breathing circuits

Question 1

define an open breathing circuit
reservoir?
rebreathing?
examples?

Answer 1

patient exchanges gas with atmosphere
no reservoir
ex) insufflation, simple face mask, NC, open drop

Question 2

define a semi open breathing circuit
reservoir?
rebreathing?
examples?

Answer 2

FGF >MV
no rebreathing
yes reservoir
ex) maples (FGF dependent on design), circle (FGF > MV)

Question 3

define a semi closed breathing circuit
reservoir?
rebreathing?
examples?

Answer 3

FGF <MV
allows partial rebreathing
unidirectional valves increase aw resistance
ex) circle system

Question 4

define a closed breathing circuit
reservoir?
rebreathing?
examples?

Answer 4

very low FGF, APL closed, change in gas concentration very slow
complete rebreathing
yes reservoir
ex) circle system with very low FGF and APL closed

Question 5

what do you do about this wave form

Answer 5

increase FGF >MV (dont increase MV)
replace absorber

Question 6

review parts of circle system

Answer 6

unique unidirectional valves in this system

Question 7

circle system can be (open v closed)

Answer 7

semi open or semi closed (FGF above or below MV)
can also be closed but not usually done

Question 8

advantages of circle system

Answer 8

consistent amount of inhaled gas
maintains heat and humidity
low resistance (not as low as mapleson circuits)
can be used as semi open, semi closed, or closed
minimizes OR pollution

Question 9

disadvantages of circle system

Answer 9

multiple places where d/c can occur
less portable than non rebreathing circuits
unidirectional valves can malfunction (stuck open valve- rebreathing, stuck closed exp valve- aw obstruction)

Question 10

ASTM says reservoir bag cannot exceed internal pressure

Answer 10

> 60cmH2O

Question 11

unidirectional valve failure:
inspiratory valve stuck open v
stuck closed
expiratory valve stuck open v
stuck closed

Answer 11

Question 12

if unidirectional valve is stuck open, what will you see on capnograph (and how to tx)

Answer 12

make it a semi open system (increase FGF)

Question 13

Mapleson A

Answer 13

best for spontaneous ventilation
(FGF away from patient)

Question 14

Mapleson B

Answer 14

Both FGF and APL near patient

Question 15

Mapleson C

Answer 15

no corrugated tubing

Question 16

Mapleson D

Answer 16

best for controlled ventilation
(opposite of A, only one where APL is away from patient)

Question 17

Mapleson E

Answer 17

Ayres T piece
(no APL or reservoir bag)

Question 18

Mapleson F

Answer 18

no APL

Question 19

components present in mapleson circuits

Answer 19

reservoir bag
fresh gas inlet
corrugated circuit tubing
APL valve
mask

Question 20

components not present in mapleson circuits

Answer 20

unidirectional valves
CO2 absorber

Question 21

two maplesons without APL

Answer 21

E and F

Question 22

advantages of mapleson circuit

Answer 22

less aw resistance (good for peds)
convenient
easily scavenged (varies by type of circuit)
bain circuit prevents heat loss

Question 23

disadvantages of mapleson circuit

Answer 23

increased apparatus dead space
requirers high FGF to prevent rebreathing
loss of heat and humidity
inefficient use of inhaled anesthetics
risks of environmental pollution
unrecognized kinking of fresh gas hose in bain circuit

Question 24

best maplesons for spontaneous ventilation (and worst)

Answer 24

all dogs bite (A>DFE>CB) best
worst: B

Question 25

best maplesons for controlled ventilation (and worst)

Answer 25

best: (DFE>BC>A) dont be arrogant
worst: A

Question 26

key facts about this mapleson system

Answer 26

-bain system (modified mapleson D)
-useful for spontaneous and controlled ventilation
-to prevent rebreathing, FGF should be 2.5x MV

Question 27

pethick test for bain circuit

Answer 27

1. occlude elbow at patient end of circuit
2. close APL
3. use O2 flush valve to fill circuitt
4. remove occlusion at elbow while flushing circuit

-if the inner tube is patient, venturi effect will cause reservoir bag to collapse
-if inner tubing is occluded, reservoir bag will remain inflated. not safe to use.