Nihon Kohden NKV-330

Asset Type

Ventilator

Manufacturer

Nihon Kohden

Model

NKV-330

What This Guide Helps With

This guide helps troubleshoot the LOW PIP alarm on a Nihon Kohden NKV-330 ventilator. This alarm indicates that peak inspiratory pressure is at or below the lower alarm limit. It may be caused by low airway pressure, a large leak, disconnected tubing, inappropriate settings, sensor line problems, moisture, blockage, or breath delivery failure.

A LOW PIP alarm should be treated as a possible ventilation problem until the patient is confirmed safe and the cause is identified.

Step-by-Step Troubleshooting

Ensure Patient Safety First

• Do not troubleshoot a ventilator alarm while the patient is at risk of inadequate ventilation.
• Confirm the patient’s condition immediately.
• Have clinical staff assess chest rise, breath sounds, oxygen saturation, end-tidal CO₂ if available, airway status, and overall clinical condition.
• If ventilation is questionable, have clinical staff provide manual ventilation or move the patient to another ventilator.
• Do not silence, ignore, or repeatedly reset the alarm without confirming the patient is safe.

A LOW PIP alarm can indicate that delivered pressure is not reaching the patient, often from a leak, disconnected circuit, or delivery problem.

Verify the Reported Alarm and Behavior

• Confirm that the ventilator display shows LOW PIP.
• Observe when the alarm occurs: at startup, after connecting the patient, during inspiration, after circuit movement, or intermittently during use.
• Check whether peak inspiratory pressure is consistently at or below the lower alarm limit.
• Look for related alarms that may point to a leak, circuit problem, or sensing issue.

Verifying the exact alarm and timing helps separate a true pressure problem from a temporary setup or movement issue.

Check the Patient Interface for a Large Leak

• Inspect the mask, endotracheal tube, tracheostomy tube, or other patient interface.
• Check for a loose connection, poor mask seal, disconnected tubing, deflated cuff, leaking cuff, loose adapter, open suction port, or missing cap.
• Correct any obvious leak before suspecting ventilator failure.
• Verify that airway pressure rises appropriately after the leak is corrected.

A large leak can prevent airway pressure from rising and cause peak inspiratory pressure to remain below the lower alarm limit.

Check Control Settings and Alarm Settings

• Review the ventilation mode, pressure settings, volume settings, flow settings, PEEP, and alarm limits.
• Confirm the lower PIP alarm limit is appropriate for the patient and ordered therapy.
• Check whether recent clinical setting changes caused measured PIP to fall below the alarm threshold.
• Only clinical staff should adjust patient therapy settings or alarm limits.

A lower PIP alarm limit set too high can create nuisance alarms even when the ventilator is delivering the selected therapy.

Inspect the Breathing Circuit for Leaks or Disconnections

• Check the full breathing circuit from the ventilator outlet to the patient connection.
• Inspect the inspiratory limb, expiratory limb, humidifier connections, filters, adapters, Y-piece, and exhalation components.
• Look for loose fittings, cracked tubing, disconnected sections, damaged filters, improperly seated water traps, open ports, or leaking humidifier chamber connections.
• Reseat or replace questionable circuit components as appropriate.

Circuit leaks can reduce delivered pressure and trigger a LOW PIP alarm.

Check the Pressure Sensor Line

• Trace the pressure sensor line from the ventilator to the circuit connection.
• Check for loose connections, cracked tubing, water droplets, kinks, clogging, blockage, or incorrect routing.
• Clear, reconnect, or replace the pressure sensor line if needed.
• Confirm the line is clean, dry, open, and securely connected.

If the ventilator cannot accurately sense airway pressure, it may report low peak inspiratory pressure even when the circuit appears connected.

Check the Flow Sensor Line

• Inspect the flow sensor line and associated connections.
• Check for leaks, water accumulation, kinks, clogging, blockage, loose fittings, or incorrect connection.
• Replace or correct the line if there is any doubt about its condition.
• Verify that the flow sensing pathway is connected, unobstructed, and free of moisture.

Flow and pressure sensing problems can affect breath delivery monitoring and cause pressure-related alarms.

Check for Water, Kinks, or Blockage in the Circuit

• Inspect the breathing circuit, pressure sensor line, and flow sensor line for condensation, dependent loops, kinks, or blocked tubing.
• Drain water traps according to facility procedure.
• Replace contaminated, kinked, or obstructed tubing.
• Confirm the circuit and sensing lines are free of water buildup, clogging, and blockage.

Water or obstruction in sensor lines can distort pressure readings and cause incorrect alarm behavior.

Perform Pressure Sensor and Breathing Circuit Calibration

• Remove the ventilator from patient use before calibration.
• Follow the facility-approved procedure for pressure sensor calibration and breathing circuit calibration.
• Use the correct circuit setup during calibration.
• Verify that calibration completes successfully without a recurring LOW PIP alarm.

Calibration helps confirm that the ventilator can correctly measure pressure with the attached circuit configuration.

Isolate Accessory vs Device Failure

• If safe and appropriate, test the ventilator with a known-good breathing circuit, pressure sensor line, and flow sensor line.
• Run the ventilator on a test lung.
• Observe whether peak inspiratory pressure rises appropriately.
• Check whether the LOW PIP alarm returns with known-good accessories.

If the issue clears with replacement accessories, the cause was likely external. If the alarm remains with known-good accessories, the ventilator may require service-level evaluation.

If the Problem Persists

If the LOW PIP alarm continues after checking the patient interface, control settings, alarm limits, breathing circuit, pressure sensor line, flow sensor line, moisture, leaks, blockage, and calibration, external and common causes have been ruled out.

A persistent LOW PIP alarm may indicate an internal breath delivery or sensing failure. The CD-358P breath delivery unit should be suspected if the alarm cannot be corrected through external troubleshooting.

• Remove the ventilator from service.
• Label it Out of Service.
• Do not return it to patient use.
• Send it for repair, bench evaluation, or vendor/service-level support according to facility procedure.

Knowing when to stop is proper troubleshooting. A ventilator with an unresolved pressure delivery alarm should not remain in clinical use.

Clinical Use Tip

Never troubleshoot a LOW PIP alarm on an active patient if ventilation is questionable. Move the patient to a backup ventilator or provide manual ventilation first, then continue equipment checks only after the patient is safe.

Work Order Documentation (CCR Method)

CCR = Complaint, Cause, Resolution

Complaint

What was reported by the clinical staff.

Example:
"Nihon Kohden NKV-330 ventilator alarming LOW PIP. Peak inspiratory pressure reported at or below the lower alarm limit during ventilation."

Cause

What was observed during troubleshooting.

Example:
"Found large leak at patient circuit connection causing low measured airway pressure."

Resolution

What action was taken.

Example:
"Reseated circuit connection, inspected breathing circuit, pressure sensor line, and flow sensor line. Verified no leaks, kinks, water, clogging, or blockage. Alarm cleared during test lung verification. Ventilator returned to service."

Helpful Details to Include (If Known)

• Alarm behavior
• Accessories swapped
• Power behavior
• Environmental factors
• Indicator lights
• Final device status

Final Thought

LOW PIP alarms should be treated as possible ventilation failure until proven otherwise. Start with patient safety, then check leaks, settings, circuit integrity, sensor lines, moisture, blockage, and calibration before suspecting an internal ventilator fault. Good troubleshooting protects the patient, prevents unnecessary parts replacement, and creates clear documentation for the next technician.

That is successful troubleshooting.