U.S. patent number 3,851,436 [Application Number 05/207,487] was granted by the patent office on 1974-12-03 for sterilizing and packaging process utilizing gas plasma.
This patent grant is currently assigned to The Boeing Company. Invention is credited to Sheila J. Fraser, Roger B. Gillette, Richard L. Olson.
United States Patent |
3,851,436 |
Fraser , et al. |
December 3, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
STERILIZING AND PACKAGING PROCESS UTILIZING GAS PLASMA
Abstract
A continuous flow of gas plasma is admitted to a substantially
evacuated sterilization chamber containing the object to be
sterilized. Argon plasma is produced continually by being subjected
to a radio frequency field. Complex shapes such as capillary
passages through a blood oxygenator can be sterilized by passing
the gas plasma through them. The exterior of objects to be
sterilized can be subjected to gas plasma within a packaging
envelope, and subsequent to sterilization such envelope can be
evacuated and collapsed onto the object to preserve its sterile
character.
Inventors: |
Fraser; Sheila J. (Seattle,
WA), Gillette; Roger B. (Auburn, WA), Olson; Richard
L. (Bellevue, WA) |
Assignee: |
The Boeing Company (Seattle,
WA)
|
Family
ID: |
22770770 |
Appl.
No.: |
05/207,487 |
Filed: |
December 13, 1971 |
Current U.S.
Class: |
53/434; 53/111RC;
422/22; 422/29; 422/45 |
Current CPC
Class: |
A61L
2/14 (20130101) |
Current International
Class: |
A61L
2/02 (20060101); A61L 2/14 (20060101); B65b
031/02 (); B65b 055/12 () |
Field of
Search: |
;21/54,102
;53/22,111R,111A,111B,111RC,112R,112A,112B,21FC ;313/231 ;315/111
;206/63.2R ;250/531 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wolk; Morris O.
Assistant Examiner: Hagan; T. W.
Attorney, Agent or Firm: Beach; Robert W.
Claims
We claim:
1. The process of sterilizing an article which comprises enclosing
the article in a container, enclosing the container in a sealable
chamber, maintaining subatmosphere pressure in the chamber and in
the container, and, while maintaining such subatmosphere pressure
in the chamber and in the container, flowing nonoxidizing gas
plasma into the container, over a surface of the article to be
sterilized and then out of the container into the portion of the
chamber exteriorly of the container, terminating such flow of gas
plasma through the container, and sealing the container to form a
sterilized package for the article.
2. The process defined in claim 1, in which the container is a
plastic bag having sealable openings.
3. The process defined in claim 1, in which the flow of gas plasma
is passed sequentially over the interior and exterior surfaces of
the article.
4. The process defined in claim 3, in which the article is a blood
oxygenator having a plurality of capillary passages therethrough
and a flow of nonoxidizing gas plasma is passed through the
capillary passages.
5. The process defined in claim 1, in which the article is a blood
oxygenator having a plurality of capillary passages therethrough
and a flow of nonoxidizing gas plasma is passed through the
capillary passages.
6. The process defined in claim 5, in which the container is a
plastic bag having an opening, the oxygenator has a tube extending
through the opening of the plastic bag and communicating with the
interior of the oxygenator, and such bag opening and tube are
sealable after the flow of nonoxidizing gas plasma through the bag
opening and the tube has been terminated.
Description
This invention relates to the sterilization by the use of coal gas
plasma of articles sufficiently fragile so that they cannot be
subjected to a high pressure differential or which are made of
material that will become plastic or melt at high temperatures, or
which would be damaged if subjected to thermal shock by an abrupt
temperature change.
A principal object of the present invention is to provide a
sterilizing and packaging process in which the sterilizing
effectiveness of gas plasma is increased by providing a continued
flow of the gas plasma over surfaces to be sterilized with minimum
dilution by air.
Another object is to cover immediately surfaces which have been
sterilized by flow of gas plasma over them so as to preserve their
sterile character.
FIG. 1 is a diagram of representative sterilizing apparatus
utilizing gas plasma according to the present invention.
FIG. 2 is a diagram of another type of sterilizing apparatus using
the plasma process of the present invention, parts being shown in
section. FIG. 3 and FIG. 4 are detail elevations of somewhat
modified portions of the apparatus shown in FIG. 2.
Sterilization of articles by the process of the present invention
is accomplished in a sterilization chamber 1. An article 2 to be
sterilized is inserted into such chamber through a suitable
aperture closable to withstand substantial external pressure.
Preferably the chamber is provided in a metal casing of cylindrical
shape which can be evacuated without collapsing.
Gas such as argon from which the gas plasma is produced is supplied
from a tank 3 in which it is stored under pressure through a
flowmeter 4 to the plasma production conduit 5 connected to one end
of the sterilization chamber 1. Such plasma-production conduit is
subjected to a radio-frequency field created by the electrodes 6,
which may encircle such conduit. A suitable radio-frequency
generator 7 is connected to the electrodes 6 through an impedance
matching network 8 for coupling the capacitative electrodes 6 to an
amplifier of the radio-frequency generator 7. The oscillator and
amplifier of the radio-frequency generator should be capable of
producing up to 300 watts of continuous power as indicated by the
power meter 9.
It may be desirable to cool the plasma generator conduit 5 by
passing cooling water through the cooling jacket 10. The supply of
gas to the plasma generator can be regulated by a valve 11 as well
as automatically by the flowmeter 4; and the flowmeter pressure
gauge 12 will indicate the amount of gas supplied to the
plasma-generating tube 5.
The quantity of gas plasma flowing through the sterilization
chamber 1 is determined, not only by the flowmeter 4 and the valve
11, but also by the pressure in the sterilization chamber 1 through
which the plasma flows. The pressure in such sterilization chamber
is preferably quite low, not exceeding a few millimeters of
mercury. The pressure in the sterilization chamber could be
indicated by a pressure gauge 14.
The supply of gas to the plasma generator from the tank 3 can be
controlled by a shutoff valve 15. When it is desired to use the
apparatus, the article to be sterilized is placed in the
sterilization chamber 1, the vacuum pump 13 is started to evacuate
the chamber, and the shut-off valve 15 is opened to enable gas to
flow from the storage tank 3 through the flowmeter 4 and regulating
valve 11 to the plasma generator 5. It is assumed that the
flowmeter 4 and valve 11 have previously been set to supply the
desired quantity of gas induced by the suction of pump 13 applied
to the sterilization chamber 1.
The radio-frequency generator 7 is then energized and the impedance
matching network 8 is adjusted to minimize reflected power. The
article is subjected to the flow over it of the gas plasma passing
through the sterilization chamber for the period of time required
to effect sterilization. Reductions in microbial population as much
as 99% have been accomplished by exposure of the article to be
sterilized to plasma flow for a period of time as short as five
minutes.
When the sterilization of the particular article has been
completed, the radio-frequency generator 7 is deenergized, the gas
supply valve 15 is closed, and the vacuum pump 13 is stopped or its
connection to the sterilization chamber is severed by a suitable
valve. The sterilization chamber is then vented to atmosphere, the
chamber is opened, and the sterilized object removed from it.
The apparatus shown in FIGS. 2, 3 and 4 is of the type particularly
adapted to the sterilization of artificial lung blood oxygenators.
The apparatus preferably is capable of sterilizing several of such
oxygenators at the same time, three of such oxygenators, 2a, 2b and
2c, being shown in FIG. 2. Such oxygenators are housed in the
sterilization chamber 1' during the sterilization operation. The
apparatus shown in FIG. 2 includes components generally similar to
those described in connection with the apparatus of FIG. 1.
Gas to be excited into plasma is supplied from the supplying tank 3
through the flowmeter 4, to a manifold 5' of the plasma generator.
The amount of gas flow is indicated by the flowmeter pressure gauge
12 and the flow to the sterilization chamber can be initiated and
terminated by operation of the shutoff valve 15. Flow of the gas
plasma through the sterilization chamber 1' is induced by suction
created by the vacuum pump 13. The connection between the
sterilization chamber and the vacuum pump can be severed by closing
valve 16 to avoid the necessity of stopping the vacuum pump between
sterilizing operations. An oil trap 17 may be included in the
suction line to pump 13, and a venting valve 18 for connecting the
sterilization chamber 1' with atmosphere may be provided in the
suction line to the vacuum pump.
Individual pipes 5" connect the manifold 5' to the individual
oxygenators 2a, 2b and 2c, respectively. A radio frequency field
for converting the gas to plasma is produced by the exciters 6' in
each of the gas supply pipes 5". The radio-frequency field is
created by such exciters connected to the radio-frequency generator
7, including an oscillator and an amplifier. The impedance matching
network is adjusted by the radio-frequency tuner 8', and the power
of the radio frequency oscillator is indicated by the wattmeter
9'.
The blood oxygenators to be sterilized are shown in greater detail
in FIGS. 3 and 4. A continuous flow of gas plasma is supplied past
a regulating valve 19, shown in FIG. 2, to a pipe 20 leading to the
interior of the oxygenator. In the arrangement shown in FIG. 3 the
gas plasma is discharged from the interior of the oxygenator
through the plasma exit 21 to the interior of sterilization chamber
1' shown in FIG. 2. The body of the oxygenator includes a
multiplicity of capillary tubes 22 through which the gas plasma
flows slowly to effect the sterilizing action. The resistance to
flow of gas plasma through different oxygenators may vary, and the
opening of valves 19 can be adjusted to equalize the flow effected
through the oxygenators from the common manifold 5'.
Although it is only essential that the interiors of the capillary
passages through the oxygenator be sterile because only such
capillary passages come into contact with blood being oxygenated,
it is desirable to have a completely sterilized oxygenator packaged
in a sealed container to facilitate storage. It is therefore
desirable to provide for flow of gas plasma over the exterior of
the oxygenator at the same time that gas plasma is flowing through
the capillary passages of the oxygenator.
FIG. 3 shows an enclosure 23 for the oxygenator having an inlet 24
and an outlet 25 for flow of gas plasma between the enclosure and
the exterior of the oxygenator to the interior of the sterilization
chamber 1' shown in FIG. 2. Such enclosure is sealed around the
inlet 20 and the exit 21 for the gas plasma flowing through the
interior of the oxygenator. If the enclosure is in the form of a
plastic bag, the openings 20, 21, 24 and 25 can all be sealed to
maintain the sterilized condition both of the interior and of the
exterior of the oxygenator.
In the construction shown in FIG. 4 the gas plasma flows through
the interior of the oxygenator 2' and then over the exterior of the
oxygenator sequentially. In this instance the plasma exit 21' from
the interior of the oxygenator discharges into the interior of the
enclosure 23'. The gas plasma is then discharged from the interior
of such enclosure, after passing over the exterior of the
oxygenator, through the exit 25' to the interior of the
sterilization chamber 1' shown in FIG. 2. With the use of such an
arrangement it is necessary to close only the inlet passage 20
leading to the interior of the oxygenator, and the exit 25' leading
from the enclosure 23'.
By providing continual flow of the gas plasma through the apparatus
and over the surfaces of the article to be sterilized, the
sterilizing operation is effected in a more efficient and
expeditious manner. The sterilizing action of the gas plasma is
also rendered more effective and consequently more expeditious by
exposing the surfaces to be sterilized in a low pressure
atmosphere, so that the gas plasma is more dense. The gas plasma
can be formed from various gases, but preferably is derived from a
monatomic inert gas such as argon, helium or xenon. Such a gas may
be excited to form gas plasma by utilizing known techniques such as
by subjecting it to a radio-frequency field as discussed above, by
a technique such as described in the articles "Analytical
Applications of Electrodelessly Discharged Gases" and "Research
With Electrodelessly Discharged Gases" published in the periodical
Journal of Chemical Education, Volume 43, Number 5, May, 1966 and
Number 6, June, 1966, respectively.
While the specific application of the sterilization process
described above with respect to FIGS. 2, 3 and 4 relates to the
sterilization of oxygenators, the process is particularly
advantageous for the sterilization of various kinds of medical and
hospital equipment. Another important application of the process is
for sterilization of excrement or other waste material which must
be stored for a time, such as in an airplane or a spacecraft,
before being discarded. Such waste material may be ejected from a
spacecraft and should be sterilized before ejection.
* * * * *