Patent Publication Number: US-2020289725-A1

Title: Control apparatus for delivery of therapy to wounds and related methods of use

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of co-pending U.S. patent application Ser. No. 15/663,710 filed 29 Jul. 2017 which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field 
     The present disclosure relates to medical devices, and, more particularly, to apparatus and related methods for delivering therapy to wound beds. 
     Related Art 
     A wound bed, as used herein, includes a localized region of tissue that has lost skin and been affected by hostile factors resulting in, for example, cellular abnormalities such as swelling, inflammation, degradation, infection, or cell death. The wound bed may include varying degrees of exposure of underlying layers and structures along with possible infections and tissue changes. The wound bed represents an unhealed wound. In contrast, a healed wound is a skin surface that was previously injured but the focal breach is now entirely sealed and covered by varying amounts of epidermis and scar tissue. The wound bed may lie within a wound boundary that extends around the affected region on the skin surface of the skin. The wound bed may extend contiguously in depth within the dermis, and the wound bed may extend subcutaneously, for example, into fat, muscle, or beyond. Thus, the wound bed may include undermined flaps, sinuses, tunnels, and fistulae and the surrounding affected tissues. An example of a wound bed including some reference anatomy is illustrated in  FIG. 1 . Wound boundary, as used herein, refers to the boundary of the wound bed at the skin surface of the skin. 
     Various negative pressure wound therapy (NPWT) devices currently used for treatment of wound bed include a dressing, a cover made of a flexible sheet of polymer and covered, at least in part, with adhesive, and an evacuation tube. In order to use current NPWT devices, the wound bed is packed with the dressing and the evacuation tube is placed about the dressing. The cover is then placed over the wound bed and attached adhesively to the skin surface around the wound bed to seal the wound bed, dressing, and evacuation tube in place. Finally, air within the region between the sheet and the wound bed is evacuated through the evacuation tube, which is in fluid communication with the dressing, to produce a suction pressure p s  within an enclosed space between the cover and the wound bed that is less than the ambient pressure p amb . The wound bed and surrounding skin are as the suction pressure p s  is decreased below the ambient pressure p amb . Exudate from the wound bed may be transmitted through the dressing and then evacuated through the evacuation tube. The wound may be subjected to a suction pressure p s  that is static and typically between around −80 mm Hg to around −175 mm Hg below ambient pressure p amb . 
     The suction pressure p s  may be maintained statically continually for weeks, if not months, until end of therapy, except during dressing changes. Because capillaries are exceedingly thin-walled microscopic tubules, capillaries are easily collapsed shut by the suction pressure. Studies have shown that while blood flow increases in proportion to suction pressure p s  at a further distance of 2.5 cm from the wound edge, blood flow is diminished detrimentally by at least as much closer to the wound bed, at 0.5 cm from the wound edge where increased blood flow is most needed. 
     It has thus become recognized that it may be beneficial to relieve the suction pressure p s  from time to time in order to allow capillaries adjacent to the wound bed to refill. However, the relief of the suction pressure p s , if at all provided, is accomplished in current NPWT devices by input of atmospheric air into the enclosed space between the covering and the wound bed. The suction pressure p s  may be relieved only to p amb −25 mm Hg instead of to p amb  in order to maintain the cover in sealing securement over the wound bed. Such relief of the suction pressure p s  in some devices may occur only intermittently, or not at all. 
     The average time to healing for a chronic wound is almost 6 months, attesting to the challenges of getting enough blood flow and oxygen to the wound bed to enable healing. NPWT requires skilled nursing and physician supervision, and is unable to salvage all wounds. Tens of thousands of deaths due to wound-related complications and 80,000 limb amputations per year occur in the US, each of which represent many months, if not years of failed costly therapy. Globally, there are 1 million amputations a year. NPWT may be tedious to apply and dressing changes, which occur usually every other day, are typically excruciatingly painful because of the tearing off of granulation tissue embedded in the dressing that occurs with each dressing change. Such disruption to the granulation tissue may set back the healing process. About 66% of wound beds require 15 weeks of NPWT while another 10% require 33 weeks or more of NPWT to heal. 
     In addition, the evacuation tube may become clogged by the proteinaceous exudate, which may result in interruption of the NPWT. The suction pressure p s  may be inaccurately sensed, falsely indicating that suction pressure p s  is at the desired level when in fact, due to exudate plug, there is little or no suction pressure within the enclosed space over the wound bed. Because the dressing is tedious to apply and painful to remove, as a practical matter, it is deemed not feasible to take it off repeatedly in order to attach other devices to deliver other therapies. 
     NPWT has been combined with instillation of an antibiotic solution in order to treat extra difficult wound beds. This system interposes one or more episodes of liquid therapy a few times a day in which the solution is introduced to the wound bed and allowed to “dwell” for a period of time and then removed. This “NPWT with instillation” requires a premeasurement of the volume of the wound bed, entering that volume into the infusion pump so that no excessive amount of instillation takes place that could jeopardize the integrity of the seal of the cover around the wound. Extra time, equipment and skilled attention is required to administer NPWT combined with instillation. 
     Another type of wound therapy in common use is total body hyperbaric oxygen (HBO). The patient is placed in a hyperbaric chamber and exposed, typically, to 2.5 ATA (atmospheres Absolute) of medically pure oxygen for 90 minutes. Exposure past 120 minutes increases the risk of oxygen toxicity, probably due to the increased formation of superoxide, H 2 O 2  or other oxidizing free radicals. Seizures and other serious consequences may result. Such a 90-minute session avails oxygen enrichment to the wound bed for a mere 6% of a day. The Medicare branch of the US Government usually approves HBO treatment for 30-40 sessions at a time at a cost per session of many hundreds to $1,000. This underscores not only the high cost of chronic wound care and HBO&#39;s low ability to effect healing with just a few sessions, but also the general lack of more efficacious therapeutic modalities. 
     Therefore, for at least these reasons, it is evident that there is a strong and unmet need for improved apparatus for delivering wound therapy as well as related methods of wound therapy. 
     BRIEF SUMMARY OF THE INVENTION 
     These and other needs and disadvantages may be overcome by the wound therapy apparatus and related method of use disclosed herein. Additional improvements and advantages may be recognized by those of ordinary skill in the art upon study of the present disclosure. 
     In various aspects, the wound therapy apparatus disclosed herein includes a wound interface that defines an enclosed space over a wound bed that is fluid tight when secured to a skin surface around the wound bed. The wound therapy apparatus includes a control group that cooperates with the wound interface to regulate input of input fluid comprising a gas having an O 2  concentration greater than atmospheric air into the enclosed space and to regulate the withdrawal of output fluid from the enclosed space in order to vary an actual pressure p a  within the enclosed space generally between a minimum pressure p min  and a maximum pressure p max , the minimum pressure p min  being less than ambient pressure p amb , in various aspects. The input of the gas having an O 2  concentration greater than atmospheric air is sequential with withdrawal of the gas having an O 2  concentration greater than atmospheric air, in various aspects. 
     In various aspects, the wound therapy apparatus disclosed herein includes a liquid source of liquid, a gas source of gas having an O 2  concentration greater than that of atmospheric air, and a wound interface engaged with a skin surface around a wound bed to define an enclosed space about the wound bed, the enclosed space being fluid tight. The wound therapy apparatus includes a control group in operable communication with the liquid source, the gas source, and the enclosed space to selectively input liquid and gas into the enclosed space and to regulate the withdrawal of output fluid from the enclosed space, in various aspects. 
     Related methods of use of the wound therapy apparatus disclosed herein may include the step of engaging a wound interface with a skin surface around a wound bed thereby defining an enclosed space, and the step of regulating the input of input fluid into the enclosed space in sequence with regulating the withdrawal of output fluid from the enclosed space using a control group thereby altering periodically the actual pressure p a  within the enclosed space according to a pressure cycle of a target pressure p 0 , in various aspects. The pressure cycle has a minimum pressure p min  and a maximum pressure p max , and the input fluid comprises a gas having an O 2  concentration greater than atmospheric air, in various aspects. 
     This summary is presented to provide a basic understanding of some aspects of the methods and apparatus disclosed herein as a prelude to the detailed description that follows below. Accordingly, this summary is not intended to identify key elements of the apparatus and methods disclosed herein or to delineate the scope thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  by cross-sectional view an exemplary wound bed that demonstrates undermining, wound tunneling, and fistulae; 
         FIG. 2  illustrates by schematic diagram an exemplary implementation of a wound therapy apparatus; 
         FIG. 3A  illustrates by schematic diagram a second exemplary implementation of a wound therapy apparatus in a first operational configuration; 
         FIG. 3B  illustrates by schematic diagram the exemplary implementation of a wound therapy apparatus of  FIG. 3A  in a second operational configuration; 
         FIG. 4A  illustrates by cut-away schematic diagram a portion of the exemplary wound therapy apparatus of  FIG. 3A  in the first operational configuration; 
         FIG. 4B  illustrates by cut-away schematic diagram a portion of the exemplary wound therapy apparatus of  FIG. 3A  in the second operational configuration; 
         FIG. 5  by schematic diagram operational states of the exemplary wound therapy apparatus of  FIG. 3A ; 
         FIG. 6A  illustrates by cut-away elevation view a third exemplary implementation of a wound therapy apparatus at a first stage of operation; 
         FIG. 6B  illustrates by cut-away elevation view portions of the exemplary wound interface of  FIG. 6A  at a second stage of operation; 
         FIG. 7  illustrates by cut-away perspective view a fourth exemplary implementation of a wound interface; 
         FIG. 8  illustrates by cut-away elevation view a fifth exemplary implementation of a wound interface; 
         FIG. 9A  illustrates by Cartesian plot an exemplary pressure cycle as may be delivered to a wound bed by the wound therapy apparatus, such as the exemplary wound therapy apparatus of  FIGS. 2, 3A, 6A, 7, and 8 ; 
         FIG. 9B  illustrates by Cartesian plot a second exemplary pressure cycle as may be delivered to a wound bed by the wound therapy apparatus, such as the exemplary wound therapy apparatus of  FIGS. 2, 3A, 6A, 7, and 8 ; 
         FIG. 9C  illustrates by Cartesian plot a third exemplary pressure cycle as may be delivered to a wound bed by the wound therapy apparatus, such as the exemplary wound therapy apparatus of  FIGS. 2, 3A, 6A, 7, and 8 ; 
         FIG. 9D  illustrates by Cartesian plot a fourth exemplary pressure cycle as may be delivered to a wound bed by the wound therapy apparatus, such as the exemplary wound therapy apparatus of  FIGS. 2, 3A, 6A, 7, and 8 ; 
         FIG. 9E  illustrates by Cartesian plot a fifth exemplary pressure cycle as may be delivered to a wound bed by the wound therapy apparatus, such as the exemplary wound therapy apparatus of  FIGS. 2, 3A, 6A, 7, and 8 ; 
         FIG. 9F  illustrates by Cartesian plot a sixth exemplary pressure cycle as may be delivered to a wound bed by the wound therapy apparatus, such as the exemplary wound therapy apparatus of  FIGS. 2, 3A, 6A, 7, and 8 ; 
         FIG. 9G  illustrates by Cartesian plot a seventh exemplary pressure cycle as may be delivered to a wound bed by the wound therapy apparatus, such as the exemplary wound therapy apparatus of  FIGS. 2, 3A, 6A, 7, and 8 ; 
         FIG. 9H  illustrates by Cartesian plot an eighth exemplary pressure cycle as may be delivered to a wound bed by the wound therapy apparatus, such as the exemplary wound therapy apparatus of  FIGS. 2, 3A, 6A, 7, and 8 ; 
         FIG. 9I  illustrates by Cartesian plot a ninth exemplary pressure cycle as may be delivered to a wound bed by the wound therapy apparatus, such as the exemplary wound therapy apparatus of  FIGS. 2, 3A, 6A, 7, and 8 ; 
         FIG. 9J  illustrates by Cartesian plot a tenth exemplary pressure cycle as may be delivered to a wound bed by the wound therapy apparatus, such as the exemplary wound therapy apparatus of  FIGS. 2, 3A, 6A, 7, and 8 ; and 
         FIG. 10  illustrates by process flow chart an exemplary method of use of the wound therapy apparatus such as the exemplary wound therapy apparatus of  FIGS. 2, 3A, 6A, 7, and 8 ; 
     
    
    
     The Figures are exemplary only, and the implementations illustrated therein are selected to facilitate explanation. The number, position, relationship and dimensions of the elements shown in the Figures to form the various implementations described herein, as well as dimensions and dimensional proportions to conform to specific force, weight, strength, flow and similar requirements are explained herein or are understandable to a person of ordinary skill in the art upon study of this disclosure. Where used in the various Figures, the same numerals designate the same or similar elements. Furthermore, when the terms “top,” “bottom,” “right,” “left,” “forward,” “rear,” “first,” “second,” “inside,” “outside,” and similar terms are used, the terms should be understood in reference to the orientation of the implementations shown in the drawings and are utilized to facilitate description thereof. Use herein of relative terms such as generally, about, approximately, essentially, may be indicative of engineering, manufacturing, or scientific tolerances such as ±0.1%, ±1%, ±2.5%, ±5%, or other such tolerances, as would be readily recognized by those of ordinary skill in the art upon study of this disclosure. 
     DETAILED DESCRIPTION OF THE INVENTION 
     A wound therapy apparatus and related methods of wound therapy are disclosed herein. In various aspects, the wound therapy apparatus includes a wound interface engaged with a skin surface around a wound bed to define an enclosed space over the wound bed, the enclosed space being fluid tight. A control group cooperates with the wound interface to regulate input of input fluid into the enclosed space and to regulate the withdrawal of output fluid from the enclosed space in order to vary an actual pressure p a  within the enclosed space generally between a minimum pressure p min  and a maximum pressure p max , in various aspects. The minimum pressure p min  is less than ambient pressure p amb , and the input of the gas is sequential with withdrawal of the gas having an O 2  concentration greater than atmospheric air, in various aspects. The control group may vary periodically the actual pressure p a  within the enclosed space in a pressure cycle between the minimum pressure p min  and the maximum pressure p max . The gas may have an O 2  concentration greater than atmospheric air (about 20.95% by volume or about 0.2095 mole O 2  per mole of dry air), 
     Fluid, as used herein, includes, liquid(s), gas(ses), and combinations thereof. Liquid includes, for example, saline solution, Dakin&#39;s solution, proteolytic enzyme solution, biofilm degradation solution, cytokines, antibiotic lavage, amniotic fluid, platelet-enriched plasma, antibiotic, analgesic, anesthetic, and combinations thereof. Liquid may include saline or water based solutions that, for example, irrigate the wound bed, remove bio-burden, or moisturize the wound bed. 
     Gas may include, for example, air, oxygen, nitric oxide, nitrogen, or suitable therapeutic or inert gasses, and combinations thereof. Gas, for example, may be nitric oxide diluted in nitrogen at about 200 ppm to about 800 ppm. Gas input into the enclosed space to increase the actual pressure p a  within the enclosed space from the minimum pressure p min  to the maximum pressure p max  may have an O 2  concentration greater than atmospheric air (about 21.95% by volume), in various aspects. In various aspects, the gas may be medical grade oxygen. Medical grade oxygen may conform to certain standards, for example, United States Food and Drug Administration standards or other appropriate regulatory standards. In various aspects, the medical grade oxygen may be United States Pharmacopoeia grade oxygen. In various other implementations, input fluid  16  supplied to wound interface  115  may be a liquid that may have some therapeutic benefit. 
     Sequential withdrawal of output fluid from the enclosed space and input of input fluid into the enclosed space means that withdrawal of output fluid and the input of input fluid does not occur simultaneously. Input fluid may be being input into the enclosed space or output fluid may be being withdrawn from the enclosed space but not the input of input fluid simultaneously with output of output fluid. An exception may be when the input fluid is a liquid and the liquid is input and withdrawn simultaneously, for example, during irrigation of the wound bed. Simultaneous input of liquid may irrigate or flush the wound bed with an amount of liquid several times the volume of the enclosed space to cleanse the wound bed of, for example, microbes, cellular debris, and biofilm. 
     Using the “downtime” of the relief phase of NPWT for programmed delivery of oxygen or other therapeutic fluids including gases and liquids into the enclosed space may effectively result in a substantial amount of new beneficial therapy in a 24-hour span where previously not even suction therapy existed. The net result is the even, regular addition of many new extra hours of beneficial therapy interspersed between suction pressure therapy that may accelerate healing through synergistic effects. Because chronic wound healing is already extremely protracted, lasting on average 23 weeks, the ability to add important needed therapy each and every day—without reducing the duration of the fundamental pressure therapy—may serve as a de novo creation of additional synergies that may accelerate healing. For example, consider a pressure cycle having a 6-minute duration with pressure p 0  at p min  for 4 minutes and the pressure p 0  is relieved to p max  for 2 minutes (i.e., ⅓ of the duration of the negative pressure cycle is pressure relief). In this example, p max  may be around ambient pressure p amb  or greater. Using fluid with O 2  concentration greater than atmospheric air results in 2 minutes of topical oxygen therapy around ambient or higher pressure in this example. Ten 2-minute cycles of such topical oxygen therapy per hour add up to 240 cycles daily that equals 8 hours per day of topical oxygen therapy without decreasing the amount of negative pressure therapy delivered. This may deliver additional therapy without displacing or shortening the fundamental underlying pressure therapy. Note that p min , p max  and p amb  are approximate and relative, and may vary from cycle to cycle depending on apparatus and environmental factors including altitude. The therapeutic results are substantially achieved regardless whether the target pressures are attained exactly or approximated. 
     As a second example, the pressure cycle has a 6-minute duration with pressure p 0  at p min  for 3 minutes and the pressure relieved to p max  for 3 minutes (½ of the duration of the pressure cycle), which results in delivery of topical oxygen therapy to the wound bed around ambient pressure or higher totaling 12 hours per day. Therefore, towards the latter healing phase when edema and exudation is greatly diminished such that negative pressure p min  is needed less, the duration of topical oxygen can be correspondingly increased to accelerate the next phase of healing. 
     In various aspects, every nth pressure cycle (where n is any suitable number such as 2 through 60 or even 120 or more) is relieved with a liquid. 
     The methods of wound therapy include, in various aspects, providing a therapy regimen to the wound bed within an enclosed space, the therapy regimen comprising delivering consecutively a number of pressure cycles of an actual pressure p a  within the enclosed space, each pressure cycle generally comprising a pressure range p min ≤p a ≤p max  where p min ≤p amb  and p amb ≤p max  with p min &lt;p max  and p amb  is the ambient pressure, an input fluid comprising gas(es) and liquids being introduced into the enclosed space as each pressure cycle progresses from p min  to p max . Pressures p min , p max , and the duration of the pressure cycle as well as the fluid(s) introduced into the enclosed space may vary from pressure cycle to pressure cycle depending on the desired therapeutic goal desired. 
     In various aspects, the methods of wound therapy may include the step of engaging a wound interface with a skin surface around a wound bed thereby defining an enclosed space. In various aspects, the methods of wound therapy may include the step of regulating the input of input fluid into the enclosed space in sequence with regulating the withdrawal of output fluid from the enclosed space using a control group thereby altering periodically the actual pressure p a  within the enclosed space generally according to a pressure cycle of a target pressure p 0 , the pressure cycle having a minimum pressure p min  and a maximum pressure p max , the input fluid comprising a gas having an O 2  concentration greater than atmospheric air. In various aspects, the methods of wound therapy may include the step of removing exudate from the enclosed space by flowing the output fluid to a reservoir. In various aspects, the input fluid may be a liquid in which case the input of the input liquid and the output of the output liquid may occur sequentially or simultaneously depending the therapeutic goal. In various aspects, the methods of wound therapy may include the step of receiving data from a user with an I/O interface; and communicating the data from the user I/O to a controller thereby altering targeted aspects of the pressure cycle. In various aspects, the methods of wound therapy may include the step of delivering a therapy regimen to the wound bed, the therapy regimen comprising a series of pressure cycles of the actual pressure p a within  the enclosed space. 
     By inputting gas with O 2  concentration greater than that found in atmospheric air into the enclosed space during portions of the pressure cycle in certain aspects, the resulting O 2  enrichment may resuscitate the hypoxic wound cells, may sustain the revived cells in cell division and collagen synthesis, may inhibit the growth of anaerobic bacteria, may enhance the efficacy of antibiotics, and may enhance survival of stem cells and tissue grafts, and augment the therapeutic benefits of other bioengineered materials. Furthermore, such O 2  enrichment provided to the wound bed may be beneficial because the O 2  enrichment is [1] under a favorable concentration gradient, [2] at a favorable pressure gradient that does not impede baseline arterial perfusion (such as between 20-60 mm Hg, but may be higher for brief durations), and [3] during a period of relative reflex hyperemia in regions of tissue where capillaries may have previously been collapsed under suction. The result is the maximum absorption and uptake of oxygen under increased-flow condition. Additionally, in aspects wherein the fluid-tight enclosed space provides a hyperbaric condition, the amplitude and period of the O 2  delivery may additionally serve and be programmed to provide a form of external pulsation of pressurized O 2 , with beneficial circulatory effect akin in some respects to providing external CPR to the wound bed. 
     In various aspects, the methods of wound therapy may include the step of inputting liquid into the enclosed space and may include the step of withdrawing liquid from the enclosed space. The methods of wound therapy may include lavage of the wound bed using liquid input into the enclosed space and withdrawn from the enclosed space in sequence. The method of wound therapy may include providing a therapy to the wound bed by inputting liquid having therapeutic properties into the enclosed space. The therapeutic properties may include, for example, proteolytic, analgesic, antimicrobial, or healing properties. Similarly, and in various aspects, if the goal is one of achieving rapid-flow irrigation, then the liquid input and output with respect to the enclosed space may occur simultaneously instead of sequentially. 
     Ambient pressure p amb , as used herein, refers to the pressure in a region surrounding the wound therapy apparatus. Ambient pressure p amb , for example, may refer to atmospheric pressure, hull pressure within an aircraft where the wound therapy apparatus is being utilized, or pressure maintained generally within a building or other structure where the wound therapy apparatus is being utilized. Ambient pressure p amb  may vary, for example, with elevation or weather conditions. Pressure p min  refers to the minimum pressure achieved within the enclosed space of the wound therapy apparatus, and periodically varying of pressure p 0 , pressure variation, varying pressure, and similar term refer to changes of pressure p 0  within the enclosed space over time, in various aspects. Pressure p max  refers to the maximum pressure achieved within the enclosed space of the wound therapy apparatus. Exudate, as used herein, includes, for example, proteinaceous liquids exuded from the wound bed, along with various plasma and blood components and other bodily fluids. Exudate may additionally include waste liquids such as irrigation liquid. 
     The term fluid-tight or related terms, as used herein, means sufficiently leak-resistant to allow insufflation or vacuum suction to create actual pressure p a  within the enclosed space of a wound interface that may be above or below ambient pressure p amb , or to substantially retain fluids including both gasses and liquids within the enclosed space other than by passage through one or more lumen that may fluidly communicate with the enclosed space, in some aspects. The term fluid-tight or related terms, as used herein, means sufficiently leak-resistant to allow insufflation or vacuum suction to maintain actual pressure p a  within the enclosed space of a wound interface t above or below ambient pressure p amb , in various aspects. 
     As used herein the terms distal and proximal are defined from the point of view of a user, such as a physician, nurse, or medical technician, treating a patient with a wound therapy apparatus. A distal portion of the wound therapy apparatus is oriented toward the patient while a proximal portion of the wound therapy apparatus is oriented toward the healthcare provider. A distal portion of a structure may be closest to the patient while a proximal portion of the structure may be closest to the user treating the patient. 
     As used herein, a wound interface that is deformation resistant resists collapse and substantially maintains its shape, including defining an enclosed space within sufficient to draw a portion of wound bed towards or into the enclosed space, including the wound bed occupying the enclosed space, when subjected to actual pressure p a ≤p amb , in various aspects. In some aspects, at least portions of the wound interface that defines the enclosed space may be essentially rigid. The wound interface, in various aspects, is sufficiently deformation resistant to remain sealingly secured to skin surface and fluid-tight over pressure range p min ≤p a ≤p max . 
     Apparatus, related methods of use, and related compositions of matter disclosed herein may be implemented, at least in part, in software having the form of computer readable instructions operably received by one or more computers to cause, at least in part, the one or more computers to function as the apparatus or to implement the steps of the methods of use. The methods of use disclosed herein may be implemented as a combination of hardware and operatively received software, in various aspects. Compositions of matter disclosed herein include non-transient computer readable media operably received by the one or more computers to cause the one or more computers, at least in part, to function as the apparatus or to implement the steps of the methods of use. 
     A computer, as used herein, includes, a processor that may execute computer readable instructions operably received by the processor. The computer may be, for example, a single-processor computer, multiprocessor computer, multi-core computer, minicomputers, mainframe computer, supercomputer, distributed computer, personal computer, hand-held computing device, tablet, smart phone, and a virtual machine, and the computer may include several processors in networked communication with one another. The computer may include memory, screen, keyboard, mouse, storage devices, I/O devices, and so forth, in various aspects, that may be operably connected to a network. The computer may execute various operating systems (OS) such as, for example, Microsoft Windows, Linux, UNIX, MAC OS X, real time operating system (RTOS), VxWorks, INTEGRITY, Android, iOS, or a monolithic software or firmware implementation without a defined traditional operating system. 
     Network, as used herein, may include the Internet cloud, as well as other networks of local to global scope. The network may include, for example, data storage devices, input/output devices, routers, databases, computers including servers, mobile devices, wireless communication devices, cellular networks, optical devices, cables, and other hardware and operable software, as would be readily recognized by those of ordinary skill in the art upon study of this disclosure. Network may be wired (e.g. optical, electromagnetic), wireless (e.g. infra-red (IR), electromagnetic), or a combination of wired and wireless, and the network may conform, at least in part, to various standards, (e.g. Bluetooth®, FDDI, ARCNET IEEE 802.11, IEEE 802.20, IEEE 802.3, IEEE 1394-1995, USB). 
       FIG. 2  illustrates exemplary wound therapy apparatus  10 . As illustrated in  FIG. 2 , wound interface  15  is secured to skin surface  11  to define enclosed space  17  that is fluid tight over a wound bed, such as wound bed  213 ,  313 ,  413 . In this implementation, wound therapy apparatus  10  includes gas source  82  and liquid source  84  in fluid communication with enclosed space  17  of wound interface  15 . As illustrated in  FIG. 2 , wound therapy apparatus  10  includes control group  30 , and control group  30  includes controller  87 , user I/O  86 , valve  88 , pump  89 , and pressure sensor  91 . Control group  30  regulates the communication of gas  22  from gas source  82 , liquid  24  from liquid source  84 , or combinations of gas  22  and liquid  24  into enclosed space  17  as input fluid  16 , as illustrated. Control group  30  regulates the withdrawal of output fluid  18  from enclosed space  17 , and output fluid  18  may include, for example, input fluid  16  and exudate  19  as well as air evacuated from enclosed space  17  following attachment of wound interface  15  to skin surface  11 , as illustrated. It should be recognized that controller  87 , user I/O  86 , valve  88 , pump  89 , and pressure sensor  91  are grouped into control group  30  for explanatory purposes only, in this implementation, and that no spatial or other physical organization or proximity of controller  87 , user I/O  86 , valve  88 , pump  89 , and pressure sensor  91  with respect to one another or with respect to gas source  82 , liquid source  84  or wound interface  15  is implied by virtue of being grouped into control group  30 . 
     Controller  87  communicates operably with user I/O  86  via communication pathway  64  to communicate data  74  with user I/O  86 . Controller  87  communicates operably with valve  88 , pump  89 , and pressure sensor  91  via communication pathways  61 ,  62 ,  63  to control operations of valve  88 , pump  89 , pressure sensor  91 , respectively, at least in part in response to data  74  received by controller  87  from user I/O  86  in order to alter pressure p 0  within enclosed space  17 , for example, according to exemplary pressure cycle  500 ,  550 ,  600 ,  650 ,  700 ,  750 ,  800 ,  850 ,  900 ,  950  (see  FIGS. 9A, 9B, 9C, 9D, 9E, 9F, 9G, 9H, 9I, 9J , respectively) by regulating the input of input fluid  16  into enclosed space  17  and the withdrawal of output fluid  18  from enclosed space  17 . Controller  87  may control operations of valve  88 , pump  89 , pressure sensor  91  at least in part in response to data  74  received from user I/O  86 , for example, to deliver Therapy Regimen 1, 2, 3 or 4, to the wound bed enclosed by wound interface  15  (see Example 1). The user may select the pressure cycle, such as pressure cycle  500 ,  550 ,  600 ,  650 ,  700 ,  750 ,  800 ,  850 ,  900 ,  950 , and the user may select the therapy regimen, such as Therapy Regimen 1, 2, 3 or 4, using user I/O  86 . 
     Controller  87  controls the operation of wound therapy apparatus  10 , at least in part, based upon data  74  communicated to controller  87  from user I/O  86 . Controller  87  may control the operation of wound therapy apparatus  10 , at least in part, based upon data  71 ,  72 ,  73  communicated between controller  87  and valve  88 , pump  89 , and pressure sensor  91 , respectively. Valve  88  and pressure sensor  91  are illustrated as a single valve and a single pressure sensor in this exemplary implementation for explanatory purposes. Is should be recognized that valve  88  may include one or more valves variously disposed about wound therapy apparatus  10  and that pressure sensor  91  may include one or more pressure sensors variously disposed about wound therapy apparatus  10 , as would be readily recognized by those of ordinary skill in the art upon study of this disclosure. Controller  87  may include, for example, a processor, memory, software operably communicating with the microprocessor, A/D converter, D/A converter, clock, I/O connectors, and so forth, and controller  87  may be configured for example, as a single chip or as an array of chips disposed about a circuit board, as would be readily recognized by those of ordinary skill in the art upon study of this disclosure. In some implementations, controller  87  may be configured as software operatively received by a computer, and the computer may be, at least in part, located remote, for example, from valve  88 , pump  89 , and pressure sensor  91 . 
     User I/O  86  may include various switches, push buttons, dials, sliders, graphs, and so forth, whether virtual or physical, for obtaining data  74  from the user that are then communicated to controller  87  in order to allow the user to direct the operation of wound therapy apparatus  10  including pressure cycles of pressure p 0  within enclosed space  17  and the delivery of various therapy regimens. In certain implementations, user I/O  86  may be formed as software operably received by a computer. Controller  87  may communicate data  74  to user I/O  86  indicative of the operation of wound therapy apparatus  10 , and user I/O  86  may display data  74  to the user. 
     As illustrated in  FIG. 2 , gas source  82  fluidly communicates gas  22  and liquid source  84  fluidly communicates liquid  24  with enclosed space  17  of wound interface  15  as input fluid  16  controlled by controller  87  using valve  88 . For example, as controlled by controller  87 , valve  88  may select gas  22  from gas source  82 , liquid  24  from liquid source  84 , or combinations of gas  22  from gas source  82  and liquid  24  from liquid source  44  as input fluid  16  for input into enclosed space  17 , and valve  88  may regulate, at least in part, the input of input fluid  16  into enclosed space  17  of wound interface  15 . Gas source  82  may be, for example, a cylinder of gas including oxygen, an oxygen bag, an oxygen generator, or mains gas including mains oxygen. Liquid source  84  may be, for example, a container of liquid  24  or mains supply of liquid  24 . 
     As illustrated in  FIG. 2 , output fluid  18  withdrawn from enclosed space  17  passes through reservoir  81 , and reservoir  81  captures exudate  19  or liquid, such as liquid  24 , from output fluid  18  in chamber  99  of reservoir  81 . Gaseous portions of output fluid  18  or gas displaced from chamber  99  of reservoir  81  by capture of liquid  24  or exudate  19  therein may then be vented to the atmosphere from pump  89 . Valve  88 , pump  89 , or valve  88  in combination with pump  89  may regulate the withdrawal of output fluid  18  from enclosed space  17  of wound interface  15  under control of controller  87 . Reservoir  81  may be omitted when the quantity of exudate  19  is minimal or there is no liquid, such as liquid  24 , in output fluid  18 . 
     Liquid  24  may be withdrawn from enclosed space  17  at least in part by chamber pressure p r  within chamber  99  of reservoir  81  when chamber pressure p r  is less than ambient pressure p amb . Chamber  99 , which may be disposable and replaceable, provides storage for liquid  24  flowed through enclosed space  17  so that a volume of liquid  24  generally equal to the volume of chamber  99  may be flowed through enclosed space  17  and collected in chamber  99 . When pump  89  is OFF and chamber pressure p r  is less than ambient pressure p amb , the chamber pressure p r  decreases toward ambient pressure p amb  as liquid  24  withdrawn from enclosed space  17  is collected in chamber  99 . Liquid input into enclosed space  17  may be stopped, for example, when chamber pressure p r  reaches some set point below ambient pressure p amb , say −10 mm Hg, or when liquid  24  fills a certain portion of chamber  99  in order to prevent excessive pressure p 0  within enclosed space  17  that may breach the sealing attachment of wound interface  15  to skin surface  11 . 
     As indicated graphically in  FIG. 2 , valve  88  operably communicates with gas  22 , liquid  24 , input fluid  16 , and output fluid  18 . Accordingly, in this illustrated implementation, valve  88  may include one or more valves disposed about wound therapy apparatus to select input fluid  16  as gas  22 , liquid  24 , combinations of gas  22  and liquid  24 , to regulate, at least in part, the input of input fluid  16  into enclosed space  17  of wound interface  15 , and to regulate, at least in part, the withdrawal of output fluid  18  from enclosed space  17  of wound interface  15 . Data  71  may control the operation of valve  88  and data  71  may be indicative of the operation of valve  88 . For example, data  71  may position valve  88  from an open position to a closed position, or data  71  may indicate that valve  88  is in the open position or in the closed position. 
     As indicated graphically in  FIG. 2 , pressure sensor  91  operably communicates with gas  22 , liquid  24 , input fluid  16 , and output fluid  18 , and enclosed space  17 . Pressure sensor  91  may include one or more pressure sensors operable, for example, to detect pressure at various locations in gas  22 , liquid  24 , input fluid  16 , output fluid  18 , gas source  82 , liquid source  24 , or enclosed space  17  of wound interface  15 . Pressure sensor  91  may communicate data  73  indicative of the pressure at various locations in gas  22 , liquid  24 , input fluid  16 , output fluid  18 , gas source  82 , liquid source  24 , or enclosed space  17  to controller  87 , and controller  87  may alter the operation of valve  88  or pump  89  in response to data  73  from pressure sensor  91 . In particular, controller may control valve  88  or pump  89  to maintain the actual pressure p a  within enclosed space  17  generally between a minimum pressure min and a maximum pressure p max  and may vary the actual pressure p a  within enclosed space  17  according to a pressure cycle, such as pressure cycle  500 ,  550 ,  600 ,  650 ,  700 ,  750 ,  800 ,  850 ,  900 ,  950  as described in  FIGS. 9A, 9B, 9C, 9D, 9E, 9F, 9G, 9H, 9I, 9J , respectively. When p a  within enclosed space  17  exceeds maximum pressure p max  output fluid  18  may be withdrawn from enclosed space  17  and gaseous portions of output fluid may be vented to the atmosphere by control group  30 . As another example, if liquid  24  is input as input fluid  16  to increase the actual pressure p a  within the enclosed space above the minimum pressure p min , the control group may halt input of liquid  24  once the actual pressure p a  reaches a preset value (such as −20 mmHg) in order to prevent overflow of the enclosed space that may dislodge wound interface  15  from skin surface  11 . As yet another example, the control group may regulate input of liquid  24  to maintain the actual pressure p a  of liquid  24  in enclosed space  17  at a target pressure p 0  (such as −20 mmHg or ambient pressure p amb ) in order to prevent overflow of the enclosed space that may dislodge wound interface  15  from skin surface  11  when liquid  24  is simultaneously input as input fluid  16  and withdrawn as output fluid  18  from the enclosed space. 
     Data  73  may be communicated between controller  87  and pressure sensor  91  to control the sensing of pressure by pressure sensor  91 , for example, the frequency of pressure sensing. Data  73  may be indicative of pressure as sensed by pressure sensor  91 . 
     Input fluid  16  may be communicated under pressure of gas source  82  (e.g., a tank of compressed gas), pressure of liquid source  84  (e.g., piezometric head at liquid source), suction of pump  89 , and combinations thereof. Pump  89  may withdraw output fluid  18  from enclosed space  17 . Pump  89  may be, for example, a centrifugal pump, positive displacement pump, or peristaltic pump, in various implementations. Data  72 , for example, may be communicated from controller  87  to pump  89  to control a speed of pump  89  or data  72  may be indicative of the actual speed of pump  89  as communicated from pump  89  to controller  87 . 
     Wound therapy apparatus  10  may include various fluid conveyances, for example hoses, pipes, valves, tubing, connectors, pressure regulators, plenums, and various other fittings, to communicate gas  22  and liquid  24  from gas source  82  and liquid source  84 , respectively, to enclosed space  17  of wound interface  15  as input fluid  16  and to communicate output fluid  18  withdrawn from enclosed space  17  of wound interface  15 . Communication pathways  61 ,  62 ,  63 ,  64  may be, for example, wired, wireless, optical (e.g., fiberoptic, infrared), networked (e.g., Internet), or various combinations thereof, in various implementations. Valve  88 , pump  89 , and pressure sensor  91  may include, for example, A/D converters, D/A converters, actuators, solenoids, stepper motors, microprocessors, to control the operations of valve  88 , pump  89 , and pressures sensor  91  using data  71 ,  72 ,  73 , respectively, or to communicated data  71 ,  72 ,  73  to controller  87  indicative of the operation of valve  88 , pump  89 , and pressure sensor  91 , as would be readily recognized by those of ordinary skill in the art upon study of the present disclosure. Data  71 ,  72 ,  73 ,  74  may be digital, analog, or combinations thereof, in various implementations. 
     One or more power source(s) may be disposed about wound therapy apparatus  10  in electrical communication with controller  87 , valve  88 , pump  89 , and pressure sensor  91  to flow electrical power thereupon. The power source(s) may be, for example, mains electric, battery, or combinations of mains electric and battery, and the power source(s) may include, for example, a transformer, an inverter, a rectifier, filter(s), surge protector, as would be readily recognized by those of ordinary skill in the art upon study of the present disclosure. 
       FIGS. 3A, 4A  and  FIGS. 3B, 4B  illustrate exemplary wound therapy apparatus  100  in operational configurations  111 ,  113 , respectively. In operational configuration  111 , as illustrated in  FIG. 3A , control group  130 , includes reservoir housing  120  and control package  160  releasably secured to one another. As illustrated in  FIG. 3B , reservoir housing  120  has been removed from releasable securement to control package  160  so that control group  130  includes only control package  160  in operational configuration  113 . Accordingly, in exemplary wound therapy apparatus  100 , control group  130  may be operably configured as either reservoir housing  120  in releasable securement to control package  160  per operational configuration  111 , or control package  160  alone per operational configuration  113 . 
     As illustrated in  FIGS. 3A, 3B , wound therapy apparatus  100  includes gas source  112 , humidity source  114 , wound interface  115  that defines enclosed space  117 , and control group  130 . Control package  160  of control group  130  selects input fluid  116  as either gas  125  from gas source  112  plus humidity  129  from humidity source  114  or air  128  from atmosphere  127 , and control package  160  controls the input of input fluid  116  into enclosed space  117  of wound interface  115 , the withdrawal of output fluid  118  from enclosed space  117  of wound interface  115 , and the exhausting of at least portions of output fluid  118  into the atmosphere, as illustrated in  FIGS. 3A, 3B . Wound therapy apparatus  100  includes various fluid conveyances, for example hoses, pipes, valves, tubing, connectors, plenum, reservoirs, and various other fittings, to communicate gas  125  from gas source  112  and air  128  from atmosphere  127  into enclosed space  117  as input fluid  116  and to communicate output fluid  118  between wound interface  115  and control group  130 . Input fluid  116  as air  128  from atmosphere  127  may be input into the enclosed space  117  to set actual pressure p a  within the enclosed space  117  to ambient pressure p amb  in the event of power failure of wound therapy apparatus  100 . 
     As illustrated in  FIG. 3A , reservoir housing  120  includes reservoir  150 , and output fluid  118  withdrawn from enclosed space  117  passes through reservoir  150 . Reservoir  150  captures exudate  152  including other liquids from output fluid  118  in chamber  155  of reservoir  150 , in the implementation of  FIG. 3A . Gaseous portions of output fluid  118  or gas displaced from chamber  155  of reservoir  150  by capture therein of exudate  152  may then be discharged to the atmosphere  127  from pump  189 , as illustrated. Reservoir  150  may be, for example, a canister, container, or space within reservoir housing  120  that may comprise substantially the interior of reservoir housing  120 . Reservoir  150  and reservoir housing  120  may be formed as a unitary structure in certain implementations. Reservoir  150  may be removable and replaceable in some implementations. Reservoir  150  may be openable to allow reservoir  150  to be emptied and reused, in some implementations. In other implementations, reservoir  150  is sealed so as not to be reusable. In such implementations, reservoir housing  120  may functionally become the reservoir and may be replaced in its entirety. Accordingly, either reservoir  150 , or reservoir housing  120  with or without reservoir  150 , may be formed to be disposable. Chamber  155  of reservoir  150  may include a pad layer or pouch of super absorbent polymer to gel exudate  152 . Odor neutralizing agents may optionally also be included in reservoir housing  120  including within chamber  155 . 
     As illustrated in  FIG. 3B , reservoir housing  120  has been removed from releasable securement to control package  160  and control group  130  includes only control package  160  in operational configuration  113 . Input fluid  116  flows under the control of control package  160  to wound interface  115 , and output fluid  118  flows from wound interface  115  towards control package  160  without passage through reservoir housing  120  in operational configuration  113 , as illustrated in  FIG. 2B . Reservoir housing  120  may be disengaged from control package  160  placing control group  130  in operational configuration  113  because, for example, exudate  152  from the wound bed is low to non-existent, wound interface  115  retains exudate  152  within wound interface  115 , or it is desirable for the patient to be unencumbered by reservoir housing  120 . Control group  130  may recognize the change in configuration and deliver therapies that are appropriate for the applicable corresponding configuration. 
     As illustrated in  FIG. 4A , control package  160 , includes power source  162  that may variously be, for example, a battery, mains electric, or a battery in combination with mains electric with the battery providing back-up power. Power source  162 , in various implementations, may include, for example, a transformer, inverter, and regulatory circuitry, as would be readily understood by those of ordinary skill in the art upon study of this disclosure. If power source  162  includes a battery, the battery may be, for example, nickel cadmium, nickel metal hydride, or lithium ion based. 
     Power source  162  is in electrical communication with various components of controller  60  including controller  165 , pump  168 , valves  172 ,  173 ,  174 , pressure sensor  176 , pressure sensor  178 , and user I/O  145  to flow power thereto, in this implementation. Various electrical pathways may be disposed about control group  130  to communicate electrical power from power source  162  to controller  165 , pump  168 , valves  172 ,  173 ,  174 , pressure sensors  176 ,  178 , and user I/O  145 . Pump  168  may be, for example, a rotary pump or a positive displacement pump, in various implementations. Valves  172 ,  173 ,  174  may be electromechanically actuated by, for example, solenoid or stepper motor. One or more of the valves  172 ,  173 ,  174  may be configured as a three-way valve or as a combination of valves, in various implementations. While this implementation includes pressure sensors  176 ,  178 , other implementations may include a single pressure sensor that functions as the combined pressure sensors  176 ,  178  or senses pressures of different locations. Other implementations of control group  130  may include various numbers of valves, such as valves  172 ,  173 ,  174  that work in conjunction with various numbers of pressure sensors, such as pressure sensors  176 ,  178 , to measure and regulate the pressure(s), leading up to, within, or downstream from, a compartment or housing. Such multi-point sensing may enable a more intelligent differential monitoring and diagnosis of a system or fault condition and may pin point the location and nature of a condition to facilitate troubleshooting, adjustment, or corrective action. 
     Controller  165  controls, at least in part, the operation of wound therapy apparatus  10  including control group  130 , in this implementation. Controller  165  may include, for example, a microprocessor, memory, A/D converter, D/A converter, clock, I/O connectors, and so forth, as would be readily recognized by those of ordinary skill in the art upon study of this disclosure. Controller  165  may communicate with power source  162  to monitor power source  162 , to receive power from power source  162 , or to regulate the flow of power from power source onto pump  168 , valves  172 ,  173 ,  174 , pressure sensors  176 ,  178 , and user I/O  145 . Controller  165  may communicate operatively with pump  168 , valves  172 ,  173 ,  174 , pressure sensors  176 ,  178  to regulate the operation thereof. Controller  165  may communicate operatively with pump  168 , valve  172 , valve  174 , pressure sensors  176 ,  178  to receive information from pump  168 , valves  172 ,  173 ,  174 , pressure sensors  176 ,  178  indicative of the operation thereof or indicative of the operation of wound therapy apparatus  100 . 
     User I/O  145 , which may be placed exteriorly about control group  130  or remotely from control group  130 , may include a display for the display of the operational status of wound therapy apparatus  100  to a user. User I/O  145  may include various switches, push buttons, dials, and so forth, whether virtual or physical for obtaining user inputs to allow the user to regulate the operation of wound therapy apparatus  100  including control group  130 . User I/O  145  and controller  165  may communicate with one another to communicate user inputs from user I/O  145  to controller  165  to regulate the operation of wound therapy apparatus  100  including control group  130  and to communicate information from controller  165  to user I/O  145  indicative of operations of wound therapy apparatus  100 . 
     Various communication pathways such as wired, optical (e.g. LASER, IR), and network may be included about wound therapy apparatus  10  including control group  130  for communication between controller  65  and pump  68 , valve  72 , valve  73 , valve  74 , pressure sensors  76 ,  78 , and user I/O  45 . For example, in some implementations, at least portions of user I/O  145  may be remote from the remainder of control group  130 , such as on a smart phone application, and user I/O  145  may communicate with controller  165  by various networks that may be wireless, at least in part. User I/O  145  may interface with a network such as the Internet by wired or wireless connection to communicate data indicative of operations of wound therapy apparatus  100  via networked communication or to receive inputs that regulate operations of wound therapy apparatus  100 . 
     As illustrated in  FIG. 3B , control group  130  includes control package  160 , and control package  160  includes power source  162 , controller  165 , pump  168 , valves  172 ,  173 ,  174  pressure sensors  176 ,  178 , and user I/O  145 . Reservoir housing  120  has been removed from engagement with control package  160 , in operational configuration  113 , so that control group  130  includes control package  160  and excludes reservoir housing  120 , as illustrated in  FIG. 3B . 
     Wound therapy apparatus  100  may be placed in operational configuration  111 , as illustrated in  FIG. 3A . As illustrated in  FIG. 3A , wound interface  15  is secured to a skin surface  111  to enclose a wound bed, such as wound bed  113 ,  213 ,  313 , within enclosed space  117  that is fluid tight. Wound interface  15 , control group  130  including both reservoir housing  120  and control package  160 , humidity source  114 , and gas source  112  are then placed in fluid communication with one another, as indicated in  FIG. 3A . Wound therapy apparatus may be placed in operational configuration  111  when the wound bed is exuding exudate  152 , for example, in early stages of wound therapy, because operational configuration  111 , as illustrated in  FIGS. 3A, 4A , includes reservoir  150  for the collection of exudate  152 . 
     As illustrated in  FIGS. 4A, 4B , gas  125  from gas source  112  combined with humidity  129  from humidity source  114  is in communication with valve  174  through connector  182  of control group  130 , and air  128  from atmosphere  127  is in communication with valve  173  through port  183  of control package  160 . Note that, in  FIGS. 4A, 4B , the path of input fluid  116  is indicated by arrows having a white interior, and the path of output fluid  118  is indicated by solid black arrows. Input fluid  116  may be selected as either air  128  or gas  125  including humidity  129  or by operation of valves  173 ,  174 . Controller  165  may operate valve  174  to select gas  125  plus humidity  129  as input fluid  116 , or controller  165  may operate valve  173  to select air  128  as input fluid. Input fluid  116  then flows either from valve  173  or from valve  174 , through connector  184  of control group  130 , and thence into the enclosed space  117  of the wound interface  115 . 
     Note that some implementations may omit humidity source  114 , for example, when the flow rate of input fluid  116  is low the oxygen flow is very low and, thus, humidification is not required as moisture in the wound bed is sufficient. Also, it should be recognized that gas source  112  may include multiple gas sources that may supply a variety of gasses and combinations of gasses as gas  125 , and the composition of gas  125  may vary during the course of wound therapy. The user may variously select the composition of gas  125  for use during various times of wound therapy. 
     As illustrated in  FIG. 4A , pressure sensor  176  is in operable communication with enclosed space  117  including input fluid  116  as input fluid  116  is being input into enclosed space  117  to detect the actual pressure p a  within the enclosed space  117 , in this implementation. The actual pressure p a  within enclosed space  117  as detected by pressure sensor  176  is communicated from pressure sensor  176  to controller  165 , and controller  165  may position either valve  173  or valve  174  to regulate flow of input fluid  116  into the enclosed space  117  in order to cause actual pressure p a  to proximate the target pressure p 0  within the enclosed space  117  (i.e., make p a ≈p 0 ), in this implementation. 
     Pressure sensor  178  is in operable communication with enclosed space  117  including output fluid  116  as output fluid  118  is being withdrawn from enclosed space  117  to detect the actual pressure p a  within the enclosed space  117 , in this implementation. The actual pressure p a  within the enclosed space as detected by pressure sensor  178  may be communicated from pressure sensor  178  to controller  165 , and controller  165  may position valve  172 , regulate pump  168 , or both position valve  172  and regulate pump  168  in order to regulate flow  118  from the enclosed space, and, thus, cause actual pressure p a  to proximate the target pressure p 0  within the enclosed space  117  (i.e., make p a ≈p 0 ). 
     As illustrated in  FIG. 4A , output fluid  118 , withdrawn, at least in part, by pump  168 , flows from the enclosed space of wound interface  115  through connector  186  of control group  130 , through reservoir  150 , towards filter  124 , towards connector  188  between reservoir housing  120  and control package  160 , towards pump  168  under the control of valve  172 . Exudate  152  including other liquids is retained in chamber  155  as output fluid  118  flows through chamber  155  of reservoir  150 , and exudate  152  including other liquids may also be captured by filter  124  as output fluid  118  as output fluid  118  passes through filter  124 , as illustrated. The remaining gaseous portions of output fluid  118  are then exhausted into the atmosphere on the discharge side of pump  168 , as illustrated. 
     Filter  124  prevents exudate  152  including other liquid in output fluid  118  from reaching control package  160  including pump  168 , thereby serving a protective function. For example, in some implementations, filter  124  may include a hydrophobic ultra-high molecular weight polyethylene (UHMW-PE) that may optionally be impregnated with carboxymethyl cellulose. Filter  124  may include a hydrophobic filter material may comprise of sintered PTFE with optional addition of a super absorbent polymer such as sodium polyacrylate, or sodium carboxymethyl cellulose. When exudate  152  reaches filter  124 , filter  124  clogs and expands abruptly, for example, increasing the pressure detected by pressure sensor  178 , that, in turn, may trigger a protective shutoff of pump  168  by controller  165 . Filter  124  may be replaceably received within reservoir housing  120 , or filter  124  may be omitted, in various implementations. 
     Note that various numbers and combinations of valve(s), such as valves  172 ,  173 ,  174 , and pressure sensor(s), such as pressure sensors  176 ,  178 , may be used in combination with controller  165  to regulate the flow of input fluid  116  into the enclosed space  117  or to regulate the flow of output fluid  118  from the enclosed space  117  in order to cause actual pressure p a  to proximate target pressure p 0  within the enclosed space. For example, valves  173   174  may be replaced with a three-way valve that selectable between no flow, flow of air  182 , or flow of gas  125  including humidity  129 . 
     Alternatively, in operation, wound therapy apparatus  100  may be placed in operational configuration  113 , as illustrated in  FIGS. 3B, 4B . As illustrated, wound interface  115  is secured to skin surface  111  to enclose a wound bed, such as wound bed  213 ,  313 ,  413 , within enclosed space  117  that is fluid tight. Wound therapy apparatus  100  may be placed in operational configuration  113 , as illustrated in  FIGS. 3B, 4B  when the wound bed is no-longer exuding exudate  152 , for example, in later stages of healing of the wound bed. Operational configuration  113  excludes reservoir  150  including reservoir housing  120  from control group  130 , as reservoir  150  including reservoir housing  120  may not be needed, in this implementation. Filter  124  may be included in controller group  130  in operational configuration  113  to capture stray liquids, in certain implementations. 
     As illustrated in  FIG. 4B , output fluid  118 , propelled, at least in part, by pump  168 , flows from the enclosed space  117  of wound interface  115  through connector  188  of control package  160  of control group  130 , through valve  172 , and through pump  168 . Output fluid  118  is then exhausted into the atmosphere on the discharge side of pump  168 , in this implementation. Input fluid  116  may flow from either gas source  112  or atmosphere  127  to the enclosed space of wound interface  115  in operational configuration  113  as described with respect to operational configuration  111  illustrated in  FIGS. 3A, 4A . In operational configuration  113 , controller  165  interacts with valves  172 ,  173 ,  174 , pressure sensors  176 ,  178 , and pump  168  to control the flow of input fluid  116  and output fluid  118 , for example, in order to cause actual pressure p a  to proximate target pressure p 0  within the enclosed space or to deliver air  128  to the wound bed. 
     Connector  188  forms a point of attachment between reservoir housing  120  and control package  160  so that reservoir housing  120  and control package  160  are removably secured to one another at least at connector  188  in operational configuration  111 . Connector  188  forms a fluid pathway for flow of output fluid  118  from reservoir housing  120  to control package  160  when reservoir housing  120  and control package  160  are removably secured to one another in operational configuration  111 . Reservoir housing  120  is absent from control group  130  in operational configuration  113 , and connector  188  provides a point for attachment of fluid conveyances between wound interface  115  and control package  160  to convey output fluid  118 , in operational configuration  113 . Connectors  182 ,  184 ,  186  provide points of attachment for various fluid conveyances to control group  130  that allow input fluid  116  and output fluid  118  to flow therethrough, in this implementation. 
     Reservoir housing  120  may be removed from securement to control package  160  by disconnection at least at connector  188 , and a new reservoir housing  120  may be removably secured to control package  160  at least by securement at connector  188 , in this implementation. Alternatively, reservoir housing  120  may be removed from securement to control package  160  by disconnection of at least at connector  188 , and fluid conveyances between wound interface  115  and control package  160  may be secured to connector  188  thereby placing wound therapy apparatus  100  from operation configuration  111  into operational configuration  113 , in this implementation. 
     As illustrated in  FIG. 5 , controller  165  is in operable communication with valves  172 ,  174 , pressure sensors  176 ,  178 , and pump  168  to vary actual pressure p a  within enclosed space  117  generally over the pressure range p min ≤p a ≤p max  in correspondence to target pressure p 0  that may vary periodically within the pressure range p min ≤p 0 ≤p max  where p min  is the minimum value of target pressure p 0  and p max  is the maximum value of target pressure p 0 . 
     In various implementations, p min ≤p amb  where p amb  is the ambient pressure of atmosphere  127  proximate wound therapy apparatus  100 . In various implementations, p max ≥p amb . In certain implementations, p max ≤p amb . The minimum pressure may be, for example, p min ≈p amb −130 mm Hg. The minimum pressure may be, for example, p min ≈p amb −90 mm Hg. The minimum pressure p min  may be, for example, within the pressure range (p amb −130 mm Hg)≤p min &lt;(p amb −90 mm Hg). The minimum pressure p min  may be generally within the pressure range (p amb −90 mm Hg)≤p min &lt;p amb . In various implementations, the periodic variation of the target pressure p 0  may be generally within the pressure range p min ≤p 0 ≤p max  where p max &gt;p amb . For example, p max ≈(p amb +40 mm Hg). In some implementations, the maximum pressure p max  may be slightly less than ambient pressure p am , for example, generally within the range of p amb −5 mm Hg to p amb b−20 mm Hg. 
       FIG. 5  illustrates exemplary operational states  132 ,  134 ,  136  of wound therapy apparatus  100  as target pressure p 0  is varied periodically within the pressure range p min ≤p 0 ≤p max , and wound therapy apparatus  100  may be varied between operational states  132 ,  134 ,  136  to cause the actual pressure p a  to correspond to target pressure p 0 . Operational states  132 ,  134 ,  136  are exemplary, not limiting, so that wound therapy apparatus  100  may be placed in operational states other than operational states  132 ,  134 ,  136 . Note that wound therapy apparatus varies sequentially between operational states  132 ,  134 ,  136  so that, for example, operational states  132 ,  136  do not exist simultaneously.  FIG. 5  excludes humidity source  114 , and reservoir  150  for clarity of explanation, so that  FIG. 5  is illustrative of the operation of wound therapy apparatus  100  in both operational configurations  111 ,  113 . Valve  173 , which is also omitted from  FIG. 5  for clarity of explanation, is in the CLOSED position in exemplary operational states  132 ,  134 ,  136  illustrated in  FIG. 5 . 
     In exemplary operational state  132 , as illustrated in  FIG. 5  (indicated by dot-dash line in  FIG. 5 ), output fluid  118  is being withdrawn from enclosed space  117  of wound interface  115  to vary the actual pressure p a  in correspondence with target pressure p 0  toward minimum pressure p min  in order to achieve p a ≈p 0 =p min , or to remove exudate  152  from the enclosed space  117 . Pump  168  may be in an ON condition in operational state  132 . Output fluid  118  flows from enclosed space of wound interface  115  through valve  172 , which is in an OPEN position, propelled by pump  168 , and gaseous portions of output fluid  118  are discharged into the atmosphere  127  by pump  168 , as illustrated. Valve  174  is in a CLOSED position, so that no input fluid  116  is being input into enclosed space of wound interface  115  in operational state  132 , as illustrated. Pressure sensor  178  is in operative communication with the enclosed space of wound interface  115  to detect actual pressure p a  within the enclosed space  117  including output fluid  118 , in this implementation. The actual pressure p a  detected by pressure sensor  178  may be communicated from pressure sensor  178  to controller  165 , and controller  165  may position valve  172  between OPEN position and CLOSED position including positions intermediate of OPEN position and CLOSED position to achieve p a ≈p 0  as target pressure p 0  is decreased toward p min . Controller  165  may adjust operations of pump  168  including, for example, the speed of pump  168  in order to achieve p a ≈p 0  and to achieve p a ≈p 0 ≈p min . 
     In exemplary operational state  134 , as illustrated in  FIG. 5  (indicated by solid line in  FIG. 5 ), valves  172 ,  174  are both in CLOSED position, so there is generally no input of input fluid  116  into enclosed space  117  or withdrawal of output fluid  118  out of enclosed space  117 . For example, either p a ≈p 0 ≈p min  or p a ≈p 0 ≈p max  in the enclosed space  117  of wound interface  115 , in operational stage  134 . 
     While in general there is no input of input fluid  116  into enclosed space  117  of wound interface  115  and no withdrawal of output fluid  118  out of enclosed space  117  at operational stage  134 , it should be recognized that there may be some leakage into or out of enclosed space  117  of wound interface  115 . Accordingly, at operational state  134 , pressure sensor  176 , pressure sensor  178 , or both pressure sensors  176 ,  178  may detect actual pressure p a  within enclosed space of wound interface  115 , and the actual pressure p a  detected by pressure sensor  176 ,  178  may be communicated from pressure sensor  176 ,  178  to controller  165 . Controller  165  may position valves  172 ,  174 , alter pump  168  between the OFF state and the ON state, or adjust the operation of pump  168  or valves  172 ,  174  intermittently, for example, in order to maintain p a ≈p 0 ≈p min , to maintain p a ≈p 0 ≈p max , or to withdraw exudate  152  from the enclosed space  117  of wound interface  115  as needed, in exemplary operational stage  134 . 
     In exemplary operational state  136 , as illustrated in  FIG. 7  (indicated by dashed line), input fluid  116  is being input into enclosed space  117  of wound interface  115  to vary the actual pressure p a  in correspondence with the target pressure p 0  toward maximum pressure p max  in order to achieve p a ≈p 0 ≈p max . Input fluid  116  flows into enclosed space  117  of wound interface  115  through valve  174 , which is in OPEN position, and the flow of input fluid  116  into the enclosed space  117  is driven by pressure p s  at gas source  112 , in this implementation. Valve  172  is in CLOSED position, so that there is no output fluid  118  being withdrawn from enclosed space  117  of wound interface  115  while input fluid  116  is being input into enclosed space  117  in operational state  136 . Pressure sensor  176  is in operative communication with the enclosed space  117  of wound interface  115  including input fluid  116  to detect actual pressure p a  within the enclosed space  117  of wound interface  115  at operational state  136 , in this implementation. The actual pressure p a  detected by pressure sensor  176  may be communicated from pressure sensor  176  to controller  165 , and controller  165  may position valve  174  between OPEN position and CLOSED position including positions intermediate of OPEN position and CLOSED position in order to achieve p a ≈p 0  as target pressure p 0  is increased toward p max . Pump  168  may be in an OFF condition in operational state  136 . 
     Thus, as illustrated in  FIG. 5 , valves  172 ,  174  are positioned between the OPEN position and the CLOSED position to sequentially input the input fluid  116  into enclosed space  117  and withdraw output fluid  118  from the enclosed space  117 , meaning that withdrawal of output fluid  118  and the input of input fluid  116  does not occur simultaneously. Input fluid  116  may be being input into the enclosed space or output fluid  118  may be being withdrawn from the enclosed space but not the input of input fluid  116  simultaneously with output of output fluid  118 , in this illustrated implementation. Thus, valve  172  may be in the OPEN position simultaneously with valve  174  in the CLOSED position, valve  172  may be in the CLOSED position simultaneously with valve  174  in the OPEN position, or valve  172  may be in the CLOSED position simultaneously with valve  174  in the CLOSED position, but valves  172 ,  174  are never both in the OPEN position at the same time, in this illustrated implementation. 
     Pressure sensor  176  or other pressure sensor(s) disposed about control group  130  may, for example, detect that pressure p s  at gas source  112  is below some minimum value indicating that gas source  112  is exhausted. As another example, control group  130  may be disconnected from gas source  112 . Valve  174  may then be placed in the CLOSED position, and valve  173  may be altered between CLOSED position and OPEN position in lieu of valve  174  in order to alter wound therapy apparatus between operational states  132 ,  134 ,  136 . Air  128  from atmosphere  127  as regulated by valve  173  is then input into enclosed space  117 , for example to vary the actual pressure p a  in correspondence with the target pressure p 0  toward maximum pressure p max . 
       FIGS. 6A and 6B  illustrate wound therapy apparatus  200  at exemplary first stage of operation  236  and at exemplary second stage of operation  238 , respectively. As illustrated in  FIGS. 6A, 6B , wound therapy apparatus  200  includes wound interface  215  that is deformation resistant and defines enclosed space  217  that is fluid-tight to enclose wound bed  213  at skin surface  211  when wound interface  215  is engaged with skin surface  211 . Wound interface  215 , as illustrated, includes cover  240  slidably sealingly frictionally removably engaged with base  220 . Cover  240  may include at least transparent portions to allow visual inspection of wound bed  213  though cover  240 . Base  220  may include flange  209  around at least portions of an outer perimeter of base  220  that may provide structural support or sealing surface against cover  240 , as illustrated. 
     In other implementations, cover  240  and base  220  may be formed as a unitary structure or cover  240  may be engaged hingedly or engaged in other ways with base  220 . While wound interface  215  is illustrated as cylindrical in shape enclosing a circular region of skin surface  211 , it should be understood the structure, such as wound interface  215 , may assume other geometric shapes to enclose other geometrically shaped regions of skin  211  such as rectangular, polygonal, or ovoid, to enclose various shaped wounds, and may include other modifications such as to base  220  to fit skin surface  211  in various regions of the body, in various other implementations. In other implementations, one or more additional ports in communication with enclosed space  217  may be situated about the wound interface  215  for monitoring parameters within enclosed space  217 , communication of fluids with enclosed space  217 , or other therapeutic interventions with enclosed space  217 . 
     Base  220 , in this implementation, includes flange  229  around the entire perimeter of outer side  223  of base  220  generally at distal end  222  of base  220 . Flange  229  is secured to skin surface  211  by adhesive  290 , as illustrated in  FIGS. 6A, 6B , around the entire perimeter of base  220  to form fluid-tight enclosed space  217 , and wound boundary  212  is enclosed within enclosed space  217 . Flange  229  may be designed by thickness and/or polymeric material to be soft and conformable to enable sealing of wound interface  215  over a wound  213  in a fluid-tight manner while distributing forces on wound interface  215  from actual pressure p a  within enclosed space  217  over the skin surface  211 . 
     Adhesive layer  290  may optionally extend over portions of skin surface  211  to include all skin surface under and proximate to flange  229  at distal end  222 . When the adhesive is a medically suitable member of the cyanoacrylate class, such as N-butyl-2-cyanoacrylate (Histoacryl Blue), or octyl-2-cyanoacrylate (Dermabond), the layer of water-resistant adhesive coating over the peri-wound skin surface serves the additional function of protecting the normal skin from maceration, secondary to prolonged exposure to other fluids, such as exudate, proteolytic enzyme soaks or saline lavages, etc. Other medical adhesives, for example, acrylic, silicone and hydrocolloid may be used to secure flange  229  of wound interface  215  to the skin surface  211 . Other securements such as straps with hook-and-loop-type fasteners or cohesive bandages may also be employed in various other implementations to secure, at least in part, wound interface  215  to the skin surface  211 . Base  220  of wound interface  215  may be formed of any of various medical polymers including, for example, polycarbonate, polystyrene, polypropylene or ABS; and may further be associated with additional sealing structures such as an inflatably adjustable circumferential cushion between the base and the adhesive layer around the perimeter of the wound bed. 
     Port  242 , which is located about wound interface  215 , is in fluid communication with enclosed space  217  via lumen  245 , in this implementation. Lumen  245  of port  242  may be in fluid communication with a control group, such as control group  30 ,  130  of wound therapy apparatus  10 ,  100 , respectively, and the control group may control the input of input fluid  216  into enclosed space  217  or the withdrawal of output fluid  218  from enclosed space  217  via lumen  245 , in this implementation. 
     Input fluid  216  may be input into enclosed space  217  via lumen  245  of port  242 , as indicated by the arrow in  FIGS. 6A, 6B , for example, to regulate, at least in part, the actual pressure p a  within enclosed space  217 , to control the composition of the gaseous fluids within enclosed space  217 , or for various therapeutic purposes. Input fluid  216 , for example, may be input into enclosed space  217  to increase the actual pressure p a  within enclosed space  217  in conformance to increases in the target pressure p 0 . Input fluid  216  may include gas, such as gas  22 ,  125 , gas  22 ,  125  plus humidity  129  from a humidity source, such as humidity source  114 . Input fluid may include liquid, such as liquid  24 . 
     Output fluid  218  may include input fluid  216  and output fluid  218  may include exudate  252 , so that output fluid  218  may include liquid, gas, and combinations of liquid and gas from within enclosed space  217 . Input fluid  216  or output fluid  218  may include liquid, such as liquid  24 , that may have various therapeutic purposes. Output fluid  218  is withdrawn from enclosed space  217  through lumen  245  of port  242 , as illustrated, for example, to decrease the actual pressure p a  within enclosed space  217  in conformance to decreases in the target pressure p 0 , to remove exudate  252  from enclosed space  217 , or to remove liquid, such as liquid  24 , from enclosed space  217 . 
     A pad  250  may be deployed within enclosed space  217  to absorb and transfer exudate  252  away from wound bed  213 , and the pad  250  may be in fluid communication with port  242  to allow withdrawal of exudate  252  from wound bed  213  through the pad  250  and thence through port  242 . Pad  250  may be formed of materials with absorbent and fluid transfer properties so as to absorb exudate. These materials include, for example, open-cell foam composed, for example, of polyvinyl alcohol (PVA), polyurethane or other polymer foam. Pad  250  may be formed of various woven or non-woven fibers such as sodium carboxymethyl cellulose hydrofiber (Aquacel), or knitted fibers with hydrophobic polyester fiber predominant on outer surface and hydrophilic nylon fibers predominantly on the inside to serve as a conduit to fluid transfer. The hydrophobic polyester fiber wicks away liquid and prevents moisture buildup and secondary maceration of tissue with which pad  250  is in sustained contact. Depending on specific fluid management goal, whether to primarily transfer exudate to another location or primarily to absorb and fix the exudate locally, certain amounts of a super absorbent polymer (SAP), such as sodium polyacrylate, can optionally be included in pad  250 . A quantity of SAP is added to a closed-cell polyurethane may enable passage of liquid through the resulting matrix, thereby enhancing the absorbent and fluid transfer properties of the matrix. 
     Wound therapy apparatus  200  may be periodically varied between first stage of operation  236  and second stage of operation  238  by consecutive withdrawal of output fluid  218  from enclosed space  217  and input of input fluid  216  into enclosed space  217  via lumen  245  of port  242 . At exemplary first stage of operation  236 , as illustrated in  FIG. 6A , the target pressure p 0  equals the maximum pressure p max  (i.e., p 0 =p max ), the maximum pressure may be generally equal to ambient pressure p amb  (i.e., p max ≈p amb ), and the actual pressure p a  generally equals the target pressure p 0  (i.e., p a ≈p 0 ) within enclosed space  217 . Wound bed  213  is in a baseline state  293 , and is in spaced relation with pad  250  such that there is reduced contact or no contact between pad  250  and wound bed  213 . The gap, if any, between pad  250  and wound bed may vary depending on the shape, structure and material used to make pad  250 . As illustrated in  FIG. 6A , wound interface  215  defines entry  226  to enclosed space  217 , and the portions of wound bed  213  enclosed by enclosed space  217  may generally lie outside entry  226  in baseline state  293 . Capillary  296 , which is proximate wound bed  213 , is undilated in baseline condition  297  and conveys a baseline quantity of blood to wound bed  213  in baseline condition  297  at first stage of operation  236 , as illustrated in  FIG. 6A . 
     At exemplary second stage of operation  238  of appliance  200 , as illustrated in  FIG. 6B , enclosed space  217  is evacuated, in part, by withdrawal of output fluid  218  from enclosed space  217  through lumen  245  of port  242  so that the target pressure p 0 =p min  and the actual pressure p a  generally equals the target pressure p 0  within enclosed space  217 . Pressure p min  is less than ambient pressure p amb  (i.e. p min &lt;p amb ) by an amount sufficient to cause at least portions of wound bed  213  to be distended into enclosed space  217  through entry  226  in distended state  294 . At least portions of wound bed, or a greater portion of wound bed  213  than in first stage of operation  236  biases against pad  250  at second stage of operation  238 , as illustrated in  FIG. 6B . Pad  250  may thus effectively absorb and transfer exudate from wound bed  213  through lumen  245  as at least a portion of output fluid  218  at second stage of operation  238 . Pad  250  fluidly communicates with lumen  245  of port  242  so that exudate may be evacuated through and from pad  250  through lumen  245  as at least a portion of output fluid  218  via external suction applied to port  242 . Capillary vessels proximate the wound bed, such as capillary  296 , may be in a dilated state  298  when wound bed  213  is in distended state  294  at second stage of operation  238 , as illustrated in  FIG. 6B . 
     A problem, for example, is the clogging of the output tubing by exudate, leading to a falsely reassuring reading of target suction pressure being maintained by the control package when a much lower actual suction pressure, if any, exists at the wound site. By adding an additional port that is also in independent communication with enclosed space  217 , differential pressure readings can be obtained of the same enclosed space from the front end and back end of a pressure conduit system that may enable more accurate diagnosis, and may localize problem situation to allow more targeted solutions or prophylactic actions. The additional port may be situated a distance apart from the first port, with both ports in fluid communication with the wound. Furthermore, when a bolus of fluid is introduced via the second port to abruptly relieve the suction pressure within the enclosed space, such sudden one-way pressure relief may serve to blast purge exudate out of the suction port, from one end of the wound bed to the other, unclog tubing, maintain tubing patency, and help to maintain effective therapy. Using an irrigant as a liquid bolus provided added benefit of further rinses away any condensed exudate, cellular debris and keep lines open. When used in conjunction with a dressing system in which the input relief port is near one end of the absorbent pad and the suction port is near the other end, intermittent use of irrigant to relieve suction may extend the clinically serviceable life of such a dressing system not unlike a self-cleaning diaper in that exudate and cellular debris is rinsed away and the dressing is “refreshed”. Aside from replacement cost savings, other benefits may include a lower incidence of adhesive tape allergy which is often precipitated by the repeated and concomitant loss of a layer of epidermis with each dressing change; the epidermal layer insulates the underlying dermis layer from being exposed to the adhesive. 
       FIG. 7  illustrates wound therapy apparatus  300  including wound interface  315 . Appliance  300  includes structure  315 , and structure  315  includes covering  320  attached to skin surface  311  by adhesive  390  to enclose wound bed  313  at skin surface  311 , with the entirety of wound boundary  312  covered by covering  320 . Distal side  322  of covering  320  faces wound bed  313  with covering  320  in securement to skin surface  311  by adhesive  390  on at least portions of distal side  322  of covering  320 , thereby defining portions of enclosed space  317 . Enclosed space  317  includes at least portions of wound bed  313 , as illustrated. Dressing  350  is placed against wound bed  313  and sealingly covered by covering  320 , as illustrated, so that dressing  350  lies within enclosed space  317 , as illustrated. 
     As illustrated in  FIG. 7 , ports  342 ,  344  are in fluid communication with enclosed space  317  between distal side  322  of covering  320  and proximal side  324  of covering  320  by lumen  345 ,  347 , respectively. 
     Lumen  345 ,  347  in fluid communication with a control group, such as control group  30 ,  130  of wound therapy apparatus  10 ,  100 , respectively, and the control group may regulate the input of input fluid  316  into enclosed space  317  through lumen  345  and regulate the withdrawal of output fluid  318  from enclosed space  317  through lumen  347 , in this implementation. Exudate  352  migrates from wound bed  313  into dressing  350 , and exudate  352  may be withdrawn from dressing  350  as part of output fluid  318 , in this implementation. 
     For example, input fluid  316  may be input into enclosed space  317  via lumen  347  of port  342  and output fluid  318  may be withdrawn from enclosed space  317  via lumen  345  of port  344  as actual pressure p a  within enclosed space  317  is varied in conformance to target pressure p 0 . For example, target pressure p 0  may be periodically varied over the pressure range p min ≤p 0 ≤p max  where p min  is the minimum target pressure over the pressure cycle and p max  is the maximum target pressure over the pressure cycle, and the actual pressure p a  is conformed to the target pressure p 0 . 
       FIG. 8  illustrates exemplary wound therapy apparatus  400 . As illustrated in  FIG. 8 , wound therapy apparatus  400  includes wound interface  415 , and wound interface  415  includes member  420  with adhesive  490  coated on at least portions of distal surface  422  of member  420  for securing member  420  to skin surface  411 . When secured to skin surface  411 , distal surface  422  of member  420  encloses wound bed  413  at skin surface  411  within enclosed space  417 . Member  420  may be formed of various polymers such as, for example, polyurethane. Member  420  may be fluid-tight and member  420  may be deformation resistant. 
     As illustrated in  FIG. 8 , flange  414  of port  442  secures port  442  to member  420  for fluid communication with enclosed space  417  by lumen  445 . The flange may be adhesively secured to the underside of pad  420  via an aperture in pad  420  as shown, or it may be adhesively secured on the upper and outer surface of member  420  and fluidly communicate with the enclosed space  437  within the wound interface via an aperture or connecting passageway. 
     Input fluid  416  may be input into enclosed space  417  via lumen  445  of port  442  and output fluid  418  may be withdrawn from enclosed space  417  via lumen  445  of port  442 . Lumen  445  may be in fluid communication with a control group, such as control group  30 ,  130  of wound therapy apparatus  10 ,  100 , respectively. The control group may regulate the input of input fluid  416  into enclosed space  417  through lumen  445  and regulate the withdrawal of output fluid  418  from enclosed space  417  through lumen  445 , in this implementation, for example, to conform actual pressure p a  with target pressure p 0  as target pressure p 0  within enclosed space  417  is, for example, periodically varied according to a pressure cycle generally having a pressure range p min ≤p 0 ≤p max  where p min  is the minimum target pressure over the pressure cycle and p max  is the maximum target pressure over the pressure cycle. 
     As illustrated in  FIG. 5 , appliance  400  includes layers  460 ,  470 , and  480  within enclosed space  417 . Portions of layer  480 , as illustrated, are secured to distal side  422  of member  420 , and portions of distal side  482  of layer  480  are biased against skin surface  411  and wound bed  413 . Layer  470  is biased between layer  480  and layer  460  with distal side  472  of layer  470  biased against proximal side  484  of layer  480 , and proximal side  474  of layer  470  biased against distal side  462  of layer  460 . Layer  460  is biased between layer  470  and spacer  430  with proximal side  474  of layer  470  biased against distal side  432  of spacer  430 . Various numbers of layers, such as layers  460 ,  470 ,  480 , may be included in other implementations of appliance  400 , and the layers may be arranged in various ways, or certain layers omitted, depending on application. Different layers may have special characteristics and functions, such as, for example, liquid absorption, fluid transfer, and release of therapeutic substances. 
     Proximal side  434  of spacer  430  is secured to distal side  422  of member  420  within enclosed space  417 , in this implementation. Spacer  430  defines void  437  within spacer  430 , and spacer  430  maintains layers  460 ,  470 ,  480  in biased engagement with one another, as illustrated. Spacer  430  may generally be a bilayer polymer pouch with or without additional distribution channels within that may be created by localized bonding or welding  464 . It may optionally be welded at multiple points  464  in the bilayer space to limit distension of the void  437  when under pressure. The purpose of spacer  430  is to disperse input fluid  416  across the entire wound surface. Spacer  430  may have a variety of sizes and shapes such as circular, rectangular, ovoid, or starburst, with a perimeter that substantially approximates that of proximal side  464  of layer  460 . 
     Lumen  445  passes through port  442  and through proximal side  434  of spacer  430  into void  437 , and input fluid  416  may be communicated via lumen  445  into void  437  or output fluid  418  may be communicated from void  437  through lumen  445 . 
     For example, input fluid  416  may be communicated into void  437  through lumen  445 , and input fluid  416  may then disperse within void  437  so that essentially the same pressure actual pressure p a  exists throughout void  437 . Input fluid  416  may then flow from void  437  through spacer passages in distal side  432  of spacer  430 , such as spacer passage  435 , into layer  460 . The spacer passages may be evenly distributed over distal side  432  of spacer  430  so that input fluid  416  is evenly distributed over proximal side of layer  460  from void  437 . Input fluid  416  may then flow through layer  460 , through layer  470 , and through perforations, such as perforation  485 , in layer  480  to contact wound bed  413  as well as skin surface  411 . The perforations, which pass between proximal side  484  and distal side  482  of layer  480 , may be evenly distributed over layer  480  so that input fluid  416  is evenly distributed over skin surface  411  and wound bed  413 . Thus, for example, input fluid  416  may, for example, provide enhanced O 2  exposure, antibiotic rinse, or cytokines in the form of amniotic fluid to wound bed  413  and to skin surface  411 . The actual pressure p a  exists throughout enclosed space  417  including wound bed  413  and skin surface  411 , and input fluid  416  and output fluid  418  may flow throughout enclosed space  417  including layers  460 ,  470 ,  480  and through spacer  430 . The spacer  430  may optionally be structured more distally to be closer to or even adjacent the wound surface, in which case, spacer passages  435  may be present in both the distal and proximal sides of spacer  430 . 
     Exudate  452  may flow from wound bed  413  through layer passages, such as layer passages  485  in layer  480 , into layer  470 , from layer  470  into layer  460 , and from layer  460  through spacer passages, such as spacer passage  435 , into void  437 . Output fluid  418  including exudate  452  may flow from layers  480 ,  470   460  through spacer passages  435  into void  437 , and output fluid  418  may be withdrawn from void  437  through port  442  via lumen  445 , in this implementation. 
     In this implementation, layer  480  is formed of silicone, including similar materials with scar modulation properties, and wound bed  413  has the form of an incision with stitch  499 . Silicone, as used herein, includes siloxane, various polysiloxanes, silicone-like materials, and various combinations thereof that may be generally solid. Silicone may have the chemical formula [R 2 SiO] n , where R is an organic group. Silicone may include, for example, silicone polymers having an average molecular weight in excess of 100,000 (e.g., between about 100,000 and about 10,000,000). Examples may include, but are not limited to, crosslinked siloxanes (e.g., crosslinked dimethicone or dimethicone derivatives), copolymers such as stearyl methyl-dimethyl siloxane copolymer, polysilicone-11 (a crosslinked silicone rubber formed by the reaction of vinyl terminated silicone and (methylhydro dimethyl)polysiloxane in the presence of cyclomethicone), cetearyl dimethicone/vinyl dimethicone crosspolymer (a copolymer of cetearyl dimethicone crosslinked with vinyl dimethyl polysiloxane), dimethicone/phenyl vinyl dimethicone crosspolymer (a copolymer of dimethylpolysiloxane crosslinked with phenyl vinyl dimethylsiloxane), and dimethicone/vinyl dimethicone crosspolymer (a copolymer of dimethylpolysiloxane crosslinked with vinyl dimethylsiloxane). 
     Wound bed  413  may be any type of wound bed, and layer  480  may be formed of other polysiloxane or similar materials, in various other implementations. Perforations  485  may take a range of forms, ranging from small holes, crosses, to slits, and allow fluid exchange with wound bed  413  and skin surface  411  through layer  480 , to prevent maceration of skin  411 . 
     Layer  470  may include a layer of material that delivers therapeutics in a slow release manner. Such therapeutics may include antimicrobials such as antibiotic or silver formulations, local anesthetic for pain reduction, amniotic or placental derived cytokines and growth factors such as BMP, hemostatics and coagulants to stop bleeding, oxygen generating and releasing compounds, exo- or endothermic reagents, etc. 
     Layer  460  may be made of a variety of materials including cotton gauze, polyester or polyamide fibers, or open-cell foams of polyurethane or polyvinyl alcohol. These materials of layer  460  may aid in transfer of exudate  452  from the wound bed  413  to void  437  for removal through lumen  445 . Layer  460  may optionally include a super absorbent polymer such as sodium polyacrylate, especially when the intent is to lock the exudate  452  within layer  460 . 
     In operation of a wound therapy apparatus, such as wound therapy apparatus  10 ,  100 ,  200 ,  300 ,  400 , target pressure p 0  within an enclosed space, such as enclosed space  17 ,  117 ,  217 ,  317 ,  417 , of a wound interface, such as wound interface  15 ,  115 ,  215 ,  315 ,  415 , may be varied with respect to time t according to a pressure cycle, such as exemplary pressure cycle  500 ,  550 ,  600 ,  650 ,  700 ,  750 ,  800 ,  850 ,  900 ,  950  (see  FIGS. 9A, 9B, 9C, 9D, 9E, 9F, 9G, 9H, 9I, 9J , respectively) and the actual pressure p a  within the enclosed space of the wound interface may be conformed to the target pressure p 0  so that p a ≈p 0  by controlling the input of input fluid, such as input fluid  16 ,  116 ,  216 ,  316 ,  416  into the enclosed space of the wound interface, and by controlling the withdrawal of output fluid, such as output fluid  18 ,  118 ,  218 ,  318 ,  418 , out of the enclosed space of the wound interface using a control group, such as control group  30 ,  130 . The input fluid may be gas, such as gas  22 ,  125 , or liquid, such as liquid  24 , in various implementations. The output fluid may include exudate, such as exudate  19 ,  152 ,  252 ,  352 ,  452 , and any residual gas or liquid from a previous pressure cycle, or any combination thereof. 
     Exemplary pressure cycles  500 ,  550 ,  600 ,  650 ,  700 ,  750 ,  800 ,  850 ,  900 ,  950  are illustrated in  FIGS. 9A, 9B, 9C, 9D, 9E, 9F, 9G, 9H, 9I, 9J , respectively, in which the target pressure p 0  within the enclosed space of the wound interface is graphed as a function of time t. Although pressure cycles  500 ,  550 ,  600 ,  650 ,  700 ,  750 ,  800 ,  850 ,  900 ,  950  are describe in terms of target pressure p 0 , the actual pressure p 0  may generally corresponds to target pressure p 0  within the enclosed space, so that pressure cycles  500 ,  550 ,  600 ,  650 ,  700 ,  750 ,  800 ,  850 ,  900 ,  950  may be descriptive of the behavior of the actual pressure p a  within the enclosed space. Because the input fluid, in various implementations, has an O 2  concentration greater than atmospheric air, the wound bed is exposed to fluid with O 2  concentration greater than atmospheric air throughout the pressure cycles, in various implementations, which may increase the oxygen supply to the wound bed during therapy with resulting therapeutic benefits. The application of multiple pressure cycles to the wound bed with O 2  concentration greater than atmospheric air may increase the O 2  exposure of the wound bed and thus the time of oxygen therapy delivered to the wound bed. Note that pressure cycles  500 ,  550 ,  600 ,  650 ,  700 ,  750 ,  800 ,  850 ,  900 ,  950  are exemplary only and not limiting, and one or more of these exemplary pressure cycles, various combinations of these exemplary pressure cycles or other pressure cycles may be delivered to the wound bed within the enclosed space as controlled by the control group  130 , in various implementations. 
     The control group, in various implementations, includes a controller, such as controller  87 ,  165 , and the pressure cycle including period, amplitude, and other characteristics of the pressure cycle may be based upon data, such as data  74 , communicated to the controller from a user I/O, such as user I/O  86 ,  145 , by a user. Accordingly, the user may select the pressure cycle(s) to be delivered to the wound bed within the enclosed space, a sequence of the pressure cycles, and characteristics such as amplitude and period of the pressures cycles using the user I/O. The controller may have pre-programmed pressure cycles in memory, and the controller may include other programs or data in memory to determine the pressure cycle(s) from the data and to implement the pressure cycle(s) using a pump, such as pump  89 ,  168 , valve(s), such as valve  88 ,  172 ,  173 ,  174 , and pressure sensor(s), such as pressure sensor  91 ,  176 ,  178 , as may be included in the control group. 
     As illustrated in  FIG. 9A , pressure cycle  500  is initiated at time t 0  and target pressure p 0 =p max . Note that actual pressure p a  within the enclosed space as controlled by the control group may be generally equal to target pressure p 0  throughout pressure cycle  500  (i.e., p a ≈p 0 ). According to exemplary pressure cycle  500 , target pressure p 0  reduces linearly at rate S 1  from time t 0  to time t 1 , and then target pressure p 0  reduces linearly at rate S 2  between time t 1  and time t 2  reaching p min  at time t 2 . Target pressure p 0  is then maintained at p min  between time t 2  and time t 3 , and then target pressure p 0  increases linearly at rate  53  from p min  to p max  between time t 3  and time t 4 , as illustrated. Input fluid input into the enclosed space between time t 3  and time t 4  to increase the pressure p a  from p min  to p max  may have an O 2  concentration greater than that of atmospheric air. Accordingly, the wound bed may be exposed to O 2  at a concentration greater than that found in atmospheric air during successive pressure cycles  500  when the pressure in each such pressure cycle is increased by fluid having an O 2  concentration greater than that of atmospheric air. The wound bed, in this example, may, thus, be exposed to O 2  concentration greater than that of atmospheric air at pressure p max  between time t 3  and time t 4 . 
     The control group may reduce the actual pressure p a  between times t 0  and t 2  by withdrawal of output fluid from the enclosed space without any concurrent input of input fluid into the enclosed space. Similarly, the control group may increase the actual pressure p a  between times t 3  and t 4  by input of input fluid into the enclosed space without any concurrent withdrawal of output fluid from the enclosed space. Finally, there is no input of input fluid into the enclosed space and concurrent withdrawal of output fluid from the enclosed space between times t 2  and t 3 , in various implementations of pressure cycle  500 . Essentially no fluid is input into the enclosed space and essentially no fluid other than exudate, is withdrawn from the enclosed space between time t 2  and time t 3 , in various implementations of pressure cycle  500 . A controller, such as controller  480  of wound therapy apparatus  400 , may control the withdrawal of output fluid between times t 0  and t 2  and the input of input fluid between times t 3  and t 4 . 
     In pressure cycle  500 , for example, p max =p amb  and p min =p amb −85 mm Hg. The time period t 2 −t 0  may be approximately 40 s, and target pressure p 0  is then held at p min  for t 3 −t 2 =240 s, followed by time period t 4 −t 3 =80 s, so that the period of pressure cycle  500  is t 4 −t 0 =360 s (6 minutes or 10 pressure cycles per hour). In various other implementations, the control group may deliver, for example 12 pressure cycles per hour, 4 pressure cycles per hour, or 3 pressure cycles per hour, according to exemplary pressure cycle  500 . Slopes S 1  and S 2  may be selected to avoid creating pain and S 2  may be less than S 1 , as rapid decreases below p max  in target pressure p 0  may be painful. For example, decreasing the target pressure p 0  from ambient pressure p amb  to p amb −40 mm Hg over time period t 1 −t 0 =10 s with corresponding decrease in the actual pressure p a  may be generally pain free followed by decreasing the target pressure p 0  to p amb −85 mm Hg over t 2 −t 1 =30 s again to attempt to minimize pain. Note that pressure cycle  500  may be asymmetrical with time t 3 −t 0  being greater than time t 4 −t 3 . 
     In various other implementations, target pressure p 0  may change at a single constant rate between time t 0  and time t 2  (S 1 =S 2 ) or target pressure p 0  may change at three or more rates between time t 0  and time t 2 . Pressure cycle  500  may repeat starting at time t 4  (i.e. time t 4  is set to time t 0 ), or some other pressure cycle, such as pressure cycle  550 ,  600 ,  650 ,  700 ,  750 ,  800 ,  850 ,  900 ,  950  may then be initiated starting at time t 4 . Pressure cycle  500  may remain essentially unchanged over successive cycles, or various parameters of pressure cycle  500 , such as p max , p min , S 1 , S 2 , t 3  t 2 , t 4  to, may be altered over successive cycles. The control group may determine the various parameters of pressure cycle  500 , such as p max , p min , S 1 , S 2 , t 3  t 2 , t 4 −t 0 , using data communicated from the user I/O, the data being input into the user I/O by the user. 
     An exemplary pressure cycle  550  is illustrated in  FIG. 9B . Note that actual pressure p a  within the enclosed space as controlled by the control group may be generally equal to target pressure p 0  throughout pressure cycle  550  (i.e., p a ≈p 0 ). As illustrated in  FIG. 9B , pressure cycle  550  is initiated at time t 10  and target pressure p 0 =p min . Target pressure p 0  increases linearly at rate S 11  from time t 10  to time t 11  reaching p max  at time t 11 . Target pressure p 0  is then maintained at p max  between time t 11  and time t 12 , and then target pressure p 0  decreases linearly at rate S 12  from p max  to p min  between time t 12  and time t 13 , as illustrated. Input fluid input into the enclosed space between time t 10  and time t 11  in order to increase the actual pressure p a  from p min  to p max  may have an O 2  concentration greater than that of atmospheric air. Accordingly, the wound bed may be exposed to enhanced oxygen at actual pressure p a  greater than p min  for time period t 13 −t 10  in exemplary pressure cycle  550 . Because generally p amb ≤p max  the wound bed may be exposed to enhanced oxygen at actual pressure p a  generally greater than or equal to ambient pressure p amb  for time period t 12 −t 11 , in exemplary pressure cycle  550 . 
     The actual pressure p a  within the enclosed space may be increased between times t 10  and t 11  by input of input fluid into the enclosed space without any concurrent withdrawal of output fluid from the enclosed space. Similarly, the actual pressure p a  within the enclosed space may be decreased between times t 12  and t 13  by withdrawal of output fluid from the enclosed space without any concurrent input of input fluid into the enclosed space. The control group may control the input of input fluid between times t 10  and t 11  and the withdrawal of output fluid between times t 12  and t 13 . Finally, there is no input of input fluid into the enclosed space and concurrent withdrawal of output fluid from the enclosed space between times t 11  and t 12 , in various implementations of pressure cycle  550 . 
     In pressure cycle  550 , for example, p max =p amb +40 mm Hg and p min =p amb , approximately. The time period t 11 −t 10  may be approximately 40 s, and target pressure p 0  is then held at p max  approximately for t 12 −t 11 =240 s, followed by time period t 13 —t 12 =80 s approximately, so that the period of pressure cycle  550  is t 13 −t 10 =360 s (6 minutes or 10 pressure cycles per hour). The pressure p max  of pressure cycle  550  may be limited, for example in certain embodiments, by the ability of the adhesive, such as adhesive  190 ,  290 ,  390 ,  490  to secure the wound interface to a skin surface, such as skin surface  211 ,  311 ,  411 , under pressure Amax, which forces the wound interface  15  away from the skin surface. 
     Pressure cycle  550  may repeat starting at time t 13  (i.e., time t 13  is set to time t 10 ), or some other pressure cycle, such as pressure cycle  500 ,  600 ,  650 ,  700 ,  750 ,  800 ,  850 ,  900 ,  950  may then be initiated starting at time t 13 . Pressure cycle  550  may remain essentially unchanged over successive cycles, or various parameters of pressure cycle  550 , such as p max , p min , S 11 , S 12 , t 11 −t 10 , t 12 −t 11 , t 13 −t 12 , may be altered over successive cycles. 
     For example, in certain implementations, the control group may deliver several pressure cycles according to pressure cycle  550  and then a pressure cycle according to pressure cycle  500  so that the actual pressure p a  varies generally over pressures greater than ambient pressure p amb  to deliver enhanced oxygen (hyperbaric) to the wound bed and the actual pressure p a  varies over pressures less than ambient pressure p amb  that may remove exudate from the wound bed or reseal the adhesive of the wound interface to the skin surface. In general, several minutes of pressurized topical oxygen such as around 40 mm Hg, which is well below MAP (mean arterial perfusion pressure) may be beneficial. Pressure cycles  500 ,  550  may be combined, for example, so that time period t 13 −t 10  is about 4 minutes and time period t 4 −t 0  is about 2 minutes to deliver hyperbaric therapy to the wound bed for about ⅔ of the pressure cycle period of 6 minutes and to deliver suction therapy for about ⅓ of the pressure cycle period. When pressure cycles  500 ,  550  are so combined, the resultant pressure cycle is asymmetric with more time period spent delivering hyperbaric therapy and less time period spent delivering suction therapy, in this example. 
     Another exemplary pressure cycle  600  is illustrated in  FIG. 9C , and actual pressure p a  may be generally equal to target pressure p 0  throughout pressure cycle  600 . In exemplary pressure cycle  600 , target pressure p 0  decreases and increases continuously in a sinusoidal (non-linear) manner, as illustrated in  FIG. 9C , and, thus actual pressure p a  decreases and increases continuously in a sinusoidal manner. As illustrated in  FIG. 9C , pressure cycle  600  is initiated at time t 20  and target pressure p 0 =p max . In this implementation, target pressure p 0  decreases from time t 20  to time t 21  reaching p min  at time t 21 , target pressure p 0  then increases from p min  to p max  between time t 21  and time t 22 , and then pressure p 0  decreases from p max  to p min  between time t 22  and time t 23 . In exemplary pressure cycle  600 , target pressure p 0  decreases and increases continuously, as illustrated. Pressure cycle  600  may repeat any number of times. Pressure cycle  600  may remain essentially unchanged over successive cycles, or various parameters of pressure cycle  600 , such as p max , p min , or the period t 22 −t 20 , may be altered over successive cycles. In other implementations, the target pressure p 0  may increase in a sinusoidal manner, then maintained at a constant p max  for some time period, and finally decreasing in a sinusoidal manner. 
     Another exemplary pressure cycle  650  is illustrated in  FIG. 9D . In exemplary pressure cycle  650 , target pressure p 0  decreases and then increases continuously as a triangular waveform, as illustrated in  FIG. 7D , and actual pressure p a  may be generally equal to target pressure p 0  throughout pressure cycle  650 . As illustrated in  FIG. 9D , pressure cycle  650  is initiated at time t 30  and target pressure p 0 ≈p max . In this implementation, target pressure p 0  decreases linearly from time t 30  to time t 31  reaching p min  at time t 31 , and then target pressure p 0  increases linearly from p min  to p max  between time t 31  and time t 32  thus completing one pressure cycle. The next pressure cycle starts with target pressure p 0  decreasing linearly from time t 32  to time t 33  reaching p min  at time t 33 . In exemplary pressure cycle  650 , target pressure p 0  decreases and then increases continuously as a triangular waveform, as illustrated. Pressure cycle  650  may repeat any number of times. The input fluid input to increase the actual pressure p a  to p max  by the control group may include O 2  at a concentration greater than that found in atmospheric air, and such increased O 2  may be delivered several times in succession by successive waveforms thereby exposing the wound bed continuously to an oxygen rich environment. 
     Another exemplary pressure cycle  700  is illustrated in  FIG. 9E . As illustrated in  FIG. 9E , target pressure p 0  is altered stepwise (pulsatile) between p min  to p max  and actual pressure p a  within the enclosed space is altered in correspondence to target pressure p 0  throughout pressure cycle  700  by the control group. The stepwise increase in target pressure p 0  from p min  to p max  in pressure cycle  700  may blow any residual exudate out of lumen in communication with the enclosed space, such as lumen  245 ,  345 ,  347 ,  445 , including fluid pathways in communication with the lumen in order to eliminate blockages caused by solidification therein of exudate including medicaments and other materials that may solidify. 
     It is a commonly encountered problem for the thick proteinaceous exudate from the wound bed to become increasingly concentrated, forming a plug and occlude the lumen including fluid pathways in communication with the lumen. When this happens, not only does exudate withdrawal cease, the exudate plug interferes with pressure sensing. This impedes therapy and the entire wound interface may have to be changed prematurely, assuming medical personnel are available to do so, resulting in increased cost and added pain to the patient. In order to solve this problem, in various implementations, the end of a pressure cycle may be initiated by a sudden or abrupt release of pressure prim, towards ambient pressure p amb  by the infusion of a bolus of gas or liquid This may prevent the creation of line-occluding exudate plugs, or if they do form, result in the forced expulsion of an exudate plug by pressure alone or in combination with liquid dissolution. The result may be the elimination or prevention of intra-lumen occlusion and more accurate sensing and delivery of suction therapy. 
     In various implementations, the control group may deliver pulses of input fluid, in conformance to pressure cycle  700  to remove blockages from the lumen including fluid pathways in communication with the lumen or the enclosed space. This may maintain the patency of the suction tubing and enable accurate sensing of target pressure p 0  within the enclosed space. The magnitude of the step may be produced for example, by a high fluid flow rate or by a high-compliance reservoir balloon that is interposed between the fluid source and valve that regulates flow delivered to the enclosed space. The maximum pressure p max  should be less than pressure that could breach the fluid-tightness of the wound interface. This is dependent on a number of factors including the characteristics of the adhesive that is used to anchor the wound interface to the skin. In general, such pulsed maximum pressure p max  may be less than about 30-40 mm Hg above ambient pressure p a . 
     Another exemplary pressure cycle  750  is illustrated in  FIG. 9F . As illustrated in  FIG. 9F , target pressure p 0  decreases linearly from p max  to p min  and then target pressure p 0  increases exponentially (non-linearly) from p min  to p max . Actual pressure p a  may be generally equal to target pressure p 0  throughout pressure cycle  750 . In exemplary pressure cycle  750 , fluid with oxygen concentration greater than that of atmospheric air may be input between times t 52  and t 51  to increase the actual pressure p a  from p min  to p max , and the actual pressure p a  is then maintained constant at p max  for time period t 53 −t 52  to deliver oxygen to the wound bed at pressure p max  for time period t 53 −t 52 . The cycle  750  repeats starting at time t 53  with linear decrease in target pressure p 0  from p max  to p min  between times t 53  and t 54  followed by exponential increase in target pressure p 0  from p min  to p max , as illustrated in  FIG. 9F . 
     Another exemplary pressure cycle  800  is illustrated in  FIG. 9G . Actual pressure p a  may be generally equal to target pressure p 0  throughout pressure cycle  800 , and target pressure p 0  varies linearly from p min  to p max  and from p max  to p min , as controlled by the control group. Fluid with oxygen concentration greater than that of atmospheric air may be input by the control group between times t 60  and t 61  to increase the actual pressure p a  to maximum pressure p max . Target pressure p 0  and, thus, actual pressure p a  is maintained constant at p max  for time period t 62 −t 61 , for example to deliver oxygen at pressure p max  to the wound bed, in this exemplary pressure cycle. Target pressure p 0  is maintained constant at p min  for time period t 64 −t 63 , for example to withdraw exudate from the wound bed, in exemplary pressure cycle  800 . 
     Another exemplary pressure cycle  850  is illustrated in  FIG. 9H . As controlled by the control group, actual pressure p a  may be generally equal to target pressure p 0  throughout pressure cycle  850 , and target pressure p 0  varies sinusoidally from p max  to p min  and from p min  to p max , in exemplary pressure cycle  850 . Target pressure p 0  is maintained constant at p min  for time period t 72 −t 71  for example to deliver oxygen at pressure p max  to the wound bed, and target pressure p 0  is maintained constant at p max  for time period t 74 −t 73  for example to withdraw exudate from the wound bed, in exemplary pressure cycle  850 . 
     In exemplary pressure cycle  900 , illustrated in  FIG. 9I , target pressure p 0  decreases and increases continuously linearly in a sawtooth pattern, and actual pressure p a  may be generally equal to target pressure p 0  throughout pressure cycle  900 . Note that maximum pressure p max  is greater than ambient pressure p amb  in exemplary pressure cycle  900 . 
     In exemplary pressure cycle  950 , illustrated in  FIG. 9J , pressure p 0  is initially at p min  at time t 90 . The control group increases the actual pressure p a  in conformance with the target pressure p 0  from p min  to p max  between times t 90  and t 91  by input of input fluid as liquid into the enclosed space. The control group controls the inputting of liquid as the input fluid and withdrawal of the liquid as at least a portion of the output fluid, in this implementation. The liquid, which forms at least a portion of the input fluid in this implementation, may provide various therapeutic benefits. The liquid may include, for example, saline solution, proteolytic enzyme solution, biofilm degradation solution, antibiotic lavage, amniotic fluid, platelet-enriched plasma, antibiotic, anesthetic, or other liquid having therapeutic benefits. In various implementations, 50 cc or more of liquid may be input into the enclosed space between times t 90  and t 91 . The input fluid in the form of liquid remains within the enclosed space between times t 91  and t 92  to provide a therapeutic benefit to the wound bed, and the liquid is then generally withdrawn from the enclosed space including any pad, such as pad  250 ,  450  or dressing, such as dressing  350 , within the enclosed space as the actual pressure p a  in correspondence to the target pressure p 0  is decreased from p max  to p min  between times t 92  and t 93 . The therapeutic benefit may include debridement, in various implementations. 
     The decrease in target pressure p 0  between times t 92  and t 93  may mark the beginning of a pressure cycle such as, for example, pressure cycle  500 ,  550 ,  600 ,  650 ,  700 ,  750 ,  850 ,  900 . The decrease in target pressure p 0  from p max  to p min  between times t 92  and t 93  may remove 90% or more of the liquid from the enclosed space including any dressing, pad, or layers, such as layers  460 ,  470 ,  480 , disposed therein, in certain implementations. Time period t 92 −t 91  during which the liquid is within the enclosed space at pressure p max  may range, for example, from about 2 minutes to about 1 hour. Time periods t 92 −t 91  of less than 1 hour or time periods t 92 −t 91  of only a few minutes may prevent maceration particularly when the skin surface is coated with adhesive such as cyanoacrylate. No input of input fluid into the enclosed space or withdrawal of output fluid from the enclosed space may occur between times t 91  and t 92 , i.e., there is no flow through the enclosed space between times t 91  and t 92 , in some implementations. 
     In other implementations, liquid may pass through the enclosed space as input fluid and output fluid simultaneously i.e., the liquid is simultaneously input and withdrawn between times t 91  and t 92 . Pressure cycle  950 , for example, may be intermittently interposed between other pressure cycles, such as pressure cycle  500 ,  550 ,  600 ,  650 ,  700 ,  750 ,  800 ,  850 ,  900 , or pressure cycle  950  may be repeated several times in succession. 
     The wound therapy apparatus may deliver a therapy regimen to the wound bed. The therapy regimen may include a sequence of pressure cycles of the actual pressure p a  within the enclosed space in conformance to target pressure p 0 . The pressure cycles may be, for example, any of exemplary pressure cycles  500 ,  550 ,  600 ,  650 ,  700 ,  750 ,  800 ,  850 ,  900 ,  950  and the sequence of pressure cycles may include several consecutive pressure cycles. 
     Example I 
     Example I presents series of pressure cycles as used in exemplary wound therapy regimens delivered to the wound bed by the wound therapy apparatus. Example I demonstrates an exemplary application of these exemplary wound therapy regimens to wound therapy of the wound bed. 
     In this Example, the pad or the dressing may be omitted from the wound bed during at least portions of the healing process. The absence of the pad or dressing eliminates the need for dressing change and the associated pain and inhibition of the healing processes due to disruption of granulation tissue as well as the attendant costs for medical personnel and various consumables, and may allow for visual inspection of the wound bed and surrounding skin through transparent portions of the wound interface. Because no dressing or pad is used in this implementation, the wound therapy apparatus may be employed until complete healing of the wound bed is achieved. The absence of the dressing or pad, except, perhaps, in the initial exudative phase of wound bed, may permit, for example, lavage of wound bed as well as incubation of stem cells incubation of tissue stroma, proteolytic enzyme soaks, medical maggot debridement or a skin graft. The wound therapy apparatus may be employed until complete healing of the wound bed is achieved. 
     In Example I, N designates a pressure therapy according to exemplary pressure cycle  500  with gas having O 2  concentration greater than atmospheric air input into the enclosed space between times t 3  and t 4  to increase the actual pressure p a  within the enclosed space to p max . Note that humidity may be added to the gas or to other gas(es) in various pressure cycles to prevent drying of the wound bed. O designates a therapy according to exemplary pressure cycle  550  with O 2  input into the enclosed space between t 10  and t 11  in order to increase the pressure within the enclosed space to p max  with p max  being greater than ambient pressure p amb  in pressure cycle  550  as used in Example I. 
     Therapy Regimens which are groups of four pressure cycles (four therapies) are as follows:
         Therapy Regimen 1—N/N/N/N (four consecutive N therapies)   Therapy Regimen 2—N/N/N/O (three consecutive N therapies followed by one 0 therapy)   Therapy Regimen 3—N/O/N/O (N therapy alternating with O therapy)   Therapy Regimen 4—O/O/O/N (three O therapies followed by an N therapy that may reattached the wound interface to the skin surface)       

     If each pressure cycle (either O therapy or N therapy) is delivered over 6 minutes, for example, each Therapy Regimen is then delivered over 24 minutes allowing the Therapy Regimen to be delivered 60 times a day. In general, at the early phase of wound treatment, relatively speaking, more N therapy may be used, as in exemplary Therapy Regimen 1 and exemplary Therapy Regimen 2, in order to remove exudate, such as exudate  51 ,  151 ,  251 ,  351 ,  419 , and improve circulation. Once the exudative phase is over, the need for N therapy is diminished. At this point the therapy regimen may switch to N/O/N/O as in exemplary Therapy Regimen 3, and, lastly, O therapy would become the dominant therapy. An occasional N therapy may be interposed with a series of O therapies, as in exemplary Therapy Regimen 4, to reseat the wound interface onto the skin. An exemplary week of prescribed therapy Regimens may be:
         Days 1-2: Therapy Regimen 1   Days 3-4: Therapy Regimen 2   Day 5-6: Therapy Regimen 3   Day 7: Therapy Regimen 4       

     Therapy Regimen 1, which is all N therapy, is used at the initiation of wound therapy, per Example I, as interstitial edema with large quantities of exudate may be present. The negative target pressures p 0  of Therapy Regimen 1 may draw the exudate from the wound bed and may reduce the edema by withdrawing exudate from the wound bed that causes the edema. After two days of Therapy Regimen 1, the wound therapy changes from Therapy Regimen 1 to Therapy Regimen 2 that interposes O therapy with the N therapy. The use of gas having O 2  concentration greater than atmospheric air under target pressure p 0  generally greater than or equal to ambient pressure p amb  to deliver O 2  to the wound bed in the O therapy may aid in healing while the N therapy may continue to treat the edema by withdrawing exudate from the wound. 
     After two days of Therapy Regimen 2, the wound therapy changes from Therapy Regimen 2 to Therapy Regimen 3 that alternates O therapy with the N therapy as the wound continues to heal. The use of gas having O 2  concentration greater than atmospheric air in the O therapy may aid in healing while the continued N therapy may continue to treat the edema by withdrawing exudate from the wound. 
     Finally, at Day 7 per Example I, the wound therapy changes from Therapy Regimen 3 to Therapy Regimen 4, which is predominantly O therapy with one cycle of N therapy every four cycles. The negative pressures of the N therapy may re-adhere the wound interface to the skin thereby prolonging the life of the fluid-tight seal between the wound interface and the skin surface. 
     Depending on the duration and magnitude of O therapy, a possibility exists for the seal between the wound interface and skin surface to become threatened or even breached. Loss of integrity of the seal, which would allow inflow of outside air during subsequent suction cycles, may dehydrate wound tissue and be detrimental for wound healing. To prevent this occurrence, aside from selecting a suitable maximum pressure p max  and duration, ending a sequence of 0 therapy with at least a brief N therapy may allow the adhesive of the wound interface to be reseated and, thus, re-secured to the skin surface. The ratio of frequency of such negative pressure cycles in relation to the positive pressure cycles may be 1:1, 1:2 or some other suitable ratio depending on a number of parameters, including the duration and magnitude of the positive pressure cycle. 
     Once the wound interface is unable to maintain a fluid tight seal (typically due to skin shedding or adhesive failure), the wound interface may require replacement. Replacement is estimated to be once every 5 to 7 days depending on the location of the wound bed and individual variability. Note that a pressure cycle such as pressure cycle  950  may be included from time t 0  time in any of Therapy Regimen 1, Therapy Regimen 2, Therapy Regimen 3, Therapy Regimen 4 to provide liquid to the wound bed. The liquid may be, for example, saline solution, proteolytic enzyme solution, biofilm degradation solution, antibiotic lavage, amniotic fluid, platelet-enriched plasma, antibiotic, anesthetic, or other liquid having therapeutic benefits. 
     Thus, in Example I, the progression is from initial use of N therapy that treats edema, to a mix of N therapy with O therapy that both treats edema and promotes healing, and, finally, to predominantly O therapy that promotes healing as the wound bed heals and the edema subsides. For example, Therapy Regimen 4 may be used when the wound is at least halfway healed and there is no longer any significant exudate. 
     It is assumed in Example 1 for explanatory purposes that the wound bed heals progressively between Day 1 and Day 7. Of course, healing may require other than a week, and, accordingly, the various Therapy Regimens, such as Therapy Regimens 1, 2, 3, and 4, may be continued for various lengths of time and may be combined as appropriate depending upon the condition of the wound bed. Therapy Regimens 1, 2, 3, and 4, may be linked with one another or with other Therapy Regimens in various ways, in various implementations. In other implementations, the Therapy Regimens, such as Therapy Regimens 1, 2, 3, 4, may have other patterns of pressure cycles, for example, O/O/O/O/. The Therapy Regimens, in other implementations, may have various numbers and types of cycles, such as pressure cycle  500 ,  550 ,  600 ,  650 ,  700 ,  750 ,  800 ,  850 ,  900 ,  950 . 
     The wound therapy apparatus may deliver liquid into the enclosed space of the wound interface as directed by the control group the including controller, and the liquid may have various therapeutic purposes. Operations of the wound therapy apparatus may include selecting the liquid from a liquid source, such as liquid source  84 , as the input fluid. Operations of the wound therapy apparatus may include controlling the input of input fluid into the enclosed space of the wound interface or controlling the withdrawal of output fluid out of the enclosed space of the wound interface using the control group in ways appropriate to the therapeutic purpose. For example, liquid as input fluid may be input into the enclosed space and then withdrawn from the enclosed space as output fluid to irrigate the wound bed in order to remove bio-burden or to moisturize the wound bed. As another example, liquid as input fluid may be input into the enclosed space and allowed to remain within the enclosed space when the liquid has healing or antiseptic properties. As yet another example, liquid as input fluid may be input into the enclosed space and withdrawn from the enclosed space as output fluid in order to flush out various fluid pathways through which input fluid or output fluid are communicated. Input of liquid or withdrawal of liquid from the enclosed space may be user selected by data communicated to the controller using the user I/O. Input of liquid or gas may be user selected by data communicated to the controller  65  by the user using the user I/O. 
     Another exemplary method of use of the wound therapy apparatus is illustrated by process flow chart in  FIG. 10 . Operational method  2000  as illustrated in  FIG. 10  and the associated description is exemplary only. As illustrated in  FIG. 10 , operational method  2000  is entered at step  2001 . At step  2002 , the wound interface of the wound therapy apparatus is secured to the skin surface forming the enclosed space over the wound bed. At step  2003 , output fluid is withdrawn from the enclosed space thereby reducing the actual pressure p a  within the enclosed space until actual pressure p a  generally equals the minimum pressure p min . Actual pressure p a  within the enclosed space may then be maintained proximate minimum pressure p min  for time period T 1 , as per step  2004 . For example, time period T 1  may be about 3 to 5 minutes. At step  2005 , input fluid is input into the enclosed space thereby increasing the actual pressure p a  from minimum pressure p min  to maximum pressure p max . The input fluid input into the enclosed space at exemplary step  2005  to increase generally the actual pressure p a  from minimum pressure p min  to maximum pressure p max  comprises a gas with an O 2  concentration greater than that of atmospheric air. 
     At step  2006 , the maximum pressure p max  may be about ambient pressure p amb , the maximum pressure p max  may be greater than ambient pressure p amb , or the maximum pressure p max  may be less than ambient pressure p amb , in various implementations. Actual pressure p a  within the enclosed space may then be maintained proximate maximum pressure p max  for time period T 2 , as per exemplary step  2006 . For example, time period T 2  may be about 1-3 minutes. 
     As illustrated in  FIG. 10 , output fluid is withdrawn from the enclosed space at step  2007  to reduce the actual pressure p a  within the enclosed space until actual p a  generally equals the minimum pressure p min . Actual pressure p a  within the enclosed space may then be maintained proximate minimum pressure p min  for time period T 3 , as per step  2008 . Because the fluid input into the enclosed space at step  2005  comprises a gas with an O 2  concentration greater than that of atmospheric air, the wound bed is exposed to gas with an O 2  concentration greater than that of atmospheric air throughout steps  2006 ,  2007 , and  2008 , in exemplary operational method  2000 . 
     At step  2009 , input fluid is input into the enclosed space to increase the actual pressure p a  from minimum pressure p min  to maximum pressure p max . The input fluid at step  2009  comprises liquid, in exemplary operational method  2000 . 
     Output fluid is withdrawn from the enclosed space and input fluid is input into the enclosed space sequentially by the wound therapy apparatus in performing steps  2003 ,  2004 ,  2005 ,  2006 ,  2007 ,  2008  and  2009 , in exemplary operational method  2000 , so that either input fluid is being input or output fluid is being withdrawn. Input fluid is not input at the same time output fluid is being withdrawn in performing steps  2003 ,  2004 ,  2005 ,  2006 ,  2007 ,  2008  and  2009  of exemplary operational method  2000 . 
     At step  2010 , liquid is then passed through the enclosed space for time period T 4 . The liquid may be sequentially input into the enclosed space and then withdrawn from the enclosed space or the liquid may be simultaneously input into the enclosed space and withdrawn from the enclosed space, at step  2010 . Liquid may be input in pulses to purge blockages within various passages that fluidly communicate with the enclosed space, at step  2010 . At step  2010 , for example, the liquid may flush out the enclosed space including the wound bed and dressing, remove bioburden or exudate, cleanse the wound bed, hydrate the wound bed. At step  2010 , the liquid may be input and withdrawn by instillation (steady flow). The control group may limit the actual pressure p a  of the liquid within the enclosed space for example to about ambient pressure p amb  in order to prevent dislodgement of the wound interface. For example, when actual pressure p a  of the liquid within the enclosed space generally equals ambient pressure p amb  as detected by the pressure sensor, the control group may reduce or stop the input of liquid into the enclosed space. 
     Exemplary operational method  2000  then terminates at step  2011 . Exemplary method  2000  may be repeated any number of times with various combinations of steps  2003 ,  2004 ,  2005 ,  2006 ,  2007 ,  2008 ,  2009 ,  2010 . Note that minimum pressure p min  and maximum pressure p max  may change between steps  2003 ,  2004 ,  2005 ,  2006 ,  2007 ,  2008 ,  2009 ,  2010 , and times T 1 , T 2 , T 3 , T 4  as well as minimum pressure p min  and maximum pressure p max  may be altered during various repetitions of method  2000 . 
     Methods of wound therapy may include the step of engaging the wound interface with the skin surface around the wound bed thereby defining the enclosed space over the wound bed. Methods of wound therapy may include the steps of establishing fluid communication between the wound interface, the control group, the liquid source, and the gas source. Methods of wound therapy may include the step of regulating the input of input fluid into the enclosed space in sequence with regulating the withdrawal of output fluid from the enclosed space using the control group operably controlled by a the controller thereby altering the actual pressure p a  within the enclosed space in correspondence to target pressure p 0 , the pressure cycle having minimum pressure p mm  and maximum pressure p max , the input fluid comprising a gas having an O 2  concentration greater than atmospheric air. 
     Methods of wound therapy may include the step of removing exudate from the output fluid by flowing the output fluid through a reservoir, such as reservoir  81 ,  150 . 
     Methods of wound therapy may include the step of receiving data using the I/O interface in operable communication with the controller, and communicating the data to the controller thereby altering the pressure cycle or altering the input fluid between liquid and gas. 
     Methods of wound therapy may include the step of delivering a therapy regimen to the wound bed, the therapy regimen comprising a series of pressure cycles of the actual pressure p a  within the enclosed space. 
     Methods of wound therapy may include the step of delivering a therapy regimen to the wound bed, the therapy regimen comprising inputting liquid into the enclosed space and may include the step of withdrawing liquid from the enclosed space. 
     Methods of wound therapy may include the programmed delivery of various gasses and liquids to the wound bed as controlled by the controller. 
     Methods of wound therapy may include the step of delivering air to the enclosed space when other gasses and liquids are unavailable. Methods of wound therapy include the step of delivering gas to the enclosed space to produce actual pressure p a  within the enclosed space equal to ambient pressure p amb  in the event of power failure of the wound therapy device. The foregoing discussion along with the Figures discloses and describes various exemplary implementations. These implementations are not meant to limit the scope of coverage, but, instead, to assist in understanding the context of the language used in this specification and in the claims. The Abstract is presented to meet requirements of 37 C.F.R. § 1.72(b) only. The Abstract is not intended to identify key elements of the methods of use and of apparatus disclosed herein or to delineate the scope thereof. Upon study of this disclosure and the exemplary implementations herein, one of ordinary skill in the art may readily recognize that various changes, modifications and variations can be made thereto without departing from the spirit and scope of the inventions as defined in the following claims.