Specifications for temperature and humidity in sterile storage - wfhss

© STEAM Consulting 2010

Where’s the evidence?

Presented by Terry McAuleySterilisation & Infection Prevention & Control [email protected]

� Why is maintenance of temperature and humidity conditions important for maintenance of sterility?

� Is there a real risk of contamination of sterile � Is there a real risk of contamination of sterile items when storage conditions exceed specified requirements?

� How do I manage in situations where temperature and/or humidity are noted to be outside acceptable limits?


� Type of packaging material

� Method of wrapping

� Method of sealing� Method of sealing

� Storage conditions� Temperature, humidity, atmospheric pressure changes,

bioburden

� Handling & storage duration


� Porosity� Pore size▪ <5µ

� Air resistance compatible with method of wrapping & sealing

Containers� Containers� Inner wrap increases barrier efficacy

� Pre-formed Sterile Barrier Systems� Paper highly resistant

� Quality varies

� Method of sealing� de Brujn & Kastelein (1999)


� Sterile Barrier System – Sterilisation wrap

� Envelope

� Parcel

� Single or double

� Sequential or simultaneous

� Pre-formed sterile barrier system

� Single or double


� Sterile Barrier System – sterilisation wrap� Torturous path

� Pre-formed Sterile Barrier Systems� Pre-formed Sterile Barrier Systems� Heat seal

� Tape

� Self seal ▪ Up to 30% self sealing pouches incorrectly sealed

� de Brujn & Kastelein (1999)


� Increased levels of bioburden increases the risk of

pack contamination

Bioburden increases with� Bioburden increases with

� Ambient conditions

� Number of people present

� Number of handling episodes

� Time


� Increasing temperature alone is unlikely to affect sterility

However:� RH typically decreases as temperature increases

▪ Excessively dehydrated packaging is also at risk of compromise▪ Excessively dehydrated packaging is also at risk of compromise

� Warmer conditions more conducive to microbial growth

� Stability of some materials can be affected at increased temperatures


� The amount of water vapour in air

� Warm, moist conditions encourage microbial

proliferation

� Water facilitates the passage of microorganisms

through packaging materials by wicking


� Fluctuations in pressure can:� Affect dew point

� Cause packs to ‘breathe’

� Pressure changes can occur� Pressure changes can occur� Handling or storage causing compression of packs

� Transport in an elevator

� Moving to a more positive pressure environment such as an Operating Room

� Weather changes� Dunkelberg & Schmelz (2009)


� Cooling

� 30 minutes minimum recommended post steam sterilisation

� ANSI/AAMI ST-79

� Cooling most critical phase

� de Brujn & Kastelein (1999)



de Brujn & Kastelein (1999)

� Number of episodes of handling

� Exposure to events

� Bioburden levels, pressure changes, compression & time are also � Bioburden levels, pressure changes, compression & time are also

events

� Dunkelberg & Wedekind (2004)


� Developed by a committee with diverse backgrounds and agendas

� ‘Consensus of experts’ rather than evidence � ‘Consensus of experts’ rather than evidence driven � No evidence based review of recently published

literature


� AS4187 - 1994

� Temperatures 22-240Celsius

� Relative Humidity 35-68%

▪ Reference made to AS1668.2▪ Reference made to AS1668.2

� AS4187 - 1998

� Same as 1994 edition

� AS/NZS4187:2003

� Temperatures changed to 18-220Celsius

� RH unchanged


� Air-conditioning & ventilation standards � AS1668

� Architects / Building codes� Australasian Health Facility Design Guidelines� Australasian Health Facility Design Guidelines

� Building Code of Australia

� Various international pharmacopoeias

� Good manufacturing practice guides

� Commercial manufacturer accelerated ageing and environmental challenge testing for sterile medical devices??


Country Document Temperature range

(0C)

Relative Humidity(%)

Australia AS/NZS4187:2003 18-22 35-68

Australasian Health Facility Guidelines <27 for storage areas

Not specified

Canada PIDAC 18-20 30-60

CSA [18-20] 30-70

United Kingdom HBN 13 16-21 30-60


Steering Committee for Decontamination of Reusable Invasive Medical Devices

18-21 35-60

HTM2010 Part 5 18-22 35-75

United States Centers for Disease Control Avoid extremes Avoid extremes

AORN <24 <70

ANSI/AAMI ST79:2006 <24 <70

� Relative humidity is a measure of the actual

amount of water vapour in the air compared to

the total amount of vapour that can exist in the

air at its current temperature and pressure. air at its current temperature and pressure.

� Expressed as a percentage.


1 kg of

dry air

can hold


can hold 7.76g

moisture

As temperature increases RH decreases providing

pressure and moisture content remain static

� Dew point and relative humidity are related.

� Dew point is measured in degrees of

temperature. It is the temperature to which the temperature. It is the temperature to which the

present air would have to be lowered to become

saturated... to be holding all the water it can hold.


� Dew Point� The temperature to which air must cool to release its water at a given

barometric pressure

▪ Rapid fluctuation of ambient temperatures at a certain RH & pressure

▪ If temperature drops from 220C to 180C at RH 78% condensation will occur▪ If temperature drops from 220C to 180C at RH 78% condensation will occur

� At RH 68% and 180C the temperature would have to drop to 120C to reach dew point

� At RH 68% and 220C the temperature would have to drop to 15.80C to reach dew point

� At RH 60% and 250C the temperature would have to drop to 17 degrees to reach dew point


A high relative humidity indicates

that the dew point is close to the that the dew point is close to the

current air temperature


� Double packaging

� Use of impervious plastic covers

Storage in closed plastic containers� Storage in closed plastic containers

� Temporary or permanent relocation of sterile items

� Minimise amount of items or duration of storage� CSA (2007)


� Changes to Standard or guidelines� Increase temperature limit to 24-250C

� Relative Humidity limits to 30-70%▪ Must be conscious of dew point

� Daily recording of temperature and humidity in storage � Daily recording of temperature and humidity in storage environments� Implementation of a corrective action plan when results deviate from acceptance

criteria

� Packaging manufacturers to provide guidance on appropriate temperature and humidity conditions for their products� Environmental challenge studies according to a standardised protocol?


� Over 60 references were sourced in the preparation of my original paper

� If you would like a copy of the paper I have published on this topic

� If you would like a copy of the paper I have published on this topic http://www.publish.csiro.au/view/journals/dsp_journal_f

ulltext.cfm?nid=241&f=HI09020

Or email me and I will send you the link


Cable Beach, WA

Thank you

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Specifications for temperature and humidity in sterile storage - wfhss

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