Electrosurgical method and apparatus for initiating an electrical discharge in an inert gas flow

A method and apparatus for initiating an electrical discharge in a formation of flowing inert gas disposed adjacent the end of an active electrode by generating charged particles in the vicinity of said inert gas formation. The charged particles are generated by an auxiliary electrical discharge produced between the active electrode and a surrounding tube, which is not connected to any external source of biasing potential. Electrostatic charge is generated on the tube as the inert gas flows thereby. This charge bleeds off the tube through inwardly pointed tips on the tube, which act as discharge points. The charge then passes to the active electrode via the auxiliary discharge through the gas.

RELATED APPLICATIONS 
This application is related to a first U.S. Pat Ser. Application No. 
649,725 filed on Jan. 16, 1976 by Charles F. Morrison, Jr., Frank W. 
Harris, and Michael C. Patzer, entitled "Electrosurgical Method and 
Apparatus for Establishing an Electrical Discharge in an Inert Gas Flow" 
and a second U.S. Ser. Pat. Application No. 649,683 filed on Jan. 16, 1976 
by Charles F. Morrison, Jr. and Benson C. Weaver, entitled 
"Electrosurgical Method and Apparatus for Initiating an Electrical 
Discharge in an Inert Gas Flow", all the foregoing applications being 
assigned to the same assignee. 
BACKGROUND OF THE INVENTION 
This invention relates to the initiation of electrical discharges and in 
particular to the initiation of such discharges in inert gas flows. 
In the first of the above-mentioned related patent applications, there is 
disclosed a method and apparatus for establishing an electrical discharge 
from an electrode by forming a column of inert gas adjacent the electrode 
whereby the discharge is both long and directed. There is also disclosed 
an electrosurgical method and apparatus for coagulating by fulguration 
where a long electrical discharge is established either through a diffuse 
blanket of inert gas or a well defined column of the gas. Since the 
discharge is long, any tendency for the electrode to contact the surface 
being treated is substantially lessened whereby undesirable sticking of 
coagulated tissue to the electrode in electrosurgical applications is 
practically eliminated. However, there is some difficulty in initiating 
this long electrical discharge and thus, it is necessary to touch the 
electrode down on or very near to the tissue being coagulated. This can 
also result in adhesion of tissue to the hot electrode where the tissue 
can be ripped away when the instrument is removed from the site thereby 
causing surgical complications. Further, the adhered tissue tends to foul 
the electrode such that it must be scraped clean before the surgical 
procedure can continue. 
In the second of the above-mentioned related patent applications, there is 
disclosed a method and apparatus for initiating the electrical discharge 
where an auxilliary source of charged particles is employed. In one 
embodiment an auxilliary electrical discharge in electrical series with 
the active electrode generates the charged particles. This arrangement is 
advantageous in that no external means are needed to generate the charged 
particles. However, all power from the gnerator to the patient must pass 
through the auxilliary gap and thus, there is some undesirable power loss. 
SUMMARY OF THE INVENTION 
With this invention, the above difficulties can be eliminated. Further, as 
will be brought out in detail hereinafter, extension of the invention to 
non-surgical applications such as thermal-inert-gas welding is also 
advantageous and desirable. 
A primary object of this invention is the provision of a method and 
apparatus for initiating a long electrical discharge in a formation of 
inert gas with little, if any power loss and without the need for external 
charged particle generating means. 
A further object of this invention is the provision of an electrosurgical 
method and apparatus for coagulating by fulguration where the electrical 
discharge is initiated and established either through a diffuse blanket of 
inert gas or a well defined column of the gas. 
These and other objects of the invention will become apparent from a 
reading of the following specification and claims taken together with the 
drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
Referring to the figures of the drawing where like reference numerals refer 
to like parts and, in particular, referring to FIG. 1, there is shown a 
source 10 of electrical energy which may be continuous or preferably 
discontinuous such as periodic bursts of electrical energy as illustrated 
in FIG. 7 of U.S. Pat. No. 3,699,967 granted to Robert K. Anderson. This 
energy is typically in the high frequency range -- that is, about 200 kHz 
or higher. The waveform has a high crest factor -- that is, typically 
about 5-10 where the crest factor of a periodic function is the ratio of 
its crest (peak, maximum) value to its root-mean-square value. The bursts 
may occur at a repetition rate of 15,000 to 50,000 bursts per second while 
the duration of each burst may consist of 1 to 5 cycles of the high 
frequency energy, it being understood that none of the foregoing values is 
critical. Such waveforms are well known for use as coagulating waveforms 
in electrosurgery. It should be understood that source 10 may also 
generate waveforms of other types such as those used in thermal-inert-gas 
(TIG) welding. 
Source 10 may be connected to an electrosurgical instrument or a welding 
instrument generally indicated at 12. Instrument 12 basically comprises a 
support member 14, which may function as a handle. Member 14 supports an 
active electrode 16, which may be directly supported by member 14 or 
indirectly supported thereby via an intermediate member 18, although 
intermediate member 18 does not necessarily also have to be employed as a 
support member, as will be described in more detail hereinafter. Source 10 
may be electrically connected in a conventional manner to electrode 16 by 
appropriate connections (not shown) internal to members 14 and 18. 
A source 20 of gas is also connected to instrument 12 and, as will be 
described in more detail hereinafter, the gas is employed to support an 
electrical discharge used for tissue coagulation and the like. The gas 
should be inert in the sense that it is not combustible by the electrical 
discharge nor will it support combustion of the electrode 16. It may, for 
example, be selected from the group consisting of nitrogen and the noble 
gases and mixtures thereof. Helium has been found to be particularly 
advantageous as discussed in the first of the beforementioned patent 
applications. 
In FIGS. 2 and 3 there are shown electrode structures generally 
corresponding to that shown in FIG. 1. Intermediate member 18 comprises a 
hollow tube disposed about and surrounding electrode 16 whereby an annular 
passageway is provided through which the gas from source 20 flows. As the 
gas flows out of tube 18 an outwardly extending column of flowing inert 
gas is formed adjacent the tip or end of electrode 16 to thereby 
facilitate the establishment and maintenance of a highly directive 
discharge 24 to a surface 26 such as body tissue or the like, although in 
this application the surface 26 may also be metal or the like as in 
welding operations or the like. The active electrode is electrically 
conductive and typically may be made from tungsten, stainless steel, etc., 
as is the tube 18. The radial distance between the forward end of 
electrode 16 and tube 18 may typically be about 30 mils while the diameter 
of electrode 16 is typically about 12-15 mils, it being understood that 
none of the foregoing values are critical to the desired formation of a 
column of gas. 
The outwardly extending column of inert gas is well defined and produces a 
very long electrical discharge. This discharge is four to six times the 
length of that generated under the same conditions without the gas. The 
discharge is straight down the gas column. The directivity of the 
discharge is such that it can be directed to the bottom of a fissure or 
crevice without deflecting to the sides thereof. 
The directivity and length of the discharge is very disirable; however, 
there is some difficulty in initiating the discharge and thus, it is 
necessary to touch the electrode 16 down or very near to the surface 26. 
This can result in adhesion of tissue to the hot electrode which can cause 
the tissue to be ripped away when the instrument is removed from surface 
26, thereby causing surgical complications. Further, the adhered tissue 
tends to foul the electrode such that it must be scraped clean before the 
surgical procedure can continue. To avoid these problems, discharge 
initiating means generally indicated at 28 are provided. In particular, 
means 28 preferably comprises a tube 18 and a plurality of pointed 
projections or tips 30 which inwardly extend from tube 18. An auxiliary 
electrical discharge is generated between tips 30 and a portion of the 
active electrode 16, the portion being indicated at 32 where portion 32 is 
spaced from the tip or forward end of active electrode 16. The location of 
portion 32 with respect to the tip of electrode 16 is not critical and it 
need only be removed from the tip to the extent necessary to maintain gas 
flow integrity. Typically the distance between tips 30 and portion 32 is 
about 10-20 mils although these values are not critical. As will be 
explained in more detail hereinafter, the auxiliary electrical discharge 
is generated by the inert gas flowing by tube 18. 
It is thought that the charged particles generated in the auxiliary 
electrical discharge are swept by the inert gas through tube 18 to the 
region in front of active electrode 16 whereby an electrical discharge is 
initiated in the inert gas in front of the electrode assuming an 
appropriate electrical potential such as that produced by source 10 is on 
active electrode 16 and assuming active electrode 16 is in the electric 
field of an appropriate return electrode, such as that indicated at 34 in 
FIG. 2. The discharge may also be solely due to the electric field 
associated with the auxiliary discharge or due to both the particles and 
the electric field. In electrosurgical applications the return electrode 
would in effect be the patient's body (surface 26) which is in electrical 
contact with return electrode 34, which preferably has a large area. In 
welding applications, the return electrode would correspond to the 
workpiece (surface 26) to be welded. When active electrode 16 is 
substantially removed from surface 26, but still in the field of the 
return electrode, the electrical discharge initiated by the auxiliary 
electrical discharge is a tiny hair line of corona discharge which extends 
a substantial distance from the active electrode due to the presence of 
the gas. As active electrode 16 is brought closer to surface 26, the 
electrical discharge becomes heavy and luminous. Typically, the discharge 
necessary to effect coagulation by fulguration occurs when the active 
electrode is within about one-half inch of the tissue and hence, no tissue 
will undesirably adhere to the electrode. The foregoing theory of 
operation may not be perfectly correct; in any event, there is no 
intention to be limited thereby. 
The gas flow through tube 18 generates electrostatic charges between active 
electrode 16 and tube 18. When an RF voltage or the like is applied to the 
active electrode, the electrostatic charges bleed off of the tube to the 
electrode through tips 30, which act as discharge points, and thence via 
the auxiliary electrical discharge through the gas. This discharge than 
provides part of the necessary corona starting conditions. Bringing the 
tip into the field of the return electrode provides the remainder. With 
the tiny corona discharge playing on the flesh, the heavy, luminous 
discharge will jump only when the distance to the flesh is less than a 
critical value. Once this discharge has started, it can be drawn to 
greater than the starting length. When drawn too far, the heavier 
discharge extinguishes, leaving the corona. 
From the foregoing it can be appreciated that tube 18 is not connected to 
any source of external biasing potential. As stated above, the 
electrostatic charge needed for the auxiliary discharge is generated on 
the tube by the gas flowing thereby. Hence, this is a very important 
feature of the invention in that the need for additional apparatus to 
generate the auxiliary discharge is eliminated. Another important feature 
of the invention is that little, if any, of the power from electrical 
power source 10 is absorbed in the auxiliary discharge. This is in 
contradistinction to the arrangement disclosed in the aforementioned 
related patent application entitled "Electrosurgical Method and Apparatus 
for Initiating an Electrical Discharge in an Inert Gas Flow" where the 
auxiliary discharge is in electrical series with the active electrode. 
Thus, all power from source 10 to the patient must pass through the 
auxiliary gap. As stated above, this is not necessary in accordance with 
the present invention. 
Reference should now be made to FIG. 3 where there is shown an electrode 
structure embodying the arrangement illustrated in FIG. 2. A brass tube 
35, which may have an outside diameter of about 93 mils is connected to 
the active terminal of generator 10. The gas from source 20 flows through 
tube 35. The gas flows from the tube via channel 38 through a tube support 
member 36 having openings 40 and 42. Tube support member 36 may be gas 
porous, if desired. The gas flows through the gap between tips 30 and 
portion 32 and down tube 18, which may comprise a metallic No. 12 
hypodermic tube. Tips 30 are as shown in FIG. 2. 
Electrode 16 may comprise a 12 mil diameter tungsten wire having a bent 
circular portion 44 at the end thereof which engages the inner surface of 
tube 35. Disposed about electrode 16 may be a metallic No. 21 hypodermic 
tube 46. The distance between the points of tips 30 and portion 32 of tube 
46 corresponds to the gap across which the auxiliary electrical discharge 
is formed and through which the gas from member 36 flows. 
Tube 46 and electrode 16 are supported by member 36 where member 36 is 
disposed in a cavity in a nose cap 48, which is made of an electrically 
insulative material, as is intermediate member 50. A gas seal plug 52 is 
employed to prevent gas flow back up around tube 35. Plastic spacers 54 
and 56 mount tube 18 within an opening 58, which extends through nose cap 
48. It is to be understood where values have been given for certain 
parameters in the foregoing description, this has been done for purposes 
of illustration only. 
In operation, gas flows through tube 18 to electrostatically charge the 
tube. When the RF voltage is applied to the electrode 16, the charge 
bleeds from tips 30 via the auxiliary discharge through the gas to the 
electrode. Thus, an electrical discharge can be initiated from active 
electrode 16 at a substantial distance from surface 26 with little, if any 
power loss in the auxiliary discharge and without the need for external 
means to initiate the discharge. 
Referring to FIG. 4, it should be understood that tube 18 need not be 
concentrically disposed about electrode 16 where the parallel embodiment 
is shown in FIGS. 2 and 3. Rather, tube 18 may also be connected in series 
with the electrode. Further, electrode 16 may be tubular as shown in FIG. 
4. Tube 18 may be collinearly and coaxially disposed with respect to 
electrode 16. In this embodiment, the tube 18 would preferably, but not 
necessarily, have about the same internal diameter as that of tubular 
electrode 16 where the gas would successively flow through, and also 
possibly around, both of the tubes. Tube 18 would be slightly spaced from 
electrode 16 and the pointed projections 30 would preferably, but not 
necessarily, extend straight out from active electrode 16 toward tube 18 
rather than be bent where the bent projection arrangement is shown in 
FIGS. 2 and 3. Electrode 16 need not be tubular in this serial embodiment. 
If not tubular, the projections 30 would more than likely be bent toward 
the tube. The distance between the projections or tips 30 and tube 18 in 
this serial embodiment would typically be about 10-20 mils although these 
values are not critical. The serial embodiment is advantageous in that the 
tube 18 can be disposed within support member or handle 14 whereby a 
particularly compact arrangement can be implemented. Also with respect to 
the projections 30, it should be appreciated that in both the serial and 
parallel embodiments, they may be disposed on either the tube 18 or 
electrode 16 or on both.