Patent Description:
The present disclosure provides apparatus and methods for measuring type and degree of tissue damage around a burn or other type of wound.

Serious wounds and burns may have regions of various degrees of damage surrounding the wound site. Effective treatment may require removal of non-viable tissue, yet it can be difficult to visually assess tissue viability. For an open wound such as a burn, there may be a region of non-viable tissue around the immediate wound while further away the tissue may be less damaged and characterized by swelling known as "edema" yet viable and likely to recover.

A common method of burn evaluation assesses the visual and tactile characteristics, namely wound appearance, capillary blanching and refill, capillary staining, and burn wound sensibility to light touch and pinprick. Estimation of the burn depth is difficult. In addition, burn wounds are dynamic and can progress over time and the changes do not immediately become visually apparent.

The invention is defined by an apparatus for determining a depth of a burn according to claim <NUM>. Further embodiments are defined by dependent claims <NUM>-<NUM>.

Some aspects of the disclosure are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and are for purposes of illustrative discussion of aspects of the disclosure. In this regard, the description and the drawings, considered alone and together, make apparent to those skilled in the art how aspects of the disclosure may be practiced.

The present disclosure describes measurement of various electrical characteristics and derivation of SEM values indicative of the accumulation or depletion of extracellular fluid (ECF), also referred to as intercellular fluid, and the application of this information to the assessment of tissue viability. Examples are provided of application to thermal burns yet are applicable to other types of wounds. These examples are not limiting and the demonstrated principles may be applied to a larger scope of injuries and conditions than the specific example. For example, apparatus and methods disclosed in relation to a <NUM>rd-degree burn may be used with equal efficacy to an open cut, gangrene, an ulcer, or other similar injury.

Assessment of tissue viability around wounds and burns may be improved by determination of the amount of SEM in the tissue surrounding the actual damage. Typically, the tissue immediately around a wound will exhibit a reduced level of SEM, indicating a lower level of tissue viability. Further out from the wound, the tissue will exhibit an increased level of moisture, or edema. This value may be very high around the edge of the low-moisture tissue, indicating a high degree of damage with a high risk of eventual tissue death. The SEM value may taper off with increasing distance from the wound, where a moderately raised SEM level indicates damage with a higher chance of tissue viability. Mapping the areas of low-viability tissue, as indicated by reduced levels of tissue moisture, and the surrounding area of edema can provide important guidance to a clinician during the treatment of the wound.

This description is not intended to be a detailed catalog of all the different ways in which the disclosure may be implemented, or all the features that may be added to the instant disclosure. For example, features illustrated with respect to one embodiment may be incorporated into other embodiments, and features illustrated with respect to a particular embodiment may be deleted from that embodiment. Thus, the disclosure contemplates that in some embodiments of the disclosure, any feature or combination of features set forth herein can be excluded or omitted. In addition, numerous variations and additions to the various embodiments suggested herein will be apparent to those skilled in the art in light of the instant disclosure, which do not depart from the instant disclosure. In other instances, well-known structures, interfaces, and processes have not been shown in detail in order not to unnecessarily obscure the invention. It is intended that no part of this specification be construed to effect a disavowal of any part of the full scope of the invention. Hence, the following descriptions are intended to illustrate some particular embodiments of the disclosure, and not to exhaustively specify all permutations, combinations and variations thereof.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used in the description of the disclosure herein is for the purpose of describing particular embodiments or aspects only and is not intended to be limiting of the disclosure.

All publications, patent applications, patents and other references cited herein are incorporated by reference in their entireties for the teachings relevant to the sentence and/or paragraph in which the reference is presented. References to techniques employed herein are intended to refer to the techniques as commonly understood in the art, including variations on those techniques or substitutions of equivalent techniques that would be apparent to one of skill in the art.

Unless the context indicates otherwise, it is specifically intended that the various features of the disclosure described herein can be used in any combination. Moreover, the present disclosure also contemplates that in some embodiments of the disclosure, any feature or combination of features set forth herein can be excluded or omitted.

The methods (no method by itself is falling within the scope of the claims) disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another without departing from the scope of the present disclosure. In other words, unless a specific order of steps or actions is required for proper operation of the embodiment, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the present disclosure.

As used in the description of the disclosure and the appended claims, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

As used herein, "and/or" refers to and encompasses any and all possible combinations of one or more of the associated listed items, as well as the lack of combinations when interpreted in the alternative ("or").

The terms "about" and "approximately" as used herein when referring to a measurable value such as a length, a frequency, or a SEM value and the like, is meant to encompass variations of ± <NUM>%, ± <NUM>%, ± <NUM>%, ± <NUM>%, ± <NUM>%, or even ± <NUM>% of the specified amount.

As used herein, phrases such as "between X and Y" and "between about X and Y" should be interpreted to include X and Y. As used herein, phrases such as "between about X and Y" mean "between about X and about Y" and phrases such as "from about X to Y" mean "from about X to about Y.

The terms "comprise," "comprises," and "comprising" as used herein, specify the presence of the stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

As used herein, the transitional phrase "consisting essentially of" means that the scope of a claim is to be interpreted to encompass the specified materials or steps recited in the claim and those that do not materially affect the basic and novel characteristic(s) of the claimed disclosure. Thus, the term "consisting essentially of" when used in a claim of this disclosure is not intended to be interpreted to be equivalent to "comprising.

As used herein, the term "sub-epidermal moisture" or "SEM" refers to the increase in tissue fluid and local edema caused by vascular leakiness and other changes that modify the underlying structure of the damaged tissue in the presence of continued pressure on tissue, apoptosis, necrosis, and the inflammatory process.

As used herein, a "system" may be a collection of devices in wired or wireless communication with each other.

As used herein, "interrogate" refers to the use of radiofrequency energy to penetrate into a patient's skin.

As used herein, a "patient" may be a human or animal subject.

As used herein, a "<NUM>rd-degree burn" refers to a full thickness burn that goes through the dermis and affect deeper tissues.

<FIG> discloses a toroidal bioimpedance sensor <NUM>. In this exemplary configuration, a center electrode <NUM> is surrounded by a ring electrode <NUM>. Without being limited to a particular theory, a gap between two electrodes of sensor <NUM> can affect the depth of field penetration into a substrate below sensor <NUM>. In an aspect, a ground plane (not visible in <FIG>), is parallel to and separate from the plane of the electrodes. In one aspect, a ground plan extends beyond the outer diameter of ring electrode <NUM>. Without being limited to a particular theory, a ground plane can limit the field between electrodes <NUM> and <NUM> to a single side of the plane of electrodes <NUM> and <NUM> that is on the opposite side of the plane of electrodes <NUM> and <NUM> from the ground plane.

<FIG> discloses an idealized field map created by a toroidal sensor of <FIG> when activated by a drive circuit (not shown in <FIG>). In one aspect, when an electric voltage is applied across two electrodes <NUM>, <NUM>, an electric field <NUM> is generated between electrodes <NUM> and <NUM> that extends outward from the plane of electrodes <NUM> and <NUM> to a depth of field <NUM>. In an aspect, the diameter of a center electrode <NUM>, the inner and outer diameters of a ring electrode <NUM>, and the gap between two electrodes <NUM> and <NUM> may be varied to change characteristics of field <NUM>, for example the depth of field <NUM>.

In use, a drive circuit according to the invention measures capacitance, while drive circuits according to embodiments not within the scope of the claims can measure an electrical property or parameter that comprises one or more of a resistance, an inductance, an impedance, a reluctance, or other electrical characteristic as sensed by electric field <NUM>. Depending on the type of drive circuit being employed in an apparatus, a sensor of an apparatus may be a bipolar radiofrequency sensor, a bioimpedance sensor, a capacitive sensor, or an SEM sensor. In an aspect, the measured electrical parameter is related to the moisture content of the epidermis of a patient at a depth that is determined by the geometry of electrodes <NUM> and <NUM>, the frequency and strength of electrical field <NUM>, and other operating characteristics of an apparatus drive circuit. In one aspect, the measured moisture content is equivalent to the SEM content with a value on a predetermined scale. In an aspect, a predetermined scale may range from <NUM> to <NUM>, such as from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>. In one aspect, a predetermined scaled can be scaled by a factor or a multiple based on the values provided herein.

<FIG> provides top and bottom views of a SEM scanner <NUM> that comprises electronics that drive sensor <NUM>, which is similar to sensor <NUM> of <FIG>, and measure a capacitance between electrodes <NUM> and <NUM>. This capacitance is converted to a SEM value that is displayed on display <NUM>.

These aspects of sensor <NUM> and SEM scanner <NUM> are disclosed in <CIT>, from which the <CIT> was filed as a national phase entry.

<FIG> depicts an exemplary electrode array <NUM>, according to the present disclosure. In an aspect, an array <NUM> is composed of individual electrodes <NUM> disposed, in this example, in a regular pattern over a substrate <NUM>. In an aspect, each electrode <NUM> is separately coupled (through conductive elements not shown in <FIG>) to a circuit, such as described with respect to <FIG>, that is configured to measure an electrical parameter. In one aspect, a "virtual sensor" is created by selective connection of predetermined subsets of electrodes <NUM> to a common element of a circuit. In one aspect, a particular electrode <NUM> is connected as a center electrode, similar to electrode <NUM> of <FIG>, and six electrodes 320A-320F are connected together as a "virtual ring" electrode, similar to electrode <NUM> of <FIG>. In an aspect, two individual electrodes are individually connected to a circuit to form a virtual sensor, for example electrodes <NUM> and 320A are respectively connected as two electrodes of a sensor. In one aspect, one or more electrodes <NUM> are connected together to form one or the other electrodes of a two-electrode sensor.

Any pair of electrodes, whether composed of single electrodes or a set of electrodes coupled together to form virtual electrodes, is coupled to electronics that are configured to measures an electrical property or parameter that comprises one or more of a resistance, a capacitance, an inductance, an impedance, a reluctance, or other electrical characteristic with one or more of sensors <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or other two-electrode sensor.

<FIG> depicts another exemplary array <NUM> of electrodes <NUM>, according to the present disclosure. In an aspect, each of electrodes <NUM> is an approximate hexagon that is separated from each of the surrounding electrodes <NUM> by a gap <NUM>. In one aspect, electrodes <NUM> are one of circles, squares, pentagons, or other regular or irregular shapes. In an aspect, gap <NUM> is uniform between all electrodes <NUM>. In one aspect, gap <NUM> varies between various electrodes. In an aspect, electrodes <NUM> may be interconnected to form virtual sensors as described below with respect to <FIG>.

<FIG> depicts an array <NUM> of electrodes <NUM> that are configured, e.g. connected to a measurement circuit, to form a sensor <NUM>, according to the present disclosure. In an aspect, a single hexagonal electrode <NUM> that is labeled with a "<NUM>" forms a center electrode and a ring of electrodes <NUM> that are marked with a "<NUM>" are interconnected to form a ring electrode. In an aspect, electrodes <NUM> between the center and ring electrode are electrically "floating. " In one aspect, electrodes <NUM> between the center and ring electrode are grounded or connected to a floating ground. In one aspect, electrodes <NUM> that are outside the ring electrode are electrically "floating. " In an aspect, electrodes <NUM> that are outside the virtual ring electrode are grounded or connected to a floating ground.

<FIG> depicts an alternate aspect where an array <NUM> of electrodes <NUM> has been configured to form a virtual sensor <NUM>, according to the present disclosure. In an aspect, multiple electrodes <NUM>, indicated by a "<NUM>," are interconnected to form a center electrode while a double-wide ring of electrodes, indicated by a "<NUM>," are interconnected to form a ring electrode. In one aspect, various numbers and positions of electrodes <NUM> are interconnected to form virtual electrodes of a variety of sizes and shapes.

<FIG> depicts an example wound, in this case a <NUM>rd-degree burn <NUM> with an open wound <NUM>. Response of tissue around a <NUM>rd-degree burn injury may comprise three zones. In an aspect, innermost zone <NUM> at the center of a wound will have necrosis with no perfusion of oxygen and irreversible damage due to the coagulation of proteins. In one aspect, second zone <NUM>, also known as the "zone of stasis," is a ring around a first zone <NUM>, where there is a decrease in perfusion and a reduction in SEM. Without being limited to a particular theory, capillaries may be nonfunctional in second zone <NUM>, leading to increased permeability of capillaries and arterioles and subsequent ischemia reperfusion injury. There may be a chance of tissue recovery in second zone <NUM> if cascading release of free radicals and cellular damage leading to apoptosis can be prevented. In an aspect, surrounding a second zone <NUM> is a zone <NUM> of hyperaemia where the tissue is damaged but retains good perfusion and will generally heal. Without being limited to a particular theory, the size, shape, and depth of wound <NUM> as well as zones <NUM>, <NUM>, <NUM> depends on the details of the event that caused the injury. In accordance with the present disclosure, evaluation of burn depth and extent is one component on which treatment decisions are based, as inaccuracies can lead to unnecessary surgeries or patients staying for extensive lengths of time.

<FIG> is a cross-section of a burn <NUM> shown in <FIG>, taken along line A-A in <FIG>. In an aspect, a first region <NUM> may extend below an open wound <NUM> as well as to the sides. In one aspect, a region <NUM> may extend below one or both of an open wound <NUM> and region <NUM>. In an aspect, at some distance from open wound <NUM>, there will be undamaged, or "normal," tissue <NUM>.

In accordance with the present disclosure, burns may be characterized as "partial thickness" or "full thickness" burns, depending upon whether damaged zones <NUM> and <NUM> extend through a skin into subcutaneous tissue. Superficial partial-thickness injuries, such as a blister of a 2nd-degree burn, are viable and will generally heal with antimicrobial dressings. Deep partial-thickness wounds are more like full-thickness burns and may require surgical excision and grafting for improved functional and cosmetic outcomes. Partial-thickness wounds are complicated to treat, as it is difficult to determine if viable structures are present and capable of healing the wound. Whatever inaccuracies associated with diagnosis may affect treatment, as it is possible that a superficial burn will receive surgery for a healing wound.

Burn wounds are challenging problems as they are dynamic and have the capacity to change and progress over time. In zone <NUM>, heating of the tissue has caused complete necrosis of the dermis and all dermal structures along with fat necrosis. Without being limited to a particular theory, moisture content of zone <NUM> is lower than normal and remains low after the injury due to destruction of the local blood vessels, which prevents perfusion into the necrotic region.

Without being limited to a particular theory, in zone <NUM>, return of blood flow after the initial thermal exposure restores perfusion and oxygenation. While not being limited to theory, the restoration of oxygenation can be important for cellular survival but also initiates a cascade of events that results in production of free radicals that lead to further tissue injury. The accumulation of burn edema can occur in a two-phase pattern. In the first phase, there is a rapid increase in interstitial fluid within the first hour post-injury and approximately <NUM>% of total edema is present at <NUM> hours post-injury. The second phase is marked by a gradual increase in fluid accumulation over the next <NUM>-<NUM> hours. In non-burn injuries, fluid movement from the capillary to the interstitium may be generally balanced by lymphatic clearance so that excess fluid does not accumulate. However, in burn injuries, while not being limited to theory, the movement of fluid and protein into the extravascular space can occur very rapidly and edema ensues because the lymphatics are unable to keep pace with the clearance of fluid and protein. Accordingly, again without being limited to a particular theory, in an aspect, the amount of edema in zone <NUM> is less than in zone <NUM>, although the amount of SEM is still increased above normal. Mapping the pattern of edema allows an assessment of which tissue is at risk.

<FIG> depicts an example plot <NUM> of how SEM values may vary across burn <NUM>, according to the present disclosure. SEM values taken along cross-section A-A have been plotted as curve <NUM>, with the x-axis being the location along cross-section A-A and the y-axis being the SEM value. A reference line <NUM> indicates normal tissue SEM value, which may a standard reference value or a measurement of known undamaged tissue on the patient.

In an aspect, curve <NUM> generally shows a region <NUM> where a SEM value is greater than reference line <NUM>. In one aspect, curve <NUM> in region <NUM> may be only slightly raised, as indicated by the bottom of the shaded region, or may be significantly increased as indicated by the top of the shaded region <NUM>. In an aspect, a peak value <NUM> of region <NUM> is an indication of the degree or depth of the damage in zone <NUM>.

In one aspect, point <NUM> on curve <NUM> indicates a transition from zone <NUM> to zone <NUM>. In an aspect, a SEM value is higher than reference line <NUM> but not so elevated as to indicate a risk that a tissue will not recover. In one aspect, location of a transition from zone <NUM> to zone <NUM> may be identified on curve <NUM> as the x-axis position of a point <NUM> using a known magnitude of a SEM value. In an aspect, the magnitude of a SEM value at point <NUM> may be a value selected from the group consisting of a predetermined value, a predetermined increase above a reference SEM value, a percentage of a reference SEM value, a percentage of peak value <NUM>, and other value determined from curve <NUM>.

In an aspect, a predetermined SEM value may range from <NUM> to <NUM>, such as from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In an aspect, a predetermined SEM value may range from <NUM> to <NUM>, such as from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In one aspect, a predetermined SEM value may range from <NUM> to <NUM>, such as from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In one aspect, a predetermined SEM value may be about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. In an aspect, a predetermined SEM value can be scaled by a factor or a multiple based on the values provided herein.

In an aspect, a predetermined increase may range from <NUM> to <NUM>, such as from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In an aspect, a predetermined increase may range from <NUM> to <NUM>, such as from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In one aspect, a predetermined increase may range from <NUM> to <NUM>, such as from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In one aspect, a predetermined increase may be about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. In an aspect, a predetermined increase can be scaled by a factor or a multiple based on the values provided herein.

In one aspect, a reference SEM value is represented by a reference line <NUM>. In an aspect, a reference SEM value may range from <NUM> to <NUM>, such as from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In an aspect, a reference SEM value may range from <NUM> to <NUM>, such as from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In one aspect, a reference SEM value may range from <NUM> to <NUM>, such as from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In one aspect, a reference SEM value may be about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. In an aspect, a reference SEM value can be scaled by a factor or a multiple based on the values provided herein.

In an aspect, a peak value may range from <NUM> to <NUM>, such as from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In an aspect, a peak value may range from <NUM> to <NUM>, such as from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In one aspect, a peak value may range from <NUM> to <NUM>, such as from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, or from <NUM> to <NUM>. In one aspect, a peak value may be about <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM>. In an aspect, a peak value can be scaled by a factor or a multiple based on the values provided herein.

One or more regions may be defined on a body. In an aspect, measurements made within a region are considered comparable to each other. A region may be defined as an area on the skin of the body where measurements may be taken at any point within the area. In an aspect, a region corresponds to an anatomical region (e.g., heel, ankle, lower back). In an aspect, a region may be defined as a set of two or more specific points relative to anatomical features where measurements are taken only at the specific points. In an aspect, a region may comprise a plurality of non-contiguous areas on the body. In an aspect, the set of specific locations may include points in multiple non-contiguous areas.

In an aspect, a region is defined by surface area. In an aspect, a region may be, for example, between <NUM> and <NUM><NUM>, between <NUM> and <NUM><NUM>, between <NUM> and <NUM><NUM>, or between <NUM> and <NUM><NUM>, between <NUM> and <NUM><NUM>, or between <NUM> and <NUM><NUM>.

In an aspect, measurements may be made in a specific pattern or portion thereof. In an aspect, the pattern of readings is made in a pattern with the target area of concern in the center. In an aspect, measurements are made in one or more circular patterns of increasing or decreasing size, T-shaped patterns, a set of specific locations, or randomly across a tissue or region. In an aspect, a pattern may be located on the body by defining a first measurement location of the pattern with respect to an anatomical feature with the remaining measurement locations of the pattern defined as offsets from the first measurement position.

In an aspect, a plurality of measurements are taken across a tissue or region and the difference between the lowest measurement value and the highest measurement value of the plurality of measurements is recorded as a delta value of that plurality of measurements. In an aspect, <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, <NUM> or more, or <NUM> or more measurements are taken across a tissue or region.

In an aspect, a threshold may be established for at least one region. In an aspect, a threshold of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or other value may be established for the at least one region. In an aspect, a delta value is identified as significant when the delta value of a plurality of measurements taken within a region meets or exceeds a threshold associated with that region. In an aspect, each of a plurality of regions has a different threshold. In an aspect, two or more regions may have a common threshold.

In an aspect, a threshold has both a delta value component and a chronological component, where a delta value is identified as significant when the delta value is greater than a predetermined numerical value for a predetermined portion of a time interval. In an aspect, the predetermined portion of a time interval is defined as a minimum of X days where a plurality of measurements taken that day produces a delta value greater than or equal to the predetermined numerical value within a total of Y contiguous days of measurement. In an aspect, the predetermined portion of a time interval may be defined as <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> consecutive days on which a plurality of measurements taken that day produces a delta value that is greater than or equal to the predetermined numerical value. In an aspect, the predetermined portion of a time interval may be defined as some portion of a different specific time period (weeks, month, hours etc.).

In an aspect, a threshold has a trending aspect where changes in the delta values of consecutive pluralities of measurements are compared to each other. In an aspect, a trending threshold is defined as a predetermined change in delta value over a predetermined length of time, where a determination that the threshold has been met or exceeded is significant. In an aspect, a determination of significance will cause an alert to be issued. In an aspect, a trend line may be computed from a portion of the individual measurements of the consecutive pluralities of measurements. In an aspect, a trend line may be computed from a portion of the delta values of the consecutive pluralities of measurements.

In an aspect, the number of measurements taken within a single region may be less than the number of measurement locations defined in a pattern. In an aspect, a delta value will be calculated after a predetermined initial number of readings, which is less than the number of measurement locations defined in a pattern, have been taken in a region and after each additional reading in the same region, where additional readings are not taken once the delta value meets or exceeds the threshold associated with that region.

In an aspect, the number of measurements taken within a single region may exceed the number of measurement locations defined in a pattern. In an aspect, a delta value will be calculated after each additional reading.

In an aspect, a quality metric may be generated for each plurality of measurements. In an aspect, this quality metric is chosen to assess the repeatability of the measurements. In an aspect, this quality metric is chosen to assess the skill of the clinician that took the measurements. In an aspect, the quality metric may include one or more statistical parameters, for example an average, a mean, or a standard deviation. In an aspect, the quality metric may include one or more of a comparison of individual measurements to a predefined range. In an aspect, the quality metric may include comparison of the individual measurements to a pattern of values, for example comparison of the measurement values at predefined locations to ranges associated with each predefined location. In an aspect, the quality metric may include determination of which measurements are made over healthy tissue and one or more evaluations of consistency within this subset of "healthy" measurements, for example a range, a standard deviation, or other parameter.

In one aspect, a measurement, for example, a threshold value, is determined by SEM Scanner Model <NUM> (Bruin Biometrics, LLC, Los Angeles, CA). In another aspect, a measurement is determined by another SEM scanner.

In an aspect, a measurement value is based on a capacitance measurement by reference to a reference device. In an aspect, a capacitance measurement can depend on the location and other aspects of any electrode in a device. Such variations can be compared to a reference SEM device such as an SEM Scanner Model <NUM> (Bruin Biometrics, LLC, Los Angeles, CA). A person of ordinary skill in the art understands that the measurements set forth herein can be adjusted to accommodate a difference capacitance range by reference to a reference device.

In an aspect, a percentage in accordance with the present disclosure may range from <NUM>-<NUM>%, such as <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>%-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>%-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, <NUM>-<NUM>%, or <NUM>-<NUM>%. In one aspect, a percentage in accordance with the present disclosure may be about <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, or <NUM>%.

In an aspect, point <NUM> on curve <NUM> indicates a transition from zone <NUM>, where edema has occurred, to zone <NUM>, where the tissue has a moisture content below normal. In one aspect, a measured SEM value that equals the normal value of reference line <NUM> indicates that a portion of a sensor is over tissue having a higher-than-normal moisture content while the remaining portion of the sensor is over tissue having a lower-than-normal moisture content. In an aspect, point <NUM> on line A-A is approximately the location of the edge of zone <NUM>. If it is desirable to excise the necrotic tissue from a patient, marking the skin at this point provides a reference to the surgeon of the edge of necrotic tissue.

In one aspect, successive measurements of SEM values at one or more points proximate to an open wound <NUM>, for example at <NUM> minute intervals for the first <NUM> hours, can provide information regarding the degree of damage to the tissue. In an aspect, successive measurements can be performed at approximately <NUM> minute intervals, <NUM> minute intervals, <NUM> minute intervals, <NUM> minute intervals, <NUM> minute intervals, <NUM> minute intervals, <NUM> minute intervals, <NUM> minute intervals, <NUM> minute intervals, <NUM> minute intervals, <NUM> minute intervals, or <NUM> minute intervals. In one aspect, successive measurement can be performed at time intervals for the first <NUM> hour, <NUM> hours, <NUM> hours, <NUM> hours, <NUM> hours, <NUM> hours, <NUM> hours, <NUM> hours, <NUM> hours, <NUM> hours, or <NUM> hours after an injury. In an aspect, the value and position of point <NUM> over the first <NUM> hours post-injury may indicate the depth of the burn and the risk of tissue depth in certain areas. Outward progression of the peak SEM values on the x-axis may indicate the severity of the reperfusion damage.

In one aspect, measurements of SEM values may be taken with a single-sensor device, such as a SEM scanner <NUM> of <FIG>, and logged, plotted, and assessed.

Other types of wounds, for example a cut, may suffer from zones of tissue death proximate to open wound <NUM>. As the level of edema is still an indication of tissue viability, the same sensing and categorization method will provide valuable information to a clinician treating the injury. Thus, the methods and apparatus described for the example burn may also be applicable to other types of injury.

The methods and apparatus disclosed herein may also be used to track the healing process of injuries such as burns, cuts, ulcers, and other types of tissue damage. Closure of the skin over a wound is not the end of the healing process, and it may take a year after the skin closes for the sub-epidermal tissue to return to its original state. Periodic assessment of the site of the original wound will show whether the healing is continuing to progress or has halted or reversed. As an example, pressure ulcers are known to suffer a high incidence of recurrence at the same location as a first ulcer. This is thought to be a result of continued pressure at the site combined with a weakened tissue structure as a result of incomplete healing. In the absence of continued measurement of the tissue state, for example with a SEM scanner, it is likely that a caregiver would consider a closed wound as a healed wound and not continue the therapy that would prevent the recurrence. Measurements of surrounding tissue at sites away from the original wound can serve as a reference of what "normal" tissue measurements. The trend of changes, or lack thereof, of measurements at the former wound site against this reference provides a continued assurance that the tissue is moving toward a fully healed condition.

This monitoring of tissue improvement after the wound has healed is also useful to monitor the performance and efficacy of wound-healing therapies. As an example, an electro-stimulus device may be used once a wound has closed in order to accelerate the healing process of the underlying tissue. The progress of the healing is likely to be difficult if not impossible to assess manually or visually. A SEM scanning device could be used to establish one or more of a SEM measurement at the site of the closed wound, periodic measurements and trend analysis to verify the effectiveness of the healing device, and measurement of adjacent tissue as a reference of fully healed tissue. In certain embodiments, adjustments may be made to the healing device, for example a change in the frequency or voltage of an electro-stimulus device, based on the measurements or the trend of the measurements made by an SEM scanner. In certain embodiments, the use of a healing device or therapy may be halted or replaced with a different device or therapy based on the SEM measurements or trend. In certain embodiments, the wound may be judged to be "healed" based on the SEM measurement and healing therapies may be halted, modified, or replaced with preventative therapies. In certain embodiments, the difference between a current SEM reading at the site of the wound and a reference value from nearby healthy tissue is a metric of the degree of recovery of the tissue at the wound site, where a zero difference is fully healed and restored to original condition.

<FIG> depicts an aspect of a SEM sensing apparatus <NUM>, according to the present disclosure. In one aspect, a flexible substrate <NUM> has a plurality of SEM sensors <NUM> arranged on a common surface of substrate <NUM>. In an aspect, sensors <NUM> comprise toroidal sensors <NUM> as shown in <FIG>. In one aspect, sensors <NUM> comprise an electrode array <NUM> as shown in <FIG>. In an aspect, sensors <NUM> comprise an electrode array <NUM> as shown in <FIG>. In one aspect, sensors <NUM> are coupled to electronics (not shown in <FIG>) that provide excitation and measure an SEM value of the tissue below the respective sensors <NUM>.

In an aspect, SEM sensing apparatus <NUM> comprises visual indicators <NUM> that are arranged on a substrate <NUM>. In one aspect, visual indicators <NUM> are on a first surface of a substrate <NUM> while sensors <NUM> are on a second surface of substrate <NUM> that is opposite the first surface. In an aspect, visual indicators <NUM> are disposed between at least some pairs of sensors <NUM>. In one aspect, visual indicators <NUM> may be light emitting devices (LEDs). In an aspect, visual indicators <NUM> may emit a single color of light. In an aspect, visual indicators <NUM> may selectably emit one of a plurality of colors of light. In one aspect, visual indicators <NUM> are selectable to be on or off. In an aspect, visual indicators <NUM> are coupled to electronics (not shown in <FIG>) that provide excitation and selectable control of visual indicators <NUM>.

In an aspect, electronics of the present disclosure actuate each visual indicator <NUM> with a color of light selected based on the SEM values measured by sensors <NUM> disposed on each side of the respective visual indicator <NUM>. This provides a color-coded map of the various zones <NUM>, <NUM>, and <NUM> for a given wound <NUM>.

In one aspect, visual indicators <NUM> may be disposed on the same surface of substrate <NUM> as sensors <NUM>. In an aspect, visual indicators <NUM> comprise marking element (not visible in <FIG>) that can selectably mark the skin of a patient on which a SEM sensing apparatus <NUM> is placed. In an aspect, electronics of the present disclosure can actuate the marking element of visual indicators <NUM> that are disposed along one or more of the boundaries between zones of <FIG>. In one aspect, electronics of the present disclosure may actuate the marking elements to mark the boundary between zone <NUM> and zone <NUM>, indicating the outer edge of non-viable tissue.

<FIG> disclose an aspect of a SEM sensing assembly <NUM>, according to the present disclosure. In one aspect, an array <NUM> of electrodes <NUM> is disposed on a substrate <NUM>. In an aspect, electrodes <NUM> are similar to electrodes <NUM> of <FIG>. In one aspect, electrodes <NUM> are similar to electrodes <NUM> of <FIG>.

In an aspect, a SEM sensing apparatus <NUM> comprises a plurality of perforations <NUM>. In one aspect, perforations <NUM> are disposed between pairs of electrodes <NUM>, as shown in <FIG>. In use, SEM sensing apparatus <NUM> can be placed on the skin of a patient over a wound and a clinician marks the skin of the patient as guided by the SEM values measured between various pairs of electrodes <NUM>.

In an aspect, a SEM sensing apparatus <NUM> may comprise both visual indicators <NUM> and perforations <NUM>, allowing a clinician to mark the skin of a patient as guided by the colors of various visual indicators <NUM>.

<FIG> discloses an aspect of an apparatus <NUM> for mapping areas of damage around a wound, according to the present disclosure. In one aspect, a patient's arm <NUM> has a burn <NUM> with an open wound <NUM>. In an aspect, apparatus <NUM> comprises an instrument head <NUM> overhanging arm <NUM> with an optical system <NUM> that comprises a camera (not visible in <FIG>) that observes area <NUM> on arm <NUM> and a projector (not visible in <FIG>) that can project one or more images onto area <NUM>, which encompasses wound <NUM> as well as tissue around wound <NUM>. In one aspect, a SEM sensing apparatus <NUM> is coupled to electronics (not shown in <FIG>) that also control optical system <NUM>. In an aspect, SEM sensing apparatus <NUM> is coupled to electronics of the present disclosure through a cable <NUM>. In an aspect, SEM sensing apparatus <NUM> comprises a wireless linkage in place of cable <NUM>. In one aspect, SEM sensing apparatus <NUM> comprises a fiducial <NUM> that is visible to a camera while apparatus <NUM> is in use. In an aspect, SEM sensing apparatus <NUM> comprises a single bioimpedance sensor and, therefore, measures the ECF at a single point at a time.

In use, a user can make multiple measurements with a SEM sensing apparatus <NUM> in area <NUM>. At the time of each measurement, a camera can observe and record the position of fiducial <NUM> in its field of view. In an aspect, reference marks (not shown in <FIG>) may be made on arm <NUM> to record the position of arm <NUM> in the field of view and enable movement of arm <NUM> during an assessment. As the set of measurements increases, electronics of the present disclosure determines the location of a boundary between tissue types, for example a boundary between viable and non-viable tissue, and causes the projector to project indicating images along this boundary. In <FIG>, these images are shown as dots <NUM>. In an aspect, a projected image may comprise lines, areas of color, areas shading from a first color to a second color, areas shading from one intensity of a color to a different intensity of the same color, or other visual indication that provides guidance as to the condition of the tissue in area <NUM>.

Claim 1:
An apparatus (<NUM>) for determining a depth of a burn wound, said apparatus comprising:
a pair of electrodes capable of forming a capacitive sensor (<NUM>) that is configured to measure a capacitance of a region of tissue proximate to the pair of electrodes,
a drive circuit electronically coupled to said capacitive sensor,
a processor electronically coupled to said drive circuit, and
a non-transitory computer-readable medium electronically coupled to said processor and comprising instructions stored thereon that, when executed on said processor, perform the steps of:
receiving said measured capacitance from said capacitive sensor via said drive circuit,
converting said measured capacitance to an associated sub-epidermal moisture (SEM) value,
comparing said SEM value to a data array comprising pairs of SEM values and depths of burns, and
determining the depth of said burn wound associated with said SEM value.