Anesthetic Breathing Systems

Question 1

Functions of BS?

Answer 1

PROVIDE suff peak insp flow. (Cyclical spont br)
PREVENT rebreathing of alveolar gasses (CO2)
- app. Dead space should be minumum
PREVENT contamination of insp gasses ny atm air
MAINTAIN low resistance to breathing

Question 2

How can one eliminate CO2 from circuit?

How can one maintain low resistance in circuit?

Answer 2

Washout via gas flow
Absorbtion via soda lime
Control rebreathing via gas flow, valves

Manually compress bag
Ventilator

Question 3

Formula for total dead space (Vd)?

What is the content of the dead space?

Answer 3

Vt = Va + Vd

Vd= portion of Vt not involved in gaseous exchange

= anatomical ( trachea, a/w, bronchi)
+ physiological ( alveoli ventilated bur not perfused)
+ apparatus

CO2

Question 4

Name the 3 types of non- rebreathing sytems?

Answer 4

1. T- piece ( Ayres - jackson rees - mapleson D)
2. Magill
3. Humphrey ADE

Question 5

3 types of T- piece non-rebreathing systems?
Are they more usefull in spontaneous/ controlled ventilation, why?
What would the fresh gas flow be set at if controled ventilation?

Resting minute volume?
Resting alveolar minute volume?

Answer 5

1. Mapleson E - without bag (T- Ayers)
2. Mapleson F -with bag (jackson rees mod)
3. Mapleson D - bag and spring valve (

Wastefull in spontaneous breathing, better in controled venilation - the inspiration :expiration of breathing cycle is set to be 1:2 or 1:3 , this increase the expiratory pause making it possible for low rate of FGF without contamination - efficient system.

1 times that of the pts predicted resting minute volume

70ml/kg/min
0.7 x minute volume

Question 6

Which of these T- systems is best suited for child under 20kgs?

Name 2 other characteristics of the system?

Answer 6

Jackson rees mod (mapleson F)

Simple circuit
Low resistance

Question 7

How does the Millers classification work?

Answer 7

Bi-directional flow
W/o co2 absorb
  - afferent (M-A)
  - efferent (M-DEF, Bains)
  - combinde ( ADE)
Uni- directional flow
With co2 absorb
  - circular

Question 8

How were the best pieces of the t piece and magills combined?

Answer 8

Humphrey ADE

Question 9

Explain the humphrey ADE?

Answer 9

A-mode: spontaneous / T piece
Includes reservoir and bag

D-mode: ventialor/ magill
Only FGF and ventilator

Question 10

What does the coaxial system refer to?

2 disadvantages?

Answer 10

Refers to the Bain system. Tubing within a tubing to deliver frech gas close to pts a/w.

Contamination by expired gasses
Wastefull of FGF

Question 11

Addition of what to the mapleson D creates a circle system?

Answer 11

By inserting 2 unidirectional valves into distal end of system.

Question 12

How is the CO2 eliminated if the system is a re rebreathing one?

Answer 12

By means of a CO2 absorber SODALIME

Question 13

What is the comparison of fresh gas flow: minute ventilation with:
Non rebreathing
Rebreathing

Answer 13

.

Question 14

3 advantage
3 disadvantages
Circle system

Answer 14

Advantages:
Economy of gas and volatile agents
Conservation of heat and moisture of insp gases
Prevention of pollution of the operating room

Disadvantages:
Multiple connection that can mis/disconnect
If one of valves stuck open = hypercapnia
Exp. unidirectional valve stuck closed
= total obstruction - intrathoracic build up
- heamodynamic collapse & pneumothorax

Question 15

What base does CO2 absorbent consist of?

Answer 15

Calcium hydroxide Ca(OH)2

Question 16

What ph- sensitive dye does the CO2 absorbent consist of?

Answer 16

Ethyl violet

Question 17

Give formula for chemical rxn?

Answer 17

Water + CO2 = H2CO3

H2CO3 + 2NaOH. = Na2CO3 + 2 water + heat

Na2CO3 + Ca(OH)2. = CaCO3 + 2NaOH

Question 18

When the rxn is exhausted (soda lime) at what ph will the excess acidic CO2 change the color of the dye?

Answer 18

10.5

Question 19

With which volatile agents does the CO2 absorbent rxn and why?

Which of the absorbents has caused carbon monoxide poisoning?

Answer 19

CF2 containing:
Enflurane; isoflurane; desflurane
Producing carbon monoxide

When absorbent has been dried out and high temp occur within the absorbent.

Baralyme.

Question 20

What breakdown product forms when absorbant rxn with sevoflurane?

What sre the implications there of?

Answer 20

Compound A

Nephrotoxicity (rats) not humans as yet.

Question 21

Compare T -piece to Magills:
Which one is better for
1. Spontaneous breathing
2. Controled ventilation

Answer 21

1. Magills

2. T-piece

Question 22

What is the peak insp flow of normal adult?

Answer 22

25- 30 L /min

Question 23

What is the purpose of Breathing syste, BS?

Answer 23

Delivery of oxygen containing fresh gas from AM to pts a/w.

Enable spontaneous breathing OR controlled ventilation