GE Aisys CS2: high PEEP in the breathing circuit
What happened
A GE Aisys CS2 anesthesia machine was showing high PEEP; the engineers suspected moisture carry-over from the compressor into the breathing system, and the expiratory side had already been checked.
What was checked
- Inspected all valves, seals and rings under the bellows module, since the expiratory path had already been cleared.
- Assessed whether valve calibration could restore proper seating before going further.
- Stripped the inspiration flow valve to examine the disc and its seat for traces of moisture.
Cause
The engineers found that the inspiration flow valve was not seating fully during exhalation and was holding pressure in the circuit — a picture consistent with moisture contamination from the compressor. The link was judged probable in this case, not proven.
The cause is probable and was not fully confirmed.
What was done
The first step was valve calibration — a procedure from the manufacturer's service documentation, done by authorised personnel. If calibration does not restore tight closure, the inspiration flow valve assembly is replaced (the part cited in the case is 1505-3209-000). The case also describes a workshop-type alternative: hot disassembly, removal of the inner mushroom-shaped washer, regrinding its sealing surface and recalibration; the outcome was reported as probable.
Safety
Depressurise and disconnect the breathing circuit before opening the valve module, and before the machine returns to clinical use run the manufacturer's leak and ventilation performance checks with a test lung.
Lesson: After moisture ingress, a poorly seating inspiratory valve can raise PEEP just like the expiratory side, so check the seating of both valves instead of only the obvious one.
Covered in the course: Anaesthesia Machine Service — Level 2: Fault-Finding →
Written from an anonymised case shared by service engineers. It is not a manufacturer instruction and grants no authorisation. Independent note; names are trademarks of their owners.