4. Breathing System (cont'd)

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

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
  • faulty selector switch - allows cross-over of gas into ventilator circuit

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

 

 

  • improperly adjusted APL valve - set to release either too high or too low
  • no alarm - upper limit set too high
  • Open APL valve slowly until pressure drops below 20 cm H2O, then stop
    • Pressure should stabilize and hold
    • Sustained pressure alarm stops
  • cannot adjust pressure - valve sticking
  • sustained pressure limit is the high pressure limit or a max of 30 cm H2O
  • 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
  • opening pressure of APL too high
  • hose from circuit to scavenger blocked
  • faulty positive pressure relief valve on scavenger
  • APL valve fully open, flows set at minimum and circuit still occluded
    • Circuit rebreathing bag does not deflate
    • Scavenging reservoir bag does deflate
  • opening pressure of APL too low
  • too much vacuum and faulty negative pressure relief valve
  • no vacuum; needle valve closed

Previous Page

Next Page

Close Window to return to Article