Free NBRC PFT Practice Test: 50 Questions With Explanations

Answer: C. The 2019 ATS/ERS spirometry update allows ±3% (±2.5% for the spirometer plus ±0.5% for the syringe). For a 3.00-L syringe that is 2.91–3.09 L, and all three strokes sit above it. A failed check means you don't test patients until the cause is fixed and the verification passes. Likely causes include a damp or contaminated sensor, a syringe leak, or wrong ambient settings. There is no ±5% allowance (A). Correcting results after the fact (B) doesn't replace a passing check. Overestimated volumes aren't "conservative" (D); they can hide a genuinely low FVC. Source: 2019 ATS/ERS spirometry standard, Calibration verification.

Answer: A. The 2023 lung volume standard calls for daily physical calibration of the mouth-pressure transducer and the box signal. Calibrate more often when room temperature or pressure is changing. The isothermal lung analog check is a separate monthly accuracy validation, not a substitute for daily calibration (B, C). Biological controls supplement calibration; they don't replace it (D). Source: 2023 ERS/ATS lung volumes standard, Quality control.

Answer: B. The 2017 ERS/ATS DLCO standard sets a daily 3-L syringe check within 2.5%. An error of 0.08 L on 3.00 L is 2.7%, so this reading is within the spirometry tolerance but outside the DLCO tolerance. Volume error isn't harmless (C): DLCO is the product of KCO and VA, so an error in VA carries straight into DLCO. The 0.5% figure (D) is the accuracy of the calibration syringe itself, not the instrument's tolerance. Sources: 2017 ERS/ATS DLCO standard, Equipment calibration and quality control, item 2 (PDF p. 7); 2022 ERS/ATS interpretation standard, Gas transfer impairments (PDF p. 23; DLCO = KCO × VA).

Answer: D. The 2019 update says that if a filter is used for testing, it must also be in place for calibration and verification, so the check reflects the system patients actually blow through. Testing without it (A) verifies a different system. Verification is at least daily, not weekly (B). Filters are standard practice, not forbidden (C). Source: 2019 ATS/ERS spirometry standard, Calibration verification.

Answer: C. For adult plethysmographs, the 2023 standard applies the ±50 mL or 3% limit, whichever is greater, to the mean of five determinations. For 4.00 L, 3% is 120 mL, so a 90-mL error passes. Option A applies the 50-mL figure without the "whichever is greater" rule. There's no 1% rule (B). Biological controls are a separate check (D). Source: 2023 ERS/ATS lung volumes standard, Body plethysmography: Quality control (PDF p. 9).

Answer: B. In the 2023 standard, a sudden drop in helium concentration signals a leak. Because the calculation assumes all the lost helium was diluted into the lungs, a leak overestimates FRC. Discard the trial. Repeat after at least twice the previous dilution time, or longer in severe obstruction. Slow mixing produces a gradual curve, not a sudden step (A). Equilibration means less than 0.02% change over 30 seconds, not an abrupt fall (D). Option C names a real maintenance issue but doesn't explain a sudden helium drop. Source: 2023 ERS/ATS lung volumes standard, Helium dilution: Measurement technique, steps 5–7 and Quality control (PDF p. 15); Acceptability and grading (PDF p. 17).

Answer: C. The 2023 standard lists a sudden large rise in expired tracer concentration as evidence of a leak, and any evidence of leak means the trial is rejected. Room air is about 78% N2, so the observed break in the seal explains the abrupt rise. No cough, sigh or other breathing change is described to support release of trapped gas (A). The test ends when end-tidal N2 falls below 1/40 of its starting value for three consecutive breaths (B). Before repeating, wait at least twice the washout time. Applying an unexplained correction (D) does not repair a leak. Source: 2023 ERS/ATS lung volumes standard, Multiple-breath washout: Measurement technique, steps 5–8 (PDF pp. 11–12); Acceptability and grading (PDF p. 17).

Answer: D. The 2019 update requires setting zero flow with the spirometer blocked before calibration checks and patient tests, and repeating it if the zero level shifts. A drifting baseline is a "faulty zero-flow setting," which makes maneuvers unacceptable and unusable. You can't assume the software handles it (A). BTPS is a temperature and humidity conversion, not a zero (B). The syringe isn't involved when no air is moving (C). Source: 2019 ATS/ERS spirometry standard, Zero-flow; Table 7.

Answer: A. The 2017 DLCO standard says older systems may require another volume calibration check when room temperature changes by more than 3 °C. Here it changed 4 °C. The 2019 spirometry update notes that continuous temperature correction may be necessary when ambient temperature changes by more than 3 °C in under 30 minutes. BTPS conversion only works if the ambient temperature entered is correct (B). Stopping for the day (C) isn't required if the check passes. Barometric pressure isn't the variable that changed (D). Sources: 2017 ERS/ATS DLCO standard, Equipment calibration and quality control, item 2 (PDF p. 7); 2019 ATS/ERS spirometry standard, BTPS Adjustment.

Answer: C. The 2023 lung volume standard states that airway resistance shouldn't come from the same panting maneuver used for lung volumes. The two measurements have different optimal panting frequencies, and staying on the mouthpiece longer increases leak risk. Option B is still one maneuver. Helium dilution can't measure airway resistance at all (D), and it changes the test. Source: 2023 ERS/ATS lung volumes standard, Plethysmography.

Answer: B. The 2019 update requires the ±3% window for inspiration and expiration on flow-based devices; expiration-only applies to volume-based spirometers. Every inspiratory stroke is above 3.09 L. Averaging good and bad strokes (C) hides the failure. The expiratory strokes are fine (D). Inspiratory accuracy matters on flow sensors because maneuvers such as the FIVC check depend on it. Source: 2019 ATS/ERS spirometry standard, Calibration verification.

Answer: D. Today's value is 4.2 units (13.5%) below the mean. The 2017 standard says to repeat the test when a biological control deviates by more than 12%, or 3 mL/min/mmHg, from its previous mean. A confirmed deviation means the instrument needs evaluation before patients are tested. This exceeds the guideline's screening limits (A). Changing predicted values (B) or forcing a span (C) would conceal the discrepancy instead of finding its cause. Source: 2017 ERS/ATS DLCO standard, Equipment calibration and quality control, item 3 (PDF p. 8).

Answer: B. Flow sensors and gas analyzers both drift, so the ERS statement recommends calibrating them immediately before each test, not once a day (A). The flow sensor is checked with a certified 3-L syringe at three or more flow ranges and should agree within ±3%. Each gas sensor needs two calibration points, and the statement prefers two reference gases of known concentration over one gas plus room air (D). Warm-up is part of preparation, not a calibration (C). Source: Radtke T et al. ERS statement on standardisation of CPET in chronic lung diseases, 2019, Metabolic carts.

Answer: D. The AARC blood gas guideline says out-of-limit QC should trigger equipment troubleshooting, and QC must be verified "in control" before specimens are analyzed, with corrective actions documented. Repeating or averaging (A) doesn't fix a biased instrument; it reproduces the bias. A comment on the report (B) doesn't make an out-of-control result usable. Running the sample before QC is fixed (C) gets the order backward. Source: Davis MD et al. AARC Clinical Practice Guideline: Blood gas analysis and hemoximetry, 2013, §8.3.1.3 (journal p. 1698; PDF p. 5).

Answer: B. A syringe has no alveolar–capillary membrane, so no CO should "disappear." The 2017 standard expects the absolute value of calibration-syringe DLCO to be below 0.5 mL/min/mmHg. A higher value means the system thinks CO was taken up, which points to a leak or an analyzer problem. The 3-unit figure (C) is the biological control limit, a different test. Hemoglobin adjusts predicted values for patients (D), not an equipment check. Source: 2017 ERS/ATS DLCO standard, Equipment calibration and quality control, item 3 (PDF p. 8); Table 1 (PDF p. 5).

Answer: D. The 2019 update says that when disposable sensors are used, a new sensor from the patient-test supply should be tested each day. That way the check reflects the sensors patients actually use. A permanent reference sensor (A) checks something patients never touch. Factory calibration doesn't remove the daily requirement (B), and monthly checks are too infrequent (C). Source: 2019 ATS/ERS spirometry standard, Calibration verification.

Answer: B. The 2019 update lists a 4–6 hour hold for short-acting beta-agonists before bronchodilator responsiveness testing. Testing now risks a false-negative response, because the baseline may already be bronchodilated. Withholding depends on the test purpose and the clinician's instructions. If the ordering clinician needs the test done today, document the dose time on the report. Albuterol lasts hours, not one hour (A). Doubling the dose (C) changes the protocol, not the problem. Adolescents routinely perform this test (D). Source: 2019 ATS/ERS spirometry standard, Bronchodilator Responsiveness Testing and Table 8.

Answer: C. The 2017 ERS methacholine standard lists baseline airflow limitation as a relative contraindication and calls for discussion with the ordering physician or laboratory medical director before proceeding. It is defined as FEV1 below 60% of predicted or below 1.5 L in adults, and this adult fails the absolute-volume test. A low starting dose (B) doesn't remove a contraindication. Deep breaths to TLC (D) are discouraged, because they blunt the response. Source: 2017 ERS methacholine standard, p. 4, Contraindications—Low FEV1 and Table 1; p. 2, Inhalation protocol. Coauthor-uploaded full text.

Answer: D. Gas dilution and washout methods only measure gas that communicates with the airways. The 2023 standard lists underestimation of FRC in obstruction, bullae and emphysema as their known limitation (A, B). Plethysmography includes trapped and poorly ventilated gas. Spirometry can't measure TLC (C). One plethysmography caveat: keep panting near 0.5–1.0 Hz, because fast panting overestimates FRC in obstruction. Source: 2023 ERS/ATS lung volumes standard, pp. 4–5, Measurement of FRC and Table 1; pp. 7–8, body plethysmography.

Answer: C. Nitrogen washout has the patient breathe 100% oxygen. The 2023 lung volume standard recommends doing DLCO before any multiple-breath nitrogen washout, because leftover oxygen can lead to an underestimated DLCO. The same logic is why the 2017 DLCO standard asks patients to be off supplemental oxygen for at least 10 minutes before testing when that's clinically acceptable. Neither one minute (D) nor "right away" (A) follows the recommended test order or establishes adequate recovery from oxygen exposure. The two tests aren't independent (B). A sequence that fits the standard is spirometry, DLCO, nitrogen washout, bronchodilator if ordered, then repeat spirometry. Sources: 2023 ERS/ATS lung volumes standard, pp. 6–7, Sequence of lung function measurements; 2017 ERS/ATS DLCO standard, p. 9, Patient condition.

Answer: A. When you're measuring change, the standard recommends two 6MWTs and recording the best. Rest at least 30 minutes between them, until heart rate and SpO2 return to baseline. In COPD, the second walk averaged about 26 m further, a learning effect that would otherwise look like improvement after rehabilitation. Averaging (C) or using the first walk (D) keeps that bias. Skipping the second test (B) may be reasonable for one-off staging or after recent testing. Source: 2014 ERS/ATS field walking test standard, journal pp. 1430–1431, adult scope and Reliability and learning effect for 6MWD; p. 1439, Test repetition (PDF pp. 3–4 and 12).

Answer: C. Exercise challenge is an indirect test. Breathing large volumes of dry air dries the airway surface, which triggers mediator release and bronchoconstriction. The protocol therefore uses dry air, a nose clip (so all air passes the mouth), a ramp of 2–3 minutes, and sustained high intensity for at least 4 minutes, preferably 6. The preferred target is 60% of maximum voluntary ventilation; a heart rate above 85% of predicted maximum can serve as a surrogate. FEV1 is then measured repeatedly over the next 30 minutes. Humid air at low intensity (A) weakens the stimulus. Three minutes without a nose clip (B) is too short and lets air be conditioned in the nose. Option D isn't the ordered test. Sources: 2018 ERS indirect airway challenge standard, pp. 6–7, Exercise challenge and Table 2; p. 8, Post-challenge spirometry protocol. The dry-air value is specified in the 2013 ATS exercise-induced bronchoconstriction guideline, journal p. 1019 (PDF p. 4), Exercise Challenge Testing to Identify EIB.

Answer: D. The 2019 rule is BEV no more than 5% of FVC or 0.100 L, whichever is greater. Here that's 0.15 L, so 0.18 L fails. A high BEV means a hesitant, slow start, which makes FEV1 unreliable. That affects both FEV1 and FVC acceptability and usability. There's no 0.20-L limit (A). The 0.100-L floor applies at all ages (B). Repeatability doesn't rescue an unacceptable start (C). Source: 2019 ATS/ERS spirometry standard, Within-Maneuver Evaluation, Table 7 and the BEV discussion.

Answer: A. In Table 7 of the 2019 update, "no cough in the first second" is an FEV1-only criterion, required for both acceptability and usability. A cough inside the first second disqualifies FEV1 entirely. FVC has its own criteria (BEV, zero flow, no glottic closure, end-of-forced-expiration and others), so the same maneuver can still contribute an acceptable FVC. Option B overextends the rule. Options C and D underapply it. Source: 2019 ATS/ERS spirometry standard, Table 7 and Within-Maneuver Evaluation, first-second cough.

Answer: B. The 2019 update defines EOFE by any of three indicators. Table 7 specifies a plateau of no more than 0.025 L of volume change in the last second. Reaching 15 seconds of forced expiratory time also counts. The third indicator, for patients who can't exhale long enough, is an FVC within the repeatability tolerance of or greater than the largest prior FVC. There is no minimum exhalation time (A, C). Fifteen seconds is a point at which EOFE is reached, not a requirement. Additional 15-second efforts are not required to establish a plateau already demonstrated (D). The older 6-second minimum often seen in textbooks no longer applies. Source: 2019 ATS/ERS spirometry standard, Table 7 (EOFE indicators) and Within-Maneuver Evaluation.

Answer: C. The 2023 standard targets 0.5–1.0 Hz. It rejects trials above 2.0 Hz, and above 1.5 Hz when spirometry shows significant obstruction. At fast frequencies, mouth pressure underestimates the change in alveolar pressure in obstructed lungs, so FRC is overestimated. Good repeatability (B) can't fix a systematic error. Panting below 0.5 Hz (D) causes problems with the box's controlled leak. Source: 2023 ERS/ATS lung volumes standard, pp. 7–8, Measurement of FRC using body plethysmography; Table 2, p. 17.

Answer: B. The FRC is linked to an IC (giving TLC) and then a slow expiratory VC (giving RV). Forced expirations (A) can cause dynamic airway collapse and air trapping in obstructed patients, which overestimates RV. The 2023 standard doesn't recommend unlinked spirometry for plethysmography (C). TLC must be measured, not estimated (D). Source: 2023 ERS/ATS lung volumes standard, pp. 4–5, Derivation of lung subdivisions (linked FRC, IC and slow EVC); Figure 3, p. 6.

Answer: D. VI is 3.40 ÷ 4.20 = 81% of VC. The 2017 standard wants at least 90%, or at least 85% with VA within 200 mL or 5% (whichever is greater) of the largest VA from another acceptable maneuver. This 81% inspired volume fails both acceptability routes; reduced inspiration can affect the measurement. An 81% VI/VC is not grade A (A), and VI clearly matters (B). The test gas must wash out before the next maneuver: wait at least 4 minutes on classical systems, and consider 10 minutes in airflow obstruction (C). Source: 2017 ERS/ATS DLCO standard, pp. 9–10, Inspiratory manoeuvres; p. 12, Manoeuvre intervals in classical systems; Table 3 and footnote, p. 22 (corrected November 2018 version).

Answer: B. Deep inspirations to TLC have a bronchoprotective, bronchodilating effect that blunts the response. The 2017 standard therefore favors at least one minute of tidal breathing with these nebulizers; dosimeters instead use a calculated breath count. It reports the delivered dose (PD20). Options A and D build deep breaths into every dose. Option C changes deposition and isn't a recognized method. Source: 2017 ERS methacholine standard, p. 2, Inhalation protocol; pp. 9–10, Duration of nebulisation and Procedure steps 4–5. Coauthor-uploaded full text.

Answer: C. In the 2014 standard, the clock never stops. Patients may rest standing or sitting and should resume when able. Encouragement is limited to the standard phrases, every 30 seconds once SpO2 is 85% or higher. Record the time stopped and the number of stops. The assessor stops the test for SpO2 below 80% or concerning symptoms, including intolerable dyspnea; no stopping criterion is present here (B). Pausing the timer (A) invalidates the distance. Setting the pace (D) is explicitly avoided; assessors walk behind. Source: 2014 ERS/ATS field walking test standard, journal p. 1439, Reasons for the assessor to stop an exercise test; p. 1440, 6MWT Conduct and Table 6 (PDF pp. 12–13).

Answer: D. A palm that doesn't regain color suggests inadequate collateral flow through the ulnar artery. Puncturing that radial artery is then considered unsafe, because injury could compromise blood supply to the hand. Pressure or needle size (A, B) doesn't change the collateral-flow problem. Repeating the test until it "passes" (C) ignores the finding. Source: WHO guidelines on drawing blood: best practices in phlebotomy (2010), Annex I, Modified Allen test, printed p. 85 (PDF p. 101); section 5.2.2, printed p. 32.

Answer: A. For patients older than 6, the 2019 update requires the two largest FVCs and the two largest FEV1s to agree within 0.150 L. FEV1 passes (0.08 L), but FVC doesn't (0.17 L). Keep trying, up to about eight maneuvers for adults, and stop sooner if the patient can't continue or FEV1 from an acceptable maneuver falls below 80% of its starting value. FEV1 alone isn't enough (B). The standard reports the largest acceptable values, not averages (C). Repeatability is assessed as the maneuvers are obtained, not delayed until fatigue (D). Source: 2019 ATS/ERS spirometry standard, Between-Maneuver Evaluation, Maximum Number of Maneuvers and Reported Values.

Answer: C. The 2019 limit is FIVC − FVC ≤ 0.100 L or 5% of FVC, whichever is greater. Here 5% of FVC is 0.17 L, and the difference is 0.22 L. The maneuver didn't start from full inspiration, so FVC and FEV1 are understated. Coach a complete inhalation before the blast. The 0.25-L figure (A) doesn't exist. The check applies to everyone (B). Option D reverses the logic: FIVC can equal or slightly exceed FVC, just not by more than the limit. Source: 2019 ATS/ERS spirometry standard, Maximal inspiration after forced expiration; Within-Maneuver Evaluation and Table 7 (FIVC minus FVC).

Answer: B. The 2017 standard requires at least two acceptable maneuvers within 2 mL/min/mmHg. These differ by 2.9. Once repeatable maneuvers are obtained, the mean is reported. More than five maneuvers are not recommended because each test raises COHb (about 3.5% over five) and lowers measured DLCO. After only two attempts, seek better repeatability before reporting the mean (A). If repeatability cannot be achieved after further testing, report the average acceptable DLCO with a quality caution. Reporting the higher value (C) is not the reporting rule. Retesting without the washout interval (D) carries over test gas. Source: 2017 ERS/ATS DLCO standard, p. 12, Manoeuvre intervals in classical systems; pp. 21–22, Repeatability, suboptimal-session reporting and Table 3 (corrected November 2018 version).

Answer: D. The 2023 repeatability test is (highest − lowest) ÷ mean. That gives 0.20 ÷ 3.207 = 6.2%, above the 5% target for three values. Keep testing for three that agree within 5%; the standard notes that values with poorer repeatability may still be useful if fatigue ends the session. Checking pairs (B) isn't the criterion. Reported FRC is a mean of acceptable values, not the highest (C). Source: 2023 ERS/ATS lung volumes standard, Repeatability (PDF p. 16); Reporting—Selection of manoeuvres (PDF pp. 18–19).

Answer: B. Dyshemoglobins such as carboxyhemoglobin change the light absorption that conventional two-wavelength oximeters rely on, which produces false readings. A CO-oximeter measures the hemoglobin species directly. The error runs toward overestimation, not underestimation (A). Option C ignores COHb. CO-oximetry measures hemoglobin fractions, not PaO2 (D). Sources: CDC clinical guidance for carbon monoxide poisoning, Confirmation of Diagnosis; Buckley et al., The pulse oximetry gap in carbon monoxide intoxication (1994), Abstract—Results and Conclusion.

Answer: C. For children 6 and younger, the 2019 update allows 0.100 L or 10% of the highest value, whichever is greater. Ten percent of 1.02 L is 0.102 L, so the limit is 0.102 L, and the 0.08-L difference passes. The 0.150-L rule (B) is for patients older than 6. FEV1 and FVC repeatability are judged separately. There's no 5% rule (A) or exact-match rule (D). Source: 2019 ATS/ERS spirometry standard, Table 7; Between-Maneuver Evaluation.

Answer: A. Room air has a higher PO2 than this patient's arterial blood and almost no CO2. Gas equilibrates across the bubble, so PO2 drifts up and PCO2 drifts down. Patterns B and C run the wrong direction for air contamination. Prompt processing does not make an air-contaminated specimen acceptable (D); removing the bubble later does not restore the original gas values. The AARC blood gas guideline lists a specimen with visible air bubbles as one not to analyze, so a sample like this should be flagged under your lab's specimen-rejection protocol. Sources: Biswas et al., Blood gas analysis: effect of air bubbles in syringe and delay in estimation (1982), Abstract—air-bubble experiment results; AARC blood gas and hemoximetry guideline, 2013, §4.4 (printed p. 1695; PDF p. 2) and §6.1.2.1 (printed p. 1696; PDF p. 3).

Answer: B. The 2022 standard defines a significant bronchodilator response as a change of more than 10% of the predicted value for FEV1 or FVC: 0.22 ÷ 3.00 = 7.3%. The older "12% and 200 mL from baseline" rule (A) would call this positive. This is a case where the two methods disagree. No 200-mL-only rule exists (C), and the 2022 criterion needs only the predicted value, not a z-score for the change (D). Source: 2022 ERS/ATS interpretation standard, Bronchodilator responsiveness (PDF pp. 10–11); Box 1 (PDF p. 11).

Answer: A. For adolescent and adult males: predicted DLCO × [1.7 × Hb ÷ (10.22 + Hb)] = 30.0 × (17 ÷ 20.22) = 30.0 × 0.841 = 25.2. Anemia lowers the predicted value. Option C uses the constant for females and children under 15 (9.38). Option B ignores the anemia. Option D divides instead of multiplies. The 2017 standard applies this adjustment to the predicted value, not the measured one. Source: 2017 ERS/ATS DLCO standard, Adjustment for haemoglobin; equations 31–32 (PDF p. 23).

Answer: C. Obstruction is FEV1/FVC below the lower limit of normal (z below −1.645), and −2.1 qualifies even though the ratio is 0.74. The fixed 0.70 cutoff (A) is strongly discouraged, because it misclassifies young and old patients. Severity is graded by the FEV1 z-score. The moderate range runs from −2.51 to −4. At −3.2, this is moderate physiological impairment. This grade describes lung-function impairment, not overall disease severity. Restriction (D) can't be called from spirometry; it needs a TLC below the LLN. Source: 2022 ERS/ATS interpretation standard, Severity of lung function impairment (PDF pp. 13–15); Figure 7 (PDF p. 14); Table 5 (PDF p. 18); Restrictive impairments (PDF p. 21).

Answer: A. Mean TLC = mean FRC + mean linked IC for the same selected maneuvers = 3.40 + 2.10 = 5.50 L (D is the TLC, not the RV). The 2023 standard reports RV as TLC minus the largest VC: 5.50 − 3.60 = 1.90 L. Option C uses the smaller linked VC (5.50 − 3.50), which overstates RV. Option B subtracts IC from FRC, which isn't a lung volume. Source: 2023 ERS/ATS lung volumes standard, Derivation of lung subdivisions (PDF p. 5); Table 3 and Reporting—Selection of manoeuvres (PDF p. 18).

Answer: D. The fall is 0.66 ÷ 3.00 = 22%. A fall of 20% or more after diluent meets the standard's cancellation criterion, with any needed rescue bronchodilator and recovery checks. Continuing (A, B) or escalating (C) would ignore that stopping rule. Source: 2017 ERS methacholine standard, p. 10, Procedure steps 6–7; p. 5, Precautions for patient safety; p. 13, Data presentation. Coauthor-uploaded full text.

Answer: D. VA ÷ TLC = 3.9 ÷ 5.8 = 0.67. The 2022 standard says a ratio well below about 0.85–0.90 suggests gas maldistribution — the test gas didn't reach all of the lung — so DLCO may be underestimated. A healthy VA is close to TLC, so A is wrong. Swapping volumes (B) isn't a recognized correction. KCO rises as lung volume falls, so a "normal" KCO doesn't cancel a low VA (C). Source: 2022 ERS/ATS interpretation standard, Gas transfer impairments: VA/TLC and interpretation of KCO at low VA (PDF p. 23).

Answer: A. The 2019 update's third EOFE indicator is for patients who can't exhale long enough to plateau, such as children with high elastic recoil. Their FVC counts if it is within repeatability tolerance of, or greater than, the largest prior FVC in the same testing set. For a 9-year-old the tolerance is 0.150 L, and 2.12 − 2.05 = 0.07 L. The plateau isn't the only route (B), and there's no minimum time (C). Because an EOFE acceptability criterion is met, the FVC can be acceptable rather than merely usable (D). Source: 2019 ATS/ERS spirometry standard, Table 7, third EOFE criterion and footnote; Within-Maneuver Evaluation.

Answer: C. The 2017 standard asks patients not to smoke on test day. It requires recording the time of the last cigarette and correcting for CO back-pressure after recent or heavy smoking, because elevated COHb lowers measured DLCO. That reverses B and contradicts A. Oxygen right before the test (D) also biases DLCO downward, and the standard asks for no supplemental O2 for 10 minutes beforehand when that's clinically acceptable. Source: 2017 ERS/ATS DLCO standard, Patient condition (PDF p. 9); Adjustments for carboxyhaemoglobin concentration and carbon monoxide back-pressure (PDF pp. 24–25).

Answer: B. A reduced FVC and FEV1 with a normal ratio and a normal TLC is what the 2022 standard calls a non-specific pattern. It can reflect submaximal effort, early small-airway disease or other causes. Restriction (A) requires TLC below the LLN. The ratio is normal, so the measured pattern is neither spirometric obstruction (C) nor a mixed ventilatory impairment (D). Source: 2022 ERS/ATS interpretation standard, Table 5 (PDF p. 18); Non-specific pattern (PDF p. 19).

Answer: D. Both the ratio and TLC are below the LLN (z under −1.645). The 2022 standard defines that combination as a mixed defect, and it can be confirmed only with a measured TLC. Option A misses the restrictive component established by the low TLC. The ratio being below the LLN isn't dismissed (B). A non-specific pattern (C) requires a normal ratio and a normal TLC. Source: 2022 ERS/ATS interpretation standard, Mixed ventilatory impairments and Table 7 (PDF p. 22).

Answer: A. Lying down shifts abdominal contents against the diaphragm. A healthy diaphragm handles this with only a small loss of VC, but a weak one can't, so VC falls markedly. This drop is about 36%, far beyond a normal postural change (D). The ATS/ERS respiratory-muscle statement uses the upright-to-supine VC fall as a sign of diaphragm weakness. Obstruction (B) isn't assessed by this comparison. VC does change with position (C), which is the whole point of the test. This finding warrants further assessment; it does not establish the diagnosis by itself. Sources: ATS/ERS Statement on Respiratory Muscle Testing (2002), Static Lung Volumes (printed p. 521; PDF p. 4); Fromageot et al., Supine fall in lung volumes in the assessment of diaphragmatic weakness in neuromuscular disorders (2001), Abstract—Results and Conclusions; study of 24 patients with neuromuscular disease.

Answer: D. The 2017 categories by delivered dose are: over 400 µg normal; 100–400 µg borderline; 25–100 µg mild; 6–25 µg moderate; under 6 µg marked. At 60 µg, the result is mild. The interpretation still depends on the clinical picture, symptoms and medications held. The standard reports PD20 (delivered dose) instead of PC20 (concentration), so results can be compared across nebulizers when their delivery characteristics and dosing protocols are known. Source: 2017 ERS methacholine standard, Table 6, p. 14; pp. 13–14, Interpretation of direct bronchial challenge tests; p. 2, Delivery devices. Coauthor-uploaded full text.