressure chamber that can suitably accommodate the different sized and shaped anatomy of different patients.

Ensuring that a pressure chamber is appropriately configured for a specific patient undergoing treatment can be useful to achieve an efficacious therapeutic outcome.

SUMMARY

[0005] In general, this disclosure relates to a device for applying pressure therapy to a patient. In some examples, the device includes a pressure chamber that has a variable- volume pressure cavity. The pressure chamber may include a flexible pressure chamber structure that can at least partially and, in some examples, fully enclose a portion of a patient's body. For example, the pressure chamber may wrap around a limb of the patient to enclose the limb and define a controlled pressure environment about the limb. The pressure chamber may be formed of a flexible material so that the pressure chamber can conform to the size and shape of the specific patient undergoing treatment. For example, the pressure chamber may include a flexible gas-barrier layer that can function to pressure isolate the interior of the pressure chamber from an exterior environment. The pressure chamber may also include a variable-stiffness structure element. The variable-stiffness structural element may be sufficiently flexible such that it can be wrapped or bent to enclose at least a portion of the patient undergoing pressure treatment, thereby conforming the pressure chamber to the specific patient undergoing treatment. However, the variable-stiffness structural element may also be controllably stiffened to provide a substantially rigid structure that prevents the pressure chamber from collapsing or expanding when generating a non-atmospheric pressure inside of the pressure chamber during subsequent use.

[0006] In operation, the variable-stiffness structural element can be placed in a non-rigid (e.g., flexible) state prior to positioning a portion of a patient in the pressure chamber. In some examples, the pressure chamber includes a joint that allows the pressure chamber to fold open to provide a substantially planar pressure chamber sheet on which a patient's limb can be positioned. Regardless, the patient's limb can be positioned in the pressure chamber, and the pressure chamber can then be closed to enclose at least a portion of the patient's limb. The process of closing the pressure chamber may cause the gas barrier layer and variable-stiffness structural element to bend around the patient's limb, conforming the pressure chamber to the size and shape of the limb of the specific patient undergoing treatment.

[0007] With the patient's limb suitably inserted into the pressure chamber and the pressure chamber closed, the variable-stiffness structural element can be transformed from a non-rigid state to a substantially rigid state. Depending on the configuration of the variable-stiffness structural element, this may involve creating a vacuum inside of a gas envelop of the variable-stiffness structural element. The vacuum may interlock material inside of the gas envelop, causing the variable-stiffness structural element to become rigid without substantially changing its size or shape. When in a rigid state, the variable- stiffness structural element may provide structural support for the pressure chamber. For example, the variable-stiffness structural element may be sufficiently strong to withstand subsequent pressure changes inside of the pressure chamber without changing size and/or shape. In other words, when in a rigid state, the variable-stiffness structural element may prevent the pressure chamber from expanding and/or contracting as non-atmospheric pressures are created inside of the pressure chamber and applied to the patient.

[0008] In some configurations, the device also includes a temperature adjustment feature to add or remove thermal energy from the patient while applying pressure therapy. For example, the pressure chamber may include a temperature adjustment layer. The temperature adjustment layer may be flexible to bend or wrap about a portion of the patient as the pressure chamber is being closed. In operation, the temperature adjustment layer can emit thermal energy to heat the patient and/or withdraw thermal energy from the patient to cool the patient while non-atmospheric pressure is being applied inside of the pressure chamber. In one example, the temperature adjustment layer is configured heat a patient by emitting far infrared radiation, which can penetrate deep into the body of the patient and may also encourage blood flow. Additionally or alternatively, the temperature adjustment layer may be filled with liquid and in communication with a liquid cooler or warmer to facilitate heat transfer.

[0009] In one example, a device for applying pulsating pressure to a patient is described that includes a pressure chamber and a pressure control unit. The pressure chamber has a gas barrier layer configured to pressure isolate an interior of the pressure chamber from an exterior pressure and a variable-stiffness structural element. The variable-stiffness structural element has a stiffness that is variable upon application of a negative pressure and includes a first operating state in which the variable-stiffness structural element is flexible to conform to a shape of a body part of the patient and a second operating state in which the variable-stiffness structural element is rigid. In this example, the pressure control unit is configured to be placed in pressure communication with the interior of the pressure chamber and the variable-stiffness structural element. For example, the pressure control unit may be configured to generate a negative pressure in the variable-stiffness structural element and thereby transform the variable-stiffness structural element from the first operating state to the second operating state. The pressure control unit may be further configured to alternatingly introduce a negative pressure to the pressure chamber during a negative pressure period and release the negative pressure from the pressure chamber during a release pressure period.

[0010] In another example, a method is described that includes inserting a body part of a patient into a pressure chamber that includes a gas barrier layer configured to pressure isolate an interior of the pressure chamber from an exterior pressure and a variable- stiffness structural element. The example method also includes closing the pressure chamber by folding at least a portion of the gas barrier layer and at least a portion of the variable-stiffness structural element about at least a portion of the body part. The method further includes generating a negative pressure in an interior of the variable-stiffness structural element and thereby transforming the variable-stiffness structural element from a first operating state in which the variable-stiffness structural element is flexible to conform to a shape of the body part of the patient to a second operating state in which the variable-stiffness structural element is rigid. In addition, the method involves alternatingly introducing a negative pressure to the pressure chamber during a negative pressure period and releasing the negative pressure from the pressure chamber during a release pressure period.

[0011] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

[0012] FIG. 1 is an illustration of an example device that can be used for delivering pulsating pressure therapy to a patient. [0013] FIGS. 2A and 2B illustrate an example configuration of a variable-stiffness structural element that can be used in the example pressure chamber of FIG. 1.

[0014] FIG. 3 is an illustration of an example configuration of a pressure chamber that can be used in the device of FIG. 1 to apply pulsating pressure therapy.

DETAILED DESCRIPTION

[0015] This disclosure generally relates to a device for applying thermal and/or pressure therapy to a patient. In some examples, the device is used to apply pulsating pressure therapy to a patient. During pulsating pressure therapy, the magnitude of pressure inside the device is varied, for example over a range of non-atmospheric pressures, rather than held static at a specific non-atmospheric pressure. In some examples, the device provides a structure that can be formed around a limb so as to define a controllable pressure environment around the limb (e.g., for applying positive and/or negative pressure pulses to the limb). In operation, the structure may be used to increase blood flow to a local part of the body positioned in the structure like a defined skin surface area, an arm, a hand, a leg, and/or a foot. While the structure may be useful for many different applications, some embodiments may be particularly useful for patients with compromised blood flow and/or where it is desirable to increase blood flow to cool or heat the blood while it flows through the limb. Example medical conditions that may be treated using the device include, but are not limited to, medical conditions associated with an acquired illness, trauma or other medical conditions where heating or cooling is desired, or where increased oxygen supply to the local tissue can be beneficial. Another example application is for patients who experience intermittent claudication or critical limb ischemia (CLI), e.g., as a result of diabetes, smokers legs, or atheroschlerosis due to old age.

[0016] In different examples, the device can be used alone or in conjunction with other devices, for example, to help restore and/or improve the circulation to a site where a supply of oxygen, glucose, or other essential requirements for cells is reduced, limited or non-existing (like in the periphery of an ulcer). Such applications may also help improve the removal of carbon dioxide and other waste products in the tissue and/or may improve lymph drainage. Depending on the application, enhanced blood flow associated with use of the device may provide easier access for antibiotics and better antigen-antibody contact for the immune system. In additional examples, the device may be useful to patients with a wound on a local part of the body. Applying pulsating pressure to a local part of the body (e.g., a limb) with the wound may increase blood flow to the wounded tissue and/or tissue adjacent the wound. This may reduce the time required for the wound to heal and/or the efficacy of the healing as compared to when the portion of the body with the wound is not subject to pulsating pressure.

[0017] FIG. 1 is an illustration of an example device 10 that can be used for delivering pulsating pressure therapy to a patient. Device 10 in FIG. 1 includes a pressure chamber 12 and a pressure control unit 14. Pressure chamber 12 may be coupled to pressure control unit 14 via a tubing 16 that provides gas communication between the pressure chamber and the pressure control unit. Pressure chamber 12 is illustrated as being in an open or unfolded condition but can be folded closed to create a closed chamber. In use, a portion of a patient's body can be inserted into pressure chamber 12 and the pressure chamber then closed to at least partially and, in some examples fully, enclose the body portion. Once closed, pressure chamber 12 defines an interior chamber that is pressure isolated from an ambient pressure surrounding the pressure chamber. Pressure control unit 14 can control the pressure in the interior of pressure chamber 12 via tubing 16, thereby controlling delivery of pressure therapy via the pressure chamber.

[0018] As will be described in greater detail below, pressure chamber 12 may provide a flexible structure of adjustable size and/or shape to accommodate different sized patients and/or different sized anatomical features. For example, in contrast to being a rigid structure with a fixed volume pressure cavity, the volume of pressure chamber 12 can vary to more effectively accommodate a wide range of different sized and shaped patients. To provide adjustability, pressure chamber 12 may include a variable-stiffness structural element. The variable-stiffness structural element may have a stiffness that can be controllably varied from a flexible state in which the structural element conforms to the size and/or shape of a specific patient to a rigid state in which the structural element can be turned rigid and "locked" into the conformed size and/or shape of the specific patient. Once set, a non-atmospheric pressure can be generated within the interior of the pressure chamber defined by the rigid variable-stiffness structural element. The variable- stiffness structural element may be sufficiently rigid to prevent the pressure chamber from substantially changing in size or shape (e.g., expanding or contracting) as a pressure differential is generated between the atmospheric inside of the pressure chamber and ambient atmosphere outside of the pressure chamber.

[0019] Configuring pressure chamber 12 to conform to the size and/or shape of a specific patient undergoing pressure treatment can be useful for a variety of reasons. A pressure chamber that can conform to the size and/or shape of a specific patient can provide a smaller interior gas volume than a pressure chamber having fixed dimensions. For example, in applications where a rigid pressure chamber having fixed dimensions is provided, the pressure chamber must typically be sized for the largest patient and/or anatomical feature that will inserted into the pressure chamber during subsequent use. For the majority of patients, this will result in a pressure chamber where there is a significant amount of excess gas space within the pressure chamber. This can necessitate the use of an overly large pressure control unit 14 and/or limit the range of non- atmospheric pressures that can be generated inside of the pressure chamber, since a greater volume of gas will need to be exchanged with the pressure chamber to achieve the same pressure as a comparatively smaller chamber. Moreover, because a fixed dimension pressure chamber must typically be sized with an opening sufficient to insert the largest patient and/or anatomical feature that will be treated using the device, the pressure chamber typically has a large seal attempting to close the gap between the opening and the patient's anatomical structure. This large seal can provide a pressure failure point limiting the magnitude of non-atmospheric pressures that can be generated inside of the pressure chamber without bypassing the seal. For example, if a user attempts to generate a significant negative pressure inside of such a pressure chamber, the large seal may suck into the opening of the pressure chamber, undermining the pressure integrity of the chamber.

[0020] By configuring pressure chamber 12 with a flexible structure, the interior volume of the pressure chamber can adjust to the specific patient utilizing the chamber. This may provide a "one size fits all" style pressure chamber capable of accommodating multiple different sized patients. In some examples, this can also provide a smaller seal at the interface of pressure chamber 12 and the portion of the patient undergoing pressure treatment, providing more effective pressure isolation between the interior of the pressure chamber and the exterior of the pressure chamber as compared to if a larger seal is provided. [0021] In some applications in which pressure chamber 12 is configured as a flexible structure, device 10 can be a portable device, for example, that can be carried by one human individual from one location to another location. Rather than requiring device 10 to be used in a fixed, controlled environment such as in a medical clinic, the device in these examples can be used in the field to deliver acute, time-sensitive treatment. For example, device 10 may be used in military applications, acute medicine, disasters, or any other situation where portability and transportability are desired. Configuring pressure chamber 12 as a flexible structure may facilitate portability by allowing the structure to collapse into a portable size and/or shape, e.g., allowing the device to be fitted in a bag or a transport medium which can be carried by a soldier or a rescue person. Further, because pressure chamber 12 is not unnecessarily oversized, the size of pressure control unit 14 can be minimized, in some cases allowing the pressure control unit to operated using battery power.

[0022] Pressure chamber 12 can be fabricated from a variety of different materials that allow generation of a non-atmospheric pressure (e.g., negative pressure and/or positive pressure) while still being comfortable, light weight, and flexible. In some examples, the pressure chamber is configured to be built around a patient's body part by wrapping, folding, bending or otherwise enclosing the body part in the chamber. For example, a patient may place a limb (e.g., which may or may not first be enclosed within an inner sleeve, such as a sterile disposable liner) on a substantially flat sheet of material that is subsequently wrapped, folded, or bent about the limb to define the pressure chamber. Opposing ends of the material may then be joined (e.g., overlapped) and, in some examples, fastened with a mechanical fixation element (e.g., adhesive, snaps, zipper, hook and loop fastener, zipper, or the like). By fabricating the pressure chamber about the patient's body part, the bulkiness of the pressure chamber and the volume of the pressure chamber may be reduced as compared to rigid pressure systems with fixed volume. Smaller pressure chamber volumes (e.g., air volumes) may reduce the need for larger pumps or systems generating the non-atmospheric pressure.

[0023] In the example of FIG. 1, pressure chamber 12 includes a variable-stiffness structural element 18 and a gas barrier layer 20. Variable-stiffness structural element 18 is configured to have a stiffness that varies in response to pressure changes caused by pressure control unit 14. For example, the stiffness of variable-stiffness structural element 18 may vary as air is withdrawn from the variable-stiffness structural element and a negative pressure is created inside of the element. Gas barrier layer 20 may comprise at least one layer of material that functions to pressure isolate an interior of pressure chamber 12 from an exterior pressure (e.g., ambient pressure) surrounding the pressure chamber. For example, gas barrier layer 20 may be one or more layers of material that is substantially impermeable to air and configured (e.g., sized and/or shaped) to provide a sealed enclosure for generating non-atmospheric pressures.

[0024] FIGS. 2A and 2B illustrate an example configuration of variable-stiffness structural element 18 that can be used in pressure chamber 12 of FIG. 1. FIG. 2 A illustrates an exploded view of different constituent components of the variable-stiffness structural element. FIG. 2B illustrates the constituent components assembled. As shown, variable-stiffness structural element 18 in this example includes a gas-tight envelope 22 and a variable-stiffness core 23 positioned inside of the gas-tight envelop. Gas-tight envelope 22 is formed from a first layer 24 of air impermeable material and a second layer 26 of air impermeable material that are joined together to create an airtight pouch enclosing variable-stiffness core 23. Variable-stiffness core 23 provides a structure having a variable stiffness depending on the pressure inside of gas-tight envelope 22.

[0025] Variable-stiffness core 23 can be fabricated from a variety of different materials. Typically, variable-stiffness core 23 includes materials and/or structures that interlock together to form a rigid network as pressure inside of gas-tight envelope 22 is reduced, e.g., from atmospheric pressure to negative pressure. As air separating the materials and/or structures is removed from gas-tight envelope 22, the materials and/or structures may be brought into closer proximity, causing frictional engagement that inhibits relative movement between the materials and/or structures. In turn, this may cause variable- stiffness structural element 18 to increase in rigidity.

[0026] In one example, variable-stiffness core 23 includes multiple layers positioned in a vertically stacked arrangement between the first layer 24 of air impermeable material and the second layer 26 of air impermeable material. The multiple layers may be formed of a high friction material, such as polyethylene terephthalate (PET) coated with vinyl. As another example, variable-stiffness core 23 may include ribbons of material that form an interlocking grid as pressure is reduced inside of gas-tight envelope 22.

[0027] To facilitate pressure control inside of gas-tight envelope 22, variable-stiffness structural element 18 may include an aperture 30 that provides gas communication between an interior of the element and an external pressure source, such as pressure control unit 14 (FIG. 1). In some examples, aperture 30 includes a valve to selectively open and close gas communication between gas-tight envelope 22 and tubing 16. In operation, air can be withdrawn from gas-tight envelope 22 to transform variable-stiffness structural element 18 into a rigid element and the valve closed to hold the structural element in its rigid configuration. After holding variable-stiffness structural element 18 in its rigid state by maintaining the negative pressure inside of gas-tight envelope 22, for example while performing pressure therapy inside of the pressure chamber defined by the structural element, the valve can then be opened. Variable-stiffness structural element 18 can be restored to a flexible structure by releasing the negative pressure inside of gas-tight envelope 22 and, in some examples, returning the pressure inside of the envelope to atmospheric pressure. One example of a commercially available material that can be used as variable-stiffness structural element 18 is VARSTIFF®, developed by Tecnalia Ventures.

[0028] Independent of the specific configuration of variable-stiffness structural element 18, in general, the structural element has at least two different rigidity states or operating states: a first operating state in which the variable stiffness structural element is flexible to conform to a shape of a body part of a patient and a second operating state in which the variable-stiffness structural element is rigid. In some examples, variable-stiffness structural element 18 has a continuously variable rigidity in which the variable-stiffness structural element is flexible when a pressure in the element is at atmospheric pressure and becomes increasingly more rigid as a negative pressure inside of the element increases in magnitude.

[0029] When variable-stiffness structural element 18 is in a flexible operating state, the structural element may conform to a portion of a body of a patient undergoing treatment. For example, variable-stiffness structural element 18 may mold to a shape profile of a limb or other body portion inserted into pressure chamber 12 (FIG. 1). As pressure is reduced inside of variable-stiffness structural element 18, the structural element may become rigid while maintaining the size and/or shape profile formed while the structural element was flexible.

[0030] During operation, the pressure inside of variable-stiffness structural element 18 can be reduced down to any suitable pressure to cause the structural element to become rigid. In some applications, variable-stiffness structural element 18 exhibits a locking transition or jamming transition pressure below which the structural element is substantially rigid. In such examples, the pressure inside of variable-stiffness structural element 18 may be reduced below the locking transition pressure or jamming transition pressure before subsequently adjusting the pressure inside of the chamber created by the rigid variable-stiffness structural element. In one example, the pressure inside of gas- tight envelope 22 of variable-stiffness structural element 18 is reduced to a pressure below -40 mm Hg (-5.6 kPa), such as a pressure below -80 mm Hg (-10.7 kPa), to transform the structural element to an operating state in which the structural element is sufficiently rigid to subsequently perform pulsating pressure therapy.

[0031] When variable-stiffness structural element 18 is transformed to a rigid state, the structural element may be sufficiently rigid such that pressure chamber 12 does not substantially change size or shape (and, in other examples, does not change size or shape) when pressure control unit 14 generates pressures of varying magnitude inside of the chamber defined by the structural element. For example, variable-stiffness structural element 18 may be sufficiently right rigid such that it does not substantially change size or shape (and, in other examples, does not change size or shape) when pressure control unit 14 alternatingly introduces a negative pressure into pressure chamber 12 during a negative pressure period and releases the negative pressure during the release pressure period. On the other hand, when variable-stiffness structural element 18 is transformed to a flexible state, the structural element may be sufficiently flexible such that it can wrap, fold, or bend to at least partially (and, in other examples, fully) encircle a limb of a patient undergoing pressure treatment. For example, the variable-stiffness structural element 18 may wrap, fold, or bend from being a substantially planar sheet into a generally tubular member encircling a limb of a patient. In some such examples, the tubular member may have a circular or oval cross-sectional shape.

[0032] With further reference to FIG. 1, pressure chamber 12 also include gas barrier layer 20. Upon closing pressure chamber 12, gas barrier layer 20 may act as a barrier that prevents gas exchange between an interior of the pressure chamber in which a portion of the patient is inserted and an exterior environment surrounding the pressure chamber. This can facilitate the creation of non-atmospheric pressures inside of the pressure chamber. In some examples, such as the example illustrated in FIG. 1 , gas barrier layer 20 includes one or more layers of material that are physically separate from the variable- stiffness structural element 18. The layers of material may or may not be adhered or attached to variable-stiffness structural element 18. Typically, gas barrier layer 20 is formed of a flexible material that wraps, bends, or folds along with variable-stiffness structural element 18, when the structural element is in a flexible operating state.

Example materials that can be used to fabricate gas barrier layer 20 include, but are not limited to, neoprene and silicone rubber.

[0033] In other examples, pressure chamber 12 is designed so that at least one layer of variable-stiffness structural element 18 functions as gas barrier layer 20. For example, when configured as described with respect to FIGS. 2A and 2B, the first layer 24 of air impermeable material and/or the second layer 26 of air impermeable material that form gas-tight envelope 22 may function as gas barrier layer 20. Therefore, although variable- stiffness structural element 18 and gas barrier layer 20 are generally described as being separate elements, it should be appreciated that in practice, a single layer of material may function as both a part of variable-stiffness structural element 18 and as gas barrier layer 20.

[0034] Device 10 in FIG. 1 also includes pressure control unit 14. In the illustrated example, pressure control unit 14 is configured to control the pressure inside of variable- stiffness structural element 18 (e.g., for transforming the structural element between a flexible state and a rigid state) and also control the pressure inside of pressure chamber 12 (e.g., for delivering pulsating pressure therapy to a patient). Pressure control unit 14 may include a positive pressure pump, vacuum pump, and/or any other device capable of controlling pressure within variable-stiffness structural element 18 and/or pressure chamber 12. In some examples, pressure control unit 14 includes a processor and non- transitory computer-readable media storing instructions for execution by the processor. Pressure control unit 14 may operate under the control of the processor based on instructions received from memory and/or user input to control the operation of device 10 and/or pressure therapy delivered using the device.

[0035] In addition, although pressure control unit 14 is illustrated as a single unit controlling the pressure in both variable-stiffness structural element 18 and pressure chamber 12, in other examples, separate pressure control units may be used to separately control the pressure in the variable-stiffness structural element and the pressure chamber. For example, an operator may utilize a comparatively simple pressure control unit, such as a syringe, to evacuate variable-stiffness structural element 18 and transform the structural element from a flexible state to a rigid state. The operator may subsequently activate an electronically controlled pressure control unit to generate a series of magnitude-controlled and/or time-controlled pressure pulses within pressure chamber 12, thereby delivering pulsating pressure therapy to the patient.

[0036] Tubing 16 provides gas communication between pressure chamber 12 and pressure control unit 14. In the example of FIG. 1, tubing 16 also provides gas communication between pressure control unit 14 and an interior of variable-stiffness structural element 18. In such an example, tubing 16 may provide one lumen extending between pressure control unit 14 and an aperture or inlet of pressure chamber 12 and a separate lumen extending between the pressure control unit and variable-stiffness structural element 18. This can facilitate independent pressure adjustment of both the inside of variable-stiffness structural element 18 and inside of the pressure chamber defined by the structural element.

[0037] As briefly discussed above, device 10 can be used to provide a variety of pressure- based treatments to a patient utilizing the device. In some applications, device 10 is used to generate pulsating or varying magnitude pressures inside of pressure chamber 12. Applying pulsating pressure to a localized part of the body (e.g., a limb) inserted into pressure chamber 12 may increase blood flow to skin, muscle, and/or other tissue. The pulsating pressure may include positive pressure pulses relative to ambient pressure (e.g., outside of the pressure chamber 12), negative pressure pulses relative to ambient pressure, or combinations of positive and negative pressure. Some applications may involve application of asymmetric, predominantly negative, pulsating pressure to a part of the body inserted into pressure chamber 12. During application of negative pressure pulses, arteries, arterioles, arteriovenous anastomoses and/or capillaries in the portion of body subjected to the negative pressure pulses may dilate, thereby increasing blood flow.

Veins and venules may also dilate. In some applications, the dilatation of veins and venules may be greater on the venous side than on the arterial side due to a lesser developed (thinner) muscular vessel wall. The greater dilatation on the venous side may create an increased arterio-venous pressure gradient over the capillaries (and the arteriovenous anastomoses if they are open). This, in turn, may contribute to greater blood flow. That being said, if the veins are over-distended, a nervous spinal reflex referred to as the veno-arterial reflex may induce constriction of arterioles to prevent venous over-distention. To help avoid this, the negative pressure creating venous distention may be intermittently applied. [0038] In some examples, pressure control unit 14 of device 10 is configured to generate pressure pulses inside of pressure chamber 12 by alternatingly introducing a negative pressure to the pressure chamber during a negative pressure period and releasing the negative pressure from the pressure chamber during a release period. During the negative pressure period, pressure control unit 14 can withdraw air from inside of pressure chamber 12, generating a negative pressure relative to ambient pressure inside of the pressure chamber. During the release period, the negative pressure can be released and air allowed to flow back into pressure chamber 12, increasing the pressure inside of the pressure chamber. In some examples, a pressure inside of pressure chamber 12 is restored to approximately atmospheric pressure during the release period. In some additional examples, pressure control unit 14 pushes air into pressure chamber 12 during the release period, generating a positive pressure relative to ambient pressure inside of the pressure chamber during the release period.

[0039] When device 10 is used to apply pulsating pressures to a region of a patient contained in pressure chamber 12, any suitable duration of pressure pulses can be used. Alternately generated and released negative pressure normally comprises alternately generating negative pressure for a predetermined time interval and releasing the negative pressure for a predetermined time interval. For example, alternatingly generating and releasing negative pressure within the pressure chamber 12 may involve alternatingly generating negative pressure for a time interval of from about 1 to about 20 seconds, such as about 5 to about 15 seconds, and releasing the negative pressure for a time interval ranging from about 2 to 15 seconds, such as about 5 to about 10 seconds. The duration of the negative pressure period may be the same as or different than the duration of the release period. In one example, alternatingly generating and releasing negative pressure within the pressure chamber 12 involves generating negative pressure for a time interval of about 10 seconds and releasing the negative pressure for a time interval of about 7 seconds.

[0040] Independent of the duration of the pressure pulses, any suitable pressure can be established inside of pressure chamber 12 during each negative pressure period and each release period. In some examples, the pressure inside of pressure chamber 12 during each negative pressure is in the range of -20 mmHg to -100 mmHg, such as in the range of -40 to - 70 mmHg. The maximum pressure inside of pressure chamber 12 during each release period may be approximately atmospheric pressure or, in different examples, can be above or below atmospheric pressure. For certain applications, the pressure inside of pressure chamber 12 during each release period may be a positive pressure of corresponding but opposite magnitude as the pressure generated during the negative pressure period. Increasing the pressure inside of pressure chamber 12 during the release period may promote venous emptying.

[0041] FIG. 3 is an illustration of one example configuration of a pressure chamber 12 that can be used in device 10 of FIG. 1 to apply pulsating pressure therapy. Pressure chamber 12 in the example of FIG. 3 includes previously-described variable-stiffness structural element 18 and previously-described gas barrier layer 20. Pressure chamber 12 also includes additional optional layers, as will be described in greater detail below. In particular, pressure chamber 12 in the example of FIG. 3 is illustrated as including a temperature adjustment layer 40, an infrared-reflective layer 42, and a thermal insulating layer 44.

[0042] As described above, device 10 can be useful to cool and/or heat blood while it flows through a body part of a patient undergoing pressure therapy. Applying pulsating pressure to a patient's body can increase blood velocity in the region where the pulsating pressure is applied. When coupled with external heating or cooling, the rate at which warmed or cooled blood is transferred through the body of the patient can be increased as compared to if the region of the patient were heated or cooled without applying pulsating pressures. This can be useful for rapidly adjusting the temperature of patients suffering from overheating or overcooling, such as heat stroke or hypothermia. As another example, thermal adjustment in combination with pulsating pressure therapy can be useful to promote recovery after physical exertion. For example, the device may be used by a patient after the patient has performed physical exercise. Pulsating pressure applied by the device can help clear away metabolites and replenish energy stores. By simultaneously cooling the portion of the body of the patient undergoing pressure treatment, the patient's core temperature can be brought down after the exercise.

[0043] To provide thermal control while delivering pressure treatment, pressure chamber 12 in the example of FIG. 3 includes temperature adjustment layer 40. Temperature adjustment layer 40 is positioned inside of the variable-stiffness structural element 18 and gas barrier layer 20. This can position the layer in close proximity to a specific body part of a patient undergoing treatment, increasing the rate of thermal transfer between the patient and temperature adjustment layer. [0044] In general, temperature adjustment layer 40 can be any structure configured to heat and/or cool a body part of a patient inserted into pressure chamber 12. In some examples, temperature adjustment layer 40 includes an electrically powered heating element and/or cooling element. In such examples, pressure chamber 12 can contain an electrical connector/conductor that allows the heating and/or cooling elements of the temperature adjustment layer to function. The connector/conductor can pass through an outer shell of the pressure chamber and connect to an external power source, such as a battery (e.g., positioned inside of pressure control unit 14) or a mains power source. In operation, temperature adjustment layer 40 can emit thermal energy to heat the patient and/or withdraw thermal energy from the patient to cool the patient while non- atmospheric pressure is being applied inside of pressure chamber 12.

[0045] Temperature adjustment layer can be fabricated from a variety of different materials. In general, temperature adjustment layer 40 is constructed from a flexible material that bends, folds, or wraps about a portion of the patient as the pressure chamber is being closed. In one example, temperature adjustment layer 40 is constructed from a material configured to emit far infrared radiation in response to electrical energy applied to the material. For example, temperature adjustment layer 40 can be constructed from a polymeric material that emits far infrared radiation in response to electrical energy applied to the material. The far infrared radiation, which may be in the range from 4 microns to 25 microns, can heat the patient undergoing pressure therapy, penetrating deeper into the body of the patient than surface heating.

[0046] Unlike ordinary heat, which may be mostly absorbed at the skin level and raise the skin temperature, far infrared radiation may penetrate the skin of the patient. The natural resonant frequencies of water and organic substances within the patient may be within the range of the far infrared radiation, causing far infrared radiation rays reaching the skin to be absorbed. In turn, this can lead to more efficient heating of the patient undergoing therapy than if the surface of the patient's skin were heated using standard conductive or convective heating techniques. In addition, when infrared energy strikes the surface of a patient's tissue, it can cause surface electrons to excite and oscillate, creating heat. This increased heat can cause vasodilation, promoting improved blood circulation and increased metabolism between blood and tissue. One example of a commercially available material that can be used as a far infrared-emitting temperature adjustment layer is FabRoc® by E-X-O². [0047] While pressure chamber 12 may utilize a far infrared-emitting temperature adjustment layer such as FabRoc®, is should be appreciated that other types of heating layers, such as heating layers incorporating conductive thermal transfer elements, can be used without departing from the scope of the disclosure. For instance, in other applications, temperature adjustment layer 40 may be formed of a layer or pocket of material filled with liquid and in communication with a liquid cooler or warmer to facilitate heat transfer.

[0048] To help control the temperature set by temperature adjustment layer 40 inside of pressure chamber 12, the pressure chamber may include insulation, such as thermal insulating layer 44. Thermal insulating layer 44 can be positioned between temperature adjustment layer 40 and an external temperature environment surrounding pressure chamber 12. In the example of FIG. 3, thermal insulating layer 44 is positioned farther away from an interior of pressure chamber 12 than temperature adjustment layer 40, between the temperature adjustment layer and gas barrier layer 20. Generally, a high R- value material such as Polartec® or any other suitable thermal insulator can be used as thermal insulating layer 44. Thermal insulating layer 44 may be flexible, allowing the layer to wrap, fold, or bend as variable-stiffness structural element 18 is being wrapped, folded, or bent.

[0049] In addition to or in in lieu of thermal insulating layer 44, pressure chamber 12 may include infrared-reflective layer 42. Infrared-reflective layer 42 can reflect infrared radiation emitted by temperature adjustment layer 40 (in instances in which the temperature adjustment layer emits infrared radiation), directing the radiation away from an exterior surface of the structure and back toward the body part inserted into the pressure chamber. This can increase the thermal efficiency of pressure chamber 12 as compared to if the pressure chamber does not include infrared-reflective layer 42.

[0050] When used, infrared-reflective layer 42 can be positioned farther away from an interior of pressure chamber 12 than temperature adjustment layer 40, such as between the temperature adjustment layer and thermal insulating layer 44. Example materials that can be used as infrared-reflective layer 42 include foil (e.g., aluminum foil), metalized polymeric films, polymeric films with infrared reflecting coatings, and the like. As with thermal insulating layer 44, infrared-reflective layer 42 may be flexible, allowing the layer to wrap, fold, or bend as variable-stiffness structural element 18 is being wrapped, folded, or bent. [0051] Pressure chamber 12 may or may not include a variety of other structural elements to help improve the usability, service life, and/or therapeutic effectiveness of device 10. In the example of FIG. 3, pressure chamber 12 includes a foam layer 46 positioned between temperature adjustment layer 40 and variable-stiffness structural element 18. Foam layer 46 may function to help minimize the internal volume of pressure chamber 12 and/or may provide a biasing force that tends to bias a body portion inside of the pressure chamber toward temperature adjustment layer 40. This can help ensure good contact between the portion of the body inside of the chamber and temperature adjustment layer 40, increasing thermal transfer with the patient. When used, foam layer 46 can extend across the entire length of pressure chamber 12 or, as illustrated in FIG. 3, can be positioned in a specific region of the pressure chamber. For example, foam layer 46 may be positioned to bias against a hand, foot, or body structure but not a remainder of the limb within the pressure chamber. In other examples, pressure chamber 12 does not include foam layer 46.

[0052] To help protect pressure chamber 12 over its service life and prevent variable- stiffness structural element 18 and/or gas barrier layer 20 from being inadvertently punctured, the pressure chamber may include an external shell layer 48 formed of a puncture-resistant material. External shell layer 48 may be formed of denim, nylon, Kevlar® (aramid fiber), or any other suitable material. In addition, to help keep pressure chamber 12 clean and sanitary when using the pressure chamber to treat multiple different patients, the pressure chamber may include a disposable liner 49. In use, a patient may slip a sterile, disposable liner over the portion of their body to be inserted into pressure chamber 12 and then dispose of the liner after completing pressure treatment using the device.

[0053] Pressure chamber 12 is configured to provide an interior chamber into which a local region of a patient (e.g., a limb or portion thereof) can be inserted and non- atmospheric pressures applied. To manufacture pressure chamber 12, the constituent components forming the pressure chamber can be provided as layers or sheets of material. The layers or sheets of material can be precut or otherwise preshaped for use with a specific body part (e.g., arm, leg, foot, hand, or combination thereof). For example, the layers or sheets of material may be sized and/or shaped so an interior of the pressure chamber includes a comparatively wider or larger region and also a comparatively narrower or smaller region. The wider or larger region may be configured to accommodate a larger anatomical feature, such as a hand or foot. By contrast, the narrower or smaller region may be configured to accommodate a smaller anatomical feature, such as a wrist or ankle. Alternatively, the layers of sheets of material may provide a generic shaped pressure chamber (e.g., a cylinder) without having

comparatively larger and smaller regions. In either case, the individual constituent components forming pressure chamber 12 can be secured together, for example, using adhesive, stitching, or other fixation elements.

[0054] To facilitate insertion and removal of a body part of a patient into and out of pressure chamber 12, the pressure chamber may have a joint about which the pressure chamber opens and closes. The joint may provide ready access to an interior of the pressure chamber, which can be useful to adjust the size and/or shape of the pressure chamber to a specific patient undergoing treatment and/or quickly insert a patient limb during acute treatment. In the example of FIG. 3, pressure chamber 12 includes joint 50. Joint 50 may be a location at which opposing portions of pressure chamber 12 join together when the pressure chamber is closed and also separate apart to open the pressure chamber. For example, pressure chamber 12 may fold open from a generally tubular structure in a closed configuration to a generally planar structure in an open

configuration.

[0055] In the example illustrated in FIG. 3, joint 50 extends approximately along a center of pressure chamber 12 from a distal or terminal end 52 into which a terminal portion (e.g., hand, foot) of a patient's body part is inserted to a proximal end 54. When in use, a patient's limb or other body structure can extend out of pressure chamber 12 through an opening defined at proximal end 54. To access pressure chamber 12 in the example of FIG. 3, the pressure chamber opens along joint 50 into two approximately equally sized halves 56A, 56B. Pressure chamber 12 can fold open along joint 50 by moving halves 56A and 56B in opposing directions, e.g., until the halves are generally flat and co-planer. A portion of a patient's body can be inserted into pressure chamber 12 by placing the body part on one half 56A or 56B of the pressure chamber and/or between the two halves. The opposing halves 56A, 56B can subsequently be folded together to enclose the body part within pressure chamber 12 and conform the pressure chamber to the specific size and/or shape of the body part inserted into the chamber.

[0056] To seal joint 50 and pressure isolate the interior of the pressure chamber from an exterior environment, pressure chamber 12 can have one or more attachment features that affix opposed sides 56A, 56B of the pressure chamber together at the joint. The attachment features may function as closure members to close joint 50. Example attachment features include, but are not limited to, snaps, a zipper, hook and loop fastener elements, and the like. In the example of FIG. 3, pressure chamber 12 has hook and loop fastener elements 58 on corresponding portions of opposed sides 56A, 56B of the pressure chamber. Pressure chamber 12 also has a zipper 60 running along the length of joint 50. In operation, opposed sides 56A, 56B are folded together and the hook and loop fastener elements 58 engaged to provide an initial seal of joint 50. Zipper 60 is subsequently closed along the length of joint 50 to seal pressure chamber 50 for delivery of pressure therapy. Pressure chamber 12 can have additional or different attachment features, and it should be appreciated that the disclosure is not limited in this respect.

[0057] When a hand or foot of a patient is inserted into pressure chamber 12 for pressure therapy, the remaining portion of the patient's limb (e.g., arm or leg) may extend outside of the pressure chamber via an opening provided at proximal end 54. Ensuring that any gap between pressure chamber 12 and the patient's limb at this opening is properly sealed may help ensure that non-atmospheric pressures of adequate magnitude are generated inside of the pressure chamber during use. Because pressure chamber 12 provides a flexible structure that can conform to the size and/or shape profile of a patient undergoing treatment, any gap between a wall of the pressure chamber and the patient's limb can be minimized by reducing the size of the pressure chamber. For example, pressure chamber 12 may be wrapped, folded, or bent around the patient's limb in the region of the pressure chamber opening such that an internal wall surface of the pressure chamber is in direct contact with the surface of the patient's limb. This can help prevent air from exiting or entering pressure chamber 12 in the region of the opening.

[0058] To further seal pressure chamber 12 in the opening provided at proximal end 54, the pressure chamber may include a sealing element 62. Sealing element 62 may extend proximally from the portion of pressure chamber 12 that includes variable-stiffness structural element 18. For example, sealing element 62 may extend upwards along the length of a patient's limb toward their torso. Sealing element 62 may extend from a wall surface of pressure chamber 12 and be sized sufficiently large so as to contact the skin of the patient's limb, e.g., about its entire circumference. Sealing element 62 may close any gap that may otherwise exist between pressure chamber 12 and the patient's limb at the opening defined at proximal end 54. [0059] When used, sealing element 62 is typically formed of a flexible material that biases (e.g., presses) against the limb of the patient whose extremity is inserted into the chamber. For example, sealing element 62 may be fabricated from rubber, flexible silicone, Neoprene, or other gas-impermeable flexible materials. Sealing element 62 may be more flexible that variable-stiffness structural element 18, when the structural element is in its rigid state. This may configure pressure chamber 12 with a flexible seal about its opening that interfaces with a rigid pressure chamber structure, when variable-stiffness structural element 18 is in its rigid state.

[0060] The pressure devices and pressure chambers described herein can be used to deliver a wide variety of different pressure-based therapies. Example uses include, but are not limited to: local temperature regulation; wound healing therapy; local warming of cancer or metastasis; increased distribution of chemotherapeutic substances; temperature regulation of the whole body; increased distribution of contrast liquids; increased drainage of lymph; treatment of venous ulcers; treatment of arterial ulcers; treatment of diabetic ulcers; prevention of DVT (deep vein thrombosis); increased distribution of IV medications; increased absorption of topical medications; restoration of blood supply in trauma, and after trauma surgery; treatment of restless leg symptom; treatment of patients with reduced blood flow to extremities; and recovery treatment after exercise.

[0061] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

CLAIMS:

1. A device for applying pulsating pressure to a patient comprising:

a pressure chamber that includes a gas barrier layer configured to pressure isolate an interior of the pressure chamber from an exterior pressure and a variable-stiffness structural element, the variable-stiffness structural element having a stiffness that is variable upon application of a negative pressure and includes a first operating state in which the variable-stiffness structural element is flexible to conform to a shape of a body part of the patient and a second operating state in which the variable-stiffness structural element is rigid; and

a pressure control unit in pressure communication with the interior of the pressure chamber and the variable-stiffness structural element, wherein the pressure control unit is configured to generate the negative pressure in the variable-stiffness structural element and thereby transform the variable-stiffness structural element from the first operating state to the second operating state, and wherein the pressure control unit is configured to alternatingly introduce a negative pressure to the pressure chamber during a negative pressure period and release the negative pressure from the pressure chamber during a release pressure period.

2. The device of claim 1, wherein the pressure control unit is configured to hold the negative pressure in the variable-stiffness structural element while alternatingly introducing the negative pressure to the pressure chamber during the negative pressure period and releasing the negative pressure from the pressure chamber during the release pressure period.

3. The device of claim 1, wherein the pressure chamber includes a first aperture providing gas communication between the interior of the pressure chamber and the pressure control unit and a second aperture providing gas communication between an interior of the variable-stiffness structural element and the pressure control unit.

4. The device of claim 1, wherein the variable-stiffness structural element comprises a gas-tight envelope, a plurality of layers positioned inside the gas-tight envelope, and a valve in gas communication with an interior of the gas-tight envelop, the valve being connected to the pressure control unit and configured to evacuate the interior of the gas- tight envelop.

5. The device of claim 1, wherein the pressure control unit is further configured to release the negative pressure from the variable-stiffness structure element and thereby transform the variable-stiffness structural element from the second operating state to the first operating state.

6. The device of claim 1 , wherein the variable-stiffness structure element, when in the second operating state, is sufficiently rigid such that the pressure chamber does not substantially change size or shape when the pressure control unit alternatingly introduces the negative pressure to the pressure chamber during the negative pressure period and releases the negative pressure from the pressure chamber during the release pressure period.

7. The device of claim 6, wherein the variable-stiffness structure element, when in the second operating state, is sufficiently rigid such that the pressure chamber does not change size or shape when the pressure control unit alternatingly introduces the negative pressure to the pressure chamber during the negative pressure period and releases the negative pressure from the pressure chamber during the release pressure period.

8. The device of claim 1, wherein the variable-stiffness structure element, when in the first operating state, is sufficiently flexible such that the pressure chamber is configured to fold at least partially around the body part of the patient.

9. The device of claim 8, wherein the variable-stiffness structure element, when in the first operating state, is sufficiently flexible such that the pressure chamber is configured to fold fully around the body part of the patient.

10. The device of claim 8, wherein the body part comprises at least one of an arm and a leg.

11. The device of claim 1 , wherein the variable-stiffness structural element is positioned closer to an interior of the pressure chamber than the gas barrier layer.

12. The device of claim 1, wherein the gas barrier layer comprises at least one of neoprene and silicone.

13. The device of claim 1, wherein the pressure chamber further comprises a temperature adjustment layer configured to conform to the shape of the body part of the patient.

14. The device of claim 13, wherein the temperature adjustment layer is configured to emit far infrared radiation to heat the body part of the patient.

15. The device of claim 13, wherein the temperature adjustment layer is positioned closer to an interior of the pressure chamber than the variable-stiffness structural element.

16. The device of claim 1, wherein the pressure chamber is configured to expand open to facilitate installation of a limb of the patient in the pressure chamber.

17. The device of claim 16, wherein the pressure chamber, when closed, defines a tubular shape with a circular or oval cross-section.

18. The device of claim 1, wherein the pressure chamber includes a joint about which the pressure chamber is configured to expand open and a closure member configured to seal the joint, when the pressure chamber is closed.

19. The device of claim 18, wherein the closure member comprises at least one of hook and loop fastener elements and a zipper.

20. The device of claim 18, wherein the joint extends approximately along a center of the pressure chamber such that the pressure chamber is configured to fold into two halves when expanded open to facilitate insertion of the limb of the patient.

21. The device of claim 16, wherein the pressure chamber defines a closed end that receives a terminal portion of a limb of the patient and an opening through when the limb extends, the pressure chamber further including a sealing element extending about the opening that is configured to bias against the limb, thereby pressure isolating the interior of the pressure chamber from the exterior pressure at the opening.

22. The device of claim 21, wherein the sealing element is more flexible than the variable-stiffness structural element, when the variable-stiffness structural element is in second operating state.

23. The device of claim 1, wherein negative pressure period is between 5 seconds and 15 seconds and the release pressure period is between 2 seconds and 15 seconds.

24. The device of claim 23, wherein the negative pressure period is different than the release pressure period.

25. The device of claim 1, wherein the pressure control unit is configured to restore the pressure chamber to approximately atmospheric pressure during the release pressure period.

26. The device of claim 1 , wherein the pressure control unit is configured to generate a positive pressure in the pressure chamber during the release pressure period.

27. The device of claim 1, wherein the pressure control unit is configured to generate a negative pressure ranging from -20 mmHg to -80 mmHg (-2.7 kPa and -10.7 kPa) within the pressure chamber during the negative pressure period.

28. The device of claim 1, wherein the pressure control unit is configured to generate a negative pressure greater than -80 mmHg (-10.7 kPa) within the variable-stiffness structural element so as to transform the variable-stiffness structural element from the first operating state to the second operating state.

29. The device of claim 28, wherein the pressure control unit is configured to release the negative pressure from the variable-stiffness structural element and restore a pressure in the variable-stiffness structural element to approximately atmospheric pressure so as to transform the variable-stiffness structural element from the second operating state to the first operating state.

30. The device of claim 1, further comprising a temperature adjustment layer positioned closer to an interior of the pressure chamber than the variable-stiffness structural element, an infrared reflective layer positioned between the temperature adjustment layer and the variable-stiffness structural element, and an insulating layer positioned between the infrared reflective layer and the variable-stiffness structural element.

31. The device of claim 30, further comprising a foam layer positioned between the insulating layer and the variable-stiffness structural element and a fabric shell covering an exterior surface of the variable-stiffness structural element.

32. The device of claim 1, wherein the pressure control unit comprises a first pressure control unit in pressure communication with the interior of the pressure chamber and a second pressure control unit in pressure communication with the variable-stiffness structural element.

33. A method comprising:

inserting a body part of a patient into a pressure chamber that includes a gas barrier layer configured to pressure isolate an interior of the pressure chamber from an exterior pressure and a variable-stiffness structural element;

closing the pressure chamber by folding at least a portion of the gas barrier layer and at least a portion of the variable-stiffness structural element about at least a portion of the body part;

generating a negative pressure in an interior of the variable-stiffness structural element and thereby transforming the variable-stiffness structural element from a first operating state in which the variable-stiffness structural element is flexible to conform to a shape of the body part of the patient to a second operating state in which the variable- stiffness structural element is rigid; and

alternatingly introducing a negative pressure to the pressure chamber during a negative pressure period and releasing the negative pressure from the pressure chamber during a release pressure period.

34. The method of claim 33, wherein generating the negative pressure in the interior of the variable-stiffness structural element comprises holding the variable-stiffness structural element at the negative pressure while alternatingly introducing the negative pressure to the pressure chamber during the negative pressure period and releasing the negative pressure from the pressure chamber during the release pressure period.

35. The method of claim 33, wherein alternatingly introducing the negative pressure to the pressure chamber and releasing the negative pressure from the pressure chamber comprises drawing a vacuum and releasing the vacuum through a first aperture providing gas communication between the interior of the pressure chamber and a pressure control unit, and wherein generating the negative pressure in the interior of the variable-stiffness structural element comprises drawing a vacuum through a second aperture providing gas communication between the interior of the variable-stiffness structural element and the pressure control unit.

36. The method of claim 33, wherein the variable-stiffness structural element comprises a gas-tight envelope and a plurality of layers positioned inside the gas-tight envelope.

37. The method of claim 33, further comprising releasing the negative pressure from the interior of the variable-stiffness structural element and thereby transforming the variable-stiffness structural element from the second operating state to the first operating state.

38. The method of claim 33, wherein the variable-stiffness structure element, when in the second operating state, is sufficiently rigid such that the pressure chamber does not substantially change size or shape when the pressure control unit alternatingly introduces the negative pressure to the pressure chamber during the negative pressure period and releases the negative pressure from the pressure chamber during the release pressure period.

39. The method of claim 38, wherein the variable-stiffness structure element, when in the second operating state, is sufficiently rigid such that the pressure chamber does not change size or shape when the pressure control unit alternatingly introduces the negative pressure to the pressure chamber during the negative pressure period and releases the negative pressure from the pressure chamber during the release pressure period.

40. The method of claim 33, wherein the body part comprises at least one of an arm and a leg.

41. The method of claim 33, wherein the variable-stiffness structural element is positioned closer to an interior of the pressure chamber than the gas barrier layer.

42. The method of claim 33, wherein the gas barrier layer comprises neoprene.

43. The method of claim 33, wherein the pressure chamber further comprises a temperature adjustment layer and closing the pressure chamber further comprises folding at least a portion of the temperature adjustment layer about the portion of the body part.

44. The method of claim 43, further comprising emitting far infrared radiation via the temperature adjustment layer and thereby heating the body part of the patient.

45. The method of claim 43, wherein the temperature adjustment layer is positioned closer to an interior of the pressure chamber than the variable-stiffness structural element.

46. The method of claim 33, further comprising expanding the pressure chamber open to facilitate installation of a limb of the patient prior to inserting the limb into the pressure chamber.

47. The method of claim 46, wherein expanding the pressure chamber open comprises opening a closure member configured to seal a joint of the pressure chamber, when the pressure chamber is closed.

48. The method of claim 47, wherein the closure member comprises at least one of hook and loop fastener elements and a zipper.

49. The method of claim 46, wherein expanding the pressure chamber open comprises folding the pressure chamber open into two halves joined at their respective bases and closing the pressure chamber comprises folding the two halves together and mating the two halves together at ends opposite the respective bases.

50. The method of claim 33, wherein the pressure chamber defines a closed end that receives a terminal portion of a limb of the patient and an opening through when the limb extends, the pressure chamber further including a sealing element extending about the opening that is configured to bias against the limb, thereby pressure isolating the interior of the pressure chamber from the exterior pressure at the opening.

51. The method of claim 50, wherein the sealing element is more flexible than the variable-stiffness structural element, when the variable-stiffness structural element is in second operating state.

52. The method of claim 33, wherein negative pressure period is between 5 seconds and 15 seconds and the release pressure period is between 2 seconds and 15 seconds.

53. The method of claim 52, wherein the negative pressure period is different than the release pressure period.

54. The method of claim 33, wherein releasing the negative pressure comprises restoring the pressure chamber to approximately atmospheric pressure.

55. The method of claim 33, wherein releasing the negative pressure comprises generating a positive pressure in the pressure chamber during the release pressure period.

56. The method of claim 33, wherein introducing the negative pressure to the pressure chamber during the negative pressure period comprises generating a negative pressure ranging from -20 mmHg to -80 mmHg (-2.7 kPa and -10.7 kPa) within the pressure chamber.

57. The method of claim 33, wherein generating the negative pressure in the interior of the variable-stiffness structural element comprises generating a negative pressure greater than -80 mmHg (-10.7 kPa) within the variable-stiffness structural element.

58. The method of claim 33, further comprising releasing the negative pressure from the interior of the variable-stiffness structural element and transforming the variable- stiffness structural element from the second operating state to the first operating state.

59. The method of claim 33, wherein the pressure chamber further comprises a temperature adjustment layer positioned closer to an interior of the pressure chamber than the variable-stiffness structural element, an infrared reflective layer positioned between the temperature adjustment layer and the variable-stiffness structural element, and an insulating layer positioned between the infrared reflective layer and the variable-stiffness structural element.

60. The method of claim 59, further comprising a foam layer positioned between the insulating layer and the variable-stiffness structural element and a fabric shell covering an exterior surface of the variable-stiffness structural element.