HK1105175B - Vacuum assisted tissue treatment system - Google Patents

Description

Treatment system for assisting tissue healing using vacuum

Technical Field

The present invention generally relates to tissue treatment systems. In particular, the present invention relates to a therapeutic system that utilizes vacuum to assist in the healing of open wounds.

Background

Available through Kinetic Concepts and its commercial suppliers located in Antonio town, TexasVacuum assisted open wound healing therapy has recently become widely used. Commonly assigned U.S. patent 4,969,880 issued to Zaierowski at 11/13/1990, and continuing and partially continuing U.S. patent 5,100,396 issued at 3/31/1992, U.S. patent 5,261,893 issued at 11/16/1993, and U.S. patent 5,527,293 issued at 6/18/1996, the disclosures of which are incorporated herein by reference. Further improvements and enhancements to vacuum assisted wound healing methods are described in U.S. patent 6,071267 issued to Zaierowski at 6.6.2000 and U.S. patents 5,636,643 and 5,645,081 issued to Argenta et al at 6.10.1997 and 7.8.1997, respectively, the disclosures of which are incorporated herein by reference. Additional improvements are disclosed in U.S. patent 6,142,982 issued to Hunt et al, 5/13/1998. In fact, healing is "vacuum assisted" (or "vacuum assisted") by the assignee and its parents) Application to commercial negative pressure wound therapyMechanical contraction of the wound and simultaneous removal of excess fluid may be involved.In this way, the therapy promotes the body's natural inflammatory process while reducing many of the known inherent side effects such as edema caused by the increased blood flow lacking the vascular structure necessary for proper venous return. As a result of which,therapy has been highly successful in promoting wound healing, healing many wounds previously thought to be difficult to treat.

The frequency with which negative pressure is applied to the wound and the frequency with which the pressure varies over time directly affect the rate of wound healing. The time-varying pressure that current vacuum therapy devices have not been able to provide is believed to greatly enhance the rate of wound healing. Similarly, rapid return to normal activity in a patient undergoing wound therapy may also increase the rate of wound healing, as increased physical activity is often accompanied by increased blood circulation, which may result in improved blood flow at the wound. One of the obstacles to restoring normal mobility is limited battery life, which is a problem with the power supplies of existing vacuum assisted wound healing therapy systems. In addition, wounds require frequent inspection to ensure that the wound is not infected. Moreover, the rapid restoration of normal mobility also has to be faced with the precautions that vacuum therapy must take, setting up devices to prevent inadvertent spillage of wound exudates from the filter cartridge or entry of wound exudates into the pump.

The use of prior art fixed frequency oscillating pumps is further limited. These limitations are caused by the reduced battery life resulting from the pump size required to maintain the desired negative pressure at the wound site and/or the power required to operate the oscillating pump. Prior art oscillating pumps are generally designed to operate under defined operating conditions, for example, low pressure flow maximization at a fixed frequency. Typically, varying the resonant frequency of the pump under design conditions varies the mass and/or stiffness of the various components. If the pump pressure increases, the stiffness of the system increases due to the increased back pressure of the oscillating pump diaphragm. The resonant frequency change and fixed frequency drive of the pump do not drive the pump at an optimal frequency. As a result, the flow rate drops rapidly and the ability of the pump to drive air at high pressure is limited. Thus, when using a fixed frequency oscillating pump, to provide a higher flow at high pressure, either the flow at low pressure is sacrificed or the pump is made larger in size.

For the foregoing reasons, there is a need for a vacuum assisted wound healing therapy system that is capable of automatically performing pressure changes over time. In addition, there is a need for a more effective vacuum assisted wound healing system that allows the patient greater mobility while reducing the risk of exudate spillage or pump contamination.

Disclosure of Invention

It is therefore an object of the present invention to provide a vacuum assisted wound healing therapy system which provides means for providing a time varying pressure to enhance tissue growth stimulation.

Another object of the invention is to propose a system that can operate for a long time in the absence of an alternating current power supply.

It is a further object of the present invention to provide a filter cartridge and a cost effective means for sampling fluid drawn from a wound site without removing the filter cartridge or disturbing the wound.

It is a further object of the present invention to provide a vacuum assisted wound treatment apparatus which can be secured to an object to reduce the possibility of interference with the apparatus while having an arrangement which is convenient to operate.

In accordance with the above objects, the present invention generally comprises a porous pad substantially insertable into a wound site and a dressing for hermetically sealing the porous pad at the wound site. The distal end of the catheter is connected to the dressing to provide negative pressure to the wound site. A fluid sampling port is provided on the catheter for sampling wound exudate withdrawn from the wound site through the catheter. A source of negative pressure is in communication with the proximal end of the catheter. A collection cartridge is removably connected to the conduit to collect exudate drawn from the wound when negative pressure is applied. A first filter is disposed into the opening of the canister and a second filter is positioned between the canister and the negative pressure source. Since the source of negative pressure may be an electric pump powered by ac or dc power, the power management device cooperates with its associated power management program to maximize battery life when the unit is powered by dc power. The clamping mechanism is used to secure the system to a stationary object, such as a bedrail or a pole used to hang an intravenous fluid container.

The porous pad comprises a foam body, which is open at portions that need to be in contact with the cell growth promoting region but is open enough for drainage and negative pressure treatment to continue unabated, to avoid unnecessary adhesion. The porous pad is placed in fluid communication with a vacuum source to facilitate fluid drainage, as is known from the prior art. The porous pad of the present invention may be a polyvinyl alcohol foam. Fluid communication may be established by connection of a conduit to the dressing as disclosed in international patent application WO 99/13973 entitled "surgical towel and suction head for wound treatment", the contents of which are incorporated herein by reference.

When the porous pad is placed, an airtight seal is formed at the wound site to prevent loss of vacuum. Such a seal may be formed by placing a drape over the wound such that the drape adheres to healthy skin surrounding the wound while maintaining a gas seal around the wound.

A conduit or tube is disposed in fluid communication with the foam pad and has a distal end in communication with a fluid discharge cartridge, which is in fluid communication with a vacuum source. Constant or intermittent negative pressure therapy is performed as described in the prior art. Alternatively, the negative pressure may be varied over time to further stimulate cell growth, which may shorten the healing process. The negative pressure introduced into the wound is adjusted to meet different target pressures, which fluctuate between a maximum target pressure and a minimum target pressure.

The flow rate of the variable displacement pump used in the present invention can be maximized within a certain pressure range by varying the pump driving frequency. The optimum drive frequency can be continuously adjusted by the present system and the pump pressure can be periodically or continuously monitored to determine the optimum drive frequency at that pressure. The performance of the prior art variable displacement pump can be improved without increasing the size or weight of the pump. Similarly, the performance of a typical variable displacement pump can be achieved with a smaller pump, thus reducing the size and weight of the overall system, increasing patient convenience and portability. Another source of negative pressure, such as a fixed displacement pump, sometimes referred to as a positive displacement pump, may also be used.

A power management system is provided to maximize battery life when the present invention employs a dc power source. The power management device includes deactivating a backlight of the display or touch screen liquid crystal display control panel after a predetermined time interval. Battery life may be further extended when the power management system stops supplying power to the electric motor until the target energy setting is actually large enough to drive the motor. In this case, the motor is used to drive an electric pump to provide a negative pressure, as is known from the prior art.

According to another aspect of the present invention, there is provided a system for stimulating tissue healing, comprising: a porous pad; an airtight dressing; means for connecting the distal end of the discharge tube to the dressing; a filter cartridge removably connected to the proximal end of the drain tube; an independent pumping device capable of providing negative pressure to the wound; and means for managing the power supply to the independent pumping means.

According to yet another aspect of the present invention, there is provided a system for stimulating tissue healing, comprising: a porous pad; an airtight dressing; an electric pump capable of providing negative pressure to the wound; a filter cartridge removably connected to the means for providing negative pressure; a housing for holding the filter cartridge and providing negative pressure; a mechanism for securing the housing to a stationary object; and means for managing the power supply of the electric pump.

According to yet another aspect of the present invention, there is provided a system for stimulating tissue healing, comprising: a porous pad; an airtight dressing; means for providing negative pressure to the wound; means for managing the supply of power to the negative pressure means; and means for varying said negative pressure at certain time intervals.

According to another aspect of the present invention, there is provided a system for stimulating tissue healing, comprising: a porous pad; an airtight dressing; a swing pump capable of providing negative pressure to the wound; means for maximizing the pumping flow over a range of pressures; and means for managing the power supply to the oscillating pump.

The foregoing has outlined some of the pertinent objects of the present invention so as not to obscure the important features of the invention and the application of the invention. Many other advantageous results can be achieved by applying the invention in a different manner or by modifying the invention as described below. A full appreciation of the invention, and other objects thereof, can therefore be gained by reference to the following detailed description of the invention, which includes the preferred embodiments.

Drawings

These and other features and advantages of the present invention will be described with reference to the following drawings of preferred embodiments, which illustrate, but do not limit the invention, and in which like reference numerals represent similar parts, in which:

FIG. 1 is a schematic block diagram of a tissue treatment system according to the present invention;

FIG. 2a is a perspective view of a fluid sampling port according to the present invention;

FIG. 2b is a perspective view of another embodiment of a fluid sampling port according to the present invention;

FIG. 3a is a perspective view of the rear of a pump housing according to the present invention;

FIG. 3b is a perspective view of the front of the pump housing according to the present invention;

FIGS. 4a and 4b are flow charts of preferred steps performed by the power management system according to the present invention;

fig. 5 is a flow chart showing preferred steps for implementing pulse therapy in accordance with the present invention.

Detailed Description

While many different embodiments will readily suggest themselves to those skilled in the art, it is to be understood that, particularly after having read the description provided herein, that this detailed description is only illustrative of the preferred embodiments of the present invention, the scope of which is defined solely by the appended claims.

The present invention is a vacuum assisted healing therapy system that can be used to stimulate tissue healing.

Referring now specifically to FIG. 1, there is shown the major components of a system which may operate in accordance with the present invention. The present invention 10 includes a foam pad 11 that is substantially insertable into a wound site 12, and a dressing 13 that seals the foam pad 11 at the wound site 12. The foam pad 11 may be a polyvinyl alcohol (PVA) open cell polymer material, or other similar material having pore sizes capable of assisting wound healing. The hole density is preferably more than 38 holes per 1 inch of line length. The pore density is preferably between 40 and 50. Preferably 45 holes are provided 1 inch long per line. Such a pore density translates to pore sizes of about 400 microns.

The addition of a visualization agent, such as crystal violet, methylene blue, or similar agents known in the art, may cause the foam pad 11 to change color when acted upon by bacteria. In this manner, a user or health care provider can easily and conveniently determine whether an infection is present at the wound site 12. It is to be understood that the disclosing agent may also be disposed along the conduit line 16 between the wound site 12 and the filter cartridge 18. By this arrangement (not shown), the presence of bacterial contamination at the wound site 12 can be easily and conveniently determined without disturbing the wound, since the color change occurs almost immediately when bacterial infectious exudates from the wound site 12 are drawn through the conduit 16 when negative pressure is applied.

It is contemplated that the foam pad 11 may also be coated with a bacterial inhibitor. The addition of such inhibitors may limit and reduce the bacterial density at the wound site 12. Such inhibitors may be applied or adhered to the foam pad 11 prior to insertion into the wound, such as during sterile packaging. Alternatively, the inhibitor may be injected into the foam pad 11 after insertion into the wound site 12.

After insertion into the wound site 12 and sealing with the dressing 13, the foam pad 11 is placed in fluid communication with a vacuum source 14 to promote fluid drainage and wound healing, as known to those of ordinary skill in the art. The vacuum source 14 may be a portable electric pump, or a wall pump as in conventional health care facilities.

According to a preferred embodiment of the invention, the foam pad 11, the dressing 13 and the vacuum source 14 are provided in a manner known in the art, except for the modifications described in detail below.

The foam pad 11 preferably comprises a highly reticulated and open-celled polyurethane or polyether foam to more effectively penetrate wound fluid by suction. The mat 11 is preferably placed in fluid communication with a filter cartridge 18 and a vacuum source 14 through a conduit 16 of plastic or similar material. A first hydrophobic membrane filter 20 is interposed between the canister 18 and the vacuum source 14 to prevent wound exudates from contaminating the vacuum source 14. The first filter 20 may also serve as a fill sensor for the filter cartridge 18. When the fluid contacts the first filter 20, a signal is generated that is sent to the vacuum source 14, causing the vacuum source to be turned off. The dressing 13 preferably comprises an elastic material, at least peripherally covered with a pressure sensitive adhesive, to sealably cover the wound site 12. A vacuum seal is maintained at the wound site 12. The conduit 16 is arranged to be in fluid communication with the foam 11 via an attachment 17 which is bonded to the dressing 13.

According to a preferred embodiment of the present invention, a second hydrophobic filter 22 is disposed between the first filter 20 and the vacuum source 14. The provision of the second filter 22 is advantageous when the first filter 20 is also used as a fill sensor for the filter cartridge 18. In this case, the first filter 20 may act as a fill sensor, while the second filter 22 may prevent wound exudates from contaminating the vacuum source 14. This will divide the function into safety devices and control (or limiting) devices, allowing each device to operate independently. The odor filter 23, which may be an activated carbon filter, is disposed between the first filter 20 and the second filter 22 to eliminate malodorous gases from the wound exudates. In another embodiment, not shown, the odor filter 23 is disposed between the second hydrophobic filter 23 and the vacuum source 14. A second odor filter 15 may be disposed between the vacuum source 14 and the exterior discharge opening 25 to further reduce the escape of malodorous gases from the system. In another embodiment, first and second filters 20, 22 are allowed to be integrated with canister 18 to ensure automatic positioning of filters 20, 22, reducing exposure of the system to contaminants captured by filters 20 and 22, since at least one of the filters may be contaminated during normal use.

The device for sampling fluid can be operated by providing a resealable access port 24 in the conduit 16. The inlet port 24 is located between the distal end 16a of the catheter 16 and the proximal end 16b of the catheter 16. The access port 24, which is described in detail in fig. 2a and 2b, may be used to sample fluid drawn from the wound site 12. Although access port 24 is shown as an appendage protruding from catheter 16, it should be understood that a flush-mounted securement port (not shown) may be used for the same purpose. The access port 24 includes a resealable membrane 26 that remains sealed after penetration by a hypodermic needle. Various rubber-like materials known in the art that maintain a seal after piercing may also be used.

The process of sampling wound fluid of the present invention includes piercing the membrane 26 with a fluid sampler 28, such as a hypodermic needle or syringe. The sampler 28 enters the port 24 through the membrane 26 until it contacts wound exudate flowing in the lumen 30 of the catheter 16. One embodiment is disclosed in U.S. patent 6,142,982 to Hunt et al, 5/13/1998, the contents of which are incorporated herein by reference, and as shown in fig. 2B, inner lumen 30 may be surrounded by one or more outer lumens 31. The outer lumen 31 may be used as a pressure sensing channel to sense pressure changes at the wound site 12. In another embodiment, not shown, one or more of the outer chambers 31 may be used as a negative pressure passage, while the inner chamber 30 may be used as a pressure sensing passage. In the present invention, the fluid sampling port 24 communicates only with the inner chamber 30, and therefore does not interfere with pressure sensing at the outer chamber 31. In another embodiment (not shown), the outer chamber 31 serves as a negative pressure passage, and the fluid sampling port 24 communicates with the outer chamber 31.

The vacuum source 14 may comprise a portable pump located in the housing 32 as shown in fig. 3a and 3 b. A handle 33 may be formed or attached to the housing 32 to allow the user to easily grasp and move the housing 32.

According to a preferred embodiment of the present invention, the mechanism by which the housing 32 may be secured to a stationary object, such as an intravenous drip stand, is provided in the form of a clamp 34. The clip 34, which may be a G-clip as is known in the art, is retractable so that it can be placed back into the storage position of the recess 36 in the housing 32 when not in use. The clip 34 is extendable outwardly from the housing 32 through a hinge mechanism 38 to form a 90 degree angle with the storage position. In an embodiment not shown, the clamp 34 is allowed to be positioned 180 degrees from the storage position. The hinge mechanism 38 may lock into place after the clip 34 is fully extended, allowing the housing 32 to be suspended by the clip 30. A securing mechanism 40, such as a bolt, extends through an aperture 42 in the clamp 34 to adjustably secure the clamp 34 to various stationary objects of varying thickness.

Alternatively, the securing mechanism 40 may comprise a spring-actuated bolt or pin that is automatically adjustable in length to accommodate a variety of objects having different cross-sectional thicknesses, such as intravenous drip poles.

The present invention also allows for management of the power supply to the vacuum source 14 so as to maximize battery life when the present invention uses a dc power source. In a preferred embodiment, as shown in the flowchart of FIG. 4a, the motor controller 44 determines at step 46 whether the actual pressure is less than or equal to the target pressure. If the actual pressure is less than the target pressure, the tentative motor drive power required to reach the target pressure is calculated at step 48. If the tentative motor drive power is greater than or equal to the braking power at step 49, then the tentative motor drive power is actually applied to the motor at step 50. If the actual pressure is greater than the target pressure, the tentative motor drive power is reduced at step 52 and it is determined if additional power is needed to overcome the braking power. If it is determined that the tentative power is insufficient to overcome the braking power, the tentative power is not applied to the motor at step 54. If the tentative power is sufficient to overcome the braking power, then the tentative power is actually applied to the motor at step 50. The motor controller 44 functions as a closed loop system that continuously measures the actual pressure and compares it to a predetermined target pressure. The advantage of this system is that power can be prevented from being applied to the motor when it is not necessary to maintain the target pressure prescribed by the v.a.c. therapy. Battery life is extended because the motor is not unnecessarily energized when no power is applied.

Battery life may be further extended by automatically stopping the backlighting of the visual display 19 of the system 10 of the present invention (see fig. 3b) by way of an integrated software program provided in the computer processor, as shown in the flow chart of fig. 4 b. The user inputs information such as the desired target pressure or treatment duration at step 55 and activates the backlight of the visual display 19 shown in figure 3b at step 57. The user making the input at step 55 may simply touch the visual display 19, which may be activated by touch, or a pressure sensitive screen, as is known in the art. Actuating an alarm at step 55 may also activate a backlight of display 19 at step 57. If an air leak is found at the wound site 12, an alarm may be automatically activated. Such a leak may be indicated by detecting a pressure drop or decrease at the wound site 12. The backlight will remain activated until it is determined whether the previously set time interval has ended at step 58. If the time interval has not ended, the backlight activated at step 57 will be maintained. If the time interval has ended, the backlight will automatically disappear at step 59 until the user enters additional time information, or an alarm is sounded at step 55.

Referring back now to FIG. 1, when the pump 14 used in the present invention is an oscillating pump, battery life may be further extended by a variable frequency pump drive system 80. The pump drive system 80 includes a pressure sensor 82, a control system 84, and a variable frequency drive circuit 86. In a preferred embodiment, the pressure sensor 82 may detect the pressure of the pump, which is communicated to the system 84. The control system 84 determines the optimum drive frequency for the pump 14, and the pump 14 generates the pressure that the pressure sensor 82 measures and delivers. The optimum drive frequency for the pump 14 may be determined by the control system repeatedly or continuously. The control system 84 adjusts the variable frequency drive circuit 86 to drive the pump at the optimum frequency determined by the control system 84.

The use of the variable frequency pump drive system 80 also maximizes the pressure of the pump 14. In tests performed on the sample oscillating pump, changing only 30% of the drive frequency resulted in a double maximum pressure. In addition, the system 80 may maximize flow over a greater frequency range. As a result, pump performance is greatly improved over existing fixed frequency drive system pumps without increasing the size or weight of the pump. In turn, battery life is further extended, allowing the user greater mobility and freedom from being restricted to stationary power sources. Alternatively, a similar level as the prior art fixed frequency drive system pump can be achieved with a smaller pump. As a result, the mobility of the patient is improved by improving the portability of the unit.

The preferred embodiment also increases the stimulation of cell growth by pressure that varies with time, as shown in the flow chart of fig. 5. This pressure change is achieved by a series of calculations performed by a software program in conjunction with a computer processing unit that controls the vacuum source or pump functions. The program is initiated when the user, or healthcare worker for example, activates the pulse mode of the pump at step 60. The user then sets a target pressure maximum peak and a target pressure minimum peak at step 62. The software sets the pressure direction for "pressurization" at step 63. The software then enters a software control loop. In the control loop, the software first determines whether the pressure is increasing at step 64.

If the actual pressure is increasing at test 64, a determination is made at step 70 as to whether the modified target pressure is still less than the maximum target pressure. If the changed target pressure is still less than the maximum target pressure, the software next determines at step 66 whether the actual pressure has been equal to (increased to) the increased target pressure. If the actual pressure has reached the elevated target pressure, the software increases the varied target pressure by an interval at step 68. Or refrain from acting until the actual pressure has equaled the raised target pressure. If the varied target pressure has reached the maximum target pressure at test step 70, the software sets the pressure direction to "step down" at step 69 and the varied target pressure begins to move toward the lower portion of the swing cycle.

The separation may be measured in mmHg or in other pressure measurement units. The magnitude of the interval is preferably in the range of about 1 to 10mmHg, according to the user's choice.

If the actual pressure is decreasing at test 64, a determination is made at 74 as to whether the varied target pressure is still greater than the minimum target pressure. If the changed target pressure is still greater than the minimum target pressure, the software determines whether the actual pressure has reached (dropped to) the decreasing target pressure at step 76. If the actual pressure has been equal to the decreasing target pressure, the software increases the changing target pressure by an interval at step 72. Or refrain from acting until the actual pressure has equaled the reduced target pressure. If the varied target pressure has reached the minimum target pressure at test step 74, the software sets the pressure direction to "boost" at step 73, and the varied target pressure begins to move toward the upper portion of the swing cycle. This swinging process continues until the user does not select the pulse mode.

While the present invention has been described with reference to certain preferred embodiments, these embodiments are presented by way of example only, and are not intended to limit the scope of the present invention. Accordingly, the scope of the invention is to be limited only by the following claims.

Claims (15)

1. A system for stimulating healing of tissue, comprising:

a porous pad;

an airtight dressing;

a conduit;

means for attaching the distal end of the catheter to the dressing;

a filter cartridge removably connectable to the proximal end of the catheter;

an electric pump for applying negative pressure to the wound site;

a first hydrophobic filter positioned between the filter cartridge and the electric pump;

a second hydrophobic filter positioned between the first hydrophobic filter and the electric pump; and

an odor filter located between the first hydrophobic filter and the second hydrophobic filter or between the second hydrophobic filter and the electric pump.

2. The system of claim 1, wherein the first and second hydrophobic filters and the odor filter are formed as an integral part of the cartridge.

3. The system of claim 1, further comprising an inlet port for sampling wound exudates, the inlet port connected to the conduit and having a resealable membrane capable of maintaining a seal after being punctured.

4. The system of claim 1, further comprising a clamp for securing the system to a strut.

5. The system of claim 1, further comprising a portable housing for housing the electric pump, the system having a clamp for securing the system to a pole.

6. The system of claim 1, wherein the porous pad is comprised of an open cell polymer.

7. The system of claim 1, further comprising a power supply to supply power to the electric pump and a power management device for managing the power supply, the power management device including a mechanism to deactivate the display backlight after a predetermined interval.

8. The system of claim 1, further comprising a motor controller configured to determine a tentative motor drive power for reaching the target pressure and prevent application of electrical power to the motor when the tentative motor drive power is insufficient to start the electric motor.

9. The system of claim 1, wherein the conduit comprises a longitudinal branch that constitutes a discharge tube and a pressure sensing tube.

10. The system of claim 9, wherein a plurality of the detection tubes are disposed around the discharge tube.

11. The system of claim 9, further comprising a resealable inlet port for sampling effluent, said inlet port forming an attachment to said discharge tube.

12. The system of claim 1, wherein the electric pump is a variable frequency pump.

13. The system of claim 12, further comprising a pump drive system including a control system capable of determining an optimal drive frequency for driving the variable frequency pump to maximize pump flow.

14. The system of claim 12, further comprising a pump drive system including a pressure sensor for measuring a pressure of the pump.

15. The system of claim 13, wherein the pump drive system further comprises a variable frequency drive circuit that drives the pump at the optimal drive frequency.