A suction coagulator includes an improved anti-clog tip. The anti-clog tip is located at the distal end of a hollow, conductive tube, the proximal end of which is connected to a handle. An interior channel runs through the conductive tube and the handle through a suction fitting thereon to a conventional source of suction. The handle also includes an electrical connection for providing electrical power to the conductive tube. An insulating layer surrounds the exterior sidewall of the conductive tube and is stripped back a distance D.sub.O of 0.050 to 0.200 inches from the distal end of the conductive tube. A thermal insulating sleeve or coating is located inside of the interior channel of the conductive tube and extends from the distal end a distance D.sub.I into said interior channel. The distance D.sub.I is approximately 11/2 to 3 times the outside diameter OD.sub.C of the conductive cannula tube. The insulating sleeve provides substantial thermal insulation and some electrical insulation. In a preferred embodiment of the invention, the distal end of the tube is flared into a bell creating an air gap having a width of D.sub.G between the insulation sleeve and the inside diameter ID.sub.B of the bell. The outside diameter of the bell is approximately equal to the outside diameter OD.sub.C of the hollow, conductive cannula tube.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a suction electrocoagulator apparatus having an 
anti-clogging tip which includes a thermally insulating sleeve that 
extends from the distal end of the hollow, conductive cannula tube into 
the interior cavity of said tube. 
2. Description of Related Art 
The coagulation of bleeding blood vessels using electrically conductive 
suction tubes, also referred to as cannulas, is a technique widely used 
for over two decades. A combined electrocautery and suction tube 
instrument is typically employed in surgery wherever excessive blood must 
be removed from the bleeding site in order to facilitate hemostat of 
bleeding vessels using the electrocautery feature of the instrument. 
Commercially available suction coagulators made expressly for 
electrocautery hemostat procedures generally have the following common 
components: 
(A) A hollow, metallic, conductive cannula tube having a suitable thickness 
of non-conducting electrical insulation on its exterior. The electrical 
insulation is absent from the first few millimeters on the tube's distal 
end in order to form an annular ring for electrocautery procedures. The 
sole purpose of the insulation is to protect the patient and doctor from 
cautery burns that would result from contact with the outside of the 
metallic tube when it is energized. 
(B) A non-metallic or electrically insulated handle. The handle includes a 
suction cavity or passageway running through its length that terminates in 
a suction fitting at one end for connection to a suction source. At its 
proximal end the handle is hermetically coupled to the hollow, metallic 
tube so that the suction cavity of the handle communicates directly with 
the suction channel of the tube. The handle may also have a venting 
passageway that connects the main suction cavity with a vent hole on the 
handle's exterior. The surgeon uses finger pressure on the vent hole to 
control the amount of suction applied. 
(C) A power cord, typically in an insulated wire, is used to connect the 
suction coagulator to a high frequency current generator. The power cord 
enters the handle and is electrically connected to the proximal end of the 
conductive suction tube using various known connecting techniques. 
One of the major problems with electrocautery suction devices is that the 
tips tend to clog with burned tissue and coagulated blood. In theory, the 
suction is supposed to remove the clog but the suction itself produces 
some problems. 
One approach has been to control the flow of air through the suction tip by 
means of a vent hole that can be manipulated by the surgeon. A useful 
description of the prior art problems is found in my prior U.S. Pat. No. 
4,932,952 entitled ANTISHOCK, ANTICLOG SUCTION COAGULATOR. The following 
patents were cited as being relevant to that approach: U.S. Pat. Nos. 
2,888,928; 3,595,234; 3,610,242; 3,828,780; 3,857,945; 3,974,833; 
4,427,006; 4,562,838; and 4,719,914. 
Another approach to minimize the coagulating of tissue in an electrocautery 
suction instrument is described in U.S. Pat. No. 3,902,494 entitled 
SUCTION SURGICAL INSTRUMENT. The general concept described therein 
provides for an electrode at the tip of the instrument located in such a 
way as to impede the introduction of tissue mass into the tube. By 
restricting the size of the opening with the conducting electrode, it is 
possible to filter out tissue that otherwise might clog the instrument 
downstream. One embodiment described in the text of U.S. Pat. No. 
3,902,494, but not illustrated in its drawings, comprehends an electrical 
lead shaped as a tube which encompasses the suction shaft 10. The purpose 
appears to be to increase the stiffness of the suction shaft. In that 
embodiment, it is assumed that the electrode tip of the suction device is 
likewise restricted to prevent tissue clogging as taught by the other 
illustrated embodiments of the invention. Insofar as understood, U.S. Pat. 
No. 3,902,494 is directed at the concept of preventing tissue clogging and 
does not appear to address the more difficult issue of clogging caused by 
the coagulation of blood at the mouth of the cannula due to the heat 
generated by the electrocautery effect. 
U.S. Pat. No. 4,682,596 entitled MEDICAL HIGH FREQUENCY COAGULATION 
INSTRUMENT describes a specialized structure incorporating an insulating 
hose inside of a ring electrode which is part of a much more complicated 
overall structure involving a second ring electrode and an exterior 
insulating layer as well as an intermediate insulating layer. The purpose 
of the device appears to provide a supply of "flushing liquid" which 
emerges around the interior electrode and then is sucked down through the 
central shaft of the interior electrode. 
U.S. Pat. No. 4,682,596 and its counterpart U.S. Pat. No. Re. 22,925 both 
describe a catheter employing an electrode and an electrically insulating 
tube. In that embodiment, the electrode appears to cover the entire front 
face of the device as illustrated in FIGS. 3 and 4 thereof. There is a 
discussion in column 8, lines 44-47 that addresses the insulating 
properties of the support for the electrode tip. 
Lastly, U.S. Pat. No. 4,347,842 entitled DISPOSABLE ELECTRICAL SURGICAL 
SUCTION TUBE AND INSTRUMENT is cited as being of general possible 
relevance only. 
While the prior art selectively discloses the concept of restricting tissue 
from entering the tip of an electrocautery tube so as to prevent clogging 
of the tube, nevertheless, it does not appear to appreciate the problem of 
blood coagulation at the tip due to electrocautery heating. Accordingly, 
none of the prior art located and described above appears to fully 
appreciate the necessity of providing appropriate thermal insulation at 
the tip in order to avoid blood coagulation. The invention described in 
detail later in this specification, provides a dramatic improvement over 
prior art devices such as described above by virtue of the fact that it 
substantially eliminates the problem previously associated with the 
formation of eschar, i.e. blood char, in the tip of electrocautery suction 
devices. 
SUMMARY OF THE INVENTION 
Briefly described, the invention comprises a suction electrocoagulator 
apparatus having an improved anti-clog tip. The anti-clog tip is located 
at the distal end of a hollow, conductive, cannula tube. The cannula tube 
includes an exterior sidewall, the distal end, a proximal end at the 
opposite end of the tube from the distal end, and an interior channel for 
connecting the proximal and distal ends together. The proximal end of the 
conductive tube is connected to the front end of a handle. A suction 
fitting is located on the rear end of the handle and is employed to 
communicate the interior cavity of the conductive tube to a source of 
suction. The handle also includes an electrical connector for providing 
high-frequency current to the tip of the conductive tube. Electrical 
insulation, in the form of a coating or sleeve, surrounds the exterior of 
the conductive tube and is stripped back by approximately 0.050 to 0.200 
inches from the distal end of the conductive tube. 
The improvement comprises a thermal insulating sleeve located inside of the 
interior channel of the conductive tube and extending a distance D.sub.I 
into the interior channel. The distance D.sub.I is preferably in the range 
of one and one-half to three times the outside diameter of the hollow, 
conductive, cannula tube. The insulating sleeve preferably provides both 
electrical and thermal insulation. The insulation can comprise either a 
combined sleeve or two discrete sleeves, one for thermal insulation and 
one for electrical insulation, located concentrically within each other. 
An alternative embodiment of the invention calls for flaring the distal end 
of the electrically conductive, hollow, metallic, cannula tube into a 
bell, the outside diameter OD.sub.B of which is larger than the outside 
diameter OD.sub.I of the cannula tube and the inside diameter which is 
larger than the downstream inside diameter ID.sub.C of the conductive 
tube. An insulator providing both electrical and thermal insulation is 
located on the inside of the bell and includes a channel therethrough that 
has a diameter ID.sub.S that is approximately the same as the inside 
diameter ID.sub.C of the conductive tube. 
The preferred embodiment of the invention calls for flaring the tip of the 
hollow, metallic, conductive cannula tube into a bell having an outside 
diameter OD.sub.B approximately equal to the outside diameter OD.sub.I of 
the insulating coating on the outside of the conductive tube. A 
cylindrical, insulating sleeve is inserted into the distal end of the 
anti-clog tip so that it extends a small distance D.sub.S beyond the bell 
and a distance D.sub.I into the throat of the anti-clog tip. An annular 
gap having a width D.sub.G is formed between the outside surface of the 
cylindrical insulating sleeve and the inside surface of the bell. The air 
gap between the insulating sleeve and the inside surface of the bell 
provides additional thermal insulation. Even though the cylindrical 
insulating sleeve slightly restricts the inside diameter of the cannula 
tube, nevertheless, the results are significantly improved because of the 
additional thermal insulating provided by the air gap between the 
insulating sleeve and the inside surface of the bell. 
These and other features of the present invention will be more fully 
understood by reference to the following drawings.

DETAILED DESCRIPTION OF THE INVENTION 
During the course of this description like numbers will be used to identify 
like elements according to the different figures which illustrate the 
invention. 
FIGS. 1A, 1B and 1C, illustrate different views of the present invention 10 
in which the improved, anti-clog tip 20 is shown in its normal context. 
The invention 10 typically includes an electrical conductor 12, which is 
connectable to a conventional source of high frequency current, a handle 
14, a vent hole 16, and cannula tube 22. Cannula tube 22 is surrounded by 
an electrically insulating coating 18 which is stripped back a distance of 
D.sub.S from the distal end of the hollow, conductive, metallic cannula 
tube 22. The proximal end of the cannula tube 22 is connected to the front 
end 28 of handle 14. A suction fitting 24 is located at the rear of handle 
14 and connects with a hollow interior cavity 26 which communicates with 
the interior cavity and opening 30 of the cannula 22. Handle structures 
that might be suitable for use with the present invention 10 are described 
in the prior art. See, for example, U.S. Pat. No. 3,828,780 and my U.S. 
Pat. No. 4,932,952 previously discussed. 
FIGS. 2-6 illustrate various different embodiments of the improved 
anti-clog tip 20 in further detail. 
According to FIG. 2, the electrically conductive, tubular cannula 22 
extends a distance D.sub.O beyond the exterior insulating sleeve 18. 
Conductive tube 22 has a central axis 32 and a front opening 30 which 
draws in air and blood under the influence of suction applied to suction 
fitting 36 as illustrated in FIGS. 1A-1C. The embodiment 40, of FIG. 2, 
includes a front face 44 and a thin interior Teflon.RTM. sleeve 42 which 
extends a distance D.sub.I from the front face 44 into the interior of the 
electrically conductive tube 22. The purpose of sleeve 42 was to provide 
electrical insulation but not thermal insulation. The distance D.sub.I 
extended approximately 11/2 to 3 times the diameter of the tube into the 
suction channel. For tonsillectomy procedures the interior diameter of the 
tube is typically 0.100 inches, and the outside diameter of the tube 22 is 
typically 0.120 inches and, therefore, the distance D.sub.I might vary 
between 0.150 to 0.360 inches. While the electrical insulation embodiment 
40 of FIG. 2 works (with proper sizing of the Teflon.RTM. sleeve 
thickness), it does not provide the dramatically improved level of results 
achieved with embodiments 3-6, described below. 
Embodiment 50, illustrated in FIG. 3, includes a tubular electrode 22, 
which extends a distance D.sub.O beyond the outer electrical sleeve 18. An 
electrical and thermal insulating sleeve or coating 52 is located within 
the inside diameter of cannula 22 and extends a distance D.sub.S beyond 
the front face 44 of cannula 22. The distance D.sub.S should be short 
enough so that the electrical and thermal insulating sleeve 52 does not 
interfere with the surgeon's ability to touch tissue with the cautery tip 
face 44. The minimum distance D.sub.I that the sleeve 52 must extend into 
the cannula 22 may be derived empirically but testing indicates that a 
distance of 11/2 to 3 times the outside diameter of the cannula tube 22 is 
adequate (i.e., D.sub.O =11/2-3 OD.sub.C). The thickness T.sub.S of the 
sleeve 52 depends upon the physical properties of the thermal insulating 
material selected. It must be thick enough to prevent the passage of most 
of the heat of cautery while at the same time insulating the inside 
surface from most or all of the electrocautery current. The design 
parameters for this are complex. The material of the sleeve 52 must be 
biocompatible, have low thermal conductivity, high electrical resistivity, 
and be capable of withstanding temperatures up to approximately 
500.degree. F. Good candidate materials for sleeve 52 would include, but 
not be limited to, glass, or high temperature plastics such as Teflon.RTM. 
(polytetrafluoroethylene), polysulfone, polyethersulfone, or 
polyetherimide. The preferred electrical resistivity of the sleeve is 
greater than 10.sup.12 ohm cm and preferably about 10.sup.16 ohm cm. For 
good results the material selected should have a thermal conductivity less 
than 0.6 . While the foregoing thermal conductivity is good, the apparatus 
also operates satisfactory with a sleeve thermal conductivity of 
approximately 0.10 . 
According to the preferred embodiment, the cannula tube 22 is preferably 
made from an electrically conducting material such as brass, aluminum or 
steel. The basic electrical insulation 18 on the outside of the cannula 22 
is preferably polyolefin but could be PVC, PTFE or any other flexible, 
suitable plastic material. The insulation 18 is preferably stripped back a 
distance D.sub.O of 0.05 to 0.200 inches from the bare cautery tip face 44 
of the cannula 22. 
FIG. 4 illustrates an embodiment 60 in which the insulating sleeve can 
comprise two concentric sleeves 62 and 64. According to the preferred 
embodiment, the innermost sleeve 64 comprises an electrical insulating 
material preferably PTFE, FEP, PFA, or polyetherimide. Its thickness 
T.sub.E is preferably 0.010 and in the range of 0.003 to 0.020 inches. 
Thermal insulating sleeve 62 surrounds the electrical insulating sleeve 64 
and has a thickness T.sub.T of approximately 0.010 and could be in the 
range of 0.005 to 0.020 inches. The preferable material for the thermal 
insulating sleeve 62 is filled epoxy but could be filled silicone or 
fiberboard. 
An improved alternative embodiment 70 is illustrated in FIG. 5. Embodiment 
70 includes a modified tip that preserves the inside diameter ID.sub.C 
while utilizing the basic design principles of the present invention to 
prevent blood coagulation due to thermal heating. According to embodiment 
70, the end of the conductive cannula tube 22 is flared to form a bell 72. 
The outside diameter OD.sub.B of the bell 72 is larger than the outside 
diameter OD.sub.I of the insulating sleeve 18. It is possible with this 
structure to place an electrical and thermal insulating sleeve 74 into the 
mouth of the bell 72 in such a way that the inside diameter ID.sub.S of 
the sleeve 74 is approximately the same or greater than the downstream 
inside diameter ID.sub.C of the conductive cannula tube 22. According to 
the tip embodiment 70, the sleeve 74 could be a homogenous material having 
both electrical and thermal insulating properties, such as illustrated by 
sleeve 52 in the embodiment 50 illustrated in FIG. 3. Alternatively, the 
sleeve 74 could be comprised of two separate concentric sleeves, one for 
thermal insulation and the other for electrical insulation, such as 
sleeves 62 and 64 illustrated in embodiment 60 of FIG. 4. This embodiment, 
however, requires an awkwardly large outside diameter of the bell in order 
to accommodate sufficient thickness for the electrical and thermal 
insulating sleeve(s) 74. Another version of embodiment 70 would be to 
reduce the outside diameter OD.sub.B of the bell while making the 
insulating sleeve inside diameter ID.sub.S somewhat less than the 
downstream inside diameter ID.sub.C of the conductive cannula. 
The preferred tip embodiment 80 of the invention 10 is illustrated in FIG. 
6. This tip was the most successful of those used in field trials. It was 
especially useful for the type of electrocautery suction tubes that are 
used in tonsillectomy, adenoidectomy, or sinuscopy procedures. According 
to the preferred embodiment 80, it is desired to use a bell-shaped tip 72, 
such as illustrated by embodiment 70 of FIG. 5, but, because of surgeon's 
preference, to limit the outside diameter of the bell OD.sub.B to 
approximately match the outside diameter OD.sub.I of the external 
insulation 18. An electrical/thermal insulating sleeve 82 having an inside 
diameter ID.sub.S is located in the opening 30 of the instrument and 
extends a distance D.sub.S beyond the front face 44 of the bell 72 and has 
a length L.sub.S sufficient so that it extends into, and is held in place 
by, the sidewalls of the upstream cannula tube 22. The exterior wall of 
the insulating sleeve 82 defines an air gap 84 with respect to the 
interior wall of the flared, bell section 72 of the cannula tube 22. The 
annular air gap 84 formed between the sleeve 82 and the bell 72 acts as a 
very good thermal insulator so that the required thickness of the 
insulating sleeve 82 is largely reduced to the minimum required for 
electrical insulating properties. While it is possible to fill the gap 84 
with a thermal insulator, it is has been found that the air gap 84 
provides more than adequate thermal insulation with a sleeve 82 having a 
thickness T.sub.S of approximately 0.010 inches for tonsillectomy size 
suction tubes. 
EXPERIMENTAL RESULTS 
The results achieved by using the basic invention, especially embodiments 
70 and 80, illustrated in FIGS. 5 and 6, were exceptionally good. For 
years electrocautery suction tube designers have attempted to minimize 
clogging by modifying the port designs such as described in my prior U.S. 
Pat. No. 4,932,952. While the modified port designs improved the 
situation, they did not remedy the underlying problem, namely that the 
tips would still clog. Accordingly, tests were initiated to try to 
determine the root causes for tip clogging. 
It was generally thought, prior to the time of the present invention, that 
the cause of rapid coagulation of blood within the tip of electrocautery 
suction tubes was the direct result of the fulguration effects of the 
electrocautery current discharged at that location. Therefore, my first 
approach was to attempt to electrically insulate the inside diameter and 
tip end with a 0.006 inch coating of polytetrafluoroethylene (i.e., 
Teflon.RTM.) as illustrated in embodiment 40 of FIG. 2. The coating 42 
extended a distance D.sub.I of approximately 1/2 inch into the tube 22 
from its tip 44 and its thickness essentially precluded the conductance of 
current in the coated area through resistive or capacitive means. The 
concept was to drive all the cautery current to the outside of the tip 40. 
Embodiment 40 was tested at the North Carolina State University College of 
Veterinary Medicine using fresh drawn horse blood. Suction tubes having 
tips with and without the coating 42 were each placed into a 100 ml 
plastic cup filled with horse blood. The ESU generator was set at 50% 
coagulation power and activated with moderate suction applied to the 
suction port. Without exception, the uncoated samples clogged within 10 to 
20 seconds and the coated ones did not. Moreover, the inside diameters of 
the coated samples were completely clean. 
Initially, it was believed that embodiment 40, illustrated in FIG. 2, 
solved the problem, but it was later discovered through actual use in 
tonsillectomy procedures that those tubes clogged almost as often as the 
uncoated ones. 
It was then observed that the laboratory tests did not simulate actual use 
of the device in one important aspect, namely, that in the laboratory the 
tip of the cannula was always submerged in blood that was being drawn up 
into the cannula. The circulating blood kept the tip cool by removing the 
heat generated by cautery. In actual use, however, suction is used first 
to remove most of the blood to visualize the bleeder area so that when 
cautery is applied only a mixture of air and a small amount of blood 
passes up the cannula to cool the tip. Therefore, the laboratory protocol 
provided much more liquid cooling of the cautery tip than was found in 
actual use. This observation led correctly to the speculation that the 
coagulation of blood within the cautery tip could be minimized if the 
cautery tip was insulated inside the diameter from both the electrocautery 
current and the heat it generated. The resulting tip is a structure that 
easily and economically prevents the clogging of electrocautery tips from 
both tissue and blood in a safe, dependable manner. 
While the invention has been described with reference to a preferred 
embodiment, it will be appreciated by those of ordinary skill in the art 
that modifications can be made to the structure and function of the basic 
invention without departing from the spirit and scope of the invention as 
a whole.