|
Medical Patent Abstract
A medical device (5) is provided which comprises a catheter tube
having a distal end and a lumen, and configured to assist in applying
tamponage to a bleeding source in a gastrointestinal tract when
flexed. A catheter tip having a catheter tip outer surface is assembled
with the tube adjacent the distal end of the tube. The catheter
tip comprises a probe body comprising an electrically insulative
material, at least one electrode pair located on the probe body
which comprises a first electrode spaced from a second electrode,
and a fluid distribution manifold to direct a fluid from inside
the probe body towards the tip outer surface. The manifold comprises
a central passage within the probe body and a plurality of lateral
passages which extend from the central passage towards the tip outer
surface. An extendable injection needle is housed within the central
passage to provide treatment to tissue.
Medical Patent Claims
I claim:
1. A medical device comprising: a catheter tube having a distal
end and a lumen, the tube configured to assist in applying tamponage
to a bleeding source in a gastrointestinal tract when flexed; a
catheter tip assembled with the tube adjacent the distal end of
the tube, the catheter tip having a catheter tip outer surface and
including: a probe body comprising an electrically insulative material;
at least one electrode pair, the electrode pair comprising a first
electrode spaced from a second electrode, the first electrode and
the second electrode located on the probe body; a fluid distribution
manifold to direct a fluid from inside the probe body towards the
tip outer surface, the manifold comprises a central passage within
the probe body and a plurality of lateral passages which extend
from the central passage towards the tip outer surface, the central
passage having a closed distal end; and an injection needle housed
within the central passage, the needle extendable from the central
passage to provide treatment to tissue.
2. The medical device of claim 1 wherein a portion of the catheter
tip is configured to be penetrated by a portion of the needle.
3. The medical device of claim 1 wherein a portion of the catheter
tip is configured to open around a portion of the needle.
4. The medical device of claim 1 wherein a portion of the catheter
tip is configured to least partially seal with a portion of the
needle.
5. The medical device of claim 1 wherein a portion of the catheter
tip is configured to electrically insulate the needle from the electrodes.
6. The medical device of claim 1 wherein a portion of the catheter
tip provides a guide portion for guiding the needle from the lumen
of the catheter tube to the central passage within the probe body.
7. The medical device of claim 1 wherein: the closed distal end
of the central passage is formed of a polymer material.
8. The medical device of claim 1 further comprising: a first electrical
connection to the catheter tip; a second electrical connection to
the catheter tip; and a member comprising an electrically insulative
portion, the electrically insulative portion electrically insulating
the first electrical connection from the second electrical connection
to inhibit a short circuit from forming between the two connections
in the presence of an electrically conductive fluid.
9. The medical device of claim 1 wherein: each electrode extends
longitudinally along the probe body; and the plurality of lateral
passages are spaced longitudinally along the probe body.
10. The medical device of claim 9 wherein: at least a portion of
the plurality of lateral passages extend to an outlet opening located
on the tip outer surface; and the tip outer surface comprises an
outer surface of at least one of the first and second electrodes.
11. The medical device of claim 1 wherein: each electrode extends
spirally around the probe body; and the plurality of lateral passages
are spaced spirally around the probe body.
12. The medical device of claim 11 wherein: at least a portion
of the plurality of lateral passages extend to an outlet opening
located on the tip outer surface; and the tip outer surface comprises
an outer surface of at least one of the first and second electrodes.
13. The medical device of claim 1 wherein: each electrode extends
circularly around the probe body; and the plurality of lateral passages
are spaced circularly around the probe body.
14. The medical device of claim 13 wherein: at least a portion
of the plurality of lateral passages extend to an outlet opening
located on the tip outer surface; and the tip outer surface comprises
an outer surface of at least one of the first and second electrodes.
15. The medical device of claim 1 wherein: each electrode extends
circumferentially around the probe body; and the plurality of lateral
passages are spaced circumferentially around the probe body.
16. The medical device of claim 15 wherein: at least a portion
of the plurality of lateral passages extend to an outlet opening
located on the tip outer surface; and the tip outer surface comprises
an outer surface of at least one of the first and second electrodes.
17. The medical device of claim 16 wherein: at least a portion
of the plurality of lateral passages extend to an outlet opening
located on the tip outer surface; and the tip outer surface comprises
an outer surface of at least one of the first and second electrodes.
18. The medical device of claim 1 wherein: each electrode extends
both longitudinally and circumferentially around the probe body;
and the plurality of lateral passages are spaced both longitudinally
and circumferentially around the probe body.
19. The medical device of claim 1 wherein the at least one electrode
pair comprises two electrode pairs.
20. The medical device of claim 1 wherein the at least one electrode
pair comprises three electrode pairs.
Medical Patent Description
This application is being filed as a PCT International Patent application
in the name of TissueLink Medical, Inc. (a U.S. national corporation),
applicant for the designation of all countries except the US, and
Michael E. McClurken (a U.S. resident and citizen), applicant for
the designation of the US only, on 11 Dec. 2002.
FIELD OF THE INVENTION
This invention relates generally to the field of medical devices,
methods and systems for use upon a body during surgery. More particularly,
the invention relates to electrosurgical devices, methods and systems
for use upon tissues of a human body during therapeutic endoscopy.
BACKGROUND
Electrosurgical devices configured for use with a dry tip use electrical
energy, most commonly radio frequency (RF) energy, to cut tissue
or to cauterize blood vessels. During use, a voltage gradient is
created at the tip of the device, thereby inducing current flow
and related heat generation in the tissue. With sufficiently high
levels of electrical energy, the heat generated is sufficient to
cut the tissue and, advantageously, to stop the bleeding from severed
blood vessels.
Current dry tip electrosurgical devices can cause the temperature
of tissue being treated to rise significantly higher than 100.degree.
C., resulting in tissue desiccation, tissue sticking to the electrodes,
tissue perforation, char formation and smoke generation. Peak tissue
temperatures as a result of RF treatment of target tissue can be
as high as 320.degree. C., and such high temperatures can be transmitted
to adjacent tissue via thermal diffusion. Undesirable results of
such transmission to adjacent tissue include unintended thermal
damage to the tissue.
Using saline to couple RF electrical energy to tissue inhibits
such undesirable effects as sticking, desiccation, smoke production
and char formation. One key factor is inhibiting tissue desiccation,
which occurs if tissue temperature exceeds 100.degree. C. and all
of the intracellular water boils away, leaving the tissue extremely
dry and much less electrically conductive. However, an uncontrolled
or abundant flow rate of saline can provide too much cooling at
the electrode/tissue interface. This cooling reduces the temperature
of the target tissue being treated, and the rate at which tissue
thermal coagulation occurs is determined by tissue temperature.
This, in turn, can result in longer treatment time to achieve the
desired tissue temperature for treatment of the tissue. Long treatment
times are undesirable for surgeons since it is in the best interest
of the patient, physician and hospital to perform surgical procedures
as quickly as possible.
RF energy delivered to tissue can be unpredictable and often not
optimal when using general-purpose generators. Most general-purpose
RF generators have modes for different waveforms (e.g. cut, coagulation,
or a blend of these two) and device types (e.g. monopolar, bipolar),
as well as power levels that can be set in watts. However, once
these settings are chosen, the actual power delivered to tissue
and associated heat generated can vary dramatically over time as
tissue impedance changes over the course of RF treatment. This is
because the power delivered by most generators is a function of
tissue impedance, with the power ramping down as impedance either
decreases toward zero or increases significantly to several thousand
ohms. Current dry tip electrosurgical devices are not configured
to address a change in power provided by the generator as tissue
impedance changes or the associated effect on tissue and rely on
the surgeon's expertise to overcome this limitation.
One medical condition which employs RF energy in treatment is gastrointestinal
(GI) bleeding, with such treatment typically administered via gastrointestinal
endoscopy. Bleeding in the upper gastrointestinal tract may result
from, for example, peptic ulcers, gastritis, gastric cancer, vascular
malformations such as varices (e.g. esophageal) and other lesions.
Bleeding in the lower gastrointestinal tract may result from, for
example, vascular malformations such as hemorroidal varices.
Peptic ulcer bleeding is one of the most common types of non-variceal
upper gastrointestinal bleeding. Peptic ulcer bleeding results from
the combined action of pepsin and hydrochloric acid in the gastric
or digestive juices of the stomach. Peptic ulcers further include,
for example, gastric ulcers, an eroded area in the lining (gastric
mucosa) of the stomach, and duodenal ulcers, an eroded area in the
lining (duodenal mucosa) of the duodenum. Peptic ulcers may also
be found in Meckel's diverticulum.
Endoscopic modalities for the treatment of upper gastrointestinal
bleeding include injection therapy (e.g. diluted epinephrine, sclerosants,
thrombogenic substances, fibrin sealant), mechanical clips and so
called thermal (heating) methods. Thermal methods are often divided
into so called non-contact thermal methods and contact thermal methods.
Non-contact thermal methods include laser treatment and, more recently,
argon plasma coagulation (APC). Thermal contact methods include
multipolar electrocoagulation and thermal coagulation probes.
Non-contact thermal probe methods depend on the heating of tissue
protein, contraction of the arterial wall and vessel shrinkage.
One drawback of non-contact thermal methods is the "heat sink
effect" where flowing arterial blood leads to dissipation of
the thermal energy. Because of the greater tissue penetration, the
neodymium: yttrium aluminum garnet (Nd:YAG) laser is generally superior
to the argon laser for ulcer hemostasis. In any event, laser units
are expensive, bulky and generally not portable. They are also difficult
to use as an en face view of the bleeding ulcer is often required.
For these reasons, laser photocoagulation has generally fallen out
of favor for the treatment of ulcer bleeding. The argon plasma coagulator
uses a flowing stream of argon gas as the conductor for electrocoagulation.
This method is generally effective for mucosal bleeding but may
not be effective in coagulating an eroded artery in a bleeding ulcer.
Also, as flowing gas is required, care must be taken to avoid overdistention
of the stomach during treatment.
Contact thermal probes utilize the principle of "coaptive
coagulation". First, mechanical pressure is applied to the
bleeding vessel to compress the vessel before heat or electrical
energy is applied to seal the bleeding vessel. Compression of the
blood vessel also reduces the blood flow and reduces the heat sink
effect. Multiple pulses of energy are given to coagulate the bleeding
vessel to achieve hemostasis. These methods are effective in hemostasis
but carry a potential risk of inducing bleeding when an adherent
probe is pulled off a bleeding vessel. Furthermore, contact devices
require accurate targeting of the bleeding vessel for successful
ulcer hemostasis.
Multipolar electrocoagulation devices include the BICAP.RTM. Hemostasis
Probe from ACMI Circon (300 Stillwater Avenue, Stamford, Conn. 06902)
and the Gold Probe.TM. from Microvasive (480 Pleasant Street, Watertown,
Mass. 02172). A third multipolar electrocoagulation device is the
Injector-Gold Probe.TM., also from Microvasive, which incorporates
an injection needle for use with epinephrine.
According to Dr. Joseph Leung's publication entitled "Endoscopic
Management of Peptic Ulcer Bleeding", an "ideal"
endoscopic hemostatic device should have the following properties.
It should be effective in hemostasis, safe, inexpensive, easy to
apply and portable. Thus, cost and non-portability issues associated
with laser therapy have generally made it a less favorable treatment
for ulcer hemostasis. Consequently, electrocoagulation or thermal
coagulation have largely replaced laser therapy as a more routine
treatment. Injection therapy generally has an advantage over the
above contact thermal devices in that the injection does not need
to be very accurate and can be performed through a pool of blood,
but the cost of the medication is a disadvantage.
Turning to the argon plasma coagulator, according to in the publication
"A Randomized Prospective Study of Endoscopic Hemostasis with
Argon Plasma Coagulator (APC) Compared to Gold Probe.TM. (GP) for
Bleeding GI Angiomas", Jutabha and colleagues compared the
efficacy and safety of APC and GP for hemostasis of bleeding GI
angiomas and describe the advantages and disadvantages of each type
of treatment for angioma patients. Thirty-four patients with angiomas
as the cause of acute or chronic GI bleeding, not responsive to
iron supplementation alone, were stratified by syndrome (i.e., UGI,
LGI angiomas; watermelon stomach; jejunal angiomas; radiation telangiectasia)
and randomized to treatment in a prospective study: 16 to APC and
18 to GP.
According to the publication, there were 2 major complications
of APC. While there were no significant differences between most
clinical outcomes of APC versus GP patients, investigators observed
that APC was significantly slower than GP and more difficult to
use because of several features of APC: it could not coagulate through
blood or water, smoke was common which interfered with visualization
and increased gut motility, tamponade of bleeders was not possible,
and tangential coagulation was difficult or often blind.
The differences between APC and GP were more marked with multiple
angioma syndromes. Although APC is a "no touch technique,"
the catheter was difficult to hold 2-3 mm off the mucosa, which
affords the best coagulation of a dry field. These features resulted
in 6 failures and crossovers with APC and none with GP. There were
no major disadvantages of GP except that coagulum needed to be cleaned
off the tip after treatment of multiple angiomas. The authors concluded
that for hemostasis of bleeding angiomas, both the APC and GP were
effective, but there were substantial problems with the newer APC
device, and overall the GP performed better.
In light of the above, what is needed is a endoscopic hemostatic
device which offers advantages of both the so called non-contact
and contact devices and methods without associated disadvantages.
Thus, for example, what is needed is an endoscopic hemostatic device
which is preferably portable and inexpensive. Furthermore, preferably
the device should be capable of tissue contact and tamponage associated
with coaptive coagulation to reduce the heat sink effect and facilitate
treatment of an eroded artery, but be less likely to induce bleeding
when the device is removed from a treated vessel. Furthermore, preferably
the device should be capable of coagulation through blood or water
(i.e. without contact) as well as tangential coagulation, without
generating smoke which raises possible problems of visualization,
gut motility or stomach overdistenation. Furthermore, preferably
the device should be capable of generating tissue hemostasis at
a temperature high enough to result in tissue shrinkage, but at
a temperature low enough not to necessarily create char (e.g. dried
blood) formation or produce scabs, which maybe subsequently dissolved
by digestive juices a result in rebleeding. Furthermore, preferably
the device should be capable of use on any surface of the GI tract
without regard for orientation. In other words, for example, preferably
the device may be used to treat any surface of the stomach, whether
above, below or to the side.
SUMMARY OF THE INVENTION
According to one aspect of the invention, an electrosurgical device
and methods for use are provided which comprises an electrosurgical
device outer surface and includes a probe body, at least one conductor
pair comprising a first electrode separated by a gap from a second
electrode, and means in fluid communication with the lumen of a
tube for distributing a fluid provided from the lumen of the tube
to at least a portion of the surface of the electrosurgical device.
Also according to the invention, a catheter assembly is provided
which comprises a catheter having a distal end and a lumen, and
an electrosurgical device assembled with the catheter adjacent the
distal end thereof The electrosurgical device comprises an electrosurgical
device outer surface and includes a probe body, at least one conductor
pair comprising a first electrode separated by a gap from a second
electrode, and means in fluid communication with the lumen of the
catheter for distributing a fluid provided from the lumen of the
catheter to at least a portion of the surface of the electrosurgical
device.
According to another embodiment of the invention, a catheter assembly
is provided which comprises a catheter having a distal end and a
lumen, and an electrosurgical device assembled with the catheter
adjacent the distal end thereof The electrosurgical device comprises
an electrosurgical device outer surface and includes a probe body,
at least one conductor pair comprising a first electrode separated
by a gap from a second electrode, and a fluid flow manifold located
within the probe body. The fluid flow manifold includes at least
one flow passage extending longitudinally within the probe body
and at least one flow passage lateral to the longitudinal flow passage.
The longitudinal flow passage comprises a longitudinal flow passage
fluid entrance opening in fluid communication with the lumen of
the catheter and is at least partially defined distally by an occlusion.
The lateral flow passage is in fluid communication with the longitudinal
flow passage and extends through the probe body from the longitudinal
flow passage towards the electrosurgical device outer surface.
According to another embodiment of the invention, a catheter assembly
is provided which comprises a catheter, the catheter having a distal
end and a lumen, and an electrosurgical device assembled with the
catheter adjacent the distal end thereof. The electrosurgical device
comprises an electrosurgical device outer surface and includes a
probe body, at least one conductor pair, the conductor pair comprising
a first electrode separated by a gap from a second electrode, and
means in fluid communication with the lumen of the catheter for
distributing a fluid provided from the lumen of the catheter to
at least a portion of the surface of the electrosurgical device.
According to another embodiment of the invention, a medical device
is provided which comprises a catheter tube having a distal end
and a lumen, and configured to assist in applying tamponage to a
bleeding source in a gastrointestinal tract when flexed. A catheter
tip having a catheter tip outer surface is assembled with the tube
adjacent the distal end of the tube. The catheter tip comprises
a probe body comprising an electrically insulative material, at
least one electrode pair located on the probe body which comprises
a first electrode spaced from a second electrode, and a fluid distribution
manifold to direct a fluid from inside the probe body towards the
tip outer surface. The manifold comprises a central passage within
the probe body and a plurality of lateral passages which extend
from the central passage towards the tip outer surface. An extendable
injection needle is housed within the central passage to provide
treatment to tissue.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing one embodiment of a control system
of the invention, and an electrosurgical device;
FIG. 2 is a schematic graph that describes the relationship between
RF power to tissue (P), flow rate of saline (Q), and tissue temperature
(T) when heat conduction to adjacent tissue is considered;
FIG. 2A is a schematic graph that describes the relationship between
RF power to tissue (P), flow rate of saline (Q), and tissue temperature
(T) when the heat required to warm the tissue to the peak temperature
(T) 68 is considered;
FIG. 3 is schematic graph that describes the relationship between
RF power to tissue (P), flow rate of saline (Q), and tissue temperature
(T) when heat conduction to adjacent tissue is neglected;
FIG. 4 is a graph showing the relationship of percentage saline
boiling and saline flow rate (cc/min) for an exemplary RF generator
output of 75 watts;
FIG. 5 is a schematic graph that describes the relationship of
load impedance (Z, in ohms) and generator output power (P, in watts),
for an exemplary generator output of 75 watts in a bipolar mode;
FIG. 6 is a schematic graph that describes the relationship of
time (t, in seconds) and tissue impedance (Z, in ohms) after RF
activation;
FIG. 7 is a schematic perspective view of a viewing scope with
an electrosurgical device according to one embodiment of the invention;
FIG. 8 is a schematic close-up view of the distal end portion of
the viewing scope of FIG. 7 bounded by circle A with an electrosurgical
device according to one embodiment of the invention;
FIG. 9 is a schematic close-up front perspective view of an electrosurgical
device according to one embodiment of the invention;
FIG. 10 is a schematic partially exploded close-up rear perspective
view of the electrosurgical device of FIG. 9;
FIG. 11 is a schematic close-up side view of the electrosurgical
device of FIG. 9 as part of a medical device assembly;
FIG. 12 is a schematic close-up cross-sectional view of the assembly
of FIG. 11 taken in accordance with line 12-12 of FIG. 13;
FIG. 13 is a schematic close-up front view of the electrosurgical
device of FIG. 9;
FIG. 14 is a schematic close-up rear view of the electrosurgical
device of FIG. 9 with member 51 removed;
FIG. 15 is a schematic close-up cross-sectional view of the electrosurgical
device of FIG. 9 taken in accordance with line 15-15 of FIG. 12;
FIG. 16 is a schematic close-up cross-sectional view of the electrosurgical
device of FIG. 9 taken in accordance with line 16-16 of FIG. 12;
FIG. 17 is a schematic close-up front perspective view of an electrosurgical
device according to another embodiment of the invention;
FIG. 18 is a schematic close-up cross-sectional view of the assembly
of the electrosurgical device of FIG. 17 and tube 19 taken in accordance
with line 12-12 of FIG. 13;
FIG. 19 is a schematic close-up cross-sectional view of the electrosurgical
device of FIG. 17 taken in accordance with line 19-19 of FIG. 18;
FIG. 20 is a schematic close-up front perspective view of an electrosurgical
device according to another embodiment of the invention;
FIG. 21 is a schematic close-up cross-sectional view of the assembly
of the electrosurgical device of FIG. 20 and tube 19 taken in accordance
with line 12-12 of FIG. 13;
FIG. 22 is a schematic close-up cross-sectional view of the electrosurgical
device of FIG. 20 taken in accordance with line 22-22 of FIG. 21;
FIG. 23 is a schematic close-up partial cross-sectional view of
an electrosurgical device according to another embodiment of the
invention taken in accordance with line 22-22 of FIG. 21;
FIG. 24 is a schematic close-up cross-sectional view of the assembly
of an electrosurgical device according to another embodiment of
the invention and tube 19 taken in accordance with line 12-12 of
FIG. 13;
FIG. 25 is a schematic close-up partial cross-sectional view of
an electrosurgical device according to another embodiment of the
invention taken in accordance with line 22-22 of FIG. 21;
FIG. 26 is a schematic close-up partial cross-sectional view of
an electrosurgical device according to another embodiment of the
invention taken in accordance with line 22-22 of FIG. 21;
FIG. 27 is a schematic close-up partial cross-sectional view of
an electrosurgical device according to another embodiment of the
invention taken in accordance with line 22-22 of FIG. 21;
FIG. 28 is a schematic close-up partial cross-sectional view of
an electrosurgical device according to another embodiment of the
invention taken in accordance with line 22-22 of FIG. 21;
FIG. 29 is a schematic close-up front perspective view of an electrosurgical
device according to another embodiment of the invention;
FIG. 30 is a schematic close-up cross-sectional view of the assembly
of the electrosurgical device of FIG. 29 and tube 19 taken in accordance
with line 12-12 of FIG. 13;
FIG. 31 is a schematic close-up cross-sectional view of the electrosurgical
device of FIG. 29 taken in accordance with line 31-31 of FIG. 30;
FIG. 32 is a schematic close-up front perspective view of the electrosurgical
device of FIG. 29 with instrument 64 extended;
FIG. 33 is a schematic close-up cross-sectional view of the assembly
of FIG. 30 with instrument 64 extended;
FIG. 34 is a schematic close-up front perspective view of an electrosurgical
device according to another embodiment of the invention;
FIG. 35 is a schematic close-up cross-sectional view of the assembly
of the electrosurgical device of FIG. 34 and tube 19 taken in accordance
with line 12-12 of FIG. 13;
FIG. 36 is a schematic close-up cross-sectional view of the electrosurgical
device of FIG. 34 taken in accordance with line 36-36 of FIG. 35;
FIG. 37 is a schematic close-up front perspective view of an electrosurgical
device according to another embodiment of the invention;
FIG. 38 is a schematic close-up cross-sectional view of the electrosurgical
device of FIG. 37 taken in accordance with line 38-38 of FIG. 39;
FIG. 39 is a schematic close-up cross-sectional view of the assembly
of the electrosurgical device of FIG. 37 with instrument 64 and
tube 19 taken in accordance with line 12-12 of FIG. 13;
FIG. 40 is a schematic close-up cross-sectional view of the assembly
of the electrosurgical device of FIG. 37 with instrument 73 and
tube 19 taken in accordance with line 12-12 of FIG. 13;
FIG. 41 is a schematic close-up front perspective view of an electrosurgical
device according to another embodiment of the invention;
FIG. 42 is a schematic close-up cross-sectional view of the assembly
of the electrosurgical device of FIG. 41 and tube 19 taken in accordance
with line 12-12 of FIG. 13;
FIG. 43 is a schematic close-up cross-sectional view of the electrosurgical
device of FIG. 42 taken in accordance with line 43-43 of FIG. 42;
FIG. 44 is a schematic close-up front perspective view of an electrosurgical
device according to another embodiment of the invention;
FIG. 45 is a schematic close-up rear perspective view of the electrosurgical
device of FIG. 44 with member 51 removed;
FIG. 46 is a schematic close-up cross-sectional view of the assembly
of the electrosurgical device of FIG. 44 and tube 19 taken in accordance
with line 12-12 of FIG. 13;
FIG. 47 is a schematic close-up cross-sectional view of the electrosurgical
device of FIG. 44 taken in accordance with line 47-47 of FIG. 46;
FIG. 48 is a schematic close-up front perspective view of an electrosurgical
device according to another embodiment of the invention;
FIG. 49 is a schematic close-up cross-sectional view of the assembly
of the electrosurgical device of FIG. 48 and tube 19 taken in accordance
with line 12-12 of FIG. 13;
FIG. 50 is a schematic close-up cross-sectional view of the electrosurgical
device of FIG. 48 taken in accordance with line 50-50 of FIG. 49;
FIG. 51 is a schematic close-up front perspective view of an electrosurgical
device according to another embodiment of the invention;
FIG. 52 is a schematic close-up cross-sectional view of the assembly
of the electrosurgical device of FIG. 51 and tube 19 taken in accordance
with line 12-12 of FIG. 13;
FIG. 53 is a schematic close-up cross-sectional view of the electrosurgical
device of FIG. 51 taken in accordance with line 53-53 of FIG. 52;
FIG. 54 is a schematic exploded perspective view of an assembly
of an electrosurgical device according to another embodiment of
the invention and a handle 100;
FIG. 55 is the schematic close-up up cross-sectional view of FIG.
53 shown with tissue 20 and with fluid 24;
FIG. 56 is the schematic close-up up cross-sectional view of FIG.
21 shown with tissue 20 and with fluid 24;
FIG. 57 is a schematic close-up front perspective view of an electrosurgical
device according to another embodiment of the invention;
FIG. 58 is a schematic close-up rear perspective view of the electrosurgical
device of FIG. 57 with member 51 removed;
FIG. 59 is a schematic close-up cross-sectional view of the assembly
of the electrosurgical device of FIG. 57 and tube 19 taken in accordance
with line 12-12 of FIG. 13;
FIG. 60 is a schematic close-up cross-sectional view of the electrosurgical
device of FIG. 57 taken in accordance with line 60-60 of FIG. 59;
FIG. 61 is a schematic close-up front perspective view of an electrosurgical
device according to another embodiment of the invention;
FIG. 62 is a schematic close-up rear perspective view of the electrosurgical
device of FIG. 61 with member 51 removed;
FIG. 63 is a schematic close-up cross-sectional view of the assembly
of the electrosurgical device of FIG. 61 and tube 19 taken in accordance
with line 12-12 of FIG. 13;
FIG. 64 is a schematic close-up cross-sectional view of the assembly
of the electrosurgical device of FIG. 61 and tube 19 taken at 90
degrees to line 12-12 of FIG. 13; and
FIG. 65 is a schematic close-up cross-sectional view of the electrosurgical
device of FIG. 61 taken in accordance with line 65-65 of FIG. 63.
DETAILED DESCRIPTION
Throughout the present description, like reference numerals and
letters indicate corresponding structure throughout the several
views, and such corresponding structure need not be separately discussed.
Furthermore, any particular feature(s) of a particular exemplary
embodiment may be equally applied to any other exemplary embodiment(s)
of this specification as suitable. In other words, features between
the various exemplary embodiments described herein are interchangeable
as suitable, and not exclusive.
The invention provides systems, devices and methods that preferably
improve control of tissue temperature at a tissue treatment site
during a medical procedure. The invention is particularly useful
during surgical procedures upon tissues of the body, where it is
desirable to shrink tissue, coagulate fluids (e.g. oozing blood),
and at least partially occlude lumens, vessels (e.g. lumen of blood
vessels (e.g. arteries, veins), intestines (e.g. absorbent vessels))
and airways (e.g. trachea, bronchi, bronchiole)).
The invention preferably involves the use of electrosurgical procedures,
which preferably utilize RF power and electrically conductive fluid
to treat tissue. Preferably, a desired tissue temperature range
is achieved through adjusting parameters, such as conductive fluid
flow rate, that affect the temperature at the tissue/electrode interface.
Preferably, the device achieves a desired tissue temperature utilizing
a desired percentage boiling of the conductive solution at the tissue/electrode
interface.
In one embodiment, the invention provides a control device, the
device comprising a flow rate controller that receives a signal
indicating power applied to the system, and adjusts the flow rate
of conductive fluid from a fluid source to an electrosurgical device.
The invention also contemplates a control system comprising a flow
rate controller, a measurement device that measures power applied
to the system, and a pump that provides fluid at a selected flow
rate.
The invention will be discussed generally with reference to FIG.
1. FIG. 1 shows a block diagram of one exemplary embodiment of a
system of the invention. Preferably, as shown in FIG. 1, an electrically
conductive fluid is provided from a fluid source 1, through a fluid
line 2, to a pump 3, which has an outlet fluid line 4a that is connected
as an input fluid line 4b to electrosurgical device 5. In a preferred
embodiment, the outlet fluid line 4a and the input fluid line 4b
are flexible and comprise a polymer, such as polyvinylchloride (PVC),
while the conductive fluid comprises a saline solution. More preferably,
the saline comprises sterile, and even more preferably, normal saline.
Although the description herein will specifically describe the use
of saline as the fluid, other electrically conductive fluids, as
well as non-conductive fluids, can be used in accordance with the
invention.
For example, in addition to the conductive fluid comprising physiologic
saline (also known as "normal" saline, isotonic saline
or 0.9% sodium chloride (NaCl) solution), the conductive fluid may
comprise hypertonic saline solution, hypotonic saline solution,
Ringers solution (a physiologic solution of distilled water containing
specified amounts of sodium chloride, calcium chloride, and potassium
chloride), lactated Ringer's solution (a crystalloid electrolyte
sterile solution of distilled water containing specified amounts
of calcium chloride, potassium chloride, sodium chloride, and sodium
lactate), Locke-Ringer's solution (a buffered isotonic solution
of distilled water containing specified amounts of sodium chloride,
potassium chloride, calcium chloride, sodium bicarbonate, magnesium
chloride, and dextrose), or any other electrolyte solution. In other
words, a solution that conducts electricity via an electrolyte,
a substance (salt, acid or base) that dissociates into electrically
charged ions when dissolved in a solvent, such as water, resulting
solution comprising an ionic conductor.
While a conductive fluid is preferred, as will become more apparent
with further reading of this specification, the fluid may also comprise
an electrically non-conductive fluid. The use of a non-conductive
fluid is less preferred to that of a conductive fluid as the non-conductive
fluid does not conduct electricity. However, the use of a non-conductive
fluid still provides certain advantages over the use of a dry electrode
including, for example, reduced occurrence of tissue sticking to
the electrode. Therefore, it is also within the scope of the invention
to include the use of a non-conducting fluid, such as, for example,
dionized water.
Energy to heat tissue is provided from energy source, such as an
electrical generator 6 which preferably provides RF alternating
current energy via a cable 7 to energy source output measurement
device, such as a power measurement device 8 that measures the RF
alternating current electrical power. In one exemplary embodiment,
preferably the power measurement device 8 does not turn the power
off or on, or alter the power in any way. A power switch 15 connected
to the generator 6 is preferably provided by the generator manufacturer
and is used to turn the generator 6 on and off. The power switch
15 can comprise any switch to turn the power on and off, and is
commonly provided in the form of a footswitch or other easily operated
switch, such as a switch 15a mounted on the electrosurgical device
5. The power switch 15 or 15a may also function as a manually activated
device for increasing or decreasing the rate of energy provided
from the surgical device 5. Alternatively, internal circuitry and
other components of the generator 6 may be used for automatically
increasing or decreasing the rate of energy provided from the surgical
device 5. A cable 9 preferably carries RF energy from the power
measurement device 8 to the electrosurgical device 5. Power, or
any other energy source output, is preferably measured before it
reaches the electrosurgical device 5.
For the situation where capacitation and induction effects are
negligibly small, from Ohm's law, power P, or the rate of energy
delivery (e.g. joules/sec), may be expressed by the product of current
times voltage (i.e. I.times.V), the current squared times resistance
(i.e. I.sup.2.times.R), or the voltage squared divided by the resistance
(i.e. V.sup.2/R); where the current I may be measured in amperes,
the voltage V may be measured in volts, the electrical resistance
R may be measured in ohms, and the power P may be measured in watts
(joules/sec). Given that power P is a function of current I, voltage
V, and resistance R as indicated above, it should be understood,
that a change in power P is reflective of a change in at least one
of the input variables. Thus, one may alternatively measure changes
in such input variables themselves, rather than power P directly,
with such changes in the input variables mathematically corresponding
to a changes in power P as indicated above.
As to the frequency of the RF electrical energy, it is preferably
provided within a frequency band (i.e. a continuous range of frequencies
extending between two limiting frequencies) in the range between
and including about 9 kHz (kilohertz) to 300 GHz (gigahertz). More
preferably, the RF energy is provided within a frequency band in
the range between and including about 50 kHz (kilohertz) to 50 MHz
(megahertz). Even more preferably, the RF energy is provided within
a frequency band in the range between and including about 200 kHz
(kilohertz) to 2 MHz (megahertz). Most preferably, RF energy is
provided within a frequency band in the range between and including
about 400 kHz (kilohertz) to 600 kHz (kilohertz). Further, it should
also be understood that, for any frequency band identified above,
the range of frequencies may be further narrowed in increments of
1 (one) hertz anywhere between the lower and upper limiting frequencies.
While RF electrical energy is preferred, it should be understood
that the electrical energy (i.e., energy made available by the flow
of electric charge, typically through a conductor or by self-propagating
waves) may comprise any frequency of the electromagnetic spectrum
(i.e. the entire range of radiation extending in frequency from
10.sup.23 hertz to 0 hertz) and including, but not limited to, gamma
rays, x-rays, ultraviolet radiation, visible light, infrared radiation,
microwaves, and any combinations thereof.
With respect to the use of electrical energy, heating of the tissue
is preferably performed by means of resistance heating. In other
words, increasing the temperature of the tissue as a result of electric
current flow through the tissue, with the electrical energy being
absorbed from the voltage and transformed into thermal energy (i.e.
heat) via accelerated movement of ions as a function of the tissue's
electrical resistance.
Heating with electrical energy may also be performed by means of
dielectric heating (capacitation). In other words, increasing the
temperature of the tissue through the dissipation of electrical
energy as a result of internal dielectric loss when the tissue is
placed in a varying electric field, such as a high-frequency (e.g.
microwave), alternating electromagnetic field. Dielectric loss is
the electrical energy lost as heat in the polarization process in
the presence of the applied electric field. In the case of an alternating
current field, the energy is absorbed from the alternating current
voltage and converted to heat during the polarization of the molecules.
However, it should be understood that energy provided to heat the
tissue may comprise surgical devices other than electrosurgical
devices, energy sources other than generators, energy forms other
than electrical energy and mechanisms other than resistance heating.
For example, providing thermal energy to the tissue from energy
source with a difference (e.g. higher) in temperature. Such may
be provided, for example, to the tissue from a heated device, which
heats tissue through direct contact with the energy source (conduction),
heats through contact with a flowing fluid (convection), or from
a remote heat source (radiation).
Also, for example, providing energy to the tissue may be provided
via mechanical energy which is transformed into thermal energy via
accelerated movement of the molecules, such as by mechanical vibration
provided, for example, by energy source such as a transducer containing
a piezoelectric substance (e.g., a quartz-crystal oscillator) that
converts high-frequency electric current into vibrating ultrasonic
waves which may be used by, for example, an ultrasonic surgical
device.
Also, for example, providing energy to the tissue may be provided
via radiant energy (i.e. energy which is transmitted by radiation/waves)
which is transformed into thermal energy via absorption of the radiant
energy by the tissue. Preferably the radiation/waves comprise electromagnetic
radiation/waves which include, but is not limited to, radio waves,
microwaves, infrared radiation, visible light radiation, ultraviolet
radiation, x-rays and gamma rays. More preferably, such radiant
energy comprises energy with a frequency of 3.times.10.sup.11 hertz
to 3.times.10.sup.16 hertz (i.e. the infrared, visible, and ultraviolet
frequency bands of the electromagnetic spectrum). Also preferably
the electromagnetic waves are coherent and the electromagnetic radiation
is emitted from energy source such as a laser device. A flow rate
controller 11 preferably includes a selection switch 12 that can
be set to achieve desired levels of percentage fluid boiling (for
example, 100%, 98%, 80% boiling). Preferably, the flow rate controller
11 receives an input signal 10 from the power measurement device
8 and calculates an appropriate mathematically predetermined fluid
flow rate based on percentage boiling indicated by the selection
switch 12. In a preferred embodiment, a fluid switch 13 is provided
so that the fluid system can be primed (e.g. air eliminated) before
turning the generator 6 on. The output signal 16 of the flow rate
controller 11 is preferably sent to the pump 3 motor to regulate
the flow rate of conductive fluid, and thereby provide an appropriate
fluid flow rate which corresponds to the amount of power being delivered.
In one exemplary embodiment, the invention comprises a flow rate
controller that is configured and arranged to be connected to a
source of RF power, and a source of fluid, for example, a source
of conductive fluid. The device of the invention receives information
about the level of RF power applied to an electrosurgical device,
and adjusts the flow rate of the fluid to the electrosurgical device,
thereby controlling temperature at the tissue treatment site.
In another exemplary embodiment, elements of the system are physically
included together in one electronic enclosure. One such embodiment
is shown by enclosure within the outline box 14 of FIG. 1. In the
illustrated embodiment, the pump 3, flow rate controller 11, and
power measurement device 8 are enclosed within an enclosure, and
these elements are connected through electrical connections to allow
signal 10 to pass from the power measurement device 8 to the flow
rate controller 11, and signal 16 to pass from the flow rate controller
11 to the pump 3. Other elements of a system can also be included
within one enclosure, depending upon such factors as the desired
application of the system, and the requirements of the user.
The pump 3 can be any suitable pump used in surgical procedures
to provide saline or other fluid at a desired flow rate. Preferably,
the pump 3 comprises a peristaltic pump. With a rotary peristaltic
pump, typically a fluid is conveyed within the confines of a flexible
tube by waves of contraction placed externally on the tube which
are produced mechanically, typically by rotating rollers which squeeze
the flexible tubing against a support intermittently. Alternatively,
with a linear peristaltic pump, typically a fluid is conveyed within
the confines of a flexible tube by waves of contraction placed externally
on the tube which are produced mechanically, typically by a series
of compression fingers or pads which squeeze the flexible tubing
against a support sequentially. Peristaltic pumps are generally
preferred for use as the electro-mechanical force mechanism (e.g.
rollers driven by electric motor) does not make contact the fluid,
thus reducing the likelihood of inadvertent contamination.
Alternatively, pump 3 can be a "syringe pump", with a
built-in fluid supply. With such a pump, typically a filled syringe
is located on an electromechanical force mechanism (e.g. ram driven
by electric motor) which acts on the plunger of the syringe to force
delivery of the fluid contained therein. Alternatively, the syringe
pump may comprise a double-acting syringe pump with two syringes
such that they can draw saline from a reservoir, either simultaneously
or intermittently. With a double acting syringe pump, the pumping
mechanism is generally capable of both infusion and withdrawal.
Typically, while fluid is being expelled from one syringe, the other
syringe is receiving fluid therein from a separate reservoir. In
this manner, the delivery of fluid remains continuous and uninterrupted
as the syringes function in series. Alternatively, it should be
understood that a multiple syringe pump with two syringes, or any
number of syringes, may be used in accordance with the invention.
Furthermore, fluid, such as conductive fluid, can also be provided
from an intravenous (IV) bag full of saline that flows under the
influence (i.e. force) of gravity. In such a manner, the fluid may
flow directly to the electrosurgical device 5, or first to the pump
3 located there between. Alternatively, fluid from a fluid source
such as an IV bag can be provided through an IV flow controller
that may provide a desired flow rate by adjusting the cross sectional
area of a flow orifice (e.g. lumen of the connective tubing with
the electrosurgical device) while sensing the flow rate with a sensor
such as an optical drop counter. Furthermore, fluid from a fluid
source such as an IV bag an be provided through a manually or automatically
activated device such as a flow controller, such as a roller clamp,
which also adjusts the cross sectional area of a flow orifice and
may be adjusted manually by, for example, the user of the device
in response to their visual observation (e.g. fluid boiling) at
the tissue treatment site or a pump.
Similar pumps can be used in connection with the invention, and
the illustrated embodiments are exemplary only. The precise configuration
of the pump 3 is not critical to the invention. For example, pump
3 may include other types of infusion and withdrawal pumps. Furthermore,
pump 3 may comprise pumps which may be categorized as piston pumps,
rotary vane pumps (e.g. blower, axial impeller, centrifugal impeller),
cartridge pumps and diaphragm pumps. In some embodiments, the pump
can be substituted with any type of flow controller, such as a manual
roller clamp used in conjunction with an IV bag, or combined with
the flow controller to allow the user to control the flow rate of
conductive fluid to the device. Alternatively, a valve configuration
can be substituted for pump 3.
Furthermore, similar configurations of the system can be used in
connection with the invention, and the illustrated embodiments are
exemplary only. For example, the fluid source 1 pump 3, generator
6, power measurement device 8 or flow rate controller 11, or any
other components of the system not expressly recited above, may
comprise a portion of the electrosurgical device 5. For example,
in one exemplary embodiment the fluid source may comprise a compartment
of the electrosurgical device 5 which contains fluid, as indicated
at reference character 1a. In another exemplary embodiment, the
compartment may be detachably connected to the electrosurgical device
5, such as a canister which may be attached via threaded engagement
with the device 5. In yet another exemplary embodiment, the compartment
may be configured to hold a pre-filled cartridge of fluid, rather
than the fluid directly.
Also for example, with regards to the generator, energy source,
such as a direct current (DC) battery used in conjunction with inverter
circuitry and a transformer to produce alternating current at a
particular frequency, may comprise a portion of the electrosurgical
device 5, as indicated at reference character 6a. In one embodiment
the battery element of the energy source may comprise a rechargeable
battery. In yet another exemplary embodiment, the battery element
may be detachably connected to the electrosurgical device 5, such
as for recharging. The components of the system will now be described
in further detail. From the specification, it should be clear that
any use of the terms "distal" and "proximal"
are made in reference from the user of the device, and not the patient.
The flow rate controller 11 controls the rate of flow from the
fluid source 1. Preferably, the rate of fluid flow from the fluid
source 1 is based upon the amount of RF power provided from the
generator 6 to the electrosurgical device 5. In other words, as
shown in FIG. 2, preferably there is a relationship between the
rate of fluid flow and the RF power as indicated by the X- and Y-axes
of the schematic graph. More precisely, as shown in FIG. 2, the
relationship between the rate of fluid flow and RF power may be
expressed as a direct, linear relationship. The flow rate of conductive
fluid, such as saline, interacts with the RF power and various modes
of heat transfer away from the target tissue, as described herein.
Throughout this disclosure, when the terms "boiling point
of saline", "vaporization point of saline", and variations
thereof are used, what is intended is the boiling point of the water
in the saline solution.
FIG. 2 shows a schematic graph that describes the relationship
between the flow rate of saline, RF power to tissue, and regimes
of boiling as detailed below. Based on a simple one-dimensional
lumped parameter model of the heat transfer, the peak tissue temperature
can be estimated, and once tissue temperature is estimated, it follows
directly whether it is hot enough to boil saline. P=.DELTA.T/R+.rho.c.sub..rho.Q.sub.1.DELTA.T+.rho.Q.sub.bh.sub.v
(1) where P=the total RF electrical power that is converted into
heat.
Conduction. The first term [.DELTA.T/R] in equation (1) is heat
conducted to adjacent tissue, represented as 70 in FIG. 2, where:
.DELTA.T=(T-T.sub..infin.) the difference in temperature between
the peak tissue temperature (T) and the normal temperature (T.sub..infin.)
of the body tissue (.degree. C.). Normal temperature of the body
tissue is generally 37.degree. C.; and R=Thermal resistance of surrounding
tissue, the ratio of the temperature difference to the heat flow
(.degree. C./watt).
This thermal resistance can be estimated from published data gathered
in experiments on human tissue (Phipps, J. H., "Thermometry
studies with bipolar diather my during hysterectomy," Gynaecological
Endoscopy, 3:5-7 (1994)). As described by Phipps, Kleppinger bipolar
forceps were used with an RF power of 50 watts, and the peak tissue
temperature reached 320.degree. C. For example, using the energy
balance of equation (1), and assuming all the RF heat put into tissue
is conducted away, then R can be estimated: R=.DELTA.T/P=(320-37)/50=5.7.apprxeq.6.degree.
C./watt
However, it is undesirable to allow the tissue temperature to reach
320.degree. C., since tissue will become desiccated. At a temperature
of 320.degree. C., the fluid contained in the tissue is typically
boiled away, resulting in the undesirable tissue effects described
herein. Rather, it is preferred to keep the peak tissue temperature
at no more than about 100.degree. C. to inhibit desiccation of the
tissue; Assuming that saline boils at about 100.degree. C., the
first term in equation (1) (.DELTA.T/R) is equal to (100-37)/6=10.5
watts. Thus, based on this example, the maximum amount of heat conducted
to adjacent tissue without any significant risk of tissue desiccation
is 10.5 watts.
Referring to FIG. 2, RF power to tissue is represented on the X-axis
as P (watts) and flow rate of saline (cc/min) is represented on
the Y-axis as Q. When the flow rate of saline equals zero (Q=0),
there is an "offset" RF power that shifts the origin of
the sloped lines 76, 78, and 80 to the right. This offset is the
heat conducted to adjacent tissue. For example, using the calculation
above for bipolar forceps, this offset RF power is about 10.5 watts.
If the power is increased above this level with no saline flow,
the peak tissue temperature can rise well above 100.degree. C.,
resulting in tissue desiccation from the boiling off of water in
the cells of the tissue.
Convection. The second term [.rho.c.sub..rho.Q.sub.1.DELTA.T] in
equation (1) is heat used to warm up the flow of saline without
boiling the saline, represented as 72 in FIG. 2, where: p=Density
of the saline fluid that gets hot but does not boil (approximately
1.0 gm/cm.sup.3); c.sub..rho.=Specific heat of the saline (approximately
4.1 watt-sec/gm-.degree. C.); Q.sub.1=Flow rate of the saline that
is heated (cm.sup.3/sec); and .DELTA.T=Temperature rise of the saline.
Assuming that the saline is heated to body temperature before it
gets to the electrode, and that the peak saline temperature is similar
to the peak tissue temperature, this is the same .DELTA.T as for
the conduction calculation above.
The onset of boiling can be predicted using equation (1) with the
last term on the right set to zero (no boiling) (.rho.Q.sub.bh.sub.v=0),
and solving equation (1) for Q.sub.1 leads to: Q.sub.1=[P-.DELTA.T/R]/.rho.c.sub..rho..DELTA.T
(2)
This equation defines the line shown in FIG. 2 as the line of onset
of boiling 76.
Boiling. The third term [.rho.Q.sub.bh.sub.v] in equation (1) relates
to heat that goes into converting the water in liquid saline to
water vapor, and is represented as 74 in FIG. 2, where: Q.sub.b
Flow rate of saline that boils (cm.sup.3/sec); and h.sub.v=Heat
of vaporization of saline (approximately 2,000 watt-sec/gm).
A flow rate of only 1 cc/min will absorb a significant amount of
heat if it is completely boiled, or about .rho.Q.sub.bh.sub.v=(1)
(1/60) (2,000)=33.3 watts. The heat needed to warm this flow rate
from body temperature to 100.degree. C. is much less, or .rho.c.sub..rho.Q.sub.1.DELTA.T=(1)
(4.1) (1/60) (100-37)=4.3 watts. In other words, the most significant
factor contributing to heat transfer from a wet electrode device
can be fractional boiling. The present invention recognizes this
fact and exploits it.
Fractional boiling can be described by equation (3) below:
.DELTA..times..times..rho..times..times..times..DELTA..times..times..rho..-
times..times..times. ##EQU00001##
If the ratio of Q.sub.b/Q.sub.1 is 0.50 this is the 50% boiling
line 78 shown in FIG. 2. If the ratio is 1.0 this is the 100% boiling
line 80 shown in FIG. 2.
As indicated previously in the specification, using a fluid to
couple energy to tissue inhibits such undesirable effects as sticking,
desiccation, smoke production and char formation, and that one key
factor is inhibiting tissue desiccation, which occur if the tissue
temperature exceeds 100.degree. C. and all the intracellular water
boils away, leaving the tissue extremely dry and much less electrically
conductive.
As shown in FIG. 2, one control strategy or mechanism which can
be employed for the electrosurgical device 5 is to adjust the power
P and flow rate Q such that the power P used at a corresponding
flow rate Q is equal to or less than the power P required to boil
100% of the fluid and does not exceed the power P required to boil
100% of the fluid. In other words, this control strategy targets
using the electrosurgical device 5 in the regions of FIG. 2 identified
as T<100.degree. C. and T=100.degree. C., and includes the 100%
boiling line 80. Stated another way, this control strategy targets
not using the electrosurgical device 5 only in the region of FIG.
2 identified as T>>100.degree. C.
Another control strategy that can be used for the electrosurgical
device 5 is to operate the device 5 in the region T<100.degree.
C., but at high enough temperature to shrink tissue containing Type
I collagen (e.g., walls of blood vessels, bronchi, bile ducts, etc.),
which shrinks when exposed to about 85.degree. C. for an exposure
time of 0.01 seconds, or when exposed to about 65.degree. C. for
an exposure time of 15 minutes. An exemplary target temperature/time
for tissue shrinkage is about 75.degree. C. with an exposure time
of about 1 second. As discussed herein, a determination of the high
end of the scale (i.e., when the fluid reaches 100.degree. C.) can
be made by the phase change in the fluid from liquid to vapor. However,
a determination at the low end of the scale (e.g., when the fluid
reaches, for example, 75.degree. C. for 1 second) requires a different
mechanism as the temperature of the fluid is below the boiling temperature
and no such phase change is apparent. In order to determine when
the fluid reaches a temperature that will facilitate tissue shrinkage,
for example 75.degree. C., a thermochromic material, such as a thermochromic
dye (e.g., leuco dye), may be added to the fluid. The dye can be
formulated to provide a first predetermined color to the fluid at
temperatures below a threshold temperature, such as 75.degree. C.,
then, upon heating above 75.degree. C., the dye provides a second
color, such as clear, thus turning the fluid clear (i.e. no color
or reduction in color). This color change may be gradual, incremental,
or instant. Thus, a change in the color of the fluid, from a first
color to a second color (or lack thereof) provides a visual indication
to the user of the electrosurgical device 5 as to when a threshold
fluid temperature below boiling has been achieved. Thermochromic
dyes are available, for example, from Color Change Corporation,
1740 Cortland Court, Unit A, Addison, Ill. 60101.
It is also noted that the above mechanism (i.e., a change in the
color of the fluid due to a dye) may also be used to detect when
the fluid reaches a temperature which will facilitate tissue necrosis;
this generally varies from about 60.degree. C. for an exposure time
of 0.01 seconds and decreasing to about 45.degree. C. for an exposure
time of 15 minutes. An exemplary target temperature/time for tissue
necrosis is about 55.degree. C. for an exposure time of about 1
second.
In order to reduce coagulation time, use of the electrosurgical
device 5 in the region T=100.degree. C. of FIG. 2 is preferable
to use of the electrosurgical device 5 in the region T<100.degree.
C. Consequently, as shown in FIG. 2, another control strategy which
may be employed for the electrosurgical device 5 is to adjust the
power P and flow rate Q such that the power P used at a corresponding
flow rate Q is equal to or more than the power P required to initiate
boiling of the fluid, but still less than the power P required to
boil 100% of the fluid. In other words, this control strategy targets
using the electrosurgical device 5 in the region of FIG. 2 identified
as T=100.degree. C., and includes the lines of the onset of boiling
76 and 100% boiling line 80. Stated another way, this control strategy
targets use using the electrosurgical device 5 on or between the
lines of the onset of boiling 76 and 100% boiling line 80, and not
using the electrosurgical device 5 in the regions of FIG. 2 identified
as T<100.degree. C. and T>>100.degree. C.
For consistent tissue effect, it is desirable to control the saline
flow rate so that it is always on a "line of constant % boiling"
as, for example, the line of the onset of boiling 76 or the 100%
boiling line 80 or any line of constant % boiling located in between
(e.g. 50% boiling line 78) as shown in FIG. 2. Consequently, another
control strategy that can be used for the electrosurgical device
5 is to adjust power P and flow rate Q such that the power P used
at a corresponding flow rate Q targets a line of constant % boiling.
It should be noted, from the preceding equations, that the slope
of any line of constant % boiling is known. For example, for the
line of the onset of boiling 76, the slope of the line is given
by (.rho.c.sub..rho..DELTA.T), while the slope of the 100% boiling
line 80 is given by 1/(.rho.c.sub..rho..DELTA.T+ph.sub.v). As for
the 50% boiling line 78, for example, the slope is given by 1/(.rho.c.sub..rho..DELTA.T+.rho.h.sub.v0.5).
If, upon application of the electrosurgical device 5 to the tissue,
boiling of the fluid is not detected, such indicates that the temperature
is less than 100.degree. C. as indicated in the area of FIG. 2,
and the flow rate Q must be decreased to initiate boiling. The flow
rate Q may then decreased until boiling of the fluid is first detected,
at which time the line of the onset of boiling 76 is transgressed
and the point of transgression on the line 76 is determined. From
the determination of a point on the line of the onset of boiling
76 for a particular power P and flow rate Q, and the known slope
of the line 76 as outlined above (i.e. 1/.rho.c.sub..rho..DELTA.T),
it is also possible to determine the heat conducted to adjacent
tissue 70.
Conversely, if upon application of the electrosurgical device 5
to the tissue, boiling of the fluid is detected, such indicates
that the temperature is approximately equal to 100.degree. C. as
indicated in the areas of FIG. 2, and the flow rate Q must be increased
to reduce boiling until boiling stops, at which time the line of
the onset of boiling 76 is transgressed and the point of transgression
on the line 76 determined. As with above, from the determination
of a point on the line of the onset of boiling 76 for a particular
power P and flow rate Q, and the known slope of the line 76, it
is also possible to determine the heat conducted to adjacent tissue
70.
With regards to the detection of boiling of the fluid, such may
be physically detected by the user (e.g. visually by the naked eye)
of the electrosurgical device 5 in the form of either bubbles or
steam evolving from the fluid coupling at the electrode/tissue interface.
Alternatively, such a phase change (i.e. from liquid to vapor or
vice-versa) may be measured by a sensor which preferably senses
either an absolute change (e.g. existence or non-existence of boiling
with binary response such as yes or no) or a change in a physical
quantity or intensity and converts the change into a useful input
signal for an information-gathering system. For example, the phase
change associated with the onset of boiling may be detected by a
pressure sensor, such as a pressure transducer, located on the electrosurgical
device 5. Alternatively, the phase change associated with the onset
of boiling may be detected by a temperature sensor, such as a thermistor
or thermocouple, located on the electrosurgical device 5, such as
adjacent to the electrode. Also alternatively, the phase change
associated with the onset of boiling may be detected by a change
in the electric properties of the fluid itself. For example, a change
in the electrical resistance of the fluid may be detected by an
ohm meter; a change in the amperage may be measured by an amp meter;
as change in the voltage may be detected by a volt meter; and a
change in the power may be determined by a power meter.
Yet another control strategy which may be employed for the electrosurgical
device 5 is to eliminate the heat conduction term of equation (1)
(i.e. .DELTA.T/R). Since the amount of heat conducted away to adjacent
tissue can be difficult to precisely predict, as it may vary, for
example, by tissue type, it may be preferable, from a control point
of view, to assume the worst case situation of zero heat conduction,
and provide enough saline so that if necessary, all the RF power
could be used to heat up and boil the saline, thus providing that
the peak tissue temperature will not go over 100.degree. C. a significant
amount. This situation is shown in the schematic graph of FIG. 3.
Stated another way, if the heat conducted to adjacent tissue 70
is overestimated, the power P required to intersect the 100% boiling
line 80 will, in turn, be overestimated and the 100% boiling line
80 will be transgressed into the T>>100.degree. C. region
of FIG. 2, which is undesirable as established above. Thus, assuming
the worse case situation of zero heat conduction provides a "safety
factor" to avoid transgressing the 100% boiling line 80. Assuming
heat conduction to adjacent tissue 70 to be zero also provides the
advantage of eliminating the only term from equation (1) which is
tissue dependent, i.e., depends on tissue type. Thus, provided .rho.,
c.sub..rho., .DELTA.T, and h.sub.v are known as indicated above,
the equation of the line for any line of constant % boiling is known.
Thus, for example, the 98% boiling line, 80% boiling line, etc.
can be determined in response to a corresponding input from the
selection switch 12. In order to promote flexibility, it should
be understood that the input from the selection switch preferably
may comprise any percentage of boiling. Preferably the percentage
of boiling may be selected in single percent increments (i.e. 100%,
99%, 98%, etc.).
Upon determination of the line of the onset of boiling 76, the
100% boiling line 80 or any line of constant % boiling there between,
it is generally desirable to control the flow rate Q so that it
is always on a particular line of constant % boiling for consistent
tissue effect. In such a situation, the flow rate controller 11
will adjust the flow rate Q of the fluid to reflect changes in power
P provided by the generator 6, as discussed in greater detail below.
For such a use the flow rate controller may be set in a line of
constant boiling mode, upon which the % boiling is then correspondingly
selected.
As indicated above, it is desirable to control the saline flow
rate Q so that it is always on a line of constant % boiling for
consistent tissue effect. However, the preferred line of constant
% boiling may vary based on the type of electrosurgical device 5.
For example, if the device is a monopolar stasis device and shunting
through saline is not an issue, then it can be preferable to operate
close to or directly on, but not over the line of the onset of boiling,
such as 76a in FIG. 3. This preferably keeps tissue as hot as possible
without causing desiccation.
Alternatively, if the device has coaptive bipolar opposing jaws
and shunting of electrical energy from one jaw to the other jaw
through excess saline is an issue, then it can be preferable to
operate along a line of constant boiling, such as line 78a in FIG.
3, the 50% line. This simple proportional control will have the
flow rate determined by equation (4), where K is the proportionality
constant: Q.sub.1=K.times.P (4)
In essence, when power P goes up, the flow rate Q will be proportionately
increased. Conversely, when power P goes down, the flow rate Q will
be proportionately decreased.
The proportionality constant K is primarily dependent on the fraction
of saline that boils, as shown in equation (5), which is equation
(3) solved for K after eliminating P using equation (4), and neglecting
the conduction term (.DELTA.T/R):
.rho..times..times..times..DELTA..times..times..rho..times..times..times.
##EQU00002##
Thus, the present invention provides a method of controlling boiling
of fluid, such as a conductive fluid, at the tissue/electrode interface.
In a preferred embodiment, this provides a method of treating tissue
without use of tissue sensors, such as temperature or impedance
sensors. Preferably, the invention can control boiling of conductive
fluid at the tissue/electrode interface and thereby control tissue
temperature without the use of feedback loops.
In describing the control strategy of the present invention described
thus far, focus has been drawn to a steady state condition. However,
the heat required to warm the tissue to the peak temperature (T)
may be incorporated into equation (1) as follows: P=.DELTA.T/R+.rho.c.sub..rho.Q.sub.1.DELTA.T+.rho.Q.sub.bh.sub.v+.rho.c.s-
ub..rho.V.DELTA.T/.DELTA.t (6) where .rho.c.sub..rho.V.DELTA.T/.DELTA.t
represents the heat required to warm the tissue to the peak temperature
(T) 68 and where: .rho.=Density of the saline fluid that gets hot
but does not boil (approximately 1.0 gm/cm.sup.3); c.sub..rho.=Specific
heat of the saline (approximately 4.1 watt-sec/gm-.degree. C.);
V=Volume of treated tissue .DELTA.T=(T-T.sub..infin.) the difference
in temperature between the peak tissue temperature (T) and the normal
temperature (T.sub..infin.) of the body tissue (.degree. C.). Normal
temperature of the body tissue is generally 37.degree. C.; and .DELTA.t=(t-t.sub..infin.)
the difference in time to achieve peak tissue temperature (T) and
the normal temperature (T.sub..infin.) of the body tissue (.degree.
C.).
The inclusion of the heat required to warm the tissue to the peak
temperature (T) in the control strategy is graphically represented
at 68 in FIG. 2A. With respect to the control strategy, the effects
of the heat required to warm the tissue to the peak temperature
(T) 68 should be taken into account before flow rate Q adjustment
being undertaken to detect the location of the line of onset of
boiling 76. In other words, the flow rate Q should not be decreased
in response to a lack of boiling before at least a quasi-steady
state has been achieved as the location of the line of onset of
boiling 76 will continue to move during the transitory period. Otherwise,
if the flow rate Q is decreased during the transitory period, it
may be possible to decrease the flow Q to a point past the line
of onset of boiling 76 and continue past the 100% boiling line 80
which is undesirable. In other words, as temperature (T) is approached
the heat 68 diminishes towards zero such that the lines of constant
boiling shift to the left towards the Y-axis.
FIG. 4 shows an exemplary graph of flow rate Q versus % boiling
for a situation where the RF power P is 75 watts. The percent boiling
is represented on the X-axis, and the saline flow rate Q (cc/min)
is represented on the Y-axis. According to this example, at 100%
boiling the most desirable predetermined saline flow rate Q is 2
cc/min. Also according to this example, flow rate Q versus % boiling
at the remaining points of the graft illustrates a non-linear relationship
as follows:
TABLE-US-00001 TABLE 1 % Boiling and Flow Rate Q (cc/min) at RF
Power P of 75 watts 0% 17.4 10% 9.8 20% 6.8 30% 5.2 40% 4.3 50%
3.6 60% 3.1 70% 2.7 80% 2.4 90% 2.2 100% 2.0
Typical RF generators used in the field have a power selector switch
to 300 watts of power, and on occasion some have been found to be
selectable up to 400 watts of power. In conformance with the above
methodology, at 0% boiling with a corresponding power of 300 watts,
the calculated flow rate Q is 69.7 cc/min and with a corresponding
power of 400 watts the calculated flow rate Q is 92.9 cc/min. Thus,
when used with typical RF generators in the field, a fluid flow
rate Q of about 100 cc/min or less with the present invention is
expected to suffice for the vast majority of applications.
As discussed herein, RF energy delivery to tissue can be unpredictable
and vary with time, even though the generator has been "set"
to a fixed wattage. The schematic graph of FIG. 5 shows the general
trends of the output curve of a typical general-purpose generator,
with the output power changing as load (tissue plus cables) impedance
Z changes. Load impedance Z (in ohms) is represented on the X-axis,
and generator output power P (in watts) is represented on the Y-axis.
In the illustrated embodiment, the electrosurgical power (RF) is
set to 75 watts in a bipolar mode. As shown in the figure, the power
will remain constant as it was set as long as the impedance Z stays
between two cut-offs, low and high, of impedance, that is, for example,
between 50 ohms and 300 ohms in the illustrated embodiment. Below
load impedance Z of 50 ohms, the power P will decrease, as shown
by the low impedance ramp 82a. Above load impedance Z of 300 ohms,
the power P will decrease, as shown by the high impedance ramp 82b.
Of particular interest to saline-enhanced electrosurgery is the
low impedance cut-off (low impedance ramp 82a), where power starts
to ramp down as impedance Z drops further. This change in output
is invisible to the user of the generator and not evident when the
generator is in use, such as in an operating room.
FIG. 6 shows the general trend of how tissue impedance generally
changes with time for saline-enhanced electrosurgery. As tissue
heats up, the temperature coefficient of the tissue and saline in
the cells is such that the tissue impedance decreases until a steady-state
temperature is reached upon which time the impedance remains constant.
Thus, as tissue heats up, the load impedance Z decreases, potentially
approaching the impedance Z cut-off of 50 ohms. If tissue is sufficiently
heated, such that the low impedance cut-off is passed, the power
P decreases along the lines of the low impedance ramp 82a of FIG.
5.
Combining the effects shown in FIG. 5 and FIG. 6, it becomes clear
that when using a general-purpose generator set to a "fixed"
power, the actual power delivered can change dramatically over time
as tissue heats up and impedance drops. Looking at FIG. 5, if the
impedance Z drops from 100 to 75 ohms over time, the power output
would not change because the curve is "flat" in that region
of impedances. If, however, the impedance Z drops from 75 to 30
ohms one would transgress the low impedance cut-off and "turn
the corner" onto the low impedance ramp 82a portion of the
curve and the power output would decrease dramatically.
According to one exemplary embodiment of the invention, the control
device, such as flow rate controller 11, receives a signal indicating
the drop in actual power delivered to the tissue and adjusts the
flow rate Q of saline to maintain the tissue/electrode interface
at a desired temperature. In a preferred embodiment, the drop in
actual power P delivered is sensed by the power measurement device
8 (shown in FIG. 1), and the flow rate Q of saline is decreased
by the flow rate controller 11 (also shown in FIG. 1). Preferably,
this reduction in saline flow rate Q allows the tissue temperature
to stay as hot as possible without desiccation. If the control device
was not in operation and the flow rate Q allowed to remain higher,
the tissue would be over-cooled at the lower power input. This would
result in decreasing the temperature of the tissue at the treatment
site.
The flow rate controller 11 of FIG. 1 can be a simple "hard-wired"
analog or digital device that requires no programming by the user
or the manufacturer. The flow rate controller 11 can alternatively
include a processor, with or without a storage medium, in which
the determination procedure is performed by software, hardware,
or a combination thereof. In another embodiment, the flow rate controller
11 can include semi-programmable hardware configured, for example,
using a hardware descriptive language, such as Verilog. In another
embodiment, the flow rate controller 11 of FIG. 1 is a computer,
microprocessor-driven controller with software embedded. In yet
another embodiment, the flow rate controller 11 can include additional
features, such as a delay mechanism, such as a timer, to automatically
keep the saline flow on for several seconds after the RF is turned
off to provide a post-coagulation cooling of the tissue or "quench,"
which can increase the strength of the tissue seal. Also, in another
embodiment, the flow rate controller 11 can include a delay mechanism,
such as a timer, to automatically turn on the saline flow several
seconds before the RF is turned on to inhibit the possibility of
undesirable effects as sticking, desiccation, smoke production and
char formation. Also in another embodiment, the flow rate controller
11 can include a low level flow standby mechanism, such as a valve,
which continues the saline flow at a standby flow level (which prevents
the flow rate from going to zero when the RF power is turned off)
below the surgical flow level ordinarily encountered during use
of the electrosurgical device 5.
An exemplary electrosurgical device of the present invention which
may be used in conjunction with the system of the present invention
is shown at reference character 5a in FIG. 9, and more particularly
in FIGS. 7-16. While various electrosurgical devices of the present
invention are described with reference to use with the remainder
of the system of the invention, it should be understood that the
description of the combination is for purposes of illustrating the
remainder of the system of the invention only. Consequently, it
should be understood that the electrosurgical devices of the present
invention can be used alone, or in conjunction with the remainder
of the system of the invention, or that a wide variety of electrosurgical
devices can be used in connection with the remainder of the system
of the invention.
As shown in FIGS. 7 and 8, electrosurgical device 5a is preferably
used in conjunction with a viewing scope, shown as an endoscope
as illustrated at reference character 17, during a minimally invasive
procedure such flexible endoscopic gastrointestinal surgery. The
endoscope 17 preferably comprises an elongated flexible shaft portion
17a, though device 5a may be used with rigid shaft viewing scopes,
for example, during laparoscopic surgery.
Endoscope 17 also comprises a proximal portion 17b separated from
a distal portion 17c by shaft portion 17a. Proximal portion 17b
of endoscope 17 preferably comprises a control head portion 17d.
Control head portion 17d preferably comprises a tissue treatment
site viewer 17e and one or more directional control knobs 17f and
17g to control the movement of the flexible distal portion 17c of
flexible shaft 17a. Control knob 17f preferably comprises a right/left
angulation control knob while control knob 17g preferably comprises
an up/down angulation control knob.
As shown in FIG. 8, flexible shaft 17a houses at least one device
channel 17h through which surgical device 5a may be passed. Also
as shown, flexible shaft 17a also preferably contains at least one
viewing channel 17i to enable viewing through the distal portion
17c. Flexible shaft 17a also preferably contains at least one fluid
flow channel 17j for providing liquid (e.g. water) or gas (e.g.
air) to a tissue treatment site. Also preferably, electrosurgical
device 5a is configured to extend from the distal end portion 17c,
and more preferably, the distal end surface 17k of endoscope 17,
as shown in FIG. 8.
As shown in FIGS. 11 and 12, electrosurgical device 5a is preferably
assembled (e.g. mechanically connected via press-fit, mechanical
connector, welded, adhesively bonded) adjacent the distal end 18
of a long, hollow, tube 19 to preferably form a medical device assembly.
Tube 19 is preferably self-supporting and flexible, and more preferably
comprises a catheter which may be flexed to apply tamponade (e.g.
compressive force) through the electrosurgical device 5a to a bleeding
source in the gastrointestinal tract Electrosurgical device 5a,
in combination with a catheters, may be referred to as a catheter
assembly.
As best shown in FIGS. 10 and 12, electrosurgical device 5a is
also preferably electrically connected to the conductors 38a, 38b
of insulated electrical wires 21a, 21b, respectively, which have
been passed through lumen 23 of tube 19 as branches of cable 9 which
is connected to generator 6. However, in alternative embodiments,
the tube 19 may incorporate the conductors 38a, 38b of wires 21a,
21b in the tube wall (in essence creating a multi-lumen tube comprising
three lumens where two of the lumens are occupied exclusively by
the conductors 38a, 38b of wires 21a, 21b) to reduce the complexity
of items being passed down lumen 23. Thereafter, electrosurgical
device 5a along with the flexible tube 19 and wires 21a, 21b contained
therein may enter channel entrance opening 171 of device channel
17h and are thereafter passed through and along at least a portion
of the length of device channel 17h until exiting from channel exit
opening 17m.
As shown throughout FIGS. 9-16, and particularly FIGS. 12 and 15,
electrosurgical device 5a comprises a probe body 26. Probe body
26 is preferably sized to pass from entrance 171 to the exit 17m
of device channel 17h of scope 17. Probe body 26 may comprise a
solid, electrically non-conductive, insulative material impervious
to the flow of fluid 24 therethrough including, but not limited
to, ceramic or polymer materials. Examples of non-conductive polymer
materials include, but are not limited to, polyamide (a/k/a nylon),
polyphthalamide (PPA), polyamideimide (PAI), polyetherimide (PEI),
polyetheretherketone (PEEK), polyphenylenesulfide (PPS), polysulfone
(PSO), polyethersulfone (PES), syndiotactic polystyrene (SPS), polyimide
(PI) or any other non-conductive polymer, thermoplastic or thermoset.
Probe body 26 may also comprise a liquid crystal polymer and, more
particularly, an aromatic liquid crystal polyester which is reinforced
with glass fiber, such as Vectra.RTM. A130 from Ticona, 90 Morris
Avenue, Summit, N.J. 07901-3914. Where probe body 26 comprises a
ceramic, it may comprise a machinable ceramic material such as sold
under the tradename MACOR. In other embodiments, the non-conductive
material of the probe body 26 may be coated with a non-conductive,
lubricating or non-stick coating, such as polytetrafluoroethylene
(PTFE).
As shown throughout FIGS. 9-16, electrosurgical device 5a is greatly
enlarged since, for example, in one exemplary embodiment the cross-sectional
dimension of device 5a, specifically its diameter, is about 7 French
(about 2.4 mm or 0.095 inches). In another embodiment, the cross-sectional
dimension of electrosurgical device 5a may be about 10 French (about
3.2 mm or 0.126 inches). In still other embodiments, electrosurgical
device 5a may be configured with any cross-sectional dimension suitable
to pass through the working channel of a viewing scope or of a trocar
(also known as a cannula) where such a device is required.
As shown in FIGS. 9-12, for interacting with tissue, electrosurgical
device 5a and, in particular, probe body 26, preferably comprise
a generally cylindrical shape 32 with the distal end portion of
the electrosurgical device 5a and probe body 26 preferably comprising
a generally domed, hemispherical shape 67, such as that of a semi-circle,
which provides a smooth, blunt contour outer surface.
As best shown in FIG. 12, electrosurgical device 5a preferably
comprises a fluid flow manifold 40 located within probe body 26.
Manifold 40 preferably comprises a discrete, rectilinear, longitudinally
directed, central fluid flow passage 41, preferably located on-center
about longitudinal axis 31 of electrosurgical device 5a. For device
5a, central flow passage 41 preferably extends between proximal
end 35 and distal end 27 of electrosurgical device 5a through probe
body 26 and has a central flow passage fluid entrance opening 42
located adjacent the proximal end 35 of probe body 26. As shown
in FIG. 12, central flow passage 41 preferably extends into and
is fluidly coupled with lumen 23 of flexible tube 19.
As best shown in FIGS. 12, 15 and 16, manifold 40 preferably comprises
at least one discrete, rectilinear, lateral fluid flow passage 43
which is fluidly coupled to central fluid flow passage 41. As shown,
preferably manifold 40 comprises a plurality of discrete, rectilinear,
lateral fluid flow passages 43a, 43b which are defined and spaced
both longitudinally along and circumferentially around the probe
body 26 and central fluid flow passage 41. More preferably the lateral
fluid flow passages 43a, 43b are defined and spaced from proximal
end 35 of electrosurgical device 5a through probe body 26 to the
distal end 27 of electrosurgical device 5a through probe body 26.
Also as best shown in FIGS. 15 and 16, for device 5a lateral fluid
flow passages 43a, 43b preferably each have a cross-sectional dimension,
more specifically diameter, and corresponding cross-sectional area,
less than the portion of central fluid flow passage 41 from which
fluid 24 is provided. Also, as best shown in FIGS. 12, 15 and 16,
the lateral fluid flow passages 43a, 43b which preferably extend
through the cylindrical portion 32 of probe body 26 are preferably
formed substantially at a right angle (e.g. within about 10 degrees
of a right angle) to the central fluid flow passage 41, both longitudinally
and circumferentially. Also as shown in FIGS. 12, 15 and 16, the
lateral fluid flow passages 43a, 43b are preferably formed substantially
at a right angle to the outer tissue interacting/treating surfaces
28, 50 of the electrosurgical device 5a.
Preferably, lateral fluid flow passages 43a, 43b extend from central
fluid flow passage 41 to lateral flow passage fluid exit openings
44a, 44b located on surfaces of electrosurgical device 5a configured
for interacting with and treating tissue. As shown in FIGS. 12,
15 and 16, lateral flow passage fluid exit openings 44a, 44b are
located on exposed outer surface 28 of probe body 26, or an exposed
outer surface 50 of electrode 29a-c, 30a-c, which are discussed
in greater detail later in this specification. More preferably,
lateral fluid flow passages 43a, 43b preferably are configured to
extend from central fluid flow passage 41 to lateral flow passage
fluid exit openings 44a, 44b located on the outer surface 28 of
probe body 26 and outer surface 50 of electrodes 29a-c, 30a-c, respectively,
such that lateral flow passages 43a, 43b and associated fluid exit
openings 44a, 44b are defined and spaced both longitudinally along
and circumferentially around the outer surfaces 28 an 50 of electrosurgical
device 5a, preferably between proximal end 35 of electrosurgical
device 5a and the distal end 27 of electrosurgical device 5a and
probe body 26.
As best shown in FIGS. 12, 15 and 16, central flow passage 41 may
be lined by a liner 45, preferably comprising a non-corrosive, impervious
(to fluid 24), metal tube (e.g. stainless steel tubing) located
within a through bore 46 of probe body 26 which extends from proximal
end 35 to distal end 27 of electrosurgical device 5a and probe body
26. Also as best shown in FIGS. 12, 15 and 16, preferably the outer
wall surface of liner 45 contacts the inner surface of bore 46 of
probe body 26 and discrete lateral fluid flow passages 43a, 43b
extend through the wall thereof. Alternatively, liner 45 may comprise
a cylindrical coil spring with the lateral openings provided between
the coils of the spring.
As best shown in FIG. 12, distal wall section 25 of liner 45 adjacent
distal end 27 of the electrosurgical device 5a and probe body 26
partially defines the distal end of the wide proximal portion 41a
of the central flow passage 41 (with the proximal end of the distal
narrow portion 41b of the central flow passage 41 defining the remainder
of the distal end of the wide portion 41a of the central flow passage
41 in this embodiment). Distal wall section 25 of liner 45 also
narrows the central flow passage 41 from wide portion 41a to narrow
portion 41b and defines a narrow central fluid passage exit opening
62. As shown, in this manner, preferably, the distal portion of
the central flow passage 41 comprises a counterbore configuration.
In other words, two adjacent circular openings about the same axis,
but of different diameter. More particularly, wide portion 41a and
narrow portion 41b of central flow passage 41 preferably comprise
the configuration of a counterbore adjacent the distal end 27 of
electrosurgical device 5a. During use of electrosurgical device
5a, the distal wall section 25 inhibits fluid flow from wide portion
41a through the narrow portion 41b of the central flow passage 41.
In other words, distal wall 25 inhibits fluid 24 from exiting from
the central fluid passage exit opening 62 as compared to a situation
where distal wall 25 would not be used and the central flow passage
41 only would consist of wide portion 41a. In the above manner,
at least a portion of the distal end of the central flow passage
41 is defined by an occlusion (i.e. wall section 25) formed by a
portion of the electrosurgical device 5a.
More preferably, wall section 25 substantially occludes and inhibits
fluid 24 from exiting from the central flow passage exit opening
62. Throughout this specification, occlusion of central flow passage
41 and the corresponding inhibiting of flow from exiting from the
central fluid passage exit opening 62 of the central flow passage
41 can be considered substantial when the occlusion and corresponding
inhibiting of flow results in increased flow from the lateral flow
passages 43a, 43b. In other words, the occlusion functions as a
fluid flow diverter and redirects fluid coming in contact therewith
from flowing parallel with the longitudinal axis 31 of central flow
passage 41 to flowing radially from the longitudinal axis 31 through
lateral flow passages 43a, 43b.
As best shown in FIGS. 12, 15 and 16, preferably the probe body
26 has an outer surface 52 on which at least a portion of one energy
providing member is located, overlies and is conneted. As shown
in FIGS. 9 and 10, the energy providing member preferably comprises
a pair of electrical conductors 29, 30 which are respectively electrically
connected to insulated wires 21a, 21b which are ultimately connected
to generator 6. Conductors 29, 30 preferably comprise an electrically
conductive metal, which is preferably non-corrosive, such as stainless
steel or titanium.
The conductors 29, 30 are preferably configured to provide energy
to tissue for hemostatic therapy and/or for tissue treatment of
the wall of an anatomical tube. Each conductor 29, 30 may be branched
into, for example, additional sub-conductors, such as comprising
three elongated longitudinally directed strip electrodes 29a, 29b,
29c and 30a, 30b, 30c which will provide energy to treat tissue.
As shown, the electrodes may be aligned generally parallel with
the longitudinal axis 31 on the peripheral surface of the probe
body 26 (comprising exposed probe body surfaces 28 and covered probe
body surfaces 52) and are preferably angularly uniformly distributed,
in this embodiment at angular intervals of 60 degrees. The electrodes
29a-c, 30a-c of conductors 29 and 30 are respectively successively
spaced from each other by gaps, G. In one embodiment, the gaps G
are generally at least about twice the widths W of the electrodes
at the cylindrical portion 32 of the probe body 26. For a probe
body 26 of a 2.4 mm diameter, the gaps G are about 0.8 mm and the
widths W are about 0.4 mm. Generally, the wider the gap G between
the electrodes the deeper the effect on tissue being treated.
Preferably, the electrodes 29a-c, 30a-c are provided alternating
electrical current, so that the electrodes alternate polarity between
positive and negative charges, and adjacent electrodes comprises
opposite polarities at any given time to create an electrical field
with current flow from the positive to negative charge. In other
words, for example, preferably while electrodes 29a-c comprise a
first polarity (e.g. positive), electrodes 30a-c comprise a second
opposite polarity (e.g. negative). In the above manner, the plurality
of uniformly distributed opposite electrode pairs formed around
the longitudinal axis 31 create one or more bipolar electrical circuits,
with the number of electrode poles generally equal to the number
of circuits. For example, with the six electrode poles described
above, an electrical array which extends circumferentially around
longitudinal axis 31 and device 5a comprising six bipolar circuits
is created between adjacent successive poles as shown by electrical
field lines 57a-f in FIG. 13.
Conductors 29, 30, including electrodes 29a-c, 30a-c may comprise
preformed metal which is then placed on probe body 26, or formed-in-place
metal which comprises a metallic compound which is formed-in-place
on the probe body 26, typically via painting or spraying. In one
particular embodiment, conductors 29, 30 and electrodes 29a-c, 30a-c
may be formed by first applying metal completely to the outer surfaces
28 and 52 of probe body 26 (such as by dip coating the outer surface
in a liquid metal bath) then removing metal in excess of the conductors
29, 30 and electrodes 29a-c, 30a-c from the surface 28 to define
the conductors 29, 30 and electrodes 29a-c, 30a-c, such as by the
use of a laser.
Also as shown in FIGS. 9 and 10, where elongated, longitudinally
directed electrodes are utilized (e.g. from the proximal end 35
to the distal end 27 of the electrosurgical device 5a and probe
body 26), such as with electrosurgical device 5a, preferably at
least three sets of opposite electrode poles are provided. In this
manner, at least bipolar, and frequently greater, polar tissue contact
and electrocoagulation can be achieved substantially independent
of the orientation of the probe body 26 relative to the tissue treatment
site. This is advantageous when the device 5a is used through endoscope
17 so that front end use (e.g. domed portion 67), sideways use (e.g.
cylindrical portion 32) or oblique use (e.g. combination of domed
portion 67 and cylindrical portion 32) of the electrosurgical device
5a results in at least a bipolar contact with the tissue treatment
site.
As best shown in FIGS. 10 and 14, electrodes 29a-c of conductor
29 are preferably electrically coupled to each other at the proximal
end 35 of the probe body 26. Preferably, electrodes 29a-c of conductor
29 are electrically coupled via a conductor 29 which comprises an
electrically conductive radial band, preferably located on a radially
recessed shoulder 34 of probe body 26 located at the proximal end
35 of probe body 26. The electrical coupling between electrodes
29a-c and conductor 29 is preferably made via radially displaced
localized conductive tabs 36a-c. In turn, conductor 38b of insulated
wire 21b is preferably connected to band preferably in a notch 37
formed in the band and in shoulder 34, where notch 37 is sized to
receive conductor 38b of wire 21b. Conductor 38b of insulated wire
21b is preferably connected to a surface 39 of notch 37 via an electrical
connector comprising solder (e.g. silver) from soldering.
As best shown in FIGS. 9 and 12, electrodes 30a-c of conductor
30 are preferably electrically coupled to each other at the distal
end 27 of the electrosurgical device 5a and probe body 26. Preferably,
electrodes 30a-c of conductor 30 are electrically coupled via a
conductor 30 comprising an electrically conductive hub preferably
located at the distal end 27 of the electrosurgical device 5a and
probe body 26. A wall section 47 of the conductor 30 overlying wall
section 25 of liner 45 may also function an occlusion which either
partially defines the distal portion of the central flow passage
41 (i.e. where central flow passage 41 comprises a narrow portion
41b and a central fluid passage exit opening 62) or completely defines
the distal end of the central flow passage 41 (i.e. where the central
flow passage does not continue through the wall section 47 of conductor
30), particularly when liner 45 is not occluded at its distal end
(i.e. does not include wall section 25).
Conductor 30 is preferably electrically coupled to hollow conductive
metal liner 45 to which, in turn, conductor 38a of insulated wire
21a is preferably connected to a surface of hollow metal liner 45
at the proximal end 35 of probe body 26 via an electrical connector
comprising solder (e.g. silver) from soldering. Alternatively where,
for example, liner 45 is not utilized, conductor 38a of insulated
wire 21a may be connected to an inner surface 49 of conductor 30.
As shown in FIGS. 9 and 16, preferably the plurality of lateral
flow passages 43a which extend through probe body 26 to fluid exit
openings 44a are defined and spaced along the outer surface 28 of
probe body 26 between at least one pair of adjacent electrodes.
As shown, preferably the plurality of lateral flow passage fluid
exit openings 44a are configured to form both longitudinal and circumferential
straight rows, and are preferably uniformly spaced relative to one
another. Also, preferably lateral flow passages 43a are configured
to distribute fluid flow exiting from fluid exit openings 44a substantially
uniformly. Lateral flow passages 43a of this exemplary embodiment
preferably have a cross-sectional dimension (e.g. diameter) in the
range between and including about 0.11 mm to 2 mm and more preferably
have a diameter in the range between and including about 0.15 mm
to 0.2 mm.
Also as shown in FIGS. 9 and 15, preferably the plurality of lateral
flow passages 43b which extend through probe body 26 and at least
one electrode 29a-c, 30a-c to fluid exit openings 44b are defined
and spaced along the outer surface 50 of electrodes 29a-c, 30a-c.
As shown, preferably the plurality of lateral flow passage fluid
exit openings 44b are configured to form both longitudinal and circumferential
straight rows, and are preferably uniformly spaced relative to one
another. Also, preferably lateral flow passages 43b are configured
to distribute fluid flow exiting from fluid exit openings 44b substantially
uniformly. Lateral flow passages 44b of this exemplary embodiment
preferably have a cross-sectional dimension (e.g. diameter) in the
range between and including about 0.1 mm to 2 mm and more preferably
have a diameter in the range between and including about 0.15 mm
to 0.2 mm.
As best shown in FIG. 10, electrical device 5a preferably further
comprises a member 51 which comprises a gasket portion 51a configured
to electrically insulate conductors 38a, 38b from one another and
inhibit a short circuit (i.e. a low resistance, alternate path through
which current will flow, often resulting in damage, rather than
through the load circuit) from forming between conductors of different
electrical potential (e.g. conductors 29/38b with conductors 30/38a)
in the presence of electrically conductive fluid, which would cause
electrical current to flow between conductors (e.g. 29/38b and 30/38a)
prior to the current reaching electrodes 29a-c and 30a-c, thus bypassing
or detouring away from the electrodes. Member 51 preferably comprises
an insulative flexible polymer material, such as an elastomer and,
in this embodiment, preferably comprises the geometry of a thin,
flat circular member, such as that of a washer. As shown in FIG.
10, gasket portion 51a surrounds aperture 51b through which wire
21b extends. Thereafter, gasket portion 51a preferably forms a gasket
with the insulator of wire 21b to inhibits fluid 24 from lumen 23
of tube 19 from contacting conductors 38b and 29.
Member 51 also preferably includes a second gasket portion 51c
which surrounds aperture 51d through which liner 45 extends and
thereafter forms a gasket with the outer surface of liner 45 to
also inhibit fluid 24 from lumen 23 of tube 19 from contacting conductor
38b or 29.
In other embodiments, electrical device 5a may further comprise
a sensor, such as probe body 26 itself, for sensing, for example,
temperature, pressure or saline impedance sensor for sensing the
phase change associated with the onset of boiling, or which may
be located in or on probe body 26, adjacent an electrode and/or
the tissue.
As best shown in FIGS. 12, 15 and 16, probe body 26 preferably
comprises a circular shape with a uniform diameter along the longitudinal
length of the cylindrical portion 32. As best shown in FIGS. 15
and 16, the outer surface 50 of at least a portion of at least one
of the electrodes 29a-c, 30a-c is stepped up or otherwise protruding
relative to an adjacent exposed outer surface 28 of the probe body
26 by the thickness of the electrodes, preferably in a thickness
range between and including about 0.01 mm to 2.0 mm and, more preferably,
in the range between and including about 0.1 mm to 0.5 mm. As shown
in FIGS. 15 and 16, the outer surface 50 of all of the electrodes
29a-c, 30a-c is stepped up relative to an adjacent exposed outer
surface 28 of the probe body 26 by the thickness of the electrodes.
Another exemplary electrosurgical device of the present invention
which may be used in conjunction with the system of the present
invention is shown at reference character 5b in FIG. 17, and more
particularly in FIGS. 17-19. As best show |