Puritan Bennett GoodKnight 420 Evolution
Puritan Bennett · Model GoodKnight 420 Evolution
CPAP machine This is an auto-adjusting which is set for a range of pressures, then seeks out and delivers the lowest level of pressure needed to keep the airway open. The pressure level will vary as needed, but it will not lower with each exhalation as a bilevel does. The auto-adjusting CPAPs were designed for patients who are unable to participate in a sleep study or whose pressure needs vary during the night according to their stage of sleep or sleep position. However, any patient will receive very comfortable therapy from this type of CPAP.
Key tips
- ·Never disable a low-pressure/circuit-disconnect alarm while troubleshooting - silence it, don't disable it.
- ·Verify the O2 supply source and pressure before assuming an internal fault.
- ·Circuit type must match the patient population (adult/pediatric/neonatal) - a mismatched circuit invalidates delivered volumes.
Typical Failure Modes
Compiled for this model from its own documentation and established engineering knowledge for this equipment class - not from a verified service record. Confirm against the manufacturer's service manual.
Does not reach or hold set pressure
HighSymptoms: Therapy pressure low or unstable, cannot titrate, pressure-error alarm.
Root cause: Worn blower, an internal leak, a pressure-sensor fault, or a large mask / circuit leak.
Blower noisy / failing
MediumSymptoms: Loud or rattling blower, cannot meet flow demand, blower-error code.
Root cause: Worn blower bearings / motor.
Humidifier fault
MediumSymptoms: No or excessive humidity, water in the tubing, humidifier not heating, leak at the chamber.
Root cause: Humidifier heater plate, a chamber-seal fault, or a heated-tube fault.
Flow / pressure sensor drift
MediumSymptoms: Reported pressure or leak / AHI data implausible, fails verification.
Root cause: Sensor drift or a blocked sensing line.
Data / compliance download fault
LowSymptoms: SD card or modem data will not read, therapy data missing.
Root cause: SD card / slot fault or the wireless module.
Serviceable Parts & Consumables
Serviceable items for this model, compiled from its documentation and engineering knowledge for this equipment class. Service class and relative cost are estimates, not manufacturer figures; no part numbers are given. Confirm intervals and pricing against the manufacturer.
Blower / motor assembly
Class Periodic replacementRel. cost $$$R&R Difficult
Pressure / flow sensor
Class Major service partRel. cost $$R&R Moderate
Humidifier heater plate / chamber seal
Class Periodic replacementRel. cost $$R&R Fairly easy
Inlet air filter
Class ConsumableRel. cost $R&R Easy
SD card / wireless module
Class Periodic replacementRel. cost $R&R Fairly easy
| Part | Service class | Relative cost | R&R difficulty |
|---|---|---|---|
| Blower / motor assembly | Periodic replacement | $$$ | Difficult |
| Pressure / flow sensor | Major service part | $$ | Moderate |
| Humidifier heater plate / chamber seal | Periodic replacement | $$ | Fairly easy |
| Inlet air filter | Consumable | $ | Easy |
| SD card / wireless module | Periodic replacement | $ | Fairly easy |
Relative cost: $ lowest · $$$$ highest service-part cost for this equipment class. Not a price.
PM Checklist
Preventive-maintenance tasks typical of this equipment class. Perform to the manufacturer's procedure and your facility's policy - this is general reference, not a schedule for this specific unit.
- ·Daily pre-use check: self-test, circuit integrity, alarm function
- ·Scheduled circuit and inspiratory filter replacement per manufacturer interval
- ·Flow and pressure sensor calibration verification
- ·Battery load test and runtime check
- ·Annual full PM and electrical safety test
Troubleshooting Approach
A starting sequence for this model, compiled from its documentation and engineering knowledge for this equipment class. Follow the manufacturer's service documentation for the actual procedure.
Symptom: Does not reach or hold the set pressure
- Run the device's pressure-verification against a calibrated manometer with a test lung / cap.
- Check for internal leaks and a blocked pressure-sensing line.
- Confirm the mask / circuit is not the leak source.
- Replace the pressure sensor if it fails verification.
- Replace the blower if it cannot meet flow demand.
Symptom: Blower noisy / failing / cannot meet flow
- Listen for bearing rumble or rattle from the blower.
- Check the inlet air filter is clean.
- Confirm no internal air leak.
- Replace the blower / motor assembly.
- Re-verify pressure and flow after replacement.
Symptom: Humidifier fault (no / excessive humidity, water in the tubing)
- Confirm the heater plate warms and the chamber seats fully.
- Inspect the chamber seal and the heated-tube connector.
- Check the humidity setting against ambient conditions.
- Replace the chamber seal or the heated tube.
- Replace the humidifier heater assembly if it will not heat.
Symptom: Therapy / compliance data will not download
- Try a known-good SD card in the correct slot.
- Check the card is not write-protected or corrupt.
- Confirm the wireless module / modem where fitted.
- Read the card on a PC to confirm data is being written.
- Replace the SD card / slot or the wireless module as isolated.
Typical Location
Where this class of equipment is typically deployed - general reference, not this unit's own placement record.
- ICU / CCU
- Emergency Department
- Operating Room (anesthesia-adjacent)
- NICU
- Respiratory Therapy department
- Patient transport
Documents & Manuals
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