Abstract:
The present disclosure provides an electrosurgical return pad current detection system for use in monopolar surgery as well as a method of using the same. The detection system includes at least one conductive pad which includes a plurality of conductive elements. The detection system further includes at least one sensor configured to measure the current levels returning to each conductive element, the current levels being input into a computer algorithm. A variable impedance controller is configured to adjust the variable impedance levels based upon output generated by the computer algorithm.

Description:
BACKGROUND  
       [0001]     1. Technical Field  
         [0002]     The present disclosure is directed to an electrosurgical apparatus and method and, more particularly, is directed to a patient return electrode pad 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 heat concentrated at that patient pad site (i.e., the smaller the surface area, the greater the current density and the greater the intensity of the heat). Hence, the overall area of the return electrode that is adhered to the patient is generally important because it minimizes the chances of current concentrating in any one spot which may cause patient burns. A larger surface contact area is desirable to reduce heat intensity. The size of return electrodes is based on assumptions of the anticipated maximum current during a particular surgical procedure and the duty cycle (i.e., 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 normal 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. Ideally, each conductive pad would receive substantially the same amount of current, therefore reducing the possibility of a pad site burn. However, this is not always possible due to patient size, incorrect placement of pads, differing tissue consistencies, etc.  
       SUMMARY  
       [0008]     The present disclosure provides an electrosurgical return electrode current distribution system for use in monopolar surgery. The system includes at least one conductive pad that includes a plurality of conductive elements, wherein the conductive elements include a pad contact impedance and a variable impedance. The system further includes at least one sensor configured to measure the current levels returning to each conductive element, wherein the current levels are input into a computer algorithm. A variable impedance controller is provided that is configured to adjust impedance levels based upon output generated by the computer algorithm.  
         [0009]     The present disclosure also provides a method for performing monopolar surgery. The method utilizes the electrosurgical system described above. The method further includes placing the system in contact with a patient, wherein the impedance levels are at some initial value; generating electrosurgical energy via an electrosurgical generator; supplying the electrosurgical energy to the patient via an active electrode; measuring the current returning to each conductive pad; detecting imbalances in current by monitoring the current returning to each conductive pad; and controlling the current entering each pad using a software program and a controller to vary impedances.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     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:  
         [0011]      FIG. 1  is a schematic illustration of a monopolar electrosurgical system according to one embodiment of the present disclosure;  
         [0012]      FIG. 2  is a plan view of an electrosurgical return electrode according to one embodiment of the present disclosure, illustrating a conductive pad having a grid of conductive elements of substantially equal sizes;  
         [0013]      FIG. 3  is a plan view of an electrosurgical return electrode according to another embodiment of the present disclosure, illustrating a conductive pad having a grid of conductive elements of varying sizes;  
         [0014]      FIG. 4  is an enlarged schematic cross-sectional view of a portion of the return electrodes; and  
         [0015]      FIG. 5  is an electrical schematic of the RF return pad current distribution system according to one embodiment of the present disclosure.  
     
    
     DETAILED DESCRIPTION  
       [0016]     Embodiments of the presently disclosed RF return pad current distribution system and method of using the same are described herein with reference to the accompanying 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.  
         [0017]     Referring initially to  FIG. 1 , a schematic illustration of an electrosurgical system  100  is shown. The electrosurgical system  100  generally includes a surgical instrument (e.g., electrosurgical pencil, electrical scalpel or other suitable active electrode)  110 , generator  120 , return electrode  200 , and variable impedance controller  300  coupled to the return electrode  200 . In  FIG. 1 , the return electrode  200  is placed under a patient “P.” Electrosurgical energy is supplied to the surgical instrument  110  by the generator  120  via a cable  130  to cut, coagulate, blend, ablate, fuse or vaporize tissue. The return electrode  200  returns energy delivered by the surgical instrument  110  to the patient “P” back to the generator  120  via return path  140 .  
         [0018]      FIGS. 2-5  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 operable to receive current during monopolar electrosurgery. While the  FIGS. 2-3  depict the return electrode  200  in a general rectangular shape, the return electrode  200  may have any suitable regular or irregular shape such as circular or polygonal. The use of the term “conductive pad” as described herein is not meant to be limiting and may indicate a variety of different pads including, but not limited to, conductive, inductive, or capacitive pads.  
         [0019]     As illustrated in  FIGS. 2, 3  and  4 , the conductive pad  210  includes a plurality of conductive elements (only conductive elements  220   a - 220   i  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 may be disposed in any other suitable grid-like arrangement) on the conductive pad  210 . The plurality of conductive elements  220   a - 220   f  may also be arranged in a suitable spiral or radial orientation (not shown) on the conductive pad  210 .  
         [0020]     As illustrated in  FIG. 4 , sensor  400  includes an array of individual sensors (illustrated as  400   a - 400   f , corresponding to conductive elements  220   a - 220   f , respectively), which are operable to measure the amount of current returning to each pad. The sensor  400  may be coupled to the plurality of conductive elements  220  on the top surface  212 , bottom surface  214  of the conductive pad  210  or anywhere therebetween. Moreover, sensor  400  may be located outside of conductive pad  210 .  
         [0021]     In one arrangement, one sensor  400  is coupled or operatively connected to one of the plurality of conductive elements  220 . For example, individual sensor  400   a  may be coupled to conductive element  220   a . Each sensor  400  is connected to the variable impedance controller  300  via a respective cable  250 . For example, sensor  400   a  may be coupled to variable impedance controller  300  via cable  250 . In the interest of clarity, each of the cables  250  connected to each sensor  400  is not explicitly illustrated in  FIGS. 2 and 3 . Furthermore, each conductive element  220   a - f  is coupled or operatively connected to a respective variable impedance  350   a - f , which is, in turn, coupled to variable impedance controller  300 . Software program  500  may be located in a variety of locations including, but not limited to, within controller  300  or generator  120 .  
         [0022]     Sensor  400  is in operative engagement with the return electrode  200  and coupled to the variable impedance controller  300  via a cable  250 . The variable impedance controller  300  is coupled to the generator  120  ( FIG. 1 ) and may be affixed to the return electrode  200  ( FIGS. 2 and 3 ), or may be disposed between the return electrode  200  and a generator  120  ( FIG. 4 ).  
         [0023]     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 which directly affects tissue heating at the contact site. 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 relatively 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 .  
         [0024]     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), the present disclosure ensures that return electrode  200  maintains a low current density by sensing and subsequently varying the amount of current returning to each of the plurality of conductive elements  220  of the return electrode  200 .  
         [0025]     In one embodiment, system  100  operates as follows. Return electrode  200  is placed in substantial contact with a patient&#39;s skin. Active electrode  110  is coupled to generator  120 , which provides active electrode  110  with RF current. Once active electrode  110  comes into contact with the patient&#39;s skin, RF current flows through the body towards return electrode  200 . Return electrode  200  includes a conductive pad  210  having a plurality of conductive elements  220   a - f , each of which is coupled to a respective sensor  400   a - 400   f . Sensors  400   a - f  measure the amount of current returning to each conductive element  220   a - f . Ideally, substantially the same amount of current will be flowing into each element  220   a - f , however, this is unlikely to be the case. Software program  500  receives data from sensors  400   a - f  and drives variable impedance controller  300 . Controller  300  is coupled to variable impedances  350   a - f  and may increase or decrease the levels of each variable impedance  350  in order to ensure that substantially equal amounts of current are flowing through each conductive element  220   a - f.    
         [0026]     Variable impedance controller  300  may be located in a number of different areas including within generator  120 . Moreover, variable impedance controller  300 , sensors  400   a - f , conductive pad  210   a - f , and software program  500  are all in electrical communication with one another. For example, software program  500  may be located in a variety of different locations including, but not limited to, variable impedance controller  300 , sensor  400  (or a common sensing device), or generator  120 . Similarly, variable impedance controller  300  may be coupled or operatively connected to software program  500  and may house software program  500 . Similarly, as mentioned hereinbefore, generator  120  could contain one, some or all of these elements.  
         [0027]     Variable impedance controller  300  may be selected from a number of suitable designs. Some designs may include proportional-integral-derivative control or other forms of digital control. Moreover, variable impedance controller  300  may receive many suitable types of signals including but not limited to control signals, neural network, and fuzzy logic algorithms.  
         [0028]     Referring now to  FIG. 5 , another embodiment of the return pad current distribution system is shown.  FIG. 5  shows body impedance (BI)  310 , pad contact impedance (PI)  320 , and variable impedance(VI)  350  cascaded and interconnected. Body impedance  310  will likely vary depending upon which part of the body is in contact with conductive pad  210 . That is, the physiological characteristics may vary significantly from patient to patient and from one sensor to another. Patients may vary in their respective amounts of adipose tissue and certain location sites may be more fatty, hairy, or scarred than another. Electrosurgical system  100  takes into account these factors while providing substantially equal amounts of current through each conductive element  220 . Each variable impedance  350  works symbiotically with controller  300 , sensor  400 , and software  500  to create substantially equal current flow through each conductive element  220   a - f.    
         [0029]     Variable impedance  350  may take the form of a variable resistor or rheostat. Potentiometers and other suitable devices are also envisioned. Variable impedance  350  is coupled to variable impedance controller  300  and receives directions from controller  300 . Variable impedance  350  may be configured in a number of different arrangements. Variable impedance  350  may be attached to conductive pad  210 , as shown in  FIG. 5 , or even housed within conductive pad  210 .  
         [0030]     The present disclosure also provides a method for performing monopolar surgery. The method may utilize the electrosurgical system  100  described above. The method further includes placing the electrosurgical system  100  in contact with a patient; generating electrosurgical energy via an electrosurgical generator  120 ; supplying the electrosurgical energy to the patient via an active electrode  110 ; measuring the current returning to each conductive element  220   a - f ; detecting imbalances in current by monitoring the current returning to each conductive element  220   a - f ; and controlling the current entering each element  220   a - f  using a software program  500  and a controller  300  to vary impedances  350   a - f.    
         [0031]     The method may further include setting impedances  350   a - f  to certain predetermined levels using controller  300  in order to direct current towards or away from certain areas.  
         [0032]     While several embodiments of the disclosure are 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. For instance, any mention of devices such as potentiometers and rheostats presupposes that these devices may be digital in nature. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments.