Treat the ARTP Full Certificate in Spirometry as one decision chain rather than six separate topics: verify the device, judge each blow's acceptability, check repeatability across acceptable blows, report the best values, interpret the pattern from ratio plus FVC, then test and calculate reversibility in the correct way. The actionable advice: build a one-page rubric that walks this chain in order, and mark every practice session against it until the sequence is automatic. The two worked scenarios below show how a single broken link - an unexamined cough, a percentage taken against the wrong reference - flips the clinical answer.
Obstruction, restriction or mixed: why the ratio alone cannot finish the job
A reduced FEV1/FVC ratio flags obstruction, but classifying a full pattern requires the ratio and FVC judged against appropriate reference values together, plus restraint about what spirometry can and cannot confirm.
Work through the pattern decision systematically. A ratio below the lower limit of normal indicates obstructive physiology, and severity is graded using the FEV1 expressed as a percentage of predicted. A reduced FVC with a normal or high ratio raises possible restriction, but spirometry alone cannot confirm restriction - reduced lung volumes need static lung volume measurement. Learn the current UK guidance on reference values rather than relying on the fixed 0.70 ratio, which overestimates obstruction in older adults and can miss it in younger ones.
The mixed pattern is where restraint matters most. A low ratio combined with a low FVC looks like obstruction plus restriction, but air trapping in obstructive disease can itself depress FVC, so the apparent restriction may be artefactual. A defensible report describes the obstructive finding, notes the reduced FVC, and recommends further testing rather than declaring restriction outright. Practise writing that cautious phrasing, because it demonstrates you understand the measurement rather than just the arithmetic.
| Pattern | FEV1/FVC ratio | FVC | What spirometry supports |
|---|---|---|---|
| Obstructive | Below lower limit of normal | Normal or reduced | Obstruction confirmed; grade severity by FEV1 % predicted |
| Possible restriction | Normal or high | Reduced | Report as possible restriction; needs lung volumes to confirm |
| Mixed | Below lower limit of normal | Reduced | Report obstruction; reduced FVC may reflect air trapping, interpret with caution |
| Normal | Within reference range | Within reference range | Normal study if blows are acceptable and repeatable |
Grading quality: acceptability and repeatability are two separate gates
Each blow must first pass acceptability checks - clean start, no cough in the first second, no early termination, adequate duration. Repeatability is then judged only across blows that passed. Grade each blow before judging the session.
Keep the two gates in order. Acceptability is judged per blow: an explosive, well-braced start without hesitation or back-extrapolation, no cough within the first second, no glottic closure or early cut-off, a smooth continuous effort lasting long enough or reaching a plateau, and no leak. Repeatability is a session-level property: the spread between the best acceptable values. A session with two superb blows and one poor one can still be repeatable; a session with three smoothly sloppy blows cannot pass the first gate at all.
Worked scenario one: three FEV1 readings of 2.45 L, 2.31 L and 2.44 L. The tempting mistake is to see the best two within repeatability tolerance and report 2.45 L. But trace each blow: the 2.45 L trace shows a cough spike in the first second, so it fails acceptability and never enters the repeatability calculation. The remaining acceptable pair, 2.31 L and 2.44 L, differs by 130 mL, which passes a 150 mL tolerance. The better decision is to report 2.44 L as the best acceptable FEV1. Why it matters: the cough-contaminated value overstates lung function, and every downstream interpretation inherits that error.
Reading artefacts on the flow-volume curve before the numbers mislead you
Cough, glottic closure, hesitant start, early cut-off and leaks each leave recognisable signatures on the flow-volume curve. Practise matching shapes to faults so you can explain why a blow failed, not merely that the numbers disagree.
Learn the shape vocabulary. A sharp spike followed by an abrupt vertical drop near the start suggests a cough or glottic closure. A slow ramp up to peak flow suggests a hesitant, poorly braced start. An expiratory curve that terminates prematurely without approaching baseline indicates early cut-off or the patient stopping early. A curve that ends well above the volume axis can indicate a leak. Volume-time curves tell the complementary story: the classic smooth rise to a plateau, or its absence when effort is cut short.
Build the skill with paper drill: print six anonymised curves from your service, two clean and four with different faults, and annotate each with the suspected artefact and the acceptability criterion it breaches. A useful self-check when you review your annotations: clean curves show a single rapid peak and a smooth decay toward the axis, while faulty ones become obvious once named - the exercise trains recognition, which is faster in an exam setting than trying to re-derive the fault from the raw numbers.
Bronchodilator reversibility: which two numbers you compare decides the answer
Reversibility compares the best acceptable pre-bronchodilator value with the best acceptable post-bronchodilator value, expressed as both absolute change and percentage of the baseline. Comparing against means or predicted values changes the classification.
Fix the method first. Record the best acceptable FEV1 and FVC before bronchodilator, administer the drug according to your protocol and wait the interval the guideline specifies, then record the best acceptable values afterwards. Calculate the absolute difference and the percentage change relative to the baseline value. Widely used UK practice quotes a benchmark of at least 12 percent and 200 mL for a significant bronchodilator response, but confirm the exact criteria in the guideline version your training and service follow rather than assuming one universal threshold.
Worked scenario two: best baseline FEV1 is 1.30 L; best post-bronchodilator FEV1 is 1.52 L. The plausible mistake is to compute the percentage change against the predicted FEV1 of 3.00 L, giving about 7 percent, and conclude there is no significant response. The better decision compares like with like: the change is 220 mL, which is roughly 17 percent of the baseline, meeting the benchmark. Why it matters: the wrong reference denominator turns a genuinely reversible result into a reported negative one, which would misdirect the clinical question the test was ordered to answer.
Calibration, verification and linearity: three checks that people conflate
Verification checks the device against a known injected volume, calibration adjusts the device when it drifts, and linearity checks accuracy across a range of volumes. Knowing which check you performed, and logging it, is itself part of quality assurance.
Separate the terms precisely. A daily check with a calibrated three-litre syringe is verification: you inject a known volume and confirm the spirometer reads it within the manufacturer's tolerance. If the reading falls outside tolerance, calibration or adjustment follows per the manufacturer's instructions, after checking for leaks and allowing the syringe and device to reach a stable temperature. Every check, pass or fail, belongs in the log with the syringe's own calibration status traceable - an uncalibrated reference syringe verifies nothing.
Linearity extends the idea across the measuring range: injecting known volumes at several points, for example one, two and three litres, to confirm accuracy is not confined to one value. A device accurate at three litres but reading low at one litre will distort results for patients with small lung volumes, exactly the patients where precision matters most. Many services build linearity checks into periodic maintenance rather than daily routine; practise explaining why a single-volume check cannot guarantee accuracy across the whole range, so the reasoning is ready when you need it in written answers.
A marked practice exercise: grade three sessions with a self-check rubric
Build a one-page rubric that walks the decision chain as fixed prompts, then mark three practice sessions against it and record every disagreement between your judgement and the modelled answer.
Construct the rubric as the chain itself, one prompt per link: device check logged and in date; each blow annotated for start quality, cough, termination and duration; repeatability judged across acceptable blows only; best values selected from acceptable data; interpretation consistent with ratio and FVC jointly; reversibility computed with the correct reference values; report states any quality limitations in plain language. Mark each prompt as met, partially met or not met, with a one-line justification. Three sessions is enough to expose your recurring weak link.
Run the exercise in two passes to sharpen it. On pass one, grade each session with the rubric hidden, then on pass two re-grade with the rubric visible and note exactly which prompt changed your verdict - that discrepancy identifies your weak link, and you can then design a targeted drill for it, for example re-examining every discarded blow before touching the repeatability prompt, or recomputing every reversibility percentage from the baseline before comparing against the threshold. Treat the rubric score as a learning milestone, not a pass prediction - a consistent full-mark self-check across three unseen sessions signals the chain is automatic, which is the point of the exercise.
- Device check: verification or calibration correctly named, logged, syringe traceable
- Per-blow acceptability: start, cough, termination, duration, leak each judged
- Repeatability: assessed across acceptable blows only
- Values: best acceptable FEV1 and FVC selected and justified
- Interpretation: ratio and FVC read together, cautious phrasing for possible restriction and mixed patterns
- Reversibility: absolute and percentage change against baseline, correct threshold cited
- Report: limitations and quality statement included in plain language
A preparation sequence that rehearses the chain, not isolated facts
Practise the full chain in single sittings, from equipment check through grading, interpretation, reversibility and report writing, using the current UK spirometry guidance and your local protocol as the source for exact thresholds.
An adaptable sequence: first, read the current ARTP spirometry guidance and your local standard operating procedure, noting the exact acceptability, repeatability and reversibility criteria they specify. Second, spend a block purely on curve annotation drills until artefacts are named on sight. Third, mark full sessions with the rubric from the previous section. Fourth, drill reversibility calculations against the baseline only. Fifth, write complete reports for graded sessions and compare wording and conclusions with reports from an experienced colleague in your service.
Rehearsing the chain end to end matters because each link supplies inputs to the next, so a weakness anywhere contaminates everything downstream. Practise explaining the reasoning at each step - why a blow was discarded, why a threshold was applied that way - rather than only naming a number, so the justification habit is in place before you need it under pressure. Concrete readiness checks before you consider yourself prepared: you can grade any blow and justify each criterion breached; you can complete the whole chain in one pass without consulting notes; your rubric self-checks are consistently strong across three unseen sessions; and you can state which guideline version your thresholds come from and why it governs.
- Readiness check: can you grade a blow and cite the specific acceptability criterion for each fault?
- Readiness check: can you run the full chain - device, acceptability, repeatability, interpretation, reversibility, report - unaided in one sitting?
- Readiness check: are your self-check rubric scores consistently high across three unseen sessions?
- Readiness check: can you name the guideline your thresholds come from and explain why the current version governs?
References and further reading
Use these references to explore the concepts and check the latest information from the relevant organizations.