Abstract:
A wound treatment system includes a housing that defines an oxygen outlet. An oxygen production subsystem is included in the housing and coupled to the oxygen outlet. A control subsystem is coupled to the oxygen production subsystem and configured to receive pressure information that is indicative of a pressure in a restricted airflow enclosure that is coupled to the oxygen outlet. The control subsystem then uses the pressure information to control power provided to the oxygen production subsystem in order to control an oxygen flow that is created by the oxygen production subsystem and provided through the oxygen outlet to the restricted airflow enclosure.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/738,905, filed Nov. 11, 2010, which is a national stage entry of PCT Application No. PCT/US09/02523, filed Apr. 23, 2009, which claims the benefit of U.S. patent application Ser. No. 12/288,873 (now U.S. Pat. No. 8,287,506), filed Oct. 24, 2008, which claims the benefit of U.S. Provisional Application No. 61/000,695, filed Oct. 26, 2007. The contents of each referenced application are hereby incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    This invention relates to tissue treatment systems, specifically to non-invasive tissue oxygenation systems for accelerating the healing of damaged tissue and promoting tissue viability. When skin is damaged a wound results and a four phase healing process begins. Optimal metabolic function of these cells to repopulate the wound requires that oxygen be available for all phases of wound healing. The more layers of tissue that are damaged the greater the risk for complications to occur in the wound healing process. 
         [0003]    Difficult-to-heal wounds encounter barriers to the wound healing process and typically experience delays in one or more of the last three phases of wound healing. One of the most common contributing factors to venous leg ulcers, diabetic foot ulcers and pressure ulcers experiencing delays in the healing process is the problem of chronic wound ischemia. Chronic wound ischemia a pathological condition that restricts blood supply, oxygen delivery and blood request for adequate oxygenation of tissue, inhibiting normal wound healing. 
         [0004]    In practice the standard of care for treating difficult-to-heal wounds typically involves the use of an advanced wound dressing or combination of advanced wound dressings providing a dressing treatment system. An advanced dressing is positioned on the wound site or on the wound site and the surrounding intact skin providing a wound site enclosure. An advanced wound dressing is typically comprised of materials having properties for promoting moist wound healing, managing wound exudate and helping control wound bioburden. The typical material components in combination further include properties for providing limited moisture vapor permeability. The lower the dressing&#39;s moisture vapor permeability or more occlusive the dressing the lower the amount of ambient air and the respective lower amount of oxygen is thereby available to the wound bed. 100% oxygen exerts a partial pressure of 760 mm Hg. Ambient air is comprised of about 21% oxygen thereby exerting a partial pressure of oxygen at about 159 mm Hg. A typical advanced wound dressing or wound dressing system comprised of lower moisture vapor permeable materials impacts the available oxygen for the wound site thereby limiting the partial pressure of oxygen at the enclosed wounds site at about 10 mm Hg to 60 mm Hg. Fresh air is provided to the wound site only when the dressing is changed. A dressing may remain covering the wound site for up to seven days before a dressing change is required. The moisture vapor permeability property of an advanced wound dressing providing a reduced oxygen wound environment thereby works against the optimal metabolic function of cells to repopulate the wound which requires that oxygen be available for all phases of wound healing. 
         [0005]    Prior art methods of tissue oxygenation for difficult-to-heal wounds include topical hyperbaric oxygen applied intermittently or continuously. Intermittent topical hyperbaric oxygen is a method of tissue oxygenation comprising of a sealed extremity or partial body chamber and a connected source of high flow pure oxygen whereby the affected limb or affected body area is positioned in a sealed extremity chamber or partial body chamber so that the oxygen source supplying the chamber is providing the patient topically up to 100% oxygen at flow rates that may exceed 300 liters per hour pressurizing the interior of the chamber up to 1.05% normal atmospheric pressure thereby increasing the available oxygen for cellular processing at affected wound site. During the oxygen application, the partial pressure of oxygen exerted inside the topical or partial body chamber may attain 798 mm Hg. Topical hyperbaric oxygen is applied for about 90 minutes. Prior art also teaches a plurality of methods to apply topically hyperbaric oxygen intermittently. A partial body chamber for treating sacral wounds has been described in U.S. Pat. No. 4,328,799 to LoPiano (1980) whereby oxygen is applied from a stationary supply tank into the interior of the chamber through connected tubing. A similar method of applying topical hyperbaric oxygen is described in U.S. Pat. No. 5,478,310 to Dyson-Cantwell (1995) whereby oxygen is applied from a stationary supply tank into the interior of the disposable extremity chamber through connected tubing. These and similar methods of applying intermittent topical hyperbaric oxygen are restrictive, cumbersome, can only supply oxygen to the affected area intermittently with no systemic application, and can only be applied with a minimal increase in atmospheric pressure (about 5%). Therefore the effect of the oxygen therapy on the wound can be minimal which is evidenced by the lack of commercial success from topical hyperbaric oxygen extremity chambers. 
         [0006]    Both U.S. Pat. No. 5,578,022 to Scherson (1996) and U.S. Pat. No. 5,788,682 to Maget (1998) describe disposable devices utilizing transmission of gases in ionic form through ion specific membranes to apply supplemental oxygen directly to the wound bed. These devices are described as battery powered, disposable, oxygen producing bandages and methods that are applied directly over the wound. They both include electrochemical oxygen generation using variations of the same 4 electron formula originally developed for NASA in U.S. Pat. No. 3,489,670 to Maget (1970). The amount of oxygen that can be applied to the wound is typically 3 milliliters per hour. Specific oxygen flow rates are generated by means of corresponding specific, preselected battery sizes and specific prescribed amperages. Prior art describes disposable devices are either “on or off.” The prior art describes disposable devices without means to sense temperature changes in the wound site oxygen environment. Prior art does not provide a means to deliver a varying (adjustable) oxygen flow rate without requiring the patient to obtain and apply a new device with a new battery having a specific amperage. Additional limitations are also associated with the use of a fixed non-variable oxygen flow rate. 
         [0007]    No prior art low dose tissue oxygenation device provides continuous oxygen adjustability to a patient&#39;s wound(s) creating a controlled hyperoxia and hypoxia wound environment for damaged tissue to accelerate wound healing and promote tissue viability. Specifically, nothing in the prior art teaches continuous oxygen adjustability based on actual flow rate, partial pressures at the wound site, and temperatures at the wound site. 
       SUMMARY 
       [0008]    The invention is an improved low dose tissue oxygenation device and wound monitoring system. The present invention generally comprises an oxygen delivery tube for placement at the wound bed and a wound dressing covering the tubing and wound site for restricted air flow enclosure. The tubing may have multiple holes at or near the distal end of the tubing. The tubing may include a generally flat, flexible, oxygen-permeable tape or membrane section attached at the distal end of the tube. The tubing may be flexible with a kink resistant inner lumen. The tubing may have a temperature sensor. The tubing may have a pressure sensor. The tubing may include a partial pressure of oxygen sensor. The proximal end of the tubing is connected to a source of oxygen. The proximal end of the tubing may have a port Leur-type locking mechanism for an airtight seal during application of the oxygen and for removal from the oxygen source during application a dressing. A source of oxygen is in communication with the proximal and distal ends of the tube. A source of oxygen may be an electrochemical oxygen concentrator supplied by alternating or direct current, a power management device and its power management protocol. The variable electrochemical oxygen concentrator is used in accordance with the present invention by varying the oxygen flow rate to meet varying target parameters at the wound site. The oxygen flow rate is adjusted by a system that periodically or continuously monitors the wound bed pressure and temperature environment or the tubing pressure and adjusting the oxygen flow rate in accordance to target set points. Adjusting oxygen flow in response to monitored changes in wound site oxygen and target oxygen pressure and temperature protocols provides a controlled hyperoxia wound environment which may shorten the healing process. 
         [0009]    In some embodiments, the device may have a backlight display terminal or touch screen liquid crystal display, a data input key pad or device function control buttons, a wound temperature monitoring system, a battery or oxygen pressure alarm system, a digital camera, a patient data input and memory system and/or a data port or wireless data access. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    A more complete understanding of the present disclosure and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying figures, wherein: 
           [0011]      FIG. 1  is a perspective view of an embodiment of a tissue oxygenation system of the present invention. 
           [0012]      FIG. 1A  is a cross section view of a wound site showing a distal end of a oxygen delivery tube of the present invention 
           [0013]      FIG. 2  is a side perspective view of the distal end of an embodiment of the tubing of the present invention showing a generally flat, flexible, oxygen-permeable tape or membrane section affixed to the tubing. 
           [0014]      FIG. 2A  is an end view of another embodiment of the tubing of the present invention. 
           [0015]      FIG. 3  is side elevation view of the distal end of the oxygen delivery tubing of the embodiment of  FIG. 2A  of the present invention 
           [0016]      FIG. 4  is a perspective view of a handset of the present invention. 
           [0017]      FIG. 5  is a flow chart illustrating the process of the present invention. 
           [0018]      FIG. 6  is a top plan view of the electrolyzer/concentrator of the present invention. 
           [0019]      FIG. 6A  is a side elevation plan view of the electrolyzer of  FIG. 6 . 
           [0020]      FIG. 6B  is an exploded perspective view of the eletrolyzer of  FIG. 6 .  FIG. 7  is a processor firmware flow chart of the present invention. 
           [0021]      FIG. 7  is a processor firmware flow chart of the present invention. 
       
    
    
       [0022]    While the present invention is susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION 
       [0023]    A preferred embodiment of the present invention, tissue oxygenation system for the healing of damaged tissue and to promote tissue viability, will now be described in detail with reference to the figures. 
         [0024]      FIG. 1  is a perspective view of several primary components of the present invention according to the preferred embodiment. The present invention includes a monitoring unit  10 , an electrochemical oxygen concentrator  11 , oxygen delivery tubing  12 , moisture absorbent dressing  14 , and vapor dressing  16 . Preferably, oxygen delivery tubing  12  is connected at the proximal end  15  of the long, kink resistant tubing to the monitoring unit  10 . The monitoring unit  10  has a small, lightweight housing which is portable and may be discretely worn by the patient in a pocket or attached to a belt. 
         [0025]    The monitoring unit  10  includes within the housing  13  a microprocessor  58  (see  FIGS. 5 and 7 ), a power management system  52 , pressure  56  and temperature  57  sensor interface(s), a flow rate sensor  54 , an input port  62  and a user entry port  66 . The electrochemical oxygen concentrator  11  is disposed within the housing  13 . The microprocessor  58  functions to control power, collect various readings from the flow, pressure, and temperature sensors controls ionic purification of room air by the electrochemical oxygen concentrator for delivery to the tubing, and controls the informational display on the monitoring unit  10 . Preferably, the microprocessor  58  is capable of receiving data through the user entry port and the input port, including information related to specific patients and re-programming information if there is a system malfunction with the device. 
         [0026]    As may be further seen in  FIGS. 1A and 2 , the distal end  17  of the tubing  12  has a soft, flexible, oxygen permeable tape or membrane section  29  placed on the damaged tissue or wound site  20  of a patient&#39;s limb  19  covered with a moisture absorbent dressing  14  and further covered by a reduced vapor pressure, permeable, occlusive dressing  16 . 
         [0027]    In a first embodiment, oxygen is delivered to the wound site  20  through a kink-resistant tube  12  connected at the proximal end  15  to the outlet of the oxygen concentrator at the monitor unit housing. On the distal end  17  of the tubing  12  is connected soft, flexible oxygen-permeable flat tape or membrane  29 . Extending through the lumen of the tube are several sensor wires  30  and  32 . These wires communicate from temperature sensor  30   a  and oxygen partial pressure sensor  32   a  disposed at the wound site to temperature  57  and pressure  56  transducers in the monitoring unit with the transducers providing input to the microprocessor  58  as would be understood by one of ordinary skill in the art. 
         [0028]    Alternatively, tubing  12   a  ( FIG. 2A ) preferably has several lumens, pressure  21  and temperature  19  sensors, and other such sensors as may be required to effectively monitor wound treatment, disposed therein. Specifically,  FIG. 2A  illustrates an end view of the tubing  12   a , and depicts a tubing with a length capable of connecting to the output side of electrochemical oxygen concentrator  11  housed within monitoring unit  10 . Such tubing lengths allow the monitoring unit to be worn discretely and continuously deliver oxygen to the wound site  20 . An inner lumen, or bore  18   a , of the tubing is a star like configuration to prevent kinking of the tubing and still allows oxygen flow if bent. The oxygen partial pressure sensor  19   a  at the wound site is disposed within the tubing and is in communication with a pressure monitoring system including transducer  58  allowing for oxygen flow rate adjustment, visual pressure display, and out of range alarm. A temperature sensor  21   a  is also disposed within the tubing at the wound site  20  and is in communication with a temperature monitoring system including transducer  57  allowing for visual display of temperature, an out of range alarm, and allowing for oxygen adjustment via the microprocessor  58  as is appropriate. 
         [0029]      FIG. 3  is a side view of the distal end of alternative tubing  12   a , which includes a plurality of holes  23  formed along the side of the distal end of the tubing to aid in the delivery of oxygen to the wound. In use, the oxygen flows F through the tubing to the wound site and may enter the wound bed through the multiple holes  23 . The oxygen may also flow through the distal end of star shaped lumen  18   a , however, the multiple holes at the distal end of the tubing allow for improved flow of oxygen to the wound site  20 . 
         [0030]      FIG. 1A  shows a wound site  20 , with the distal end  17  of the oxygen delivery tubing  12  having the oxygen distribution tape  29  placed over the wound site  20 . The tape  29  is placed centrally on the wound site for optimal delivery of oxygen to the damaged tissue. A moisture absorbent dressing  14  is placed at the wound site covering the tape end of the oxygen delivery tubing  12  and wound site. One skilled in the art will appreciate that moisture absorbent dressing is typical standard of care protocol for a difficult-to-heal wound. A reduced moisture vapor permeable dressing  16  covers the moisture absorbent dressing  14 , tape end of tubing  12  and wound site  20 , creating a restricted airflow enclosure. Preferably the reduced moisture vapor permeable dressing  16  is transparent and may be described to as an occlusive dressing. The occlusive dressing traps the oxygen over the wound site to create and maintain oxygen rich environment. The local partial pressure of oxygen at the wound site  20  may be increased from a low range of 10 to 60 mm Hg to an oxygen rich environment range of 200 to 760 mm HG. The increased available oxygen is metabolized at the cellular level and will stimulate an increase in growth factors, epithelialization, granulation tissue, glycosaminoglycan production, and collagen synthesis. The oxygen partial pressure at the wound site is communicated to the pressure monitoring transducer  57  in the housing  13 . The transducer supplies data to the microprocessor  58  which controls the power flow (amperage) to the concentrator  11 . The concentrator may increase or decrease the O 2  flow rate. 
         [0031]      FIG. 4  is a perspective view of a handset housing the major components of the present invention.  FIG. 5  is a flow chart of the present invention. 
         [0032]    As shown in  FIGS. 4 and 5 , in use, the monitor housing  13  draws in room air  50  with about 21% oxygen through the air inlet  40  by means of an electrochemical process. The room air passes through an ion exchange oxygen concentrator  11 , which concentrates the oxygen level of the room air to create a mixture that is 99% pure oxygen. The power management system  52  controls the electrical current supplied to the ion exchange oxygen concentrator  11 , thereby making the oxygen flow rate conform to the amount of current supplied to the ion exchange oxygen concentrator, i.e., increasing electrical current increases the electrochemical process and thereby increases the respective oxygen flow rate to the wound site  20  and decreasing the electrical current decreases the electrochemical process thereby decreasing the respective oxygen flow rate to the wound site. It should be noted that the power management system  52  includes lithium batteries (7.4 v) and a regulator which varies the amperage over a range from approximately 15 milliamps to approximately 150 milliamps. This range of current variation results in O 2  flow rates in the range of approximately 1.0 milliliters/hour to approximately 15.0 milliliters/hour. 
         [0033]    The concentrated O 2  then exits the housing through the oxygen delivery port  54 . The proximal end  15  of the oxygen delivery tubing  12  is connected with an oxygen delivery port  54  with Leur-type locking fitting. The locking fitting is engaged to maintain an airtight seal with the tubing. 
         [0034]    As illustrated in  FIGS. 2 and 5 , a pressure sensor  30   a  or  19   a  and a temperature sensor  32   a / 21   a  in the tubing  12  or  12   a  are in communication with a pressure transducer  56  and a temperature transducer  57 . The microprocessor  58  communicates with the power management system  52 , the pressure transducer  56 , and temperature transducer  57  adjusting the oxygen flow rate (sensed at sensor  54 ) to the wound site per programmed algorithms to optimally meet changes in the patients oxygen wound healing requirements. 
         [0035]    Turning to  FIGS. 6-6B , the electrochemical oxygen generator/concentrator  11  is illustrated.  FIG. 6  is a top plan view of concentrator  11  showing the cathode plate  70  overlaying the anode plate  72 .  FIG. 6A  is a side elevation view of the concentrator  11 . 
         [0036]    Each of the charged plates has a carbon backed metalized substrate with a titanium mesh plated on the carbon membrane. This provides a complete coverage area for electrical conductance to a Nafion® oxygen transfer membrane. Nation® is a registered trademark of DuPont and is a sulfonated tetrafluroethylene copolymer. Nation® is well known in the art as a proton conductor for proton exchange membranes (PEM). A Nafion 212 membrane is preferred in the present invention. 
         [0037]      FIG. 6B  is an exploded perspective view of the concentrator  11 . The PEM membrane  74  is compressed fully (40-60 ft-lbs force) between the cathode  70  and the anode  72 . To provide proper sealing of the concentrator, a gasket seal  76  may be utilized with flange bolting  78 . A  304 L stainless steel needle discharge valve  80  with viton seats is machined for attachment into the anode plate  72  using a viton O-ring (not shown). 
         [0038]    Electrical contact and transfer to the plates is accomplished by attaching a copper strip to the titanium mesh substrate. The compressive force applied provides the necessary adhesion to the surfaces of the two metals. The strips are then attached to the charge plates with epoxy. 
         [0039]    Ambient air enters the concentrator through inlet  82  which is covered by a polarized membrane  84  which allows water vapor to pass in one direction only and maintain the encapsulation of other gases (mainly hydrogen). The preferred membrane  84  in the present invention is a Gore-Tex® fabric. (Gore-Tex® is the registered trademark of W.L. Gore &amp; Associates.) Concentrated O 2  is discharged out discharge valve  80  which communicates with discharge  54  in housing  13 . 
         [0040]    A firmware flow chart for the present invention is illustrated in  FIG. 7 . When the monitoring unit  10  is started or powered up  90 , the microprocessor  58  calibrates  92  all sensors and the PEM cell. Because every PEM cell and each sensor has its own particular functional characteristics, the present invention calibrates the sensors and cell to ensure precise flow rates. 
         [0041]    If the calibration is successful  94 , then the microprocessor gets the desired  95  flow rate from the user. The microprocessor calculates the voltage and current to output from the PEM the set desired flow rate  96 . The microprocessor receives input from the flow rate sensor  54  and determines if the set flow rate has been reached  97 , if not the processor again seeks to recalibrate the sensors and the PEM cell. If the set flow rate is reached  97 , then the microprocessor enters a proportional control mode  98 . The flow rate may be adjusted based upon input from the temperature monitoring system and the pressure monitoring system. The microprocessor also displays the flow rate and the temperature on the monitor display screen  68 . 
         [0042]    In the proportional control mode, the microprocessor continuously tests the actual flow rate to ensure that it is maintained  99  using a feedback loop which looks at variations in sensor and PEM cell efficiencies. 
         [0043]    In another embodiment of the invention a wound monitoring system is contemplated. Patient data and therapy commands are communicated to the device by the care giver or patient for processing by means of a data input key pad  64  and function control buttons  65 . A data port  66  may be used to upload or download data. The monitoring system allows for collection and monitoring of key medical parameters to aid the caregiver in managing the patient care and potentially accelerate the healing process with improved access to more data. Available patient data and device functions are displayed and where appropriate are visually and audibly alarmed on the device function display screen  68 . A digital camera  69  may also be utilized to aid the monitoring process visually tracking the wound closure progress.