Puritan Bennett 980

Proximal Flow Sensor Not Detected or Calibration Failure

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Asset Type

Ventilator

Manufacturer

Puritan Bennett

Model

980

What This Guide Helps With

Troubleshooting a missing, inoperative, or failed proximal flow sensor caused by setup, connection, moisture, blockage, sensor damage, or option hardware failure.

Step-by-Step Troubleshooting

1. Ensure Patient Safety First

Do not troubleshoot a proximal flow sensor failure while the Puritan Bennett 980 is actively supporting a patient.

Transfer the patient to another verified ventilator when proximal flow measurements are required for safe clinical management. Confirm ventilation, oxygenation, and alarm operation on the replacement equipment before removing the affected ventilator.

The PB980 may revert to its internal flow sensors when the proximal flow system becomes unavailable, but proximal measurements at the patient wye will no longer be provided. Do not assume that this fallback is clinically acceptable for every neonatal patient.

Expected outcome: The patient is safely supported without relying on unavailable or questionable proximal flow measurements.

Continue Clinical Engineering troubleshooting only after the ventilator has been removed from patient use.

2. Confirm the Exact Failure

Record the displayed alarm, SST result, and reported behavior. Determine whether the ventilator:

The PB980 may disable proximal measurements because the sensor is not detected, readings are outside the expected range, proximal option hardware reports a problem, or communication with the proximal option fails.

Expected outcome: The failure is clearly identified as a connection, measurement, SST, or option-system problem.

3. Verify That Proximal Flow Is Applicable and Enabled

Confirm that:

The proximal flow sensor can operate in the enabled state only when the neonatal circuit type is selected. The option may be enabled or disabled through the Options and Prox configuration screen.

Expected outcome: The correct patient circuit type and proximal flow option are selected.

If enabling the option restores proximal measurements, verify operation and stop.

4. Inspect the Sensor and Pneumatic Lines

Remove the single-use proximal sensor from the test circuit and inspect it under adequate lighting.

Check for:

Excessive moisture or secretion buildup can affect measurement accuracy. The sensor is single-use and should not be cleaned or sterilized. Aerosolized medications may damage it.

Expected outcome: The sensor and both pneumatic lines are clean, dry, intact, and free of obstruction.

Replace any wet, contaminated, damaged, or previously used sensor with a compatible new sensor.

5. Reseat the Ventilator-Side Connector

Open the clear connector-panel door on the front of the breath delivery unit.

Disconnect the proximal sensor connector and inspect:

Firmly reconnect the sensor to the receptacle labeled Prox Flow. The connector must be fully seated in the appropriate front-panel port.

Avoid forcing the connector or applying liquid directly to the port.

Expected outcome: The connector seats securely without looseness or intermittent detection.

If the sensor is detected after reseating, complete functional verification and stop.

6. Verify Sensor Orientation and Circuit Installation

Set up a known-good neonatal patient circuit using the configuration intended for testing.

Confirm that:

When an HME is used, the proximal sensor is positioned between the HME and the breathing-circuit wye.

Expected outcome: The sensor is correctly oriented, securely connected, and not subjected to tubing strain.

If correcting the installation restores the measurement, verify operation and stop.

7. Check for Leaks or Occlusions

Inspect the complete test circuit for:

During proximal SST, the PB980 evaluates circuit leakage, resistance, compliance, autozero operation, purge operation, barometric pressure, and pressure cross-check functions.

Expected outcome: The test circuit and proximal sensor pathway are unobstructed and leak-free.

Correct any external problem before repeating SST.

8. Substitute a Known-Good Proximal Flow Sensor

Install a new, compatible Puritan Bennett proximal flow sensor.

Do not reuse a sensor taken from patient service unless it is unopened and unused. Use only the sensor type approved for the PB980 proximal flow option.

Confirm the new sensor is:

The operator guidance allows the proximal sensor to be exchanged without repeating SST when the circuit and other accessories have not changed. For a reported calibration failure, however, repeating SST is appropriate to verify the entire proximal system before return to service.

Expected outcome: A known-good sensor is recognized and proximal data become available.

If the replacement sensor resolves the issue, discard the defective sensor according to facility policy, complete testing, and stop.

9. Run SST With the Complete Intended Configuration

Remove the ventilator from clinical use and perform the manufacturer-approved Short Self Test.

Install all components that will affect circuit calculations, including:

Follow every SST prompt carefully. When instructed:

The manufacturer states that SST must be completed with the circuit, proximal sensor, and accessories installed in the configuration intended for use.

Expected outcome: All SST tests, including SST Prox, pass without alerts or failures.

If SST passes and proximal values remain stable, proceed with final functional testing.

10. Review the Specific SST Failure

If SST fails, document which test failed rather than recording only “calibration failed.”

Relevant failures may include:

The SST Prox test evaluates the proximal subsystem’s barometric-pressure, autozero, purge, and pressure cross-check functions.

A non-Prox SST failure may indicate a circuit, filter, occlusion, or connection problem rather than a defective proximal option.

Expected outcome: The failed test is isolated sufficiently to determine whether the cause is external or internal.

11. Check Alarm and Diagnostic Logs

Review available alarm, SST diagnostic, system diagnostic, and communication logs.

Record:

The PB980 stores alarm and SST diagnostic information that can assist qualified personnel in identifying recurring failures.

Do not attempt board-level diagnosis unless trained and authorized for PB980 service.

Expected outcome: The failure pattern supports either sensor replacement, external correction, or escalation for internal service.

12. Perform Final Functional Verification

After the corrective action:

The Y displayed with applicable parameters indicates that the values are being measured by the proximal flow sensor rather than the ventilator’s internal flow sensors.

Expected outcome: The ventilator passes SST, recognizes the sensor, displays stable proximal measurements, and operates without recurring alarms.

If successful, return the ventilator to service according to facility policy.

If the Problem Persists

If a known-good sensor, correct neonatal configuration, secure connections, dry and unobstructed tubing, and a verified test circuit do not resolve the issue, common external causes have been ruled out.

A persistent SST Prox failure may involve the proximal option pneumatics, autozero or purge components, option electronics, connector assembly, or internal communication. Manufacturer guidance indicates that continued failure after circuit and sensor checks requires evaluation of the proximal flow option hardware.

The ventilator should be:

Do not return the ventilator to neonatal service solely because it can operate using internal flow sensors. The required clinical configuration and intended use must determine whether operation without proximal measurements is acceptable.

Knowing when to stop external troubleshooting and escalate is proper Clinical Engineering practice.

Clinical Use Tip

Never troubleshoot the proximal flow system on an actively ventilated neonatal patient. Transfer the patient first and verify the replacement ventilator before manipulating the sensor, tubing, circuit, or configuration.

Do not install a proximal sensor in the patient circuit unless its pneumatic connector is also connected to the ventilator.

Work Order Documentation (CCR Method)

CCR = Complaint, Cause, Resolution

Complaint

What was reported by the clinical staff.

Example:
"Respiratory Therapy reported that the Puritan Bennett 980 displayed “Prox Inoperative,” did not detect the neonatal proximal flow sensor, and failed SST Prox."

Cause

What was observed during troubleshooting.

Example:
"Inspection found moisture inside the proximal sensor pneumatic tubing, causing unstable pressure readings and repeated proximal calibration failure."

Resolution

What action was taken.

Example:
"Removed the contaminated single-use sensor, installed a new compatible proximal flow sensor, reseated the Prox Flow connector, completed SST successfully, and verified stable proximal flow and volume measurements with a neonatal test circuit."

Helpful Details to Include (If Known)

Final Thought

Proximal flow failures should be approached by protecting the patient first, then verifying configuration, sensor condition, connections, orientation, circuit integrity, and SST results. Replacing a questionable single-use sensor is appropriate; repeated failure with a known-good setup requires qualified internal evaluation. Clear CCR documentation preserves the troubleshooting logic and supports safe repair decisions.

That is successful troubleshooting.

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