breathing circuits Flashcards
define an open breathing circuit
reservoir?
rebreathing?
examples?
patient exchanges gas with atmosphere
no reservoir
ex) insufflation, simple face mask, NC, open drop
define a semi open breathing circuit
reservoir?
rebreathing?
examples?
FGF >MV
no rebreathing
yes reservoir
ex) maples (FGF dependent on design), circle (FGF > MV)
define a semi closed breathing circuit
reservoir?
rebreathing?
examples?
FGF <MV
allows partial rebreathing
unidirectional valves increase aw resistance
ex) circle system
define a closed breathing circuit
reservoir?
rebreathing?
examples?
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
what do you do about this wave form
increase FGF >MV (dont increase MV)
replace absorber
review parts of circle system
unique unidirectional valves in this system
circle system can be (open v closed)
semi open or semi closed (FGF above or below MV)
can also be closed but not usually done
advantages of circle system
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
disadvantages of circle system
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)
ASTM says reservoir bag cannot exceed internal pressure
> 60cmH2O
unidirectional valve failure:
inspiratory valve stuck open v
stuck closed
expiratory valve stuck open v
stuck closed
if unidirectional valve is stuck open, what will you see on capnograph (and how to tx)
make it a semi open system (increase FGF)
Mapleson A
best for spontaneous ventilation
(FGF away from patient)
Mapleson B
Both FGF and APL near patient
Mapleson C
no corrugated tubing
Mapleson D
best for controlled ventilation
(opposite of A, only one where APL is away from patient)
Mapleson E
Ayres T piece
(no APL or reservoir bag)
Mapleson F
no APL
components present in mapleson circuits
reservoir bag
fresh gas inlet
corrugated circuit tubing
APL valve
mask
components not present in mapleson circuits
unidirectional valves
CO2 absorber
two maplesons without APL
E and F
advantages of mapleson circuit
less aw resistance (good for peds)
convenient
easily scavenged (varies by type of circuit)
bain circuit prevents heat loss
disadvantages of mapleson circuit
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
best maplesons for spontaneous ventilation (and worst)
all dogs bite (A>DFE>CB) best
worst: B
best maplesons for controlled ventilation (and worst)
best: (DFE>BC>A) dont be arrogant
worst: A
key facts about this mapleson system
-bain system (modified mapleson D)
-useful for spontaneous and controlled ventilation
-to prevent rebreathing, FGF should be 2.5x MV
pethick test for bain circuit
- occlude elbow at patient end of circuit
- close APL
- use O2 flush valve to fill circuitt
- 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.
