Surgery – Instruments
Reexamination Certificate
1998-06-23
2002-12-17
Peffley, Michael (Department: 3739)
Surgery
Instruments
C606S046000, C606S051000, C606S205000
Reexamination Certificate
active
06494877
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to electrosurgical apparatus and in particular to such apparatus for performing laparoscopic, pelvoscopic, arthroscopic, thoroscopic and the like surgical procedures. Procedures of the foregoing type are experiencing explosive growth in that incisions are kept to a minimum size and thus such procedures facilitate shorter hospital stays and lower costs. For example, with laparoscopic surgery, a patient can return to, normal activity within about one week, whereas with procedures where a large incision is made, about a month for full recovery may be required. It is to be understood that hereinafter and in the claims, whenever the term “laparoscopic” is employed, similar procedures such as pelvoscopic, arthroscopic, thoroscopic, and the like where small incisions of the foregoing type are made are also encompassed by this term.
Prior art electrosurgical laparoscopic apparatus typically include an active electrode probe that is removably insertable through a trocar sheath and that includes an electrode having an insulative coating thereon. The tip of the probe may be of different conventional shapes such as needle-shape, hook-shape, spatula-shape, graspers, scissors, etc. and serve various conventional functions such as suction, coagulation, irrigation, pressurized gas, cutting, etc. There are, however, various problems which may arise with respect to the use of such a prior art apparatus when used in laparoscopic or like procedures.
A first problem may arise if the insulation on the active electrode is damaged thereby allowing active current (possibly in the form of arcing) to pass therethrough directly to the patient's tissue (possibly the bowel or colon) whereby peritonitis may set in within several days. A second problem which can arise with prior art apparatus is caused by a capacitive effect where one electrode of the capacitance is the active electrode and the other electrode of the capacitance is a metallic trocar sheath and the dielectric between these elements is the insulation on the active electrode. Current from the active electrode will be capacitively coupled to the trocar sheath and then returned through the body and the return electrode to the generator. If this current becomes concentrated, for example, between the trocar sheath and an organ such as the bowel, the capacitive current can cause a burn to the organ. A third potential problem occurs if the active electrode contacts another instrument within the peritoneal cavity such as metallic graspers or the like. The above-mentioned capacitive effect also arises in this situation where the first electrode is the active electrode and the second electrode is the metallic graspers or the like. Thus, where the grippers contact a unintended site, injury may occur.
To solve some of the above identified problems, an electrosurgical apparatus as disclosed in U.S. Pat. No. 5,312,401 to Newton et al. and assigned to the assignee of the present invention has been proposed, the contents of which are incorporated herein by reference. Newton et al. disclose an electrosurgical apparatus that includes a safety shield that surrounds an active electrode and that includes insulation provided at least on the outer surface of the shield and preferably also provided on the inner surface of the shield. The safety shield is connected to a return lead via a low impedance path that includes monitoring circuitry used to detect the shield current and determine an abnormal condition therefrom.
In the event that the insulation on the active electrode is damaged, current will pass through the damaged insulation to the shield and then be returned to the return lead via the low impedance electrical connection between the shield and the return lead of the electrosurgical generator. A monitor circuit responsive to the shield current deactivates the electrosurgical generator whenever the shield current corresponds to an abnormal condition such as an insulation breakdown. The insulated shield of Newton et al. also addresses the second and third above-mentioned problems by harmlessly returning any current which is capacitively coupled to the shield to the return lead via the above-mentioned low impedance connection.
Referring to
FIG. 1
a cross-sectional view of an illustrative laparoscopic apparatus in accordance with Newton et al. is shown. A tubular safety shield assembly
15
includes a tubular shield
9
having a layer of insulation
11
provided on the outer surface thereof and an optional layer of insulation
13
provided on the inner surface thereof. The tubular shield assembly is inserted through trocar sheath
1
to thereby provide a passageway through which the active electrode probe
3
may be inserted. An elongated port
23
may extend through the active electrode through which irrigation fluids, suction, a pressurized gas stream, etc. may pass. When active probe
3
and tubular shield assembly
15
are in their respective inserted positions as shown in
FIG. 1
, the shield
9
surrounds the active probe from at least (a) a proximal point
17
prior to the entry point
19
of the active probe into the trocar sheath
1
to (b) a distal point
21
in proximity to the tip
7
of the active probe. Shield monitor circuitry
25
is connected to shield
9
via a dual conductor lead
27
whereby the integrity of the connection of the shield to the monitor circuitry can be monitored.
The active electrode probe
3
is connected to an electrosurgical generator
31
which may be of a conventional type via an active lead
35
. The electrosurgical generator is connected to a patient return electrode
37
, preferably of the dual area type, via the shield monitor circuitry
25
and, in particular, the return terminal of the generator is connected to circuitry
25
via lead
29
while the circuitry
25
is connected to the return electrode via lead
33
. Upon detection of a fault condition by the shield monitor circuitry, the electrosurgical generator
31
may be deactivated by opening a relay in the connection between the generator and patient return electrode
37
although other means may also be employed to deactivate the generator.
Referring to
FIG. 2
a generalized block diagram of the shield monitor circuitry
25
shown in FIG.
1
and used in Newton et al. is shown. A conductivity monitor
39
is connected to dual lead
27
, the purpose of the conductivity monitor circuit being to measure the integrity of the connection of lead
27
to shield
9
. The dual connection provides a redundant path for shield monitoring current which is applied to lead
27
as will be described in more detail hereinafter with respect to
FIG. 9. A
shield current sensor
41
senses the current passing from the shield
9
to return electrode lead
29
,
33
and may provide a signal voltage proportional to the instantaneous value of the shield current.
Measurement electronics circuitry
43
includes various circuits for measuring different parameters of at least the sensed shield current. The first of these circuits is a full bandwidth amplitude sensor circuit
47
which measures the amplitude of the full bandwidth of the sensed shield current. Processing and decision circuitry
53
determines whether this amplitude exceeds a predetermined threshold and, if it does, a fault condition may be applied to indicators
61
over line
55
. Indicators
61
may be aural and/or visible and provide an appropriate alert. A data logger
73
may also be connected to processing and decision circuitry
53
to provide a hard copy of various safety conditions.
In addition to applying an alert signal over line
55
, a generator deactivate signal is applied over line
69
to a relay
71
which opens the connection between return electrode
37
and generator
31
to thus deactivate the generator and discontinue the application of electrosurgical energy. That is, the monitor circuitry
25
, when used outside host electrosurgical generator
31
, is preferably used with an electrosurgical generator of the type having a dual return electr
Boyle Don R.
Emerling Paul H.
Newton David W.
Odell Roger C.
Steinway Robert C.
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