Spirometer Performance, Calibration Verification, and Quality Control
Spirometer Performance, Calibration Verification, and Quality Control
This domain tests the daily and periodic checks that keep volume and flow measurements trustworthy. A spirometer that is not verified can produce precise-looking but invalid numbers.
Core rules
- Perform a calibration verification at the start of each testing day, after movement, after sensor cleaning, and whenever results look implausible.
- Use a 3.00-L calibration syringe; inject slowly, at medium flow, and rapidly. Measured volume should be within ±3.5% (about 2.895–3.105 L).
- Check flow linearity across the range used in testing; a single slow injection does not prove accuracy at high flow.
- Record results in a log: date, time, syringe volume, measured volume, percent error, technician, and corrective action.
- Follow manufacturer limits for temperature, humidity, and warm-up; apply BTPS correction.
- Run periodic biologic control with a healthy nonsmoker to detect drift; document the values.
Worked example
A daily check with a 3-L syringe yields 2.80 L. Error = (2.80 − 3.00)/3.00 × 100 = −6.7%, outside ±3.5%. Reasoning: do not test participants. Check for leaks at the syringe and mouthpiece, clean or replace the sensor, repeat the check, and if still out of range remove the device from service.
Traps
- Calibrating only when a result looks abnormal.
- Confusing calibration (adjusting) with verification (checking).
- Ignoring a passing slow injection when high flows are inaccurate.