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Andersen EOGas™ Series 4® Sterilization Efficacy Using
the Three-Hour Sterilization Cycle
The Andersen EOGas Series 4 sterilizer efficacy study was
executed by Andersen Scientific, Inc., using a series of sub-lethal
exposure protocols1, to demonstrate that the three-hour exposure
cycle is capable of delivering a Sterility Assurance Level (SAL) of
10-6.
MATERIALS & EQUIPMENT:
Andersen EOGas Series 4 sterilizer
Calibrated incubator
Shimadzu gas chromatograph and detector
Self-contained biological indicators (min. pop. 1x106)
Standard load (items sterilized in the Series 4 sterilizer):
10 AN10 tubes sealed in polyethylene/polysurlyn pouches
2 patient gowns wrapped in CSR wrap
1 AN42 Sump Pump wrapped in CSR wrap
6 pairs of latex gloves sealed in Seal & Peel packaging
10 cotton-tipped applicators sealed in Seal & Peel packaging
30 PPE Sutures inserted into aluminum pouches, then sealed
in self-sealing paper / plastic pouches
4 hemostats sealed in Seal & Peel packaging
12 syringes sealed in self-sealing paper / plastic pouches
10 glass vials sealed in self-sealing paper / plastic pouches
1 AN2018 Andersen EOGas™ cartridge
2 Humidichips placed in a Humiditube
Items were placed in a 22inch x 36inch 5mil Series 4
PE/Nylon/PE sterilization bag.
METHOD:
Sub-lethal Exposure Studies:
The Andersen EOGas Series 4 sterilizer used in this study was
calibrated to 50°C.
Each sterilization load was seeded with
twenty self-contained biological indicators and processed with
all sterilization parameters remaining constant except time.
Exposure cycles times of 45, 60, 75 and 90-minutes were run on
different days.
All exposed biological indicators were incubated
within 5-minutes of removal from the sterilization bag.
The
average Ethylene Oxide delivered during the four cycles was
18.02g with a standard deviation of 0.34.
RESULTS:
Exposure Time No. Positive No. Negative
t=45 minutes 15 5
t=60 minutes 12 8
t=75 minutes 10 10
t=90 minutes 0 20
Andersen Scientific Protocol No.: 083004S4, Title: Evaluation of the Andersen
EOGas Series 4 Sterilizer: Partial BI exposure & Protocol No.: 090704S4 Title:
Evaluation of the Andersen Series 4 EOGas/Anprolene Sterilizer:
GC Profile
Comparison – 3mil EOGas™ bag vs. 5mil PE/Nylon/PE sterilization bag.
2 Lower sterilization load temperature is result of sterilizer warm-up.
EOGas™ and EOGas 4® are trademarks of Andersen Sterilizers, Inc. ANPROX541XKTSR\
My Documents\EOGas\SERIES 4\studies\EOGas 4 Sterilization Efficacy Study.doc
The self-contained biological indicators—containing a
minimum of 1x106 Bacillus atrophaeus (subtilis) spores,
were rendered sterile after 90-minutes of exposure to Ethylene Oxide.
CONCLUSION:
The sub-lethal cycles suggest that a 6-log reduction can be
achieved during a ninety-minute half cycle exposure cycle.
We can extrapolate this data beyond the first ninetyminutes
in order to determine the minimum achievable
SAL during the full three-hour exposure cycle. Since the Ethylene Oxide within the sterilization bag is not sealed in
a leak-proof system, we have to assume that the Ethylene
Oxide concentration is not constant but is variable. To
better understand this sterilization variable, an Ethylene
Oxide concentration profile was performed under
Andersen Scientific protocol 090704S4—see graph below.
The resulting profile clearly shows that the latter half of
the sterilization cycle (90 to 180-minutes—with a mean
temperature of 46.8°C) has an overall higher Ethylene
Oxide concentration than the initial half (0 to 90-minutes
with a mean temperature 39.6°C2). We can thus conclude
that the latter or second half cycle will deliver a greater
level of lethality than the first half cycle. Since the first
half cycle has already proven a 6-log reduction of the test
organism, we can assume that the second half cycle, will
at a minimum, achieve the same level of lethality for a
combined SAL of 10-6 over the full three-hour exposure
cycle—the requirement for terminally sterilized devices.
Daryl L. Woodman, B.Sc.
Andersen Scientific, Inc., November 16, 2004
Andersen EOGas™ Series 4® Sterilization Efficacy
in a 914mm x 1mm Stainless Steel Lumen
INTRODUCTION:
Hospitals and small doctors offices have faced a difficult
decision when it comes to cleaning, disinfecting and / or
sterilizing flexible and rigid scopes. While Ethylene Oxide
offers the most effective sterilizing agent without damage to
the instrument, the lengthy turnaround times have caused
facilities to move to shorter less effective cycles that can
and often do reduce the life expectancy of the scope. With
the introduction of the new Andersen Series 4 sterilizer,
hospitals and doctors offices know have the best of both
worlds—a cycle that not only sterilizes (rather than
disinfects) but does so in only three-hours.
MATERIALS & EQUIPMENT:
Andersen EOGas Series 4 sterilizer
Calibrated incubator
3x914.4mm length stainless steel tubes with a 1mm lumen
Self-contained biological indicators (min. pop. 1x106)
Standard load (items sterilized in the Series 4 sterilizer):
10 AN10 tubes sealed in polyethylene/polysurlyn pouches
2 patient gowns wrapped in CSR wrap
1 AN42 Sump Pump wrapped in CSR wrap
6 pairs of latex gloves sealed in Seal & Peel packaging
10 cotton-tipped applicators sealed in Seal & Peel packaging
30 PPE Sutures inserted into aluminum pouches, then sealed
in self-sealing paper / plastic pouches
4 hemostats sealed in Seal & Peel packaging
12 syringes sealed in self-sealing paper / plastic pouches
10 glass vials sealed in self-sealing paper / plastic pouches
1 AN2018 Andersen EOGas™ cartridge
2 Humidichips placed in a Humiditube
Items were placed in a 22inch x 36inch 5mil Series 4
PE/Nylon/PE sterilization bag.
ABSTRACT:
Three sections of flexible stainless steel tubing
(914.4mm in length x 1mm lumen) were seeded with a
specialty biological indicator (2.23x106)—mimicking a
contaminated rigid / flexible scope. The microbial death
kinetics of these biological indicators was then
established through a series of partial exposure cycles
where all sterilization parameters remained constant
except time. The resulting survivor curve was then used to
determine the absolute sterilization time. This sterilization
or exposure time was then tested in triplicate to
demonstrate the Series 4 efficacy is sterilizing small and
lengthy lumens.
METHOD:
Survivor Curve:
Using Andersen Scientific protocol 110804.1S41, the stainless
steel lumens were seeded with 2.23x106 Bacillus atrophaeus
spores and processed in four independent exposure cycles.
Exposure times of 0, 60, 90 and 120 minutes were employed to
create the survivor curve. At the conclusion of each exposure
phase, the biological indicators were removed and immediately
processed by Andersen Products, Inc. laboratory to enumerate the
surviving populations. A survivor curve was created by graphing
the surviving population against time. From this graph, the
absolute kill time was established.
Sterility Testing:
Three independent cycles were performed to verify that the
established absolute kill time was sufficient to sterilize 2.23x106
Bacillus atrophaeus spores placed in the center of the lumen.
RESULTS:
Survivor Curve:
The survivor curve indicates that the absolute kill time is less
than 2.5 hours.
Sterility Testing:
The verification sterility studies indicate that the Series 4
sterilizer can sterilize the specialty biological indicators—greater than a 6-log reduction in three hours.
Cycle Number Lumen 1 Lumen 2 Lumen 3
3 hour #1 Pass Pass Pass
3 hour #2 Pass Pass Pass
3 hour #3 Pass Pass Pass
CONCLUSION:
The results from this study indicate that the Series 4 sterilizer can be
used effectively to sterilize long lumens even with diameters as small
as 1mm.
Daryl L. Woodman, B.Sc.
Andersen Scientific, Inc., March 20, 2005
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Ethylene Oxide Residuals Detected on Medical Devices
after Processing in the EOGas™ Series 4®
Three-hour Exposure Cycle
The Andersen Series 4 residual study1 was executed by
Andersen Scientific, Inc., by performing exhaustive
Ethylene Oxide residual analyses on nine different
materials commonly used in medical devices. These
different materials were tested immediately after the Series
4 three-hour sterilization cycle (plus thirty minute gas
purge).
MATERIALS & EQUIPMENT:
Andersen Series 4 EOGas sterilizer
Standard load (items sterilized in the Series 4 sterilizer):
10 AN10 tubes sealed in polyethylene/polysurlyn pouches.
2 Patient gowns wrapped in CSR wrap.
1 AN42 Sump pump wrapped in CSR wrap.
6 Pairs of latex gloves sealed in Seal & Peel packaging.
10 Cotton-tipped applicators sealed in Seal & Peel packaging.
30 PPE sutures inserted into aluminum pouches, then
sealed in self-sealing paper / plastic pouches.
4 Hemostats sealed in Seal & Peel packaging.
12 Syringes sealed in self-sealing paper / plastic pouches.
10 Glass vials sealed in self-sealing paper / plastic pouches.
1 AN2018 EOGas cartridge.
2 Humidichips placed in a Humiditube.
Gas chromatograph and related testing equipment.
TEST MATERIALS:
Latex (glove), Polycarbonate (female luer lock), Nitrile
(glove), Silicone (tubing), Glass, hard PVC (female luer
lock), Polypropylene (pinch clamp), Paper (20lb) and
Metal (Stainless needles).
METHOD:
Exposure Cycle:
A single exposure cycle was performed on the standard load
containing the nine test materials. Each test material was sealed
in an independent self-seal pouch (paper / plastic—AN2310) and
placed in the center of the sterilization load. The average cycle
temperature was 45.5°C with 82.2% relative humidity. The net
Ethylene oxide delivered was 17.63 grams.
RESULTS:
All Ethylene Oxide residual levels were measured using an
exhaustive extraction procedure (worst-case scenario). The
exhaustive extraction procedure is designed to calculate the
total residual within the test material, which is quite different
from a simulated test, where only the residual transferred to the
user is established.
EtO residual levels after a three-hour cycle
with a thirty-minute aeration purge.
Material Device ppm Total Device mg
Metal (Stainless) 0.00* 0.00*
Glass 0.00* 0.00*
Latex 2.17 0.0135
Paper 7.98 0.0075
Silicone 8.09 0.0004
Nitrile 227.57 1.4678
PVC (hard) 310.19 0.1839
Polypropylene 688.36 0.7035
Polycarbonate 1031.21 0.6043
* below the detection limit
CONCLUSION:
The ISO residual limits for medical devices classified as limited
exposure devices (contact up to 24 hours), is defined as <20mg.
In our study, all tested materials where at least twenty-eight
times below this specified level.
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Andersen EOGas™ Series 4® Sterilization Efficacy
Using the Pentax EC3830TL Colonoscope
The Andersen EOGas Series 4 scope challenge study1 was executed by Andersen Scientific, Inc., by seeding a specialty biological indicator within the lumen of a Pentax EC3830TL colonoscope. The biological indicator was carefully placed at the mid-point of the scope’s overall length.
MATERIALS & EQUIPMENT:
Andersen EOGas Series 4 sterilizer
Calibrated incubator
Pentax EC3830TL colonoscope
Specialty biological indicators (population 2.23x106)
Tape measure, 10mm tape, Polyester thread
Thermocouple wire, sterile gloves and scissors
Sterilized media (capped) in 100ml test tubes
Standard load (items sterilized in the Series 4 sterilizer):
10 AN10 tubes sealed in polyethylene/polysurlyn pouches
2 patient gowns wrapped in CSR wrap
1 AN42 Sump Pump wrapped in CSR wrap
6 pairs of latex gloves sealed in Seal & Peel packaging
10 cotton-tipped applicators sealed in Seal & Peel packaging
30 PPE Sutures inserted into aluminum pouches, then sealed
in self-sealing paper / plastic pouches
4 hemostats sealed in Seal & Peel packaging
12 syringes sealed in self-sealing paper / plastic pouches
10 glass vials sealed in self-sealing paper / plastic pouches
1 AN2018 Andersen EOGas™ cartridge
2 Humidichips placed in a Humiditube
Items were placed in a 22inch x 36inch 5mil Series 4 PE/Nylon/PE sterilization bag.
SCOPE BACKGROUND:
The Pentax EC3830TL colonoscope is a two channel lower G.I. video endoscope. The lumen diameters are 2.8mm and 3.8mm, with a working length of 1700mm (66.9 inches). The specialty biological indicator was inserted into the 2.8mm lumen and pulled approximately 850mm (33.5 inches) into the scopes working length.
METHOD:
Seeding of the Biological Indicator into the Scope:
Thermocouple wire was threaded into the scope opening and gently pushed through to the scope tip. Polyester thread was tied to the wire and pulled through the scope until the polyester thread traveled the entire length of the scope. The biological indicator was then tied to the polyester thread at the scope opening and pulled into the scope so that it rested halfway into the length of the device. The polyester thread was then attached to the scope tip with the 10mm tape to prevent further movement of the biological indicator.
Exposure Cycle:
Five independent exposure cycles were performed on separate days—two three-hour exposure cycles and three five-hour cycles. Each cycle was processed with a standard load and a Pentax EC3830TL colonoscope. The average net Ethylene oxide delivered was 17.56grams.
RESULTS:
The five-hour exposure cycle was sufficient to sterilize the biological indicator seeded into the center of the Pentax EC3830TL lumen.
Specialty Biological Indicator (6.23x106) Results
Study No. Cycle Length Control BI Scope BI
1 3 hour Positive Positive
2 3 hour Positive Positive
3 5 hour Positive Negative
4 5 hour Positive Negative
5 5 hour Positive Negative
CONCLUSION:
The results from this study demonstrate that the Series 4 five-hour sterilization cycle can be used to sterile long lumens such as that found in the Pentax EC3830TL colonoscope.
Daryl L. Woodman, B.Sc.
Andersen Scientific, Inc., March 10, 2005 |
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