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Pulmonary Function Test • Publication 014181-001 Rev 02 • www.datasci.com ©2023 Data Sciences International
without any air leaking through. This is a very likely place to find a leak.
• To improve the quality of your seal, try using a greasy substance (like vacuum grease or silicone
grease) around the outside of the air tube. Make sure that no grease gets inside the air tube.
• Thin Teflon tape may be applied or wrapped around the area in suspicion, providing a semi-
malleable and snug connection. Be careful not to add too much Teflon tape, however, because too
much will only prevent you from making the connection completely.
Never glue air tubes, valves, or any other connections together. This may interfere with the air
flow. It will also prevent you from ever moving or adjusting previously detachable parts.
Test for Leaks in the Main Chamber
If you suspect a leak in the PFT chamber, then you can repeat the FRC flow calibration.
If the calibration is successful, then the chamber is likely not leaking.
If you want to verify more thoroughly that the chamber does not leak:
• Plug the tracheal tube port and close the chamber,
• Seal the pneumotach opening with painter’s tape or electrical tape,
• Pull the plunger of a 10 cc syringe back 5 mL,
• Connect the syringe to the syringe port of the chamber and to the calibrator at the same time using a Luer “T”
fitting,
• Inject the air, keeping pressure on the plunger to make sure it does not get pushed back,
• Make sure that the water level in the calibrator does not rise and stays steady.
Test for Leaks in the Valve Assembly
If you suspect a leak in the valve assembly (the Lucite manifold that houses all the valve connections, at the end of
the chamber). Simply follow the instructions listed in the Pressure Calibration chapter. After pushing the syringe
plunger until the calibrator is at 20 cm H
2
O, the water level in the manifold should not raise, and the voltage
should not drift down. If the voltage drifts down, then you have a leak, and you should identify and fix the leak in
the manifold.
Common places to look for a leak in the Valve Assembly:
• N
2
Sample port. Make sure it is plugged.
• Mouth Pressure Transducer.
If the leak is not in either of these places, you will need to narrow it down by removing one valve at a time and
plugging the hold with tape or a bung. Start with the Slow Expiration, then Inflation, etc.
If you cannot solve your leak problem, then you may have a faulty valve or transducer. Please call your DSI
representative in that situation.
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