Sterilisation 4

Question 1

autoclave, mechanism of heat transfer?

Answer 1

Latent heat of vaporization- steam comes into contact with the object in the chamber and condenses round the object as it does this theres a small vacuum round the product that sucks in more steam and the heat is transferred from the steam to the product- as a result this creates more of a vacuum
This continues till the heat is the same

Question 2

what are the critical aspects of autoclaving?

Answer 2

Air Removal- to replace the air with steam to pressurize the container if you don’t you’re unlikely to get temperatures above 100 degrees.
Saturated Steam- has a defined moisture content
Steam under pressure- only when the steam is generated under pressure will it get hotter than 100 degrees which we need to remove endospores

Question 3

what would happen if you dont remove the air?

Answer 3

unlikely to get temperatures above 100 degrees

Question 4

why does the steam need to be under pressure

Answer 4

only when the steam is generated under pressure will it get hotter than 100 degrees which we need to remove endospores

Question 5

what is filtration sterilisation

Answer 5

passage of fluid across a filter, removing contaminating solutes

Question 6

what is a filter voidage

Answer 6

no direct passage from the top to the bottom- like a maze

Question 7

what has happened with a filter voidage if there’s an accumulation above the filter? what does this indicate?

Answer 7

the voidage is full

filter capacity

Question 8

pore size of a depth filter

Answer 8

no fixed pore size

Question 9

mechanism of retention in depth filters?

Answer 9

intertial impaction- where the particles collides with the matrix and gets retained

Question 10

TF: depth filters have a high retentive capacity.

Answer 10

true

Question 11

depth filters are ____ expensive than screen filters

Answer 11

less

Question 12

can depth filters guarantee sterility

Answer 12

no

Question 13

pore size of screen filters?

measured in?

Answer 13

uniform poor size- highly engineered

measured in microns

Question 14

mechanism of retention with screen filters?

Answer 14

direct interception

Question 15

TF: screen filters aren’t easily blocked

Answer 15

false

Question 16

why are screen filters fragile

Answer 16

they’re brittle

Question 17

screen filters cost ___ times more than depth

Answer 17

5

Question 18

is sterility guaranteed with screen filters? why?

Answer 18

yes
0.22um
smallest known bacteria is 0.4um

Question 19

how are filtered validated?

Answer 19

bubble test

challenge filter test

Question 20

direct proportion between the amount of pressure applied by the bubbles and the….

Answer 20

porosity of the filter

Question 21

explain the bubble test

Answer 21

put their filter into an apparatus, from the underside they put gas, then increase the amount of pressure till bubbles come up in a steadily
• Direct proportion between amount of pressure applied and the porosity of the filter

Question 22

explain the challenge filter test?

Answer 22

challenge the filter with the smallest bacteria and see if it filters it out 
Brevundimonas diminuta (0.4um)

Question 23

what is the smallest bacteria?

Answer 23

Brevundimonas diminuta (0.4um)

Question 24

how does moist heat cause death?

Answer 24

Death by protein coaggulation and hydrolysis more rapid

Question 25

what types of products is moist heat used for?

Answer 25

aqueous products / devices/ dressings

Question 26

how does dry heat cause death?

Answer 26

Death by oxidative processes- lot longer

Question 27

what types of products is dry heat used for?

Answer 27

dry powders / oil preparations / glassware and instruments

Question 28

technology for dry heat sterilisation?

Answer 28

dry heat ovens

sterilising tunnels

Question 29

what is a dry heat oven. used for _____ heating

Answer 29

essentially like a domestic oven- tend to be for more batch heating

Question 30

what is a sterilising tunnel? is a _____ process

Answer 30

continuous process- product slowly moves through dry heat

Question 31

3 mechanism of heat transfer

Answer 31

conduction
radiation
convection

Question 32

if the loading pattern is correct what should we get

Answer 32

good air circulation

Question 33

dry heat cycle?

Answer 33

drying
heating
exposure
cooling

Question 34

what’s the longest part of the dry heat cycle? how long does it take?

Answer 34

cooling

16 hours

Question 35

what type of steam do we want for autoclaving?

Answer 35

dry saturated NOT wet or superheated steam

Question 36

will wet steam sterilise the product

Answer 36

yes but decrease the quality

Question 37

superheated steam has a lower ______ content. will kill by….

Answer 37

moisture

oxidative kill not hydrolytic

Question 38

what is the issue with superheating steam killing by oxidation?

Answer 38

much slower process, so will take longer

Question 39

in autoclaving what should the temperature be maintained within

Answer 39

+-5 kelvin of the limit

Question 40

autoclaving time of contact must be sufficient enough to give what?

Answer 40

SAL