Anesthesia delivery systems

Question 1

Open system

Answer 1

No reservoir bag, valves or rebreathing of exhaled gas
2 types:
*insufflation/blow by: NC, blow-by tent
*Open drop: Schimmelbush mask

Question 2

Insufflation/blow by

Answer 2

NC, simple

disadvantages: *no ability to assist vent
* no control of anechoic depth/FiO2 *environmental pollution

Question 3

Open drop

Answer 3

Schimmelbush mask–ether mask (cloth saturated with ether)
simple, low cost, portable
Disadvant: poor control of anesthesia, accumulation of CO2, hypoxia risk, can control vent, and OR pollution

Question 4

Semi-open system 5 components

Answer 4

1. Facemask or ETT
2. Spring loaded pop off valve (APL)
3. Reservoir inlet (tubing)
4. Fresh gas inlet
5. Reservoir bag

Question 5

Semi-open group 1

Answer 5

Mapleson A
APL located near face mask
FGF located at opposite end
*most efficient during Spont breathing, only requires 1 x the MV to prevent rebreathing of CO2
*least efficient during controlled vent and can requires FGF 20L/min to prevent rebreathing

Question 6

Semi-open group 2

Answer 6

Mapleson B C
APL and FGF near face mask
*spont least efficient
*controlled middle efficient

Question 7

Semi-open group 3

Answer 7

Mapleson D, E, F
FGF located near face mask 
APL at opposite end
*opposite of A 
*spont middle efficient require 2.5xMV of FGF
*controlled most efficient

Question 8

CO2 rebreathing will depend on

Answer 8

1 *FGF
2 *MV 
3 *type of vent
4. VT
5. RR
6. I:E
7. duration of expiratory pause
8. peak inspiratory flow rate
*in notes others in book

Question 9

Anesthesia bag vs ambu

Answer 9

anesthesia-can tell resistance compliance and can see expiration
ambu: self inflating can’t tell in exhaling
modified mapleson A..has non-rebreating valve—so only get fresh gas
*can still ventilate if loose gas source because of self refilling

Question 10

Mapleson D

Answer 10

FGF located near face mask APL at opposite end

• spont middle efficient require FGF2-3xMV
• controlled most efficient FGF1-2xMV

Question 11

Mapleson E

Answer 11

modification of T piece
No reservoir bag or Pop off valve
spont FGF 2-3xMV

Question 12

Mapleson F

Answer 12

Jackson-Rees
modification of E with adjustable pop-off valve at end of reservoir bag
popular in peds

Question 13

Bain circuit

Answer 13

Modification of D
FGF is the corrugated tube
allows for fresh gas to warm up
preserves heat and humidity 
can bee use for controlled(1-2mv) or spent vent(2-3MV)

Question 14

Mapleson advantages

Answer 14

*simple *light weight *can provided + press vent *low resistance *portable
if using inhaled anesthetics—more predictable and less room pollution

Question 15

Mapleson disadvantages

Answer 15

requires FGF calculations: varies for type and mode
control of anesthetic depth is variable–diluted as FGF goes up
if FGF is not maintained possibility of CO2 buildup and rebreathing
minimal rebreathing of other gases
poor conservation of heat and humidity

Question 16

circle system 7 components

Answer 16

1. FGF source
2. insp and expi unidirection valves
3. insp and expi limbs and corrugated tubing
4. Y-piece connector
5. Adjustable pressure–APL valve, pop off valve
6. Reservoir bag
7. CO2 absorber

Question 17

Circle system

Answer 17

can be used as:
semi-open– with increased FGF
semi-closed–some rebreathing, need CO2 absorber)
closed–rebreathing all, need CO2 absorber, only providing enough O2 for pts needs
*all this depends on APL valve

Question 18

Unidirectional valves

Answer 18

gas flowing into valve raises disc form its seat and passes through
reversing gas causes disc to contact its seat, stop flow
the guide prevents lateral/vertical displacement of disc
Transparent dome allows for observation of disc—can unscrew and clean if gets sticky

Question 19

Reservoir bag

Answer 19

neck 22mm
accummulates exhaled gas
visual/tactile to observe spont respiration

Question 20

APL valve

Answer 20

pressure relief
when pressure gets to where ever APL is set excess pressure (gas) goes to scavenge
*closing valve increased pressure in system
*provides control of pressure in system
*spont- valve open, close some if reservoir bag collapses
*assisted vent (not ventilator mode)- valve partially open–careful and frequent adjustments necessary
*mech vent-valve closed

Question 21

O2 flush

Answer 21

gas flow through the absorber

Question 22

circle arrangement rules

Answer 22

1. unidirectional valves must be located btwn pt and reservoir bag, on both insp and expo limbs
2. FGF cannot enter system btwn expiratory valve and pt
3. APL valve cannot be located btwn pt and inspiratory valve

Question 23

Semi Open circle

Answer 23

not used much, occasionally for sedation–mask placed over face to increase FiO2, ex preO2

• no rebreathing occurs
• high FGF for eliminate rebreathing
• no conservation of wasted gas, APL open all the way

Question 24

Semi-closed circle

Answer 24

Most commonly used*requires low FGF

• conserves some heat and gases
• some rebreathing except CO2
• APL is partially closed and adjusted as needed

Question 25

Closed circle

Answer 25

3rd world countries

• FGF exactly matches metabolic needs–O2 flow = 200ml/min
• total re-breathing of gases after absorption of CO2
• APL is closed
• *O2 consumption: VO2= 10xkg^3/4

Question 26

Circle system advantages

Answer 26

• stability of inspired gas
• conservation of heat and moisture
• prevention of OR pollution
• can be used with fairly low flows and no rebreathing of CO2
• can scavenge waste gases

Question 27

Circle system disadvantages

Answer 27

complex design
has at least 10 connections 
potential of malfunctioning valves
increased resistance to breathing 
less portable than mapleson

Question 28

Circle system check

Answer 28

leak test–btwn every case
set flow to zero, occlude Y piece, close APL, pressurize circuit to 30cmH20 using O2 flush, ensure pressure hold for 10 sec, listen of sustained press alarm, open APL to ensure pressure decreased

Question 29

Flow test

Answer 29

attach breathing bag to Y piece, turn on vent, assess integrity of unidirectional valves