Avance family (Datex-Ohmeda S/5 Avance, Avance CS2)
Datex-Ohmeda / GE anaesthesia workstations with an electronic gas mixer, an integrated bellows ventilator and a compact breathing system, used in operating theatres for general anaesthesia from adults to children.
2,284 manual-derived records across S/5 Avance, S5 Avance and Avance CS2 (221 alarm/troubleshooting rows, 81 maintenance lines, about 2,000 parts entries), 2 Avance field cases and 1 field case from the sister Aisys CS2; all field outcomes are 'suggested' or single-source.under engineering review
Architecture
Display unit and Anesthesia Control Board (ACB)
The display unit (on the CS2: carrier board, COM Express CPU, internal Compact Flash card with the software, and a coin cell) runs the user interface. The Anesthesia Control Board supervises gas delivery and talks to the mixer, the ventilator and the power controller. ACB faults appear as 'System Malfunction' messages (EEPROM, RAM, watchdog, communication). Display faults are boot failures, 'App Not Loaded', a dead encoder or touch, and lost setups.
Gas supplies and electronic mixer
O2, air and N2O come from pipeline or cylinders through supply pressure transducers to an electronic mixer. The mixer has an O2 channel and a balance-gas channel (air or N2O, chosen by a selector valve), each with a proportional valve and flow, pressure and temperature sensors. Mixer errors drop the machine to the Alternate O2 screen, so the clinician can still give oxygen. Know the Alternate O2 path and test it.
Ventilator and drive gas
The bellows ventilator is driven by gas through a ventilator flow valve controlled by the vent interface board (Vent SIB). Manifold and airway pressure transducers watch the drive and patient sides. Failures here usually show as 'Vent Fail. Monitoring Only' (supply voltages, valve current, pressure sensor), 'Bellows Collapsed' or 'Drive Gas Lost', or loss of PEEP and pressure modes.
Breathing system (ABS)
The compact breathing system carries the absorber, the bellows, the APL valve, the inspiratory and expiratory flow sensors and the galvanic O2 cell. A latch switch confirms it is seated. Most day-to-day complaints start here: wet or damaged flow sensors, a worn free-breathing (flapper) valve and its o-ring, a breathing system that is not latched, and leaks at the seals.
Vaporizer manifold, fresh gas outlet and scavenging
Vaporizers sit on a manifold with port o-rings that wear and are replaced every year. The auxiliary / common gas outlet (ACGO / SCGO) switches fresh gas to an external circuit, and volume and apnea monitoring are off in that mode. The AGSS scavenging receiver has a reservoir, air brake, filter and relief valves that need inspection, and condensate collects in the reservoir.
Airway gas module
An optional plug-in module (for example CAiO types) measures CO2, O2 and anaesthetic agents through a sample line and a D-fend water trap. Blocked lines, residue on the D-fend membrane and module hardware faults produce MGAS alarms. The module needs periodic calibration with certified calibration gas.
Power controller and batteries
The power controller manages mains, the backup batteries and the DC-DC supplies to each subsystem. Its service menu shows the voltages for every board, so start power troubleshooting at the power controller and work forward. Battery alarms usually mean aged batteries. A daily reminder that the system has run more than 12 hours without a power-up self-test is normal behaviour, not a fault.
Faults and how to find them
O2 cell in the breathing system was replaced and calibrated fine, but a couple of weeks later the O2 reading fails again and the cell seems to need replacing again.field case
- Damaged coiled cable or connector between the O2 cell and the machine
- Moisture at the cell connector
- Genuinely defective cell (less likely if it is in date and calibrated well at first)
- Inspect the coiled cable along its full length and flex it while watching the O2 reading
- Check the connector pins for corrosion or moisture
- Fit a known-good cable before fitting another cell
Replace the O2 cell cable if flexing changes the reading, then do the 21% / 100% O2 calibration and check the reading against a reference analyser.
Airway gas module (S/5 Avance with CAiO-type module) shows no more than about 60% O2 while the fresh gas is set to 100% O2.field case
- Delivered concentration really is lower than set (mixer, supply or circuit issue)
- Room air entering through a leaking sample line, D-fend or connector
- Gas module O2 measurement out of calibration
- Measure the delivered O2 physically with an independent, calibrated analyser at the patient connection
- Compare with the breathing-system O2 cell reading
- Replace the sample line and D-fend and check all connections for leaks
- Run a module calibration check with certified calibration gas
If delivery is correct and the module still reads low, calibrate the module with certified calibration gas or send it to an authorised service centre. Do not adjust it without calibration gas.
High, unstable PEEP during mechanical ventilation after moisture got into the drive gas (reported on the sister Aisys CS2 platform).field case
- Inspiratory flow valve under the bellows not sealing fully during expiration
- Water in the ventilator gas path from a wet compressed air supply
- Flow valve calibration drifted
- Inspect the whole expiratory side (exhalation valve, sensors, tubing) for water
- Check the drive gas supply for water
- Run the ventilator flow valve calibration (it needs the calibration orifice tool)
Calibrate the inspiratory flow valve with the proper orifice tool. If the calibration will not pass, replace the valve, then calibrate and run the full checkout.
'CHECK FLOW SENSOR' or 'PATIENT VOLUME MISMATCH' alarm; volumes look wrong or the checkout fails the flow sensor step.reference
- Water in the inspiratory or expiratory flow sensor
- Damaged sensor membrane or sensor fitted in the wrong port
- Leak in the breathing system
- Flow sensors out of calibration
- Remove and dry both flow sensors; inspect the membranes
- Check that each sensor is in its correct port and fully seated
- Run the breathing system leak test
- Run the flow sensor calibration
Dry, recalibrate or replace the flow sensors, as the system message suggests. Replace the inspiratory flow sensor if the machine reports an EEPROM failure on it.
'O2 SENSOR FAILURE' or 'O2CAL ERROR' (breathing-system O2 cell).reference
- Galvanic O2 cell at end of life
- Cable or connector fault
- Calibration done in the wrong gas
- Check the cell date
- Check the cable and connector as in the field case above
- Repeat the calibration in room air and in 100% O2
Replace the cell or cable and recalibrate.
'BELLOWS COLLAPSED' or 'DRIVE GAS LOST'; the ventilator cannot drive the bellows.reference
- Drive gas supply lost or too low
- Leak in the bellows housing or a bellows not seated
- Breathing system not latched or a leaking circuit, so the bellows empties
- Ventilator flow valve or manifold pressure sensor fault
- Confirm the drive gas supply pressure
- Reseat the bellows and its housing; inspect the seals
- Run the breathing system leak test
- Read the manifold and airway pressures in service mode during ventilation
Restore the drive gas supply, or replace the bellows, seals or ventilator valve, as indicated. Run the full checkout.
'O2 PRESS LOW', 'AIR PRESS LOW' or 'N2O PRESS LOW', or 'O2 / AIR PIPE INVALID'.reference
- Pipeline pressure low and no backup cylinder (or cylinder nearly empty)
- Pipeline hose or inlet problem
- Supply pressure transducer fault (the 'invalid' message points here)
- Compare the displayed pressures with an external gauge on the pipeline and the cylinder
- Check the hoses and inlets
- Check the supply transducer readings in the service Gas Supplies menu
Restore the supply, or replace the faulty transducer.
Mixer errors ('MIXER O2 FLOW FAIL', 'O2 / BAL FLOW CTRL FAIL', 'PROP VALVE FAIL', 'BAL GAS CHANGE FAIL', mixer communication failure); the machine switches to the Alternate O2 screen.reference
- Supply pressure problem on the affected gas
- Failed proportional valve, flow sensor, temperature sensor or selector valve inside the mixer
- Communication or power fault between the mixer and the ACB
- Confirm all supply pressures first
- In service mode, go through the Gas Supplies, Mixer Output, Mixer Tests and Mixer Temperatures menus in that order
- Check the mixer supply voltage in Power Diagnostics
Usually the mixer assembly is replaced as a unit. Afterwards, do all calibrations and the full checkout, and verify delivered O2 with an independent analyser.
'Vent Fail. Monitoring Only' with ventilator messages (VENT +6V / -6V / ADC VREF FAIL, VENT VALVE POWER FAIL, VENT FLOW VALVE FAIL CURRENT, MANIFOLD PAW SENSOR FAIL).reference
- Supply voltage problem to the ventilator interface board
- Failed ventilator interface board (Vent SIB)
- Failed ventilator flow valve or manifold pressure transducer
- Open Power Diagnostics and follow the voltages from the power controller forward; problem values are shown in red
- Check the cabling between the power controller, the ACB and the vent board
- Check the flow valve coil and connector
Replace the failed board, valve or transducer, then calibrate and run the full checkout.
'PEEP PCV NOT AVAILABLE' (only volume ventilation without PEEP is offered).reference
- Manifold pressure transducer reading abnormally negative
- Sensing line disconnected or blocked
- Transducer out of calibration
- Read the manifold pressure in service mode at rest
- Inspect the sensing line
- Run the pressure transducer calibration
Reconnect or replace the sensing line, or replace the transducer, then calibrate and run the full checkout.
'BREATHING SYSTEM NOT LATCHED' although the breathing system looks mounted.reference
- Breathing system not fully pushed home or latched
- Latch or detection switch worn or misaligned
- Remove and refit the breathing system
- Inspect the latch and the switch actuator
Repair or replace the latch or switch, then run the leak test and the full checkout.
Checkout leak test fails, or fails only when a particular vaporizer is mounted.reference
- Worn or missing vaporizer port o-rings
- Vaporizer not seated or locked
- Leaking breathing system seals or absorber canister
- Run the low-pressure leak test with each vaporizer mounted and turned on, one at a time
- Inspect the port o-rings
- Check the absorber and breathing system seals
Replace the port o-rings or the leaking seal. Send a leaking vaporizer for vaporizer service.
Battery alarms ('BATTERY FAIL', 'BATTERY CHARGE FAIL', 'BATTERY MISSING', short run time) or 'PWR CNTRL DC-DC FAIL'.reference
- Aged backup batteries
- Battery connection fault
- Power controller or DC-DC failure
- Check the battery age and connections
- Read the power controller values in Power Diagnostics
- Run on battery and confirm the expected run time
Replace the batteries as a set, or replace the power controller if it reports a DC-DC failure while mains is good.
Display will not boot, shows 'App Not Loaded', touch is misaligned or not working, or the rotary encoder is dead (mainly Avance CS2 display).reference
- Corrupt software or failed Compact Flash card
- Flat display coin cell
- Loose internal cable, failed touch controller or encoder
- Reload the software from the original USB media
- Check the coin cell
- Calibrate the touch from the display diagnostics in service mode
- Reseat the encoder and touch cables
Replace the CF card, then the touch controller or encoder, and finally the carrier / COM Express board if needed.
MGAS alarms: 'LINE BLOCKED', 'INLET FILTER RESIDUE' (replace D-fend), 'SAMPLE LINE NOT CONNECTED', 'SAMPLE FLOW DEVIATION' or 'SENSOR INOP'.reference
- Blocked or kinked sample line
- Saturated D-fend water trap
- Blocked sample gas outlet (exhaust)
- Module hardware fault (SENSOR INOP)
- Replace the sample line and D-fend
- Check the sample gas outlet
- Swap in a known-good module if available
Replace consumables. A module with a SENSOR INOP fault goes for module repair.
Preventive maintenance
| General inspection: frame, display, arms, drawers and fittings; casters (do not lubricate); labels; external hoses and pipeline hoses; electrical cables | Every 12 months |
| Check that the start-up audio and visual annunciators work (the start-up beeps and the alarm LEDs) | Every 12 months |
| Replace the vaporizer port o-rings and the free-breathing (flapper) valve with its o-ring | Every 12 months |
| AGSS: empty condensate from the reservoir, inspect the air brake for occlusion, and clean or replace the filter on active systems; check the scavenger relief valves | Every 12 months |
| Check and clean or replace the display fan filter and the filter above the AC power inlet | Every 12 months |
| Functional tests: breathing system, pressure relief and negative pressure relief, O2 flush, alternate O2, vaporizer leak test, mixer flow sensors, alarms, service calibrations, then the complete checkout and an electrical safety test | Every 12 months |
| Calibrate the airway gas module with certified calibration gas | Every 6 months, or when readings are in doubt |
| Free-breathing valve maintenance, user calibrations and hard-key test (Avance CS2 schedule) | Every 24 months |
| Replace the system backup batteries and the display coin cell | Per the manufacturer's schedule (the source data lists them in the annual kit; confirm the interval for your model) |
Parts worth keeping on the shelf
| Breathing-system flow sensors (inspiratory and expiratory) | The most common cause of volume and 'check flow sensor' alarms; the annual kit includes two. |
| Galvanic O2 cell, plus a spare O2 cell cable | A consumable cell, and a damaged cable is easily mistaken for a bad cell. |
| Vaporizer port o-rings | Replaced every year, and the usual source of vaporizer-related leaks. |
| Free-breathing (flapper) valve and o-ring | Annual replacement item in the breathing system. |
| System backup batteries and display coin cell | Aged batteries cause battery alarms and short run time; a flat coin cell causes lost setups. |
| D-fend water traps and sample lines; certified calibration gas for the gas module | Most MGAS alarms are consumables, and the module cannot be calibrated without gas. |
| Display fan filter | Cheap and part of the annual service. |
Field notes
An O2 cell that 'fails again' two weeks after replacement is often not the cell. Check the coiled cable and the connector first.
When the gas module shows low O2 at 100% fresh gas, first measure what the patient actually gets with an independent analyser. Calibrating a monitor to match an unverified delivery is dangerous.
Gas module O2 and agent calibration needs certified calibration gas. If you do not have it, do not improvise; send the module to a centre that does.
On the sister Aisys CS2 platform, water from a wet compressed-air drive supply caused high PEEP. The inspiratory flow valve under the bellows was no longer sealing in expiration. Recalibration with the correct orifice tool sometimes recovers it; otherwise replace the valve. Fix the air quality too, or it will come back.
Service menu access, calibration orifices and calibration gas belong in the toolkit before you go to site. Many Avance repairs end in a calibration you cannot do without them.
After any repair, run the manufacturer's full checkout and performance verification before the device goes back to patients.