MEDICAL APPARATUS

Abstract: Medical apparatus for cauterisation functions with capacitive coupling (19) from a patient (18) back to an electrical power source (11). Energy from the power source is delivered at a frequency in the Kilohertz region and of amplitude less than 5KV to the patient (18) along a conductor (12). Substantially insert gas is delivered to the end of the conductor (12) where a nozzle (13A) is formed from which and ionised plasma emerges for incidence on the patient (18). The gas may include up to 25 % oxygen. The end piece may take the form of a hand tool and be made of material of low permittivity.

Description: MEDICAL APPARATUS This invention relates to apparatus for use in medicine, particularly for cauterisation. Apparatus for use in medicine, particularly for cauterisation, is already known. For example diathermic apparatus uses electrical energy in the 1-10 MHz range at power levels of about 400 watts and has proved successful in certain circumstances. Laser systems have also been used for cauterisation but these require on-going maintenance and are comparatively powerful. It is an object of the present invention to provide a new and improved form of apparatus for use in medicine, particularly for cauterisation, that is simple to operate and maintain and which utilises very low power levels. According to the present invention there is provided apparatus for use in medicine, particularly for cauterisation, comprising: an electrical power source providing an alternating voltage at a frequency in the Kilohertz region and with a magnitude below 5KV, a single insulated electrical conductor leading from the output of the power source and terminating with an insulation-free tip, conduit means surrounding the electrical conductor along its length and defining a gas-flow channel exteriorly of the electrical conductor, means for delivering a supply of substantially inert gas to the channel, an end piece terminating the gas-flow channel and surrounding the insulation-free tip of the conductor, and wherein the end-piece at its free end defines a nozzle through which the gas-flow can emerge from the channel as a plasma ionised by the alternating voltage supplied to said tip. Preferably the power source operates at a frequency in the range 30-100 KHz and at a voltage in the range 1-3 KV with a power level less than 100 watts. The voltage may have a sinusoidal, square, or triangular waveform. Preferably also, the gas is a gas with a low breakdown potential such as He, Ar, Ne, H 2 or N 2 or a combination thereof. The gas may additionally include a small amount (e.g. less than 25%) of 0 2 . In operation the apparatus provides a corona type flame issuing from the nozzle (high electron temperature but low molecular temperature typically about 20°C) until such time as the flame is brought close to a surface that is connected to electrical earth directly or by stray capacitance, at which point the corona type flame changes to an arc discharge flame (which has a high molecular temperature typically of the order of 800°C) . The flame takes place in the atmosphere provided by the flowing gas which being substantially inert minimises oxidation occurring at the earthed surface. The power delivered to the surface can be controlled to be only a few watts. Accordingly, when the surface is part of a human or animal body the plasma can be used to stop flow of blood from damaged tissue by cauterisation or it can be used to remove layers of tissue by the heat from the arc discharge flame. Because the apparatus functions with capacitive coupling from the surface back to the power source the conduit means can be kept very slender so that it may be used in an endoscope (e.g. it may be associated with a cutting instrument for use in keyhole surgery) . In this connection it will be understood that the conduit means should be made of a non-electrically conducting material and if the end piece takes the form of a hand tool to be hand manipulated by a surgeon it requires to be made of a material of low permittivity so that any capacitance introduced to the apparatus via the surgeon is very low in comparison with that introduced by the patient so that the latter rather than the former provides the electrical return path for the plasma. An embodiment of the present invention will now be described by way of example with reference to the accompanying drawing; in which Fig. 1 schematically illustrates apparatus according to the present invention; and Figs. 2A and 2B illustrate alternative forms of a detail in Fig. 1. The apparatus 10 shown in Fig. 1 comprises an electrical power source 11 which is capable of providing at its output 11A an alternating voltage at a frequency in the Kilohertz region and with a magnitude below 5KV with respect to earth to which terminal 11B is connected. The output voltage is taken by a single insulated electrical wire 12 to a tubular end piece 13 where the wire 12 terminates with an insulation- free tip 12A. Additionally a supply of substantially inert gas is delivered to the end piece 13 via a conduit 14 surrounding the wire 12 and defining a gas flow channel 14A. At its end remote from the end piece 13 the conduit is bifurcated so as to lead to both the electrical terminal 11A and the outlet 15A of a gas supply 15. By this arrangement the electrical wire 12 is surrounded by the inert gas substantially throughout its length and additionally the electrical wire 12 is electrically insulated substantially through its length. The end piece 13 is provided with a tubular outlet nozzle 13A which enables the gas to issue from the end piece 13 and when the electrical wire 12 is energised the issue is to the form of a self-ignited ionised plasma flame 16. The plasma flame 16 is of the corona type, i.e. of low molecular temperature, when it discharges into the normal atmosphere but when the flame 16 is brought close (say about 5 mm) to a surface 18 which is directly connected to electrical earth or is indirectly connected to electrical earth through stray capacitance as illustrated at 19 then the flame 16 switches to being of the arc discharge type (i.e. with high molecular temperature) . In order to regulate and control the apparatus 10 a controller 20 is provided the outputs of which control supplies 11,15 as will be explained. Controller 20 itself is influenced by a manually-operated actuator 21 which can be situated locally to controller 20 but more probably is situated locally to the end piece 13. In particular actuator 21 may take the form of an optical fibre switch arrangement as shown in either of Figs. 2A and 2B. In both cases interrogation light from the controller 20 is delivered to the switch unit 21 via one or more optical fibres 22 extending along the outer surface of the conduit 14 in any geometric configuration (helically wound in Fig. 1 in the interests of clarity) . The interrogation light returned to the controller 20 is proportional to the force F applied to the switch and is quantified and the controller 20 provides its outputs accordingly. In Fig. 2A the switch 21 is formed by a break in a length of optical fibre 24 with one portion of the fibre 24 being mounted on a resilient pad 25 so as to be manually movable into and out of alignment with the other portion of the fibre 24. In Fig. 2B the switch 21 is formed by a prism 26 mounted resiliently on pad 28 adjacent the ends of two fibres 27 and manually movable so as to bring the two fibres 27 into and out of optical continuity. Both switch arrangements described provide a gradual or incremental response so that controller 20 can gradually or incrementally vary the supplies 11,15. Many different control regimes are possible but it is preferred that at initial switch on the gas supply 15 is given a high flow rate for a short period of time in order to purge the gas flow channel 14A of air and thereafter the gas supply 15 delivers at a constant flow rate of 2-6 litres/minute. Also, the electrical supply 11 is pulse width modulated according to the position of the switch 21 to deliver blocks of sinusoidal waveforms of constant frequency and constant amplitude such that the power delivered lies in the range 0 to 100 watts. In consequence delicate cauterisation procedures can be carried out.

Claims: CLAIMS 1. Apparatus for use in medicine, particularly for cauterisation, comprising: an electrical power source (11) providing an alternating voltage at a frequency in the Kilohertz region and with a magnitude below 5KV, a single insulated electrical conductor (12) leading from the output of the power source (11) and terminating with an insulation-free tip (12A) , conduit means (14) surrounding the electrical conductor (12) along its length and defining a gas-flow channel (14A) exteriorly of the electrical conductor (12) , means (15,15A) for delivering a supply of substantially inert gas to the channel (14A) , an end piece (13) terminating the gas-flow channel (14A) and surrounding the insulation-free tip (12A) of the conductor (12) , and wherein the end-piece (13) at its free end defines a nozzle (13A) through which the gas-flow can emerge from the channel (14A) as a plasma ionised by the alternating voltage supplied to said tip. 2. Apparatus as claimed in Claim 1, wherein the power source (11) operates at a frequency in the range 30-100 KHz and at a voltage in the range 1-3 KV with a power level less than 100 watts. 3. Apparatus as claimed in either preceding claim, wherein the gas is a gas with a low breakdown potential such as He, Ar, Ne, H 2 or N 2 or a combination thereof. . Apparatus as claimed in Claim 3 , wherein the gas additionally includes less than 25% of oxygen. 5. Apparatus as claimed in any preceding claim, wherein the end piece (13) takes the form of a hand tool to be hand manipulated by a user and is made of a material of low permittivity. 6. Apparatus as claimed in Claim 1 and substantially as hereinbefore described with reference to the accompanying drawing.

Inventors: CAMPBELL LESLIE, HOWIESON MAURICE MAXWELL, TEKLETSADIK KASEGN, CAMPBELL, LESLIE, HOWIESON, MAURICE, MAXWELL, TEKLETSADIK, KASEGN
Applicants: CAMPBELL LESLIE, HOWIESON MAURICE MAXWELL, TEKLETSADIK KASEGN, UNIV STRATHCLYDE, CAMPBELL, LESLIE, HOWIESON, MAURICE, MAXWELL, TEKLETSADIK, KASEGN, UNIVERSITY OF STRATHCLYDE
Application year: 1995
Main classification: A61B17
IPC codes: A61B17, A61B18