Manually operated negative pressure wound therapy (NPWT) dressing with improved pump efficiency, automatic pressure indicator and automatic pressure limiter

Abstract

To provide an NPWT bandage which is simple, inexpensive, easy to use, small in a size (including having a low profile), and atraumatic to a wound during use.SOLUTION: A new and improved NPWT bandage has improved pump efficiency, incorporates an automatic pressure indicator for indicating a level of a negative pressure created, and provides an automatic pressure limiter for limiting the level of the negative pressure created.SELECTED DRAWING: Figure 21

Description

[Technical field]

[0001] Applicant Cornell University Inventor Timothy Johnson Charles Sears Sean Albert David Tortoriello Orlando Soto REFERENCE TO PRIOR PENDING PATENT APPLICATIONS This application is (1) Prior pending U.S. Provisional Patent Application No. 62 / 595,398, filed December 6, 2017 by Cornell University and Timothy Johnson et al., entitled "MANUALLY-OPERATED NEGATIVE PRESSURE WOUND THERAPY (NPWT) BANDAGE WITH IMPROVED PUMP EFFICIENCY, AUTOMATIC PRESSURE INDICATOR" AND AUTOMATIC PRESSURE LIMITER" (Agent Reference Number CORN-50PROV), and (2) Prior pending U.S. Provisional Patent Application No. 62 / 611,227, filed December 28, 2017 by Cornell University and Timothy Johnson et al., entitled "MANUALLY-OPERATED NEGATIVE PRESSURE WOUND THERAPY (NPWT) BANDAGE WITH IMPROVED PUMP" EFFICIENCY, AUTOMATIC PRESSURE INDICATOR AND AUTOMATIC PRESSURE LIMITER” (proxy reference number CORN-55PROV), Claim the benefits of.

[0002] The two above-identified patent applications are hereby incorporated by reference. This application relates generally to bandages, and more particularly to negative pressure wound therapy (NPWT) bandages. [Background technology]

[0003] Bandages are used to provide care for wounds while they are healing. More specifically, bandages typically provide a covering for the wound to protect it from contaminants and microorganisms while it is healing. Most bandages also provide an occlusive function that helps to hold the edges of the wound in proximity while it is healing. Bandages also often include gauze or the like to receive exudate from the wound while it is healing.

[0004] Negative Pressure Wound Therapy (NPWT) dressings apply negative pressure to a wound during healing. This negative pressure helps reduce the likelihood of contaminants and microorganisms entering the wound during healing, helps draw exudate from the wound during healing, and can promote beneficial biological responses at the wound site. More specifically, NPWT dressings typically comprise (i) an absorbent dressing configured to create a completely sealed chamber ("wound chamber") around the periphery of the wound, (ii) a negative pressure source, and (iii) a conduit extending between the completely sealed wound chamber and the negative pressure source. As a result of this structure, the absorbent dressing can be applied to the wound to create a completely sealed chamber around the periphery of the wound, and the negative pressure source can be applied to the wound to create a completely sealed chamber around the periphery of the wound. Negative pressure can be applied to the member, which will draw any contaminants and microorganisms present at the wound site away from the wound, draw exudate from the wound, and promote beneficial biological responses at the wound site.

[0005] Most NPWT dressings are part of a large, complex NPWT system in the sense that (i) the absorbent dressing is usually fairly large (e.g., sized to cover a large open wound), (ii) the negative pressure source is usually fairly large and configured and positioned separately from the absorbent dressing (e.g., the negative pressure source usually includes a powered suction pump or vacuum canister), and (iii) the NPWT system usually requires significant training to use. These NPWT systems also tend to be fairly expensive.

[0006] Efforts have been made to provide smaller, simplified, and less expensive NPWT dressings in which a negative pressure source is integrated into the absorbent dressing. By way of example and not limitation, efforts have been made to provide NPWT dressings in which a manually operated suction pump is integrated into the absorbent dressing.

[0007] Unfortunately, current NPWT bandages that integrate a suction pump with an absorbent dressing tend to suffer from a wide variety of shortcomings, such as having a complex design, and / or being expensive, and / or being complicated to use, and / or being bulky (including having a high profile), and / or causing additional trauma to the wound during use, and / or having poor pump efficiency, and / or lacking a way to indicate the level of negative pressure generated, and / or lacking a way to limit the level of negative pressure generated, etc. With regard to this latter, it should be appreciated that NPWT bandages may cause trauma to the patient, e.g., blister formation, capillary leakage, etc., if an excessively high level of negative pressure is generated.

[0008] Thus, there is a need for new and improved NPWT dressings that are simple, inexpensive, easy to use, small in size (including having a low profile), do not traumatize the wound during use, have improved pump efficiency, incorporate an automatic pressure indicator to indicate the level of negative pressure generated, and provide an automatic pressure limiter to limit the level of negative pressure generated. Summary of the Invention [Problem to be solved by the invention]

[0009] These and other objects of the present invention are addressed by the provision and use of a new and improved NPWT dressing that is simple, inexpensive, easy to use, small in size (including having a low profile), does not traumatize the wound during use, has improved pump efficiency, incorporates an automatic pressure indicator to indicate the level of negative pressure generated, and provides an automatic pressure limiter to limit the level of negative pressure generated. [Means for solving the problem]

[0010] In one preferred form of the invention, there is provided a Negative Pressure Wound Therapy (NPWT) dressing for applying negative pressure to a wound, said NPWT dressing comprising: a membrane configured for placement over a wound to form a wound chamber between the membrane and the wound, the membrane including a wound-side surface, an atmosphere-side surface, and an opening extending through the membrane from the wound-side surface to the atmosphere-side surface; A pump assembly carried by the membrane, the pump assembly comprising: a pump body including a wall structure disposed about a pump chamber, at least a portion of the wall structure being elastic; a wound side passageway extending through the wall structure and communicating with the wound chamber through the opening formed in the membrane; a wound side one-way valve disposed within the wound side passageway, the wound side one-way valve a wound side one-way valve configured to allow fluid flow from the wound chamber to the pump chamber through the wound side passage but to prevent fluid flow from the pump chamber to the wound chamber through the wound side passage; an atmosphere-side passageway extending through the wall structure connecting the pump chamber and the atmosphere; an atmosphere-side one-way valve disposed in the atmosphere-side passageway, the atmosphere-side one-way valve configured to allow fluid to flow from the pump chamber to atmosphere through the atmosphere-side passageway but to prevent fluid from flowing from atmosphere to the pump chamber through the atmosphere-side passageway; a pump assembly comprising: Equipped with An NPWT dressing is provided where, when a compressive force is applied to the wall structure of the pump body, fluid in the pump chamber is forced out of the pump chamber via the atmosphere side passageway, and when the compressive force applied to the wall structure of the pump body is subsequently reduced, fluid in the wound chamber is drawn into the pump chamber through the wound side passageway.

[0011] Preferably, the NPWT dressing is configured such that the pump body of the pump assembly assumes a substantially fully deployed configuration when a pressure differential between fluid pressure in the pump chamber and atmospheric pressure is below a predetermined threshold, and such that the pump body of the pump assembly assumes a substantially fully collapsed configuration when the pressure differential between fluid pressure in the pump chamber and atmospheric pressure is above the predetermined threshold.

[0012] Even more preferably, the NPWT bandage is configured such that the pump body abruptly changes state between the substantially fully deployed configuration and the substantially fully collapsed configuration, and between the substantially fully collapsed configuration and the substantially fully deployed configuration, when the pressure differential crosses the predetermined threshold, effectively creating a substantially "binary state" device.

[0013] In another preferred form of the invention there is provided a method for applying negative pressure to a wound comprising the steps of: Preparing a negative pressure wound therapy (NPWT) dressing, the NPWT dressing comprising: a membrane configured for placement over a wound to form a wound chamber between the membrane and the wound, the membrane including a wound-side surface, an atmosphere-side surface, and an opening extending through the membrane from the wound-side surface to the atmosphere-side surface; A pump assembly carried by the membrane, the pump assembly comprising: a pump body including a wall structure disposed about a pump chamber, at least a portion of the wall structure being elastic; a wound side passageway extending through the wall structure and communicating with the wound chamber through the opening formed in the membrane; a wound side one-way valve disposed in the wound side passageway, the wound side one-way valve configured to allow fluid flow from the wound chamber to the pump chamber through the wound side passageway but to prevent fluid flow from the pump chamber to the wound chamber through the wound side passageway; an atmosphere-side passageway extending through the wall structure connecting the pump chamber and the atmosphere; an atmosphere-side one-way valve disposed in the atmosphere-side passageway, the atmosphere-side one-way valve configured to allow fluid to flow from the pump chamber to atmosphere through the atmosphere-side passageway but to prevent fluid from flowing from atmosphere to the pump chamber through the atmosphere-side passageway; a pump assembly comprising: Equipped with when a compressive force is applied to the wall structure of the pump body, fluid in the pump chamber is forced out of the pump chamber via the atmosphere side passageway, and when the compressive force applied to the wall structure of the pump body is subsequently reduced, fluid in the wound chamber is drawn into the pump chamber through the wound side passageway; positioning the negative pressure wound therapy (NPWT) dressing over a wound so as to form a wound chamber between the membrane and the wound; applying a compressive force to a wall structure of the pump body, and thereafter reducing the compressive force applied to the wall structure of the pump body such that a negative pressure is applied to the wound; A method is provided, comprising:

[0014] In another preferred form of the invention, there is provided a Negative Pressure Wound Therapy (NPWT) dressing for applying negative pressure to a wound, said NPWT dressing comprising: a membrane configured for placement over a wound to form a wound chamber between the membrane and the wound, the membrane including a wound-side surface, an atmosphere-side surface, and an opening extending through the membrane from the wound-side surface to the atmosphere-side surface; a pump carried by the membrane, the pump comprising a wall chamber disposed about a pump chamber, at least a portion of the wall chamber being elastic, the pump chamber communicating with the wound chamber through the opening formed in the membrane; An NPWT dressing is provided in which no portion of the pump chamber is defined by the wound.

[0015] In another preferred form of the invention, there is provided a Negative Pressure Wound Therapy (NPWT) dressing for applying negative pressure to a wound, said NPWT dressing comprising: a membrane configured for placement over a wound to form a wound chamber between the membrane and the wound, the membrane including a wound-side surface, an atmosphere-side surface, and an opening extending through the membrane from the wound-side surface to the atmosphere-side surface; a pump carried by the membrane, the pump comprising a wall chamber disposed about a pump chamber, at least a portion of the wall chamber being elastic, the pump chamber communicating with the wound chamber through the opening formed in the membrane; A NPWT dressing is provided in which the pump does not apply positive pressure to the wound.

[0016] In another preferred form of the invention, there is provided a Negative Pressure Wound Therapy (NPWT) dressing for applying negative pressure to a wound, said NPWT dressing comprising: a membrane configured for placement over a wound to form a wound chamber between the membrane and the wound, the membrane including a wound-side surface, an atmosphere-side surface, and an opening extending through the membrane from the wound-side surface to the atmosphere-side surface; a pump carried by the membrane, the pump comprising a wall chamber disposed about a pump chamber, at least a portion of the wall chamber being elastic, the pump chamber communicating with the wound chamber through the opening formed in the membrane; An NPWT dressing is provided in which the pump is connected to the wound chamber such that a reduction in the volume of the pump chamber does not result in a change in pressure in the wound chamber.

[0017] These and other objects and features of the present invention will be more fully disclosed or made apparent by the following detailed description of preferred embodiments of the invention, which should be considered in conjunction with the accompanying drawings in which like numerals refer to like parts and in which: [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram illustrating a new and improved NPWT dressing formed in accordance with the present invention. [Diagram 2] FIG. 1 is an exploded schematic diagram showing a new and improved NPWT dressing formed in accordance with the present invention. [Diagram 3] FIG. 1 is an exploded schematic diagram showing a new and improved NPWT dressing formed in accordance with the present invention. [Figure 4] FIG. 1 is a schematic diagram illustrating a new and improved NPWT dressing formed in accordance with the present invention. [Figure 4A] FIG. 4B is a schematic diagram illustrating the maximum negative pressure that can be established for two different sizes of wound chambers (i.e., 7.5 mL wound chamber and 15 mL wound chamber) using (i) a deformable pump body with two one-way valves (one one-way valve located on each side of the deformable pump body) and (ii) a deformable pump body with a single one-way valve (Note: in the comparison shown in FIG. 4A, the volume of the pump chamber of the deformable pump body with one one-way valve is the same as the volume of the pump chamber of the deformable pump body with two one-way valves). [Diagram 5]FIG. 5 is a schematic diagram illustrating a pump body of the pump assembly of the NPWT dressing shown in FIGS. 1-4 in a substantially fully deployed configuration. [Figure 6] FIG. 5 is a schematic diagram illustrating a pump body of the pump assembly of the NPWT dressing shown in FIGS. 1-4 in a substantially fully collapsed configuration. [Figure 7] FIG. 5 is a schematic diagram illustrating how the pump body of the pump assembly of the NPWT bandage shown in FIGS. 1-4 abruptly changes state between its substantially fully deployed configuration and its substantially fully folded configuration. [Figure 8] 1 is a schematic diagram illustrating how a pump body of a pump assembly of a prior art NPWT bandage gradually changes state between its substantially fully deployed configuration and its substantially fully collapsed configuration. [Figure 9] 11A-11C are schematic diagrams illustrating an exemplary use of the new and improved NPWT dressing shown in FIGS. 1-4 (note that in FIGS. 11 and 14-16, the removable cap 100 (see below) has been removed from the drawings for clarity of illustration). [Figure 10] 11A-11C are schematic diagrams illustrating an exemplary use of the new and improved NPWT dressing shown in FIGS. 1-4 (note that in FIGS. 11 and 14-16, the removable cap 100 (see below) has been removed from the drawings for clarity of illustration). [Figure 11] 11A-11C are schematic diagrams illustrating an exemplary use of the new and improved NPWT dressing shown in FIGS. 1-4 (note that in FIGS. 11 and 14-16, the removable cap 100 (see below) has been removed from the drawings for clarity of illustration). [Figure 12] 11A-11C are schematic diagrams illustrating an exemplary use of the new and improved NPWT dressing shown in FIGS. 1-4 (note that in FIGS. 11 and 14-16, the removable cap 100 (see below) has been removed from the drawings for clarity of illustration). [Figure 13]11A-11C are schematic diagrams illustrating an exemplary use of the new and improved NPWT dressing shown in FIGS. 1-4 (note that in FIGS. 11 and 14-16, the removable cap 100 (see below) has been removed from the drawings for clarity of illustration). [Figure 14] 11A-11C are schematic diagrams illustrating an exemplary use of the new and improved NPWT dressing shown in FIGS. 1-4 (note that in FIGS. 11 and 14-16, the removable cap 100 (see below) has been removed from the drawings for clarity of illustration). [Figure 15] 11A-11C are schematic diagrams illustrating an exemplary use of the new and improved NPWT dressing shown in FIGS. 1-4 (note that in FIGS. 11 and 14-16, the removable cap 100 (see below) has been removed from the drawings for clarity of illustration). [Figure 16] 11A-11C are schematic diagrams illustrating an exemplary use of the new and improved NPWT dressing shown in FIGS. 1-4 (note that in FIGS. 11 and 14-16, the removable cap 100 (see below) has been removed from the drawings for clarity of illustration). [Figure 17] FIG. 1 is a schematic diagram illustrating another new and improved NPWT dressing formed in accordance with the present invention. [Figure 18] FIG. 1 is a schematic diagram illustrating another new and improved NPWT dressing formed in accordance with the present invention. [Figure 19] FIG. 1 is a schematic diagram illustrating another new and improved NPWT dressing formed in accordance with the present invention. [Figure 20] FIG. 1 is a schematic diagram illustrating another new and improved NPWT dressing formed in accordance with the present invention. [Figure 21] FIG. 1 is a schematic diagram illustrating another new and improved NPWT dressing formed in accordance with the present invention. [Figure 22] FIG. 1 is a schematic diagram illustrating another new and improved NPWT dressing formed in accordance with the present invention. [Diagram 23] FIG. 1 is a schematic diagram illustrating another new and improved NPWT dressing formed in accordance with the present invention. [Figure 24]FIG. 1 is a schematic diagram illustrating another new and improved NPWT dressing formed in accordance with the present invention. [Diagram 25] FIG. 1 is a schematic diagram illustrating another new and improved NPWT dressing formed in accordance with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present invention involves the provision and use of a new and improved NPWT dressing that is simple, inexpensive, easy to use, small in size (including having a low profile), does not traumatize the wound during use, has improved pump efficiency, incorporates an automatic pressure indicator to indicate the level of negative pressure generated, and provides an automatic pressure limiter to limit the level of negative pressure generated. A typical manually operated negative pressure wound therapy (NPWT) dressing More specifically, and referring first to Figures 1-4, a manually operated Negative Pressure Wound Therapy (NPWT) bandage 5 is shown having improved pump efficiency, an automatic pressure indicator for indicating the level of negative pressure generated, and an automatic pressure limiter for limiting the level of negative pressure generated.

[0020] The NPWT dressing 5 generally comprises a membrane (or sheet) 10 and a pump assembly 15 . As will be discussed later, the membrane 10 is configured to create a completely sealed chamber around the periphery of the wound, thereby defining a wound chamber.

[0021] And as will be discussed below, the pump assembly 15 applies negative pressure to the completely sealed wound chamber, thereby drawing any contaminants and microorganisms present at the wound site away from the wound, drawing exudate from the wound, and promoting beneficial biological responses at the wound site. Importantly, as will be discussed below, the pump assembly 15 is designed to provide improved pump efficiency, an automatic pressure indicator to indicate the level of negative pressure generated, and an automatic pressure limiter to limit the level of negative pressure generated. film More specifically, membrane 10 includes a flat, planar sheet 20 formed from a flexible, substantially air impermeable material, such as Tegaderm from 3M Company (also known as Minnesota Mining and Manufacturing Company), which enables membrane 10 to conform to the contours of the body and form a substantially airtight chamber (i.e., wound chamber) around the periphery of the wound. Membrane 10 is characterized by a wound-facing surface 25 and an air-facing surface 30. Membrane 10 is It is also characterized by an outer edge 35 and an inner opening 40 .

[0022] Adhesive 45 is preferably disposed on wound-side surface 25 of membrane 10. A release liner 50 is preferably disposed on wound-side surface 25 over adhesive 45 to keep adhesive 45 covered until use.

[0023] The removable stiffener 55 is preferably disposed on the air-facing surface 30 of the membrane 10. The removable stiffener 55 serves to facilitate manipulation of the NPWT dressing 5 (and particularly the membrane 10) during removal of the NPWT dressing from its sterile packaging and during positioning of the NPWT dressing about a wound. The removable stiffener 55 is intended to be removed from the membrane 10 once the NPWT dressing 5 has been secured about the wound site. The removable stiffener 55 can be provided as a single element, and more preferably, the removable stiffener 55 is provided as a pair of elements to facilitate removal from the membrane 10 after the NPWT dressing 5 has been secured about the wound site. Pump Assembly The pump assembly 15 comprises a pump body 60 having a generally cylindrical shape and comprising a sidewall 65 and an inner chamber 70. The pump body 60 is formed from a resilient material, e.g., silicone, whereby the sidewall 65 can be compressed inwardly by application of an external force (e.g., squeezing by the user's thumb and index finger) and then tends to return to its original, uncompressed state when the external force is removed. A pump flange 75 is preferably formed on one side of the pump body 60. As will be discussed in more detail below, the pump body 60 extends through the inner opening 40 of the membrane 10, and an upper surface of the pump flange 75 is secured to the wound-side surface 25 of the membrane 10, whereby the pump assembly 15 is secured to and carried by the membrane 10. The pump flange 75 is preferably formed from a flexible material, whereby it can conform (at least to a limited extent) to the contours of the body. In one form of the invention, the pump body 60 and the pump flange 75 are integrally formed with one another from the same material, e.g., silicone. In one preferred form of the invention, the side wall 65 of the pump body 60 and the pump flange 75 meet at a neck 77 (FIG. 5). And, in one preferred form of the invention, the neck 77 has a relatively small width relative to the overall diameter of the pump body 60, and a recess 78 extends inwardly between the membrane 10 and the pump body 60, such that the pump body 60 is mounted to the pump flange 75 but is still free to radially compress / expand with minimal interference from the pump flange 75. A wound side passageway 80 is formed in the pump body 60 and communicates with the inner chamber 70. The wound side passageway 80 opens to the outside of the pump body 60 at a wound side port 82. An atmosphere side passageway 85 is formed in the pump body 60 and also communicates with the inner chamber 70. The atmosphere side passageway 85 opens to the outside of the pump body 60 at an atmosphere side port 87.

[0024] The wound side one-way valve 90 is disposed within the wound side passage 80 and is configured to allow fluid to enter the inner chamber 70 through the wound side passage 80 but to prevent fluid from exiting the inner chamber 70 through the wound side passage 80.

[0025] The atmospheric side one-way valve 95 is disposed in the atmospheric side passage 85 and is configured to allow fluid to exit the inner chamber 70 through the atmospheric side passage 85 but to prevent fluid from entering the inner chamber 70 through the atmospheric side passage 85.

[0026] As a result of this construction, when pump body 60 of pump assembly 15 is manually squeezed (e.g., by applying a compressive force to side wall 65 of pump body 60 with a user's thumb and index finger), fluid (e.g., air, liquid, etc.) within inner chamber 70 is forced out of inner chamber 70 via atmosphere-side passageway 85, and then pump body 60 of pump assembly 15 is manually squeezed (e.g., by applying a compressive force to side wall 65 of pump body 60 with a user's thumb and index finger). When released (by relieving the compressive force applied to membrane 10, 5), fluid (e.g., air, liquid, etc.) beneath wound side surface 25 of membrane 10 (e.g., air, liquid, etc. in the wound chamber) is drawn through wound side passageway 85 and into inner chamber 70 as the elastic side walls of the pump body return to their unstressed state.

[0027] It should be noted that when the pump body 60 of the pump assembly 15 is manually squeezed, fluid (e.g., air, liquid, etc.) in the inner chamber 70 is prevented from exiting the inner chamber 70 through the wound side passage 80 due to the one-way operation of the wound side one-way valve 90, and when the pump body 60 of the pump assembly 15 is subsequently released, air from the atmosphere is prevented from being drawn into the inner chamber 70 through the atmosphere side passage 85 due to the one-way operation of the atmosphere side one-way valve 95.

[0028] Thus, it will be appreciated that by repeatedly manually squeezing and releasing the pump body 60 of the pump assembly 15, suction is applied to the wound chamber located beneath the wound side surface 25 of the membrane 10, thereby generating negative pressure at the wound site.

[0029] It should be appreciated that the present invention's approach of preparing a pump assembly utilizing two one-way valves arranged in an in-line configuration on either side of the deformable pump body (i.e., a wound side one-way valve 90 and an atmosphere side one-way valve 95 arranged on either side of the deformable pump body 60) provides several significant advantages not achievable with the prior art approach of preparing a deformable pump body utilizing a single one-way valve.

[0030] More specifically, as discussed below, the present approach of preparing a pump assembly utilizing two one-way valves arranged in an in-line configuration on either side of the deformable pump body (i.e., a wound side one-way valve 90 and an atmosphere side one-way valve 95 arranged on either side of the deformable pump body 60) allows substantially the same maximum negative pressure to be established at the wound site regardless of the size of the wound chamber, which is not achievable with the prior art approach of preparing a deformable pump body utilizing a single one-way valve.

[0031] Additionally, the present approach of preparing a pump assembly utilizing two one-way valves arranged in an in-line configuration on either side of the deformable pump body (i.e., a wound-side one-way valve 90 and an atmosphere-side one-way valve 95 arranged on either side of the deformable pump body 60) allows a constant selected maximum negative pressure to be achieved at the wound site that is greater than would be achievable at the wound site using a deformable pump body having a single one-way valve (reflecting the prior art approach).

[0032] More specifically, FIG. 4A shows the maximum negative pressure that can be established for two different sizes of wound chambers (i.e., a 7.5 mL wound chamber and a 15 mL wound chamber) using (i) a deformable pump body having two one-way valves (one one-way valve located on each 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. 4A, the volume of the pump chamber of the deformable pump body having one one-way valve is the same as the volume of the pump chamber of the deformable pump body having two one-way valves).

[0033] FIG. 4A illustrates several important aspects of the present invention. First, FIG. 4A illustrates that by evacuating the wound chamber using a deformable pump body having two one-way valves (one one-way valve located on each side of the deformable pump body), substantially the same maximum negative pressure can be created in the wound chamber regardless of the size of the wound chamber (i.e., approximately −20.00 kPa (−150.0 mmHg) for a 7.5 mL wound chamber and approximately −20.00 kPa (−150.0 mmHg) for a 15 mL wound chamber). ) is established at the wound site, whereas a deformable pump body having a single one-way valve would not (i.e., approximately -10.67 kPa (-80.0 mmHg) is obtained for a 7.5 mL wound chamber and approximately -6.67 kPa (-50.0 mmHg) is obtained for a 15 mL wound chamber). Thus, the NPWT dressing 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 the prior art NPWT dressings do not allow this.

[0034] This unique feature of the present invention is clinically important because (i) it is typically desirable to establish a selected maximum negative pressure (e.g., between about 8.00 kPa (60 mmHg) and about 24.00 kPa (180 mmHg)) at a wound site, and (ii) it is typically difficult to know in advance the volume of the wound chamber (e.g., due to variations in medical applications and variations in patient anatomy, etc.). Thus, the present invention allows for NPWT bandages to be designed in advance (e.g., at the time of manufacture) to establish a selected maximum negative pressure at a wound site, whereas prior art NPWT bandages do not, because the NPWT bandages of the present invention allow for substantially the same maximum negative pressure to be established at the wound site regardless of the size of the wound chamber.

[0035] Second, Figure 4A shows that by evacuating the wound chamber using a deformable pump body having two one-way valves (one one-way valve disposed on each side of the deformable pump body), a substantially higher maximum negative pressure is established in the wound chamber (i.e., about -20.00 kPa (-150 mmHg) for a 7.5 mL wound chamber and about -20.00 kPa (-150 mmHg) for a 15 mL wound chamber) than can be established using a deformable pump body having a single one-way valve (i.e., about -10.67 kPa (-80.0 mmHg) for a 7.5 mL wound chamber and about -6.67 kPa (-50.0 mmHg) for a 15 mL wound chamber). Thus, the NPWT dressing of the present invention allows a substantially higher maximum negative pressure to be established at the wound site.

[0036] It should also be noted that the pressure within the inner chamber 70 of the pump body 60 is typically equal to the pressure beneath the wound side surface 25 of the membrane 10 (i.e., the pressure within the inner chamber 70 of the pump body 60 is typically equal to the pressure within the wound chamber).

[0037] In one preferred form of the invention, pump assembly 15 also includes a removable cap 100. Removable cap 100 is configured to selectively close atmosphere-side passageway 85 to fluid flow when removable cap 100 is inserted into atmosphere-side passageway 85 such that removable cap 100 closes atmosphere-side port 87.

[0038] The pump assembly 15 is attached to the membrane 10 such that the pump assembly 15 is carried by the membrane 10. More specifically, the pump assembly 15 is attached to the membrane 10 by (i) passing the pump body 60 of the pump assembly 15 through the inner opening 40 of the membrane 10, (ii) bringing the pump flange 75 facing the wound-side surface 25 of the membrane 10, and then (iii) attaching (e.g., by adhering, gluing, etc.) the pump flange 75 to the wound-side surface 25 of the membrane 10. It should be noted that the pump assembly 15 and the membrane 10 form a substantially airtight connection.

[0039] Importantly, the pump body 60 of the pump assembly 15 is carefully constructed to provide (i) improved pump efficiency, (ii) an automatic pressure indicator that indicates the level of negative pressure generated, and (iii) an automatic pressure limiter for limiting the level of negative pressure generated, as discussed below.

[0040] More specifically, the pump body 60 of the pump assembly 15 abruptly changes state between (i) a substantially fully deployed configuration in which the side walls 65 of the pump body 60 and the inner chamber 70 of the pump body 60 have a substantially circular cross-section (see FIG. 5 ) when the pressure difference between the pressure of the fluid in the inner chamber 70 and atmospheric pressure is below a given threshold, and (ii) a substantially fully deployed configuration in which the side walls 65 of the pump body 60 are deflected inwardly (see FIG. 6 ) when the pressure difference between the pressure of the fluid in the inner chamber 70 and atmospheric pressure exceeds a given threshold.

[0041] In particular, when the pressure difference between the pressure of the fluid in the inner chamber 70 and atmospheric pressure is below a given threshold, the pump body 60 of the pump assembly 15 assumes a substantially fully deployed configuration (FIG. 5), and when the pressure difference between the pressure of the fluid in the inner chamber 70 and atmospheric pressure is above a given threshold, the pump body 60 of the pump assembly 15 assumes a substantially fully folded configuration (FIG. 6).

[0042] Importantly, the pump body 60 of the pump assembly 15 is configured to abruptly change state between a substantially fully deployed configuration (FIG. 5) and a substantially fully folded configuration (FIG. 6) when the pressure difference between the pressure of the fluid in the inner chamber 70 and atmospheric pressure crosses a given threshold value as described above. See FIG. 7, which is a graph showing the relationship between the diameter of the sidewall 65 of the pump body 60 and the pressure difference between the pressure of the fluid in the inner chamber 70 and atmospheric pressure. Thus, the pump assembly 15 is specifically configured to essentially behave as a substantially "binary state" device, i.e., substantially fully deployed (FIG. 5) or substantially fully folded (FIG. 6). In this regard, as used herein, the term "substantially 'binary state' device" is intended to refer to a device that tends to assume either a substantially fully deployed state or a substantially fully folded state, and as used herein, the term "substantially 'binary state' behavior" is intended to refer to a device that tends to assume either a substantially fully deployed state or a substantially fully folded state.

[0043] It should be noted that the substantially "binary state" behavior of pump body 60 is a result of forming the pump body with sidewalls 65 having a substantially circular cross-section that gives the pump body an "over-center" deformation characteristic. That is, the sidewalls of pump body 60 have a "break" mode in which they abruptly transition from a substantially fully deployed configuration to a substantially fully collapsed configuration, and a "restoration" mode in which they abruptly transition from a substantially fully collapsed configuration to a substantially fully deployed configuration. See FIG. 7. By forming the pump assembly 15 such that the side wall 65 of the pump body 60 and the pump flange 75 meet at a neck 77 (FIG. 5), the neck 77 has a relatively small width relative to the overall diameter of the pump body 60, and the recess 78 extends inwardly between the membrane 10 and the pump body 60, the pump body 60 has a substantially circular cross-section substantially around its entire circumference, and the pump body 60 radially compresses / expands with minimal interference from the pump flange 75, thereby enabling the pump body 60 to exhibit a substantially “binary state” behavior.

[0044] Also, prior art approaches to forming pump bodies using dome-shaped or square pump configurations do not provide the pump body with an abrupt change of state; rather, these prior art dome-shaped or square pump configurations provide the pump body with a more gradual change of state between the deployed and folded configurations as the pressure differential between the pressure of the fluid in the inner chamber and atmospheric pressure changes. See Figure 8, which is a graph showing the relationship between the diameter of the sidewall of a pump body having a dome-shaped or square configuration and the pressure differential between the pressure of the fluid in the inner chamber of the pump body and atmospheric pressure.

[0045] The side wall 65 of the pump body 60 of the pump assembly 15 is adapted to exhibit this abrupt change in state. As a result of careful construction, the pump assembly 15 is able to provide improved pump efficiency, an automatic pressure indicator to indicate the level of negative pressure created, and an automatic pressure limiter to limit the level of negative pressure created.

[0046] More specifically, by configuring the pump body 60 of the pump assembly 15 to abruptly change state between a substantially fully deployed configuration and a substantially fully collapsed configuration when the pressure differential between the pressure of the fluid in the inner chamber 70 and atmospheric pressure crosses a given threshold, the pump assembly 15 effectively returns to the substantially fully deployed configuration as long as the pressure differential between the pressure of the fluid in the inner chamber 70 and atmospheric pressure is below the given threshold. As a result, the pump assembly 15 returns to a substantially fully deployed configuration during compression (i.e., squeezing) as long as the pressure differential between the fluid in the inner chamber 70 and atmospheric pressure is below the given threshold, and thus remains fully effective in applying negative pressure to the wound chamber. This contrasts with the performance of prior art devices in which the pump body exhibits a gradual change of state between the deployed and collapsed configurations as the pressure differential between the fluid pressures in the inner chambers of the pump assembly changes, thereby progressively reducing the efficiency of the pump assembly as the pressure in the wound chamber decreases. This is because as negative pressure is created in the wound chamber, the pump body returns progressively less to its fully deployed configuration, thereby allowing the pump assembly to eject less fluid with each squeeze of the pump body. In other words, in prior art devices, the more negative pressure is created in the wound chamber, the less efficient the pump assembly becomes.

[0047] In a related manner, by configuring the pump body 60 to abruptly change state between a substantially fully deployed and a substantially fully collapsed configuration when the pressure differential between the pressure of the fluid in the inner chamber 70 and atmospheric pressure crosses a given threshold, the pump assembly 15 can function as an automatic pressure indicator to indicate the level of negative pressure created; i.e., so long as the pump body 60 of the pump assembly 15 returns to the substantially fully deployed configuration between squeezes, it will be readily apparent to an observer that the pressure in the inner chamber 70 (and thus the pressure in the wound chamber) will be below the given level. This contrasts significantly with the performance of prior art devices in which the pump body 60 provides a gradual state change between the deployed and collapsed configurations as the pressure differential between the pressures of the fluids in the inner chambers of the pump assembly changes, in which case the pump assembly cannot function as an automatic pressure indicator to indicate the level of negative pressure created.

[0048] Also in a related manner, by configuring the pump body 60 to abruptly change state between a substantially fully deployed and a substantially fully collapsed configuration when the pressure differential between the pressure of the fluid in the inner chamber 70 and atmospheric pressure crosses a given threshold, the pump assembly 15 can function as an automatic pressure limiter to limit the level of negative pressure generated, because as soon as the pump body 60 assumes a substantially fully collapsed configuration, the pump assembly 15 can no longer pump fluid from the wound chamber, essentially deactivating the pump assembly. This contrasts significantly with the performance of the prior art, where the pump body provides a gradual state change between the deployed and collapsed configurations as the pressure differential between the pressures of the fluids in the inner chambers changes, because the pump assembly is not effectively deactivated at a given pressure differential.

[0049] The pressure differential required to transition the pump body 60 between a substantially fully deployed configuration and a substantially fully collapsed configuration (i.e., the "given threshold" discussed above) can be adjusted by varying one or more characteristics of the pump body 60, such as by forming the side wall 65 of the pump body 60 from a material having a particular durometer, adjusting the thickness of the side wall 65 of the pump body 60, adjusting the diameter of the inner chamber 70 of the pump body 60, or adjusting the thickness of the inner chamber 70 of the pump body 60. It should be understood that the control may be "tuned" (i.e., adjusted) to a particular level, such as by adjusting the control's frequency.

[0050] In general, it has been found that excellent therapeutic results can be achieved when the pressure differential required to transition the pump body between a substantially fully deployed configuration and a substantially fully collapsed configuration (i.e., the "given threshold" described above) is between about 8.00 kPa (60 mmHg) and about 24.00 kPa (180 mmHg). In other words, it has been found that excellent therapeutic results can be achieved when the pump body 60 transitions between a substantially fully deployed configuration (FIG. 5) and a substantially fully collapsed configuration (FIG. 6) at a negative pressure of about 8.00 kPa (60 mmHg) and about 24.00 kPa (180 mmHg). If the pump body 60 transitions between the two states at a lower pressure (i.e., if the pump body 60 transitions at a negative pressure less than about 60 mmHg), it is believed that sufficient suction will not be provided at the wound site to effectively draw contaminants and microorganisms from the wound site and / or exudate from the wound site and / or promote a beneficial biological response at the wound site. Also, if the pump body 60 transitions between the two states at a higher pressure (i.e., if the pump body 60 transitions at a negative pressure greater than about 180 mmHg), it is believed that the suction provided at the wound site may cause trauma to tissue (e.g., blister formation, capillary leakage, etc.).

[0051] In one preferred form of the invention, pump body 60 of pump assembly 15 is configured to abruptly transition between a substantially fully deployed configuration and a substantially fully collapsed configuration when the pressure differential between the pressure of the fluid in inner chamber 70 and atmospheric pressure exceeds 10.67 kPa (80 mmHg). Thus, in this form of the invention, as long as the negative pressure in the wound chamber is less than 90.66 kPa (680 mmHg) (assuming atmospheric pressure is 101.33 kPa (760 mmHg)), the pump assembly 15 will return to a substantially fully deployed configuration between squeezes of the pump body to maintain pump efficiency in applying suction to the wound chamber; as soon as the negative pressure in the wound chamber exceeds 90.66 kPa (680 mmHg) (assuming atmospheric pressure is 101.33 kPa (760 mmHg)), the pump assembly 15 will assume a substantially fully collapsed configuration and operate as an automatic pressure indicator that the negative pressure level generated at the wound site has exceeded 10.67 kPa (80 mmHg) and will automatically deactivate the pump assembly 15 so that the negative pressure level generated at the wound site cannot exceed 10.67 kPa (80 mmHg).

[0052] It should be noted that inasmuch as the pump body 60 of the pump assembly 15 has a substantially cylindrical configuration, the NPWT dressing 5 has a low profile. It should also be noted that inasmuch as pump body 60 of pump assembly 15 is configured to be squeezed between a user's thumb and index finger, the compressive force applied to pump body 60 is applied parallel to the surface of the skin, ensuring no trauma to the wound during use (i.e., during pumping of pump assembly 15). This is in stark contrast to prior art NPWT dressings which use a dome-like configuration and require the compressive force to be applied toward the wound. Exemplary Uses In one preferred form of the invention, and referring now to Figures 9-16, the NPWT dressing 5 is intended to be used as follows.

[0053] First, the NPWT dressings 5 ​​are removed from the box. In one form of the invention, each individual NPWT dressing 5 is contained within a separate sterile package, and multiple sterile packages are contained within the box. See FIG.

[0054] The NPWT dressing 5 is then packaged in a sterile package ready for use (FIG. 11). (Figure 10). To apply the NPWT dressing 5 to the wound site, the release liner 50 is removed from the wound-side surface 25 of the membrane 10. See Figure 12. The NPWT dressing 5 is then positioned against the patient's skin such that the wound-side surface 25 of the membrane 10 is positioned against the wound and the adhesive 45 secures the NPWT dressing 5 to the patient's skin, thereby forming a substantially air-tight seal with the patient's skin around the perimeter of the wound chamber. See Figure 13.

[0055] It should be noted that when the NPWT dressing 5 is applied to the patient's skin, the wound side port 82 of the wound side passageway 80 of the pump assembly 15 is open to the wound chamber. It should also be noted that prior to placing the NPWT bandage 5 on the patient's skin, a layer 102 of gauze (or other absorbent wound dressing) can be placed at the wound site such that the layer of gauze (or other absorbent wound dressing) is interposed between the wound and the wound-side passageway 80 of the pump assembly 15. As a result, exudate from the wound is absorbed by the gauze (or other absorbent wound dressing). It should also be noted that if desired, the layer of gauze (or other absorbent wound dressing) 102 can be attached (i.e., secured) to the wound-side surface of the membrane 10, such as during manufacture, such that the layer of gauze (or other absorbent wound dressing) 102 is carried to the wound site by the NPWT bandage 5 and applied to the wound simultaneously with the NPWT bandage 5.

[0056] Next, with the NPWT dressing 5 secured to the patient's skin, the removable reinforcement 55 is removed from the air-facing surface 30 of the membrane 10. See FIG. At this point, the NPWT dressing 5 can be used to apply negative pressure to the wound chamber. This is accomplished by squeezing the sidewall 65 of the pump body 60 between the user's thumb and index finger, compressing the pump body 60 into a substantially fully collapsed configuration, thereby allowing fluid (e.g., air, liquid, etc.) to exit the inner chamber 70 of the pump body 60 via the atmosphere-side passageway 85 and the atmosphere-side one-way valve 95. See FIG. 15. Fluid within the inner chamber 70 of the pump body 60 is prevented from exiting the inner chamber 70 through the wound-side passageway 80 due to the presence of the wound-side one-way valve 90. The sidewall 65 of the pump body 60 is then released, allowing the elastic pump body 60 to return to a substantially fully deployed configuration, thereby creating negative pressure within the inner chamber 70 and the wound-side passageway 80, causing fluid (e.g., fluid within the wound chamber) below the wound-side surface 25 of the membrane 10 to be drawn into the inner chamber 70 through the wound-side passageway 85 and the wound-side one-way valve 90. It should be noted that due to the presence of the atmosphere-side one-way valve 95, air at the atmosphere is prevented from entering the inner chamber 70 through the atmosphere-side passage 85.

[0057] This process of squeezing and releasing the sidewalls 65 of the pump body 60 is repeated until the pump body 60 of the pump assembly 15 remains in a substantially fully folded configuration (i.e., the sidewalls 65 of the pump body 60 are deflected inwardly) even when the sidewalls 65 of the pump body 60 are not being manually squeezed. See FIG. 16. When the pump body 60 of the pump assembly 15 remains in a substantially fully folded configuration even when the sidewalls 65 of the pump body 60 are not being manually squeezed, an observer will know that the pressure difference between the pressure of the fluid in the inner chamber 70 (and wound chamber) and atmospheric pressure exceeds a desired threshold, indicating that a desired negative pressure level has been achieved at the wound site. It should be noted that when the pump body 60 of the pump assembly 15 remains in a substantially fully folded configuration even when the sidewalls 65 of the pump body 60 are not being manually squeezed, the pump assembly 15 is effectively deactivated, since it is not possible to continue using the pump assembly with the sidewalls 65 in a substantially fully folded configuration.

[0058] At this point, the removable cap 100 is used to close the air side of the air passage 85. Port 87 can be sealed. The NPWT dressing 5 is left in place over the wound for a suitable period of time (e.g., several days) to protect the wound from contaminants and microorganisms during healing, draw exudate from the wound, and promote beneficial biological responses at the wound site. When the negative pressure created in the wound chamber due to leakage drops below a given threshold (which is evident to an observer by the sidewall 65 of the pump body 60 returning to a substantially fully deployed configuration), the atmospheric port 87 of the atmospheric passageway 85 is unsealed (i.e., by removing the removable cap 100), and the pump assembly 15 can then be used as discussed above to re-establish the desired negative pressure in the wound chamber (i.e., by repeatedly squeezing and releasing the sidewall 65 of the pump body 60).

[0059] Optionally, the NPWT dressing 5 may be removed from the patient's skin by simply peeling the membrane 10 from the patient's skin. Pump body having notches for improving the substantially "binary state" behavior of the pump body As described above, the pump body 60 of the pump assembly 15 is preferably configured, in particular, such that the pump body abruptly changes state between (i) a substantially fully deployed configuration in which the side walls 65 of the pump body 60 and the inner chamber 70 of the pump body 60 have a substantially circular cross-section (see FIG. 5 ) when the pressure difference between the pressure of the fluid in the inner chamber 70 and atmospheric pressure is below a given threshold, and (ii) a substantially fully deployed configuration in which the side walls 65 of the pump body 60 are deflected inwardly (see FIG. 6 ) when the pressure difference between the pressure of the fluid in the inner chamber 70 and atmospheric pressure exceeds a given threshold.

[0060] Also, as noted above, it is noted that this substantially "binary state" behavior of pump body 60 is achieved by forming the pump body with a substantially circular cross-section that gives the body an "over-center" deformation characteristic. That is, the sidewalls of pump body 60 are adapted to have a "break" mode in which they abruptly transition from a substantially fully deployed configuration to a substantially fully collapsed configuration, and a "restoration" mode in which they abruptly transition from a substantially fully collapsed configuration to a substantially fully deployed configuration. See FIG. 7. As described above, by forming the pump assembly 15 such that the side wall 65 of the pump body 60 and the pump flange 75 meet at the neck 77 (FIG. 5), the neck 77 has a relatively small width relative to the overall diameter of the pump body 60, and the recess 78 extends inwardly between the membrane 10 and the pump body 60, the pump body 60 has a substantially circular cross-section substantially around its entire circumference, allowing the pump body 60 to freely radially compress / expand with minimal interference from the pump flange 75, thereby allowing the pump body 60 to exhibit a substantially “binary state” behavior.

[0061] If desired, the pump body 60 can be modified to enhance the substantially "binary state" behavior of the pump body. 17-20, notches 105 can be formed in pump body 60 (e.g., at the "9 o'clock," "12 o'clock," and "3 o'clock" positions) to improve the substantially "binary state" behavior of the pump body by further inducing pump body 60 to assume only a substantially fully deployed or substantially fully collapsed configuration. Note that the more true "binary state" behavior the pump body 60 exhibits, the better the pump efficiency will be and the better the pump assembly 15 will act as an automatic pressure indicator and automatic pressure limiter. NPWT dressing incorporating gauze (or other absorbent wound dressing) and utilizing an improved pump assembly 21-25, there is shown another Negative Pressure Wound Therapy (NPWT) bandage 5 formed in accordance with the present invention. The NPWT bandage 5 shown in FIGS. 21-25 essentially comprises: It is the same as the NPWT bandage 5 shown in Figures 1-16 and the NPWT bandage 5 shown in Figures 17-20, except that (i) in the configuration shown in Figures 21-25, the membrane 10 comprises multiple layers incorporating gauze (or other absorbent wound dressing), and (ii) in the configuration shown in Figures 21-25, the pump assembly 15 has a modified configuration and is secured to the membrane 10 using a different technique.

[0062] More specifically, in this form of the invention, the membrane 10 comprises a lower skin-contacting polyurethane layer 110 having a central opening 115, an intermediate foam (or gauze or other absorbent wound dressing) layer 120 for placement over the central opening 115 of the lower skin-contacting polyurethane layer 110, and an upper polyurethane layer 125 for placement over the intermediate foam layer 120 and the lower skin-contacting polyurethane layer 110. In a preferred form of the invention, the upper polyurethane layer 125 is formed from a material that is substantially air impermeable. And, in a preferred form of the invention, the upper polyurethane layer 125 and the lower skin-contacting polyurethane layer 110 have perimeters of the same size, whereby the upper polyurethane layer 125 does not contact the patient's skin. The perimeters of the upper polyurethane layer 125 and the lower skin-contacting polyurethane layer 110 are secured to one another, capturing the intermediate foam layer 120 therebetween. The intermediate foam layer 120 is (i) larger than the perimeter of the central opening 115 of the lower skin contacting polyurethane layer 110 and (ii) smaller than the perimeter of the lower skin contacting polyurethane layer 110 and the upper polyurethane layer 125. In this manner, when the NPWT dressing 5 is positioned with the central opening 115 of the lower skin contacting polyurethane layer 110 over a wound, fluid from the wound can pass through the central opening 115 of the lower skin contacting polyurethane layer 110 to the intermediate foam layer 120. It will be appreciated that the adhesive 45 is positioned on the wound-facing surface of the lower skin contacting polyurethane layer 110 such that a substantially airtight seal can be established by the NPWT dressing 5 around the perimeter of the wound (i.e., forming the wound chamber discussed above). An opening 130 is formed in the upper polyurethane layer 125 and overlaps the central opening 115 of the lower skin-contacting polyurethane layer 110, allowing the wound-side passageway 80 of the pump assembly 15 to access fluid (e.g., air, liquid, etc.) within the wound chamber for evacuation during pumping of the pump assembly 15 (i.e., via the opening 130 in the upper polyurethane layer 125, the opening in the intermediate foam layer 120, and the central opening 115 in the lower skin-contacting polyurethane layer 110).

[0063] The pump assembly 15 utilized in the NPWT dressing 5 of Figures 21-25 is generally similar to the pump assembly 15 described above, except that it includes a pair of seats 135A, 135B for mounting the pump assembly 15 to the membrane 10. More specifically, the seat 135A includes one end of the pump body 60 and is attached (e.g., by adhesive 137) to the upper surface of the membrane 10 (i.e., to the upper surface of the upper polyurethane layer 125) such that the wound side passageway 80 and the wound side one-way valve 90 are aligned with the opening 130 in the upper polyurethane layer 125 (and thus in fluid communication with the wound chamber). The seat 135B includes the other end of the pump body 60 and is attached (e.g., by adhesive 138) to the upper surface of the membrane 10 (i.e., to the upper surface of the upper polyurethane layer 125). The interstitial portion 140 of the pump body 60 is elevated above the upper polyurethane layer 125 of the membrane 10 and rests suspended between the pedestals 135A and 135B, thereby forming a space 145 between the interstitial portion 140 of the pump body 60 and the upper polyurethane layer 135 of the membrane 10. Because the interstitial portion 140 of the pump body 60 is suspended above the membrane 10 by the pedestals 135A and 135B, rather than being directly attached to the membrane 10, the interstitial portion 140 of the pump body 60 can be formed with a true circular cross-section, thereby enhancing the substantially "binary state" behavior of the NPWT dressing. It will be appreciated that the pump body 60 can incorporate one or more of the notches 105 described above to further enhance the substantially "binary state" behavior of the NPWT dressing. Variations of the Preferred Embodiment It should be understood that many additional changes in the details, materials, steps and arrangements of parts which have been described and illustrated herein for the purpose of explaining the principles of the invention may be made by those skilled in the art and still remain within the principles and scope of the invention. (1) A first aspect of the present invention is a Negative Pressure Wound Therapy (NPWT) bandage for applying negative pressure to a wound, the NPWT bandage comprising: a membrane configured for placement over a wound to form a wound chamber between the membrane and the wound, the membrane including a wound-side surface, an atmosphere-side surface, and an opening extending through the membrane from the wound-side surface to the atmosphere-side surface; and a pump assembly carried by the membrane, the pump assembly comprising: a pump body having a wall structure disposed about a pump chamber, at least a portion of the wall structure being elastic; a wound-side passage extending through the wall structure and communicating with the wound chamber through the opening formed in the membrane; and a wound-side one-way valve disposed in the wound-side passage, the wound-side one-way valve allowing fluid to flow from the wound chamber to the pump chamber through the wound-side passage, a wound side one-way valve configured to prevent fluid flow from the pump chamber to the wound chamber through a wound side passage; an atmosphere side passage extending through the wall structure connecting the pump chamber to atmosphere; and an atmosphere side one-way valve disposed within the atmosphere side passage, the atmosphere side one-way valve configured to allow fluid flow from the pump chamber to atmosphere through the atmosphere side passage but to prevent fluid flow from atmosphere to the pump chamber through the atmosphere side passage, such that when a compressive force is applied to the wall structure of the pump body, fluid in the pump chamber is forced out of the pump chamber via the atmosphere side passage and when the compressive force applied to the wall structure of the pump body is subsequently reduced, fluid in the wound chamber is drawn into the pump chamber through the wound side passage. (2) In a second aspect of the present invention, in the first aspect, the membrane comprises a plurality of layers. (3) In a third aspect of the present invention, in the second aspect, the membrane comprises a substantially air-impermeable layer and an absorbent layer, the absorbent layer being positioned on the wound side of the substantially air-impermeable layer. (4) In a fourth aspect of the present invention, the third aspect further comprises an additional layer, and the absorbent layer is disposed between the substantially air-impermeable layer and the additional layer. (5) In a fifth aspect of the present invention, in the first aspect, a portion of the pump assembly extends through the opening formed in the membrane. (6) In a sixth aspect of the present invention, in the fifth aspect, the pump assembly includes a flange connected to the pump body, and further, the flange is fixed to the wound side surface of the membrane, and the pump body extends through the opening formed in the membrane. (7) In a seventh aspect of the present invention, in the sixth aspect, the flange is integrally formed with the pump body. (8) In an eighth aspect of the present invention, in the seventh aspect, a neck is formed between the pump body and the flange, and further, a pair of recesses extend inwardly between the pump body and the flange. (9) In a ninth aspect of the present invention, in the first aspect, the pump assembly is attached to the membrane by a pair of bases, one of the bases further including a passageway on the wound side. (10) In a tenth aspect of the present invention, in the ninth aspect, the pump body is suspended between the pair of pedestals and spaced apart from the membrane. (11) In an eleventh aspect of the present invention, in the first aspect, the pump assembly includes a removable cap for selectively closing the atmospheric side passage. (12) In the twelfth aspect of the present invention, in the first aspect, the wound side surface of the membrane comprises an adhesive. (13) In a thirteenth aspect of the present invention, in the twelfth aspect, a release liner is placed on the wound side surface of the membrane over the adhesive. (14) In a fourteenth aspect of the present invention, in the first aspect, a removable reinforcement member is disposed on the air-side surface of the membrane. (15) In the fifteenth aspect of the present invention, in the first aspect, the pump body of the pump assembly assumes a substantially fully deployed configuration when a pressure difference between the pressure of the fluid in the pump chamber and atmospheric pressure is less than a predetermined threshold, and the pump body of the pump assembly assumes a substantially fully folded configuration when the pressure difference between the pressure of the fluid in the pump chamber and atmospheric pressure is greater than the predetermined threshold. (16) In a sixteenth aspect of the present invention, in the fifteenth aspect, the pump body abruptly changes state between the substantially fully deployed configuration and the substantially fully folded configuration, and between the substantially fully folded configuration and the substantially fully deployed configuration, when the pressure differential crosses the predetermined threshold, effectively creating a substantially "binary state" device. (17) In the seventeenth aspect of the present invention, in the fifteenth aspect, the predetermined threshold value is about 8.00 kPa (60 mmHg) to about 24.00 kPa (180 mmHg). (18) In an eighteenth aspect of the present invention, in the fifteenth aspect, the pump body is configured to provide an "over-center" deformation characteristic. (19) In a nineteenth aspect of the present invention, in the fifteenth aspect, the pump body includes a substantially circular cross-section. (20) In a twentieth aspect of the present invention, in the nineteenth aspect, the pump body comprises a substantially cylindrical configuration. (21) In a twenty-first aspect of the present invention, in the fifteenth aspect, (i) when the pressure difference between the pressure of the fluid in the pump chamber and atmospheric pressure is less than the predetermined threshold, the wall structure of the pump body and the pump chamber include a substantially circular cross-section, and (ii) when the pressure difference between the pressure of the fluid in the pump chamber and atmospheric pressure exceeds the predetermined threshold, the wall structure of the pump body deflects inwardly. (22) In a twenty-second aspect of the present invention, in the fifteenth aspect, the pump assembly includes a removable cap for selectively closing the atmospheric side passage. (23) In the twenty-third aspect of the present invention, in the fifteenth aspect, the wound side surface of the membrane comprises an adhesive. (24) In a twenty-fourth aspect of the present invention, in the twenty-third aspect, a release liner is placed on the wound side surface of the membrane over the adhesive. (25) In a twenty-fifth aspect of the present invention, in the fifteenth aspect, a removable reinforcement member is disposed on the air-side surface of the membrane. (26) In the 26th aspect of the present invention, in the 15th aspect, the pump assembly further comprises a flange connected to the pump body, the flange being fixed to the wound side surface of the membrane, and the pump body extending through the opening formed in the membrane. (27) In a 27th aspect of the present invention, in the 26th aspect, the flange is integrally formed with the pump body. (28) In a twenty-eighth aspect of the present invention, in the fifteenth aspect, a notch is formed in the wall structure of the pump body to facilitate substantially "binary state" behavior. (29) A twenty-ninth aspect of the present invention is a method for applying negative pressure to a wound, comprising the steps of preparing a Negative Pressure Wound Therapy (NPWT) dressing, the NPWT dressing comprising a membrane configured for placement over a wound to form a wound chamber between the membrane and the wound, the membrane including a wound-side surface, an atmosphere-side surface, and an opening extending through the membrane from the wound-side surface to the atmosphere-side surface, and a pump assembly carried by the membrane, the pump assembly including a pump having a wall structure disposed about a pump chamber. a wound side passage extending through the wall structure and communicating with the wound chamber through the opening formed in the membrane; a wound side one-way valve disposed within the wound side passage, the wound side one-way valve configured to allow fluid to flow from the wound chamber to the pump chamber through the wound side passage but to prevent fluid from flowing from the pump chamber to the wound chamber through the wound side passage; an atmosphere side passage extending through the wall structure connecting the pump chamber and the atmosphere; and an atmosphere side one-way valve disposed within the atmosphere side passage, the atmosphere side one-way valve configured to allow fluid to flow from the pump chamber to atmosphere through the atmosphere side passage but to prevent fluid from flowing from atmosphere to the pump chamber through the atmosphere side passage, the wound chamber is forced out of the wound chamber and when the compressive force applied to the wall structure of the pump body is subsequently reduced, fluid in the wound chamber is drawn into the pump chamber through the wound side passage; positioning the NPWT dressing over the wound to form a wound chamber between the membrane and the wound; and applying a compressive force to the wall structure of the pump body and then reducing the compressive force applied to the wall structure of the pump body to apply a negative pressure to the wound. (30) In a thirtieth aspect of the present invention, in the twenty-ninth aspect, the membrane comprises a plurality of layers. (31) In the thirty-first aspect of the present invention, in the thirtieth aspect, the membrane comprises a substantially air-impermeable layer and an absorbent layer, the absorbent layer being positioned on the wound side of the substantially air-impermeable layer. (32) In a thirty-second aspect of the present invention, in the thirty-first aspect, the device further comprises an additional layer, and the absorbent layer is disposed between the substantially air-impermeable layer and the additional layer. (33) In a thirty-third aspect of the present invention, in the twenty-ninth aspect, a portion of the pump assembly extends through the opening formed in the membrane. (34) In a thirty-fourth aspect of the present invention, in the thirty-third aspect, the pump assembly includes a flange connected to the pump body, further, the flange is fixed to the wound side surface of the membrane, and the pump body extends through the opening formed in the membrane. (35) In a thirty-fifth aspect of the present invention, in the thirty-fourth aspect, the flange is integrally formed with the pump body. (36) In a thirty-sixth aspect of the present invention, in the thirty-fifth aspect, a neck is formed between the pump body and the flange, and further, a pair of recesses extend inwardly between the pump body and the flange. (37) In the thirty-seventh aspect of the present invention, in the twenty-ninth aspect, the pump assembly is attached to the membrane by a pair of bases, one of the bases further including a passageway on the wound side. (38) In a thirty-eighth aspect of the present invention, in the thirty-seventh aspect, the pump body is suspended between the pair of pedestals and spaced apart from the membrane. (39) In a thirty-ninth aspect of the present invention, in the twenty-ninth aspect, the pump assembly includes a removable cap for selectively closing the atmospheric side passage. (40) In the fortieth aspect of the present invention, in the twenty-ninth aspect, the wound side surface of the membrane comprises an adhesive. (41) In the forty-first aspect of the present invention, in the twenty-ninth aspect, a release liner is placed on the wound side surface of the membrane over the adhesive. (42) In the forty-second aspect of the present invention, in the twenty-ninth aspect, a removable reinforcement member is disposed on the air-side surface of the membrane. (43) In the forty-third aspect of the present invention, in the twenty-ninth aspect, the pump body of the pump assembly assumes a substantially fully deployed configuration when a pressure difference between the fluid pressure in the pump chamber and atmospheric pressure is less than a predetermined threshold, and the pump body of the pump assembly assumes a substantially fully folded configuration when the pressure difference between the fluid pressure in the pump chamber and atmospheric pressure is greater than the predetermined threshold. (44) In a forty-fourth aspect of the present invention, in the forty-third aspect, the pump body abruptly changes state between the substantially fully deployed configuration and the substantially fully collapsed configuration, and between the substantially fully collapsed configuration and the substantially fully deployed configuration, when the pressure differential straddles the predetermined threshold, effectively creating a substantially "binary state" device. (45) In the 45th aspect of the present invention, in the 43rd aspect, the predetermined threshold value is about 8.00 kPa (60 mmHg) to about 24.00 kPa (180 mmHg). (46) In a forty-sixth aspect of the present invention, in the forty-third aspect, the pump body is configured to provide an “over-center” deformation characteristic. (47) In a forty-seventh aspect of the present invention, in the twenty-ninth aspect, the pump body includes a substantially circular cross-section. (48) In a forty-eighth aspect of the present invention, in the forty-seventh aspect, the pump body comprises a substantially cylindrical configuration. (49) In a forty-ninth aspect of the present invention, in the forty-third aspect, (i) when the pressure difference between the pressure of the fluid in the pump chamber and atmospheric pressure is less than the predetermined threshold, the wall structure of the pump body and the pump chamber include a substantially circular cross-section, and (ii) when the pressure difference between the pressure of the fluid in the pump chamber and atmospheric pressure exceeds the predetermined threshold, the wall structure of the pump body deflects inwardly. (50) In a 50th aspect of the present invention, in the 43rd aspect, the pump assembly includes a removable cap for selectively closing the atmospheric side passage. (51) In the 51st aspect of the present invention, in the 43rd aspect, the wound side surface of the membrane comprises an adhesive. (52) In the 52nd aspect of the present invention, in the 51st aspect, a release liner is placed on the wound side surface of the membrane over the adhesive. (53) In a fifty-third aspect of the present invention, in the forty-third aspect, a removable reinforcement member is disposed on the air-side surface of the membrane. (54) In the 54th aspect of the present invention, in the 43rd aspect, the pump assembly further comprises a flange connected to the pump body, the flange being fixed to the wound side surface of the membrane, and the pump body extending through the opening formed in the membrane. (55) In the 55th aspect of the present invention, in the 54th aspect, the flange is integrally formed with the pump body. (56) In a fifty-sixth aspect of the present invention, in the forty-third aspect, a notch is formed in the wall structure of the pump body to facilitate substantially "binary state" behavior. (57) A 57th aspect of the present invention is a Negative Pressure Wound Therapy (NPWT) dressing for applying negative pressure to a wound, the NPWT dressing comprising: a membrane configured for placement over a wound to form a wound chamber between the membrane and the wound, the membrane including a wound-side surface, an atmosphere-side surface, and an opening extending through the membrane from the wound-side surface to the atmosphere-side surface; and a pump carried by the membrane, the pump comprising a wall chamber disposed about the pump chamber, at least a portion of the wall chamber being elastic, and further, the pump chamber communicating with the wound chamber through the opening formed in the membrane, no portion of the pump chamber being defined by the wound. (58) A 58th aspect of the present invention is a Negative Pressure Wound Therapy (NPWT) dressing for applying negative pressure to a wound, the NPWT dressing comprising: a membrane configured for placement over a wound to form a wound chamber between the membrane and the wound, the membrane including a wound-side surface, an atmosphere-side surface, and an opening extending through the membrane from the wound-side surface to the atmosphere-side surface; and a pump carried by the membrane, the pump comprising a wall chamber disposed about the pump chamber, at least a portion of the wall chamber being elastic, and further, the pump chamber communicating with the wound chamber through the opening formed in the membrane, the pump not applying positive pressure to the wound. (59) A fifty-ninth aspect of the present invention is a negative pressure wound therapy (NPWT) dressing for applying negative pressure to a wound, the NPWT dressing comprising: a membrane configured for placement over a wound to form a wound chamber between the membrane and the wound, the membrane including a wound-side surface, an atmosphere-side surface, and an opening extending through the membrane from the wound-side surface to the atmosphere-side surface; and a pump carried by the membrane, the pump comprising a wall chamber disposed about the pump chamber, at least a portion of the wall chamber being elastic, the pump chamber communicating with the wound chamber through the opening formed in the membrane, the pump being connected to the wound chamber such that a reduction in the volume of the pump chamber does not result in a change in pressure in the wound chamber.

Claims

1. 1. A negative pressure wound therapy (NPWT) bandage for applying negative pressure to a wound, said NPWT bandage comprising: a membrane configured for placement over a wound to form a wound chamber between the membrane and the wound, the membrane including a wound-side surface, an atmosphere-side surface, and an opening extending through the membrane from the wound-side surface to the atmosphere-side surface; A pump assembly carried by the membrane, the pump assembly comprising: a pump body having a resilient outer wall defining a single inner hollow chamber; a wound side passageway extending through the outer wall and communicating with the wound chamber through the opening formed in the membrane; a wound side one-way valve disposed within the wound side passageway, the wound side one-way valve configured to allow fluid to flow from the wound chamber to the inner hollow chamber through the wound side passageway but to prevent fluid from flowing from the inner hollow chamber to the wound chamber through the wound side passageway; an atmosphere-side passageway extending through the outer wall and connecting the inner hollow chamber with the atmosphere; an atmosphere-side one-way valve disposed in the atmosphere-side passage, the atmosphere-side one-way valve configured to allow fluid to flow from the inner hollow chamber to the atmosphere through the atmosphere-side passage but to prevent fluid from flowing from the atmosphere to the inner hollow chamber through the atmosphere-side passage; a pump assembly comprising: Equipped with When a compressive force is applied to the outer wall of the pump body, fluid in the inner hollow chamber is forced out of the inner hollow chamber through the atmosphere side passage, and when the compressive force applied to the outer wall of the pump body is subsequently reduced, fluid in the wound chamber is drawn into the inner hollow chamber through the wound side passage.

2. The NPWT dressing of claim 1 , wherein the membrane comprises multiple layers.

3. 3. The NPWT dressing of claim 2, wherein the membrane comprises a substantially air impermeable layer and an absorbent layer, the absorbent layer being disposed on the wound side of the substantially air impermeable layer.

4. 4. The NPWT dressing of claim 3, further comprising an additional layer, said absorbent layer being disposed between said substantially air impermeable layer and said additional layer.

5. The NPWT bandage of claim 1 , wherein a portion of the pump assembly extends through the opening formed in the membrane.

6. The NPWT dressing of claim 5, wherein the pump assembly comprises a flange, the flange being secured to the wound-side surface of the membrane, and the pump body extending through the opening formed in the membrane.

7. The NPWT dressing of claim 6 , wherein the flange is integrally formed with the pump body.

8. 8. The NPWT bandage of claim 7, further comprising a neck defined between said pump body and said flange, and further comprising a pair of recesses extending inwardly between said pump body and said flange.

9. The NPWT dressing of claim 1 , wherein the pump assembly is attached to the membrane by a pair of pedestals, one of the pedestals including a passageway on the wound side.

10. The NPWT bandage of claim 9 , wherein the pump body is suspended between the pair of pedestals and spaced from the membrane.

11. 10. The NPWT bandage of claim 1, wherein said pump assembly includes a removable cap for selectively closing said atmosphere side passageway.

12. The NPWT dressing of claim 1 , wherein the wound-facing surface of the membrane comprises an adhesive.

13. The NPWT dressing of claim 12 , wherein a release liner is disposed on the wound-side surface of the membrane over the adhesive.

14. The NPWT dressing of claim 1 , wherein a removable stiffener is disposed on the air-facing surface of the membrane.

15. 2. The NPWT bandage of claim 1, wherein the pump body of the pump assembly assumes a substantially fully deployed configuration when a pressure difference between the pressure in the inner hollow chamber and atmospheric pressure is below a predetermined threshold, and wherein the pump body of the pump assembly assumes a substantially fully collapsed configuration when the pressure difference between the pressure in the inner hollow chamber and atmospheric pressure is above the predetermined threshold.

16. 16. The NPWT bandage of claim 15, wherein the pump body abruptly changes state between the substantially fully deployed configuration and the substantially fully collapsed configuration, and between the substantially fully collapsed configuration and the substantially fully deployed configuration, when the pressure differential straddles the predetermined threshold, effectively creating a substantially "binary state" device.

17. 16. The NPWT bandage of claim 15, wherein the predetermined threshold is from about 8.00 kPa (60 mmHg) to about 24.00 kPa (180 mmHg).

18. The NPWT bandage of claim 15, wherein the pump body is configured to provide an "over-center" deformation characteristic.

19. 16. The NPWT bandage of claim 15, wherein the pump body includes a substantially circular cross-section.

20. 20. The NPWT bandage of claim 19, wherein the pump body comprises a substantially cylindrical configuration.

21. 16. The NPWT bandage of claim 15, wherein (i) when the pressure difference between the pressure in the inner hollow chamber and atmospheric pressure is less than the predetermined threshold, the outer wall of the pump body and the inner hollow chamber comprise a substantially circular cross-section, and (ii) when the pressure difference between the pressure in the inner hollow chamber and atmospheric pressure exceeds the predetermined threshold, the outer wall of the pump body deflects inwardly.

22. 16. The NPWT bandage of claim 15, wherein the pump assembly includes a removable cap for selectively closing the atmosphere side passageway.

23. 16. The NPWT dressing of claim 15, wherein the wound-facing surface of the membrane comprises an adhesive.

24. 24. The NPWT dressing of claim 23, wherein a release liner is disposed on the wound-side surface of the membrane over the adhesive.

25. The NPWT dressing of claim 15 , wherein a removable stiffener is disposed on the air-facing surface of the membrane.

26. The NPWT bandage of claim 15, wherein the pump assembly includes a flange, the flange being fixed to the wound side surface of the membrane, and the pump body extending through the opening formed in the membrane.

27. 27. The NPWT bandage of claim 26, wherein the flange is integrally formed with the pump body.

28. The NPWT bandage of claim 1, wherein a notch is formed in the outer wall of the pump body.

29. The NPWT bandage of claim 1, wherein no portion of the inner hollow chamber is defined by the wound.

30. The NPWT dressing of claim 1 , wherein the pump assembly does not apply positive pressure to the wound.

31. 10. The NPWT dressing of claim 1, wherein the pump assembly is connected to the wound chamber such that a reduction in the volume of the inner hollow chamber does not result in a change in pressure in the wound chamber.

32. The NPWT bandage of claim 1, wherein the elastic outer wall is airtight.

33. The NPWT bandage of claim 1, wherein the inner hollow chamber does not contain any solid material.

34. The NPWT bandage of claim 1, wherein the pump assembly includes a pump flange, the pump flange being fixed to the membrane.

35. An NPWT bandage as described in claim 34, wherein a neck portion is formed between the pump body and the pump flange.

36. An NPWT bandage as described in claim 35, wherein a pair of recesses extend between the pump body and the pump flange, and in at least a portion of each recess, the thickness of the outer wall of the pump body is smaller.

37. The NPWT bandage of claim 35, wherein a pair of recesses extend between the pump body and the pump flange, and wherein the inner surfaces of each recess face in a direction perpendicular to the direction in which the pump flange extends.

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