RF RETURN PAD CURRENT DETECTION
1. Technical Field
The present disclosure is directed to an electrosurgical apparatus and method, and, is particularly directed to a patient return electrode pad and a method for performing monopolar surgery and RF ablation using the same. 10
During electro surgery, 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 15 electro surgery, 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, ablating and/or coagulating tissue. The patient return electrode is placed at a remote site from the 20 source electrode and is typically in the form of a pad adhesively adhered to the patient.
The return electrode typically has a relatively large patient contact surface area to minimize heat concentrations at that patient pad site (i.e., the smaller the surface area, the greater 25 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 30 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 35 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 40 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 45 could cool the skin.
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 50 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 55 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 60 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.
As new surgical and therapeutic RF procedures continue to be developed that utilize higher current and higher duty 65 cycles, increased heating of tissue under the return electrode may occur. Ideally, each conductive pad would receive sub
stantially 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. It would therefore be advantageous to design a return electrode pad which has the ability to detect and correct a current imbalance between pads, therefore reducing the likelihood of patient burns.
The present disclosure provides an electrosurgical return pad current detection system for use in monopolar surgery. The detection system comprises a plurality of conductive pads which include a plurality of conductive elements. The detection system further includes a plurality of sensors which sense the current returning to each conductive pad as well as a comparator for sensing the difference in current between a plurality of conductive pads.
The present disclosure may also include an ablation generator which may regulate the amount of power delivered to a surgical device. In operation, the return pad current detection system is placed in contact with the patient. A generator enables the transfer of radio frequency current from an active electrode to at least one of a plurality of conductive elements. The plurality of sensors measures the amount of current returning to each pad. This information in then processed a comparator which detects any possible imbalances in current between the pads. If there is a substantial imbalance the user is warned of such a situation and the generator automatically corrects the imbalances.
In one embodiment of the present disclosure the current sensor of each conductive pad is a current sense transformer. Alternatively, the current sensor could be, inter alia, a noninductive sense resistor.
In another embodiment of the present disclosure the comparator is a differential or instrumentation amplifier.
It is envisioned for the generator to utilize the information provided by the comparator to alert the user of potential hazardous conditions and to prevent injury. This may be achieved using a variety of differing methods including safety control, neural network, or fuzzy logic algorithms.
In one embodiment, a full-wave rectifier is connected to the current sensor in order to convert the returning current signal from alternating current to direct current.
The present disclosure also includes a method for performing monopolar surgery. The method utilizes the return pad current detection system as described above. The method also includes placing the return pad current detection system in contact with a patient; 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 comparing the current returning to one conductive pad with the current returning to each of the remaining pads; warning the user of possible hazardous conditions; and substantially correcting or regulating the imbalances among pads.
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
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: