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

An electrosurgical method and apparatus for coagulating by fulguration where the electrical discharge is established through a formation of flowing inert gas where the formation may either be a diffuse blanket of the flowing gas or a well defined column thereof.

RELATED APPLICATIONS 
This application is related to a first U.S. patent application Ser. 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" and a second U.S. patent 
application Ser. No. 649,682 filed on Jan. 16, 1976 by Charles F. 
Morrison, Jr., entitled "Improved Electrosurgical Method and Apparatus for 
Initiating an Electrical Discharge in an Inert Gas Flow", all of the 
foregoing applications being assigned to the same assignee. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to electrosurgery and in particular an 
electrosurgical method and apparatus for coagulating by fulguration. 
2. Discussion of the Prior Art 
Electrosurgical coagulation by fulguration consists of the establishment of 
electrical discharges to body tissue with bursts of radio-frequency 
energy. It is used to dehydrate, shrink, kill, or char the tissue. This is 
most often to stop bleeding and oozing, or to otherwise seal the tissue. 
Conventional fulguration techniques are complicated by the following: 
1. Very high voltages are required to start and maintain the high crest 
factor sparking needed for effective fulguration. Few solid state 
electrosurgical generator systems can provide the output parameters needed 
for truly satisfactory performance. Sparks are typically short and hard to 
start and control. 
2. With high voltage and crest factor, as provided by conventional 
generators, the precise control of the fulguration site is impossible due 
to the "arc" nature of the discharge. The spark does not issue from the 
point of the electrode in the direction indicated, but arcs from the side 
of the point in a curved trajectory to nearby flesh. The spark wanders 
increasingly with greater spark length. Fulguration at the bottom of a 
hole or crevice is especially difficult to achieve. 
3. Should the electrode accidentally touch the tissue, the partially 
dehydrated tissue can often adhere to the hot electrode and be 
inadvertently ripped away creating unnecessary complications. In addition 
to surgical complications, such sticking fouls the electrode such that it 
must be scraped clean before continuing the operation. 
4. Conventional fulguration systems cannot be used to quickly treat large 
areas of bleeding or oozing flesh. 
5. Considerable volumes of dense unpleasant smoke and fumes are produced. 
SUMMARY OF THE INVENTION 
With this invention, the above difficulties can be totally eliminated. In 
particular, a primary object of this invention is the provision of an 
electrosurgical method and apparatus for coagulating by fulguration where 
the electrical discharge is established through a formation of flowing 
inert gas where the formation may either be a diffuse blanket of the 
flowing gas or a well defined column thereof. 
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 such 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 wave form has a high crest factor -- that is, 
typically 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. Source 10 is connected to an electrosurgical 
instrument generally indicated at 12. Instrument 12 basically comprises a 
support member 14, which may function as a handle. Member 14 supports an 
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. As can 
be seen in FIG. 1, a return path 11 is provided from tissue 26 to source 
10. 
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 especially with respect to initiation of the electrical 
discharge, as will be discussed further hereinafter. 
In FIGS. 2-4 there are shown electrode structures generally corresponding 
to that shown in FIG. 1. In FIG. 2, intermediate member 18 comprises a 
hollow tube disposed about and surrounding electrode 16 whereby an annular 
passageway 22 is provided through which the gas from source 20 flows. The 
tube has as opening 23, the area of which is preferably the same as the 
cross-sectional area of passageway 22 although advantageous results are 
obtained whenever the gas flow is focused. Thus, the exit from passageway 
22 may also be cone shaped with the cone gently flaring inwardly to the 
end of passageway 22. Hence, as the gas flows out of opening 23, an 
outwardly extending, focused formation (as opposed to a diffuse formation) 
such as a column or cone of 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 such as body tissue or the 
like. The active electrode is electrically conductive and typically may be 
made from tungsten, stainless steel, etc., while the tube 18 may be made 
from an electrically insulative material. The radial distance between 
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 is 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 and thus, is a very 
important aspect of the invention. 
In FIG. 3, the electrode 16 comprises a hollow tube having a passageway 25 
for the inert gas. The tube is truncated at the end thereof to form an 
opening 27 having an inside diameter of typically about 15-60 mils 
internal diameter, it being understood that the foregoing values are not 
critical to the desired formation of a column of gas. A sharp point 28 
results due to the truncation of tube 16. Intermediate member 18 comprises 
a coating disposed on electrode 16 where preferably the coating is made of 
electrically insulating material. The gas flows through the electrode, 
cooling it very effectively, while providing the conduction column to the 
flesh. This arrangement provides excellent fulguration, but eventually the 
sharp point 28 tends to burn away. Directability is excellent, but spark 
length is less with this arrangement than with those of FIGS. 2 and 4. 
In FIG. 4, the arrangements of FIGS. 2 and 3 are combined whereby gas flows 
through tubes 16 and 18. Preferably different gas flow rates are 
established in tubes 16 and 18. This can be effected by the employment of 
an additional gas source 21 or appropriate means (not shown) can be 
employed in the line from source 20 to effect the desired flow rates in 
tube 16 and 18 where the flow velocity in tube 16 may typically be about 
five times that in tube 18. This embodiment performs very well. The gas 
flow down center tube 16 provides directionality. It flows gently down 
outer tube 18 to prevent oxidation of the inner tube and to give 
additional gas column diameter. This enhances the the length of the 
discharge with respect to that obtainable in the FIG. 3 embodiment. 
Further, it is also preferable to employ different gases in tubes 16 and 18 
where the gas in center tube 16 discharges more readily than that in tube 
18 to thereby enhance the effectiveness and directivity of the discharge. 
Thus, argon as the center tube gas and nitrogen as the outer tube gas 
provides a better focus and directability than the use of argon in both 
streams. Also, for example, argon in the outer tube and helium in the 
inner tube focuses better than helium in both channels. 
In FIGS. 2-4 embodiments, the gas flow rate typically established in tube 
18 in FIG. 2, tube 16 in FIG. 3, and tube 16 in FIG. 4 is about 0.02 
standard cubic feet per minute while pressure of the gas in the column at 
the tissue is about 0.25 p.s.i. although it is to be understood that these 
values are not critical. Although electrode 16 is preferably pointed in 
FIG. 2 and preferably has a sharp point 28 in FIGS. 3 and 4 in order to 
facilitate initiation of the electrical discharge, it has been determined 
that when helium is used as the inert gas, electrode 16 may be 
non-pointed. Thus, for example, a perpendicularly cut-off tube of small 
diameter (32 mils, e.g.) may be used as electrode 16 where the discharge 
is essentially self-starting in helium after several touch-down starts. 
The fulguration provided by all of the devices of FIGS. 2-4 is excellent 
when used with practically all electrosurgical generators, including solid 
state generators. The electrical discharge is typically 3/8 to 3/4 inches 
in length, making it easy to control. Precise control of the fulguration 
site is provided by the spark being straight and in the directed, 
columnated gas stream. The spark is easily directed to the bottoms of 
holes and crevices. It is not deflected to adjacent conducting structures 
as is the case in the absence of a gas flow pattern. Because of the long, 
electrical discharge there is little danger of accidentally touching the 
tissue with the discharging tip. In any event, very little of the tip is 
sufficiently hot to stick to the flesh, in that the gas flow keeps the 
structure very cool compared with other electrosurgical electrodes. In the 
columnar flow systems of FIGS. 2-4, the electrical discharge covers a well 
defined area, and can be swept across the tissue to provide rapid coverage 
of wide areas. Thus, such systems are many times as effective (for many 
applications) as the same generator with a conventional electrode. In 
addition, the quantity of smoke and fumes generated is an order of 
magnitude less than with prior art arrangements. 
In FIG. 5, there is illustrated a method for producing coagulation by 
fulguration where a diffuse blanket of inert gas is formed between 
electrode 16 and tissue 26 as opposed to a focused formation such as the 
column of inert gas formed by the embodiments of FIGS. 2-4. The 
configuration of the instrument of FIG. 5 corresponds to that of a typical 
thermal-inert-gas (TIG) welder; however, it is employed for tissue 
coagulation in accordance with one aspect of the invention. As can be 
appreciated, the electrically insulated cover has a turned-in portion 30 
with an opening 32 disposed therein. Thus, the gas which flows through the 
annular space between electrode 16 and 18 encounters portion 30 and 
eventually is diffused out opening 32 to form a a diffuse blanket (as 
opposed to a column) of the inert gas between the electrode and the 
tissue. As indicated hereinbefore with respect to FIGS. 2-4, there is 
preferably little, if any, obstacle such as end portion 30 in the gas flow 
paths in the embodiments of these figures. Rather, the area of opening 27 
of tube 16 in FIGS. 3 and 4 and the area of opening 23 of tube 18 in FIGS. 
2 and 4 are preferably, substantially the same as the cross-sectional 
areas of passageway 25 and passageway 22, respectively. Hence, the 
establishment of a column of gas occurs in the embodiments of FIGS. 2 
through 4. Thus, the discharge established by the embodiments of these 
figures is both long and directed while that of the FIG. 5 embodiment is 
long but not directed due to the diffuse nature of the gas blanket. 
Nevertheless, the FIG. 5 embodiment is useful in many electrosurgical, 
coagulation applications due to the discharge length, as will be discussed 
further hereinafter. 
In welding applications, the gas blanket established by a TIG welder 
provides two functions. First, it provides an inert cover for the hot 
welding tip and the heated work piece such that oxygen is excluded, 
preventing corrosion. Second, it provides a medium in which a gaseous 
discharge can be readily initiated, by application of an essentially 
continuous wave, radio frequency (RF) power. Once the discharge is 
initiated, the RF power is turned off so that thereafter only a low 
frequency or DC current is applied to the electrode. Thus, the discharge 
initiated by the RF power permits striking of the low voltage welding arc 
without the electrode touching the work piece. If applied to living 
tissue, the low frequency or DC welding current could cause fibrilation 
and death if its driving voltage were sufficiently high. The raw blast of 
RF voltage used to start the welding arc is not suitable for either 
welding or fulguration. 
Hence, in accordance with a further aspect of this invention, the TIG 
welder configuration of FIG. 5 is employed for electrosurgical coagulation 
by applying to the instrument either continuous wave electrical energy or 
periodic blasts of high frequency, electrical energy, such as produced by 
source 10 of FIG. 1. The source 10 output is employed as long as an 
electrical discharge takes place between electrode 16 and tissue 26 of 
FIG. 5, as opposed to the welding arrangement where the RF power is 
applied only during the time interval necessary to initiate the arc. 
The FIG. 5 embodiment is somewhat limited, due in part to the diffuse 
nature of the gas flow, and in part due to the vaporized materials issuing 
from the flesh which contaminate the gas. In spite of this, the 
application of this embodiment provides spark length and fast wide 
coverage not available with conventional electrosurgical tools. 
The embodiments of FIGS. 2, 3 and 5 are also advantageous in that the 
primary electrical discharge from the tip of electrode 16 can be readily 
initiated. In particular, whenever a person such as a doctor grips the 
instrument and, for example, places his finger on tube 18, an auxiliary 
electrical discharge will be established between the interior of tube 18 
and electrode 16. The auxiliary discharge results from the electric field 
established between the doctor's finger and the active electrode 16 where 
the latter two will be at different electric potentials depending on 
various factors such as the magnitude of the voltage on electrode 16, the 
thickness of tube 18, etc. Tube 18 should be electrically insulative and 
preferably thick enough to prevent discomfort to the doctor while thin 
enough to permit establishment of the auxiliary discharge. The auxiliary 
discharge will be spaced from the electrode tip a certain distance 
depending on where the doctor places his finger. It is thought that the 
ions generated in the auxiliary electrical discharge are swept by the 
flowing gas to the electrode tip to initiate the primary discharge at the 
tip although there is no intent to be limited to a particular theory of 
operation.