Patent Application
20070106288
This invention relates to an electrosurgical apparatus and method, in particular an electrosurgical apparatus wherein a fluid regulator on a distal end of a shaft regulates the flow of fluid over an active electrode and into an ingress port on the shaft. In one embodiment the fluid flow into the ingress port is regulated such that the temperature of the electrode is controlled, the plasma generated at the electrode is stabilized, and bubbles formed around the electrode and the target site during the procedure are removed, for better visualization of the electrode and the target site.
An electrosurgical system as shown for example in
In treating the target site, the current across the electrodes is applied in several ways, e.g., the current is passed directly into the target site by direct contact with the electrodes such that the current passes into and heats the target site; or the current is passed indirectly into the target site through an electrically conductive fluid located between the electrode and the target site also to heat the target site; or current is passed into an electrically conductive fluid disposed between the electrodes to generate plasma which is used to ablate tissue at the target site. In the procedure wherein plasma is generated, the current does not pass in to the tissue. In various procedures, the conductive fluid is an electrolyte such as isotonic saline and other fluids having conductivity similar to isotonic saline and body fluids. Examples of an electrosurgical apparatus, system and methods of using plasma to treat a target site are described in commonly assigned U.S. Pat. No. 6,149,620 and U.S. patent application Ser. No. 09/457,201, herein incorporated by reference for all purposes.
In using the apparatus (10) to generate plasma to treat tissue in a “wet field” procedure, the tip (14) of the shaft (11) comprising the active electrode is placed in a conductive fluid on the target site. For the present purposes, a wet field procedure is a procedure wherein the target site is flooded with a conductive fluid. With reference to
With reference to
With reference to
In the prior art, one possible approach to removing the bubbles from the target site is to increase the fluid flow to the site, while simultaneously suctioning off the fluid from the site at a rate such that the bubbles are captured in the fluid flow. While this approach will remove bubbles, an undesirable consequence of the increase fluid flow across the electrode is that the temperature of the electrode is lowered, which has the undesirable effect of decreasing the stability of the plasma generated. Thus, with this approach, in order to maintain the stability of the plasma, the current through the electrodes is increased to maintain the temperature of the electrode at the desired plasma-generating temperature level.
However, on increasing the in current to the electrode, besides increasing the temperature of the electrodes, the temperature of the conductive fluid around the electrode also increases, which has the undesirable consequence of increasing the risk of burns to the patient and heat damage to the tissue.
Accordingly, in view of the above disadvantages of in the prior art, there is a need for a better way to stabilize the plasma at the electrodes, and also to control bubbles at the target site, without increasing the risk of heat damage to the tissue, or burns to the patient. It is thus an objective of the present invention to address these needs.
In one embodiment, the present apparatus is an electrosurgical instrument comprising: a shaft comprising a distal end section including a distal tip; and an active electrode disposed near the distal tip, wherein the distal end section comprises a fluid collection chamber. In one embodiment the fluid collection chamber comprises an ingress port for suctioning a fluid flow over the active electrode and into the fluid collection chamber; a regulator adapted to adjust the fluid flow through the ingress port; and an aspiration port for exhausting the fluid from the fluid collection chamber.
In another embodiment, the apparatus is an electrosurgical instrument for treating a target site comprising: a shaft comprising a distal end section, a distal tip, and a fluid aspiration lumen extending to the distal tip. On the distal end is a fluid collection chamber in fluid communication with the aspiration lumen, the fluid collection chamber comprising: a fluid ingress port such that fluid in the vicinity of the target site may be drawn therein at a first flowrate, and transported into the aspiration lumen; and a regulator, the regulator adapted to adjust the first flowrate such that the first flowrate is independent of a third flowrate through the aspiration lumen; and an active electrode arranged at the distal end section such that fluid entering the ingress port is drawn across the active electrode.
In various embodiments of the apparatus, the fluid ingress port comprises a first cross section area, and the regulator comprises a second cross section area such that the ratio of the second cross section area to the first cross section area is equal to or greater than about ⅗; in another embodiment the ratio of the second cross section area to the first cross section area is equal to or greater than about 1; while in a further embodiment the ratio of the second cross section area to the first cross section area is equal to or greater than about 3/2. In one embodiment, the second section area is about 0.0030 square inch to about 0.0050 square inch. In various embodiments the regulator comprises one or more openings formed into the fluid collection chamber; in one embodiment the regulator comprises one more valves.
In another embodiment, the present method comprises performing an electrosurgical procedure on a target site, including the steps of: applying a high-frequency voltage potential difference between an active electrode and a return electrode of an electrosurgical apparatus in the presence of an electrically conductive fluid, in close proximity to the target site; removing a first fluid stream from the target site through an ingress port on the electrosurgical apparatus, at a first flow rate, wherein the first fluid stream comprises fluids in contact with the active electrode; suctioning a second fluid stream from said target site through a regulator on the apparatus; wherein the first fluid stream flow is regulated by the second stream flow and bubbles at the target site are removed for improved visualization of the target site during the procedure.
Advantageously, with the present apparatus and method, since the flow of fluid through the ingress port and across the active electrode is regulated by the fluid flow through the regulator, the bubbles generated at the electrode and target site are removed, without increasing the fluid flow across the active electrode. Consequently, with the present apparatus and method, the plasma at the active electrode is stabilized without increasing the current through the electrodes. Also, because the current through the electrodes is not increased, heating of the electrode is not increased, and therefore the risk of causing thermal injury to the patient is not increased.
Embodiments of the present apparatus and methods are illustrated schematically in the following Figures, and described in greater detail in the following sections of the specification.
The following description of preferred embodiments of the apparatus and method is provided in conjunction with the illustrations of
With reference to
With reference to
In one embodiment the ingress port (50) is provided with a first cross-section area (51) for suctioning fluids from the target site (52) into the fluid collection chamber. Deployed across the ingress port, or at least partly circumscribing the ingress port, is an active electrode (46). In this embodiment, the regulator (54) is designed to allow entry of fluid into the fluid chamber, and comprises one or more openings (54) spaced away from the ingress port.
In various embodiments the fluid ingress port (50) comprises a first cross section area, and the regulator comprises a second cross section area such that the ratio of the second cross section area to the first cross section area is equal to or greater than about ⅗; in another embodiment this ratio is equal to or greater than about 1, while in a further embodiment this ration is equal to or greater than about 3/2. In one embodiment the cross section area of the second opening is in the range of about 0.0030 square inch to about 0.0050 square inch. Thus, in this embodiment, since the volume of the fluid chambers fixed, therefore fluid flow through the regulator can be adjusted to regulate the flow of fluid through the ingress port and across the active electrode. Under normal operating conditions, the above-noted ratio has been found to provide sufficient fluid flow across the active electrode such that the plasma is stabilized, the temperature of the fluid is controlled, and bubbles are removed without the need to increase the current through the electrodes.
In various embodiments an aspiration port (56) having a third cross-section area (57) for aspirating and exhausting fluids from the fluid collection chamber is provided. In one embodiment, the aspiration port is connected to a vacuum system (not shown) for evacuating fluid from the collection chamber.
The fluid cap or sleeve in various embodiments is comprised of conventional material as, for example, the conductive material of the shaft; in alternative embodiments the material is non-conductive as, for example, a polymer or a ceramic. In one embodiment the fluid cap or sleeve is adapted to function as a return electrode; in this embodiment, the fluid cap as illustrated in
As is illustrated in
In a preferred embodiment as illustrated in
Without desiring to be bound by any theory pertaining to the results achieved by the present apparatus and method, it is believed that because the holes of the regulator into the fluid collection chamber are either as small as and or smaller than the bubbles, the bubbles are prevented from escaping through the regulator. In one embodiment as illustrated in Table 1, the holes are sized to provide an opening of about 0.0030 square inch to about 0.0050 square inch into the collection chamber. As is illustrated schematically in
In experiments conducted to with the present apparatus to determine the stability of the plasma at the electrodes for various first and second cross-section areas of the present apparatus and fluid flow, it was observed that sufficient stable plasma forms when the ratios of the second cross-section area to the first cross-section area equal to or greater than about 1, and in particular to a ratio equal to or less than about 3/2. A summary of the experiments results is provided in Table 1.
In various embodiments, the fluids aspirated from the target site through the ingress port comprise gas bubbles, water vapor, conductive fluids, disintegrating body tissue, bone fragments and body fluids. In one procedure, as illustrated in
In another embodiment the present apparatus as illustrated for example in
In one embodiment the present method is a procedure of performing an electrosurgical procedure on tissue at a target site and removing bubbles that impair visualization of the target site, comprising applying a voltage potential difference between an active electrode of an electrosurgical apparatus in close proximity to the target site and a return electrode in the presence of an electrically conductive fluid on the target site; aspirating a first stream of material from the target site through a fluid ingress port of the apparatus at a first flow rate; suctioning a second stream of electrically conductive from the target site through a regulator of the apparatus; whereby the first flow rate is regulated by the suctioning step, thereby treating the target site and removing bubbles that impair visualization of the target site.
In one embodiment first flow rate into the fluid chamber and across the active electrode through the ingress port is regulated such that it is substantially constant. In accordance with the present apparatus the constant flow rate is achieved by dimensioning the ingress port to have a first cross-section area, and the ingress port to have a second cross-section area such that the ratio of said second cross-section area to said first cross-section area is equal to or greater than about ⅗. In other embodiments the ratio of the second cross-section area to first cross-section area is equal to or greater than about 1, and in a preferred embodiment the ratio of the second cross-section area to said first cross-section area is equal to or less than about 3/2. As is illustrated in Table 1 and described above, the second cross-sectional area is sized for an opening of about 0.0030 square inch to about 0.0050 square inch in the apparatus.
In various embodiments, the method further comprises aspirating the bubbles from the fluid collection chamber to maintain visualization of the target site. As will be appreciated by one ordinarily skilled in the art, the present method may be used to treat target tissue includes ablating, puncturing, and cutting the target tissue. Depending on the tissue being treated, in one procedure a voltage of about 50 volts to 1000 volts can be applied; in other procedures, a voltage in the range of 200 volts to 350 volts can be applied. In various embodiment treatment include directing a conductive fluid to the target tissue so as to ablate, puncture, and volumetrically remove tissue.
While the invention is described with reference to the Figures and method herein, it will be appreciated by one ordinarily skilled in the art that the invention can also be practiced with modifications that are within the scope of the claims. Thus the scope of the invention should not be limited to the embodiments as described herein, but is limited only by the scope of the appended claims.
