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Theory of Operations
though the more advanced control features (active exhalation valve control)
are not functional.

Note:
During Mix and Inspiratory BUV, gas supply to installed options is disabled.
Entry into BUV is logged in the alarm log and system diagnostic log, and the
status display provides an indicator that the ventilator is in BUV and which subsystem is affected.
When in BUV, a high priority alarm is annunciated, and the GUI displays an
alarm banner indicating BUV, blanks patient data, and a displays a pressure
waveform.
If the ventilator cannot provide any degree of reliable ventilatory support and
fault monitoring, then the ventilator alarms and enters the safety valve open
(SVO) emergency state. During SVO, the ventilator de-energizes the safety,
expiratory, and inspiratory valves, annunciates a high-priority alarm, and turns
on the SVO indicator. During SVO, a patient can spontaneously inspire room
air (if able to do so) and exhale. Check valves on the inspiratory and expiratory
sides minimize rebreathing of exhaled gas during SVO. During SVO the ventilator
•
Displays the elapsed time without ventilatory support
•
Does not display patient data (including waveforms)
•
Does not detect patient circuit occlusion or disconnect conditions
Visible indicators on the ventilator's GUI and status display illuminate when the
ventilator is in the SVO state. Other safeguards built into the ventilator include
a one-way valve (check valve) in the inspiratory pneumatic circuit allowing the
patient to inhale through the safety valve with limited resistance. This check
valve also limits exhaled flow from entering the inspiratory limb to reduce the
possibility of re-breathing exhaled CO2 gas.
10.17
Power On Self Test (POST)
Every time the ventilator is powered on or resets and at the beginning of Short
Self Test (SST) and Extended Self Test (EST) it performs Power On Self Test
(POST). POST checks the integrity of the GUI and Breath Delivery subsystems
and communication channels without operator intervention and takes approximately twelve(12) s to complete.
10-76
Operator’s Manual