sterilisers Flashcards
what is the guidance document?
SHTM 2010
daily info for sterilisation
date time started operator cycle no sterilisation temp daily tests performed sterilisation successful machine identified cycle completed successfully Type B - Bowie Dick successful
who carries out the daily and weekly tests?
on site staff
temp
134-137 degrees
time
min hold time 3mins
pressure
pressure equivalent gauge (from atmospheric) 2.05 to 2.35 bar
pressure equivalent absolute (from absolute 0) 3.05 to 3.35 bar
do all sterilisers achieve the same temp and pressure?
yes
daily tests
wipe door seal with clean, disposable, damp, non-linting cloth and carry out any other checks required by the manufacturer, check seal for damage/contamination
check load carrier and chamber for damage/debris/clean
fill and drain water reservoir
when switching power on, check that the ventilation louvers are not covered to avoid overheating
if recommended by the steriliser manufacturer, preheat the steriliser chamber before performing daily tests
record completion of the daily checks in the steriliser logbook
Type B: Bowie Dick (steam penetration) test
record daily sterilisation temps
which extra daily test is required for type B sterilisers?
Bowie Dick (steam penetration) test
sterilisation
a process undertaken to render a steriliser load sterile
sterile
condition of a medical device that is free from viable MOs
weekly tests
Type B - air detector function test and air leakage test
ACT
daily tests
weekly safety checks
weekly safety checks
examine door seal for signs of wear or damage
examine security and performance of the door safety features inc the hinges and locking mechanism as detailed in the MIs
if a fault is detected in the door seal or safety features, ensure this is corrected before carrying out weekly tests or using the steriliser
record satisfactory completion of the weekly safety checks in the steriliser logbook
type N steriliser - how does it work?
‘gravity displacement’
air passively displaced by steam
purified water introduced to the chamber and heated
as it boils and turns to steam, the chamber pressure increases
what instruments can be processed in type N?
rigid steel solid instruments
no wrapped/channeled/lumened
stages in type N
air removal - heating time
sterilising - holding time
condensing - cooling time
what instruments can be processed in a type B?
wrapped and non-wrapped (make sure not to damage wrappings)
channelled and porous instruments
porous loads e.g. cotton swabs
loading recommendations
no overlapping/shadowing
do not overload machine
assemblies should be disassembled beforehand
utilise the available basket/load carrier
type B - how does it work?
porous load/vacuum capable
has active air removal creating a vacuum in the chamber in its initial stage
so steam can contact all surfaces of device
because there is no air in the chamber, the vacuum rapidly draws the steam in from the generator
after sterilisation the machine draws another vacuum for drying, allowing water to vapourise at lower temps
B type - after processing
wrapping intact - ‘sterile’ at point of use
can store in env controlled atmosphere that is free from contaminants and moisture
N type - after processing
‘sterilised’
wrap as soon as remove from steriliser and transport to procedure room
either for immediate use or for non-sterile storage, transport and application
why should instruments be left to cool down after first?
if put hot instrumentation into transport box might cause condensation to build up, potentially damaging wrappings
for sterilisation of wrapped goods what must the residual gas not exceed?
3.5 ml per 100ml of condensed steam
air detector incorporated as a safety device to monitor the adequacy of the air removal process
what is residual gas?
remaining air and gases carried in the steam after the air removal stage
type S
products specified by the manufacturer of the steriliser inc non-wrapped solid products and ≥1 of the following: porous products, small porous items, hollow load products type A, hollow load products B, single wrapped products, multiple layer wrapped products
vacuum pump/some other active method to remove air from the chamber and load
what should dental handpieces be sterilised using?
a vacuum process
type S
obligations under H+S and Consumer Protection Act
ensure equipment:
- complies with safety requirements
- installed and maintained appropriately
- validated and routinely tested
- operated only in accordance with MIs and by properly trained operators
water and steam quality
good quality water to make good quality steam
water low in minerals to prevent depositing minerals onto the instruments (limescale) and making them harder to clean
waters recommended by manufacturers for use in sterilisers
= pure water RO distilled sterile deionised
basic stages of operation of Type B
1 - air removal (negative pulsing) 2 - steam admission (positive pulsing) 3 - equilibration 4 - sterilisation 5 - drying 6 - air admission (0.2micron fitted inlet)
type B : 1 - heating up of water and air removal
water enters an external boiler known as a steam generator to a pre-determined level from the clean tank
heating element switched on (generator heating water)
machine is pulling a pre-determined vacuum (neg pressure)
as water reaches bp, steam generated. Element stays on until the steam reaches sterilising temp
once vacuum achieved to a pre-determined level the steam generator injects steam - 3 times (neg pulsing)
on 3rd injection of steam vacuum cuts off and the steam is allowed to build up in stages (positive pulsing) to the sterilising temp and pressure
type B: 2 - sterilising
once all air removed and temp/pressure achieved it is held for a holding time (min 3mins)
sterilising temp controlled by a combination of pressure transducers and sump and chamber temp sensors
at end a valve opens to allow the condensate steam to enter the dirty tank
Type B: 3 - drying
B unlike N has a proper drying stage
pulling a vacuum whilst keeping the chamber hot - remove steam
some sterilisers do vacuum pulses at this stage whilst others only pull the one deep vacuum
negative pressure
Type B: 4 - cooling (air admission)
after a predetermined time the vacuum is switched off and the chamber allowed to cool
when the chamber reaches atmospheric pressure and a set temp (typically 80 degrees) the door is unlocked and can be opened
mass
amount of matter an object contains (kg)
weight
force caused by gravity on an object (N)
- weight of a mass 1kg approx 10N
pressure
force acting normally per unit area
1Pa = 1N/m2
atmospheric pressure
often given in millibars where standard sea level pressure defined as 1000mbar = 1 bar
when we speak about vacuum for sterilisation normally use mbars
when we speak about positive pressure we use bar e.g. 2.3 bar
automatic controller
device within the steriliser that controls the sterilisation cycle
to ensure it is working - ACT
how often should ACT be done?
daily: either using the sterilisation cycle parameter values recorded on the printout or electronic data logger, or by manually observing and recording the cycle parameters if there is not a suitable recorder fitted
weekly: manual ACT
can the ACT be done when sterilising a standard load?
yes
unless also carrying out a steam penetration test for a vacuum steriliser at the same time
- usually 1st cycle of day
when must a daily manual ACT be carried out?
if a suitable recorder is not fitted
as normally would just be done daily with steriliser recorder - a printer or electronic data logger
ACT using a recorder
run a sterilisation cycle with a standard load or an empty chamber (the chamber must be empty if also carrying out a steam penetration test in a vacuum steriliser)
at the end of the cycle, check printout/data logger to ensure that the recorded cycle parameters (temp, pressure, hold time) are within the specified range for the cycle and comparable to the values obtained at validation
- keep a record of the values
if ACT unsatisfactory (i.e. recorded temp, pressure or hold time are not within the specified range for the cycle), record the test as a fail and do not use until fault resolved
- return any instruments that were loaded in the steriliser to the start of the decon cycle
sign logbook
how often should the Bowie-Dick (steam penetration test) be carried out?
daily
which type of steriliser needs Bowie-Dick (steam penetration test) ?
type B
steam penetration test types
Bowie and Dick test pack - chemical indicators
Helix/hollow load test
Bowie and Dick test pack
chemical indicators
test sheet fitted between hundreds of sheets of paper
yellow - dark blue
if air removal part of cycle not performing correctly - yellow spotting on the sheet
pink coloured circle on outside changes colour once processed - purple
how to carry out Bowie-Dick (steam penetration test)
place on bottom shelf of load chamber start cycle cycle much shorter and doesn't have same drying time remove pack open, find test sheet identify colour change
Helix/hollow load test
tests for steam penetration by letting us know that the steam was able to contact the chemical indicator by travelling through the entire length of tubing attached to the device
is a strip inserted into the pack when processing instruments acceptable?
no - not considered to show us anything except a pack of instruments has been through a sterilisation cycle - not a steam penetration test
main fct of steam penetration test
test steam penetration, also informs temp achieved, adequate air removal
to show steam will rapidly and evenly penetrate a test device that is similar to the intended load
where can you get information on recommended steam penetration test device and indicator?
MIs
carrying out a steam penetration test
start of day - select usual cycle and perform test with chamber empty apart from the test device, following test device MIs
record pass/fail in steriliser logbook
if fail - repeat. A 2nd unsatisfactory test result confirms fault
- arrange for a MP (sterilisers) to investigate and don’t use until resolved
which steriliser needs an air leakage test?
type B
how often should the air leakage test be carried out?
weekly
other names for air leakage test
vacuum leak rate
chamber integrity test
vacuum test
why is it important air doesn’t leak into the chamber in a type B?
if air leaks into chamber at a higher rate than specified by manufacturer, it might interfere with steam penetration into load, and as air will not have passed through the bacteria retentive filter, risk of recontamination of load
air cannot be heated the same way as steam and therefore cannot achieve the required temp, or easily maintain that temp either
purpose of the air leakage test
verify that:
during negative pressure stage it removes all air within the chamber at the start of the cycle
when reach low pressure set point and vacuum pump stops operating
- machine continues to maintain same pressure and no air is able to enter the chamber from any part of the machine
= verifies that all valves and connections made to the chamber are sealing properly, the vacuum pump is capable of reaching the low set-point that we require and that the door is also sealing onto the chamber correctly
carrying out an air leakage test
chamber must be cold, dry, empty
close door, machine locks it and cycle starts
machine approaches set point pressure
- then stabilises for 5mins(potential for pressure fluctuations), then measures any differential in the pressure over the following 10mins
- max permitted change is 13mbar over 10mins or 1.3mbar per min. Max differential <2%
once 10min over - see pressure start to increase as valve opens to allow filtered air back into the chamber
- happens at beginning and end of cycle - ensure air can’t be drawn in while cycle running (contamination)
- check machine cycle data - displays all relevant values
record results in steriliser logbook
automatic air leakage test
if an automatic test is available, do once a week (FMIs), generally with a cold chamber
preferable to have a steriliser that is capable of performing an automatic test as otherwise a test person(decon) is required to perform a weekly manual test
note that some manufacturers specify that an air leakage test is carried out each day before steam penetration test
why does the temp remain low in an air leakage test?
temp remains low as not a stage that has steam in it
how does machine display pressure in an air leakage test?
- pressure absolute displays atmospheric pressure as 1 bar (1000mbar)
- machine displays it as pressure gauge, showing atmospheric pressure as 0
- removes air until reaches set point -0.87bar or -870mbar
what will any air leakage cause?
any air leakage will cause a change in the chamber pressure
if user cannot perform an ADFT, what needs to be done?
require a TP(D) to visit weekly to do it
- will add significantly to costs so check before purchase
which steriliser requires an ADFT?
B type
freq of an ADFT?
weekly
what machines are fitted with an air detector?
safety device
sterilisers that actively remove air from the load before sterilisation (e.g. using a vacuum pump)
what is an air detector?
generally a temp probe (/pressure transducer)
in a difficult to reach part of the chamber, potentially at the bottom of a tube attached to the chamber
positioned somewhere that will be difficult to remove air from - the resulting presence of air would mean that the temp at the probe would be lower than that of the temp the chamber probe would be measuring from the steam
- temp differential checked and if it is outwith limits the cycle will fail
why is air in the chamber detrimental?
doesn’t maintain temp the same way that steam does, and is also much harder to heat
if air present during cycle could mean not every part of chamber and load being processed will reach required temp for required time - could allow MOs to survive
how much air is allowed to enter in ADFT?
small measured bleed of air is allowed to enter the chamber
recommended rate 11mBar/min - v small - approx 0.5% of the pressure that we are working with
- even v small amount of air has potential to affect cycle set points
after an ADFT
retrieve data from machine
record in steriliser logbook
which cycle can be used for the ACT?
1st production cycle
B type ACT things to record
date, time, cycle number, operator
more data - cycle more complex
record info for: vacuum stage at start, steam introduction and sterilisation stage and post-vacuum/drying stage. Time for each stage
record readings at each peak, low pressure and high pressure
- pulsing: record low pressure, high pressure and temp
+ pulsing: record low pressure, high pressure and temp
sterilisation temp and pressures - at start of stage and then at 1min intervals until it finishes
N type ACT things to record
date, time, cycle number, operator
record e.g. cycle times and sterilisation temps, times for diff stages
record temp and pressure (if it is displayed) of the sterilisation stage at 1min intervals
after create own ACT record can retrieve the machine cycle data as well and check both records against each other
vacuum steriliser - quarterly
weekly safety checks Bowie Dick test air leakage test ADFT calibration of test instruments ACTs and verification of calibration small load thermometric test calibration checks (post-testing) produce cycle graphs to make sure all cycle set points are being achieved
sterilisers - what must be done annually?
annual validation
