Abstract:
An electrosurgical return electrode for use in monopolar surgery is disclosed. The return electrode includes a conductive pad which includes a plurality of conductive elements, forming a grid. A plurality of temperature sensors are each operatively engaged with a respective one of the plurality of conductive elements. A connection device is capable of selectively transferring radio frequency current from an active electrode to each of the plurality of conductive elements. The connection device may be connected and/or disconnected to a conductive element when a temperature sensor senses a predetermined temperature or range of temperatures. Specifically, if the temperature of a portion of the patient is too high, the corresponding conductive element may be disconnected from the connection device. If the temperature of a portion of the patient is low enough, the corresponding conductive element can be connected (or reconnected) to the connection device.

Description:
BACKGROUND  
       [0001]     1. Technical Field  
         [0002]     The present disclosure is directed to an electrosurgical apparatus and method, and, is particularly directed to a patient return electrode pad containing grids and a method for performing monopolar surgery using the same.  
         [0003]     2. Background  
         [0004]     During electrosurgery, a source or active electrode delivers energy, such as radio frequency energy, from an electrosurgical generator to a patient. A return electrode carries the current back to the electrosurgical generator. In monopolar electrosurgery, the source electrode is typically a hand-held instrument placed by the surgeon at the surgical site and the high current density flow at this electrode creates the desired surgical effect of cutting and/or coagulating tissue. The patient return electrode is placed at a remote site from the source electrode and is typically in the form of a pad adhesively adhered to the patient.  
         [0005]     The return electrode typically has a relatively large patient contact surface area to minimize heating at that site because the smaller the surface area, the greater the current density and the greater the intensity of the heat. That is, the area of the return electrode that is adhered to the patient is generally important because it is the current density of the electrical signal that heats the tissue. A larger surface contact area is desirable to reduce heat intensity. The size of return electrodes is based on assumptions of the maximum current seen in surgery and the duty cycle (e.g., the percentage of time the generator is on) during the procedure. The first types of return electrodes were in the form of large metal plates covered with conductive jelly. Later, adhesive electrodes were developed with a single metal foil covered with conductive jelly or conductive adhesive. However, one problem with these adhesive electrodes was that if a portion peeled from the patient, the contact area of the electrode with the patient decreased, thereby increasing the current density at the adhered portion and, in turn, increasing the heat applied to the tissue. This risked burning the patient in the area under the adhered portion of the return electrode if the tissue was heated beyond the point where circulation of blood could cool the skin.  
         [0006]     To address this problem, split return electrodes and hardware circuits, generically called Return Electrode Contact Quality Monitors (RECQMs), were developed. These split electrodes consist of two separate conductive foils arranged as two halves of a single return electrode. The hardware circuit uses an AC signal between the two electrode halves to measure the impedance therebetween. This impedance measurement is indicative of how well the return electrode is adhered to the patient since the impedance between the two halves is directly related to the area of patient contact. That is, if the electrode begins to peel from the patient, the impedance increases since the contact area of the electrode decreases. Current RECQMs are designed to sense this change in impedance so that when the percentage increase in impedance exceeds a predetermined value or the measured impedance exceeds a threshold level, the electrosurgical generator is shut down to reduce the chances of burning the patient.  
         [0007]     As new surgical procedures continue to be developed that utilize higher current and higher duty cycles, increased heating of tissue under the return electrode may occur. It would therefore be advantageous to design a return electrode pad which has the ability of reducing the likelihood of patient burns, while still being able to dissipate an increased amount of heat.  
       SUMMARY  
       [0008]     The present disclosure provides an electrosurgical return electrode for use in monopolar surgery. The return electrode comprises a conductive pad including a plurality of conductive elements. The return electrode further includes a plurality of temperature sensors which are each operatively engaged with a respective one of the plurality of conductive elements and which measure the temperature of a portion of a patient in contact with the respective conductive element.  
         [0009]     The present disclosure may also include a connection device which selectively enables the transfer of radio frequency current from an active electrode to at least one of the plurality of conductive elements. In operation, the connection device may be connected, disconnected, activated, deactivated and/or adjusted to a conductive element when the temperature of the patient in contact with the respective conductive element reaches a predetermined level. Specifically, if the temperature of a portion of the patient is too high, the conductive element contacting the patient at that location may be disconnected from the connection device. If the temperature of a portion of the patient in contact with a conductive element is cool enough, the conductive element in that location can be connected (or reconnected) to the connection device.  
         [0010]     It is envisioned for the plurality of conductive elements to form a grid. Additionally, each of the conductive elements may be approximately the same size. Alternatively, certain conductive elements may be a different size from the rest. For example, the conductive elements around the perimeter of the conductive pad may be relatively smaller than the remainder of the conductive elements.  
         [0011]     In an embodiment, an adhesive portion is included on the electrosurgical return electrode which facilitates the adhesion between at least a portion of the conductive pad and a patient. This adhesive portion may be capable of conducting electricity.  
         [0012]     In a particularly useful embodiment, the connection device is connectable to an electrosurgical generator and to each of the plurality of the conductive elements.  
         [0013]     It is envisioned for each of the temperature sensors to be able to measure the temperature of a patient&#39;s skin in contact therewith and/or in contact with the corresponding conductive element.  
         [0014]     The connection device may be located on the conductive pad, on an electrosurgical generator, or at a location between the conductive pad and the electrosurgical generator.  
         [0015]     It is envisioned for the electrosurgical return electrode to be entirely disposable, partially disposable, or entirely re-usable. It is further envisioned for some portions of the electrosurgical return electrode to be disposable and for some portions to be re-usable. For example, the conductive elements may be re-usable, while an adhesive may be disposable.  
         [0016]     The present disclosure also includes a method for performing monopolar surgery. The method utilizes the electrosurgical return electrode as described above. The method also includes placing the electrosurgical return electrode in contact with a patient; generating electrosurgical energy with an electrosurgical generator; supplying the electrosurgical energy to the patient via an active electrode; measuring the temperature of each portion of the patient in contact with the conductive elements using the temperature sensors; and monitoring the temperature of each portion of the patient in contact with the conductive elements. To monitor the temperature of the portions of the patient in contact with the conductive elements, the temperature of each portion of the patient in contact with a conductive elements is measured. If any temperature is too high or if it reaches a certain temperature, a user can disconnect that element from the connection device. Additionally, a user may connect or re-connect an element to the connection device if the temperature of the patient in contact with a certain conductive element reaches a predetermined level—generally a lower temperature.  
         [0017]     The present disclosure also provides an electrosurgical system for performing electrosurgery on a patient. The electrosurgical system comprises an electrosurgical generator which produces electrosurgical energy and a return electrode which is selectively connectable to the electrosurgical generator. The return electrode includes a conductive pad including a plurality of conductive elements. The return electrode further includes a plurality of temperature sensors which are each operatively engaged with a respective one of the plurality of conductive elements and which measure the temperature of a portion of a patient in contact with the respective conductive element.  
         [0018]     For a better understanding of the present disclosure and to show how it may be carried into effect, reference will now be made by way of example to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The above and other aspects, features, and advantages of the present disclosure will become more apparent in light of the following detailed description when taken in conjunction with the accompanying drawings in which:  
         [0020]      FIG. 1  is a schematic illustration of a monopolar electrosurgical system;  
         [0021]      FIG. 2  is a plan view of an electrosurgical return electrode according to an embodiment of the present disclosure, illustrating a conductive pad having a grid of conductive elements of substantially equal sizes;  
         [0022]      FIG. 3  is a plan view of an electrosurgical return electrode according to an embodiment of the present disclosure, illustrating a conductive pad having a grid of conductive elements of various sizes; and  
         [0023]      FIG. 4  is an enlarged schematic cross-sectional view of a portion of the return electrodes of  FIGS. 1-3 . 
     
    
     DETAILED DESCRIPTION  
       [0024]     Embodiments of the presently disclosed temperature regulating patient return electrode and method of using the same will be described herein below with reference to the accompanying drawing figures wherein like reference numerals identify similar or identical elements. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the disclosure in unnecessary detail.  
         [0025]     Referring initially to  FIG. 1 , a schematic illustration of a monopolar electrosurgical system  100  is shown. The electrosurgical system generally includes a return electrode  200 , a connection device  300  for connecting the return electrode  200  to a generator  120 , and a plurality of temperature sensors  400  disposed on or operatively associated with the return electrode  200  ( FIG. 4 ). In  FIG. 1 , the return electrode  200  is illustrated placed under a patient “P.” The plurality of temperature sensors  400  are in operative engagement with the return electrode  200  and operatively connect to the connection device  300  via a second cable  250 . The connection device  300  may be operatively connected to the generator  120  ( FIG. 1 ), may be operatively connected to the return electrode  200  ( FIGS. 2 and 3 ), or may be disposed between the return electrode  200  and a generator  120  ( FIG. 4 ).  
         [0026]     A surgical instrument (e.g., an active electrode) for treating tissue at the surgical site is designated by reference number  110 . Electrosurgical energy is supplied to the surgical instrument  110  by the generator  120  via a first cable  130  to cut, coagulate, blend, etc. tissue. The return electrode  200  returns the excess energy delivered by the surgical instrument  110  to the patient “P” back to the generator  120  via a wire  140 . It is envisioned for the wire  140  to be incorporated into the second cable  250 .  
         [0027]      FIGS. 2, 3  and  4  illustrate various embodiments of the return electrode  200  for use in monopolar electrosurgery. Generally, the return electrode  200  is a conductive pad  210  having a top surface  212  ( FIG. 4 ) and a bottom surface  214  ( FIG. 4 ). The return electrode  200  is designed and configured to receive current during monopolar electrosurgery. While the figures depict the return electrode  200  in a general rectangular shape, it is within the scope of the disclosure for the return electrode  200  to have any regular or irregular shape.  
         [0028]     As illustrated in  FIGS. 2, 3  and  4 , the conductive pad  210  is comprised of a plurality of conductive elements (only conductive elements  220   a - 220   f  are labeled for clarity) arranged in a regular or irregular array. Each of the plurality of conductive elements  220  may be equally-sized or differently-sized and may form a grid/array or be disposed in any other grid-like arrangement on the conductive pad  210 . It is also envisioned and within the scope of the present disclosure for the plurality of conductive elements  220  to be arranged in a spiral or radial orientation (not shown) on the conductive pad  210 . While the figures depict the conductive elements  220  in a generally rectangular shape, it is within the scope of the present disclosure for the conductive elements  220  to have any regular or irregular shape.  
         [0029]     As illustrated in  FIG. 4 , the plurality of temperature sensors  400  include individual temperature sensors (illustrated as  400   a - 400   f , corresponding to conductive elements  220   a - 220   f , respectively), which are able to measure the temperature of a patient&#39;s skin in contact therewith. The plurality of temperature sensors  400  are operatively connected to the plurality of conductive elements  220  on the top surface  212  of the conductive pad  210 . In such an arrangement, one of the plurality of temperature sensors  400  is operatively connected to one of the plurality of conductive elements  220 . For example, individual temperature sensor  400   a  may be operatively connected to conductive element  220   a . Each of the plurality of temperature sensors  400  is connected to the connection device  300  via a respective second cable  250 . For example, temperature sensor  400   a  may be connected to the connection device  300  via second cable  250   a . In the interest of clarity, each of the second cables  250  connected to each of the temperature sensors  400  is not illustrated in  FIGS. 2 and 3 .  
         [0030]     Generally, the area of the return electrode  200  that is in contact with the patient “P” affects the current density of a signal that heats the patient “P.” The smaller the contact area the return electrode  200  has with the patient “P,” the greater the current density and the greater and more concentrated the heating of tissue is. Conversely, the greater the contact area of the return electrode  200 , the smaller the current density and the less heating of the tissue. Further, the greater the heating of the tissue, the greater the probability of burning the tissue. It is therefore important to either ensure a relative high amount of contact area between the return electrode  200  and the patient “P,” or otherwise maintain a relatively low current density on the return electrode  200 .  
         [0031]     While there are various methods of maintaining a relatively low current density (including, inter alia, the use of electrosurgical return electrode monitors (REMs), such as the one described in commonly-owned U.S. Pat. No. 6,565,559, the entire contents of which are hereby incorporated by reference herein), the present disclosure ensures the return electrode  200  maintains a low current density by monitoring the temperature of each of the plurality of conductive elements  220  of the return electrode  200 .  
         [0032]     Each temperature sensor  400  of the present disclosure has the ability to measure the temperature of the patient “P” that is in contact therewith. Further, each conductive element  220  of the present disclosure may be connected and/or disconnected to the connection device  300  or may be activated and/or deactivated as needed, or may be adjusted as needed. When the temperature of the patient “P” in contact with a particular conductive element  220  reaches a predetermined level, that conductive element  220  may either be connected, disconnected, activated, deactivated or adjusted as needed. For example, if a conductive element (e.g.,  220   a ) along the perimeter of the conductive pad  210  becomes relatively hot, that conductive element  220   a  may be disconnected from the connection device  300 , deactivated or adjusted to receive a lower amount of energy. In this example, the conductive element  220   a  would not receive any more energy or receive a reduced amount of energy and the temperature in the area of the patient “P” contacting the conductive element  220   a  would consequently no longer rise. It is envisioned and within the scope of the present disclosure for the disconnection/re-connection, deactivation/reactivation of the conductive elements  220  to occur automatically as a result of an algorithm or the like provided in the electrosurgical generator  120 .  
         [0033]     It is also envisioned and within the scope of the present disclosure for a disconnected conductive element, e.g.,  220   a , to be reconnected to the connection device  300  when the temperature of the patient “P” in contact with the corresponding temperature sensor  400   a  falls to a relatively lower temperature (i.e., cools down). Utilizing these features, the temperature of the return electrode  200  can be relatively consistent throughout the entire surface thereof, thus reducing the possibility of “hot spots” and patient burns.  
         [0034]     During electrosurgical use of the return electrode  200 , portions of the perimeter of the return electrode  200  may become hot at a faster rate than the center of the return electrode  200 . In such a situation, as seen in  FIG. 3 , it may be desirable to have the conductive elements  220  near the perimeter of the return electrode  200  be smaller than the remaining conductive elements  220 . Monitoring the temperature of the patient “P” in contact with the smaller conductive elements  220  would allow greater control of the overall temperature of the portions of the patient “P” in contact with the return electrode  200 . Thus, the return electrode  200 , as a whole, would be able to receive a greater amount of current, as some new procedures necessitate.  
         [0035]     To further limit the possibility of patient burns, it is envisioned for an adhesive layer  500  to be disposed on the return electrode  200 , as illustrated in  FIGS. 2 and 3 . The adhesive layer  500  may be conductive and may be made from materials that include, but are not limited to, a polyhesive adhesive; a Z axis adhesive; or a water-insoluble, hydrophilic, pressure-sensitive adhesive and is desirably made of a polyhesive adhesive. Such materials are described in U.S. Pat. Nos. 4,699,146 and 4,750,482, the entire contents of each of which are herein incorporated by reference. A function of the adhesive layer  500  is to ensure an optimal surface contact area between the return electrode  200  and the patient “P” and thus to limit the possibility of a patient burn.  
         [0036]     It is envisioned for the return electrode  200  to be entirely disposable, entirely re-usable, or a combination thereof. In one embodiment, the conductive elements  220  are re-usable, while the adhesive layer  500  is disposable. Other combinations of disposable/re-usable portions of the return electrode  200  are envisioned and within the scope of the present disclosure.  
         [0037]     It is envisioned that a multiplexer  260  may be employed to control switching of the plurality of conductive elements  220 , as illustrated in  FIG. 4 . For example, it is envisioned that the multiplexer  260  may be configured to regulate the current in any fashion by switching on and off various amounts of the plurality of conductive elements  220 . While the multiplexer  260  is illustrated between the generator  120  and the connection device  300 , other locations for the multiplexer  260  are envisioned and within the scope of the present disclosure.  
         [0038]     A method of performing monopolar electrosurgery is also envisioned by the present disclosure. The method includes providing a return electrode  200  as described above; placing the return electrode  200  in contact with a patient “P”; generating electrosurgical energy via the generator  120 ; supplying the electrosurgical energy to the patient “P” via the active electrode  110 ; measuring the temperature of the portions of the patient “P” in contact with the plurality of conductive elements  220  via the plurality of temperature sensors  400 ; and monitoring the temperature of the portions of the patient “P” in contact with the plurality of conductive elements  220 . Utilizing this method, a conductive element (e.g.,  220   a ) may be disconnected or deactivated from the connection device  300  when the portion of the patient “P” in contact with the conductive element  220   a  reaches a predetermined temperature. Additionally, a conductive element (e.g.,  220   a ) may be connected (or reconnected) to the connection device  300 , or re-activated when the portion of the patient “P” in contact with that conductive element  220   b  falls to a predetermined temperature. As can be appreciated, this method can be utilized to maintain a relatively constant temperature where the return electrode  200  contacts the patient “P.” 
         [0039]     While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. For example, it is envisioned for the return electrode  200  to be at least partially coated with a positive temperature coefficient (PTC) material to help distribute the heat across the return electrode  200 , as described in commonly-owned U.S. Provisional Patent Application Ser. No. 60/666,798, the entire contents of which are hereby incorporated by reference herein.