U.S. patent application number 09/725976 was filed with the patent office on 2001-04-12 for sterilization of elongate lumens.
Invention is credited to Kowanko, Nicholas.
Application Number | 20010000227 09/725976 |
Document ID | / |
Family ID | 46257271 |
Filed Date | 2001-04-12 |
United States Patent
Application |
20010000227 |
Kind Code |
A1 |
Kowanko, Nicholas |
April 12, 2001 |
Sterilization of elongate lumens
Abstract
A method of and system for sterilizing the internal surfaces of
one or more elongate relatively narrow passages of interest
contained in a device of interest, said passages having end
openings and being susceptible of sustaining flow there along by
inducing a positive flow of sterilizing gas through each passage of
interest in a selected direction. Gas flow through a device of
interest is caused by a passive two-chamber device which generates
a transient pressure gradient between the ends of the lumens of the
device in response to externally imposed variations of pressure.
Sterilant gas is provided from outside the two chamber systems.
Inventors: |
Kowanko, Nicholas; (Punta
Gorda, FL) |
Correspondence
Address: |
C. G. Mersereau, Esq.
NIKOLAI, MERSEREAU & DIETZ, P.A.
820 International Centre
900 Second Avenue South
Minneapolis
MN
55402-3813
US
|
Family ID: |
46257271 |
Appl. No.: |
09/725976 |
Filed: |
November 29, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09725976 |
Nov 29, 2000 |
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09135146 |
Aug 17, 1998 |
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6162395 |
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Current U.S.
Class: |
422/33 ; 422/119;
422/297; 422/300 |
Current CPC
Class: |
A61B 1/125 20130101;
A61L 2/206 20130101; A61L 2/208 20130101; A61L 2202/24 20130101;
A61L 2202/122 20130101; A61L 2/204 20130101 |
Class at
Publication: |
422/33 ; 422/119;
422/297; 422/300 |
International
Class: |
A61L 002/20 |
Claims
What is claimed is:
1. A method of gas phase sterilization of elongate devices of
interest of a class having internal surfaces which include one or
more elongate lumen passages of interest, said passages having end
openings and being susceptible of sustaining a flow of gas there
along the method comprising the steps of: (a) inserting one end of
each device of interest including one end of said passages of
interest through a resilient opening in a closed chamber, said
closed chamber being opened to each said passage of interest and
wherein said closed chamber has a volume greater than the total
volume of all connected passages of interest to be sterilized; (b)
establishing a net flow of sterilant gas through each passage of
interest in a selected direction by subjecting the one or more end
openings not inserted into one of said closed chamber to transient
alternating cycles of decreasing pressure and pressurization
thereby producing a directionally reversing net flow through said
one or more passages of interest; (c) introducing sterilant vapor
with said repressurization steps of said cycles; and (d) varying
said pressure sufficiently that said net flow in each direction
exceeds the volume of said one or more passages; (e) providing
vapor permeability for sterilizing the portion of said devices of
interest at the connection with said closed chamber.
2. A method of gas phase sterilization as in claim 1 further
comprising the step of: (f) enclosing said device of interest with
said removable closed chamber attached in a storage container
having a gas permeable, external access port for evacuation and
pressurization.
3. A method of gas phase sterilization as in claim 2 further
comprising the step of: (g) enclosing said storage container in a
larger sterilization vessel for pressure cycling.
4. A method of gas phase sterilization as in claim 1 wherein said
device of interest contains a single passage of interest.
5. A method of gas phase sterilization as in claim 1 wherein said
device of interest contains a plurality of passages of
interest.
6. A method of gas phase sterilization as in claim 1 wherein the
said resilient opening is stretched by insertion of said device to
provide a seal between the device and the chamber.
7. A method of gas phase sterilization as in claim 2 wherein said
storage container is a formed gastight plastic tray having a gas
permeable area.
8. A method of gas phase sterilization as in claim 6 wherein the
chamber is built as an integral part of the tray.
9. A method of gas phase sterilization as in claim 6 wherein the
chamber is snapped fit into the tray.
10. A method of gas phase sterilization as in claim 9 wherein said
elongate device is also snapped fit into said tray.
11. A method of gas phase sterilization as in claim 1 further
comprising the step of: (h) providing the chemical indicator in
said chamber which provides a visual indication that a quantity of
sterilant gas has passed through an entire passage of interest and
into said chamber during the sterilization.
12. A method of gas phase sterilization as claimed in claim 2
wherein said removable closed chamber is only partially contained
in said storage container.
13. A method of gas phase sterilization as in claim 1 wherein said
resilient opening in said closed chamber provides sufficient gas
permeability such that the area of said device passing through said
opening is also sterilized during the process.
14. A method of gas phase sterilization as in claim 2 wherein said
storage container is a peel pouch.
15. A gas phase sterilization packaging system for the
sterilization of elongate devices having one or more discreet
elongate narrow internal passages or of interest comprising: (a) a
hollow vessel having an elastic resilient opening for containing
one end of said elongate device, said elastic opening providing a
seal between said elongate device and said chamber opening; (b) a
storage container for containing said chamber and said elongate
device during and after sterilization, said storage container
having a gas permeable, external access port for evacuation and
pressurization; and (c) wherein said storage container is designed
for placement into a system designed to draw a vacuum and
pressurize said storage container and, through said passages
therein, said attached chamber, in a manner to induce a reversing
transient net flow between said attached chamber or vessel and said
storage container through said internal passages and; (d) wherein
said chamber has a value greater than said passages to be
sterilized.
16. The apparatus as in claim 15 wherein said storage container is
a molded plastic tray and wherein said chamber is formed as an
integral part of said tray.
17. The apparatus of claim 15 wherein said storage container is a
molded plastic tray and wherein said chamber is fit into a recess
in said tray.
18. The apparatus of claim 15 wherein said storage container is a
peel pouch.
19. The apparatus of claim 18 wherein said chamber is not fully
contained in said peel pouch.
20. The apparatus of claim 15 further comprising a chemical
indicator in said chamber capable of producing a color change
indicative of concentration of sterilant gas having been received
in said chamber through said passages to be sterilized.
Description
CROSS REFERENCE TO RELATED APPLICATION
1. This application is a continuation-in-part of application Ser.
No. 09/135,146 filed Aug. 17, 1998. That application is deemed
incorporated by referenced herein in its entirety.
BACKGROUND OF THE INVENTION
2. Field of the Invention
3. The present invention relates generally to gas phase (vapor)
sterilization and, more particularly, to disinfecting and
sterilizing devices having elongate, narrow passages or lumens
accessible from both ends such as those commonly associated with
vascular catheters endoscopes and similar devices. While the entire
device must be sterilized, the invention is primarily concerned
with the successful sterilization of the more difficult internal
surfaces concurrently with sterilization of the exterior. The
invention employs techniques that produce a flow of sterilizing gas
through the internal passage or passages in a given load (items to
be concurrently sterilized) during processing which results in a
rapid and complete exposure of internal passage or channel surfaces
of each item of the load to the sterilant vapor by transforming
each lumen or other channel or passage of interest into a flow
channel for the sterilant gas during successive evacuation and
pressurization cycles.
4. Related Art
5. The need to sterilize articles such as medical devices and
instruments following manufacture and initial packaging for use or
prior to reuse after contacting a patient has long been recognized.
Traditional methods of sterilization include immersion of the
article or instrument of interest in a sterilizing solution or the
use of various techniques involving elevated temperatures. More
recently, however, it has been recognized that chemical vapor
sterilization at lower temperatures is generally better suited to
today's more sensitive and sophisticated instrumentation and
materials of construction. Moreover, financial constraints placed
generally on medical care providers presently produce situations in
which "single-use" items previously discarded after the first
patient are now being resterilized and reused.
6. While vapor sterilization has offered several distinct
advantages over other forms, one major disadvantage heretofore
associated with the technique involves an inability to conduct
sufficient sterilizing vapor to contact the central internal
surfaces of rather long and narrow passages such as the lumens of
catheters and endoscopes in an expeditious manner. Typically,
present systems operate by partially evacuating the sterilization
chamber prior to the introduction of the sterilizing material in a
repressurization step. The chamber may be subjected to a series of
evacuation and pressurization cycles in this manner. Complete
sterilization of the internal surfaces depends on diffusion of the
sterilant gas, which might be ethylene oxide or another material
usually diluted in a carrier gas along the passages from the open
ends to produce sufficient antimicrobial activity at the midpoint
of each narrow passage. Unfortunately, normal diffusion and other
mixing techniques are simply too slow to accomplish reliable
sterilization at passage midpoints within desired time constraints
and this may offset other advantages of vapor sterilization. The
problem is documented, for example, in Alfa, M. J., "Changes In
Hospital Practice", Biomedical Instrumentation and Technology
(September/October 1996) and Alfa, M. J. et al, "Comparison of Ion
Plasma, Vaporized Hydrogen Peroxide, and 100% Ethylene Oxide Gas
Sterilizer", Infection Control And Hospital Epidemiology (February
1996).
7. Several ways of overcoming the above disadvantage have been
proposed with respect to vapor sterilization of relatively long and
narrow passages. In one technique, a closed vessel containing a
small amount of a vaporizable antimicrobial fluid is attached to
one end of an endoscope or other device lumen. A seal is breached
in the vessel and the other end of the lumen is exposed to a
reduced pressure. This allows antimicrobial vapor to flow along the
length of a lumen from the source toward the open end. Such a
technique is shown in U.S. Pat. Nos. 5,580,530 and 5,733,503 to
Kowatsch et al and in Jacobs et al (U.S. Pat. No. 4,943,414).
Another technique shown in Childers et al (U.S. Pat. No. 5,527,508)
discloses a pressure modulation technique using a low vapor
pressure chemical vapor sterilant in conjunction with a compression
carrier gas to promote diffusion in a pressure modulation cyclic
sequence. Meanwhile, manufacturers of these devices have been
resorting to drastically extended gas sterilization cycles,
sometimes taking days to complete, to insure sterility of their
device products.
8. While these previous techniques have met with some success,
there remains a need for a method and system that provides more
certain and immediate contact between the sterilizing vapor and the
internal passage surfaces, particularly the surfaces nearest the
midpoint of the passages, to enable the surfaces to be sterilized
in an expeditious manner which need not depend on internal
diffusive mixing equilibrium.
9. With regard to certain terminology used in this specification,
definitions seem appropriate. The terms "sterilant gas or sterilant
vapor" or "sterilizing gas or sterilizing vapor", as used in this
specification, refer to any substance, whether true gas or vapor of
a volatile liquid, which is capable of sterilizing the load of
interest and which is in the gaseous state under use conditions. It
may consist of a single active ingredient or a mixture of
ingredients, and may contain inactive diluents or carriers. Also,
the term "lumen", "channel", "passage", or the like, refers to any
internal passage accessible from both ends which is relatively long
in relation to its diameter and therefore difficult to readily
sterilize near or at its midpoint by diffusion of a sterilant gas
from the ends. "Cassette" refers to any relatively compact package
form suitable for containing and adapted to receive any of the
class of devices (having integral elongate passages) suitable for
sterilization and/or storage in accordance with the invention. The
cassettes may be of any convenient shape and are assumed to be of
sufficient rigidity to withstand the necessary pressure
differential used in the method of the invention and the term
includes, without limitation, the common rectangular shaped
containers. The term "sterilization" means a sufficient reduction
in the live microbe and/or spore population to render the device of
interest to be safe for its intended use. This is normally a 7-9
log.sub.10 reduction of the bacteria and/or spore population.
10. Accordingly, a primary object of the present invention is to
provide an improved method of vapor sterilization particularly
suited to the sterilization of devices of interest having internal
surfaces including relatively long, narrow passages characteristic
of the lumens of catheters and endoscopic instruments, together
with devices for carrying out the method.
11. Another object of the present invention is to provide an
improved method of vapor sterilization that is based on inducing a
reversible positive flow of sterilant vapor throughout the length
of a passage of interest to be sterilized.
12. Yet another object of the present invention is to establish a
positive flow of sterilant vapor throughout the length of a passage
to be sterilized by inducing an end-to-end pressure differential to
an open-ended passage to be sterilized by exposing each end to a
different time variable (transient) pressure function to transform
the passage into a flow channel and to promote flow therethrough to
produce immediate antimicrobial activity along the entire length of
the passage.
13. Still another object of the present invention is to accomplish
the method of the invention using only a passive partitioned
cassette to contain the device of interest and a
vacuum/pressurization chamber to contain the cassette.
14. Yet still another object of the present invention is to provide
a close tolerance passage or gas permeable collar at the partition
wall within the cassette so as to achieve sterilization of the area
of the device contacting the partition.
15. A further object of the present invention is to produce a time
variable (transient) end-to-end pressure differential in each
open-ended passage to be sterilized on a reversing basis.
16. A still further object of the present invention is to provide a
partitioned two-chamber cassette to contain a device having an
elongate passage to be sterilized with one end in each chamber
having gas permeable accesses in each chamber to be exposed
simultaneously to vacuum/pressurization sterilization cycling in
which the combination of the relative chamber sizes and
permeabilities can be used to determine the time variable pressure
difference between the chambers.
17. These and other objects, as well as these and other features
and advantages of the invention, will become apparent to those
skilled in the art upon familiarization with the specification,
drawings and claims contained herein which are meant to exemplify
but not to limit the scope of the present invention in any
manner.
SUMMARY OF THE INVENTION
18. The present invention provides a new method and apparatus for
achieving timely total gas or vapor sterilization in devices
generally having internal passages which are difficult to sterilize
utilizing diffusion techniques. These include, for example, the
elongated lumens of vascular catheters and the interior passages of
endoscopes. The present invention achieves rapid vapor
sterilization by providing for immediate and complete contact
between the internal surfaces of the instrument passages and the
sterilizing vapor by providing means which produce a flow of
sterilant gas in and throughout the entire length of the passage of
interest to be sterilized. The present invention enables a variety
of open-ended passages including the long, narrow tubes or
instrument passages of endoscopes or catheter lumens to be
dependably sterilized internally in a timely manner even at the
most difficult central portion of the load. The method adapts to a
number of apparatus embodiments, some of which are illustrated in
the detailed description by way of example, and lends itself to the
use of existing equipment.
19. The present invention introduces a method and apparatus for gas
phase sterilization of elongated tubular devices of interest in
which sterilant gas flow through lumens of the devices of interest
is induced by a flow-dependent transient pressure gradient set up
between the ends of the lumens. The transient pressure gradient can
be created by exposing each end of each lumen to a separate chamber
and concurrently evacuating or concurrently pressurizing both
chambers at different effective rates. A preferred method is one in
which each end of a passage of interest in a device to be
sterilized is subjected to a different transitory pressure change
function when a sterilization container containing the device is
exposed to a vacuum or pressurization step thereby producing a
transitory pressure gradient function between passage ends which
transforms the passage of interest into a flow channel and induces
a flow of sterilant gas along the length of the passage. The
different transitory pressure change functions may be produced in
any of a number of ways which result in the net effect of a
pressure gradient which typically operates to induce a flow of
sterilant material in one direction when the ambient pressure is
reduced as by a vacuum pump or in the opposite direction when the
pressure is increased by the introduction of sterilant gas.
20. A device to be sterilized is generally loaded into a storage
container, preferably in the form of a cassette, which may be of a
design unique to that species of device. The container is provided
with two compartments or chambers of equal or unequal, but
relatively fixed size. At least one of the chambers has an area of
vapor permeability that accesses the volume outside the cassette.
When a device is loaded for sterilization, one end of each of the
elongate passages or lumens of interest is situated in each
chamber. By modulating the pressure outside the cassette, both
chambers are subjected to evacuation/pressurization cycles with
sterilant gas being added in the pressurization cycles in a manner
that effectively affects the chambers according to different
transitory pressure change functions and thereby induces a flow
between the chambers in the passages of interest. Flow in one
direction during evacuation reverses during pressurization.
21. The chamber sizes and difference in the transitory pressure
change functions are preferably sufficient to cause at least one
complete volume change in all passages of interest. It will be
appreciated that a net flow that amounts to less than one volume
change will also eventually result in sterilization in accordance
with the invention; however, additional cycles and thus a longer
sterilization time will be required with lesser flow amounts. As
used herein, net flow means the flow through the passages of
interest during one pressurization or evacuation cycle. Flow
through the passage of interest can be accomplished in a number of
ways. If the two cassette compartments are unequal in size,
evacuating or pressurizing them at the same volumetric rate will
produce a different rate of pressure change in the compartments to
produce the desired effect. Of course, to produce a volume change,
the smaller volume chamber must still have a volume that exceeds
the total volume of the passages to be sterilized. If the cassette
compartments are not sufficiently unequal in size, relatively
diverse volumetric flow rates for evacuation/pressurization can be
used to compensate. Relative flow rates can be adjusted in a number
of ways according to the invention. For example, the two chambers
of the cassette may be provided with gas permeable accesses of
different capacities and the cassette exposed to the cycle steps
within a common larger sterilizing chamber or the chambers may be
connected to vacuum/pressurization devices that effectively treat
them unequally due to size of connection, relative permeability,
etc.
22. Direct cross flow through the barrier between the chambers is
minimized by a low clearance fit or by sealing devices between the
item to be sterilized and the barrier wall. The seal is preferably
a resilient, but porous material such as a foam material that
allows seepage but not direct flow. However, a relatively low
clearance fit may also be used. It is an important aspect of the
invention that the entire device be sterilized and, accordingly,
sterilant material must readily reach and sterilize that segment of
the device which is in the vicinity of the barrier or partition,
either directly or through a porous material. It is noteworthy that
the method can manifest itself in any of a variety of devices and
technique combinations and offers a new practical solution to a
long-standing problem.
23. In accordance with the operation of the device or method of the
invention, when the assembly is evacuated, gas will flow from both
chambers, however, since the time related transient flow function
for each is different, the pressure within one chamber will drop
faster than that within the other chamber. This temporary pressure
differential will induce a net flow of gas throughout the length of
the tubes or passages to be sterilized inside the cassette.
Conversely, upon repressurization with sterilant gas, the net flow
will reverse as the same chamber will fill more readily. By cycling
the system, this technique produces two-way time varying or
transient, reversing flow of relatively full strength sterilant gas
to maintain high antimicrobial activity along the entire length of
the device to be sterilized. The rate of depletion of sterilant
material potency in use should also be considered in arriving at
ideal cycle times. The typical pressure range for the operation of
the process may cycle from less than 1 Torr to several
atmospheres.
24. The required time and number of cycles also will vary with the
type of items to be sterilized and the previous histories of those
items. Typically, 2 to 5 evacuation/pressurization steps are
required.
25. Of course, the open-ended internal passages or lumens of
interest need not run the length of the device; they only need
straddle the barrier between the chambers. Thus, guidewire or other
shorter lumens contained some devices in addition to much longer
lumens may be sterilized by proper placement of the device so that
one access opening is on either side of the barrier.
26. Any sterilant material compatible with the material of the
endoscope or other device being sterilized may be employed as the
sterilizing vapor. For example, one may employ ethylene oxide
(ETO), hydrogen peroxide (H.sub.2O.sub.2), formaldehyde (HCHO) or a
variety of peracid materials such as those disclosed in applicant's
copending application, Ser. No. 08/032,606, filed Mar. 17, 1993,
now U.S. Pat. No. 6,036,918, issued Mar. 14, 2000. Purge cycling,
as required, is used to remove chemical sterilants after
sterilization.
27. Of course, those skilled in the art will recognize that
sterilant material is consumed by impurities during the
sterilization process which, in turn, reduces the strength or
anti-microbial capacity or potency of the gas unless the sterilant
is replenished. This is particularly true in confined spaces. The
flow-through system of the invention changes the gas within even
the most clandestine central passage spaces often enough to enable
the strength of the sterilant to be maintained at a relatively high
level throughout the load during the process.
28. The invention may also operate using a single access. One
single access embodiment that employs the technique of the present
invention involves providing one end of an open-ended endoscope
tube or other elongated open-ended hollow device to be treated with
a closed chamber in the form of a removable gastight hollow fitting
(cap or bulb) of internal volume greater than the internal volume
of the device to be sterilized to assure sufficient flow through
during sterilization. The hollow fitting preferably includes a gas
permeable collar that fits over the endoscope tube or the end of
another device of interest constructed so that the area under the
collar is also exposed to the sterilant gas and the entire device
is sterilized. This system is designed to be placed in a packaging
container that, in turn, is itself placed entirely inside of a
pressure variable gas sterilization chamber for processing. In this
manner, the packaging container becomes a second chamber which
contains the first, i.e., the larger chamber entirely contains the
smaller with the passages of interest situated therebetween with
respect to flow. A similar effect is realized when one compartment
of the cassette embodiment is sealed and the entire system is
forced to "breathe" through the other via the passages of
interest.
29. During sterilization, the pressure is cycled on a time variable
basis as with the cassette system previously described. The
packaging container is first partially evacuated and thereafter the
desired amount of active sterilant gas is admitted. Sterilant gas
entering the chamber enters each partially evacuated lumen at the
exposed open end thereof and flows through each entire device
passage to equalize the pressure in the cap, bulb or closed
cassette chamber volume thereby providing a fresh stream of
sterilizing gas throughout the length of the tube. During
subsequent evacuation stages of the sterilizer chamber, the stored
excess of vapor within the volume of the cap, bulb or closed
cassette chamber will flow out again sweeping through the entire
length of the hollow lumen providing further contact with the
entire inner surface.
30. Alternatively, the device may be enclosed in a gas permeable
container or bag and the tightly fitting chamber placed over one
end of the package so as to enclose one opening of the device
lumens, the package or bag acting as a gas permeable collar. This
embodiment is especially useful for endoscopes packaged to be
stored hanging in a straight posture. It will be appreciated that
the cassettes or other such devices of the present invention
readily replace typical contemporary flow-through (gas permeable)
sterile soft-sided packaging (some of which are also known as peel
pouches), and which can be used with some single access versions of
the present invention. The cassettes or cap or bulb devices should
be rigid enough to resist flexure during cyclic pressure changes
although large pressure differentials do not normally occur.
BRIEF DESCRIPTION OF THE DRAWINGS
31. In the drawings, wherein like numerals are utilized to
designate like parts throughout the same:
32. FIG. 1 illustrates schematically a perspective view of a
two-compartment cassette system for accomplishing vapor
sterilization in accordance with the invention;
33. FIG. 2 is a schematic perspective diagram of an enclosed lumen
and bulb single access arrangement for a device to be sterilized in
accordance with the invention;
34. FIG. 3 illustrates in perspective a greatly enlarged
inter-chamber transition area as in FIG. 1 partially cut away to
show portions of the interior and a gas-permeable layer;
35. FIGS. 4 and 5 schematically illustrate in perspective a further
adaptation or variation useful for processing endoscopes;
36. FIG. 6 depicts in perspective an alternate embodiment of the
cap or bulb of FIG. 2 or the container of FIG. 4 for receiving one
end of a device to be sterilized;
37. FIG. 7 is a fragmentary perspective schematic representation of
an embodiment utilizing a formed plastic tray and chamber
arrangement for accommodating an elongated lumen device for
sterilization;
38. FIG. 7A is a an enlarged perspective view of the chamber of
FIG. 7;
39. FIG. 8 is a fragmentary schematic perspective view of a device
similar to that in FIG. 7 in which the chamber is an integral part
of the tray;
40. FIG. 9 is a fragmentary schematic perspective diagram
illustrating another arrangement in which the lumen is contained in
a medical bag attached to a partially external plastic chamber
within a sterilizing environment; and
41. FIG. 10 is a fragmentary schematic perspective diagram similar
to that in FIG. 8 wherein both the elongated lumen to be sterilized
and the plastic chamber are contained within a gas permeable sealed
peel pouch.
DETAILED DESCRIPTION
42. The present invention offers a method for gas phase
sterilization of elongated tubular devices of interest, such as
medical catheters and endoscopes, in which sterilant gas flow
through the lumen(s) of the devices of interest is induced by
creating a different transient pressure gradient function at each
end of those lumens. The transient pressure gradient is preferably
created by exposing each end of each lumen to a separate chamber
and concurrently evacuating or concurrently pressurized both
chambers at different effective rates. The method can be practiced
using any of a variety of sterilization devices and provides new
flow-through approaches to the total gas or vapor sterilization of
relatively elongate narrow open-ended passages in medical and other
devices requiring sterilization that enables rapid and total
sterilization by virtue of providing a positive flow of sterilizing
gas contacting all internal surfaces. As indicated, the approach is
particularly suited to long and narrow passages with end openings,
the central portions of which have heretofore challenged and
resisted timely vapor sterilization because of the difficulty in
accessing these regions with effective antimicrobial
concentrations.
43. It will be appreciated that any suitable sterilant gas may be
used in accordance with the present invention including ETO,
H.sub.2O.sub.2, HCHO, ion plasma sterilizers, peracids, including
performic acid, peracetic, perpropionic acid and mixtures thereof
as more completely described in the above-cross referenced
copending application. The techniques of the invention are
particularly useful for cold sterilization which, as used herein,
refers to procedures which effect sterilization at temperatures
substantially below the 120-132.degree. C. typically employed using
high pressure steam techniques.
44. In addition, any suitable range of pressures may be employed in
implementing the techniques of the invention, although a range
which centers at or below one atmosphere is generally the easiest
to implement. The process is also generally designed to enable
operation at relatively low sterilization temperatures, i.e., below
100.degree. C. and preferably below 70.degree. C. In addition, any
type of device having intricate internal passages which are openly
accessible but difficult to reach by diffusion and which will admit
to sterilization using the present invention are presumed to be
intended to be included and those illustrated, together with the
particular embodiments or devices to carry out the invention, are
given by way of example and not limitation.
45. FIG. 1 depicts a preferred embodiment in which a hollow
sterilizing cassette package or container having a body generally
at 10 and a removable lid 11 is nominally subdivided into unequal
compartments including a first small chamber or compartment 12 of
volume V.sub.1 and a second chamber or compartment 14 of volume
V.sub.2. The cassette package including body 10 and lid 11 is shown
inside a larger sterilization chamber shown as a transparent
fragment at 16 of volume V.sub.3 which is attached by one or more
external accesses represented by 18 which represents both a gas
admitting or supply system that includes a source of sterilizing
and/or purge gas 36 and to a vacuum system (not shown) in a
well-known manner. Separation of the compartments 12 and 14 is
accomplished by a separator barrier or partition 20. The separator
20 as indicated by the arrow 22 may be located in a variety of
locations as shown in phantom at 20a and 20b depending on the
desired relative sizes of V.sub.1 and V.sub.2 and generally
contains one passage or opening therethrough, which is illustrated
as having components or portions in the body 10 and lid 11 at 26 to
accommodate an elongated, hollow tube 28 to be treated. The tube is
situated with one open end 30 in the compartment 14 and the other
open end 32 in the chamber 12. When the cassette is assembled, the
passage 26 should be snug with, but not in gastight relation to the
tube 28. A snug fit between the tube 28 and the barrier 20
minimizes direct flow between the chambers, but allows leakage for
sterilization of the entire device is all that is necessary.
External vapor-permeable areas accesses or ports connecting to the
container 12 are represented for the chambers 12 and 14
respectively by 34 and 36. The tube 28 represents any elongated
device lumen or passage and the areas 34 and 36 represent accesses
of any size or degree of permeability. It will be understood that
the lid 11 and body 10 are provided with the necessary peripheral
seals when assembled.
46. The embodiment of FIG. 1 is designed to operate by pressure
modulation in the chamber 16 (V.sub.3) using alternating evacuation
and sterilizing gas input or pressurization steps for sterilization
as through access 18. Generally, V.sub.3>>(V.sub.1+V.sub.2)
and a wide range of ratios between V.sub.1 and V.sub.2 is
acceptable when the transport capacity of accesses 34 and 36 are of
the same or nearly the same vapor transporting capacity provided
that one is larger than the other. The higher the ratio, the
greater will be the transient pressure gradient allowing the
selection of an optimum ratio for a particular application, pumping
rate, etc. However, the smaller chamber should still be greater
than the total internal volume of the lumens to be sterilized.
Typically, the desired ratio between V.sub.1 and V.sub.2 is from
about 2:1 to about 20:1; however, lower or higher ratios may be
employed if desired.
47. Both compartments 12 and 14 may alternatively be connected via
a conduit arrangement attached at 34, 36 (not shown) to a common
source of sterilizing vapor and a common evacuating system in a
well known manner. In addition, the connecting vapor-permeable
accesses may be unequal in vapor transmission capacity to thereby
produce a difference in effective rates of pressurization and
evacuation for the two chambers. In this variation, the two
compartments 12 and 14 may be equal or unequal in volume. Also,
only one access need be used in one embodiment where the system
interfaces through only one chamber. This represents one version of
a single access system and can be accomplished by closing one port
or vapor permeable access 34, 36. The vapor passing or transmitting
capacity of the areas 34, 36 may be varied by adjusting size,
permeability or both and that may be combined with sizing the
compartments 12 and 14 to produce any conceivable combination. The
rate of change of the external pressure in the main chamber
represented by 16 or V.sub.3 can also be varied.
48. FIG. 2 illustrates a single access configuration in which a
first chamber V.sub.5 is entirely contained within a second V.sub.6
and the lumen of interest V.sub.4 extends between V.sub.5 and
V.sub.6. It will be recognized that this is similar to removing
either V.sub.1 or V.sub.2 in FIG. 1 and sealing the remaining
access to the outside 34 or 36 such that the function of the
remaining chamber (V.sub.1 or V.sub.2) is assumed by V.sub.3 which,
of course, preserves the general principle of FIG. 1. An elongated
tube generally at 40, shown broken at 42, illustrates an elongated
internal lumen at 44 which encloses or contains a total volume
denoted as V.sub.4. A hollow cap or bulb 46, having an internal
volume V.sub.5, is shown attached to the tube 40 using a gas
permeable collar 48. This assures sterilization of the entire
device. This system is further enclosed in a chamber or package
shown transparent and broken at 50 which has an internal volume
represented by V.sub.6. Both end accesses 52 and 54 of the tube 10
are open so that a free flow between V.sub.5 and ambient through
V.sub.4 may be established, together with flow penetrating the
collar 48. The relative sizes of V.sub.4 and V.sub.5 are without
restriction except that, to promote timely sterilization, V.sub.5
V.sub.4. A preferred range of ratios between V.sub.5 and V.sub.4 is
from approximately 1 to 10 with a most preferred range of about
2-4. Of course, normally V.sub.6>>V.sub.5 +V.sub.4. This will
depend on the nature of the device to be processed.
49. In this embodiment, the entire assembly including the attached
cap or bulb is designed to be subjected to sterilization in a
common package represented by chamber 50, which may be placed in a
sterilization chamber as at 16 in FIG. 1. The package 50 is shown
having a permeable access 56 and an internal volume V.sub.6. Of
course, the ratio of V.sub.5 to V.sub.4 designed for a particular
sterilant or sterilization process, such that cycling of the
pressure in V.sub.6 produces sufficient reversible flow through the
opening 52 to enable the entire volume V.sub.4 to be purged quickly
in both directions by the actual or net flow in and out of
V.sub.5.
50. In operation, the sterilization chamber containing the device
of FIG. 2, including dimensionally stable flow-through container 50
is, in turn, placed in a conventional sterilization chamber (not
shown), made accessible to a vacuum system and a pressurization
system through the access represented by 56 which may be similar in
configuration to 34, 36 of FIG. 1. The volume V.sub.6 is first
evacuated to a desired pressure below atmospheric causing outward
flow to equalization. Thereafter, sterilant gas with or without a
carrier gas, as desired, is introduced into the chamber 50 and, as
the pressure in V.sub.6 increases, an amount of this flows inward
through the opening 52, through lumen 44 and through the opening 54
into V.sub.5. This amount exceeds the volume V.sub.4 so that
complete purging and contact with the entire internal surface of
the lumen 44 by the sterilizing gas is assured. These steps are
cyclically repeated at desired timed intervals until sterilization
is completed. After sterilization, the system may be subjected to
one or more cycles using a purge gas such as N.sub.2 to remove
sterilant material.
51. An additional embodiment or configuration is illustrated in
FIGS. 4 and 5 in which an endoscope device 60 with open-ended lumen
61 is sterilized in a storage package 62 that later is mounted to
enable hanging storage in a straight configuration. In FIG. 4, the
package 62 is shown protruding through an opening and partially
deployed in a container 64 having a volume V.sub.7. Vapor permeable
or gas transport areas in the wall of the package 62 are
represented by 66 and 68 and an optional permeable area is shown in
the otherwise sealed container 64 at 70. The passage of the package
62 into the container 64 may be similar to the interchamber
transition area illustrated in FIG. 3. The volume of the package
may be represented by V.sub.8. The system including the container
64 and package 62 may be placed in a sterilization chamber 72
having a volume V.sub.9 and an external connection as at 74 which
is conventionally connected to a vacuum line and source of
sterilant vapor or purge gas according to known techniques. In FIG.
5, the package 62 is shown mounted on a backing 80 for hanging on a
hook as by using opening 82.
52. It will be apparent from the above discussion that the system
of FIG. 4 may be operated according to the method of FIG. 1 when
optional transport area 70 is provided and according to the method
associated with FIG. 2 without it. While the container 64 is
represented as a cubic or box-like structure, it will be
appreciated that it can be of any desired shape so long as it
functions in the manner intended. This, of course, is also the case
with respect to the hollow cap or bulb 46 of FIG. 2 and the
cassette and lid combination of FIG. 1. Moreover, the opening in
the container 64 may be in the form of a clamping device or any
other confining mechanism that fits over one end of the package 62
to cause vapor material flowing between the package 62 and the
container 64 to predominantly use the lumen 61. Thus, for example,
the chamber or container 64 may be a clamp-on envelope device.
53. Such an alternate container is shown at 90 in FIG. 6 which
includes a spring clamp 92 connected to a semi-rigid structure 94.
The clamp 92 provides an opening 96 adapted to receive a tube as at
40 in FIG. 2 or a package as at 62 in FIG. 4 and may have a vapor
transport permeable area as at 98. The clamp 92 is operable to
engage a tube or package for sterilization as needed.
54. In operation, the sterilization cycle for the embodiment
illustrated in FIG. 1 begins with the evacuation of both chambers
12 and 14. If the chambers are unequal in size, because of the
difference in volume between the two chambers, the pressure in the
smaller chamber volume initially decreases more rapidly than that
of the larger one thereby producing a transient pressure gradient
between the two chambers. This imbalance induces a net flow through
the tube 28 from the larger chamber into the smaller chamber which
continues until the pressure finally equalizes at the end of the
evacuation portion of the sterilization cycle. In the next step,
sterilant vapor is introduced into both chambers and a reverse
imbalance occurs with the pressure rising faster in the smaller
compartment than in the larger compartment thereby inducing a
gradient which results in a flow through the tube 28 and collar 26
from the smaller chamber into the larger chamber until pressure
equalization is again reached. Sterilization is accomplished by a
series of cyclical alternate pressurization and evacuation steps,
each resulting in a purging and replacement of the gas atmosphere
within the tube 28, thereby assuring complete sterilization of the
inner surfaces of the tube. Of course, a similar effect can be
produced by varying the vapor transport capacity of the ports 34,
36 accessing compartments. A higher capacity for vapor transmission
produces the effect of making the chamber smaller. As above, a
number of purge cycles may be used at the end of the process to
remove traces of sterilant material from the cassette.
55. While the figures illustrate several embodiments, it should be
kept in mind that many other possible configurations can be used
which will enable the practice of the present invention. Thus,
cassette 10 or package 62 may be replaced by peel pouch package for
containing an endoscope, medical catheter or the like. In addition,
the system can be configured to operate with separate vacuum pumps
and pressurization devices attached at 34, 36 so long as these are
properly controlled and coordinated in order to achieve a desired
transient or time variable pressure gradient between the ends of
the internal lumens of the device to be sterilized. These
accommodations are considered well within the general knowledge of
those skilled in the art.
56. As indicated above, an important aspect of the invention is the
total sterilization of the device of interest and, in this regard,
the passages or openings between the chambers as at 26 in FIG. 1,
48 in FIG. 2 and 76 in FIG. 4 are provided with gas or vapor
permeable material at the interface with the device so that these
areas remain exposed to the sterilant gas during the process. Thus,
the passages 26 and 48 may be appropriately lined as at 27 in FIG.
3 using material that prevents direct cross flow between the
chambers but one which is highly porous to allow penetration of the
sterilant vapor through the layer 27 to the surface of the device
as at 28. A few porous openings are illustrated in FIG. 3 at 29,
but it will be appreciated that the entire surface of the device 28
will be adequately exposed to sterilant gas during the process.
Alternatively, a low clearance fit of low leakage may also
suffice.
57. FIGS. 7, 7A and 8 show another embodiment of containers systems
for use in sterilizing endoscopes, catheters or other such devices
in accordance with the invention in plastic trays which may be
packages for shipping or even trays used for resterilization in the
case of devices which are used more than once and require
resterilization between uses. FIG. 7 depicts a fragmentary view of
a part of a sterilization chamber 100 containing a port 102 which
indicates intake and exhaust communication with a source of
sterilant vapor and vacuum. A formed plastic tray is shown inside
the sterilization chamber at 104 which in turn contains a breathing
medical paper seal or other gas permeable area as indicated at 106
in which vapor exchange can take place with the atmosphere in the
sterilization chamber 100. A device to be sterilized in the form of
an elongated lumen representation is shown at 108 mounted within
the tray and connected at one end by insertion into a chamber 110
at 112. The chamber 110 may be held in a recess in the tray 104 as
part of the retention of the device in the tray, this may be a
snap-fit relation. Optionally, a color chemical indicator 114 may
be placed in the chamber 110 to indicate contact with the sterilant
gas as a result of the sterilization process. The chamber 110 may
be plastic or other material which will withstand a vacuum but
which is sufficiently transparent so that the color indicator 114
can be recognized through the tray. The tray itself is also shown
as a transparent device as is the sterilization chamber in the
illustration, primarily to enhance clarity and understanding.
58. FIG. 7A is an enlarged view of the chamber 110 of FIG. 7 which
can be fabricated from a plastic tube of a much larger diameter
than that of the catheter or scope 108 to be sterilized. The
chamber 110 is provided with a closed end 116 and the chemical
sterilant indicator 114 may be located at or near that end 116.
Also shown are a second enclosure 118 and access opening 112; the
chamber further describes an interior volume at 120 which, as has
been previously described, should be greater than the volume of the
lumen or lumens to be sterilized 108.
59. As previously stated, the plastic tube or other member
describing the generally cylindrical chamber 110 should be
sufficiently strong to withstand a vacuum being pulled on the
system without collapse and the end closings 116 and 118 may be an
integral part of this system or be formed separately and joined by
adhesive, screw or press fits but must be substantially gastight.
The access port 112 is designed for a catheter or scope to be
inserted through it into the chamber and so is preferably of a film
material that is rather thin and elastic. The port hole should be
designed to be undersized so that the catheter scope, as it is
pushed through the hole, will force the hole to enlarge or stretch
and the material will then form a substantially tight seal around
the catheter or scope. As with previous embodiments, however, the
film material must be of a composition that allows some limited
leakage or permeation of gas so as to permit the system to
sterilize the area of contact between the catheter, scope, etc.,
and the film. Thus, materials such as polyethylene film that is
permeable by ethylene-oxide gas or an open-salved foam film should
provide the necessary permeability.
60. The indicator dot 114 represents a chemistry that is affixed to
the inside of the plastic chamber and can be viewed from the
outside of the transparent plastic chamber and also through the
plastic tray 104. The indicator contains the necessary chemistry to
indicate or record, by changing color, the adequate presence of
sterilant gas in a concentration normally required to achieve
sterility. This demonstrates that sterilant gas has passed through
the entire length of the lumen 108 indicating that the device has
been subjected to the sterilization procedure.
61. FIG. 8 depicts an embodiment similar to that of FIG. 7 but in
which the formed plastic tray for containing the lumen-carrying
device 120 is provided with an integral hollow chamber 122 molded
as part of the tray and having an access port at 124 and a chemical
sterility indicator at 126 within the integral hollow chamber. The
criteria for the chamber 122 are the same as those for 110 of FIGS.
7 and 7A and so far as the sterilization process is concerned with
the chamber being formed as a permanent part of the tray rather
than a snap-in arrangement as shown in FIG. 7.
62. FIG. 9 shows yet another variation in which a gas permeable or
breathable medical bag or custom peel pouch 130 contains a catheter
or other lumen containing device 132 which extends through a seal
opening 134 to a attached hollow chamber or tube 136 as previously
described. In this embodiment the tube or chamber 136 is not
entirely enclosed in the breathable medical bag or peel pouch 130
but protrudes partially into the sterilization chamber 100. An
optional chemical sterilization indicator is shown at 136.
63. FIG. 10 is a view similar to FIG. 9 showing the plastic chamber
as being contained entirely within the breathable medical bag or
custom peel pouch 130.
64. While the above description has emphasized elongated devices
having a single open-ended lumen, multiple lumen devices such as
vascular catheters having a plurality of parallel lumens or
multi-lumen scoping devices can also be processed as a number of
parallel elongate passages can be sterilized readily as well
utilizing the techniques of the present invention. The relative
volume relationships, of course, need reflect the total volume of
the devices of interest. Additionally, it will be understood that a
sterilization chamber may be used to simultaneously (concurrently)
process a plurality of the illustrated or other devices in
accordance with the invention. For example, the barrier 20 may be
provided with a plurality of openings 39 to accommodate a plurality
of tubular devices 26 or a plurality of cassettes or devices 10 can
be provided in a batch to be sterilized in a common chamber.
65. This invention has been described herein in considerable detail
in order to comply with the patent statutes and to provide those
skilled in the art with the information needed to apply the novel
principles and to construct and use embodiments of the invention as
required. However, it is to be understood that the invention can be
carried out by specifically different devices and that various
modifications can be accomplished without departing from the scope
of the invention itself.
* * * * *