Grading a Spirometry Session with an Unacceptable First Effort and Non-Reproducible FEV1
A 34-year-old woman referred for spirometry has performed three forced expiratory maneuvers. The technologist's notes read: Effort 1 - back-extrapolated volume (BEV) 0.24 L, FEV1 2.20 L, FVC 3.05 L, expiratory flow still 0.06 L/s when the technologist stopped the maneuver at 6 seconds. Effort 2 - BEV 0.09 L, FEV1 2.34 L, FVC 3.30 L, clear plateau (flow <0.025 L/s for >1 second) at 7 seconds, good effort throughout. Effort 3 - BEV 0.12 L, FEV1 2.63 L, FVC 3.33 L, plateau at 8 seconds, but the patient leaned forward and produced a fast, snatchy start. Reference values: FEV1 3.10 L, FVC 3.80 L, LLN for FEV1/FVC 0.70. The patient is now coughing and says she is tired; laboratory policy permits up to eight maneuvers.
1. Grade the session using the acceptability and repeatability criteria, showing the arithmetic for each judgment.
Read the worked answer
Acceptability, effort by effort
| Effort | BEV | BEV limit (0.15 L or 5% of FVC, whichever is greater) | Verdict |
|---|---|---|---|
| 1 | 0.24 L | 5% of 3.05 = 0.153 L → limit 0.153 L | Unacceptable (BEV exceeds limit; also no end-of-test plateau - stopped at 6 s with flow still 0.06 L/s) |
| 2 | 0.09 L | 5% of 3.30 = 0.165 L → limit 0.165 L | Acceptable (BEV well under, plateau met, no cough in first second, no leak) |
| 3 | 0.12 L | 5% of 3.33 = 0.167 L → limit 0.167 L | Acceptable (BEV under limit, plateau met) |
A snatchy, fast start is not disqualifying by itself - what matters is the back-extrapolated volume, and 0.12 L is within the limit.
Repeatability
- FEV1: 2.63 − 2.34 = 0.29 L, which exceeds the 0.150 L repeatability criterion → not repeatable.
- FVC: 3.33 − 3.30 = 0.03 L → repeatable.
Grade
- Two acceptable efforts, but FEV1 fails repeatability → Grade C if the session ended here. Effort 1 contributes nothing and should be discarded from the calculation (it is retained only in the raw record).
The error to avoid is either (a) accepting effort 1 because the FEV1 "looks reasonable," or (b) averaging the three FEV1 values. Spirometry is never averaged.
2. What do you do next - how many more efforts, what specific coaching, and what does the pattern of the three efforts tell you?
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Number of efforts: two acceptable efforts are on the record and policy allows up to eight. The goal now is not "more blows" but at least one more acceptable maneuver that is reproducible with effort 3 (or a second effort reproducible with effort 2, which would force a re-examination of effort 3). Three acceptable efforts is the usual target; stop at eight or earlier if the patient is symptomatic.
The pattern is diagnostic of the coaching problem. Effort 2 gave FEV1 2.34 L with the same FVC as effort 3 (3.30 vs 3.33 L). Identical FVC with a 0.29 L FEV1 difference almost always means effort 2 was submaximal in the first second - a slow, hesitant start, or a patient who "paced herself" against the cough - not that effort 3 captured a different lung. If effort 3 were the outlier (e.g., an artifactually fast start inflating the FEV1), you would expect its FVC to be different too.
Specific coaching before the next effort
- Let her rest until the cough settles; a coughing patient cannot give a reproducible forced expiratory maneuver and coughing during the first second invalidates the effort anyway.
- Re-demonstrate the start as a single explosive movement: "seal your lips, take the biggest breath, then blast it out - think of blowing out candles across the room."
- Fix the posture issue from effort 3: feet flat, sitting upright, chin slightly up, no leaning forward, and hold the mouthpiece with both hands so the trunk stays still.
- Coach the end separately: keep blowing for a full 6 seconds or until the technologist says stop, so she is not guarding against the cough.
- Give feedback after each effort using her own numbers ("that one was 0.2 L bigger in the first second - do the same start again").
If variance persists despite good coaching, document it and accept grade C. In a symptomatic, coughing patient, a reported comment explaining the variation is far more honest than quietly dropping the inconvenient curve.
3. If this really is the final data set, what values go on the report, what does the ratio become, and what comment accompanies it?
Read the worked answer
Values reported (largest acceptable value for each parameter, even if from different curves)
- FEV1 = 2.63 L (from effort 3, the largest acceptable FEV1)
- FVC = 3.33 L (from effort 3)
- FEV1/FVC = 2.63 / 3.33 = 0.79
Using the largest FEV1 and largest FVC regardless of which maneuver produced them is the standard convention and is exactly why both must come from acceptable curves. Here both happen to come from the same maneuver, which is the easy case.
Interpretation inputs
- FEV1 2.63/3.10 = 85% predicted; FVC 3.33/3.80 = 88% predicted; ratio 0.79 is above the LLN of 0.70 → no obstructive or restrictive pattern is evident on these numbers.
Required comment / quality statement
- Session grade C, with the reason spelled out: effort 1 rejected for back-extrapolated volume of 0.24 L (limit 0.153 L) and absence of an end-of-test plateau; efforts 2 and 3 acceptable but FEV1 differing by 0.29 L, exceeding the 0.150 L criterion.
- Note the cough and the resulting coaching limitation.
- Do not report FEV1 from effort 1's 2.20 L, and do not report a mean or "best of three average."
- A quality note of this kind tells the interpreter that the FEV1 could reasonably lie anywhere between roughly 2.34 and 2.63 L, which matters if this patient will be followed serially for a condition in which a 0.2 L change is the difference between stable and progressing. A borderline ratio (0.79 here is comfortable) in a patient with a grade C session would justify repeating the study rather than interpreting it.