Patent Description:
Such bandages are generally known from the state of the art. The document <CIT> describes an apparatus for removing fluids from wounds, which includes a suction component with an inlet and outlet port, and a wound cover that can connect with the suction component. This system can be used in conjunction with a specialized wound dressing, which consists of a thin sheet portion suitable for application to a wound. This wound dressing has a pressure-sensitive adhesive coating, with specific gaps which do not have adhesive, and are designed with slits to allow the wound fluid to pass through uninterrupted by adhesive material that would otherwise block these slits. The suctioning mechanism can be manually or automatically operated.

Further, <CIT> details a system and method for providing negative pressure therapy to a tissue site. The system includes a dressing assembly with an absorbent layer and a sealing layer, and a blister fluidly coupled to the absorbent layer. The blister can shift between a collapsed and an expanded position, and two check valves work to control the fluid flow during this movement. As for the method, it includes positioning the assembly at the tissue site, compressing the blister to evacuate it, and allowing the blister to expand to draw fluid from the absorbent.

Another document, <CIT>, relates to a wound dressing with an integrated mechanical aspirator for drawing exudates and fluids from the wound. The dressing combines the aspirator with an internal absorbent pad for collecting exudate and fluids. The pad includes multiple layers such as a layer of hyper-absorbent material, which acts as the fluid collection medium. The aspirator is built into the top of the dressing, featuring a hollow bulb head and a one-way purge vent that removes air when manually compressed. Upon releasing the compression, the bulb head expands back to its original shape, thereby creating a vacuum pressure that aids in drawing exudate and fluids from the wound into the pad.

Finally, <CIT> shows a device for applying dressing, medication, and suction to a skin infection. The device consists of a resilient bulb-like housing that contains an absorbent dressing and is designed with an open bottom portion. This housing is partially squeezed against the skin, causing the dressing to make contact with the infected area, while also maintaining a partial vacuum within the housing to provide suction. The device can also contain a fragile capsule of medication, which is released into the dressing when the housing is squeezed. The housing's bottom flange can be adhesively attached to the skin to hold the dressing in contact with the infected area and maintain a seal for the partial vacuum. The device can be used for continuous treatment of skin infections such as boils and carbuncles.

Generally, bandages are used to provide wound care during healing. More particularly, bandages generally provide a covering for a wound so as to shield the wound from contaminants and microbes during healing. Most bandages also provide a closure feature to help hold the edges of the wound in close apposition during healing. Bandages also frequently include gauze or the like to receive exudates emerging from the wound during healing.

Negative pressure wound therapy (NPWT) bandages apply a negative pressure to a wound during healing. This negative pressure helps reduce the likelihood of contaminants and microbes entering the wound during healing, helps draw exudates from the wound during healing, and can promote beneficial biological responses at the wound site. More particularly, NPWT bandages typically comprise (i) an absorbent dressing configured to make a fully-sealed chamber around the perimeter of a wound ("the wound chamber"), (ii) a source of negative pressure, and (iii) a conduit extending between the fully-sealed wound chamber and the source of negative pressure. As a result of this construction, the absorbent dressing can be applied to a wound so as to create a fully-sealed chamber around the perimeter of the wound, and the source of negative pressure can apply a negative pressure to the fully- sealed wound chamber, such that any contaminants and microbes present at the wound site are drawn away from the wound, exudates are drawn out of the wound, and beneficial biological responses are promoted at the wound site.

Most NPWT bandages are part of a large, complex NPWT system, in the sense that (i) the absorbent dressings are generally fairly large (e.g., they are sized to cover large open wounds), (ii) the sources of negative pressure are generally fairly large, and formed and located separate from the absorbent.

Efforts have been made to provide a small, simplified and less expensive NPWT bandage where the source of negative pressure is integrated with the absorbent dressing. By way of example but not limitation, efforts have been made to provide an NPWT bandage where a manually-operated suction pump is integrated into the absorbent dressing.

Unfortunately, current NPWT bandages integrating a suction pump with the absorbent dressing tend to suffer from a variety of deficiencies, e.g., they have a complex design, and/or are expensive, and/or are complicated to use, and/or are bulky (including having a high profile), and/or cause additional trauma to the wound during use, and/or have poor pump efficiency, and/or lack a way of indicating the level of negative pressure created, and/or lack a way of limiting the level of negative pressure created, etc. In this latter respect it should be appreciated that where too high a level of negative pressure is created, the NPWT bandage can cause trauma to the patient, e.g., blistering, capillary leakage, etc..

Thus there is a need for a new and improved NPWT bandage which is simple, inexpensive, easy-to-use, small in size (including having a low profile), is atraumatic to the wound during use, has improved pump efficiency, incorporates an automatic pressure indicator for indicating the level of negative pressure created, and provides an automatic pressure limiter for limiting the level of negative pressure created.

These and other objects of the invention are addressed by the provision and use of a new and improved NPWT bandage which is simple, inexpensive, easy-to-use, small in size (including having a low profile), is atraumatic to the wound during use, has improved pump efficiency, incorporates an automatic pressure indicator for indicating the level of negative pressure created, and provides an automatic pressure limiter for limiting the level of negative pressure created.

In one preferred form of the invention, there is provided a negative pressure wound therapy (NPWT) bandage for applying negative pressure to a wound, said NPWT bandage comprising:.

Preferably, the NPWT bandage is configured so that when the pressure differential between the pressure of the fluid within said pump chamber and atmospheric pressure is below a predetermined threshold, said pump body of said pump assembly will assume a substantially fully expanded configuration, and when said pressure differential between the pressure of the fluid within said pump chamber and atmospheric pressure is above said predetermined threshold, said pump body of said pump assembly will assume a substantially fully collapsed configuration.

Even more preferably, the NPWT bandage is configured so that said pump body abruptly changes state between said substantially fully expanded configuration and said substantially fully collapsed configuration, and between said substantially fully collapsed configuration and said substantially fully expanded configuration, as said pressure differential crosses said predetermined threshold so as to effectively constitute a substantially "binary state" device.

These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein:.

The present invention comprises the provision and use of a new and improved NPWT bandage which is simple, inexpensive, easy-to-use, small in size (including having a low profile), is atraumatic to the wound during use, has improved pump efficiency, incorporates an automatic pressure indicator for indicating the level of negative pressure created, and provides an automatic pressure limiter for limiting the level of negative pressure created.

More particularly, and looking first at <FIG>, there is shown a manually-operated negative pressure wound therapy (NPWT) bandage <NUM> having improved pump efficiency, an automatic pressure indicator for indicating the level of negative pressure created, and an automatic pressure limiter for limiting the level of negative pressure created.

NPWT bandage <NUM> generally comprises a membrane (or sheet) <NUM> and a pump assembly <NUM>.

As will hereinafter be discussed, membrane <NUM> is configured to make a fully-sealed chamber around the perimeter of a wound, whereby to define a wound chamber.

And as will hereinafter be discussed, pump assembly <NUM> is configured to apply a negative pressure to the fully-sealed wound chamber, such that any contaminants and microbes present at the wound site are drawn away from the wound, exudates are drawn out of the wound, and beneficial biological responses are promoted at the wound site. Significantly, pump assembly <NUM> is designed to provide improved pump efficiency, an automatic pressure indicator for indicating the level of negative pressure created, and an automatic pressure limiter for limiting the level of negative pressure created, as will hereinafter be discussed.

More particularly, membrane <NUM> comprises a flat planar sheet <NUM> formed out of a flexible, substantially air-impermeable material, e.g., Tegaderm from <NUM> Company (which has also been known as the Minnesota Mining and Manufacturing Company), so that it can conform to body contours and form a substantially air-tight chamber around the perimeter of a wound (i.e., the wound chamber). Membrane <NUM> is characterized by a wound-side surface <NUM> and an atmosphere-side surface <NUM>. Membrane <NUM> is also characterized by an outer perimeter <NUM> and an inner opening <NUM>.

An adhesive <NUM> is preferably disposed on wound- side surface <NUM> of membrane <NUM>. A release liner <NUM> is preferably disposed on wound-side surface <NUM> atop adhesive <NUM> so as to keep adhesive <NUM> covered until use.

A removable stiffener <NUM> is preferably disposed on atmosphere-side surface <NUM> of membrane <NUM>.

Removable stiffener <NUM> serves to facilitate manipulation of NPWT bandage <NUM> (and particularly membrane <NUM>) during removal of the NPWT bandage from its sterile packaging and during positioning of the NPWT bandage about a wound. Removable stiffener <NUM> is intended to be removed from membrane <NUM> once NPWT bandage <NUM> has been secured about the wound site.

Removable stiffener <NUM> may be provided as a single element or, more preferably, removable stiffener <NUM> is provided as a pair of elements so as to facilitate removal from membrane <NUM> after NPWT bandage <NUM> has been secured about the wound site.

Pump assembly <NUM> comprises a pump body <NUM> having a generally cylindrical shape and comprising a side wall <NUM> and an inner chamber <NUM>. Pump body <NUM> is formed out of a resilient material, e.g., silicone, such that side wall <NUM> may be compressed inwardly by the application of an external force (e.g., squeezing by the thumb and forefinger of a user) and will then attempt to return to its original uncompressed state when the external force is removed. A pump flange <NUM> is preferably formed on one side of pump body <NUM>. As will hereinafter be discussed in further detail, pump body <NUM> extends through inner opening <NUM> of membrane <NUM>, and the upper surface of pump flange <NUM> is secured to the wound-side surface <NUM> of membrane <NUM> so that pump assembly <NUM> is secured to, and carried by, membrane <NUM>. Pump flange <NUM> is preferably formed out of a flexible material so that it can conform (to at least a limited extent) to body contours. In one form of the invention, pump body <NUM> and pump flange <NUM> are formed integral with one another out of the same material, e.g., silicone. In one preferred form of the invention, side wall <NUM> of pump body <NUM> and pump flange <NUM> merge at a neck <NUM> (<FIG>). And in one preferred form of the invention, neck <NUM> has a relatively small width relative to the full diameter of pump body <NUM>, with recesses <NUM> extending inwardly between membrane <NUM> and pump body <NUM>, such that pump body <NUM> is mounted to pump flange <NUM> but is still free to radially compress/radially expand with minimal interference from pump flange <NUM>. A wound-side passageway <NUM> is formed in pump body <NUM> and communicates with inner chamber <NUM>. Wound-side passageway <NUM> opens on the exterior of pump body <NUM> at a wound-side port <NUM>. An atmosphere-side passageway <NUM> is formed in pump body <NUM> and also communicates with inner chamber <NUM>. Atmosphere-side passageway <NUM> opens on the exterior of pump body <NUM> at an atmosphere-side port <NUM>.

A wound-side one-way valve <NUM> is disposed in wound-side passageway <NUM> and is configured to permit fluid to enter inner chamber <NUM> through wound-side passageway <NUM> but to prevent fluid from exiting inner chamber <NUM> through wound-side passageway <NUM>.

An atmosphere-side one-way valve <NUM> is disposed in atmosphere-side passageway <NUM> and is configured to permit fluid to exit inner chamber <NUM> through atmosphere-side passageway <NUM> but to prevent fluid from entering inner chamber <NUM> through atmosphere-side passageway <NUM>.

As a result of this construction, when pump body <NUM> of pump assembly <NUM> is manually squeezed (e.g., by applying a compressive force to side wall <NUM> of pump body <NUM> with the thumb and forefinger of a user), fluid (e.g., air, liquid, etc.) within inner chamber <NUM> will be forced out of inner chamber <NUM> via atmosphere-side passageway <NUM>, and when pump body <NUM> of pump assembly <NUM> is thereafter released (e.g., by relaxing the compressive force applied to side wall <NUM> of pump body <NUM> by the thumb and forefinger of a user), fluid (e.g., air, liquid, etc.) below wound- side surface <NUM> of membrane <NUM> (e.g., air, liquid, etc. within the wound chamber) will be drawn into inner chamber <NUM> through wound-side passageway <NUM> as the resilient side wall of the pump body returns to its uncompressed state.

Note that when pump body <NUM> of pump assembly <NUM> is manually squeezed, fluid (e.g., air, liquid, etc.) within inner chamber <NUM> is prevented from exiting inner chamber <NUM> through wound-side passageway <NUM> due to the one-way operation of wound-side one-way valve <NUM>, and when pump body <NUM> of pump assembly <NUM> is thereafter released, air from the atmosphere is prevented from being drawn into inner chamber <NUM> through atmosphere-side passageway <NUM> due to the one way operation of atmosphere-side one-way valve <NUM>.

Thus it will be appreciated that repeatedly manually squeezing and releasing pump body <NUM> of pump assembly <NUM> will apply suction to the wound chamber disposed below wound-side surface <NUM> of membrane <NUM>, whereby to create negative pressure at the wound site.

It should be appreciated that the present invention's approach of providing a pump assembly utilizing two one-way valves disposed on either side of a deformable pump body with an in-line configuration (i.e., wound-side one-way valve <NUM> and atmosphere-side one-way valve <NUM> disposed on either side of deformable pump body <NUM>) provides a number of significant advantages which are not achievable with the prior art's approach of providing a deformable pump body utilizing a single one-way valve.

More particularly, and as will hereinafter be discussed, the present invention's approach of providing a pump assembly utilizing two one-way valves disposed on either side of a deformable pump body with an in-line configuration (i.e., wound-side one-way valve <NUM> and atmosphere-side one-way valve <NUM> disposed on either side of deformable pump body <NUM>) allows substantially the same maximum negative pressure to be established at the wound site regardless of the size of the wound chamber. This is not achievable with the prior art's approach of providing a deformable pump body utilizing a single one-way valve.

In addition, the present invention's approach of providing a pump assembly utilizing two one-way valves disposed on either side of a deformable pump body with an in-line configuration (i.e., wound-side one-way valve <NUM> and atmosphere-side one-way valve <NUM> disposed on either side of deformable pump body <NUM>) allows a greater constant selected maximum negative pressure to be achieved at the wound site than can be achieved at the wound site using a deformable pump body with a single one-way valve (which is reflective of the prior art's approach).

More particularly, <FIG>, shows, for two different size wound chambers (i.e., a <NUM> wound chamber and a <NUM> wound chamber), a maximum negative pressure that may be established with (i) a deformable pump body having two one-way valves (with one one-way valve being disposed on either side of the deformable pump body), and (ii) a deformable pump body having a single one-way valve (note: in the comparison shown in <FIG>, the volume of the pump chamber of the deformable pump body with <NUM> one-way valve is the same as the volume of the pump chamber of the deformable pump body with <NUM> one-way valves).

Inherent in <FIG> are a number of significant aspects of the present invention. First, <FIG> shows that using a deformable pump body having two one-way valves (with one one-way valve being disposed on either side of the deformable pump body) to evacuate the wound chamber lets you establish substantially the same maximum negative pressure in the wound chamber regardless of the size of the wound chamber (i.e., it yields approximately -<NUM> Hg for a <NUM> wound chamber and approximately -<NUM> Hg for a <NUM> wound chamber), whereas using a deformable pump body having a single one-way valve does not (i.e., it yields approximately -<NUM> Hg for a <NUM> wound chamber and approximately -<NUM> Hg for a <NUM> wound chamber). Thus, the NPWT bandage of the present invention allows substantially the same maximum negative pressure to be established at the wound site regardless of the size of the wound chamber, whereas prior art NPWT bandages do not.

This unique feature of the present invention is clinically significant, inasmuch as (i) it is generally desirable to establish a selected maximum negative pressure at the wound site (e.g., between about <NUM> Hg and about <NUM> Hg) , and (ii) it is generally difficult to know in advance the volume of the wound chamber (e.g., due to variations in medical applications, variations in patient anatomy, etc.). Thus, inasmuch as the NPWT bandage of the present invention allows substantially the same maximum negative pressure to be established at the wound site regardless of the size of the wound chamber, the present invention allows the NPWT bandage to be engineered in advance (e.g., at the time of manufacture) to establish a selected maximum negative pressure at the wound site, whereas prior art NPWT bandages do not.

Second, <FIG> shows that using a deformable pump body having two one-way valves (with one one-way valve being disposed on either side of the deformable pump body) to evacuate the wound chamber lets you establish a substantially higher maximum negative pressure in the wound chamber (i.e., it yields approximately - <NUM> Hg for a <NUM> wound chamber and approximately -<NUM> Hg for a <NUM> wound chamber) than can be established using a deformable pump body having a single one-way valve (i.e., it yields approximately -<NUM> Hg for a <NUM> wound chamber and approximately -<NUM> Hg for a <NUM> wound chamber). Thus, the NPWT bandage of the present invention allows a substantially higher maximum negative pressure to be established at the wound site.

Note also that the pressure within inner chamber <NUM> of pump body <NUM> is generally equal to the pressure below wound-side surface <NUM> of membrane <NUM> (i.e., the pressure within inner chamber <NUM> of pump body <NUM> is generally equal to the pressure within the wound chamber). In one preferred form of the invention, pump assembly <NUM> also comprises a removable cap <NUM>.

Removable cap <NUM> is configured to selectively close off atmosphere-side passageway <NUM> to fluid flow when removable cap <NUM> is inserted into atmosphere-side passageway <NUM> so as to close off atmosphere-side port <NUM>.

Pump assembly <NUM> is mounted to membrane <NUM> such that pump assembly <NUM> is carried by membrane <NUM>. More particularly, pump assembly <NUM> is mounted to membrane <NUM> by (i) passing pump body <NUM> of pump assembly <NUM> through inner opening <NUM> of membrane <NUM>, (ii) bringing pump flange <NUM> up against wound-side surface <NUM> of membrane <NUM>, and then (iii) adhering pump flange <NUM> to wound-side surface <NUM> of membrane <NUM> (e.g., by bonding, gluing, etc.). Note that pump assembly <NUM> and membrane <NUM> make a substantially air-tight connection.

Significantly, pump body <NUM> of pump assembly <NUM> is carefully configured to provide (i) improved pump efficiency, (ii) an automatic pressure indicator for indicating the level of negative pressure created, and (iii) an automatic pressure limiter for limiting the level of negative pressure created, as will hereinafter be discussed.

More particularly, pump body <NUM> of pump assembly <NUM> is specifically configured so that the pump body will abruptly change state between (i) a substantially fully expanded configuration where side wall <NUM> of pump body <NUM> and inner chamber <NUM> of pump body <NUM> have a substantially circular cross-section (see <FIG>) when the pressure differential between the pressure of the fluid within inner chamber <NUM> and atmospheric pressure is below a given threshold, and (ii) a substantially fully collapsed configuration where side wall <NUM> of pump body <NUM> bows inwardly (see <FIG>) when the pressure differential between the pressure of the fluid within inner chamber <NUM> and atmospheric pressure exceeds a given threshold.

Specifically, when the pressure differential between the pressure of the fluid within inner chamber <NUM> and atmospheric pressure is below a given threshold, pump body <NUM> of pump assembly <NUM> will assume its substantially fully expanded configuration (<FIG>), and when the pressure differential between the pressure of the fluid within inner chamber <NUM> and atmospheric pressure is above a given threshold, pump body <NUM> of pump assembly <NUM> will assume its substantially fully collapsed configuration (<FIG>).

Significantly, pump body <NUM> of pump assembly <NUM> is configured so that it will abruptly change state between its substantially fully expanded configuration (<FIG>) and its substantially fully collapsed configuration (<FIG>) when the pressure differential between the pressure of the fluid within inner chamber <NUM> and atmospheric pressure crosses the aforementioned given threshold. See <FIG>, which is a graph showing the relationship between the diameter of side wall <NUM> of pump body <NUM> and the pressure differential between the pressure of a fluid within inner chamber <NUM> and atmospheric pressure. Thus, pump assembly <NUM> is specifically configured to essentially behave as a substantially "binary state" device - it is either substantially fully expanded (<FIG>) or substantially fully collapsed (<FIG>). In this respect it should be appreciated that, as used herein, the term "substantially "binary state" device" is intended to refer to a device which is inclined to assume either a substantially fully expanded condition or a substantially fully collapsed condition and, as used herein, the term "substantially "binary state" behavior" is intended to refer to the inclination of a device to assume either a substantially fully expanded condition or a substantially fully collapsed condition.

Note that the substantially "binary state" behavior of pump body <NUM> is a consequence of forming the pump body with a side wall <NUM> having a substantially circular cross-section, which gives the pump body an "over-the-center" deformation characteristic, i.e., the side wall of pump body <NUM> has a "failure" mode where it abruptly transitions from its substantially fully expanded configuration to its substantially fully collapsed configuration, and has a "restoration" mode where it abruptly transitions from its substantially fully collapsed configuration to its substantially fully expanded configuration.

Note that by forming pump assembly <NUM> so that side wall <NUM> of pump body <NUM> and pump flange <NUM> merge at a neck <NUM> (<FIG>), with neck <NUM> having a relatively small width relative to the full diameter of pump body <NUM>, and with recesses <NUM> extending inwardly between membrane <NUM> and pump body <NUM>, pump body <NUM> has a substantially circular cross-section over substantially its entire circumference, with pump body <NUM> free to radially compress/radially expand with minimal interference from pump flange <NUM>, so that pump body <NUM> can exhibit substantially "binary state" behavior.

Note also that the prior art approaches of forming the pump body with dome-like or square pump configurations does not provide the pump body with an abrupt change of state - rather, these prior art dome like or square pump configurations provide the pump body with a more gradual change of state between an expanded configuration and a collapsed configuration when the pressure differential between the pressure of the fluid within an inner chamber and atmospheric pressure changes. See <FIG>, which is a graph showing the relationship between the diameter of the side wall of a pump body having a dome-like or square configuration and the pressure differential between the pressure of a fluid within an inner chamber of the pump body and atmospheric pressure.

As a result of deliberately configuring side wall <NUM> of pump body <NUM> of pump assembly <NUM> to exhibit this abrupt change of state, pump assembly <NUM> is able to provide improved pump efficiency, an automatic pressure indicator for indicating the level of negative pressure created, and an automatic pressure limiter for limiting the level of negative pressure created.

More particularly, by configuring pump body <NUM> of pump assembly <NUM> so that it will abruptly change state between its substantially fully expanded configuration and its substantially fully collapsed configuration when the pressure differential between the pressure of a fluid within inner chamber <NUM> and atmospheric pressure crosses a given threshold, pump assembly <NUM> effectively returns to its substantially fully expanded configuration as long as the pressure differential between the pressure of the fluid within inner chamber <NUM> and atmospheric pressure is below the given threshold. As a result, so long as the pressure differential between the fluid within inner chamber <NUM> and atmospheric pressure is below the given threshold, pump assembly <NUM> returns to its substantially fully expanded configuration between compressions (i.e., squeezes), and hence remains fully efficient as it applies a negative pressure to the wound chamber. This is in contrast to the performance of prior art devices where the pump body exhibits a gradual change of state between an expanded configuration and a collapsed configuration when the pressure differential between the pressure of a fluid within the inner chamber of the pump assembly changes, which makes the pump assembly progressively less efficient as it reduces the pressure within the wound chamber. This is because the pump body will progressively return less and less to its fully expanded configuration as negative pressure is created in the wound chamber, so that the pump assembly is able to evacuate less and less fluid with each squeeze of the pump body. In other words, with prior art devices, the pump assembly becomes less and less efficient as negative pressure is created in the wound chamber.

In a related manner, by configuring pump body <NUM> so that it will abruptly change state between its substantially fully expanded configuration and its substantially fully collapsed configuration when the pressure differential between the pressure of the fluid within inner chamber <NUM> and atmospheric pressure crosses a given threshold, pump assembly <NUM> is able to function as an automatic pressure indicator for indicating the level of negative pressure created, i.e., so long as pump body <NUM> of pump assembly <NUM> returns to its substantially fully expanded configuration between squeezes, it will be readily apparent to an observer that the pressure within inner chamber <NUM> (and hence the pressure within the wound chamber) will be less than a given level. This is in marked contrast to the performance of prior art devices where pump body <NUM> provides a gradual change of state between an expanded configuration and a collapsed configuration when the pressure differential between the pressure of a fluid within an inner chamber of the pump assembly changes, in which case the pump assembly is not able to function as an automatic pressure indicator for indicating the level of negative pressure created.

And also in a related manner, by configuring pump body <NUM> so that it will abruptly change state between its substantially fully expanded configuration and its substantially fully collapsed configuration when the pressure differential between the pressure of a fluid within inner chamber <NUM> and atmospheric pressure crosses a given threshold, pump assembly <NUM> is able to function as an automatic pressure limiter for limiting the level of negative pressure created since, as soon as pump body <NUM> assumes its substantially fully collapsed configuration, pump assembly <NUM> is no longer able to pump fluid from the wound chamber, essentially deactivating the pump assembly. This is in marked contrast to the performance of prior art devices where the pump body provides a gradual change of state between an expanded configuration and a collapsed configuration when the pressure differential between the pressure of a fluid within an inner chamber changes, since the pump assembly is not effectively deactivated at a given pressure differential.

It should be appreciated that the pressure differential required to transition pump body <NUM> between its substantially fully-expanded configuration and its substantially fully-collapsed configuration (i.e., the aforementioned "given threshold") may be "tuned" (i.e., tailored) to a particular level by varying one or more characteristics of pump body <NUM>, e.g., by forming side wall <NUM> of pump body <NUM> out of a material having a particular durometer, by adjusting the thickness of side wall <NUM> of pump body <NUM>, by adjusting the diameter of inner chamber <NUM> of pump body <NUM>, etc..

In general, it has been found that excellent therapeutic results may be achieved when the pressure differential required to transition pump body <NUM> between its substantially fully-expanded configuration and its substantially fully-collapsed configuration (i.e., the aforementioned "given threshold") is between about <NUM> Hg and about <NUM> Hg. In other words, it has been found that excellent therapeutic results may be achieved where pump body <NUM> transitions between its substantially fully-expanded configuration (<FIG>) and its substantially fully-collapsed
configuration (<FIG>) at a negative pressure of between about <NUM> Hg and about <NUM> Hg. It is believed that where pump body <NUM> transitions between its two states at a lower pressure (i.e., where pump body <NUM> transitions at a negative pressure lower than about <NUM> Hg) , not enough suction is provided at the wound site to effectively draw contaminants and microbes away from the wound site and/or to effectively draw exudates away from the wound site and/or to promote beneficial biological responses at the wound site. It is also believed that where pump body <NUM> transitions between its two states at a higher pressure (i.e., where pump body <NUM> transitions at a negative pressure higher than about <NUM> Hg) , the suction provided at the wound site may cause trauma to the tissue (e.g., blistering, capillary leakage, etc.).

In one preferred form of the invention, pump body <NUM> of pump assembly <NUM> is configured so that it abruptly transitions between its substantially fully expanded configuration and its substantially fully collapsed configuration when the pressure differential between the pressure of the fluid within inner chamber <NUM> and atmospheric pressure exceeds <NUM> Hg. Thus, in this form of the invention, as long as the negative pressure within the wound chamber is less than <NUM> Hg (assuming atmospheric pressure is <NUM> Hg) , pump assembly <NUM> returns to its substantially fully expanded configuration between squeezes of the pump body and maintains its pump efficiency as it applies suction to the wound chamber, and as soon as the negative pressure within the wound chamber exceeds <NUM> Hg (assuming atmospheric pressure is <NUM> Hg) , pump assembly <NUM> will assume its substantially fully collapsed configuration, acting as an automatic pressure indicator to indicate that the level of negative pressure created at the wound site has exceeded <NUM> Hg and automatically deactivating pump assembly <NUM> so that the level of negative pressure created at the wound site cannot exceed <NUM> Hg.

Note that inasmuch as pump body <NUM> of pump assembly <NUM> has a substantially cylindrical configuration, NPWT bandage <NUM> has a low profile.

Note also that inasmuch as pump body <NUM> of pump assembly <NUM> is configured to be squeezed between the thumb and forefinger of a user, the compressive force being applied to pump body <NUM> is applied parallel to the surface of the skin, so that no trauma is applied to the wound during use (i.e., during pumping of pump assembly <NUM>). This is in marked contrast to prior art NPWT bandages which employ a dome-like configuration and require the compressive force to be applied toward the wound.

Exemplary Use In one preferred form of the invention, and looking now at <FIG>, NPWT bandage <NUM> is intended to be used as follows.

First, an NPWT bandage <NUM> is removed from its box. In one form of the invention, each individual NPWT bandage <NUM> is contained in a separate sterile package, with multiple sterile packages contained in a box.

Next, an NPWT bandage <NUM> is removed from its sterile package (<FIG>) so as to be ready for use (<FIG>).

In order to apply NPWT bandage <NUM> to the wound site, release liner <NUM> is removed from wound-side surface <NUM> of membrane <NUM>. Then NPWT bandage <NUM> is positioned against the skin of a patient so that wound-side surface <NUM> of membrane <NUM> is positioned against the wound, with adhesive <NUM> securing NPWT bandage <NUM> to the skin of the patient, thereby forming a substantially air-tight seal with the skin of the patient about the perimeter of the wound chamber.

Note that when NPWT bandage <NUM> is applied to the skin of the patient, wound-side port <NUM> of wound-side passageway <NUM> of pump assembly <NUM> is open to the wound chamber.

Note also that a layer of gauze (or other absorbent wound dressing) <NUM> may be placed on the wound site prior to placing NPWT bandage <NUM> on the skin of the patient, so that the layer of gauze (or other absorbent wound dressing) is interposed between the wound and wound-side passageway <NUM> of pump assembly <NUM>. As a result, exudate emerging from the wound will be taken up by the gauze (or other absorbent wound dressing). Note that, if desired, the layer of gauze (or other absorbent wound dressing) <NUM> may be mounted to (i.e., secured to) the wound-side surface of membrane <NUM>, e.g., such as at the time of manufacture, so that the layer of gauze (or other absorbent wound dressing) <NUM> is carried to the wound site by NPWT bandage <NUM> and is applied to the wound at the same time as the NPWT bandage <NUM>.

Next, with NPWT bandage <NUM> secured to the skin of the patient, removable stiffener <NUM> is removed from atmosphere-side surface <NUM> of membrane <NUM>.

At this point, NPWT bandage <NUM> may be used to apply negative pressure to the wound chamber. This is done by squeezing side wall <NUM> of pump body <NUM> between the thumb and forefinger of a user so as to compress pump body <NUM> into its substantially fully collapsed configuration, whereby to expel fluid (e.g., air, liquid, etc.) from inner chamber <NUM> of pump body <NUM> via atmosphere-side passageway <NUM> and atmosphere-side one-way valve <NUM>. Note that fluid in inner chamber <NUM> of pump body <NUM> is prevented from exiting inner chamber <NUM> through wound-side passageway <NUM> due to the presence of wound-side one-way valve <NUM>. Then side wall <NUM> of pump body <NUM> is released, allowing the resilient pump body <NUM> to return to its substantially fully expanded configuration, thereby creating a negative pressure within inner chamber <NUM> and wound-side passageway <NUM>, such that fluid below wound-side surface <NUM> of membrane <NUM> (e.g., fluid within the wound chamber) is drawn into inner chamber <NUM> through wound-side passageway <NUM> and wound-side one-way valve <NUM>. Note that air in the atmosphere is prevented from entering inner chamber <NUM> through atmosphere-side passageway <NUM> due to the presence of atmosphere-side one-way valve <NUM>.

This process of squeezing and releasing side wall <NUM> of pump body <NUM> is repeated until pump body <NUM> of pump assembly <NUM> remains in its substantially fully collapsed configuration (i.e., side wall <NUM> of pump body <NUM> bows inwardly) even when side wall <NUM> of pump body <NUM> is not being manually compressed. When pump body <NUM> of pump assembly <NUM> remains in its substantially fully collapsed configuration even when side wall <NUM> of pump body <NUM> is not being manually compressed, an observer will know that the pressure differential between the pressure of the fluid within inner chamber <NUM> (and the wound chamber) and atmospheric pressure exceeds the desired threshold, indicating that the desired level of negative pressure has been achieved at the wound site. Note that when pump body <NUM> of pump assembly <NUM> remains in its substantially fully collapsed configuration even when side wall <NUM> of pump body <NUM> is not being manually compressed, pump assembly <NUM> will have been effectively deactivated, since it will be impossible to continue using the pump assembly with side wall <NUM> in its substantially fully collapsed configuration.

At this point removable cap <NUM> may be used to seal atmosphere-side port <NUM> of atmosphere-side passageway <NUM>.

NPWT bandage <NUM> is left in place on the wound for an appropriate period of time (e.g., a few days) so as to shield the wound from contaminants and microbes during healing, draw exudates out of the wound, and promote beneficial biological responses at the wound site. In the event that leakage should cause the negative pressure created in the wound chamber to fall below the given threshold (which will be apparent to an observer by virtue of the fact that side wall <NUM> of pump body <NUM> will return to its substantially fully- expanded configuration), atmosphere-side port <NUM> of atmosphere-passageway <NUM> may be unsealed (i.e., by removing removable cap <NUM>) and then pump assembly <NUM> may be used in the manner discussed above to re establish the desired negative pressure in the wound chamber (i.e., by repeatedly squeezing and releasing side wall <NUM> of pump body <NUM>). When appropriate, NPWT bandage <NUM> may be removed from the skin of the patient by simply peeling membrane <NUM> away from the skin of the patient.

Pump Body With Notches To Enhance The Substantially "Binary State" Behavior Of The Pump Body As noted above, pump body <NUM> of pump assembly <NUM> is preferably specifically configured so that the pump body will abruptly change state between (i) a substantially fully expanded configuration where side wall <NUM> of pump body <NUM> and inner chamber <NUM> of pump body <NUM> have a substantially circular cross-section (see <FIG>) when the pressure differential between the pressure of the fluid within inner chamber <NUM> and atmospheric pressure is below a given threshold, and (ii) a substantially fully collapsed configuration where side wall <NUM> of pump body <NUM> bows inwardly (see <FIG>) when the pressure differential between the pressure of the fluid within inner chamber <NUM> and atmospheric pressure exceeds a given threshold.

As also noted above, this substantially "binary state" behavior of pump body <NUM> is achieved by forming the pump body with a substantially circular cross- section, which gives the body an "over-the-center" deformation characteristic, i.e., so that the side wall of pump body <NUM> has a "failure" mode where it abruptly transitions from a substantially fully expanded configuration to a substantially fully collapsed configuration, and has a "restoration" mode where it abruptly transitions from a substantially fully collapsed configuration to a substantially fully expanded configuration. As noted above, by forming pump assembly <NUM> so that side wall <NUM> of pump body <NUM> and pump flange <NUM> merge at a neck <NUM> (<FIG>), with neck <NUM> having a relatively small width relative to the full diameter of pump body <NUM>, and with recesses <NUM> extending inwardly between membrane <NUM> and pump body <NUM>, pump body <NUM> has a substantially circular cross-section over substantially its entire circumference, with pump body <NUM> free to radially compress/radially expand with minimal interference from pump flange <NUM>, so that pump body <NUM> can exhibit substantially "binary state" behavior.

If desired, pump body <NUM> can be modified so as to enhance the substantially "binary state" behavior of the pump body.

By way of example but not limitation, and looking now at <FIG>, notches <NUM> can be formed in pump body <NUM> (e.g., at the "<NUM> o'clock", "<NUM> o'clock" and "<NUM> o'clock" positions) so as to enhance the substantially "binary state" behavior of the pump body by further inducing pump body <NUM> to assume only its substantially fully expanded configuration or its substantially fully collapsed configuration. Note that the more that pump body <NUM> exhibits true "binary state" behavior, the more that pump efficiency will improve and the better that pump assembly <NUM> will serve as an automatic pressure indicator and as an automatic pressure limiter.

Looking next at <FIG>, there is shown another negative pressure wound therapy (NPWT) bandage <NUM> formed in accordance with the present invention.

The NPWT bandage <NUM> shown in <FIG> is substantially the same as the NPWT bandage <NUM> shown in <FIG>, and the NPWT bandage <NUM> shown in <FIG>, except that (i) in the construction shown in <FIG>, membrane <NUM> comprises multiple layers which incorporate gauze (or other absorbent wound dressing), and (ii) in the construction shown in <FIG>, pump assembly <NUM> has a modified construction and is secured to membrane <NUM> using a different approach.

More particularly, in this form of the invention, membrane <NUM> comprises a lower skin-contacting polyurethane layer <NUM> having a center opening <NUM>, an intermediate foam (or gauze or other absorbent wound dressing) layer <NUM> for disposition over center opening <NUM> of lower skin-contacting polyurethane layer <NUM>, and an upper polyurethane layer <NUM> for disposition over intermediate foam layer <NUM> and lower skin-contacting polyurethane layer <NUM>. In the preferred form of the invention, upper polyurethane layer <NUM> is formed out of a substantially air- impermeable material. And, in the preferred form of the invention, upper polyurethane layer <NUM> and lower skin-contacting polyurethane layer <NUM> have the same size outer perimeter, so that upper polyurethane layer <NUM> does not contact the skin of the patient. The outer perimeters of upper polyurethane layer <NUM> and lower skin-contacting polyurethane layer <NUM> are secured to one another, capturing intermediate foam layer <NUM> therebetween. Intermediate foam layer <NUM> has an outer perimeter which is (i) larger than the perimeter of center opening <NUM> of lower skin contacting polyurethane layer <NUM>, and (ii) smaller than the outer perimeter of the outer perimeters of lower skin-contacting polyurethane layer <NUM> and upper polyurethane layer <NUM>. In this way, when NPWT bandage <NUM> has its center opening <NUM> of lower skin contacting polyurethane layer <NUM> positioned over a wound, fluid from the wound can pass through center opening <NUM> of lower skin-contacting polyurethane layer <NUM> to reach intermediate foam layer <NUM>. It will be appreciated that adhesive <NUM> is positioned on the wound side surface of lower skin-contacting polyurethane layer <NUM> so that a substantially air tight seal may be established by NPWT bandage <NUM> about the perimeter of a wound (i.e., so as to form the aforementioned wound chamber). An opening <NUM> is formed in upper polyurethane layer <NUM>, and overlaps center opening <NUM> of lower skin-contacting polyurethane layer <NUM>, so that wound-side passageway <NUM> of pump assembly <NUM> can access fluid (e.g., air, liquid, etc.) within the wound chamber (i.e., via opening <NUM> in upper polyurethane layer <NUM>, the openings in intermediate foam layer <NUM>, and center opening <NUM> of lower skin-contacting polyurethane layer <NUM>) for evacuation during pumping of pump assembly <NUM>.

The pump assembly <NUM> utilized in the NPWT bandage <NUM> of <FIG> is generally similar to the pump assembly <NUM> described above, except that it comprises a pair of pedestals 135A, 135B for mounting pump assembly <NUM> to membrane <NUM>. More particularly, pedestal 135A comprises one end of pump body <NUM> and is adhered (e.g., by an adhesive <NUM>) to the upper surface of membrane <NUM> (i.e., to the upper surface of upper polyurethane layer <NUM>) so that wound-side passageway <NUM> and wound-side one-way valve <NUM> are aligned with opening <NUM> in upper polyurethane layer <NUM> (and hence in fluid communication with the wound chamber). Pedestal 135B comprises the other end of pump body <NUM> and is adhered (e.g., by an adhesive <NUM>) to the upper surface of membrane <NUM> (i.e., to the upper surface of upper polyurethane layer <NUM>). The intervening portion <NUM> of pump body <NUM> sits suspended between pedestal 135A and pedestal 135B, elevated above upper polyurethane layer <NUM> of membrane <NUM>, so that a space <NUM> is formed between intervening portion <NUM> of pump body <NUM> and upper polyurethane layer <NUM> of membrane <NUM>. Inasmuch as intervening portion <NUM> of pump body <NUM> is not mounted directly to membrane <NUM>, but is instead suspended above membrane <NUM> by means of pedestals 135A and 135B, intervening portion <NUM> of pump body <NUM> can be formed with a true circular cross-section, whereby to enhance the substantially "binary state" behavior of the NPWT bandage. It will be appreciated that pump body <NUM> may incorporate one or more of the aforementioned notches <NUM> so as to further enhance the substantially "binary state" behavior of the NPWT bandage.

Claim 1:
A negative pressure wound therapy (NPWT) bandage for applying negative pressure to a wound in skin of a patient, said NPWT bandage comprising:
a membrane configured for disposition over a wound so as to form a wound chamber between said membrane and the wound, said membrane comprising a wound-side surface, an atmosphere-side surface, and an opening extending through said membrane from said wound-side surface to said atmosphere-side surface; and
a pump assembly carried by said membrane, said pump assembly comprising:
a pump body comprising a wall structure disposed about a pump chamber, wherein at least a portion of said wall structure is formed out of a resilient material such that at least a portion of said wall structure may be compressed inwardly by application of a force applied parallel to the skin of the patient;
a wound-side passageway extending through said wall structure and communicating with the wound chamber through said opening formed in said membrane;
a wound-side one-way valve disposed in said wound-side passageway, said wound-side one-way valve being configured to allow fluid to flow through said wound-side passageway from the wound chamber to said pump chamber but to prevent fluid from flowing through said wound-side passageway from said pump chamber to the wound chamber;
an atmosphere-side passageway extending through said wall structure and connecting said pump chamber and the atmosphere; and
an atmosphere-side one-way valve disposed in said atmosphere-side passageway, said atmosphere-side one-way valve being configured to allow fluid to flow through said atmosphere-side passageway from said pump chamber to the atmosphere but to prevent fluid from flowing through said atmosphere-side passageway from the atmosphere to said pump chamber;
such that when a compressive force is applied to said wall structure of said pump body in a direction parallel to the skin of the patient, said wall structure is compressed inwardly and fluid within said pump chamber will be forced out of said pump chamber via said atmosphere-side passageway, and when the compressive force applied to said wall structure of said pump body is thereafter reduced, fluid within the wound chamber will be drawn into said pump chamber through said wound-side passageway,