Patent Description:
Particulate matter in aerosol form is commonly encountered during surgical procedures. For example, it can be either utilized to deliver a therapeutic agent or can be experienced as a result of performing a surgical procedure. Examples of particulate-based therapeutic agents are the delivery of agents for effecting rapid clotting of blood or for treating diseases such as cancer. A common example of particulate matter created as a result of performing a surgical procedure is that experienced when using "energy-based" surgical instruments. Energy-based surgical instruments are powered in some manner in order to deliver a therapeutic effect such as cutting or coagulating tissue. Although there are several modes of action such as radiofrequency (RF), ultrasonic and laser, all of these energy-based instruments create particulate matter as a by-product of their mode of action.

Particulate matter created in an aerosol form by energy-based instruments is problematic for at least two reasons. Firstly, it rapidly obscures the visual field of the surgeon, and therefore slows the surgical procedure and creates risk of accidental harm to the patient caused by poor visibility. Secondly there are concerns that long-term exposure to particulate matter created by these instruments may represent a hazard for healthcare workers. Historically vacuum-based systems have been used to extract the aerosol particulate matter from the surgical field. However, because this is a dilution-based process it is inefficient at rapidly removing the particulate matter and improving the visual field quality. In addition to this, and in the case of surgical procedures that require gas insufflation to create an operative space, such as laparoscopic surgery for example, the resulting exchange of gas dries and desiccates tissue which has a detrimental effect for the patient. As a result of this and the fact that vacuum-based systems are loud and cumbersome, the adoption of vacuum-based systems has been poor.

<CIT> discloses an alternative approach for managing particulate matter in surgical procedures via an apparatus for the reduction and removal of surgical smoke and other aerosol particulates generated during electrosurgical procedures. The apparatus generates a stream of electrons from a pointed electrode placed near the surgical site, such as within an abdominal cavity, and the electrons emitted from the electrode attach themselves to the aerosol particles suspended nearby. The apparatus further establishes an electrical potential difference between the electrode and the patient for attracting the ionized particles away from the surgical site and thus improving the surgeon's view of the site.

However, the electrode that is deployed into the abdomen for example, requires an additional incision within the abdominal wall which is undesirable. The effectiveness of the apparatus is also dependent on the positioning of the electrode relative to the site of surgery and other surgical instruments, and is thus subject to the surgeons experience and skill.

<CIT> discloses a surgical instrument comprising a surgical device which is actuatable for performing a surgical procedure. The device comprises an electrically conductive portion and an ion-generating electrode integrally arranged with respect to the surgical device, the ion-generating electrode having an ion emission zone. The ion emission zone of the ion-generating electrode and the electrically conductive portion of the surgical device are moveable relative to each-other between a first position and a second position, so that the ion emission zone can be used to generate electrons therefrom for ionising aerosol particles.

We have now devised a surgical assembly, surgical system and an electrode assembly which address at least some of the above-mentioned limitations.

According to a first aspect of the present invention there is provided a surgical assembly as defined in claim <NUM>.

In an embodiment, the controller is arranged to disable the application of the second signal to the electrode upon receiving a sensing signal representative of a deactivation of the first signal.

In an embodiment, the controller comprises a timing arrangement for disabling the application of the second signal to the electrode a predefined time after receiving a sensing signal representative of a deactivation of the first signal.

In an embodiment, the sensing arrangement comprises a sensor for sensing an activation of one or more actuators that activate(s) the first signal. For example, the actuators may be associated with a surgical generator, such as an electrosurgical generator or an ultrasonic generator, for generating the first signal, and may be disposed upon the tool. Alternatively, or in addition thereto, the sensing arrangement comprises a sensor for directly sensing the first signal.

In an embodiment, the assembly further comprises a surgical generator for generating the first signal and the first signal is communicated to the tool via a cable. Accordingly, the sensor of the sensing arrangement may be arranged to sense the generation or activation of the first signal along the cable.

In an embodiment, the assembly further comprises an override actuator for enabling the application of the second signal to the electrode independently of the activation status of the first signal. It is envisaged that this facility will provide a surgeon with the option of manually activating the second signal for removing particles suspended proximate the surgical site. The override actuator may be disposed on the tool or the electrical generator, and may comprise a push-button, for example, to enable the surgeon to commence a smoke clearing period.

The electrode is disposed upon the tool, and in an embodiment, the electrode extends around the tool, proximate a distal end thereof. The electrode comprises a collar or ring of electrically conductive material disposed upon an electrically insulative carrier. The carrier and collar are centered upon a longitudinal axis of the tool and in an embodiment, the carrier comprises a continuous, peripherally extending window for electrically exposing at least a continuous, circumferentially extending portion of the collar.

In an alternative embodiment, the carrier comprises a plurality of circumferentially separated windows for electrically exposing portions of the collar around the tool. In an embodiment, the windows are shaped, such as square and/or triangular, for electrically exposing a shaped portion of the collar. Alternatively, the collar may be shaped to provide the desired shaping of portions of the collar.

In an embodiment, the tool comprises a handle and a shaft which is coupled at a proximal end thereof to the handle, and wherein the electrode is disposed proximate a distal end of the shaft. The electrode may extend around the tool and particularly the shaft. In an embodiment, the electrode is offset from the shaft and may comprise a linear section of wire, or a rod having a sharpened end. In a further alternative, the electrode may comprise a blade.

In an embodiment, the electrode diverges from the shaft, in a direction which is along the shaft toward a distal end thereof.

In an alternative embodiment, the electrode is disposed upon the tool and comprises a plurality of electrically conductive elements circumferentially separated around the tool. The elements are electrically coupled with a respective electrically conductive pathway which extends to a proximate end of the tool, for communicating the second signal from the electrical generator to the respective element. The elements may comprise electrical wires.

In an embodiment, the tool comprises a handle and a shaft which is coupled at a proximal end thereof to the handle, and the electrode is disposed proximate a distal end of the shaft. In an embodiment, the assembly further comprises a heater for heating a region of the shaft disposed longitudinally between the electrode and the distal end of the shaft.

In an embodiment, the shaft comprises a profiled outer surface at least in the region disposed longitudinally between the electrode and the distal end of the shaft.

In an embodiment, the assembly further comprises a monitoring circuit for monitoring a build-up of material on the shaft in the region disposed longitudinally between the electrode and the distal end of the shaft. The monitoring circuit is further arranged to monitor the total current flowing through the patient due to the current flowing from the electrode to the patient. In a first embodiment, the monitoring circuit comprises a switch which is reconfigurable between a first configuration for coupling the electrode with the tool along a first electrical pathway, and a second configuration for coupling the tool-piece with the surgical generator along a second electrical pathway. The monitoring circuit further comprises a current sensor, such as an ammeter, for monitoring the current flowing directly between the electrode and patient within the first electrical pathway, when the switch is configured in the first configuration, and for separately monitoring the current flowing directly between the electrode and the tool along the second electrical pathway, when the switch is configured in the second configuration.

In alternative embodiment, the monitoring circuit comprises a guard collar disposed around a distal end of the shaft of the tool, and the monitoring circuit comprises a first electrical pathway between the electrode and the guard collar, the first pathway comprising a first current sensor for monitoring the electrical current flowing in the first pathway, namely between the electrode and guard collar. The monitoring circuit further comprises a second electrical pathway between the electrode and patient, the second pathway comprising a second current sensor for monitoring the electrical current flowing in the second pathway, namely between the electrode and the patient.

In an embodiment, the electrode further comprises an electrically conductive pathway which extends from the collar to a proximate end of the tool, for communicating the second signal from the electrical generator to the collar.

In an embodiment, the tool comprises a tool-piece disposed at a distal end thereof, for performing the surgical procedure. The assembly may further comprise a voltage compensation circuit for maintaining a substantially constant voltage difference between the tool-piece and patient tissue independently of a separation between the tool-piece and the patient tissue. The voltage compensation circuit is arranged to maintain the substantially constant voltage difference as the current passing between the tool-piece and patient tissues varies between <NUM>-100µA. In an embodiment, the voltage compensation circuit is arranged to set the voltage difference between 3kV and 15kV, and preferably between 3kV and 8kV.

According to a second aspect of the present invention, there is provided a surgical system for use in performing a surgical procedure on a patient, the system comprising:.

Further features of the surgical system may comprise one or more of the features of the surgical assembly.

In an embodiment, there is provided an electrode assembly for removing particles suspended proximate a site of a surgical procedure performed on a patient, the assembly comprising an electrode comprising a plurality of electrically conductive elements, communicatively couplable with an electrical generator and configured to receive an electrical signal, the assembly further comprising a controller communicatively coupled with a sensing arrangement and which is arranged to receive a sensing signal from the sensing arrangement representative of a proximity of the electrically conductive elements to patient tissue, the controller being arranged to selectively admit the electrical signal to the conductive elements in dependence of the sensing signal.

In an embodiment, the electrode is disposed upon a surgical tool. The sensing arrangement may comprise a plurality of current sensors for separately sensing an electrical current flowing along each conductive element. In the event that the sensed electrical current exceeds a pre-determined threshold, which may be indicative of the element passing to close to patient tissue, or otherwise contacting tissue, the sensing arrangement is arranged to output a sensing signal to the controller causing the controller to inhibit or otherwise electrically isolate the conductive element from the electrical generator.

In an embodiment, the controller comprises a switching arrangement for selectively electrically isolating the conductive elements.

In an embodiment, the controller comprises a timer for admitting the electrical signal to the conductive elements according to a timing sequence. The timing arrangement thus enables the elements to be separately addressed by the electrical signal according to a desired sequence.

Whilst the invention has been described above, it extends to any inventive combination of features set out above or in the following description. Although illustrative embodiments of the invention are described in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to these precise embodiments.

Furthermore, it is contemplated that a particular feature described either individually or as part of an embodiment can be combined with other individually described features, or parts of other embodiments, even if the other features and embodiments make no mention of the particular feature. Thus, the invention extends to such specific combinations not already described.

The invention may be performed in various ways, and, by way of example only, embodiments thereof will now be described, reference being made to the accompanying drawings in which:.

Referring to <FIG> of the drawings, there is illustrated a surgical assembly <NUM> according to an embodiment of the present invention for use during a surgical procedure, such as an electrosurgical, ultrasonic or laser based surgical procedure. The assembly <NUM> comprises a surgical tool <NUM>, which may typically comprise a tool which is held by the surgeon for cutting and/or cauterising tissue. In the embodiment illustrated, the tool <NUM> comprises a handle <NUM> and an elongate shaft <NUM> which is coupled at a proximal end thereof to the handle <NUM>. The shaft <NUM> is formed of a dielectric material and comprises an electrical conductor <NUM>, which extends through the shaft <NUM>, typically along a longitudinal axis thereof. The conductor <NUM> extends out from a distal end of the shaft <NUM> and is thus electrically exposed, forming or joining to the tool-piece <NUM> that is responsible for delivering the energy to the tissue. The tool-piece is shaped to facilitate the surgical procedure and may comprise a wire formed into an arcuate section, or an L-section, or a jaws of a forceps or graspers, for example; or a jawed/grasper arrangement suitable for sealing of vessels, for example (not shown).

Referring to <FIG> and <FIG> of the drawings, the assembly <NUM> further comprises an electrode <NUM> disposed upon the tool shaft <NUM>, proximate a distal end thereof. In a first embodiment, the electrode <NUM> extends circumferentially around the shaft <NUM> and is centred upon a longitudinal axis of the shaft. The electrode <NUM> comprises an electrically conductive collar <NUM> which is encased within an electrically insulative sheath (not shown) or carrier <NUM>. In this respect, the carrier <NUM> is disposed radially between the collar <NUM> and the shaft <NUM> of the tool <NUM> and thus acts to minimise any electrical current flowing directly between the collar <NUM> and the conductor <NUM> which extends along the tool <NUM>. The electrode collar <NUM> is electrically exposed circumferentially thereof, along a radially outward facing side of the electrode <NUM>, by a circumferentially extending window <NUM> formed in the radially outward facing side of the carrier <NUM>, thus exposing a ring shaped portion <NUM> of the collar (<FIG>). In an alternative embodiment, the carrier <NUM> may comprise a plurality of windows <NUM> formed in the radially outward facing side of thereof, which are angularly separated around the electrode <NUM>, for electrically exposing portions of the collar <NUM>. The windows <NUM> may comprise a square (second embodiment - <FIG>) or triangular shape (third embodiment - <FIG>), or a combination thereof for example, and act to electrically expose shaped portions of the collar <NUM>. In each of the first, second and third embodiments of the electrode, the collar <NUM> is arranged to project through the opening(s) in the carrier <NUM> and thus extend above an outer surface of the carrier <NUM>. The raised portions of the collar <NUM> facilitates the emission of electrons therefrom for ionising particulate material. In a fourth embodiment as illustrated in <FIG> of the drawings, the collar <NUM> may extend longitudinally of the shaft <NUM>, beyond a distal end of the carrier <NUM>, to electrically expose a distal edge or ring of the collar <NUM> (<FIG>). In this case, the distal edge may be sharpened to similarly facilitate the emission of electrons. In a further alternative embodiment (which is not illustrated), the collar <NUM> may be patterned directly to form the desired shaping and disposed upon the radially outward facing side of the carrier <NUM>, rather than being encased within the carrier <NUM> and the desired shaping of the exposed portions of the collar <NUM> being determined by the shaping of the windows in the carrier <NUM>.

In a fifth embodiment (as illustrated in <FIG> of the drawings), the electrode <NUM> may instead comprise a plurality of electrically conductive elongate elements <NUM>, such as electrically exposed wires, orientated in a substantially parallel orientation, and parallel with a longitudinal axis of the shaft <NUM> of the tool <NUM>. The elements <NUM> are angularly separated around the shaft <NUM> and are electrically coupled at their proximal ends by an electrically conductive ring <NUM> which extends circumferentially around the tool shaft <NUM>.

The electrode <NUM> of each of the above embodiments further comprise an electrically conductive pathway <NUM> which extends from the respective collar <NUM> of the first-fourth embodiments or ring <NUM> of the fifth embodiment, along the shaft <NUM> toward the handle <NUM>, where the pathway terminates at an electrical connector <NUM>. The pathway <NUM> may comprise an electrically insulated wire for example and, via the connector <NUM>, is arranged to electrically communicate an electrical signal from an electrical generator <NUM> to the collar <NUM> or ring <NUM>. The generator <NUM> may comprise a high voltage electrical generator capable of generating <NUM>-20kV, preferably <NUM>-10kV, and is arranged to generate a direct current (DC) voltage waveform that is used for establishing an electrical field from the electrically exposed portions of the collar <NUM> or elongate elements <NUM>, proximate a site of a surgical procedure.

In a sixth embodiment, as illustrated in <FIG> and <FIG> of the drawings, the electrode <NUM> comprises an elongate rod or wire <NUM> having a sharpened distal end. The electrode <NUM> may extend substantially parallel to the longitudinal axis of the shaft <NUM> (<FIG>) or diverge away from the shaft <NUM> in a direction which is along the shaft <NUM> toward a distal end thereof (<FIG>). In both situations, a proximal end of the electrode <NUM> is radially spaced from an outer surface of the shaft <NUM> by a first offset X and a distal end of the electrode <NUM> is longitudinally spaced from a distal end of the shaft <NUM> (namely where the conductor <NUM> becomes exposed), by a second offset Y. In situations where the tool-piece <NUM> comprises a forceps for example, as shown in <FIG> of the drawings, the first offset is directed out of a plane in which the jaws J1, J2 of the forceps rotate. In this respect, in situations where the jaws rotate in an x-y plane for example, then the first offset extends laterally out of the x-y plane, and comprises a component to the separation which is along the z-axis.

The first and second offsets X, Y minimise any undesirable electrical tracking/conductance directly between the electrode <NUM> and the conductor <NUM> or tool-piece <NUM>, caused by a build-up of conductive material (not shown), such as fluid and tissue resulting from the surgical procedure, upon the shaft <NUM>. The build-up of conductive material on the shaft <NUM> provides an electrical pathway between the exposed wire <NUM> of the electrode <NUM>, and tool-piece <NUM>, and this pathway can be further reduced by profiling an outer surface of the shaft <NUM> with an external thread 112a or corrugations as illustrated in <FIG> of the drawings. The profiling reduces the tendency of the conductive material to distribute (creep) along the shaft <NUM>, by preferentially causing the material to follow the profiling <NUM> around the shaft <NUM> (thereby increasing the creepage distance).

The electrodes <NUM> described above in connection with each of the first to sixth embodiments may be enclosed within a sheath (not shown) and retractably deployable relative to the sheath to expose the electrode <NUM>, by an actuator (not shown). Upon retracting the electrode <NUM> relative to the sheath, the sheath is arranged to wipe the electrode <NUM> and thus remove conductive material from the electrode <NUM>. In situations where the sheath (not shown) is retractable relative to the shaft <NUM> then the sheath may also be further arranged to remove any conductive material from the shaft to further minimise any electrical tracking between the electrode <NUM> and the tool-piece <NUM>.

As an alternative to the sheath, or in addition thereto, the assembly <NUM> may comprise a heater <NUM> disposed upon the tool shaft <NUM>, longitudinally between the distal end of the shaft <NUM> and the electrode <NUM>, as illustrated in <FIG> of the drawings. The heater <NUM> may comprise a coil <NUM> of encapsulated resistive wire for example which extends around the shaft <NUM>, or which may be embedded within the shaft <NUM>, and which is electrically coupled to an electrical supply (not shown) via transfer wires <NUM> for supplying electrical current through the resistive coil <NUM>. The passage of electrical current through the coil <NUM> is arranged to heat the region of the shaft <NUM> disposed longitudinally between the electrode <NUM> and the tool-piece <NUM> for drying any conductive material and fluid disposed around the shaft <NUM>, to minimise the development of an electrical pathway between the electrode <NUM> and the tool-piece <NUM>.

Referring to <FIG> of the drawings, the electrical generator <NUM> comprises an analogue closed loop control circuit <NUM> for closed loop control of the output current from the electrode <NUM>, through the patient. The operating current is influenced by the separation of the distal end of the electrode <NUM> from the patient tissue. As the electrode <NUM> approaches the patient tissue, the impedance falls. This causes the current to increase and the output voltage between the electrode <NUM> and patient to fall. The electrical generator <NUM> however, monitors the current flowing between the electrode <NUM> and the patient tissue and terminates the current as it approaches 10µA, which is typically the maximum DC current that can safely be applied to a patient. As a result, the voltage falls below a level that is sufficient to cause electrostatic precipitation.

The control circuit <NUM> primarily controls the output current of the electrical generator <NUM>. The electrical generator <NUM> comprises a 200MΩ series resistance <NUM> (see <FIG>) at the output thereof to ensure that a maximum current of 50µA under a single short circuit fault condition, i.e. if the current limit fails and the electrical generator <NUM> outputs the maximum voltage. The resistance is embodied as two separate 100MΩ resistors 632a, 632b (see <FIG>) each separately connected in series with the high voltage and low voltage output terminals of the electrical generator <NUM>. Electrical current is returned to the electrical generator <NUM> via a resistor (see <FIG>), thereby developing a voltage that is buffered and used as a process value. This value is compared with a current set point using a comparator <NUM> and the resulting error is integrated via integrator <NUM> providing a control signal for the electrical generator <NUM>. If the process value is above/below the current set point, the control signal to the electrical generator <NUM> reduces/increases. This reduces/increases the high voltage output and increases/reduces the measured current toward the target set point value.

It is possible for the error signal to become saturated as the electrical generator output saturates at approximately 10kV, thereby limiting the current available. The closed loop circuit <NUM> is designed to saturate at a variable level, allowing the output saturation voltage to be adjusted below 10kV whenever the process value current is below the set point.

This output resistance of the electrical generator <NUM> imposes an unwanted voltage drop at the output under normal operating conditions, creating a dependency between the voltage available at the output and the current being drawn. Practically, problems occur where the corona current is close to the typically 10µA patient current limit. Voltage drop across the series resistance <NUM> reduces the output voltage below what is required for efficient corona, namely ionisation of smoke particulates. Smoke clearing performance is impaired by the mandated current limit, not because of insufficient current available, but because there is insufficient voltage.

However, the voltage drop can be compensated using a voltage compensation circuit <NUM>, as illustrated in <FIG>, which is configured to engineer a corresponding increase in the voltage output from the electrical generator <NUM>. This is achieved by increasing the voltage set point by the voltage drop through the series resistance <NUM>. The circuit comprises a processor <NUM> or summation device which is arranged to receive as input the desired or target voltage and a signal representative of an electrical current flowing through the resistance <NUM> This current is already known by the closed loop control circuit <NUM>; the process value of the control circuit is representative of the current through the series resistance. Accordingly, by adding a proportion of the current signal to the set point achieves the desired voltage compensation. Operating with this circuit <NUM> results in a near flat load curve, as illustrated in <FIG> of the drawings, up to the current limit. This ensures that the ionisation efficiency no longer reduces with increasing current, provided that the electrical generator <NUM> has not reached the voltage saturation point.

Referring to <FIG> of the drawings, there is illustrated a surgical system <NUM> according to an embodiment of the present invention, for use in performing a surgical procedure on a patient. The system <NUM> comprises the surgical assembly <NUM> as described above (and shown in <FIG>), and a surgical generator <NUM> for generating a surgical signal along the tool <NUM> to the tool-piece <NUM>, for use in performing the surgical procedure. In an embodiment in which the tool-piece <NUM> comprises an electrical conductor, the surgical generator <NUM> may comprise an electrosurgical generator for generating an electrical current surgical signal along the wire <NUM> within the shaft <NUM>. However, in an alternative embodiment, it is envisaged that the shaft <NUM> may comprise a waveguide (not shown) for communicating an ultrasonic or lasing surgical signal from a respective ultrasonic or laser surgical generator, for performing the required surgical procedure.

The assembly <NUM> and system <NUM> further comprise a controller <NUM> for controlling the application of the electrical current along the electrical pathway <NUM> of the electrode <NUM> from the electrical generator <NUM> to the collar/ring/wire <NUM>/<NUM>/<NUM>. The controller <NUM> comprises a switching arrangement <NUM> for enabling and disabling the application of the electrical current to the electrode <NUM> in dependence of an activation status of the surgical signal. The activation status is determined by a sensing arrangement <NUM> of the assembly <NUM>, which may be arranged to directly sense the operation of actuators <NUM> for actuating the surgical signal, or alternatively directly sense the surgical signal from the surgical generator <NUM>, such as via a current sensor <NUM>. The sensing arrangement <NUM> is arranged to output a sensing signal to the controller <NUM> in dependence of the activation status, so that the controller <NUM> can determine whether to enable/disable the electrical current to the electrode <NUM>.

During use, the electrode <NUM> is electrically coupled with an electrical pole <NUM> of the electrical generator <NUM> with a cable <NUM>, via the switching arrangement <NUM>. The cable is terminated at a connector (not shown) for connecting with the connector <NUM> on the handle <NUM> of the tool <NUM>. The patient is electrically coupled to the further electrical pole <NUM> of the electrical generator <NUM> via a contact pad <NUM> which is applied to the patient's leg (not shown) for example, and a further connecting cable <NUM>. The tool <NUM> is then electrically coupled with the surgical generator <NUM> for performing the surgical procedure, via a further connecting cable <NUM> and connector <NUM> disposed on the handle <NUM>. When the surgeon activates the surgical signal, which maybe via a button <NUM> on the tool handle <NUM>, a pedal on a footswitch (not shown) for example, or a button <NUM> on the surgical generator <NUM> itself, the sensing arrangement <NUM> is arranged to output a sensing signal to the controller <NUM> to cause the controller <NUM> to simultaneously enable the electrical current to flow to the electrode <NUM> by closing the switching arrangement <NUM>. The electrical supply to the electrode <NUM> thus establishes an electric field between the exposed portions of the collar <NUM>, or conductive elements <NUM>, or wire <NUM>, and the patient, thereby attracting ionised particulates held in suspension proximate the surgical site toward the patient for example, to clear the surgeons view. It is evident therefore that the controller <NUM> enables the electrode <NUM> to facilitate particulate clearing at the time the surgical signal is commenced.

When the sensing arrangement <NUM> senses that the actuators <NUM> of the surgical generator <NUM> have been manipulated to remove the surgical signal, or when the sensing arrangement <NUM> senses that the surgical signal has been removed from the tool <NUM>, namely disabled, then the sensing arrangement <NUM> is arranged to output a sensing signal to the controller <NUM> which causes the controller <NUM> to open the switching arrangement <NUM> thereby inhibiting further electrical current from flowing to the electrode <NUM> and thus removing the electrical field.

However, in an alternative embodiment, the controller <NUM> further comprises a timer <NUM> which enables the controller <NUM> to delay the disablement of the electrical signal to the electrode <NUM> for a predetermined time, such as <NUM>-<NUM> seconds, after the surgical signal has been removed. This enables the electrode <NUM> to maintain the electrical field to the patient even after the surgeon has finished with an aspect of the surgical procedure for example, so that smoke and particulate clearing can continue even after the aspect of the procedure has been completed.

In an embodiment, the assembly <NUM> further comprises a monitoring circuit <NUM> for monitoring the build-up of conductive material on the shaft <NUM> of the tool, between the electrode <NUM> and tool-piece <NUM>. A schematic illustration of the monitoring circuit <NUM> is illustrated in <FIG> of the drawings and includes a series electrical pathway <NUM> comprising the tool-piece <NUM>, conductor <NUM>, electrical generator <NUM> and electrode <NUM>. The pathway <NUM> is interrupted by the separation of the tool-piece <NUM> from the electrode <NUM>, and a switch <NUM> which, in the embodiment illustrated in <FIG>, remains open (namely switched to the surgical generator <NUM>) during the application of the surgical signal to the tool-piece <NUM>. However, following the removal of the surgical signal from the tool-piece <NUM>, the switch <NUM> is arranged to close via an instruction from the controller <NUM>, thereby establishing an electrical pathway between the tool-piece <NUM> and electrode <NUM> which is interrupted only by the physical separation of the tool-piece <NUM> from the electrode <NUM>. Any conductive material disposed on the shaft <NUM>, between the tool-piece <NUM> and electrode <NUM> will thus facilitate electrical current (generated from the electrical generator <NUM>) to pass directly therebetween. The current flowing in the monitoring circuit <NUM> is thus indicative of the build-up of conductive material. For tools <NUM> completely devoid of conductive material on the shaft <NUM>, then the physical separation of the tool-piece <NUM> and electrode <NUM> will prevent any electrical current flowing in the monitoring circuit <NUM>. Conversely, in situations where the shaft <NUM> is heavily contaminated with conductive material, then electrical current will flow easily between the tool-piece <NUM> and electrode <NUM>. Accordingly, by monitoring the electrical current flowing in the pathway <NUM> as by using an ammeter <NUM> disposed in series within the pathway <NUM>, then the build-up of conductive material can be monitored and the shaft <NUM> cleaned (such as via the sheath (not shown) or heating coil <NUM> discussed above) before the voltage difference between the patient and the electrode <NUM> falls to unuseable levels. In situations where the shaft <NUM> is cleaned via the heating coil <NUM>, then it is envisaged that the heating coil <NUM> may be disposed in a series configuration with the pathway <NUM> of the monitoring circuit <NUM> such that the heating generated will be dependent on the level of material disposed on the shaft <NUM>.

The monitoring circuit <NUM> discussed above is enabled only following the removal of the surgical signal from the tool-piece <NUM>. However, in an alternative embodiment, as illustrated in <FIG> of the drawings, the monitoring circuit <NUM> may comprise an electrically conductive guard collar or ring <NUM> disposed at the distal end of the shaft <NUM>, on an exterior thereof, and the level of conductive material build-up on the shaft <NUM> is determined by monitoring the electrical current flowing between the electrode <NUM> and the ring <NUM>, through the material via ammeter A1 530a, rather than between the electrode <NUM> and tool-piece <NUM> so that the build-up of material on the shaft <NUM> can be monitored. The monitoring circuit of this alternative embodiment further comprises a separate ammeter A2 530b so that the current flowing through the patient from the electrode <NUM> can be simultaneously monitored during the application of the surgical signal to the tool-piece <NUM>, namely during use.

The monitoring circuit <NUM> illustrated in figured 6a and 6b is also arranged to monitor the total electrical current passing through the patient due to the electrical signal from the electrode <NUM>. Upon referring to <FIG>, during use of the tool-piece <NUM> and electrode <NUM>, electrical current will pass through the patient, from electrode <NUM>, and return to the respective generator <NUM> via the patient pad <NUM>. The electrical current can thus be monitored during a surgical procedure and thus the current supply to the electrode <NUM> can be maximised to provide optimal ionisation, without exceeding the safe patient current limit.

The assembly <NUM> further comprises an override actuator <NUM> which may be disposed on the electrical generator <NUM>, controller <NUM> (as illustrated in <FIG> and <FIG> of the drawings), surgical tool <NUM> or a foot switch (not shown) for example, for enabling the surgeon to activate the electrical current to the electrode <NUM> for clearing particulate matter independently of the sensing signal. The override facility allows a surgeon to consciously position the tool <NUM> for smoke clearing for example, and further enable the surgeon to operate the switching arrangement <NUM> of the controller <NUM>, for a bespoke period of time, to suitably clear particulate matter suspended near the surgical site.

Irrespective of whether the surgeon activates the surgical generator <NUM> (and thus initiates a call for the electrical signal to the electrode <NUM>) or actuates the override actuator <NUM> to enable the electrical signal to the electrode <NUM>, the application of the electrical (smoke clearing) signal to the electrode <NUM> is fundamentally controlled by the closed loop control circuit <NUM> which monitors the proximity of the electrode <NUM> to patient tissue. The control circuit <NUM> comprises a voltage monitoring device (not shown) for monitoring the voltage at the distal end of the electrode <NUM>. In the event that the electrode <NUM> is sited too close to the abdominal wall (not shown), within the abdominal cavity of the patient for example, then the voltage will fall below a threshold value, owing to the reduced impedance between the electrode <NUM> and the patient tissue. This reduced voltage will be too low to create a suitable potential difference therebetween for ionising surgical particles and smoke. Moreover, in the event that the electrode <NUM> is too close to the patient tissue, then this could result in a direct electrical short through the patient upon applying the electrical signal. Accordingly, the control circuit <NUM> is configured to prevent/terminate the application of the electrical signal to the electrode <NUM> in the event that the collar/element/wire <NUM>,<NUM>, <NUM> of the electrode <NUM> is positioned or becomes positioned too close to the patient tissue, irrespective of any demand or call for the electrical signal.

Referring to <FIG> of the drawings, there is provided a schematic illustration of a circuit diagram <NUM> of the surgical system <NUM> according to an embodiment of the present invention, but with the sensing arrangement <NUM> removed. The system <NUM> is arranged to receive ac mains electrical power via input terminals <NUM> and this ac mains is converted into dc using a rectification circuit (not shown) associated with the electrical generator <NUM>. The high voltage output from the electrical generator <NUM> is provided to the hand-piece <NUM> via line 142a within cable <NUM>. Line 142a comprises a relay R1, and the application of the electrical signal to the electrode <NUM> is dependent on the switched state of this relay R1.

The surgical generator <NUM> is similarly arranged to receive ac mains electrical power via input terminals <NUM> and generate a first, namely surgical signal which is output via an interface <NUM>. The surgical signal is communicated to the hand-piece <NUM> and thus the tool-piece <NUM> via a cable <NUM> and connector <NUM>. Cable <NUM> comprises a line 411a with a relay R2 disposed therein and a cable 411b with a relay R3 disposed therein. Cable <NUM> comprises a length which is minimized to reduce capacitance between the patient circuit and the environment, and also reduce capacitance between the poles of the surgical generator output. This tends to reduce RF leakage currents (and thus lower the risk of burns to the operator or patient) and reduce the risk of low frequency (mains) leakage current, which is an electrocution hazard, to the patient. On some systems, the RF displacement/capacitive currents which are increased by lengthening treatment cables are significant compared to surgical effect currents (surgical plasmas are often high impedances) and this results in an attenuation of the intended treatment waveform.

The system <NUM> circuit further comprises a first and second electrical pathway <NUM>, <NUM> coupled either side of relay R2 and which extend to a return or ground pathway <NUM>. The pathway <NUM> extends to a terminal <NUM> on the housing 150a of the controller <NUM>. The second pole <NUM> or return of the electrical generator <NUM> is electrically coupled to this pathway <NUM> via cable <NUM>'. The cable <NUM>' comprises a connector <NUM> disposed at a distal end thereof for electrically coupling with terminal <NUM>. The first pathway <NUM> is electrically coupled at the high voltage side of relay R2 and comprises a series connected bleed resistor <NUM> (having a resistance value in the range of 1MΩ - 300MΩ, and preferably 50MΩ - 200MΩ) disposed therein. The bleed resistor <NUM> acts to encourage the dissipation or discharge of residual charge arising from the application of the first signal. The resistance of the bleed resistor <NUM> is selected to suitably attenuate the residual portion of the surgical signal appearing across the output of the surgical generator <NUM> as the first signal is preferably limited to 10µA. The bleed resistor <NUM> is a trivial addition to the loading presented to the second signal and as such, does not substantially affect the second signal. The second pathway <NUM> is electrically coupled at the low voltage side of the relay R2 and comprises a series connected relay R6 and a discharge resistor <NUM>.

The circuit further comprises a relay R5 disposed in the tool handle <NUM> which is manually activated by the surgeon, such as via button <NUM>. The relay R5 is disposed in an electrical pathway 142b which extends within cable <NUM> to the controller <NUM> for communicating the surgeon demands. The pathway 142b further comprises an electrical isolation element, such as a capacitor <NUM> for preventing DC current flowing to the controller <NUM>.

The operational status of the tool-piece <NUM> and electrode <NUM> is provided as a visual output to the surgeon via the front panel indicator display <NUM>. This display <NUM> is arranged to receive signals from the controller <NUM> via pathway <NUM> which also includes a protective capacitor <NUM> which prevents DC currents passing to the display <NUM>.

Upon referring to <FIG>, the circuit further comprises a separate electrical pathway <NUM> which is electrically coupled to line 142a, and which extends to a port <NUM> disposed on the housing 150a. Pathway <NUM> further comprises a series connected relay R4 which can be operated by the controller <NUM> to communicate the first signal to the port <NUM> in the event that a further electrode (not shown) is required to be electrically coupled to the electrical generator <NUM>, for smoke clearing.

During an initialization process, relays R1 and R2 of the switching arrangement <NUM> are closed, with all other relays (R3-R6) of the switching arrangement <NUM> being open, so that any residual charge at the output of the surgical generator <NUM> is permitted to quickly discharge or dissipate across discharge resistor <NUM> for a period of <NUM>-<NUM>. Following this initialization, relay R1 is opened. In this state, the system is in a standby condition with only R2 closed, ready for a demand from the surgeon.

When the surgeon demands the application of the surgical signal to the tool-piece <NUM> by actuating the button <NUM>, relay R5 is closed, thereby instructing the controller <NUM> to close relay R3. While the button <NUM> is pressed, the surgical signal will be communicated to the tool-piece <NUM> and the sensing arrangement (not shown in <FIG>) is configured to sense the activation of the surgical signal and close relay R1 to apply the electrical signal to the electrode <NUM> for smoke clearing. The application of the electrical signal to the electrode <NUM> causes electrons to emanate therefrom, and the electrons attach to the suspended particles thereby ionizing the particles. The electric field generated between the electrode <NUM> and the patient owing to the DC signal, subsequently causes the ionized particles to become attracted to the patient and thus away from the surgical site to improve the surgeons view thereof.

When the surgeon releases button <NUM>, relay R5 is opened. The sensing arrangement <NUM> detects this release and communicates this button release to the controller <NUM>, which results in relays R2 and R3 opening, thereby stopping the surgical signal from passing to the tool-piece <NUM>. Following a time delay of approximately <NUM>-10seconds, relay R1 is subsequently opened by the controller <NUM> to remove the electrical signal from the electrode <NUM>. However, if the surgeon requires extended smoke clearing for example, the then surgeon may press the override actuator <NUM> to cause the electrical signal to continue to pass to the electrode <NUM>. Moreover, when the surgeon releases button <NUM> to remove the surgical signal from the tool-piece <NUM>, then the controller <NUM> may cause relay R6 to close so that any residual capacitative charge developed at the tool-piece <NUM> can discharge through resistor <NUM>.

However, the application of the electrical signal to the electrode <NUM> is contingent on the electrode <NUM> being positioned out of contact with the patient tissue, and sited a minimum distance from patient tissue, as determined by the closed loop control circuit <NUM>. The control circuit <NUM> is configured to disable/prevent the application of the electrical signal to the electrode <NUM> regardless of any demand or call for the electrical signal, in the event that the electrode <NUM> is sited too close to patient tissue.

Referring to <FIG> of the drawings, there is illustrated an electrode assembly <NUM> according to an embodiment of the present invention for use with surgical tools <NUM> in reducing particulate matter, such as surgical smoke, generated during surgical procedures proximate a surgical site. The electrode assembly <NUM> may be used with the surgical assembly <NUM> and system <NUM> described above comprises an electrode comprising a plurality of electrically conductive elements 126a-d, each separately electrically couplable with an electrical generator <NUM> via a respective electrical pathway 128a-d, and configured to receive an electrical signal, namely an electrical current, from the generator <NUM>.

The elements 126a-d are configured to a circular array via a carrier <NUM> which maintains an angular separation between the elements 126a-d, around the surgical tool <NUM>. However, the skilled reader will recognize that the elements <NUM> may be configured to a differently shaped array, depending on the cross-sectional shape of the tool shaft <NUM>. The elements <NUM> may comprise elongate electrical strips or wires for example which may be orientated in a substantially parallel configuration and parallel with a longitudinal axis of the tool <NUM>. Each element <NUM> is arranged to receive an electrical current via a respective switch 710a-d disposed in the respective pathway 128a-d. The switches 710a-d form part of a switching arrangement <NUM> of the controller <NUM>, and the controller <NUM> is arranged to operate each switch 710a-d of the arrangement <NUM> in dependence of a current sensing signal from an electrical current sensing arrangement <NUM>.

The current sensing arrangement <NUM> comprises a plurality of electrical current sensors 720a-d each arranged to separately sense the electrical current flowing in a respective pathway 128a-d. In the event that a particular sensor 720a-d senses that the electrical current flowing in a particular pathway 128a-d exceeds a pre-defined threshold value, the sensing arrangement <NUM> outputs a signal to the controller <NUM> causing the controller <NUM> to open the switch 710a-d in the respective pathway 128a-d to electrically isolate the element 126a-d. In this respect, in situations where the one or more conductive elements 126a-d pass too close to the patient tissue, or otherwise contact the patient, the controller <NUM> is arranged to remove the electrical current flowing to the respective elements 126a-d to prevent any discharge of electrical current directly from the conductive elements 126a-d through the patient. This ability to effectively "switch-off" selected elements 126a and 126b (for example) enables the remainder of the elements 126c and 126d (for example) to continue to function as normal, and thus avoids the need for a complete shut-down of the electrode <NUM>.

Claim 1:
A surgical assembly (<NUM>) for use in performing a surgical procedure on a patient, the assembly comprising:
a surgical tool (<NUM>) comprising a tool-piece (<NUM>) disposed at a distal end thereof, the tool-piece being arranged to receive a first signal for use in cutting or cauterizing tissue of the patient during the surgical procedure;
an electrode (<NUM>) disposed upon the tool;
a DC electrical generator (<NUM>) communicatively couplable with the electrode, for generating a second signal for use in generating an electrical field from the electrode proximate a site of the surgical procedure, for removing particles suspended proximate the surgical site wherein the DC generator comprises an analogue closed loop control circuit (<NUM>) with a voltage monitoring device;
a controller (<NUM>) for controlling the application of the second signal to the electrode, the assembly further comprising a sensing arrangement (<NUM>) for sensing an activation status of the first signal, the sensing arrangement being communicatively coupled with the controller and arranged to output a sensing signal to the controller in dependence of the activation status of the first signal,
wherein the controller is arranged to enable the application of the second signal to the electrode upon receiving a sensing signal representative of an activation of the first signal and prevent/terminate the application of the second signal to the electrode in the event that the electrode is positioned or becomes positioned too close to patient tissue based on the monitored voltage at the distal end of the electrode.