Cicuits

Question 1

How do non-rebreathing circuits operate

Answer 1

Rely on high FGF to flush expired CO2 from system do it cannot be re-breathed

Question 2

Ayre’s t-piece features (3)

Answer 2

Small animals <10kg
High FGFR
Suitable for IPPV

Question 3

Ayre’s t-piece circuit factor

Answer 3

2.5-3

Question 4

Bain features (4)

Answer 4

larger patients >10kg
Double tubing
High FGFR
Suitable for IPPV

Question 5

Bain circuit factor

Answer 5

2.5-3

Question 6

Check specific to Bain

Answer 6

Check that inner tube not detached from system

Question 7

Magill features (3)

Answer 7

patients >10kg
Lower FGFR than t-piece and Bain
Not suitable for prolonged IPPV

Question 8

Magill circuit factor

Answer 8

1-1.5

Question 9

Parallel lack features (3)

Answer 9

For patients >10kg
More economical than Bain for large patients
- lower FGFR
Not suitable for prolonged IPPV

Question 10

Mini-lack features (3)

Answer 10

For patients <10kg
Lower FGFR
Not suitable for prolonged IPPV

Question 11

Parallel and mini-lack circuit factor

Answer 11

1-1.5

Question 12

Advantages of non-rebreathing circuits (6)

Answer 12

Simple construction
Inexpensive
No soda lime
Lower resistance than RB
- some good for small patients
Inspired gas volume comparable to vaporiser setting
Volatile agent concentration can be altered rapidly

Question 13

Disadvantages of NRB circuits (4)

Answer 13

High FGFR
High volatile agent consumption
Expired moisture and heat loss
- cold inspired gas
Different FGFR required for different circuits

Question 14

Re-breathing circuit features (3)

Answer 14

Requires lower FGFR
Higher resistance
- unsuitable for small patients
Allows conservation of heat and moisture

Question 15

Circle features (7)

Answer 15

High resistance
Soda lime absorbs CO2
For patients <10kg
- more economical than Bain/lack
Preserves exhaled heat and moisture
Less pollution
Cost efficient re. O2 and VA

Question 16

Circle FGFR

Answer 16

100ml/kg/min ~15mins

10ml/kg/min after ~15mins

Question 17

Humphrey ADE features (6)

Answer 17

Adjustable lever and detachable SLC allows use as RB or NRB
Adjustable level allows IPPV
Can use SLC to act as circle
Suitable for wide range of patient weights
Economical
- can be run at low FGFR
Preserves expired heat and moisture

Question 18

Soda lime checks and when should be changed and how

Answer 18

Checked regularly for
- cracks
- exhaustion
Changed at 2/3 exhausted
Gloves and mask worn to change

Question 19

Advantages of RB circuits (4)

Answer 19

Lower FGFR
Economical
- lower O2 and VA consumption
Expired heat and moisture conserved
Less pollution than other systems

Question 20

Disadvantages of RB circuits (5)

Answer 20

Expensive to buy
Higher resistance
Soda lime must be changed regularly
Changes in vaporiser level slow to alter depth
N2O cannot be used in low-flow closed systems

Question 21

Circuit safety checks (6)

Answer 21

Correct assemble
Kinks and damage
Contamination of tubing or bag
Leak test
APL valve open
Check soda lime

Question 22

Reason for use of induction chamber

Answer 22

For small mammals where restrain difficult or overly stressful

Question 23

Features of induction chamber (5)

Answer 23

Airtight
Transparent to allow monitoring
Durable material 
Inlet for VA / outlet for waste gas
High risk of environmental pollution