(e) If necessary, troubleshoot the outflow valve using the procedures
outlined in Table 2-7 below.
Leak in the
1. Check and secure all
connections and ensure
CPAP at a flow
the patient connector is
rate of 15
attached to the
mechanical test lung for
a closed system.
2. Replace the diaphragm
with a new diaphragm
Table 2-7. Outflow valve troubleshooting.
Pressure relief valve.
(a) Ensure the flow is adjusted to 10 lpm.
(b) Remove the red patient-exhalation tubing attached to the bottom of
the shuttle-valve assembly.
(c) Seal or otherwise block the end of the disconnected tubing and
observe the manometer for a pressure rise and plateau of 30cmH2O. An audible alarm
should be heard at this pressure.
(d) If a distinct audible alarm is not heard (at 30cmH2O), remove the
reed alarm from the back of the relief valve (to get at the adjusting nut) and use a 1/4-
inch nut driver to adjust the device to the correct relief pressure. A clockwise rotation of
the adjusting nut increases the relief pressure.
(e) Replace the reed alarm and recheck the pressure. Back pressure
of the reed alarm may increase pop-off pressure; adjust accordingly. Ensure the audible
alarm is heard during a 30cmH2O pressure plateau.
Reconnect the exhalation tube to the shuttle valve.
(g) Use the procedures outlined in Table 2-8 to troubleshoot the
pressure relief valve.