Apparatus and method for electrical treatment of wounds

Abstract

The present invention relates to electrotherapy of wounds. More particularly, a device for administering electrotherapy to wounds is provided. The device of the present invention is useful for treating any type of wound, and is particularly useful for promoting the healing of chronic wounds.

Description

[Technical Field]

[0001] The present invention relates to electrotherapy of wounds. More particularly, a device for electrotherapy of wounds and a method for administering electrotherapy to wounds are provided. The device and method of the present invention are useful for healing any type of wound, and are particularly useful for promoting the healing of difficult-to-heal or chronic wounds. [Background technology]

[0002] Chronic wounds, such as diabetic wounds, venous wounds, and pressure ulcers, cause pain and physical stress to the afflicted patient while incurring enormous economic costs to the healthcare system. Currently, the predominant method of treating chronic wounds is to apply bandages or wound dressings—i.e., bandages with healing factors incorporated therein—in combination with antibiotic treatment to prevent or combat infection. Such treatments are lengthy and often not particularly effective, so treating chronic wounds can take months or even years, during which time the patient's (and their family's) quality of life may decline. Because many patients suffering from chronic wounds are elderly with compromised immune systems, wounds significantly increase their risk of infection, thus leading to further complications and high healthcare system costs for their treatment. Other types of wounds, such as surgical wounds, can suffer from the same complications described above, and in such cases, reducing wound infection is equally important.

[0003] Electrical therapy has been demonstrated to promote blood flow and accelerate wound healing, making it an attractive alternative or adjunctive treatment. Because wound healing and blood flow promotion require longer treatment periods for the body to respond, the preferred method of administering the treatment is to embed electrodes into a dressing so that the dressing covers the wound while the patient continues with daily activities during the electrotherapy. The following electrotherapy methods constitute examples relevant in the art.

[0004] WO 2005 / 032652 relates to a dressing for treating damaged tissue, incorporating a pair of electrodes and a conductive gel between the electrodes. An electric current passes through the gel between the electrodes to repair the damaged tissue. A sensor may be incorporated into the dressing along with a control unit. The control unit may vary the current supplied to the electrodes according to environmental parameters detected by the sensor. Alternatively, one or more pre-defined programs may be stored in the control unit for supplying alternating currents of varying amplitude, frequency, and waveform to the electrodes.

[0005] WO 2009 / 060211 relates to a device for providing electrical stimulation to tissue from a control unit and at least one electrode connected to the control unit. A fixation element holds the at least one electrode against the tissue and holds the control unit in a fixed position relative to the tissue. The control unit is configured to supply current to the at least one electrode to stimulate the tissue.

[0006] WO 02 / 098502 relates to an electrode system for promoting wound healing. The device comprises a support structure with two electrodes attached to the support structure. One of the electrodes surrounds the other electrode on the support structure. The electrodes are attached to the wound and a potential difference is applied between the electrodes, causing a current to flow between the electrodes through the wound.

[0007] WO 2008 / 013936 relates to an electrode system for inducing wound healing. The system comprises two electrodes, a first electrode configured to be at least partially attached to the wound and a second electrode configured to be at least partially attached to the skin surrounding the wound and to a portion outside the wound. The system further comprises one or more feedback sensors for detecting the efficacy of the treatment and adjusting the electrical stimulation. The feedback sensors are connected to a control module, which can adjust the voltage based on the sensor output. The feedback sensors can be voltage sensors.

[0008] Even in light of the devices disclosed in the prior art, there remains a need for improved electrotherapy that promotes more rapid and efficient wound healing. DISCLOSURE OF THE INVENTION

[0009] Improved electrotherapy and / or further objects are achieved by a first aspect of the present invention, which relates to an electrotherapy method for wound healing, said method comprising: - providing at least two stimulation electrodes; - placing at least two stimulation electrodes in electrical contact with spaced apart areas of the skin surrounding the wound; - applying a pulsed direct current having a frequency of at least 5 kHz, such as at least 50 kHz, and a duty cycle in the range of 1% to 10% to the wound via at least two stimulation electrodes; Includes:

[0010] Electrical contact may be any contact formed between the electrode and the target tissue that allows for the conduction of electrical current through the skin. For example, this may be direct contact between the electrode's conductor and the tissue. It may also be indirect, such as when a conductive medium is placed between the electrode and the tissue. Without limiting the present disclosure to a particular medium, an example of such a medium may be a conductive hydrogel, which is well known for its use in electrocardiogram and ultrasound applications. For a given wound, the conductive hydrogel may cover the skin surrounding the wound.

[0011] The method is useful for treating any type of wound, and is particularly useful, but not limited to, for promoting the healing of chronic wounds, such as those caused by surgical infections, diabetic infections, surgical wounds such as those from cesarean section, trauma, venous infections, pressure ulcers, venous ulcers, diabetic foot ulcers, diabetic foot, and arterial ulcers. The method may also be relevant as a preventative treatment to reduce the risk of infection beforehand.

[0012] The electrodes can be any material with good electrical conductivity, such as metals or alloys such as platinum (Pt), gold (Au), copper (Cu), silver (Ag), iron (Fe), lead (Pb), or other conductive materials such as carbon.

[0013] The disclosed method allows electrical current to pass through a wound when stimulation electrodes are placed in electrical contact with the skin surrounding the wound. The current is supplied through the stimulation electrodes, and the current can flow from one of the stimulation electrodes, through the skin, through the wound, back through the skin, and to another stimulation electrode. When the current is applied to the wound by this method, an electric field created within the wound acts to enhance impaired physiological processes and promote wound healing, thus allowing the method to provide electrical therapy for the wound.

[0014] Because placing electrodes in or on a wound can interfere with wound scab formation and current wound treatment methods, being able to apply electrotherapy through the skin surrounding the wound may be preferable to applying electrotherapy directly to the wound itself. For example, in traditional wound treatment, a dressing may be applied to the wound to drain fluid from the wound or for a number of other functions. For efficiency, such dressings often need to be placed in contact with the wound itself. Therefore, placing electrodes on, in, or on the wound would prevent the dressing from contacting the wound, thereby hindering the effectiveness of the dressing. Because the disclosed method is used to apply electrotherapy to a wound through the skin surrounding the wound, it does not prevent the use of dressings placed in contact with the wound itself. Thus, the disclosed method allows both electrotherapy and traditional wound treatment to be performed simultaneously. Placing the stimulating electrodes on or around the skin around the wound can also make placement of the stimulating electrodes easier and less painful for the patient when they are placed and removed compared to when the electrodes are placed on, in, or on the wound itself. The ease of placing the stimulating electrodes is further relevant to the caregiver responsible for preparing the dressing, as little or no training is required to place and configure the electrodes on or around the skin around the wound.

[0015] In the context of this application, pulsed direct current is to be understood as direct current that alternates between periods of no voltage and periods of voltage, for example between 0V and 5V, 0V and 10V, 0V and 20V, and 0V and 50V.

[0016] The frequency of a pulsed DC current represents the number of cycles of voltage and no voltage per second. For example, if the pulsed DC current has a frequency of 2 Hz, the pulsed DC current has two periods of voltage and two periods of no voltage, such as 2 V for 0.25 seconds, then 0 V for 0.25 seconds, then 2 V for 0.25 seconds, and then 0 V for 0.25 seconds. The periods of voltage and no voltage do not need to be of equal duration; the relationship between the periods of voltage and no voltage can be within the range of 1:1.1 to 1:20, 1:1.5 to 1:10, or 1:2 to 1:5. Furthermore, the rise and fall of the voltage can be any suitable shape, such as a sawtooth wave, a square wave, a triangular wave, a sine wave, or a combination thereof. In one embodiment, the voltage is in the form of a square wave.

[0017] The DC signal may be, for example, a square wave (e.g., 10 kHz frequency, 10 V amplitude, and pulse-width modulated with a 10% duty cycle). When applied to a wound, the electrical pulse may be bandwidth-limited by impedance to make the electrical signal through the wound more sinusoidal. The signal may also be intentionally bandwidth-limited or shaped by other means, e.g., to have an extended rise time compared to a perfect square wave. A longer rise time reduces the unpleasant sensation caused by a sudden electrical stimulus. The current is preferably monopulse DC, flowing in a first direction between the electrodes and through the wound for a period of time, e.g., one minute to one hour. After this period, the current may be applied in the opposite direction. The purpose of the monopulse DC signal is to mimic the natural electrical stimulation that occurs in wounds, which may not be present in chronic or other severe wounds, e.g., those seen in elderly patients or those with chronic illnesses. In the context of the present concepts, the terms "mono" or "single-phase" used in the context of pulsed direct current (DC) are used interchangeably to mean that the current travels in one direction, as opposed to a two-phase system in which the current is supplied in two, or alternating, directions. Furthermore, the term "pulse" used in the context of DC is used to describe a periodic current that varies in amplitude. Pulses can occur individually or multiple times in succession.

[0018] At the frequencies used in this method, a low effective impedance is generated, allowing current to be applied to the wound without causing pain to the patient or animal being treated. Without being bound by theory, it is believed that the use of a high frequency pulsed direct current signal adequately mimics the natural electrical stimulation that occurs at or within the wound, while at the same time ensuring adequate penetration of the signal through the skin barrier.

[0019] Experiments using an AC voltage source at 2 Vpp have shown that when such current pulses (high-frequency pulses) are applied to the skin, the effective electrical impedance of the skin can be observed to be low. For pulses of 50 kHz to 500 kHz (2 μs to 20 μs), such low impedance values ​​were observed to be in the range of 144 ohms to 173 ohms. Therefore, the same effect would be expected for DC pulses of the same frequency. On the other hand, when the frequency of the current pulse is lower, e.g., 1 Hz to 1 kHz, the skin impedance values ​​are much higher, e.g., 1,000 ohms to 20,000 ohms. Therefore, the disclosed method advantageously allows a larger current to pass through the skin, which, without being bound by theory, improves the effectiveness of treatment. Additionally, the disclosed method allows for a rough determination of the voltage drop across the wound without taking into account the impedance differences of the skin surrounding the wound, which can vary widely.

[0020] Furthermore, experiments using an AC voltage source at 2 Vpp have shown that current pulses having frequencies in the range of 50 kHz to 500 kHz are painless, while current pulses having frequencies between 0.8 kHz and 3 kHz produce a direct sensation of pain. Thus, the disclosed method advantageously allows for the application of a therapeutic current that is painless and can be applied for extended periods of time, such as 0.5 to 12 hours, 0.5 to 8 hours, or 0.5 to 4 hours.

[0021] The current pulses may have a frequency in the range of 50 kHz to 500 kHz, 60 kHz to 400 kHz, 70 kHz to 300 kHz, or 80 kHz to 200 kHz.

[0022] In one embodiment, the electrotherapy comprises: - providing at least two sensing electrodes; - placing sensing electrodes on the skin at spaced locations around the wound; - measuring one or more voltage drops across the wound via a sensing electrode; - adjusting the voltage output to the wound via the sensing electrode based on the measurement of at least one voltage drop; Further includes:

[0023] By using at least two sensing electrodes for measurement (while applying electricity through the stimulating electrodes), the method of the present disclosure can be used to measure the voltage drop across the wound itself through the skin. By using at least two sensing electrodes for measurement, the measurement of unknown skin impedance can be eliminated, allowing for a more accurate measurement of the wound voltage drop. Furthermore, a differential measurement of the voltage drop can be made with the two sensing electrodes, reducing or eliminating common-mode noise. In this way, the method of the present disclosure allows for a more accurate measurement of the wound voltage drop.

[0024] The at least two sensing electrodes and the at least two stimulating electrodes may be formed by the same two electrodes. The device may include two electrodes, each of which is switchable between a stimulating electrode and a sensing electrode. In embodiments in which the device includes two electrodes, the device may further include a multiplexer that allows each of the two electrodes to switch between a stimulating electrode and a sensing electrode. In embodiments in which the device includes two electrodes, the two electrodes may function as sensing electrodes when performing a frequency sweep with a calibration voltage and subsequently function as stimulating electrodes that deliver current to the wound for electrotherapy.

[0025] When the stimulating and sensing electrodes are placed on the skin surrounding a wound, the measured voltage drop can depend on the electrical characteristics of the wound. Therefore, the disclosed method further enables regulated wound electrotherapy, where the voltage delivered to the wound can be adjusted based on the voltage drop, depending on the specific wound. Using this method, the voltage level can be adjusted to a level tailored to the specific wound being treated, and the resulting regulated electrotherapy can provide improved efficacy compared to unregulated electrotherapy. Because the electrodes are placed on the skin surrounding the wound, this method can be used for regulated electrotherapy tailored to the specific wound, and regulated electrotherapy is achieved without the device ever touching the wound itself. Therefore, the disclosed method can be used for regulated electrotherapy without interfering with conventional wound treatments applied to, on, or within the wound.

[0026] In one embodiment, the electrotherapy comprises: - measuring the current flowing between the stimulation electrodes; The adjustment of the voltage delivered to the wound via the stimulation electrodes is based on at least one measured voltage drop measurement and at least one measured current measurement.

[0027] When the stimulation electrodes are placed on the skin surrounding a wound, the level of current flowing through the stimulation electrodes depends on the electrical impedance or resistance of the wound. Thus, the disclosed method further enables tailored electrotherapy to the wound, where the voltage delivered to the wound by the stimulation electrodes can be further adjusted based on a current measurement that depends on the impedance of the particular wound. Using the measured current alone, or the measured current together with the measured voltage drop, the disclosed method can deliver tailored electrotherapy to the wound, where the voltage delivered to the wound by the device can be adjusted to a level tailored for the particular wound being treated. Tailored electrotherapy can result in improved wound healing efficiency compared to non-tailored electrotherapy.

[0028] In one embodiment, the stimulating and sensing electrodes are arranged to form pairs including at least one sensing electrode and at least one stimulating electrode, with the electrodes of each pair positioned within 5 mm to 50 mm of each other.

[0029] The sensing electrode may be positioned a suitable distance from the stimulating electrode supplying current to the wound so that a reliable measurement of the voltage drop is obtained and a suitable electric field for electrotherapy is obtained. The distance between the sensing electrode and the stimulating electrode may be in the range of 50 mm to 10 mm, 50 mm to 20 mm, 40 mm to 10 mm, 40 mm to 20 mm, 30 mm to 10 mm, or 20 mm to 10 mm.

[0030] In one embodiment, the voltage is adjusted so that the measured voltage drop is in the range of 50 mV to 350 mV per mm of wound distance.

[0031] Without being bound by theory, these voltage levels are believed to be particularly suitable and efficient for wound healing.

[0032] In another embodiment, an impedance value is calculated from one or more measured voltage drops and one or more measured current levels, and the voltage is adjusted so that the one or more measured voltage drops are within the range of 0.05 V to 1 V per ohm of the calculated impedance.

[0033] Without being bound by theory, this voltage level is believed to be particularly suitable and efficient for wound healing.

[0034] In one embodiment, the pulsed direct current has a duty cycle in the range of 1% to 50%. In a preferred embodiment, the pulsed direct current has a duty cycle of 1% to 4%.

[0035] In one embodiment, the pulsed direct current has a duty cycle in the range of 1% to 10%. In the context of the present invention, duty cycle can be understood as the percentage of the pulse period duration or pulse width relative to the total period of the waveform. A duty cycle in the range of 1% to 10%, especially in combination with the DC pulses described above, provides adequate electrical therapy to the wound. Such a duty cycle also prevents excessive pH buildup and heat generation in the wound and tissue during treatment.

[0036] Furthermore, the use of a duty cycle conserves power, extending battery life and total treatment time. The duty cycle may be within the range of 1% to 10%, 1% to 20%, 1% to 30%, 1% to 40%, or 1% to 50%. In a preferred embodiment, the pulsed direct current has a duty cycle within the range of 1% to 4%. In another embodiment, the pulsed direct current has a duty cycle of 2%. The inventors have discovered that pulsed direct current of at least 50 kHz, such as 100 kHz, and a duty cycle of 1% to 10% is suitable for electrotherapy of wounds.

[0037] In one embodiment, the electrotherapy method further includes increasing the peak voltage output to the wound via the stimulation electrodes from a first peak voltage level to a second peak voltage level.

[0038] In other embodiments, the electrotherapy further includes gradually and / or stepwise increasing the peak voltage output via the stimulation electrodes from a first peak voltage level to a second peak voltage level.

[0039] Immediate application of a target voltage level to a wound can be painful / uncomfortable to the mammal or patient. Having at least two voltage levels slows the flow of current into the skin / wound, thereby reducing pain and discomfort to the mammal. More steps over a longer period of time mean slower flow and potentially less pain and discomfort. Thus, applying voltage levels gradually or in stages provides less painful or uncomfortable electrotherapy.

[0040] In one embodiment, the electrotherapy further comprises maintaining a short period of time during which no voltage is output prior to the step of adjusting the voltage output.

[0041] In the context of the present concept, the short period of time during which no voltage is output may be any period deemed appropriate for the course of treatment, and may be determined by, for example, conditions such as wound size and location, patient health, battery life, and combinations thereof.

[0042] The electrotherapy of the present concept is suitable for wound healing treatment. A treatment course may be configured as a series of treatment time periods as well as voltage-free or rest time periods.

[0043] The treatment time period may be 5 minutes to 10 hours, 5 minutes to 5 hours, 5 minutes to 1 hour, 15 minutes to 45 minutes, 20 minutes to 40 minutes, e.g., 30 minutes. The treatment time period is the period of time that the electrical current for electrotherapy is applied to the wound.

[0044] The voltage-free period may be 5 minutes to 10 hours, 5 minutes to 5 hours, 5 minutes to 1 hour, 15 minutes to 45 minutes, 20 minutes to 40 minutes, for example, 30 minutes. The rest time period may have the same duration as the treatment time period. The rest time period is a period of time during which no electrical current for electrotherapy is applied to the wound.

[0045] Stopping the electrical treatment allows any electrical charge that may have accumulated in the wound during the electrical treatment to discharge.

[0046] In one embodiment, the average current applied to the wound through the stimulation electrodes may be in the range of about 1 mA to 10 mA.

[0047] Such currents are not damaging to tissue and result in currents suitable for electrotherapy. Limiting the method to this power level mitigates the application of harmful currents to the wound.

[0048] In one embodiment, the pulsed direct current applied to the wound via the stimulating electrodes has a frequency in the range of 50 kHz to 500 kHz, hi another embodiment, the pulsed direct current applied to the wound via the stimulating electrodes has a frequency in the range of 100 kHz to 500 kHz.

[0049] The inventors have discovered that using frequencies within the range of 50 kHz to 500 kHz, such as within the range of 100 kHz to 500 kHz, is effective in wound healing while minimizing stress and pain to the patient being treated.

[0050] In a second aspect of the present disclosure, there is provided an apparatus for electrical therapy, comprising a controlled voltage source connected to at least two stimulation electrodes configured to electrically connect with skin surrounding a wound, the controlled voltage source configured to output a pulsed direct current having a frequency of at least 5 kHz, such as at least 50 kHz, and the pulsed direct current having a duty cycle in the range of 1% to 10%.

[0051] The second aspect may achieve the same objectives as the first aspect and / or additional objectives.

[0052] In the context of this disclosure, the skin surrounding a wound should be understood as any area of ​​skin adjacent to or bordering the wound, and generally also as the skin up to 50 mm from the edge of the wound.

[0053] The electrodes may be any material with good electrical conductivity (conductor), such as metals or alloys such as platinum, gold, copper, silver, iron, lead, or other conductive materials such as carbon.

[0054] Electrical contact between the electrode and the skin surrounding the wound can be any contact between the electrode and the skin surrounding the wound that allows for the conduction of electrical current. For example, this can be direct contact between the electrode's conductor and the tissue. It can also be indirect, such as when a conductive medium is placed between the electrode and the skin surrounding the wound. Without limiting the present disclosure to a particular conductive medium, an example of such a conductive medium can be a conductive hydrogel, which is well known for its use in electrocardiogram and ultrasound applications. The conductive medium can also be an electrolyte solution. For a given wound, the conductive medium can cover the skin surrounding the wound or a portion of the skin surrounding the wound.

[0055] In the context of the present disclosure, an electrode configured to electrically contact the skin surrounding the wound should be understood to have or be configured to have a suitable surface for contacting the skin surrounding the wound, the surface being capable of electrically contacting the skin surrounding the wound. The suitable surface may be substantially flat and / or bendable or folded to form a shape with a surface that conforms to the curvature of the skin, as known from patches such as band-aids or cardiac monitoring electrodes. The electrode may have any shape, provided that the shape provides a suitable surface. The surface should be at least partially of a conductive material so that electricity is conducted through the electrode and to the skin on which the electrode is placed. A gel layer may be placed between the electrode and the skin to improve electrical contact.

[0056] The disclosed device allows electrical current to pass through a wound when stimulation electrodes of the device are placed in electrical contact with the skin surrounding the wound. The device supplies electrical current through the stimulation electrodes, and the current can flow from one of the stimulation electrodes, through the skin, through the wound, back through the skin, and to another stimulation electrode. When the device applies electrical current to the wound, an electric field created within the wound promotes wound healing, and thus the device can provide electrical therapy for the wound.

[0057] In one embodiment, the average current output from the controlled voltage source is limited to within the range of 1 mA to 10 mA.

[0058] Such currents generally do not damage tissue, resulting in currents suitable for electrotherapy. The device may be limited to these output levels to mitigate harmful current application to the wound. Peak current levels may be, for example, 10 mA or greater. Average current levels may be 2 mA to 8 mA, 3 mA to 7 mA, or 4 mA to 6 mA.

[0059] In one embodiment, the average peak voltage output from the controlled voltage source is limited to between 0.1V and 20V.

[0060] Such voltages generally do not damage tissue and result in currents suitable for electrotherapy. The device may be limited to these output levels to mitigate harmful current application to the wound. Peak current levels may be, for example, 10 mA or greater. Average peak voltage levels may be 0.2 V to 18 V, 0.3 V to 17 V, 0.4 V to 16 V, or 0.5 V to 15 V.

[0061] The inventors have discovered that pulsed direct current of at least 5 kHz, having an average current output of 1 mA to 10 mA and an average peak voltage output of 0.1 V to 20 V, may be particularly suitable for electrotreatment of wounds.

[0062] In one embodiment, the controlled voltage source is configured to output a pulsed direct current having a frequency in the range of 50 kHz to 500 kHz, and in another embodiment, the controlled voltage source is configured to output a pulsed direct current having a frequency in the range of 100 kHz to 500 kHz.

[0063] The inventors discovered that such currents provide an appropriately low impedance to model wounds while causing no pain to the mammal or patient being treated with the current. The inventors discovered that the use of an intermittent electrical signal, i.e., monophasic pulsed direct current with a duty cycle in the range of 1% to 10% and a frequency of at least 50 kHz, is sufficient to penetrate the skin barrier and provide excellent wound healing results. Without being bound by theory, it is believed that the use of monopulse direct current with a frequency of at least 50 kHz completely avoids the discomfort, such as itching, skin reaction, or muscle activation, typically associated with biphasic direct current or low-frequency current passing through the skin. Furthermore, treatment cessation, i.e., rest periods during which no current is delivered, ensures optimal battery life and avoids overstimulation of treated cells. Data supporting these observations are shown and discussed in Examples 1 and 2 and Figures 6, 7, and 8 provided herein. [Brief explanation of the drawings]

[0064] Embodiments of the present invention will now be described with reference to the enclosed non-binding drawings, in which: [Figure 1] FIG. 1 is a flow diagram illustrating an embodiment of a method in accordance with the present disclosure. [Figure 2] FIG. 2 shows an apparatus that can be used to perform the methods of the present disclosure. [Figure 3] FIG. 3 shows an exploded view of the patch of FIG. [Figure 4] FIG. 4 shows the patch of FIGS. 2 and 3 in an assembled state. [Figure 5] FIG. 5 shows a planar cross section of the device of FIGS. 2, 3, and 4 applied to the skin. [Figure 6]FIG. 6 shows representative light microscopy images of scratch assays of monolayer HaCaT cells exposed to electrical stimulation for 48 hours. [Figure 7] FIG. 7 shows representative light microscopy images of scratch assays of monolayer HaCaT cells exposed to electrical stimulation for 48 hours. [Figure 8] FIG. 8 shows a graph of the cell migration capacity of HaCaT cells exposed to electrical stimulation over a 48 hour period.

[0065] The present invention is described below in connection with specific embodiments. Those skilled in the art will recognize that the present invention may be implemented in several other applications and embodiments and is not specifically limited in its application to the specific embodiments depicted herein.

[0066] FIG. 1 is a flow diagram illustrating an embodiment of a method of the present disclosure. In a first step 101, two stimulating electrodes are provided. In a second step 102, the two stimulating electrodes are electrically connected to spaced apart portions of the skin surrounding the wound. In a third step 103, a pulsed direct current having a frequency of at least 5 kHz, such as at least 50 kHz, is applied to the wound through the two stimulating electrodes. In an optional fourth step 104, at least two sensing electrodes are provided. In an optional fifth step 105, the sensing electrodes are placed at spaced apart portions of the skin surrounding the wound. In an optional sixth step 106, a voltage drop across the wound is measured via the sensing electrodes. In an optional seventh step 107, the voltage output across the wound via the stimulating electrodes is adjusted based on the measured voltage drop.

[0067] 2 shows an apparatus that can be used to implement an embodiment of the present invention. A central unit 201, including a control module 201a, a voltage measurement circuit 201b, and a current measurement circuit 201c, is placed near a wound 207 and connected to two stimulating electrodes 204a and 204b and two sensing electrodes 205a and 205b via a cable 203. Cable 203 branches into two cables 203a and 203b, which are connected to the stimulating electrodes 204a and 204b and the sensing electrodes 205a and 205b, respectively, and optionally to support structures 206a and 206b. The sensing electrode 205a, the stimulating electrode 204a, and the support structure 206a form a patch 200p.

[0068] The central unit 201 may be controlled by at least buttons 202 on the central unit 201. Electrode pairs 204a and 205a and electrode pairs 204b and 205b are connected to support structures 206a and 206b, respectively, positioned on either side of the wound 207, with the sensing electrodes 205a and 205b closest to the wound 207. In this view, the support structures 206a and 206b are shown as transparent to show the electrode configuration. When activated, electricity is output by the central unit 201 and conducted across the wound 207 via cables 203, 203a, and 203b, through the stimulating electrodes 204a and 204b, and through the sensing electrodes 205a and 205b and the central unit 201 by a voltage measurement circuit. The control module 201a may calculate the appropriate output voltage based on the voltage and current measurements. The distance, such as the diameter of the wound, may be entered using the buttons 202 or by wireless interface. The entered value may be used by the central unit 201 to calculate the appropriate voltage output level.

[0069] Figure 3 shows an exploded view of the patch 200p of Figure 2. The patch 200p includes a support structure 206 and electrodes 204 and 205. The cable 203 includes two unshielded electrical wires 209a and 209b. When the patch 200p is assembled, the two electrical wires 209a and 209b are in electrical contact with the stimulating electrode 204 and the sensing electrode 205, respectively, and are sandwiched between the support structure 206 and the electrodes 204 and 205. A conductive gel layer 210 is located between each electrode 204, 205 and the optional removable film 208.

[0070] Figure 4 shows the patch 200p of Figures 2 and 3 in an assembled state. The removable film 208 optionally has a notch 208a to facilitate removal of the film. This embodiment may be cut across the width of the patch, for example, to shorten the length of the patch. Ideally, the length of the patch is cut to roughly match the dimensions of the skin surrounding the wound to be treated.

[0071] FIG. 5 shows a planar cross section of the patch 200p of FIGS. 2, 3, and 4 in an assembled state, with the removable film 208 removed and the conductive gel layer 210 in contact with the surface of the skin 211 surrounding the wound (not shown).

[0072] Figure 6 shows representative optical microscope images of the scratch assay described in Example 2, in which a monolayer of HaCaT cells was exposed to electrical stimulation under various conditions for 48 hours. The various conditions tested were: Condition A: 0 kHz pulse frequency, 100% duty cycle, and 200 mV / mm electric field; Condition B: 100 kHz pulse frequency, 2% duty cycle, and 200 mV / mm electric field; Condition C: 100 kHz pulse frequency, 4% duty cycle, and 200 mV / mm electric field; and Condition D: 100 kHz pulse frequency, 10% duty cycle, and 150 mV / mm electric field. Control group TIFF0007749590000001.tif11170 represents untreated, i.e., unstimulated, cells. Each condition was tested in triplicate, and the images shown in Figure 6 represent representative images of the general cell behavior observed in each condition. Images were acquired after 0, 12, 24, 36, and 48 hours of electrical stimulation. In all conditions, the electrical stimulation was perpendicular (top to bottom) to the scratch in the center of the image. Control group In TIFF0007749590000002.tif11170, the acellular area in the center of the image, i.e., the scratch, remained the same size throughout the entire 48 hours. In conditions C and D, the acellular area in the center of the image showed a slight decrease in size, meaning that wound healing in these conditions was slow and inefficient. In condition A, there was a visible change in the size of the acellular area over the course of treatment. Cells treated in condition B showed the greatest decrease in the size of the acellular area and therefore represented the best conditions for wound healing. The healing characteristics of conditions A and B are more clearly shown in Figure 7.

[0073] Figure 7 shows the effect of stimulated (A and B) and unstimulated (B) conditions on monolayer HaCaT cells over a 48-hour period. TIFF0007749590000003.tif11170 shows representative light microscope images of the scratch assay described in Example 2 exposed to electrical stimulation. The scratch area, or acellular area, represents the wound and is shown as the darker area in the center of the image. During electrical stimulation, the acellular area of ​​treated cells (A and B) decreases, while that of unstimulated cells (B and C) decreases. This area in TIFF0007749590000004.tif11170 remains unchanged in size. Furthermore, cells treated under condition B (100 kHz pulse frequency, 2% duty cycle, and 200 mV / mm electric field) exhibit the fastest and most efficient wound healing, as indicated by the significant reduction in the acellular area already visible after 24 hours. After 48 hours of treatment under condition B, the acellular area was almost completely reduced. Condition A exhibits slower and less pronounced wound healing.

[0074] Figure 8 shows the results of HaCaT cells treated under condition A (solid line with squares) and condition B (solid line with triangles) compared with untreated HaCaT cells. Figure 8 shows a graph of cell migration ability (solid line with circles) in TIFF0007749590000005.tif11170. The graph shows the change in cell-free area over time, which was calculated using Image J software, an open-source image processing program. Image J software is used to assess wound closure by tracking the wound perimeter and calculating the closure rate. The scratch width at 0 hours is 100%. As can be seen in Figure 8, the change in cell-free area over time, i.e., the wound healing rate, was highest for HaCaT cells treated under condition B, as evidenced by a change of approximately 50% in cell-free area at 48 hours.

[0075] <Example> Example 1: Demonstration of low impedance and painlessness at high AC frequencies in a simulated wound

[0076] Two electrodes were placed on the dry skin of a person's arm, with a 50 mm interelectrode distance. The electrodes were connected in series to a signal generator with a 50 ohm output impedance. A 100 ohm resistor was inserted in series with the circuit as a measuring resistor to measure current. A simulated wound was created on the arm by applying a thick layer of Cefar Electrogel to the skin between the electrodes. The Cefar Electrogel was applied to form a roughly circular gel layer, approximately 5 mm from each edge of the electrodes. Electrical measurements were made by connecting an oscillometer in series, with the first and second leads of the oscillometer connected immediately before and after the 100 ohm resistor, respectively. Briefly, measurements showed that the AC resistance of the simulated wound was strongly frequency-dependent, ranging from approximately 20 kOhms at 1 Hz to less than 150 Ohms at 100 kHz-1 MHz, and that the DC resistance of the simulated wound was voltage-dependent, ranging from 40 kOhms at 20 V to 263 kOhms at 1 V. While there was no skin irritation after several hours of AC measurements, DC (non-pulsed) measurements resulted in redness and irritation of the skin under the positive electrode, even after only 10 minutes and at measured currents below 0.5 mA. Furthermore, DC voltages / currents above 15 V / 150 μA already caused discomfort. Direct pain was felt at AC frequencies between 0.8 and 3 kHz. Table 1 below shows the impedance values ​​of the simulated wound at different AC frequencies. The table also indicates the AC frequencies at which direct pain was felt.

[0077] [Table 1]

[0078] Conclusion: AC signals with frequencies of at least 10 kHz can be used to deliver current and voltage levels suitable for electrotherapy through the skin without causing pain to simulated wounds. Pulsed DC signals similar to AC signals are expected to behave in a generally similar manner and may therefore be used for electrotherapy.

[0079] Example 2: In vitro study of electrically stimulated HaCaT cells versus controls

[0080] <Setting up the electrical stimulation system> The basic principles of the electrical stimulation system were based on a protocol published in 2007 by Song et al. (doi:10.1038 / nprot.2007.205). The core of the stimulation system consisted of a specially constructed cell culture dish, including a cell culture chamber, a salt bridge to transport electrons, an electrical stimulator to generate current, and a scaffold to hold everything in place. The purpose of this setup was to generate a targeted electric field in the cell culture environment. The protocol by Song et al. was adapted to accommodate the special requirements of this study, including long-term electrical stimulation and microscopy.

[0081] <Cell culture and scratch assay methods> HaCaT cells were cultured in a monolayer in a thin chamber to avoid cell damage due to excessive heating of the medium by the electric field. Cells were seeded in custom-made Petri dishes. Typically, HaCaT cells were cultured at a density of 1x10 4 / cm 2 In order to make the cells confluent as quickly as possible in a limited space, the density of the cell suspension used for seeding was 95x10 4 / cm 2 Trypan blue staining confirmed that the cell viability under the experimental conditions provided was over 95%.

[0082] Typically, a cell-free area is created by scratching a wound in the center of a Petri dish with a pipette tip. However, in this experimental setup, using a tip results in irregular scratch edges, which can easily lift cells in the layer surrounding the edge and cause cells at the scratch edge to break. To avoid these issues, self-adhesive silicone tape was used instead of the tip. The silicone tape was cut to the same width (0.5 mm to 0.7 mm) and pre-attached to the cell culture area. After the cells had grown sufficiently and cell adhesion was achieved, the tape was removed, creating a sufficient cell-free area.

[0083] <Effect of electrical stimulation on cell migration> To investigate the effects of different modes of electrical stimulation on HaCaT cell migration, electrical signals with different parameters (Table 2) were applied to a monolayer of HaCaT cell culture. Stimulated (conditions A, B, C, D) and unstimulated (control) conditions were performed using Ag / AgCl electrodes connected via an agar-salt bridge to prevent electrode products from entering the culture. TIFF0007749590000007.tif11170) was applied to a monolayer of HaCaT cell culture.

[0084] Table 2 shows the parameters tested for the HaCaT cell culture system. [Table 2]

[0085] The scratch or cell-free area in the culture system was photographed 0, 12, 24, 36, and 48 hours after the start of electrical stimulation. Three images of the cell-free area were taken at each time point (Figure 6), and the cell-free area was calculated using Image J software. The initial microscope magnification was 40x.

[0086] The following formula 1 was used to calculate the migration rate of each group at different time points to evaluate their migration ability.

[0087]

number

[0088] The migration rate of the experimental group (A, B) was 1.0%. TIFF0007749590000010.tif11170) showed a tendency to increase (Figures 7 and 8). HaCaT cell cultures exposed to electrical stimulation produced by condition B (100 kHz, 2% duty cycle, 200 mV / mm) showed the most significant increase in migration ability, i.e., the fastest and most efficient wound healing. As seen in Figure 7, the wound was substantially closed after only 24 hours of electrical stimulation therapy, and was almost completely closed after 48 hours of electrical stimulation therapy. As seen in Figure 8, both condition B and condition A showed a significant increase in migration ability compared to the control group ( Condition B significantly improved wound closure rates compared to condition A (normal DC stimulation). Furthermore, condition B closed wounds approximately 50% faster (*p<0.05, **p<0.01, ***p<0.001), significantly better than condition A (normal DC stimulation).

[0089] <Statistics> Results are presented as the mean ± standard error of the mean (SEM). Each experimental condition was measured in triplicate or more (technical replicates, n ≥ 3) and performed three independent times (N = 3). Statistical analysis was performed using GraphPad Prism software (version 8.0.2, El Camino Real, USA). Data sets were compared using the Kruskal-Wallis H test. α = 0.05 was set as the maximum type I error rate. * < 0.05, ** < 0.01, *** < 0.001 were used to classify P values ​​compared to the control group.

[0090] <Conclusion> The cell system described in this example meets the requirements for testing cell migration ability.

[0091] Electrical stimulation delivered under conditions A and B tended to improve cell migration ability, with the most significant change occurring under condition B, i.e., a pulse frequency of 100 kHz, a duty cycle of 2%, and an electric field of 200 mV / mm.

[0092] Based on the in vitro studies presented above, it is clear that electrical stimulation delivered in accordance with the concepts of the present invention provides superior wound healing properties. Furthermore, in accordance with the data provided in Example 1, the electrical stimulation conditions tested herein are believed to have minimal adverse effects on the patient during the course of electrical therapy. Therefore, an optimal stimulation algorithm consisting of high-frequency pulses of at least 50 kHz or 100 kHz and a low duty cycle (less than 10%) is believed to deliver maximum electric field (EF) force to the wound with minimal battery power consumption and minimal power loss at the skin. This maximizes battery life, generates the desired EF of 50-200 mV / mm at the wound, and completely avoids discomfort such as itching, skin reaction, or muscle activation associated with direct current or low-frequency current through the skin.

Claims

1. An apparatus for electrotherapy configured to apply a pulsed direct current through a wound, comprising: a controlled voltage source connected to the at least two stimulation electrodes; The stimulation electrode is configured to be in electrical contact with the skin surrounding the wound at a distance of up to 50 mm from the wound edge, the controlled voltage source is configured to output a pulsed direct current having a frequency of at least 50 kHz, the pulsed direct current having a duty cycle in the range of 1% to 10%, and the pulsed direct current output from the controlled voltage source has an average current level in the range of 1 mA to 10 mA.

2. 10. The apparatus of claim 1, wherein the average peak voltage output from the controlled voltage source is limited to within the range of 0.1V to 20V.

3. An apparatus as described in any one of claims 1 or 2, wherein the pulsed direct current has a duty cycle within the range of 2% to 10%.

4. 3. The apparatus of claim 1, wherein the pulsed direct current has a duty cycle in the range of 1% to 4%.

5. An apparatus described in any one of claims 1 to 4, wherein the pulsed direct current is a single-phase pulsed direct current.

6. 6. The apparatus of claim 1, wherein the controlled voltage source is configured to output a pulsed direct current having a frequency in the range of 50 kHz to 500 kHz.

7. 7. The apparatus of claim 1, wherein the controlled voltage source is configured to output a pulsed direct current having a frequency in the range of 60 kHz to 500 kHz.

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