Acceptability and Reproducibility Criteria for Spirometry Curves
Acceptability and Reproducibility Criteria for Spirometry Curves
This domain tests the rules for judging whether a spirometry session is usable and how to grade it.
Core rules
- An acceptable maneuver is free of artifacts: no cough in the first second, no glottic closure, no leak, no obstructed mouthpiece, good start (back-extrapolated volume under 5% FVC or 0.150 L), and satisfactory duration.
- Reproducibility: the two largest FVC values must agree within 0.150 L, and the two largest FEV1 values within 0.150 L.
- Perform at least 3 acceptable maneuvers; stop when 3 acceptable and 2 reproducible are obtained, or after 8 maneuvers.
- Grade the session: A = at least 3 acceptable and reproducible; B = 2 acceptable and reproducible; C = 2 acceptable but not reproducible; D = only 1 acceptable; F = none acceptable.
- Report the largest FVC and FEV1 from acceptable curves, not necessarily from the same maneuver.
Worked example
Three maneuvers give FVC 3.80, 3.90, and 4.10 L; FEV1 2.90, 2.95, and 3.00 L. Reasoning: FVC spread is 0.30 L (over 0.150 L), so the session is not reproducible; FEV1 spread is 0.10 L. The session is grade C if only two are acceptable, or continue to a fourth maneuver to try to meet reproducibility.
Traps
- Averaging results instead of reporting the largest values.
- Calling a session reproducible when only FEV1, not FVC, meets the 150-mL rule.
- Forgetting that a cough after 1 second may still affect FVC.