U.S. patent number 3,889,680 [Application Number 05/440,539] was granted by the patent office on 1975-06-17 for cryoadhesion preventing cryosurgical instruments.
Invention is credited to Thomas Anthony Armao.
United States Patent |
3,889,680 |
Armao |
June 17, 1975 |
Cryoadhesion preventing cryosurgical instruments
Abstract
The cryosurgical instruments disclosed have a sheath of porous
material spaced from a heat conducting core, and an
anti-cryoadhesion material which is cooled to cryogenic
temperatures and thus also acts as a cryogenic fluid is pumped
through the space between the sheath and the core. A part of the
material is exuded through the sheath to prevent sticking of the
material of the sheath to the tissue with which the instrument is
in contact, and the remainder of the material is recirculated. The
porous sheath can be removably attached to the instrument so that a
sheath in the shape of a probe or surgical blade can be used on the
instrument.
Inventors: |
Armao; Thomas Anthony
(Brooklyn, NY) |
Family
ID: |
23749160 |
Appl.
No.: |
05/440,539 |
Filed: |
February 7, 1974 |
Current U.S.
Class: |
606/23;
62/293 |
Current CPC
Class: |
A61B
18/02 (20130101); A61B 2018/0097 (20130101); A61B
2018/0275 (20130101); A61B 2018/0281 (20130101); A61B
2017/00867 (20130101) |
Current International
Class: |
A61B
18/00 (20060101); A61B 18/02 (20060101); A61B
17/00 (20060101); A61B 017/36 () |
Field of
Search: |
;62/293 ;128/303.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pace; Channing L.
Attorney, Agent or Firm: Wenderoth, Lind & Ponack
Claims
What is claimed is:
1. A cryosurgical instrument comprising a body of heat insulating
material, a hollow sheath comprised of a good heat conducting
material at least a portion of which is porous, said sheath being
on one end of said body, a core of good heat conducting material
projecting into said sheath from within said body having the outer
surface thereof spaced from the inner surface of said sheath so as
to leave a space between said core and said sheath, said body
having an inlet passage therethrough opening into said space, said
body having an outlet passage therethrough opening out of said
space, said body having a heat exchange space along the portion of
said core within said body and means for directing a flow of heat
exchange fluid therethrough for exchanging heat between said core
and fluid flowing in said heat exchange space, and means for
supplying a heat exchange fluid to said heat exchange space.
2. A cryosurgical instrument as claimed in claim 1 in which said
inlet passage has a branch connected to one end of said heat
exchange space and the other end of said space being connected to
said outlet passage.
3. A cryosurgical instrument as claimed in claim 1 in which said
sheath is detachably mounted on said body.
4. A cryosurgical instrument as claimed in claim 1 in which said
sheath is in the form of a probe.
5. A cryosurgical instrument as claimed in claim 1 in which said
sheath is in the form of a blade and has a blade portion along one
side thereof having a knife edge thereon.
6. A cryosurgical instrument as claimed in claim 1 in which said
core is a replaceable core.
7. A cryosurgical instrument as claimed in claim 6 in which the
free end of the portion of said core within said body has an
annular groove therearound, and a turnbutton movably extending
through said body and engageable in and disengageable from said
groove for preventing removal of said core when engaged in said
groove and freeing the core for removal when disengaged from said
groove.
8. A cryosurgical instrument as claimed in claim 6 in which the
portion of said core within said body is separate from the portion
within said sheath and has a recess therein, and said portion of
the core within said sheath has a spindle projecting therefrom and
fitting into said recess, and thread means on said spindle and on
the portion of said core within said body around the said recess
engageable with each other for retaining said spindle in said
recess.
9. A cryosurgical instrument as claimed in claim 1 further
comprising a cleaning and purging means having a supply of cleaning
fluid and a supply of purging gas, valve means for alternately
coupling said supplies to the inlet passage of said body, said
cleaning and purging means further being connected to the outlet
passage of said body.
10. A cryosurgical instrument as claimed in claim 9 further
comprising a cover removably secured over said sheath and spaced
therefrom for containing the fluid forced through said sheath
during cleaning and purging.
11. A cryosurgical instrument as claimed in claim 10 in which said
cover has a bleed hole therein adjacent the point where said outlet
passage opens out of said space.
12. A cryosurgical instrument as claimed in claim 10 in which said
sheath has a base threadedly mounted on the end of said body and
said cover is threadedly attached to said sheath around said
base.
13. A cryosurgical instrument as claimed in claim 12 in which said
body has spring loaded coupling means thereon for engaging said
sheath for preventing said sheath from moving when said cover is
removed therefrom.
14. A cryosurgical instrument as claimed in claim 10 in which said
cover is transparent.
15. A cryosurgical instrument as claimed in claim 1 further
comprising a reservoir for a fluid anti-cryoadhesion-cryogenic
material, means coupled to said reservoir for circulating the fluid
material from the outlet passage of said body to the inlet passage
of said body through said reservoir and including a pump, a filter
and a pressure regulator, and further heat exchange means in heat
exchange relationship with said means for cooling said fluid
material to a cryogenic temperature.
16. A cryosurgical instrument as claimed in claim 15 further
comprising a cleaning and purging means having a supply of cleaning
fluid and a supply of purging gas and valve means coupled thereto
and coupled between said reservoir and said means for circulating
the fluid material, whereby said cleaning fluid and said purging
gas can be supplied to said instrument through said means for
circulating said fluid material for also cleaning and purging said
means for circulating the fluid material and said reservoir, and a
bleed valve between said valve means and said reservoir for
removing cleaning fluid and purging gas from said instrument and
said reservoir and said means for circulating the fluid material.
Description
BACKGROUND OF THE INVENTION
There has recently been considerable development of techniques and
instrumentation for use in cryosurgery, i.e. surgery which involves
the use of cryogenic instruments cooled to cryogenic temperatures.
A characteristic of all of these techniques is the cryoadhesion
between tissue and the metal of the instrument being used. This is,
of course, desirable in such surgical procedures as cataract
removal or the removal of cholesterol plaques from blood vessel
walls, and in fact, is what makes these techniques workable.
However, in other areas, cryoadhesion has limited the use of
cryosurgical techniques to probes of various designs and shapes.
Even here, when it is necessary to treat tissue cryogenically and
thereafter remove the probe, it is necessary to apply heat in some
manner to overcome the cryoadhesion. This is usually accomplished
by passing a heating fluid through the instrument or providing
miniature heating devices in the instrument. Such measures are not
only crude, but more important, they are time consuming and thus
can be dangerous where rapid withdrawal of the instrument becomes
necessary.
A further disadvantage of the necessity of providing some source of
heat to overcome the cryoadhesion of the surgical instrument to
tissue is that it is not at all useful in a surgical instrument
which must be moved during use, such as a moving knife. Manifestly,
it is impossible to both cool cryogenically to obtain the benefits
of the cyrogenic temperatures, and, at the same time, heat to avoid
or overcome cryoadhesion.
My prior U.S. Pat. No. 3,391,690 has recognized that tissue will
adhere to cryogenically active surgical instruments. The disclosure
in this patent states that cryoadhesion can be prevented by the
simple application of a viscous lubricant to the tissue contacting
components of said instruments.
However, permanent coverings or coatings of Paralene, Kel-F, Teflon
Silicones and Lubrichrome, etc. have proved to be of insufficient
practical value in the prevention of cryoadhesion of tissue to the
cryogenically active surgical instruments. It is recognized by
those skilled in the art that even minute tabs or shreads of tissue
that will adhere or freeze to the activated instrument will cause
stripping away of the cryogenically treated tissue adjacent to the
instrument upon its withdrawal or movement. This stripping away or
disturbance of the cryosurgicaly treated zone of tissue will expose
a raw denuded highly vascular area and invariably leads to profuse
hemorrhaging, thus negating any beneficial effects of cryogenic
surgery.
In my application Ser. No. 315,314, filed Dec. 15, 1972, now U.S.
Pat. No. 3,786,814, there is disclosed a method of preventing
cryoadhesion and cryosurgical instruments for carrying out this
method. In all of the instruments, there are two systems needed,
one for circulating the cryogenic fluid, and the other for
supplying the anticryoadhesion material to the tissue contacting
surfaces of the instrument. This arrangement necessarily requires a
sophisticated apparatus for handling the two materials.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide cryosurgical
instruments for use in carrying out cryosurgical techniques which
require only a single system for supplying a fluid which is an
anticryoadhesion material which also acts as a cryogenic fluid.
This object is achieved by providing an instrument having a porous
sheath thereon through which an anticryoadhesion material which
also acts as a cryogenic fluid is exuded, which material both cools
the tissue with which the instrument is in contact and prevents
sticking of the material of the instrument to the tissue. One
specific material is fluorinated polyether. A single system
supplies the anticryoadhesion material, cools it to a cryogenic
temperature, and recirculates the portion of the fluid which is not
exuded through the porous sheath. The porous sheath is preferably
removably attached to the instrument so that different sheaths can
be used on a single basic instrument.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in greater detail hereinafter in
connection with the accompanying drawings, in which:
FIG. 1 is a partly sectional elevation view and partly schematic
view of a cryogenic probe according to the present invention with a
removable sheath member thereon;
FIGS. 2 and 3 are sectional views taken on lines 2--2 and 3--3,
respectively, of FIG. 1;
FIG. 4 is a partial section view showing a cover;
FIG. 5 is a sectional elevation view of the upper part of the
instrument of FIG. 1 showing the different form of sheath
thereon;
FIG. 6 is a section taken on lines 5--5 of FIG. 4; and
FIGS. 7 and 8 are partial sectional views showing removable
cores.
DETAILED DESCRIPTION OF THE INVENTION
In its most elementary form, the instrument of the present
invention has a porous sheath spaced from a core of a heat
conducting material, and a circulation system is provided for
circulating a fluid through the space which is an anticryoadhesion
material which also acts as a cryogenic fluid.
The anticryoadhesion material used in the instruments of the
present invention should be a material which is liquid at ambient
temperatures and remaining liquid at cryogenic temperatures, e.g.
down to about -180.degree.C. so that it overcomes the adhesion
between the metal of the cryosurgical instrument and the tissue
contacted thereby, and it must also be a material which has a good
thermal conductivity so that heat can be conducted through the film
of the material from the tissue to the metal of the cryosurgical
instrument. Moreover, the material should be inert and non-toxic,
since it will come in contact with tissue during the carrying out
of the surgical procedures.
One group of such materials are non-toxic, inert liquid
fluorocarbons which remain liquid at cryogenic temperatures, which
fluorocarbons are applied to cryosurgical instruments and, as a
result of the use of such instruments in cryosurgical treatments,
are applied topically to cryosurgically treated tissue. As the
temperature drops, these materials do not crystallize but only
become increasingly viscous. These materials are available from
several sources. One source is the fluorocarbon chemical sold under
the trademark MEDIFLOR by 3M Co. One specific fluorocarbon is
designated FC47 and is a polyfluorinated tertiary alkly amine
having the general formula (C.sub.4 F.sub.9).sub.3 N and has a pour
point of -58.degree.F. Another specific fluorocarbon designated
FC80 is a cyclic perfluorinated ether and has the general formula
c--C.sub.8 F.sub.16 O had has a pour point of -135.degree.F.
Another is designated FC88 and has a pour point of approximately
-115.degree.C. Another source is the fluorocarbon chemicals sold
under the trademark FLUORONETS by Allied Chemical Co. The
fluorocarbon chemicals with the designations P-1F, P-1H, P- 1C,
P-1D and P-11c have pour points from -85.degree. to -125.degree.C.
Among these materials, the materials with the designations P-1F,
P-1H and P-1C are polyfluorinated ethers having the general
formula:
CF.sub.3 FF .vertline..vertline..vertline. FC -- O -- C -- C -- X
(1) .vertline..vertline..vertline. CF.sub.3 FF
where X is fluorine, hydrogen or chlorine. The material designated
P-11C is a polyfluorinated either having the formula:
CF.sub.3 FFFF .vertline..vertline..vertline..vertline..vertline.
FC--O--C--C--C--C--Cl (2) CF.sub.3 FFFF
The materials with designations P-1D and P-11D are perfluorinated
polyethers having the formulae:
CF.sub.3 FF .vertline..vertline..vertline. (F--C--O--C--C--).sub.2
(3) .vertline..vertline..vertline. CF.sub.3 FF
and
CF.sub.3 FFFF .vertline..vertline..vertline..vertline..vertline.
(F--C--O--C--C--C--C--).sub.2 (4)
.vertline..vertline..vertline..vertline..vertline. CF.sub.3
FFFF
Another specific material which can be used as the
anti-cryoadhesion material is one of a family of polyfluorinated
polyethers having the general formula:
F(CFCF.sub.2 O).sub.n CHFCF.sub.3 .vertline. CF.sub.3
where n is a whole number in the range of 1-11 inclusive. The
materials have pour points from -46.degree.C down, depending on the
value of n. This material is available from E.I. DuPont de Nemours
Co. as FREON E Series Fluorocarbons. The characteristics of the
members of the series from 1 to 4 of the material which are
pertinent to the present invention are as set forth in Table I. It
will be seen from this data that the thermal conductivity is such
that the material conducts heat very satisfactorily, yet it remains
liquid to very low temperatures. Even though it has a low boiling
point, especially the lowest viscosity form of the material,
because it will be kept cooled to carry out its function as a
cryogenic fluid this characteristic will not detract from its
usefulness.
The anti-cryogenic materials described above can be used
individually, or they can be blended to obtain viscosities and pour
point temperatures intermediate the viscosities and pour points of
the individual materials.
In order to make it possible to use a cryosurgical instrument to
make a relatively long incision or move over tissue for relatively
long distances, special surgical instruments have been devised
which provide a constant flow of anti-cryogenic material to the
surface thereof which will be in contact with the tissue. Some
embodiments of these instruments will be described hereinafter. It
should be understood, however, that while the description is of
several forms of one form of a probe and one form of scalpel, the
same type of structures can be utilized for clamps, biopsy
instruments, and the like, without departing from the scope of the
present invention. Examples of other such instruments are found in
my U.S. Pat. Nos. 3,391,690 and 3,369,550.
One embodiment of a probe according to the present invention is
shown in FIGS. 1-3, and has a body 10 made, for example, of foamed
polyurethane, such as is sold under the tradename THURANE by Dow
Chemical Co., and having a sheath 10b of metal, e.g. stainless
steel, thereover and a coating 10c of a thermoplastic resin, for
example such as is sold under the tradename LEXAN by General
Electric Co. The body 10 has a seat 10d on the end which is
uppermost in FIG. 1. A porous hollow sheath 11, made of materials
to be described in greater detail hereinafter, is secured to the
seat 10d by a threaded connection 12 or any other equivalent
connection, and the joint is sealed by a gasket 13 in the seat. The
gasket could also be included in the edge of the sheath.
In the center of the body 10 is an elongated recess 14 having a
socket 15 in the bottom thereof which is slightly smaller in
diameter than the diameter of the recess 14. Positioned in the
recess 14 is the shank 16b of a core 16 which is of good heat
conducting material, the free end of the shank 16b being tightly
fitted into the socket 15 so as to hold the shank in the recess
with the surface of the shank spaced from the wall of the recess.
On the other end of the shank 16b is a core head 16a which projects
into the hollow sheath 11 and is shaped so as to leave between the
core head 16a and the inside surface of the sheath 11 a space S.
Spiral lands and grooves 16c are provided on the head 16a. Struts
16d are also provided on the core head 16a which engage and support
the sheath 11.
An inlet passage 10e extends through body 10 from the lower end to
a point near space S and then branches, branch 10f leading into
space S and branch 10g extending to the upper end of recess 14 and
opening into the recess 14 tangentially of the wall thereof. Outlet
passage 10h extends from space S at a point diammetrally opposite
branch 10f out through the body 10.
Around the upper end of recess 14 is an exteriorly threaded ring 17
of insulating material which fits in a threaded seat 17a in body
10. The ring 17 engages snugly around the upper end of shank 16a in
substantially fluid tight relationship. At the lower end of recess
14 is an outlet passage 14a which opens into outlet passage 10h.
The exterior of shank 16b can be spirally grooved as at 16g to
promote spiral flow of liquid along the shank 16b. The wall of the
recess could also be grooved or one or the other or both could have
spiral lands thereon for the same purpose. Both the inlet and
outlet passages are defined by metal tubes extending through the
heat insulating material of the body 10.
A reservoir 18 for fluid anti-cryoadhesioncryogenic material is
provided in a single fluid supply system for the instrument, and
the reservoir 18 is connected to the inlet passage 10e through a
filter 19, a fluid pump 20, a heat exchanger 21, and a quick
disconnect coupling 23. The fluid is successively filtered, pumped
and cooled to a cryogenic temperature, and supplied to passage 10e.
The outlet passage 10h is connected through a quick disconnect
coupling 24 and a pressure regulator 22 to the reservoir. The quick
disconnect couplings 23 and 24 make it possible to remove the probe
from the supply system and replace it with another probe. A
depressor type injection valve 18b can be provided in the reservoir
18 through which anti-cryoadhesion-cryogenic material can be
supplied from a pressurized container 18c, such as an aerosol can
or the like.
All piping in the fluid supply system leading to and from the base
of the instrument body 10 is flexible and is suitably insulated
with flexible insulation. The flexible insulation prevents the
absorption of heat before the fluid reaches the base of the
instrument body 10. An example of suitable flexible insulated
piping is C.V.I. static vacuum insulated radiation-shielded
flexible piping, which is manufactured by C.V.I. Corp., a
subsidiary of the Pennwalt Corp., Columbus, Ohio 43216.
In operation, fluid anti-cryoadhesion-cryogenic material from
reservoir 18 is drawn through the filter 19 through the heat
exchanger 21, sufficient heat being extracted in the heat exchanger
21 to lower the temperature of the material to the desired
cryogenic temperature. The cooled fluid then flows through the
inlet passage 10e and part of it flows through branch 10f into the
space S. The lands and grooves 16c help distribute the fluid evenly
while the struts 16d prevent vibration of the sheath. The pressure
regulator 22 in the return line is set so that the pressure within
the space S is sufficient to force some of the fluid material out
through the pores in the sheath to prevent sticking of the sheath
to the tissue being acted on, while the remainder of the fluid
material supplied to space S continues to flow through space S and
outlet passage 10h and back to the reservoir 18. Heat from the
tissue being acted on flows through the sheath 11 and is taken up
by the fluid material. However, since the circulation is not
sufficiently rapid to produce rapid cooling of the tissue, which is
desirable, due to the necessity to maintain sufficient pressure to
cause the exuding of the fluid material through the sheath, the
core 16 is provided. This also takes up heat which is transmitted
through the circulating fluid material and conducts it from the
core head 16a to the shank 16b. The portion of the incoming fluid
material which flows through branch 10g is conducted through the
recess 14 along the shank 16b, from the end closest to the head 16a
at which the incoming fluid will be coldest, to the other end, and
the heat taken up by the core 16 is given up to the circulating
fluid material flowing through the recess 14. The equipment for
cooling the fluid to cryogenic temperatures is conventional and
will not be described here. It will be clear, however, that the
heat can be extracted at locations other than that shown in FIG. 1,
at the reservoir, for example.
The inner portion or core of the probe is preferably made of a good
heat conducting low thermal expansion metal. One good metal is a
high nickel-iron alloy sold under the trademark INVAR by Carpenter
Steel Co. It can be nickel plated to increase corrosion resistance.
Alternately, a gold plated solid copper inner portion can be used.
Stainless steel, which resists staining during use and can be
cleaned and sterilized readily, can also be used. Use of such a
metal makes possible rapid transfer of heat from the tissue to the
cryogenic fluid. The sheath is preferably thin stainless steel
which has been made microporous, for example, by the process
disclosed in U.S. Pat. No. 3,352,679, which comprises connecting
the stainless steel as an anode in a cell containing a
non-polarizing electrolyte and discharging direct current through
the cell. The gaskets are silicone rubber, which will withstand
cryogenic temperatures.
It will be understood that the sizes of the pores in the stainless
steel sheath can be varied, and that anti-cryoadhesive materials
are available with different viscositites. Those skilled in the art
will be able to provide the proper combination of pore size and
viscosity of the anti-cryoadhesive material with a minimum amount
of difficulty to give optimum results.
An alternate form of porous material for the sheath is a woven
stainless steel wire cloth known as MICROWEAVE, which is available
from Microporous Filter Division of Circle Seal Development Corp.,
Anaheim, Calif. This material is woven from stainless steel wire
drawn to a diameter of as small as 0.001 inch and then heat treated
to restore the ductility and corrosion resistance. To form this
material or the above described materials into a sheath, a die in
the shape of the sheath is made and the material is shaped to this
die in a four slide forming machine.
In use, the instrument must first be dried thoroughly. One simple
way of doing this is by dipping it in a 100 percent anhydrous
alcohol solution and purging with dry nitrogen gas. Preferably,
however, the whole probe, including the interior passages, is
thoroughly dried by means of a purging system described
hereinafter. Then the fluid anti-cryoadhesion-cryogenic material is
pumped through the passage 10e into the space between the sheath 11
and the core 16, and due to the pressure it is under, it is forced
through the porous sheath 11 so as to form a film on the outer
surface of the sheath. The flow of fluid is maintained to cool the
instrument to the desired temperature, and it is then ready for
use.
During the use of the probe, the anti-cryoadhesion property of the
fluid material will prevent the metal of the probe from sticking to
the tissue which is touched by the probe by providing a physical
layer of the material between the tissue and the sheath and also
due to the hydraulic pressure of the material which acts to force
the tissue away from the surface of the sheath.
Thus, the probe or knife can move through or along tissue in the
same manner as room temperature instruments are moved through or
along tissue, thereby removing any restrictions on the use of the
instrument because of the occurrence of cryoadhesion. At the same
time, due to the heat conductivity properties of the fluid
material, heat is removed from the tissue being cut so that the
benefits of cryogenic surgery can be obtained.
In the use of the device of the present invention and the
fluorocarbon anti-cryoadhesive materials disclosed, it has been
discovered that whatever toxicity these materials have can be
reduced by passing them through a microporous filter, such as a
Gelman microporous filter made by Fisher Scientific Co., 711 Forbes
Ave., Pittsburgh, Pa. 15219. Moreover, if it is anticipated that
large amounts of the fluorocarbon anti-cryoadhesive material are to
be used on an individual patient, it may be advantageous to lower
the general body temperature of the patient of about 85.degree.F or
lower by known hypothermia techniques. This will suppress the
general vapor pressure of the fluorocarbon material that will come
into contact with the tissue being acted upon.
One system for purging the instrument is shown in FIG. 1. It is
most convenient to incorporate it in the supply system so that it
can be used on any probe attached to the supply system. A three-way
valve 40 is provided in the piping 18a between the reservoir 18 and
the filter 19, and the valve 40 is connected to a pressurized
supply 42 of anhydrous alcohol, and to a pressurized supply 43 of
dry nitrogen gas by appropriate conduits 40a. A bleed-off valve 44
is provided between the reservoir 18 and the three-way valve
40.
To carry out purging, with the entire probe and supply system
empty, the pump 20 is run at low speed, the valve 40 is set to
supply alcohol to the filter 19 and pump 20, and the bleed-off
valve 44 is opened. The alcohol will then be supplied through the
supply system and passage 10e and branch 10f in the probe into the
space S within the sheath 11, and through the branch 10g and recess
14, and will clean and dry the space S and be forced through the
pores in the sheath and will clean the recess 14. The valve 40 is
then changed over, and nitrogen under pressure purges the alcohol
from the supply system, space S, and the pores of the sheath 11,
the recess 14, and dries the instrument. The spent alcohol and
nitrogen are removed through bleed-off valve 44. The valves 40 and
44 are then reset, and the instrument is ready to have the
anti-cryoadhesion-cryogenic fluid supplied thereto, for example
through the valve 18b.
Alternatively, the more sophisticated purging system shown in FIG.
15 of my patent referred to above can be connected to the
instrument.
As described above, during purging, the alcohol is forced through
the pores in the sheath 11. Depending on the size of the sheath,
and hence its surface area, and the size of the pores, the total
resistance offered by the sheath to the flow of the alcohol may be
less than the resistance offered by the return path from the space
S through the pressure regulator 18 and the alcohol in space S in
such a situation would all be forced through the sheath. To avoid
this situation, it is desirable to provide a cover 50 for the
sheath, as shown in FIG. 4. The cover is comprised of a dome 51,
which is preferably clear plastic, so that the presence of the
purging liquid inside of it can be easily seen, which is
sufficiently larger than sheath 11 to leave a space between the
sheath 11 and dome 51, and a handle 52 preferably integrally formed
with the top of the dome 51. It will, of course, be possible to
make the handle 52 separately and attach it to the dome 51, if
desired. The base of the sheath 11 has an exterior threaded portion
53 onto which interior threads 54 at the base of the dome 51 are
threaded to secure the dome and the sheath to each other. The dome
51 further preferably has a very small bleed hole 55 therein,
preferably at a position adjacent the position of the entrance into
the outlet passage 10h, to prevent an air or vapor lock in the
space T between the sheath 11 and the dome 51. Depending from the
base of the sheath 11 along the outside of the body 10 is a skirt
56 which is angled outwardly from the body 10 and having an
aperture 57 therein, and when the sheath is in position on the body
10, the aperture 57 is aligned with a bore 58 in the body in which
is a spring loaded pin 59 having a rounded top, preferably with a
notch therein. The spring loaded pin 59 normally projects out
through the aperture 57, thus holding the sheath 11 against
rotation while the dome 51 is unscrewed from the sheath 11.
In use, if the sheath 11 is already present on the instrument, the
cover 50 is threaded onto the threaded portion 53 by means of the
handle 52, and thereafter the purging alcohol is passed through the
instrument as described above. The alcohol will be forced through
the porous sheath 11 into the space T, but will be blocked from
further escape by the dome 51. Any air trapped in the space T will
be forced out of the bleed hole 55. The bleed hole 55 should not be
so large as to allow any appreciable amount of liquid alcohol to
escape. Vaporized alcohol can escape, however.
After purging with the alcohol, purging with the nitrogen gas is
carried out as described above. The instrument is then ready for
use, as described above. Preferably, the cover 50 is removed only
after the anticryoadhesion cryogenic material begins to come
through the sheath 11.
Alternatively, it may be desirable to make the sheath 11
disposable, and to supply the sheath 11 and the cover 50 as a
single unit which is used only one time and then disposed of. When
the sheath 11 and the cover 50 are supplied as a single unit, the
dome 51 will already be threaded onto the sheath 11. This unit is
attached to the instrument by threading the unit made up of the
sheath 11 and cover 50 onto the body 10. It will be noted that the
skirt 56 is angled away from the body 10 so that during the
threading of the unit onto the body 10, the skirt 56 will engage
the pin 59 to depress it. When the unit is tightly threaded onto
the body 10, the aperture 57 is aligned with the pin 59 which is
then spring urged through the aperture 57. The pitch of the threads
12 is sufficiently large so that the aperture 57 comes opposite the
pin 59 only during the last turn of the sheath 11. The remainder of
the purging procedure is as described above. To remove the sheath
11, the pin 59 is depressed by engaging a simple pointed tool with
the notch in the end of the pin 59 and pushing the pin 59 inwardly
and then unscrewing the sheath.
The sheath 11 is shown as having the shape of a simple probe.
However, other shapes of sheath can be used. FIGS. 5 and 6 show a
sheath 31 having the shape of a scalpel blade. The sheath 31 is
generally cylindrical, but along one side thereof it has a blade
portion 32a with a cutting edge 32b therein, preferably formed on a
solid metal insert 32. The contour of the knife edge along the
length of the sheath is that of a common form of scalpel. The base
of the sheath has internal screw threads 33 the same size as those
on the sheath 11 so that the sheath 31 can be threaded onto the
body 10 to replace the sheath 11, thereby transforming the
instrument into a cryogenic scalpel. The interior of the sheath 31
is shaped so that it will accommodate the core head 16a and leave a
space S between it and the core head through which the fluid
anti-cryoadhesion-cryogenic material can flow during the use of the
instrument. Other forms of blade shaped sheath which can be used
with the present instrument are shown in FIGS. 3, 4a-4e, 6, 7 and
9-12 of my above-identified patent.
Otherwise, the structure and operation of the instrument are the
same as for the instrument in FIGS. 1-3.
It is desirable to make the core 16 interchangable so that core
heads can be provided which fit inside of the scalpel shaped
sheaths 31 more properly. Two alternate core structures for this
purpose are shown in FIGS. 7 and 8. In FIG. 7, the entire core 16
is removably held in the body 10. At the inner or lower end of the
shank 16k of the core 16, as shown in the Figure, is an annular
groove 16m, and projecting into the groove 16m is the end of a
shaft 61 of a turnbutton 60. The shaft 61 extends through a bore 65
through the body 10 and on the outer end of the shaft 61 is a head
62. Turnbutton holding means is also provided. On an enlarged
portion 63 between the shaft 61 and the head 62 is a male portion
64 of a bayonet type joint, the female portion of which are shown
at 66a and 66b around the end of the bore 65. A spring 67 in the
bore 65 urges the turnbutton 60 outwardly of the body 10.
With the parts in the position shown, the shank 16k is free of the
end of the shaft 61, and the core 16 can be withdrawn from the body
10 and replaced by a different core with the same shape shank. To
hold the shank in the body 10, the turnbutton is pushed into the
bore 65 against the force of the spring 67 and then turned to
engage the male and female portions 64 and 66 of the bayonet joint,
thus moving the end of the shaft 61 into the groove 16m and holding
it there. Disengagement is carried out by turning the turnbutton in
the opposite direction and releasing the force on it, so as to
allow the spring 67 to force the turnbutton to the position as
shown in the figure.
The embodiment shown in FIG. 8 is somewhat less complex than that
of FIG. 7. The head 16a and the shank 16b are separate parts, the
head 16a having a spindle 16n depending therefrom and fitting
tightly into a recess 16r in the shank 16b. Threads 16q around the
spindle 16n where it joins the head 16a engage with threads 16p
around the upper end of the recess 16r in the shank 16b. The head
16a is thus simply unscrewed from the shank 16b and replaced by a
head with a similar spindle and threads.
It is thought that the invention and its advantages will be
understood from the foregoing description, and it is apparent that
various changes may be made in the form construction and
arrangement of the parts without departing from the spirit and
scope of the invention or sacrificing its material advantages, the
forms hereinbefore described and illustrated in the drawings being
merely preferred embodiments thereof.
TABLE I ______________________________________ n 1 2 3 4
______________________________________ Boiling Point 39 101 153 193
.degree.C Thermal Conductivity J/(m) (Sec) (.degree.C) 311 311 311
311 Vapor Pressure at 52.degree.C psia 21.7 2.03 .023 0.82
Viscosity at 25.degree.C CS .03 0.6 1.3 2.3
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