NBRC PFT Exam Prep: Free CPFT & RPFT Study Guide

Use this free NBRC PFT exam prep guide to review CPFT and RPFT topics, work through 20 original questions, and follow a six-week study plan.

Try the first calculation

Worked example 1: the denominator changes the answer. FEV1 is the forced expiratory volume in one second. These are hypothetical, technically acceptable measurements:

Pre-bronchodilator FEV1: 2.00 L · Post-bronchodilator FEV1: 2.26 L · Predicted FEV1: 3.20 L

Using the 2022 European Respiratory Society/American Thoracic Society (ERS/ATS) standard, what is the change as a percentage of predicted FEV1, and does that FEV1 change meet the response threshold?

Where your 100 scored points come from

The 100 scored-item specifications also allocate 10 pediatric questions (90 are general), with no more than 3 blood gas analysis and 2 CO-oximetry/hemoximetry analysis questions. (PFT Detailed Content Outline, effective October 2022)

What this tells you: 83 of the 100 scored questions ask you to apply or analyze, not just recall. Memorizing the numbers is step one. The exam scores whether you can use them on a calibration result, a tracing, or a report. Both the CPFT and the RPFT come from this same content; the RPFT just takes more correct answers.

Jump to: Study plan · Which standards · Review by domain · 20 practice questions · Exam facts

Your six-week study plan

Assumptions: five one-hour sessions a week (30 hours total), some pulmonary function lab exposure, and a goal of the high (RPFT) cut. This is a planning starting point, not an official requirement or a promise of readiness. If a topic is new to you, give it more time.

Each one-hour session: 10 minutes recalling the last session from memory, 25 minutes learning the topic from this page and the linked standard, 20 minutes applying it (a practice question, a tracing, or a calculation), and 5 minutes writing down what you'll fix next.

Short on time? Keep the order. With three weeks, double up to about two hours a session. With half-hour sessions, stretch to twelve weeks. Already work in a busy PF lab? After checking your understanding of the tests you run daily, move time toward the ones you rarely see, such as challenge testing or plethysmograph quality checks. Retaking? Start with your error log, not Week 1.

Which ATS/ERS standards to study

NBRC says its PFT exam committee writes questions from current American Thoracic Society (ATS) and European Respiratory Society (ERS) standards, and warns that textbooks may lag behind them. These are relevant technical standards from NBRC's preparation reading list:

Spirometry: 2005 or 2019?

Study the 2019 ATS/ERS spirometry update listed on NBRC's current exam-preparation standards page. A February 2020 NBRC notice said questions would continue to use the 2005 standard until a further announcement. That older notice remains online, but neither page provides a specific transition date.

Use the comparison below to recognize differences in older study material; the 2005 column is historical context. The practice explanations identify the standard used where the version affects the answer.

For the 2019 repeated-FVC route, the FVC must be greater than, or within the repeatability tolerance of, the largest earlier FVC in the same pre- or post-bronchodilator set when a plateau or 15-second expiration cannot be achieved. A first maneuver without a plateau and lasting less than 15 seconds qualifies provisionally until its FVC is compared with subsequent maneuvers. Similar FVC values do not excuse a leak, glottic closure, or another acceptability failure. (2019 standard, Table 7 and End of forced expiration)

Medication withholding depends on the test's purpose and the referring clinician's instructions. For bronchodilator-response testing when withholding is indicated, the 2019 suggested intervals are: short-acting beta-agonist 4–6 h, short-acting anticholinergic 12 h, long-acting beta-agonist 24 h, ultra-long-acting beta-agonist 36 h, and long-acting anticholinergic 36–48 h. Tests assessing response on the existing treatment regimen generally do not require withholding. These are not methacholine-challenge withholding intervals. (2019 standard, Patient preparation and Table 8)

High-yield review by domain

Instrumentation and equipment: can you trust the measurement?

Verification vs calibration. Verification checks whether a device reads a known volume correctly. Calibration establishes the relationship between the sensor's signal and a known flow or volume. Under the 2019 standard, the spirometer itself must be accurate within ±2.5%; the daily 3-L syringe check allows ±3% because the syringe adds its own 0.5%. Judge each reading separately. If one stroke is 3.12 L, that's 4% high and fails, even if an average of three strokes looks fine. A failed check means no patient testing until the cause is fixed and a repeat check passes. A dropped syringe counts as out of calibration until the syringe itself is checked. (2019 standard, Device Quality Assurance)

BTPS means body temperature, ambient barometric pressure, saturated with water vapor. Lungs hold gas at body temperature, saturated with water vapor. Gas measured at ambient temperature and pressure, saturated (ATPS), has cooled and shrunk, so the correction to BTPS raises the volume at normal room temperatures. For this ATPS volume measurement, omitting the correction underestimates the BTPS volume. (2019 standard, BTPS Adjustment)

Gas dilution and washout systems. Closed-circuit helium dilution rebreathes the same gas, so a chemical absorber removes CO2 and oxygen is added to replace what the patient uses. Rising circuit CO2 points to the absorber. In nitrogen washout, a sudden jump in exhaled nitrogen can indicate a leak, and the test should be stopped and investigated. (2023 lung volume standard, pp. 11, 13–14)

Plethysmograph checks. The body box is checked with a model lung of known volume. Filling the model with thermal mass such as copper wool and moving air at 0.5–1 Hz mimics the near-constant temperature of gas in real lungs. After the door closes, allow roughly 30 seconds to 2 minutes for temperature to settle. Patients pant at 0.5–1 Hz; panting faster than about 1.5 Hz can overestimate FRC. (Same standard, pp. 8–9)

Blood gases and CO-oximetry. If analyzer controls fail and stay out of range, troubleshoot and get acceptable controls before running patient samples. Expel visible air bubbles before mixing. A sample held over 30 minutes at room temperature in a plastic syringe is not acceptable under this guideline; some circumstances require faster analysis, so 30 minutes is not permission to delay. When carbon monoxide exposure is possible, measure with CO-oximetry (hemoximetry); a calculated saturation can overestimate oxyhemoglobin. (AARC guideline, 2013, §§4.4–4.5, 6.1.6, 8.3.1.3, 8.4.1, 14.4) The outline caps blood gas analysis at three scored questions and CO-oximetry/hemoximetry analysis at two; related equipment and procedure topics also appear elsewhere.

Procedures: is the maneuver valid?

Spirometry. FEV1 is the volume blown out in the first second; FVC is the total volume exhaled forcefully and completely after a full inhalation. Two different questions decide validity. Acceptability asks whether one maneuver was done right (good start, full effort, proper end). Repeatability asks whether the best acceptable maneuvers agree with each other. Check FEV1 and FVC repeatability separately: one can pass while the other fails.

Quick check. FVC 4.00 L, back-extrapolated volume 0.18 L. The limit is 5% of FVC (0.20 L) or the fixed value (0.150 L in 2005, 0.100 L in 2019), whichever is greater. That's 0.20 L under both versions, so 0.18 L meets this volume criterion.

DLCO (2017 standard). Diffusing capacity of the lung for carbon monoxide (DLCO) measures carbon monoxide transfer from the lungs into the blood. For a valid test, the breath in should be at least 90% of the largest vital capacity (at least 85% but under 90% can be accepted if alveolar volume is within 200 mL or 5%, whichever is greater, of the largest alveolar volume from another acceptable maneuver), inhaled fast (85% of it in under 4 seconds), and held for 10 ± 2 seconds. On classic systems, wait at least 4 minutes between tests. Report the mean of at least two acceptable tests within 2 mL/min/mmHg of each other. More than five maneuvers is not recommended: each one adds carbon monoxide to the blood and nudges DLCO down. (DLCO standard, pp. 10–12, 21–22)

Methacholine challenge (2017 standard). The end-point is a 20% fall in FEV1 from the post-diluent value (or the pre-challenge value if no diluent step is used). In the supervised challenge protocol, once that end-point is reached, stop methacholine, give a fast-acting bronchodilator, and repeat spirometry. The standard prefers reporting PD20 (the delivered dose that causes a 20% fall) over PC20 (the concentration), because dose compares better across nebulizers. It lists a starting FEV1 below 60% of predicted, or below 1.5 L in adults, as a relative contraindication. (Methacholine standard, pp. 4, 8–11)

Six-minute walk test (2014 standard, adults with chronic respiratory disease). Use a flat, straight course of 30 m or more, and keep it the same for repeat tests. Patients usually walk farther the second time as they learn the test, so when measuring change, do two tests and record the better distance. If the patient stops to rest, the timer keeps running. (Field walking standard, pp. 1431, 1440)

Respiratory muscle strength. Routine maximal inspiratory pressure (MIP) is measured at or near residual volume; maximal expiratory pressure (MEP) at or near total lung capacity. The starting lung volume affects muscle length and elastic recoil, so it must match the method and reference values used. (ATS/ERS respiratory muscle testing statement, 2002, p. 531, Maximal Static Inspiratory and Expiratory Pressure)

Also on the outline: oxygen assessment and titration at rest or with exercise, instructing patients in home spirometry and pulse oximetry, monitored exercise testing (ECG, blood pressure, SpO2), and indirect challenges (exercise, eucapnic voluntary hyperpnea, mannitol). Use the content outline as your checklist so nothing is left out.

Data Management: what does the result actually show?

A study sequence using the 2022 ERS/ATS routine interpretation standard: First check test quality and the reference equations. Then ask:

1. Is FEV1/FVC below the lower limit of normal (LLN)? The LLN is the 5th percentile of the healthy reference population, a z-score of −1.645. Below it means airflow obstruction.
2. Is FVC low with a normal ratio? That's only possible restriction. Spirometry can't confirm it.
3. Is TLC below the LLN? That confirms restriction. A low ratio plus a low TLC is a mixed pattern.
4. Bronchodilator response: a change of more than 10% of the predicted value in FEV1 or FVC. This routine interpretation standard replaces the older "12% and 200 mL from baseline" rule.
5. Severity of lung function impairment uses z-scores. The ATS quick-reference guide, Figure 3, lists mild −1.65 to −2.5, moderate −2.5 to −4, and severe below −4. Physiological impairment is not the same as overall disease severity.
6. DLCO: interpret alongside lung volumes and hemoglobin.

(2022 ERS/ATS interpretive standard)

Two context notes. First, COPD diagnosis is a different setting: GOLD uses a post-bronchodilator FEV1/FVC below 0.70 in the clinical assessment of suspected COPD. A ratio alone does not establish a disease diagnosis. (ERS interpretation guidance, fixed-ratio discussion; 2022 ERS/ATS standard, classification of physiological impairments) Second, reference equations: use ones that cover the patient's age. Race-neutral GLI Global spirometry equations cover ages 3 to 95; that age range does not apply to every GLI test family. (ERS reference-equation guidance, Choosing the reference values; ATS statement, 2023)

Worked example 2: lung volume arithmetic.

Use technically satisfactory measurements linked to the same stable end-expiratory level. Functional residual capacity (FRC) is 3.2 L, expiratory reserve volume (ERV) is 1.0 L, and inspiratory capacity (IC) is 2.6 L. Calculate residual volume (RV) and total lung capacity (TLC).

RV = FRC − ERV = 3.2 − 1.0 = 2.2 L

TLC = FRC + IC = 3.2 + 2.6 = 5.8 L

Check: vital capacity (VC) = IC + ERV = 3.6 L, and TLC − VC = 5.8 − 3.6 = 2.2 L = RV. ✓

RV/TLC = 2.2 ÷ 5.8 × 100 = 37.9%, or 38% rounded to a whole percent. Whether that's normal depends on reference limits for this patient, not on the number alone.

Source: 2023 lung volume standard, pp. 3–4, definitions and linked volume relationships.

Plethysmography vs dilution. The body box measures all compressible gas in the chest, including gas trapped behind narrowed airways. Dilution and washout only reach gas that mixes with the airways, so they can underestimate volumes in severe obstruction, bullae, or emphysema. A big gap between methods is a finding, not automatically an error. Plethysmography can also overestimate volume in severe obstruction, so the difference alone does not quantify trapped gas. (2023 lung volume standard, p. 4)

Hemoglobin and DLCO. Anemia lowers DLCO because there's less hemoglobin to bind carbon monoxide. The 2017 standard adjusts the predicted value for hemoglobin, which can move a "low" result toward normal. Recent smoking raises carboxyhemoglobin and lowers DLCO too, which is why the time of the last cigarette is recorded. (DLCO standard, pp. 9, 23)

20 original practice questions

Original, unofficial practice written by Castleport Test Prep. These are not NBRC exam questions. The mix is 6 Instrumentation, 8 Procedures, and 6 Data Management. This is a teaching sample of selected topics; 20 questions cannot measure your readiness. Use your misses to decide what to study next.

Instrumentation / Equipment

Procedures

Data Management

Review your misses

A question you missed is only useful if you know why. Keep a simple log as you go:

Start your next study session with a rule you missed or could not explain. Use the points table to keep track of broader coverage, including topics this short set does not test. When you can explain why every wrong option is wrong, move on.

For optional official practice, NBRC's free practice exams page lists a PFT practice exam. NBRC's instructions say to finish it in one sitting because results are not saved if you exit. This page's 20 questions and explanations remain available here without an account.

Exam facts: scores, eligibility, fees, retakes

The NBRC Pulmonary Function Technology (PFT) exam is one test with two credential outcomes: Certified Pulmonary Function Technologist (CPFT) and Registered Pulmonary Function Technologist (RPFT).

Quick facts: 115 multiple-choice questions (100 scored, 15 unscored pretest) · 2 hours · $200 first attempt, $170 repeat · content outline effective October 2022 (NBRC)

Scoring. You get one point per correct scored question. Pretest questions don't count. As of NBRC's current scoring publication (Table 1), the low cut score is 61 correct answers (CPFT) and the high cut is 74 (RPFT; you also earn the CPFT). The same publication gives a lower boundary for each cut: 50 for the low cut and 63 for the high cut. Scores below 50 relative to the CPFT cut, or below 63 relative to the RPFT cut, fall outside the publication's stated 99% margin of error. NBRC uses this to discuss remediation after a failed result. These are score-interpretation boundaries, not alternative passing scores, retake-eligibility rules, or a way to interpret this page's practice score. Cut scores can change, so check NBRC's current publication before you test.

Eligibility. You must be 18 or older and meet one of these (NBRC):

• Graduation with at least an associate degree from an entry-into-practice respiratory therapy program supported or accredited by CoARC (the Commission on Accreditation for Respiratory Care)
• An NBRC CRT or RRT credential
• 62 semester hours of college credit from a regionally accredited school (or equivalent), including college-level biology and mathematics
• A CPFT credential, if you're going for the RPFT

NBRC doesn't list a lab-experience requirement for the 62-credit route. Some third-party pages still show older rules, so go by NBRC.

Fees. $200 for a first attempt, $170 for a repeat (candidate handbook, rev. 09/03/2026, p. 8). Eligible AARC members can get a one-time $40 discount on a first application to one of the eligible examinations. Register for the benefit, then start the application through the link in AARC's emailed instructions and use it when applying and paying; it cannot be applied retroactively. (AARC conditions and instructions)

Applying and testing. Apply online or on paper; there is no application deadline. Once your application is accepted, the handbook gives 90 calendar days to take the exam. Check the assigned eligibility period shown with your application. The separate one-year record-inactivity rule applies when there has been no examination scheduled or indication of a desire to attempt one; it does not extend the 90-day period. You test by computer at a PSI assessment center by appointment, Monday through Saturday, subject to holidays and site availability. Bring two current IDs with your name and signature, one with a photo; student and employee IDs don't count. (NBRC; handbook, pp. 8, 10–11)

Results. You get score information at the test center, and a score report is emailed. (Candidate handbook, p. 12)

Retakes. The first two PFT attempts have no waiting-period restriction. Before the third and every later attempt, you must wait at least 180 days. (NBRC)

Common questions

I already have the CPFT. If I retake for the RPFT and score lower, do I lose it? No. NBRC says you can retake the exam as many times as needed for the RPFT without affecting your existing CPFT. The 180-day wait still applies after your first two attempts. (NBRC PFT FAQ)

Does the 2027 NBRC exam change affect the PFT exam? NBRC's 2027 announcement covers the new respiratory therapist exam for the CRT and RRT, and it doesn't mention the PFT exam. The PFT outline is still the October 2022 version. (NBRC 2027 announcement; current content outlines)

Is a CPFT or RPFT a state license? No. It's a national credential from NBRC. Whether you need a state license for your job depends on your state and role, so check with your state's licensing board and your employer. (Candidate handbook, NBRC and State Licensure, p. 7)

Sources

Last verified: October 30, 2026 — NBRC exam format, scoring, eligibility, application period, fees, and retake rules; the PFT content outline; and the cited passages supporting the teaching and practice answers.

NBRC

• Registered Pulmonary Function Technologist (RPFT) exam page and PFT FAQs
• Candidate Handbook, rev. 09/03/2026
• PFT Detailed Content Outline, effective October 2022
• Accuracy of a Testing Result, Part 1 (cut scores, Table 1)
• ATS and ERS Update Standards Critical for Exam Preparation
• 2019 Spirometry Standard Update statement
• Free Practice Exams
• Examination Changes Coming in 2027

Standards and guidelines

• Miller MR, et al. Standardisation of spirometry. Eur Respir J. 2005;26:319–338.
• Graham BL, et al. Standardization of Spirometry 2019 Update. Am J Respir Crit Care Med. 2019;200(8):e70–e88.
• Graham BL, et al. 2017 ERS/ATS standards for single-breath carbon monoxide uptake in the lung. Eur Respir J. 2017;49:1600016.
• Bhakta NR, et al. ERS/ATS technical statement: standardisation of the measurement of lung volumes, 2023 update. Eur Respir J. 2023;62:2201519.
• Coates AL, et al. ERS technical standard on bronchial challenge testing: methacholine. Eur Respir J. 2017;49:1601526.
• Holland AE, et al. ERS/ATS technical standard: field walking tests in chronic respiratory disease. Eur Respir J. 2014;44:1428–1446.
• American Thoracic Society/European Respiratory Society. Statement on Respiratory Muscle Testing. Am J Respir Crit Care Med. 2002;166:518–624. Static mouth-pressure technique, p. 531.
• Stanojevic S, et al. ERS/ATS technical standard on interpretive strategies for routine lung function tests. Eur Respir J. 2022;60:2101499.
• European Respiratory Society. Spirometry interpretation, reference equations and fixed-ratio context.
• American Thoracic Society. Routine Lung Function Tests quick-reference guide, Figure 3, p. 6.
• Centers for Disease Control and Prevention. Clinical guidance for carbon monoxide poisoning, Confirmation of Diagnosis; August 21, 2026.
• Bhakta NR, et al. Race and Ethnicity in Pulmonary Function Test Interpretation: an official ATS statement. Am J Respir Crit Care Med. 2023;207(8).
• Davis MD, et al. AARC Clinical Practice Guideline: Blood Gas Analysis and Hemoximetry: 2013. Respir Care. 2013;58(10):1694.

By the Castleport Test Prep Editorial Team.

Castleport Test Prep is an independent exam prep publisher. We are not affiliated with, endorsed by, or approved by the National Board for Respiratory Care (NBRC). Exam and credential names, including CPFT and RPFT, identify their subjects; trademarks belong to their respective owners. The practice questions on this page are original and are not official NBRC exam questions.