4. Breathing System (cont'd)
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4.4
Perform leak test - Bag / APL valve circuit
- Set selector switch to Bag/APL - close APL valve
and occlude Y-piece
- Inflate bag with O2 flush to 40 cm H2O
- circuit pressure holds for > 10 secs
- ventilator bellows does not move at all
- Sustained pressure alarm sounds
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numerous leak sites possible
- poorly connected /obstructed FGF hose
- CO2 canisters not locked into position
- faulty canister seals or granules are preventing
a good seal
- CO2 drain plug partially open
- unidirectional valve domes loose
- O2 sensor not firmly seated in port or
sensor housing is cracked
- pressure sensing tubing from gauge is not tightly
connected
- leak in rebreathing bag, circuit hoses
- unused sampling ports not capped
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- faulty selector switch - allows cross-over of gas
into ventilator circuit
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4.5 Check
APL valve and scavenging system
- With APL valve still closed and circuit occluded,
squeeze inflated bag until pressure reaches
approx. 70 cm H2O
- APL valve partially releases and
reservoir bag on scavenger fills
- High pressure alarm sounds
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- improperly adjusted APL valve - set to release
either too high or too low
- no alarm - upper limit set too high
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- Open APL valve slowly until pressure drops below
20 cm H2O, then stop
- Pressure should stabilize and hold
- Sustained pressure alarm stops
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- cannot adjust pressure - valve sticking
- sustained pressure limit is the high pressure
limit or a max of 30 cm H2O
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- Open APL valve fully, flush occluded circuit with
O2
- Circuit pressure stays < 10 cm H2O
- Scavenging reservoir bag fills and then
positive pressure relief valve releases
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- opening pressure of APL too high
- hose from circuit to scavenger blocked
- faulty positive pressure relief valve on
scavenger
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- APL valve fully open, flows set at minimum and
circuit still occluded
- Circuit rebreathing bag does not deflate
- Scavenging reservoir bag does deflate
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- opening pressure of APL too low
- too much vacuum and faulty negative pressure
relief valve
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- no vacuum; needle valve closed
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