WO2023012551A1

WO2023012551A1 - Negative pressure accumulator to control fluid flow through filter

Info

Publication number: WO2023012551A1
Application number: PCT/IB2022/056529
Authority: WO
Inventors: Shannon C. Ingram; Bobby Keen
Original assignee: Kci Manufacturing Unlimited Company
Priority date: 2021-08-04
Filing date: 2022-07-15
Publication date: 2023-02-09

Abstract

An accumulator for positioning inline between a canister and a therapy device is described. The accumulator can include a fluid container having a fluid chamber, a first port configured to be fluidly coupled to a pressure sensor of the therapy device, and a second port configured to be fluidly coupled to an unknown volume. The accumulator can also include a fluid passage disposed in the fluid container and fluidly isolated from the fluid chamber, a third port configured to be fluidly coupled to a negative-pressure supply of the therapy device, the third port fluidly coupled to the fluid passage, and a fourth port configured to be fluidly coupled to the unknown volume, the fourth port fluidly coupled to the fluid passage.

Description

NEGATIVE PRESSURE ACCUMULATOR TO CONTROL FLUID FLOW THROUGH

FILTER

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 63/229,240, filed on August 4, 2021, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

[0002] The invention set forth in the appended claims relates generally to system volume determinations in tissue treatment systems and more particularly, but without limitation, to an accumulator for use in determining a volume of a tissue site.

BACKGROUND

[0003] Clinical studies and practice have shown that reducing pressure in proximity to a tissue site can augment and accelerate growth of new tissue at the tissue site. The applications of this phenomenon are numerous, but it has proven particularly advantageous for treating wounds. Regardless of the etiology of a wound, whether trauma, surgery, or another cause, proper care of the wound is important to the outcome. Treatment of wounds or other tissue with reduced pressure may be commonly referred to as "negative-pressure therapy," but is also known by other names, including "negative-pressure wound therapy," "reduced-pressure therapy," "vacuum therapy," "vacuum-assisted closure," and "topical negative-pressure," for example. Negative-pressure therapy may provide a number of benefits, including migration of epithelial and subcutaneous tissues, improved blood flow, and micro-deformation of tissue at a wound site. Together, these benefits can increase development of granulation tissue and reduce healing times.

[0004] There is also widespread acceptance that cleansing a tissue site can be highly beneficial for new tissue growth. For example, a wound or a cavity can be washed out with a liquid solution for therapeutic purposes. These practices are commonly referred to as "irrigation" and "lavage" respectively. "Instillation" is another practice that generally refers to a process of slowly introducing fluid to a tissue site and leaving the fluid for a prescribed period of time before removing the fluid. For example, instillation of topical treatment solutions over a wound bed can be combined with negative-pressure therapy to further promote wound healing by loosening soluble contaminants in a wound bed and removing infectious material. As a result, soluble bacterial burden can be decreased, contaminants removed, and the wound cleansed.

[0005] While the clinical benefits of negative-pressure therapy and/or instillation therapy are widely known, improvements to therapy systems, components, and processes may benefit healthcare providers and patients. BRIEF SUMMARY

[0006] New and useful systems, apparatuses, and methods for determining tissue site size in a negative-pressure therapy and instillation therapy environment are set forth in the appended claims. Illustrative embodiments are also provided to enable a person skilled in the art to make and use the claimed subject matter.

[0007] For example, in some embodiments, an accumulator positioned in-line between a canister and a therapy device is described. The accumulator can include a fluid container having a fluid chamber, a first port configured to be fluidly coupled to a pressure sensor of the therapy device, and a second port configured to be fluidly coupled to an unknown volume. The accumulator can also include a fluid passage disposed in the fluid container and fluidly isolated from the fluid chamber, a third port configured to be fluidly coupled to a negative-pressure supply of the therapy device, the third port fluidly coupled to the fluid passage, and a fourth port configured to be fluidly coupled to the unknown volume, the fourth port fluidly coupled to the fluid passage.

[0008] More generally, a system for supplying negative-pressure therapy and instillation therapy is described. The system can include a therapy unit configured to provide instillation therapy and negative-pressure therapy, the therapy unit having a pressure-sensing port, a negative-pressure supply port, and a latching mechanism. The system can also include a pressure vessel configured to store negative-pressure, the pressure vessel configured to be coupled to the therapy unit via the latching mechanism. The pressure vessel can have a fluid chamber configured to be fluidly coupled to the pressure-sensing port, and a negative-pressure bypass disposed in and fluidly isolated from the fluid chamber. The negative-pressure bypass can be configured to be fluidly coupled to the negativepressure supply port. The system can further include a fluid storage container. The fluid storage container can be configured to be fluidly coupled to the fluid chamber and the negative-pressure bypass. The fluid storage container can be further configured to be coupled to the pressure vessel.

[0009] A method of determining a size of a tissue site is also described herein, wherein some example embodiments provide a therapy system configured to provide negative-pressure therapy and instillation therapy. An accumulator can be fluidly coupled to the therapy system. A canister can be fluidly coupled to the accumulator and a dressing. Negative-pressure therapy can be provided. A solenoid valve of the therapy system can be operated to permit fluid flow from the ambient environment to the accumulator and through a filter into the system. A negative-pressure decay profile can be determined, and in response to determining a negative-pressure decay profile, the size of the tissue site can be determined.

[0010] Objectives, advantages, and a preferred mode of making and using the claimed subject matter may be understood best by reference to the accompanying drawings in conjunction with the following detailed description of illustrative embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a functional block diagram of an example embodiment of a therapy system that can provide negative-pressure treatment and instillation treatment in accordance with this specification;

[0012] Figure 2 is a perspective view of a portion of a therapy unit of Figure 1, illustrating additional details that may be associated with some embodiments of the therapy system;

[0013] Figure 3 is a side view of the therapy unit of Figure 2, illustrating additional details that may be associated with some embodiments;

[0014] Figure 4 is a perspective view of an accumulator of Figure 1, illustrating additional details that may be associated with some embodiments of the therapy system;

[0015] Figure 5 is a sectional view of the accumulator taken along line 5 — 5 of Figure 4, illustrating additional details that may be associated with some embodiments;

[0016] Figure 6 is a left side view of the accumulator of Figure 4, illustrating additional details that may be associated with some embodiments;

[0017] Figure 7 is a right side view of the accumulator of Figure 4, illustrating additional details that may be associated with some embodiments;

[0018] Figure 8 is a perspective view of a canister of Figure 1, illustrating additional details that may be associated with some embodiments of the therapy system;

[0019] Figure 9 is a sectional view of the canister taken along line 9 — 9 of Figure 8, illustrating additional details that may be associated with some embodiments; and

[0020] Figure 10 is a left side view of the accumulator of Figure 8, illustrating additional details that may be associated with some embodiments.

DESCRIPTION OF EXAMPLE EMBODIMENTS

[0021] The following description of example embodiments provides information that enables a person skilled in the art to make and use the subject matter set forth in the appended claims, but it may omit certain details already well-known in the art. The following detailed description is, therefore, to be taken as illustrative and not limiting.

[0022] The example embodiments may also be described herein with reference to spatial relationships between various elements or to the spatial orientation of various elements depicted in the attached drawings. In general, such relationships or orientation assume a frame of reference consistent with or relative to a patient in a position to receive treatment. However, as should be recognized by those skilled in the art, this frame of reference is merely a descriptive expedient rather than a strict prescription.

[0023] The term “tissue site” in this context broadly refers to a wound, defect, or other treatment target located on or within tissue, including but not limited to, a surface wound, bone tissue, adipose tissue, muscle tissue, neural tissue, dermal tissue, vascular tissue, connective tissue, cartilage, tendons, or ligaments. The term “tissue site” may also refer to areas of any tissue that are not necessarily wounded or defective, but are instead areas in which it may be desirable to add or promote the growth of additional tissue. For example, negative pressure may be applied to a tissue site to grow additional tissue that may be harvested and transplanted. A surface wound, as used herein, is a wound on the surface of a body that is exposed to the outer surface of the body, such as injury or damage to the epidermis, dermis, and/or subcutaneous layers. Surface wounds may include ulcers or closed incisions, for example. A surface wound, as used herein, does not include wounds within an intraabdominal cavity. A wound may include chronic, acute, traumatic, subacute, and dehisced wounds, partial-thickness bums, ulcers (such as diabetic, pressure, or venous insufficiency ulcers), flaps, and grafts, for example.

[0024] Figure 1 is a simplified functional block diagram of an example embodiment of a therapy system 100 that can provide negative -pressure therapy with instillation of topical treatment solutions to a tissue site in accordance with this specification. The therapy system 100 may include a source or supply of negative pressure, such as a negative -pressure source 102, a dressing 104, a fluid container, such as a canister 106, and a regulator or controller, such as a controller 108, for example. In some embodiments, a pressure vessel, such as an accumulator 126, can be fluidly coupled to the canister 106. Additionally, the therapy system 100 may include sensors to measure operating parameters and provide feedback signals to the controller 108 indicative of the operating parameters. As illustrated in Figure 1, for example, the therapy system 100 may include a pressure sensor 110, an electric sensor 112, or both, coupled to the controller 108. A three-way valve 128 may also be fluidly coupled to the pressure sensor 110, the accumulator 126, and the ambient environment 130 and coupled to the controller 108. As illustrated in the example of Figure 1, the dressing 104 may comprise or consist essentially of a tissue interface 114, a cover 116, or both in some embodiments.

[0025] The therapy system 100 may also include a source of instillation solution. For example, a fluid source 118 may be fluidly coupled to the dressing 104, as illustrated in the example embodiment of Figure 1. The fluid source 118 may be fluidly coupled to a positive-pressure source such as the positive-pressure source 120, a negative-pressure source such as the negative-pressure source 102, or both in some embodiments. A regulator, such as an instillation regulator 122, may also be fluidly coupled to the fluid source 118 and the dressing 104 to ensure proper dosage of instillation solution (e.g. saline or sterile water) to a tissue site. For example, the instillation regulator 122 may comprise a piston that can be pneumatically actuated by the negative-pressure source 102 to draw instillation solution from the fluid source 118 during a negative-pressure interval and to instill the solution to a dressing during a venting interval. Additionally or alternatively, the controller 108 may be coupled to the negative-pressure source 102, the positive-pressure source 120, or both, to control dosage of instillation solution to a tissue site. In some embodiments, the instillation regulator 122 may also be fluidly coupled to the negative -pressure source 102 through the dressing 104, as illustrated in the example of Figure 1. [0026] Some components of the therapy system 100 may be housed within or used in conjunction with other components, such as sensors, processing units, alarm indicators, memory, databases, software, display devices, or user interfaces that further facilitate therapy. For example, in some embodiments, the negative-pressure source 102 may be combined with the fluid source 118, the controller 108, and other components into a therapy unit 124.

[0027] In general, components of the therapy system 100 may be coupled directly or indirectly. For example, the negative-pressure source 102 may be directly coupled to the canister 106, and may be indirectly coupled to the dressing 104 through the canister 106. Coupling may include fluid, mechanical, thermal, electrical, or chemical coupling (such as a chemical bond), or some combination of coupling in some contexts. For example, the negative-pressure source 102 may be electrically coupled to the controller 108, and may be fluidly coupled to one or more distribution components to provide a fluid path to a tissue site. In some embodiments, components may also be coupled by virtue of physical proximity, being integral to a single structure, or being formed from the same piece of material. For example, the tissue interface 114 and the cover 116 may be discrete layers disposed adjacent to each other, and may be joined together in some embodiments.

[0028] A distribution component is preferably detachable, and may be disposable, reusable, or recyclable. The dressing 104 and the canister 106 are illustrative of distribution components. A fluid conductor is another illustrative example of a distribution component. A "fluid conductor," in this context, broadly includes a tube, pipe, hose, conduit, or other structure with one or more lumina or open pathways adapted to convey a fluid between two ends. Typically, a tube is an elongated, cylindrical structure with some flexibility, but the geometry and rigidity may vary. Moreover, some fluid conductors may be molded into or otherwise integrally combined with other components. Distribution components may also include or comprise interfaces or fluid ports to facilitate coupling and de-coupling other components. In some embodiments, for example, a dressing interface may facilitate coupling a fluid conductor to the dressing 104.

[0029] A negative-pressure supply, such as the negative-pressure source 102, may be a reservoir of air at a negative pressure, or may be a manual or electrically-powered device, such as a vacuum pump, a suction pump, a wall suction port available at many healthcare facilities, or a micropump, for example. “Negative pressure” generally refers to a pressure less than a local ambient pressure, such as the ambient pressure in a local environment external to a sealed therapeutic environment. In many cases, the local ambient pressure may also be the atmospheric pressure at which a tissue site is located. Alternatively, the pressure may be less than a hydrostatic pressure associated with tissue at the tissue site. Unless otherwise indicated, values of pressure stated herein are gauge pressures. References to increases in negative pressure typically refer to a decrease in absolute pressure, while decreases in negative pressure typically refer to an increase in absolute pressure. While the amount and nature of negative pressure applied to a tissue site may vary according to therapeutic requirements, the pressure is generally a low vacuum, also commonly referred to as a rough vacuum, between -5 mm Hg (-667 Pa) and -500 mm Hg (-66.7 kPa). Common therapeutic ranges are between -50 mm Hg (-6.7 kPa) and -300 mm Hg (-39.9 kPa).

[0030] The canister 106 is representative of a container, canister, pouch, or other storage component, which can be used to manage exudates and other fluids withdrawn from a tissue site. In many environments, a rigid container may be preferred or required for collecting, storing, and disposing of fluids. In other environments, fluids may be properly disposed of without rigid container storage, and a re-usable container could reduce waste and costs associated with negative-pressure therapy.

[0031] A controller, such as the controller 108, may be a microprocessor or computer programmed to operate one or more components of the therapy system 100, such as the negativepressure source 102. In some embodiments, for example, the controller 108 may be a microcontroller, which generally comprises an integrated circuit containing a processor core and a memory programmed to directly or indirectly control one or more operating parameters of the therapy system 100. Operating parameters may include the power applied to the negative-pressure source 102, the pressure generated by the negative-pressure source 102, or the pressure distributed to the tissue interface 114, for example. The controller 108 is also preferably configured to receive one or more input signals, such as a feedback signal, and programmed to modify one or more operating parameters based on the input signals.

[0032] Sensors, such as the pressure sensor 110 or the electric sensor 112, are generally known in the art as any apparatus operable to detect or measure a physical phenomenon or property, and generally provide a signal indicative of the phenomenon or property that is detected or measured. For example, the pressure sensor 110 and the electric sensor 112 may be configured to measure one or more operating parameters of the therapy system 100. In some embodiments, the pressure sensor 110 may be a transducer configured to measure pressure in a pneumatic pathway and convert the measurement to a signal indicative of the pressure measured. In some embodiments, the pressure sensor 110 may be a piezoresistive strain gauge. The electric sensor 112 may optionally measure operating parameters of the negative-pressure source 102, such as the voltage or current, in some embodiments. Preferably, the signals from the pressure sensor 110 and the electric sensor 112 are suitable as an input signal to the controller 108, but some signal conditioning may be appropriate. For example, the signal may need to be filtered or amplified before it can be processed by the controller 108. Typically, the signal is an electrical signal, but may be represented in other forms, such as an optical signal.

[0033] A three-way valve, such as the three-way valve 128, can be a device configured to regulate, control, or direct fluid flow. In some embodiments, the three-way valve 128 can have various passageways that can be selected to direct fluid flow between three ports. A three-way valve can be manually, pneumatically, hydraulically, or electrically actuated. For example, a three-way valve can be coupled to a solenoid. The solenoid can, in response to an input control signal, operate a gate or other valve body to direct fluid flow from a first path through the valve to a second path through the valve. For example, a three-way valve can have a first port fluidly coupled to a tissue site, a second port fluidly coupled to the ambient environment, and a third port fluidly coupled to a negative-pressure source. The solenoid can be actuated to connect the first port to the second port or the first port to the third port. In some embodiments, the solenoid can be communicatively coupled to the controller 108 and can receive one or more signals from the controller 108 and actuate the three- way valve 128 in response.

[0034] The tissue interface 114 can be generally adapted to partially or fully contact a tissue site. The tissue interface 114 may take many forms, and may have many sizes, shapes, or thicknesses depending on a variety of factors, such as the type of treatment being implemented or the nature and size of a tissue site. For example, the size and shape of the tissue interface 114 may be adapted to the contours of deep and irregular shaped tissue sites.

[0035] In some embodiments, the tissue interface 114 may comprise or consist essentially of a manifold. A manifold in this context may comprise or consist essentially of a means for collecting or distributing fluid across the tissue interface 114 under pressure. For example, a manifold may be adapted to receive negative pressure from a source and distribute negative pressure through multiple apertures across the tissue interface 114, which may have the effect of collecting fluid from across a tissue site and drawing the fluid toward the source. In some embodiments, the fluid path may be reversed or a secondary fluid path may be provided to facilitate delivering fluid, such as fluid from a source of instillation solution, across a tissue site.

[0036] In some illustrative embodiments, a manifold may comprise a plurality of pathways, which can be interconnected to improve distribution or collection of fluids. In some illustrative embodiments, a manifold may comprise or consist essentially of a porous material having interconnected fluid pathways. Examples of suitable porous material that can be adapted to form interconnected fluid pathways (e.g., channels) may include cellular foam, including open-cell foam such as reticulated foam; porous tissue collections; and other porous material such as gauze or felted mat that generally include pores, edges, and/or walls. Liquids, gels, and other foams may also include or be cured to include apertures and fluid pathways. In some embodiments, a manifold may additionally or alternatively comprise projections that form interconnected fluid pathways. For example, a manifold may be molded to provide surface projections that define interconnected fluid pathways.

[0037] In some embodiments, the tissue interface 114 may comprise or consist essentially of reticulated foam having pore sizes and free volume that may vary according to needs of a prescribed therapy. For example, reticulated foam having a free volume of at least 90% may be suitable for many therapy applications, and foam having an average pore size in a range of 400-600 microns (40- 50 pores per inch) may be particularly suitable for some types of therapy. The tensile strength of the tissue interface 114 may also vary according to needs of a prescribed therapy. For example, the tensile strength of foam may be increased for instillation of topical treatment solutions. The 25% compression load deflection of the tissue interface 114 may be at least 0.35 pounds per square inch, and the 65% compression load deflection may be at least 0.43 pounds per square inch. In some embodiments, the tensile strength of the tissue interface 114 may be at least 10 pounds per square inch. The tissue interface 114 may have a tear strength of at least 2.5 pounds per inch. In some embodiments, the tissue interface may be foam comprised of polyols such as polyester or polyether, isocyanate such as toluene diisocyanate, and polymerization modifiers such as amines and tin compounds. In some examples, the tissue interface 114 may be reticulated polyurethane foam such as found in GRANUFOAM™ dressing or V.A.C. VERAFLO™ dressing, both available from Kinetic Concepts, Inc. of San Antonio, Texas.

[0038] The thickness of the tissue interface 114 may also vary according to needs of a prescribed therapy. For example, the thickness of the tissue interface may be decreased to reduce tension on peripheral tissue. The thickness of the tissue interface 114 can also affect the conformability of the tissue interface 114. In some embodiments, a thickness in a range of about 5 millimeters to 10 millimeters may be suitable.

[0039] The tissue interface 114 may be either hydrophobic or hydrophilic. In an example in which the tissue interface 114 may be hydrophilic, the tissue interface 114 may also wick fluid away from a tissue site, while continuing to distribute negative pressure to the tissue site. The wicking properties of the tissue interface 114 may draw fluid away from a tissue site by capillary flow or other wicking mechanisms. An example of a hydrophilic material that may be suitable is a polyvinyl alcohol, open-cell foam such as V.A.C. WHITEFOAM™ dressing available from Kinetic Concepts, Inc. of San Antonio, Texas. Other hydrophilic foams may include those made from polyether. Other foams that may exhibit hydrophilic characteristics include hydrophobic foams that have been treated or coated to provide hydrophilicity.

[0040] In some embodiments, the tissue interface 114 may be constructed from bioresorbable materials. Suitable bioresorbable materials may include, without limitation, a polymeric blend of polylactic acid (PLA) and polyglycolic acid (PGA). The polymeric blend may also include, without limitation, polycarbonates, polyfumarates, and capralactones. The tissue interface 114 may further serve as a scaffold for new cell -growth, or a scaffold material may be used in conjunction with the tissue interface 114 to promote cell-growth. A scaffold is generally a substance or structure used to enhance or promote the growth of cells or formation of tissue, such as a three-dimensional porous structure that provides a template for cell growth. Illustrative examples of scaffold materials include calcium phosphate, collagen, PLA/PGA, coral hydroxy apatites, carbonates, or processed allograft materials.

[0041] In some embodiments, the cover 116 may provide a bacterial barrier and protection from physical trauma. The cover 116 may also be constructed from a material that can reduce evaporative losses and provide a fluid seal between two components or two environments, such as between a therapeutic environment and a local external environment. The cover 116 may be, for example, an elastomeric film or membrane that can provide a seal adequate to maintain a negative pressure at a tissue site for a given negative-pressure source. The cover 116 may have a high moisture-vapor transmission rate (MVTR) in some applications. For example, the MVTR may be at least about 300 g/m² per twenty-four hours in some embodiments. In some example embodiments, the cover 116 may be a polymer drape, such as a polyurethane film, that is permeable to water vapor but impermeable to liquid. Such drapes typically have a thickness in the range of about 25 microns to about 50 microns. For permeable materials, the permeability generally should be low enough that a desired negative pressure may be maintained.

[0042] The cover 116 may comprise, for example, one or more of the following materials: hydrophilic polyurethane; cellulosics; hydrophilic polyamides; polyvinyl alcohol; polyvinyl pyrrolidone; hydrophilic acrylics; hydrophilic silicone elastomers; an INSPIRE 2301 material from Coveris Advanced Coatings of Wrexham, United Kingdom having, for example, an MVTR (inverted cup technique) of about 14400 g/m²/24 hours and a thickness of about 30 microns; a thin, uncoated polymer drape; natural rubbers; polyisoprene; styrene butadiene rubber; chloroprene rubber; polybutadiene; nitrile rubber; butyl rubber; ethylene propylene rubber; ethylene propylene diene monomer; chlorosulfonated polyethylene; polysulfide rubber; polyurethane (PU); EVA film; copolyester; silicones; a silicone drape; a 3M Tegaderm® drape; a polyurethane (PU) drape such as one available from Avery Dennison Corporation of Glendale, California; polyether block polyamide copolymer (PEBAX), for example, from Arkema, France; INSPIRE 2327; or other appropriate material.

[0043] An attachment device may be used to attach the cover 116 to an attachment surface, such as undamaged epidermis, a gasket, or another cover. The attachment device may take many forms. For example, an attachment device may be a medically-acceptable, pressure-sensitive adhesive configured to bond the cover 116 to epidermis around a tissue site. In some embodiments, for example, some or all of the cover 116 may be coated with an adhesive, such as an acrylic adhesive, which may have a coating weight between about 25 grams per square meter (g.s.m.) and about 65 g.s.m. Thicker adhesives, or combinations of adhesives, may be applied in some embodiments to improve the seal and reduce leaks. Other example embodiments of an attachment device may include a double-sided tape, paste, hydrocolloid, hydrogel, silicone gel, or organ gel.

[0044] The fluid source 118 may also be representative of a container, canister, pouch, bag, or other storage component, which can provide a solution for instillation therapy. Compositions of solutions may vary according to a prescribed therapy, but examples of solutions that may be suitable for some prescriptions include hypochlorite-based solutions, silver nitrate (0.5%), sulfur-based solutions, biguanides, cationic solutions, and isotonic solutions.

[0045] The fluid mechanics of using a negative-pressure source to reduce pressure in another component or location, such as within a sealed therapeutic environment, can be mathematically complex. However, the basic principles of fluid mechanics applicable to negative-pressure therapy and instillation are generally well-known to those skilled in the art, and the process of reducing pressure may be described illustratively herein as “delivering,” “distributing,” or “generating” negative pressure, for example.

[0046] In general, exudates and other fluids flow toward lower pressure along a fluid path. Thus, the term “downstream” typically implies a position in a fluid path relatively closer to a source of negative pressure or further away from a source of positive pressure. Conversely, the term “upstream” implies a position relatively further away from a source of negative pressure or closer to a source of positive pressure. Similarly, it may be convenient to describe certain features in terms of fluid “inlet” or “outlet” in such a frame of reference. This orientation is generally presumed for purposes of describing various features and components herein. However, the fluid path may also be reversed in some applications (such as by substituting a positive-pressure source for a negativepressure source) and this descriptive convention should not be construed as a limiting convention.

[0047] Negative pressure applied across the tissue site through the tissue interface 114 in the sealed therapeutic environment can induce macro-strain and micro-strain in the tissue site. Negative pressure can also remove exudate and other fluid from a tissue site, which can be collected in canister 106.

[0048] In some embodiments, the controller 108 may receive and process data from one or more sensors, such as the pressure sensor 110 and the electric sensor 112. The controller 108 may also control the operation of one or more components of the therapy system 100 to manage the pressure delivered to the tissue interface 114. In some embodiments, controller 108 may include an input for receiving a desired target pressure and may be programmed for processing data relating to the setting and inputting of the target pressure to be applied to the tissue interface 114. In some example embodiments, the target pressure may be a fixed pressure value set by an operator as the target negative pressure desired for therapy at a tissue site and then provided as input to the controller 108. The target pressure may vary from tissue site to tissue site based on the type of tissue forming a tissue site, the type of injury or wound (if any), the medical condition of the patient, and the preference of the attending physician. After selecting a desired target pressure, the controller 108 can operate the negative-pressure source 102 in one or more control modes based on the target pressure and may receive feedback from one or more sensors to maintain the target pressure at the tissue interface 114.

[0049] Some therapy systems providing negative-pressure therapy and instillation therapy can determine a size of a tissue site prior to instilling fluid to the tissue site. For example, a therapy system may determine a size of a tissue site by determining a volume of a tissue site. Knowing the volume of the tissue site can allow a therapy system to instill a volume of fluid to a tissue site that is less than the volume of the tissue site. In this manner, complications caused by overfilling the tissue site can be avoided. For example, if the volume of fluid instilled to the tissue site is less than the volume of the tissue site, the risk that the seal between the cover 116 and the tissue site may be broken is reduced. In some therapy systems, the size of the tissue site can be determined by monitoring a change in negative pressure at the tissue site for a predetermined interval. For example, negativepressure therapy can be provided by developing a negative pressure at a tissue site. A sensing system can monitor a pressure at the tissue site and signal to the therapy system that the pressure at the tissue site has reached a target negative pressure. At the conclusion of a negative-pressure interval, the therapy system may vent the negative pressure to the atmosphere for a pre-determined period of time. For example, the therapy system may have a solenoid valve providing a fluid coupling between the therapy system and the ambient environment. The therapy system may operate the solenoid valve, to permit fluid flow from the atmosphere to the tissue site. The sensing system of the therapy system can monitor the rate of change of the pressure at the tissue site to determine a decay profde for the tissue site. The decay profde can be a signal representing the decrease in negative pressure at the tissue site for the given time interval. Generally, for larger tissue sites, the decay profde may be flatter, and for smaller tissue sites, the decay profde may be sharper. The decay profde can be compared to one or more expected decay profdes associated with tissue sites of various sizes to determine an approximate size of the tissue site.

[0050] For some therapy systems, variations in the manufacturing processes of the components of the therapy system can impact the accuracy of the tissue site size determination process. For example, unexpected flow restrictions in the therapy system may cause the profde of the determined decay profde can cause the decay profde to deviate from the actual decay profde for the tissue site. A flow restriction can include an obstruction in a fluid conductor or variation in the construction of a canister fdter disposed between the canister and the negative-pressure source or between the canister and a pressure sensor, for example. For a canister fdter, variation between purchased fdter lots can impact fluid flow across the fdter, leading to decay profde variation. For example, the fdter may have more or less free volume than expected for the passage of fluid. As a result, the differences in decay profdes may not be attributable to different tissue sites and can cause the therapy system to inaccurately estimate the tissue site size. Tissue sites having a smaller volume may be more prone to errors in the size determination than larger tissue sites. For tissue sites that are smaller than 100 cubic centimeters (cc) the impact of such manufacturing variation can be acute.

[0051] These limitations and others may be addressed by the therapy system 100, which can provide negative-pressure therapy, instillation therapy, and determination of tissue site size. In some embodiments, the therapy system 100 can provide accurate tissue site size determination over a wider range of variables. A pressure drop through a fdter can be managed to introduce consistent known volumes of fluid into a closed pressure measuring system. By managing the pressure drop, a total system volume comprising known and unknown volumes can be determined using Darcy’s Law. The known system volumes in the total system volume can be subtracted from the total system volume to determine the unknown system volumes. A disposable fdter through which the introduced fluid is passed can be connected so that there may be very little fluid volume between a valve used to control the introduced fluid and the filter, the filter will introduce inconsistent volumes because of variations in pressure drop from lot to lot of the filter material. An accumulator, such as the accumulator 126, can collect a consistent known volume of fluid prior to the fluid reaching the filter. Once the fluid is collected and an input valve is closed the system can stabilize with a new pressure as the air moves through the filter at the various flowrates created from the varying filter media pressure drop.

[0052] For example, the therapy system 100 can accommodate for variation between filter lots that may be used in canister production, leading to improved fluid use during instillation cycles. In particular, the therapy system 100 may accurately estimate tissue site size for tissue sites having a volume of 100 cc or less. In some embodiments, the accumulator 126 can be fluidly coupled between the three-way valve 128 and the canister 106. Fluid can be drawn from the accumulator 126 to create a reservoir of negative pressure between a filter of the canister 106 and the three-way valve 128. The reservoir of negative pressure held by the accumulator 126 can smooth fluid flow during the venting step of the tissue site size determination process. By smoothing flow, the therapy system 100 can more accurately determine the tissue site size despite variations that may occur during manufacturing.

[0053] Figure 2 is a perspective view of the therapy unit 124 of Figure 1, illustrating additional details that may be associated with some embodiments of the therapy system 100. The therapy unit 124 can include the negative-pressure source 102, the controller 108, the pressure sensor 110, the electric sensor 112, the positive-pressure source 120, and the instillation regulator 122. For example, the therapy unit 124 may have a housing 202 having an interior into which the negativepressure source 102, the controller 108, the pressure sensor 110, the electric sensor 112, the positivepressure source 120, and the instillation regulator 122 can be disposed. In some embodiments, the housing 202 can have one or more inputs or user interfaces 204. The user interfaces 204 can be disposed in or coupled to the housing 202. For example, the therapy unit 124 can have at least a graphical user interface, a power button, and a start/pause button as user interfaces 204. The user interfaces 204 may be communicatively coupled to the controller 108. For example, the user interfaces 204 may be capable of generating and transmitting signals to the controller 108. In some embodiments, the user interfaces 204 can permit a user to interact with the therapy system 100 by powering on the therapy system 100, starting or stopping therapy, selecting one or more parameters of a therapy to be provided by the therapy system 100, and/or displaying one or more operating states of the therapy system 100. The user interfaces 204 may permit input a desired target pressure, the type of tissue forming a tissue site, the type of injury or wound (if any), the medical condition of the patient, and any preferences of the attending physician. The user interfaces 204 can also permit selection of the control modes for the negative-pressure source 102 and the fluid source 118. Still further, the user interfaces 204 can display feedback from one or more sensors, such as the pressure sensor 110 and the electric sensor 112, of the therapy system 100.

[0054] The canister 106, the fluid source 118, and the accumulator 126 can be coupled to the therapy unit 124. In some embodiments, the canister 106, the fluid source 118, and/or the accumulator 126 can be removably coupled to therapy unit 124. For example, the housing 202 can have a mount 206. The mount 206 may be a physical component of the housing 202 permitting one or more component modules to be physically attached to the housing 202. In some embodiments, the mount 206 may provide one or more couplings for interaction between a component module, such as the accumulator 126 or the canister 106 and other components of the therapy unit 124. In some embodiments, the mount 206 may comprise a side of the housing 202. The mount 206 may be configured to receive one or more of the accumulator 126 and the canister 106. In some embodiments, the housing 202 can include a mount on an opposite side of the housing 202 from the mount 206 that is configured to receive the fluid source 118. In other embodiments, the canister 106, the fluid source 118, and/or the accumulator 126 can be permanently coupled to therapy unit 124.

[0055] In some embodiments, the mount 206 can comprise a cavity or recess depending into the housing 202. For example, the housing 202 may have a wall 208 forming a side of the therapy unit 124. An opening 210 can be formed in the wall 208. In some embodiments, the opening 210 can be circular or elliptical. In other embodiments, the opening 210 can have other shapes, for example, a polygonal, a triangular, or an amorphous shape. An annular wall 212 can depend into the housing 202 from the wall 208. In some embodiments, the annular wall 212 can be coincident with the opening 210. In other embodiments, the annular wall 212 can be offset from the opening 210. If the annular wall 212 is offset from the opening 210, the annular wall 212 may have a radius of curvature that is greater than the radius of the opening 210, allowing the wall 208 to form a lip protruding past the annular wall 212. In some embodiments, a first end of the annular wall 212 can be coupled to the wall 208 at the opening 210. An opposite end or second end of the annular wall 212 can be coupled to a cavity wall 214. The cavity wall 214 can extend across the opening 210. In some embodiments, the cavity wall 214 can form a barrier to access to the interior of the housing 202. The mount 206 can also include one or more couplers 216. In some embodiments, the couplers 216 can be secured to the cavity wall 214. The couplers 216 can provide one or more contact points between the therapy unit 124 and components, such as the accumulator 126 or the canister 106. In some embodiments, the couplers 216 may physically secure components to the therapy unit 124. The couplers 216 may also provide a communicative coupling, such as an electrical or fluid connection across the cavity wall 214.

[0056] Figure 3 is a side view of the therapy unit 124 of Figure 2, illustrating additional details that may be associated with some embodiments. The couplers 216 can include a latch 302, a negative-pressure port 306, and a pressure-sensing port 304. In some embodiments, the latch 302 can be a mechanical fastener configured to releasably couple to a mating element on another component. For example, the latch 302 may be configured to releasably couple to a mating element on the accumulator 126 or the canister 106. In some embodiments, the latching mechanism may align the accumulator 126 with the therapy unit 124 to create a hermetic seal between the accumulator 126 and the canister 106 and align the negative-pressure port 306 and the pressure-sensing port 304 with counterpart ports.

[0057] The negative-pressure port 306 can be fluidly coupled to the negative -pressure source 102 and be configured to be fluidly coupled to another component, such as the accumulator 126 or the canister 106. In some embodiments, the negative-pressure port 306 can be a cylindrical component. The negative-pressure port 306 can include a fluid passage 314 passing through a center of the negative-pressure port 306. The fluid passage 314 can be fluidly coupled to the negative-pressure source 102. In some embodiments, the fluid passage 314 can be a fluid conductor, such as a tube or conduit having one or more lumens. The negative-pressure port 306 can also include a supply tube seal or grommet 312 surrounding the fluid passage 314. The grommet 312 can comprise an apparatus formed from a flexible or pliable material. The grommet 312 may be configured to provide a seal between the cavity wall 214, the fluid passage 314 and a component module being coupled to the fluid passage 314, such as the accumulator 126 or the canister 106. In some embodiments, the grommet 312 may be a bellows type grommet having a concertinaed annular wall configured to provide some movement along an axis that is parallel to an axis of the fluid passage 314.

[0058] Similarly, the pressure-sensing port 304 can be fluidly coupled to sensor, such as the pressure sensor 110 and be configured to be fluidly coupled to another component, such as the accumulator 126 or the canister 106. The pressure-sensing port 304 can be a cylindrical body and include a fluid passage 308 passing through a center of the pressure-sensing port 304. The fluid passage 308 can be fluidly coupled to the pressure sensor 110. In some embodiments, the fluid passage 308 can be a fluid conductor, such as a tube or conduit having one or more lumens. The pressure-sensing port 304 can also include a sensing tube seal or grommet 310 surrounding the fluid passage 308. The grommet 310 can comprise an apparatus formed from a flexible or pliable material. The grommet 310 may be configured to provide a seal between the cavity wall 214, the fluid passage 308 and a component module being coupled to the fluid passage 308. In some embodiments, the grommet 310 may be a bellows type grommet having a concertinaed annular wall configured to provide some movement along an axis that is parallel to an axis of the fluid passage 308.

[0059] Figure 4 is a perspective view of the accumulator 126, illustrating additional details that may be associated with some embodiments of the therapy system 100. The accumulator 126 may include a latch 402, a first port, such as a canister port or a negative-pressure port 406, and a second port, such as a pressure-sensing port 404. In some embodiments, the latch 402 can be a mechanical fastener configured to releasably couple to a mating element on another component. For example, the latch 402 may be configured to releasably couple to a mating element on the canister 106. In some embodiments, the latch 402 may be a square shaped projection from the first wall 416. The latch 402 may include one or more mechanical components configured to engage one or more mating elements on a corresponding component. In some embodiments, the latch 402 may align the canister 106 with the accumulator 126 to create a hermetic seal between the accumulator 126 and the canister 106 and align the negative-pressure port 406 and the pressure-sensing port 404 with counterpart ports.

[0060] The negative-pressure port 406 can be configured to be fluidly coupled to the negative-pressure source 102 and be configured to be fluidly coupled to another component, such as the canister 106. The negative-pressure port 406 can be a cylindrical body and include a fluid passage 412 passing through a center of the negative-pressure port 406. The fluid passage 412 may be fluidly isolated from an interior of the accumulator 126. The negative-pressure port 406 can also include a negative-pressure bypass tube seal or grommet 414 surrounding the fluid passage 412. The grommet 414 can comprise an apparatus formed from a flexible or pliable material. The grommet 414 may be configured to provide a seal between the fluid passage 412 and a component module being coupled to the fluid passage 412. In some embodiments, the grommet 414 may be a bellows type grommet having a concertinaed annular wall configured to provide some movement along an axis that is parallel to an axis of the fluid passage 412.

[0061] Similarly, the pressure-sensing port 404 can be configured to be fluidly coupled to sensor, such as the pressure sensor 110 and be configured to be fluidly coupled to another component, such as the canister 106. The pressure -sensing port 404 can be a cylindrical body and include a fluid passage 408 passing through a center of the pressure -sensing port 404. The fluid passage 408 can be fluidly coupled to interior of the accumulator 126. The pressure-sensing port 404 can also include a sensing bypass tube seal or grommet 410 surrounding the fluid passage 408. The grommet 410 can comprise an apparatus formed from a flexible or pliable material. The grommet 410 may surround the fluid passage 408 and be configured to provide a seal between the cavity wall 214, the fluid passage 408 and a component module being coupled to the fluid passage 408. In some embodiments, the grommet 410 may be a bellows type grommet having a concertinaed annular wall configured to provide some movement along an axis that is parallel to an axis of the fluid passage 408.

[0062] The accumulator 126 can include a first wall 416 and an annular wall 418. In some embodiments, the first wall 416 can be elliptical or oval-shaped. In other embodiments, the first wall 416 can have other shapes, such as polygonal, triangular, or amorphous. The annular wall 418 can be coupled to the first wall 416. In some embodiments, the annular wall 418 can be coupled to a perimeter of the first wall 416. The annular wall 418 may have a first end coupled to the first wall 416 and a second end opposite the first end. The latch 402, the negative -pressure port 406, and the pressure-sensing port 404 can all be disposed on the first wall 416. In some embodiments, the negative-pressure port 406 and the pressure -sensing port 404 can provide fluid communication across the first wall 416. In some embodiments, if the accumulator 126 is coupled to the therapy unit 124, the negative-pressure port 406, the pressure -sensing port 404, and the latch 402 reflect the locations of the latch 302, the negative-pressure port 306, and the pressure-sensing port 304 of the therapy unit 124. [0063] Figure 5 is a sectional view of the accumulator 126 taken along line 5 — 5 of Figure 4; Figure 6 is a left side view of the accumulator 126, and Figure 7 is a right side view of the accumulator 126, illustrating additional details that may be associated with some embodiments. The accumulator 126 can include a second wall 502. The second wall 502 can be coupled to the second end of the annular wall 418. In some embodiments, the second wall 502 may be opposite the first wall 416. The first wall 416 and the second wall 502 may have a similar shape. The second wall 502 may be elliptical or oval-shaped. In other embodiments, the second wall 502 may be polygonal, triangular, or amorphous. The first wall 416, the second wall 502, and the annular wall 418 may form a housing that defines a chamber 504. In some embodiments, the chamber 504 may be a space fluidly isolated from the ambient environment. In some embodiments, the chamber 504 may have a volume of up to about 100 cubic centimeters (cc).

[0064] The second wall 502 may have a port or a first opening 506 and another port or a second opening 508. The first opening 506 may be fluidly coupled to the chamber 504. The first opening 506 may permit fluid communication with the chamber 504 across the second wall 502. The first opening 506 may be disposed in the second wall 502 so that, if the accumulator 126 is coupled to the therapy unit 124, the first opening 506 may be adjacent to the pressure-sensing port 304. The fluid passage 408 may be fluidly coupled to the chamber 504. The fluid passage 408 may permit fluid communication with the chamber 504 across the first wall 416.

[0065] The second opening 508 may be coupled to a fluid passage, for example, a lumen 510. The second opening 508 may permit fluid communication across the second wall 502 with the lumen 510. The second opening 508 may be disposed in the second wall 502 so that, if the accumulator 126 is coupled to the therapy unit 124, the second opening 508 may be adjacent to the negative pressure port 306. The lumen 510 may fluidly couple the second opening 508 to the fluid passage 412 of the pressure-sensing port 406. In some embodiments, the lumen 510 may be fluidly isolated from the chamber 504 and operate as a negative-pressure bypass. For example, the lumen 510 may not be in fluid communication with the chamber 504, permitting an apparatus fluidly coupled to negative-pressure port 406 to be fluidly coupled to the second opening 508 through the accumulator 126 without being in fluid communication with the chamber 504 of the accumulator 126.

[0066] The second wall 502 may also include a receiver 512. The receiver 512 may be configured to be releaseably coupled to the latch 302. For example, the receiver 512 may be configured to receive the latch 302 and physically couple the second wall of the accumulator 126 to the cavity wall 214 of the therapy unit 124. In some embodiments, the receiver 512 may be positioned to permit the second wall 502 to be positioned adjacent to the cavity wall 214 of the therapy unit 124. The receiver 512 may be a square-shaped cavity disposed in the second wall 502. In some embodiments, the receiver 512 may include one or more elements configured to engage the latch 302 to secure the receiver 512 to the latch 302. [0067] Figure 8 is a perspective view of the canister 106, illustrating additional details that may be associated with some embodiments of the therapy system 100. The canister 106 can have a housing 802, a fluid port 804, and a fluid conductor 806. The housing 802 can define a fluid chamber configured to receive fluid. The fluid port 804 can be a device configured to permit fluid communication with the fluid chamber of the housing 802. The fluid conductor 806 can be a tube or other device permitting the fluid port 804 to be fluidly coupled to another device, such as the dressing 104 for fluid communication between the canister 106 and the dressing 104. In some embodiments, the fluid conductor 806 can be a single lumen conduit providing fluid communication between the dressing 104 and the fluid chamber of the canister 106. In other embodiments, the fluid conductor 806 can be a multi-lumen conduit having a primary lumen configured to draw fluid from a sealed therapeutic environment provided by the dressing 104 and one or more secondary lumens configured to communicate a pressure from the sealed therapeutic environment provided by the dressing 104.

[0068] Figure 9 is a sectional view of the canister 106 taken along line 9 — 9 of Figure 8, and Figure 10 is a left side view of the canister 106 of Figure 8, illustrating additional details that may be associated with some embodiments. The housing 802 defines a chamber 902. In some embodiments, the housing 802 may have a substantially planar wall, an annular wall coupled to the planar wall, and a domed wall coupled to an opposite end of the annular wall. In other embodiments, the housing 802 may have other shapes and wall configurations. The housing 802 also includes a receiver 904, a first opening 908, and a second opening 906. The receiver 904 can be configured to be coupled to the latch 402. The receiver 904 may be configured to be releaseably coupled to the latch 402. For example, the receiver 904 may be configured to receive the latch 402 and physically couple the housing 802 of the canister 106 to the first wall 416 of the accumulator 126. In some embodiments, the receiver 904 may be positioned to permit the housing 802 to be positioned adjacent to the first wall 416 of the accumulator 126. The receiver 904 may be a square-shaped cavity disposed in the housing 802. In some embodiments, the receiver 904 may include one or more elements configured to engage the latch 402 to secure the receiver 904 to the latch 402.

[0069] The first opening 908 can be configured to be fluidly coupled to the negative-pressure port 406. For example, the first opening 908 can be an aperture in the housing 802 positioned to be adjacent to the negative-pressure port 406 if the latch 402 is engaged with the receiver 904. The first opening 908 may permit fluid communication with the chamber 902 across the planar wall of the housing 802. The second opening 906 can be configured to be fluidly coupled to the pressure-sensing port 408. For example, the second opening 906 can be an aperture in the housing 802 positioned to be adjacent to the pressure-sensing port 408 if the latch 402 is engaged with the receiver 904. The second opening 906 may be fluidly coupled to the chamber 902. In some embodiments, the second opening 906 can be fluidly coupled to the fluid conductor 806. For example, a lumen 912 may fluidly couple the second opening 906 to the fluid conductor 806 through the chamber 902. If the lumen 912 is used to fluidly couple the second opening 906 to the fluid conductor 806, the second opening 906 is fluidly isolated from the chamber 902. Fluid isolation of the second opening 906 can permit the second opening 906 to be fluidly coupled to a device, such as the dressing 104, through the canister 106 without being in fluid communication with the chamber 902 of the canister 106. In some embodiments, the lumen 912 may be fluidly coupled to the one or more secondary lumens of the fluid conductor 806.

[0070] In some embodiments, the canister 106 can include a filter 910. The filter 910 can be disposed over the first opening 906 and the second opening 908. In some embodiments, the filter 910 can be a hydrophobic filter. The filter 910 can prevent liquid, such as exudate, from entering the first opening 906 and the second opening 908. However, the filter 910 allows the passage of gas, such as air, such that negative pressure may be transferred from the accumulator 126 through the pressuresensing port 404, the second opening 906, the lumen 912, to the dressing 104 via the one or more secondary lumens of the fluid conductor 806, and into the chamber 902 via the primary lumen of the fluid conductor 806. The filter 910 may be composed from any of a variety of materials, such as expanded polytetrafluoroethene. In some embodiments, the filter 910 may be comprised of a material that is liquid impermeable and vapor permeable. For example the filter 910 may comprise a material manufactured under the designation MMT-314 by W.L. Gore & Associates, Inc. of Newark, Delaware, United States, or similar materials. In other embodiments, the filter 910 may be, for example, a porous, sintered polymer.

[0071] During operation, the accumulator 126 can be coupled to the therapy unit 124. For example, the second wall 502 of the accumulator 126 can be positioned adjacent to the cavity wall 214 of the therapy unit 124. In some embodiments, the latch 302 can be inserted into the receiver 512. The latch 302 may engage the receiver 512, physically coupling the accumulator 126 to the therapy unit 124. In some embodiments, the chamber 504 of the accumulator 126 can be fluidly coupled to the pressure sensor 110. For example, the first opening 506 can be disposed in the second wall 502 and aligned with the receiver 512 so that the first opening 506 is adjacent to the pressuresensing port 304 if the receiver 512 is engaged with the latch 302. Fluid communication may occur between the chamber 504 and the pressure sensor 110 through the first opening 506 and the fluid passage 308 of the pressure-sensing port 304. If the latch 302 is engaged with the receiver 512, the grommet 310 can be at least partially compressed between the cavity wall 214 and the second wall 502. The compression of the grommet 310 can seal the grommet 310 to the second wall 502 around the first opening 506, permitting fluid communication between the fluid passage 308 and the first opening 506.

[0072] Similarly, in some embodiments, the second opening 508 can be fluidly coupled to the negative-pressure source 102. For example, the second opening 508 can be disposed in the second wall 502 and aligned with the receiver 512 so that the second opening 508 is adjacent to the negativepressure port 306 if the receiver 512 is engaged with the latch 302. Fluid communication may occur between the lumen 510 and negative-pressure source 102 through the second opening 508 and the fluid passage 312 of the negative-pressure port 306. If the latch 302 is engaged with the receiver 512, the grommet 314 can be at least partially compressed between the cavity wall 214 and the second wall 502. The compression of the grommet 314 can seal the grommet 314 to the second wall 502 around the second opening 508, permitting fluid communication between the fluid passage 312 and the second opening 508. The negative -pressure source 102 may be fluidly coupled to the negativepressure port 406 through the lumen 510, the second opening 508, and the fluid passage 312 of the negative-pressure port 306. Operation of the negative-pressure source 102 may draw fluid through the lumen 510, the second opening 508, and the negative-pressure port 306.

[0073] The canister 106 can be coupled to the accumulator 126. For example, the housing 802 of the canister 106 can be positioned adjacent to the first wall 416 of the accumulator 126. In some embodiments, the latch 402 can be inserted into the receiver 904. The latch 402 may engage the receiver 904, physically coupling the canister 106 to the accumulator 126. In some embodiments, the chamber 902 of the canister 106 can be fluidly coupled to the negative-pressure source 102. For example, the first opening 908 can be disposed in the housing 802 and aligned with the receiver 904 so that the first opening 908 is adjacent to the negative-pressure port 406 if the receiver 904 is engaged with the latch 402. Fluid communication may occur between the chamber 902, the first opening 908, and the fluid passage 412 of the negative-pressure port 406. If the latch 402 is engaged with the receiver 904, the grommet 414 can be at least partially compressed between the first wall 416 and the housing 802. The compression of the grommet 410 can seal the grommet 414 to the housing 802 around the first opening 908, permitting fluid communication between the fluid passage 412 and the first opening 908. Negative pressure provided to the lumen 510 may draw fluid from the chamber 902 through the first opening 908 and the negative-pressure port 406.

[0074] Similarly, in some embodiments, the second opening 906 can be fluidly coupled to chamber 504. For example, the second opening 906 can be disposed in the housing 802 and aligned with the receiver 904 to that the second opening 908 is adjacent to the pressure-sensing port 408 if the receiver 904 is engaged with the latch 402. Fluid communication may occur between the chamber 902 and pressure sensing port 404 through the second opening 906 and the fluid passage 408 of the pressure-sensing port 404. If the latch 402 is engaged with the receiver 904, the grommet 410 can be at least partially compressed between the first wall 416 and the housing 802. The compression of the grommet 410 can seal the grommet 410 to the housing 802 around the second opening 906, permitting fluid communication between the fluid passage 408 and the second opening 906. The pressure sensor 110 may be fluidly coupled to the chamber 902 through the second opening 906, the pressure-sensing port 404, the chamber 504, the second opening 506, and the fluid passage 312 of the pressure-sensing port 304

[0075] Operation of the negative-pressure source 102 may draw fluid from the lumen 510 through the first opening 508 and the fluid passage 314 of the negative-pressure port 306. Similarly, fluid may be drawn from the chamber 902 through the filter 910, the first opening 908, the fluid passage 412 of the negative-pressure port 406, and the lumen 510. As a negative-pressure is developed in the chamber 902, fluid may be drawn from a tissue site through the dressing 104 and the fluid conductor 806. For example, fluid may be drawn through the primary lumen of a multi-lumen fluid conductor 806. In some embodiments, fluid drawn from the tissue site may be stored in the chamber 902. The pressure sensor 110 may be fluidly coupled to the chamber 902 through second opening 906, the fluid passage 408 of the pressure-sensing port 404, the chamber 504, the second opening 506, and the fluid passage 308 of the pressure-sensing port 304. The pressure at the tissue site can be approximated based on the measured pressure in the chamber 902 of the canister 106. In some embodiments, for example, if the fluid conductor 806 is a multi-lumen conduit, the pressure sensor 110 may be fluidly coupled to the dressing 104 through the secondary lumens of the multilumen fluid conductor 806, the lumen 912, the second opening 906, the fluid passage 408 of the pressure-sensing port 404, the chamber 504, the second opening 506, and the fluid passage 308 of the pressure-sensing port 304. The pressure at the tissue site can be determined based on the measured pressure in the dressing 104.

[0076] Negative-pressure can be initially supplied to the dressing 104 in a draw-down cycle, where the negative-pressure source 102 can remove fluid from the sealed therapeutic environment or sealed environment provided by the dressing 104 to increase negative pressure from ambient pressure to a therapy pressure. Following the draw-down cycle, the therapy unit 124 can provide fluid in an instillation therapy cycle. In an instillation therapy cycle, fluid is provided to the sealed environment. Prior to the initiation of the instillation therapy cycle, the therapy system 100 may determine a size of the sealed environment at the tissue site to prevent over instillation of fluid. A size of a tissue site can be determined by venting the sealed environment to the atmosphere and, in response, monitoring the change in negative pressure in the sealed environment. For example, the negative-pressure source 102 can draw fluid from the tissue site through the canister 106, generating a negative pressure at the tissue site within the sealed environment covered by the dressing 104. The therapy unit 124 can monitor the pressure at the tissue site as the negative-pressure source 102 draws fluid from the tissue site. As fluid is drawn from the sealed environment provided by the dressing 104, fluid can be drawn from the chamber 504 through the pressure-sensing port 404, the second opening 906, the lumen 912, and the secondary lumens of the multi-lumen conduit 806. The pressure at the tissue site can be determined by the pressure sensor 110 through the fluid connection provided by the pressure-sensing port 304, the second opening 506, the chamber 504, the pressure-sensing port 404, and the second opening 906.

[0077] In response to the pressure sensor 110 determining that a pressure at the tissue site is about a target negative pressure, the therapy unit 124 may vent the negative pressure to the ambient environment. For example, the tissue site may be vented to atmospheric pressure. Venting can occur by operation of a solenoid in the therapy system 100. For example, the therapy unit 124 may include the three-way valve 128 fluidly coupled to the fluid passage 308 the pressure sensor 110 and the ambient environment 130. The therapy unit 124 may actuate the three-way valve 128 to fluidly couple the fluid passage 308 to the pressure sensor 110 and the ambient environment. During a negative-pressure therapy cycle or as fluid is being drawn from the tissue site, the three-way valve 128 may isolate the fluid passage 308 from the ambient environment 130.

[0078] To vent the therapy system 100, the therapy unit 124, through for example, the controller 108, may actuate the three-way valve 128 to fluidly couple the fluid passage 308 to the ambient environment 130. Operating the three-way valve 128 to fluidly couple the tissue site to the ambient environment 130 permits the flow of fluid from the ambient environment into the accumulator 126 through the fluid passage 308. Fluid can flow from the accumulator 126 into the dressing 104 through the fluid passage 408, the second opening 906, the lumen 912, and through the secondary lumens of the multi-lumen fluid conductor 806. Fluid flowing from the ambient environment into the therapy system 100 can raise a pressure in the therapy system 100, causing the negative pressure in the therapy system 100 and the sealed environment over the tissue site to decay. The pressure sensor 110 can provide a signal indicative of the pressure at the tissue site to the controller 108. In response to the signal from the pressure sensor 110, the controller 108 can determine a rate of change of the negative pressure as the absolute pressure at the tissue site increases towards the ambient pressure. The rate of change can be stored by the controller 108 as the decay profile for the tissue site. In some embodiments, the therapy unit 124 may have one or more expected decay profiles associated with tissue sites of a particular size stored in, for example, the controller 108. In some embodiments, the therapy unit 124 may have expected decay profiles associated with tissue sites having a size between about 10 cubic centimeters (cc) and about 1000 cc. Once the decay profile for the tissue site covered by the dressing 104 has been determined, the controller 108 can compare the determined decay profile to the expected decay profiles to determine a size of the tissue site.

[0079] The systems, apparatuses, and methods described herein may provide significant advantages. For example, the therapy system 100 can accommodate variation in the manufacturing process that may negatively impact the accuracy of the tissue site size determination. In some embodiments, the therapy system 100 can accommodate variation in the construction of a canister filter, such as the filter 910, disposed between the canister 106 and the negative-pressure source 102. For example accumulator permits accommodate of variation between purchased filter lots, can create different decay profiles for the same size tissue site. In particular, the accumulator 126 can increase accuracy of tissue site size determination for tissue sites that are smaller than 100 cubic centimeters (cc) for which the impact of such manufacturing variation can be acute.

[0080] While shown in a few illustrative embodiments, a person having ordinary skill in the art will recognize that the systems, apparatuses, and methods described herein are susceptible to various changes and modifications that fall within the scope of the appended claims. Moreover, descriptions of various alternatives using terms such as “or” do not require mutual exclusivity unless clearly required by the context, and the indefinite articles "a" or "an" do not limit the subject to a single instance unless clearly required by the context. Components may be also be combined or eliminated in various configurations for purposes of sale, manufacture, assembly, or use. For example, in some configurations the dressing 110, the container 115, or both may be eliminated or separated from other components for manufacture or sale. In other example configurations, the controller 108 may also be manufactured, configured, assembled, or sold independently of other components.

[0081] The appended claims set forth novel and inventive aspects of the subject matter described above, but the claims may also encompass additional subject matter not specifically recited in detail. For example, certain features, elements, or aspects may be omitted from the claims if not necessary to distinguish the novel and inventive features from what is already known to a person having ordinary skill in the art. Features, elements, and aspects described in the context of some embodiments may also be omitted, combined, or replaced by alternative features serving the same, equivalent, or similar purpose without departing from the scope of the invention defined by the appended claims.

Claims

CLAIMS What is claimed is:

1. An accumulator for positioning inline between a canister and a therapy device, the accumulator comprising: a housing having a fluid chamber; a first port configured to be fluidly coupled to a pressure sensor of the therapy device; a second port configured to be fluidly coupled an unknown volume; a fluid passage disposed in the housing and fluidly isolated from the fluid chamber; a third port configured to be fluidly coupled to a negative-pressure source of the therapy device, the third port fluidly coupled to the fluid passage; and a fourth port configured to be fluidly coupled to the unknown volume, the fourth port fluidly coupled to the fluid passage.

2. The accumulator of claim 1, wherein the third port is configured to engage a supply tube seal of the therapy device.

3. The accumulator of claim 1, wherein the fourth port further comprises an accumulator tube seal having a concertinaed annulus.

4. The accumulator of claim 1, wherein the first port is configured to engage a sensing tube seal of the therapy device.

5. The accumulator of claim 1, wherein the second port further comprises a pressure-sensing tube seal having a concertinaed annulus.

6. The accumulator of claim 1, wherein the second port is further configured to be fluidly coupled to a filter of the canister.

7. The accumulator of claim 6, wherein the filter is a hydrophobic filter.

8. The accumulator of claim 1, further comprising a latching mechanism coupled to the housing, the latching mechanism configured to couple the housing to the therapy device and to couple the canister to the housing.

9. The accumulator of claim 1, wherein the fluid chamber has a volume of about 100 cubic centimeters (cc).

10. A system for supplying negative-pressure therapy and instillation therapy, the system comprising: a therapy unit configured to provide instillation therapy and negative-pressure therapy, the therapy unit having a pressure -sensing port, a negative-pressure supply port, and a latching mechanism; a pressure vessel configured to store negative-pressure, the pressure vessel configured to be coupled to the therapy unit via the latching mechanism, the pressure vessel comprising: a fluid chamber configured to be fluidly coupled to the pressure-sensing port, and

23 a negative-pressure bypass disposed in and fluidly isolated from the fluid chamber, the negative-pressure bypass configured to be fluidly coupled to the negativepressure supply port; and a fluid storage container, the fluid storage container configured to be fluidly coupled to the fluid chamber and the negative-pressure bypass, the fluid storage container further configured to be coupled to the pressure vessel. The system of claim 10, wherein the pressure vessel is disposed within the fluid storage container. The system of claim 10, wherein the pressure vessel is disposed within the therapy unit. The system of claim 10, wherein the pressure vessel comprises a filter chamber of the fluid storage container, the filter chamber having a hydrophobic filter disposed between the fluid chamber and the fluid storage container. The system of claim 10, wherein the pressure vessel further comprises a supply port fluidly coupled to the negative-pressure bypass and configured to engage a negative-pressure supply tube seal of the negative-pressure supply port. The system of claim 10, wherein the pressure vessel further comprises a canister port fluidly coupled to the negative-pressure bypass and having a tube seal having a concertinaed annulus. The system of claim 10, wherein the pressure vessel further comprises a device sensing port fluidly coupled to the fluid chamber and configured to engage a sensing tube seal of the pressuresensing port. The system of claim 10, wherein the pressure vessel further comprises an accumulator sensing port fluidly coupled to the fluid chamber and having a sensing tube seal having a concertinaed annulus. The system of claim 10, wherein the fluid chamber has a volume of about 100 (cc). The system of claim 10, further comprising a solenoid valve configured to fluidly couple the ambient environment to the fluid chamber through the pressure-sensing port. A method of determining a size of a tissue site, the method comprising: providing a therapy system configured to provide negative-pressure therapy and instillation therapy; fluidly coupling an accumulator to the therapy system; fluidly coupling a canister to the accumulator and a dressing; providing negative-pressure therapy; operating a solenoid valve of the therapy system to permit fluid flow from the ambient environment through the solenoid valve to the accumulator; determining a negative-pressure decay profile; and in response to determining a negative-pressure decay profile, determining the size of the tissue site. The systems, methods, and apparatuses as described an illustrated herein.