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 surgeon's experience and skill.

<CIT> discloses an electrosurgical system including a generator for generating RF power, an electrosurgical instrument including at least first and second bipolar electrodes carried on the instrument, and a monopolar patient return electrode separate from the instrument. The generator comprises a source of RF power, and has a first supply state in which the RF waveform is supplied between the first and second bipolar electrodes of the electrosurgical instrument, and a second supply state in which the RF waveform is supplied between at least one of the first and second bipolar electrodes and the monopolar patient return electrode. A controller is operable to control the generator such that, in at least one mode of the generator, a feeding means is adapted to alternate between the first and second supply states to supply an alternating signal.

<CIT> discloses a multifunctional medical device that is capable of performing surgical procedure and removing smoke particulates generated during the procedure. The device comprises a plurality of electrodes, two of which are configured to be in electrical communication with opposite poles of a source of high voltage DC electricity to ionize and remove or reduce smoke particles, and at least one of which is also configured to be part of a RF circuit to perform a surgical procedure or operation such as tissue cutting.

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

In accordance with the present invention there is provided a surgical assembly comprising a switching assembly which is arranged to receive a DC signal for use in generating an electrical field proximate a site of a surgical procedure for ionizing and removing particles suspended proximate the surgical site, and a second signal for use in cutting, sealing or cauterizing tissue of the patient during the surgical procedure, the assembly further comprising a surgical tool comprising a tool-piece, the switching assembly being arranged to switch the application of the DC signal and second signal to the tool-piece, and a controller for controlling the application of the DC signal to the tool-piece during a first time interval, the DC and second signals being separated by a third interval during which the DC and second signals are removed from the tool-piece and the application of the second signal to the tool-piece for a second time interval, wherein the controller comprises a timing arrangement configured to time the application of the DC signal to the tool-piece following the second interval, such that the first and second intervals are non-overlapping intervals characterised in that the timing arrangement is arranged to time the application of the DC signal in dependence of a cessation of the second signal, and wherein any residual capacitive charge accumulated during the preceding first interval is allowed to discharge or dissipate during the third interval, the assembly comprising at least one resistor for enabling the discharge or dissipation of residual charge.

In an embodiment, the assembly further comprises a first generator for generating the DC signal, the tool-piece being communicatively couplable with the first generator. The assembly further comprises a sensing arrangement for sensing the second signal from the second generator, as it passes through the controller, the sensing arrangement being arranged to output a sensing signal to the controller in dependence of the sensed second signal. It is envisaged that this sensing arrangement will be particularly useful for situations where the second signal comprises an ultrasonic or laser signal, for example. The first interval corresponds to an interval during which the second signal is below a second threshold value and the second interval corresponds to an interval during which the DC signal is below a first threshold value. The first and second threshold values preferably correspond to DC and second signal values below which the DC and second signals are unable to provide their surgical function of particulate clearing, and cutting, sealing or cauterizing, respectively.

In an embodiment, the controller comprises at least one actuator which is arranged to control the application of the DC and second signals to the tool-piece. The actuator may comprise a hand switch disposed upon the surgical tool. Alternatively, the actuator may comprise a foot-actuated actuator. In a further alternative, the actuator may be disposed remotely from the surgical site, such as in a robotic procedure, for example.

In an embodiment, the controller comprises an override actuator for activating the DC signal. At any time during the first time interval, or following the first interval, namely during a time when the DC signal is not applied to the tool-piece, but before the second interval commences, namely before the second signal is applied to the tool-piece, then upon actuating the override actuator, the controller is arranged to further apply the DC signal to the tool-piece while the override actuator is activated. It is envisaged that this facility will be useful for surgeons who wish to clear large accumulations of suspended particles, including surgical smoke.

In an embodiment, the timing arrangement is arranged to delay the switching of the DC and second signals to the tool-piece, following an instruction from the controller, to allow any residual capacitance voltages and inductance currents within the DC and second signal generators to dissipate or fall below the respective threshold values.

In an embodiment, the first generator comprises a first electrical generator and a first electrical pole of the first generator is electrically couplable with the tool-piece and a second electrical pole of the first generator is electrically couplable with the patient. The second electrical pole may be electrically couplable with the patient via an adhesive pad and electrically conducting gel. The first and second generator may share the same second electrical pole.

In an embodiment, the first electrical generator is configured to generate a direct current signal, to establish a directional electrical field between the tool-piece and biological tissue of the patient. The assembly may further comprise a second generator for generating the second signal. In an embodiment, the second generator comprises a second electrical generator which is configured to generate radio-frequency alternating current signal.

In an embodiment, the tool-piece comprises at least one ion-generating centre. The ion-generating centre may comprise a pointed distal end of the tool-piece and/or a serrated portion of the tool-piece, for example.

In an embodiment, the tool-piece comprises a linear configuration, a J-shape configuration, an L-shape configuration or may comprise a blade, or a forceps comprising a pair of opposing jaws, for example.

In an embodiment, the tool-piece is detachably couplable with the surgical tool. The tool-piece may comprise a disposable, single-use tool-piece, for example. The tool may also comprise a disposable, single use tool, for example.

In an embodiment, the surgical tool comprises a housing, at least a portion of which serves as a handle. Preferably, the controller is disposed within the housing.

In an embodiment, the DC and second signals are communicated to the tool-piece via a connecting cable, which is arranged to electrically couple with the first generator via a cable connector.

In an embodiment, any residual capacitive charge accumulated during the preceding second interval is allowed to discharge or dissipate during the third interval.

In an embodiment, the assembly further comprises a proximity sensor for sensing a proximity of a distal end of the tool-piece to patient tissue.

In an embodiment, the assembly further comprises a voltage compensation circuit for maintaining a substantially constant voltage difference between a distal end of 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, preferably <NUM>-50µA and more preferably <NUM>-10µA.

In an embodiment, the voltage compensation circuit comprises a resistor arrangement electrically couplable with an output of the first generator and a processor which is arranged to receive as input a target voltage and a signal representative of an electrical current flowing through the resistor arrangement, the processor being arranged to process the signal and increase the voltage output from the first generator by an amount corresponding to a voltage drop across the resistor arrangement.

In an embodiment, the assembly further comprises an analogue closed loop circuit for closed loop control of the current output from the first generator. The analogue closed loop circuit is arranged to limit the current flowing from the first generator to a maximum value of 100µA.

In accordance with a second aspect of the present invention, there is provided a surgical system comprising a surgical assembly of the first aspect, a first generator for generating a DC signal for use in generating an electrical field proximate a site of a surgical procedure for removing particles suspended proximate the surgical site resulting from the surgical procedure, and a second generator for generating a second signal for use in cutting or cauterizing biological tissue of the patient during the surgical procedure,.

Further features of the surgical system or DC voltage compensation circuit or process may comprise one or more of the features of the surgical assembly described above.

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.

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 in a surgical procedure, such as an electrosurgical, ultrasonic or laser based surgical procedure. The assembly <NUM> comprises a first generator <NUM>, such as a high voltage electrical generator capable of generating <NUM>-20kV, preferably <NUM>-10kV. The first generator <NUM> is arranged to generate a first signal which is a direct current (DC) voltage waveform that is used for creating an electric field proximate a site of a surgical procedure. In an embodiment, the assembly <NUM> is arranged to receive via a connector <NUM>, a second signal which is output from a second generator <NUM>. The connector <NUM> may be disposed on a housing <NUM> of the first generator <NUM> and the second signal may be received within the housing <NUM>. The second generator <NUM> may comprise a laser source (not shown) in which case, the second signal may comprise lasing radiation. Alternatively, the second generator <NUM> may comprise an ultrasonic wave generator, in which case the second signal may comprise an ultrasonic signal. In a further alternative, the second generator <NUM> may comprise an electrical generator for generating a radio frequency (RF) alternating current (AC) voltage waveform. In any of the above embodiments, the second signal is arranged to cut, seal and/or cauterize biological tissue of a patient during the surgical procedure.

The assembly <NUM> further comprises a surgical tool <NUM> which is electrically couplable with the first generator <NUM> and second generator <NUM>, via a cable <NUM>. The cable <NUM> comprises a connector <NUM> disposed at a distal end thereof for forming a connection with the first and second generator <NUM>, <NUM>, and as such may comprise an electrical connector, or a combination connector for forming an electrical and optical connection for example, to the respective generators. The cable <NUM> preferably comprises a length of at least <NUM> so that the first and second generators <NUM>, <NUM> can be kept isolated from the sterile environment of a surgical environment. In an embodiment, the connector <NUM> and cable <NUM> are arranged to communicate the first signal and the second signal to the tool <NUM> for use in performing the surgical procedure. However, in an alternative embodiment, it is to be appreciated that the first and second signals may be communicated to the tool <NUM> via separate cables and connectors (not shown). For the purposes of further describing the invention, only the embodiment in which the second generator <NUM> comprises an RF generator will be described.

In use, the tool <NUM> is held by a surgeon (not shown) to perform the procedure and comprises a housing <NUM>, at least a portion of which forms a tool handle for the surgeon. The tool <NUM> further comprises a tool-piece <NUM> which may be detachably couplable with the housing <NUM> via a clamp or chuck arrangement (not shown). The tool-piece <NUM> is arranged to receive the first and second signals and is formed of an electrically conductive material, such as a metal, which extends through an electrically insulating sheath <NUM>, whereas the housing <NUM> which is held by the surgeon is formed of an electrically insulating material, such as a dielectric.

The first signal is arranged to pass along a first circuit path and the second signal is arranged to pass along a second circuit path, and the first and second path is dependent on the electrosurgical mode of operating the tool <NUM>.

For example, in a monopolar operational mode, as illustrated in <FIG> and <FIG> of the drawings, the first signal is arranged to pass from a first electrical pole (not shown) of the first generator <NUM>, through the patient to a second electrical pole of the first generator. The second electrical pole is electrically coupled to a patient (not shown) via a separate cable <NUM>' which, in the arrangement illustrated in <FIG>, is coupled at a proximal end thereof to the second electrical pole (not shown) of the second generator <NUM> and at a distal end thereof to an adhesive pad <NUM> for forming a physical and electrical connection to the patient. The second electrical pole of the first generator <NUM> is electrically coupled to the second electrical pole of the second generator <NUM> (via cable <NUM>' and connector <NUM> - see later description relating to <FIG>) and as such it is evident that the first and second path share a common cable <NUM>' and adhesive pad <NUM>. Accordingly, the first signal is arranged to pass from the first pole of the first electrical generator <NUM>, along cable <NUM> to the tool-piece <NUM>, whereupon electrons propagate from the tool-piece <NUM> toward the patient tissue, such as an abdominal wall of the patient owing to the electrical coupling of the patient to the second (i.e. opposite) electrical pole of the first generator <NUM> via cable <NUM>'. The electrons and thus first signal subsequently passes back to the second pole of the first generator <NUM> via the adhesive pad <NUM> and further cable <NUM>'. In a variation of the monopolar operational mode however, which is not illustrated, the proximal end of the cable <NUM>' may instead by coupled directly to the second pole of the first generator <NUM>. In this case, the first circuit path and second circuit path may comprise a dedicated return cable <NUM>' and a dedicated adhesive pad <NUM> for forming an electrical contact with the patient, within their respective circuits.

The second signal is arranged to pass along a second circuit path which is again dependent on the particular electrosurgical mode of operating the tool <NUM>. For example, in a monopolar configuration, as illustrated in <FIG> and <FIG> of the drawings, the second signal passes between a first and second electrical pole (not shown) of the second generator <NUM>, along a path comprising the cable <NUM>, the tool-piece <NUM> and the cable <NUM>' which is electrically coupled to the patient via the adhesive pad <NUM>.

However, in a bipolar configuration (which is not illustrated), opposing electrical poles of the second generator <NUM> are electrically coupled to electrically isolated portions of the tool-piece <NUM>. For example, in situations where the tool-piece <NUM> comprises a grasp or forceps <NUM> as illustrated in <FIG>, having opposing jaw portions , then the electrical poles of the second generator <NUM> may be separately electrically coupled with each jaw, and as such, there is no requirement for an electrical return via a pad <NUM> disposed on the patient. The second signal is arranged to pass from a first pole of the second generator <NUM>, to one of the jaws 135a of the forceps <NUM> and then return to the second pole of the second generator <NUM> via the opposing jaw 135b of the forceps <NUM>. The RF electrical field generated by the second generator <NUM> will thus become directed within the tissue held between the jaws 135a, 135b for performing the required cutting, sealing or cauterising of tissue. In this bipolar configuration, the cable <NUM>' may be electrically coupled directly with the second pole of the first generator <NUM> and thus form part of the first circuit path only. In this case, the first signal is arranged to pass from the first pole of the first generator <NUM> to one of the jaws 135a, 135b of the forceps <NUM> and then return to the second pole of the first generator <NUM> via cable <NUM>' and pad <NUM>. However, the first signal would only be allowed to pass to one of the jaws 135a, 135b once the second signal has been removed from both jaws 135a, 135b and disconnected from the second generator, to otherwise prevent a first signal discharge between the jaws. Similarly, and as an extension to bipolar configurations, in multi-pole configurations, it would be necessary to remove the second signal from each pole, and disconnect the second generator <NUM> from each pole, before applying the first signal to one of the poles.

The assembly <NUM> further comprises a controller <NUM> for controlling the application of the first and second electrical signals to the tool-piece <NUM>. The controller <NUM> may be disposed within the tool housing <NUM> for example or alternatively within the housing <NUM> of the first generator <NUM>. The controller <NUM> is communicatively coupled with a switching assembly <NUM>, and is arranged to control the switched state of the assembly <NUM> for switching the application of the first and second electrical signals to the tool-piece <NUM>. The switching assembly <NUM> comprises a plurality of relays (R1-R6 - see <FIG> of the drawings) which are opened and closed by a relay driver (not shown) in response to control signals from the controller <NUM> and in order to avoid any interference between the first and second signals, and the control signals, effective electrical shielding is disposed therebetween.

In an embodiment particularly suited to situations where the second signal comprises an ultrasonic or optical radiation signal, the controller comprises a sensing arrangement <NUM> for sensing the second signal. Such a sensing arrangement may be effected in a plurality of forms including but not limited to a medium wave antenna coupled to a diode detector for sensing an envelope of the peak electromagnetic field disturbance caused by the presence of the second signal, a combination of voltage or current transformer coupling a fractional sample of the second signal, or by a status input from a controller (not shown) of the second generator <NUM> indicative of the second signal being above or below an amplitude threshold which is communicated to the sensor arrangement <NUM>. The sensing arrangement <NUM> is arranged to output a sensing signal to the controller <NUM> in dependence of the sensed second signal, to enable the controller <NUM> to control the application of the first electrical signal to the tool-piece <NUM> via the switching assembly <NUM>. The controller <NUM> is arranged to apply the first electrical signal to the tool-piece <NUM> during a first time interval and the second electrical signal to the tool-piece during a second time interval, which is separate and non-overlapping with the first time interval. In this respect, the sensing arrangement <NUM> acts as a safety feature to prevent a simultaneous application of the first and second signal. The first interval corresponds to an interval during which the second signal is below a second threshold value and the second interval corresponds to an interval during which the first signal is below a first threshold value. The first and second threshold values correspond to signal values below which the first and second signals are unable to provide their surgical function of particulate clearing, and cutting, sealing or cauterizing, respectively. However, in embodiments in which the second signal comprises lasing radiation or an ultrasonic signal it is anticipated that the first and second signals may be applied to the tool-piece simultaneously.

In an embodiment, the assembly <NUM> further comprises at least one user controlled actuator <NUM>. The controller <NUM> is arranged to control the application of the first and second signals to the tool-piece in response to the operational state of the actuator <NUM> and as such, the operational state of the actuator <NUM> determines in part, the control signals output by the controller <NUM> to the relay driver.

The actuator <NUM> may comprise a button <NUM>, for enabling a surgeon to initiate an automated switching of the application of the first and second signals to the tool-piece <NUM>. The button <NUM> may be mounted on the tool housing or comprise a foot-actuated button, or in the case of robotic surgery, located remote from the surgical site. It is envisaged that pressing button <NUM> will cause the second signal to pass to the tool-piece <NUM> for performing the surgical procedure, and upon releasing the button <NUM>, the second signal will be removed from the tool piece <NUM>. The release of the button <NUM> subsequently results in the application of the first signal to the tool-piece for smoke clearing.

In a further embodiment, the assembly <NUM> may comprise or further comprises an override actuator <NUM>, such as a button on the housing of the tool-piece <NUM>, for enabling the surgeon to activate the first signal for a desired period of time, once the second signal has been removed from the tool piece. For example, upon releasing button <NUM>, then the second signal will be removed from the tool-piece and the first signal will subsequently be applied for a predetermined time. However, the override actuator <NUM> is arranged to enable the surgeon to continue to apply the first signal to the tool-piece <NUM>. The application of the first signal to the tool-piece <NUM> by the override actuator <NUM> may be designed to continue while the button <NUM> is pressed, and/or to continue for a predetermined time following the release of the actuator <NUM>. It is envisaged that this facility will be useful for surgeons who wish to clear large accumulations of suspended particles, including surgical smoke for example, without necessarily having to maintain operation of the actuator <NUM> throughout the clearing process. Such a time interval may be repeated by the surgeon as necessary by subsequent operation of the actuator <NUM>.

However, to ensure a safe operation of the assembly <NUM>, namely a safe application of the first and second signals, the controller <NUM> further comprises a timing arrangement <NUM> for timing the application of the first signal to the tool-piece <NUM> following a release of button <NUM>. The timing arrangement <NUM> is arranged to receive notification of the removal of the second signal from the tool-piece, and is configured time the application of the first signal for a first time interval, such as <NUM>, after a predefined delay following the removal of the second signal from the tool-piece <NUM>.

In a further embodiment, the assembly <NUM> further comprises at least one sensor (not shown) communicatively coupled with the controller <NUM>, for sensing the presence of surgical particulates, and the at least one sensor is arranged to output a signal to the controller <NUM> representative of the amount of particulates surrounding the surgical site. In this embodiment, the controller <NUM> is arranged to suspend, and if necessary override any demand for the application of the second signal to the tool-piece <NUM> and thus maintain/initiate the application of the first signal to the tool-piece <NUM> for a dwell period/interval until the amount of surgical particulates have been reduced to a predefined threshold.

The timing arrangement <NUM> and controller <NUM> are thus arranged to control the switching assembly <NUM> to delay the application of the first signal to the tool-piece <NUM>, following the application of the second signal, by <NUM>-<NUM>. For example, upon referring to <FIG> of the drawings, there is illustrated a timing sequence for the automated switching of the application of the first signal. Following the application of the second signal for a second time interval, as determined by the surgeon during a tissue cutting procedure for example, the circuit comprising the second generator <NUM> is allowed to discharge during a third time interval of approximately <NUM>-<NUM>, before the first signal is applied for a first time interval of approximately <NUM>, to clear particulates. Similarly, a further delay, namely a further third interval of <NUM>-<NUM> is used to enable the circuit comprising the first generator <NUM> to discharge before the subsequent application of the second signal again. Such a delay in commencement of the first and second interval may avoid premature commutation of the tool-piece <NUM> between the second signal and the first signal where the envelope of the second signal is necessarily of a particularly intermittent nature, by enabling any residual first or second signal charge to discharge/dissipate (see later description relating to <FIG>). It is known for instance that laser treatments intended for cutting, sealing or cauterizing tissue may be applied with significant dwell intervals where the second signal is below an amplitude threshold separated by intervals where the second signal is above the amplitude threshold. Such methods are also found on electrosurgical generators, and are generally employed to reduce collateral damage through thermal diffusion through tissue at the surgical site.

In a further embodiment, the controller <NUM> further comprises a proximity sensor <NUM> for sensing the separation of the distal end of the tool-piece <NUM> from an electrically conducting pathway, such as patient tissue. The proximity sensor comprises a voltage monitoring device (not shown) for monitoring the voltage at the distal end of the tool-piece <NUM>. In the event that the distal end of the tool-piece <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 tool-piece <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 distal end of the tool-piece <NUM> is too close to the patient tissue, then this could result in a direct electrical short through the patient upon applying the first signal. Accordingly, the proximity sensor <NUM> is configured to prevent/terminate the application of the first signal in the event that the distal end of the tool-piece <NUM> is positioned or becomes positioned too close to the patient tissue.

The tool-piece <NUM> may comprise a linear spear-like shape (as illustrated in <FIG> of the drawings) having a pointed distal end <NUM>. The pointed end acts as an ion-generating centre and facilitates the release of electrons therefrom when supporting the second signal, and thus the ionization of particles suspended in the local atmosphere of the surgical site. In alternative embodiments however, as illustrated in <FIG> of the drawings, the tool-piece may comprise a blade configuration, an L or J-shape, and similarly comprise a pointed distal end. In yet a further embodiment as illustrated in <FIG> of the drawings, the tool-piece may comprise or further comprise a plurality of pointed serrations which extend along a portion of the length of the tool-piece for example. In a further embodiment, as illustrated in <FIG> of the drawings, the tool-piece may comprise opposing jaws 135a, 135b of a forceps <NUM>, where one or both of the jaws 135a, 135b comprise sharp edges or serrations <NUM> which act as ion-generating centres and thus similarly facilitate the ionization of particles suspended nearby.

In use, the surgical assembly <NUM> is electrically coupled with the second electrical generator <NUM> via a socket <NUM> on the first electrical generator <NUM> to form a surgical system <NUM>, an embodiment of which is illustrated in <FIG> of the drawings. An adhesive pad <NUM> is subsequently secured to the patient, such as upon a leg of the patient (not shown), and for a monopolar operation, the pad <NUM> is electrically coupled to the second pole of the second generator <NUM> via a cable <NUM>'. However, as noted above, the second pole of the first and second generators may share the return cable <NUM>' in this configuration, and as such, the second pole of the first generator <NUM> is also electrically coupled to the pad <NUM>. To provide an enhanced electrical coupling to the patient, an electrically conductive gel (not shown) may be applied between the pad <NUM> and the patient's leg (not shown).

The surgical tool <NUM> is then electrically coupled with the first generator <NUM> via the cable <NUM> and associated connector <NUM> and a tool-piece <NUM> is secured within the tool <NUM> via the chuck arrangement (not shown) for example. The tool-piece <NUM> forms an electrical coupling with the cable <NUM>, and a distal end of the tool-piece <NUM> is electrically exposed, namely extends out from the sheath <NUM>, for performing the electrosurgical procedure. Once the tool-piece <NUM> has been secured in place, the first and second generators <NUM>, <NUM> are activated via a respective power switch (not shown).

Referring to <FIG> of the drawings, there is provided a schematic illustration of a circuit diagram of the surgical system <NUM> configured for monopolar surgical operation. The system 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 first generator <NUM>. The high voltage output from the first generator <NUM> is provided to the handpiece <NUM> via line 140a within cable <NUM>. Line 140a comprises a relay R1 which forms part of the switching arrangement <NUM>, and the application of the first signal to the tool-piece <NUM> is dependent on the switched state of this relay R1.

Referring to <FIG> of the drawings, the first generator <NUM> comprises an analogue closed loop <NUM> for closed loop control of the output current. The operating current is influenced by the separation of the distal end of the tool-piece <NUM> from the patient tissue. As the tool-piece <NUM> approaches the patient tissue, the impedance falls. This causes the current to increase and the output voltage to fall. The first generator <NUM> however, monitors the current flowing between the tool-piece <NUM> and the patient tissue and terminates the current as it approaches an upper current limit, such as 10µA, which is typically the maximum DC current that can safely be applied to a patient.

The control loop <NUM> primarily controls the output current of the first generator <NUM>. The first generator <NUM> comprises a 200MΩ series resistance <NUM> 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 first generator <NUM> outputs the maximum 10kV. The resistance is embodied as two separate 100MΩ resistors 114a, 114b, each separately connected in series with the high voltage and low voltage output terminals of the first generator <NUM>. Electrical current is returned to the first generator <NUM> via a resistor 114b, 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 first generator <NUM>. If the process value is above/below the current set point, the control signal to the first 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 first 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 <NUM> of the first 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 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 first generator <NUM>. This is achieved by increasing the voltage set point by the voltage drop through the series resistance 114b. The circuit <NUM> comprises a processor or summation device <NUM> which is arranged to receive as input the desired or target voltage and a signal representative of an electrical current flowing through the resistor 114b. This current is already known by the closed loop control circuit <NUM>; the process value of the control circuit <NUM> is representative of the current through the series resistance <NUM>. Accordingly, by adding a proportion of the current signal to the set point achieves the desired voltage compensation. Operating the system <NUM> with this circuit <NUM> results in a near flat load curve where the voltage remains within <NUM>% of the desired 10kV voltage (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 first generator <NUM> has not reached the voltage saturation point.

Referring again to <FIG> of the drawings, the second generator <NUM> is similarly arranged to receive ac mains electrical power via input terminals <NUM> and generate a second signal which is output via an interface <NUM>. The second signal is communicated to the handpiece <NUM> and thus the tool-piece <NUM> via a cable <NUM> and connector <NUM>. Cable <NUM> comprises a line 208a with a relay R2 disposed therein and a cable 208b 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 second 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 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 <NUM>. The second pole or return of the second 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 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 first signal appearing across the output of the second 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 (which also forms part of the switching arrangement <NUM>, although is located within the tool <NUM>) disposed in the tool <NUM> which is manually activated by the surgeon, such as via button <NUM>. The relay R5 is disposed in an electrical pathway 140b which extends within cable <NUM> to the controller <NUM> for communicating the surgeon demands. The pathway 140b further comprises an electrical isolation element, such as a capacitor <NUM> for preventing DC current flowing to the controller <NUM>.

Upon referring to <FIG>, the circuit further comprises a separate electrical pathway <NUM> which is electrically coupled to line 140a, and which extends to a port <NUM> disposed on the housing <NUM>. 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 first generator <NUM>, for smoke clearing.

During an initialization process, relays R1 and R6 of the switching arrangement <NUM> are closed, with all other relays (R2-R5) of the switching arrangement <NUM> being open, so that any residual charge at the output of the first generator <NUM> is permitted to quickly discharge or dissipate across discharge resistor <NUM> for a period of <NUM>-<NUM>. Following this initialization, relays R1 and R6 are opened, and relay R2 is closed to place the second generator <NUM> in a standby condition for performing the surgical procedure. During this standby period, any current leakage preferentially occurs across the bleed resistor <NUM>, thereby minimizing current leakage across the other relays, R1, R3-R6.

When the surgeon demands the application of the second signal to the tool-piece <NUM> by actuating the button <NUM>, relay R5 is closed, thereby instructing the controller <NUM> to close relay R3 (for the second time interval, as determined by the length of time the surgeon presses the button <NUM>). During this second time interval the surgeon can manipulate the tool <NUM> to perform the surgical procedure. Upon releasing button <NUM>, relay R5 is opened, which results in relay R3 opening stopping the second signal from passing to the tool-piece <NUM>. Relay R2 is subsequently opened to disconnect the second generator <NUM> from the tool <NUM>. Following a third time interval, relay R1 is closed by the controller <NUM> to apply the first signal to the tool-piece for smoke clearing (for a first time interval). The application of the first signal to the tool-piece <NUM> causes electrons to emanate from the distal end of the tool-piece <NUM> and any other ion-generating centres, and the electrons attach to the suspended particles thereby ionizing the particles. The electric field generated between the tool-piece <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.

Following the first time interval, the system is configured to re-initialise. During this process, relay R6 is closed together with relay R1, with all other relays being open, so that any residual charge at the output of the first generator <NUM> is permitted to quickly discharge or dissipate across discharge resistor <NUM> for a period of <NUM>-<NUM>.

In the case of a bipolar surgical operation or in situations where the second signal comprises an ultrasonic signal, bleed resistors <NUM> would be placed between the poles of the output of the second generator <NUM> and in a further alternative embodiment, such resistors would be placed between each pole of the second generator output and the patient return pad <NUM> or protective earth potential. In this further embodiment, the further resistors connected to protective earth would have values at least 50MΩ so as to not compromise the floating status of the patient circuit, which comprises the electrical components coupled to the patient.

With any residual charge from the application of the first signal removed, relays R1 and R6 are subsequently opened, and relay R2 is closed to place the second generator <NUM> in a standby condition again, ready for a further demand for the second signal from the surgeon.

Claim 1:
A surgical assembly (<NUM>) comprising a switching assembly (<NUM>) which is arranged to receive a DC signal for use in generating an electrical field proximate a site of a surgical procedure for ionizing and removing particles suspended proximate the surgical site, and a second signal for use in cutting, sealing or cauterizing tissue of the patient during the surgical procedure, the assembly further comprising a surgical tool (<NUM>) comprising a tool-piece (<NUM>), the switching assembly being arranged to switch the application of the DC signal and second signal to the tool-piece, and a controller (<NUM>) for controlling the switching assembly to control the application of the DC signal to the tool-piece during a first time interval, the DC and second signals being separated by a third interval during which the DC and second signals are removed from the tool-piece and the application of the second signal to the tool-piece for a second time interval, wherein the controller comprises a timing arrangement (<NUM>) configured to time the application of the DC signal to the tool-piece following the second interval, such that the first and second intervals are non-overlapping intervals, wherein that the timing arrangement is arranged to time the application of the DC signal in dependence of a cessation of the second signal, and wherein any residual capacitive charge accumulated during the preceding first interval is allowed to discharge or dissipate during the third interval, the assembly comprising at least one resistor (<NUM>, <NUM>) for enabling the discharge or dissipation of residual charge.