Registered Pulmonary Function Technologist (RPFT) Practice Exam

Getting ready for the NBRC Registered Pulmonary Function Technologist (RPFT) exam takes more than just memorizing information. The test is designed to check whether you can actually interpret pulmonary function results, spot errors during testing, apply quality control standards, understand how the respiratory system works, and make solid clinical judgments in real situations. That’s why choosing the right study materials matters — they should help you not only learn the content but also walk into the exam feeling prepared and confident

Our RPFT Practice Exam includes 670 carefully developed practice questions with comprehensive answer explanations designed to closely reflect the style, difficulty, and clinical reasoning expected on the current RPFT examination. Every question reinforces essential concepts while helping you identify weak areas, improve critical thinking, and become familiar with the format of the certification exam.

Whether you are taking the RPFT exam for the first time or preparing for a retake, this complete practice package provides extensive coverage of the topics tested by the National Board for Respiratory Care (NBRC).

Why Choose Our RPFT Practice Exam?

Master the knowledge and clinical judgment required to pass the RPFT certification exam with confidence.

You’ll receive:

• 670 realistic RPFT practice questions
• Detailed explanations for every answer
• Exam-style multiple-choice questions
• Case-based clinical scenarios
• Current pulmonary function laboratory concepts
• Updated respiratory physiology questions
• Spirometry interpretation exercises
• Lung volume calculation practice
• DLCO interpretation questions
• Body plethysmography scenarios
• Cardiopulmonary exercise testing (CPET) practice
• Respiratory muscle testing questions
• Bronchodilator responsiveness interpretation
• Equipment calibration and quality assurance review
• Biological control and laboratory quality management
• Patient preparation and testing procedures
• Infection prevention and laboratory safety
• Professional ethics and documentation
• Unlimited self-paced study
• Instant digital access after purchase

Studying with realistic exam-style questions helps reinforce key concepts while building the confidence needed for certification success. Each explanation goes beyond the correct answer by explaining why the other options are incorrect, making every practice session a valuable learning experience.

What’s Included in This RPFT Study Package?

Prepare smarter with a complete review of the knowledge areas commonly evaluated on the Registered Pulmonary Function Technologist examination.

Major study areas include:

• Pulmonary anatomy and respiratory physiology
• Normal pulmonary function values
• Spirometry performance and interpretation
• Flow-volume loops
• Lung volumes and capacities
• Body plethysmography
• Gas dilution techniques
• Diffusing capacity (DLCO)
• Bronchodilator response testing
• Airway resistance measurements
• Respiratory muscle strength testing
• Cardiopulmonary exercise testing (CPET)
• Obstructive lung diseases
• Restrictive lung diseases
• Interstitial lung disease
• COPD assessment
• Asthma evaluation
• Neuromuscular disorders
• Pulmonary vascular disease
• Quality assurance programs
• Equipment calibration
• Biological control procedures
• Infection control standards
• Laboratory troubleshooting
• Patient coaching techniques
• Test acceptability and reproducibility
• ATS/ERS pulmonary function testing principles
• Clinical data interpretation
• Professional responsibilities of the RPFT

Every topic is presented through practical exam-style questions that encourage critical thinking rather than simple memorization.

Practice Questions That Reflect the Real RPFT Exam

Passing the RPFT exam requires understanding how pulmonary function data are applied in clinical practice.

Our practice questions are designed to help you:

• Interpret complex pulmonary function reports
• Analyze spirometry and flow-volume loops
• Identify common testing errors
• Evaluate restrictive and obstructive patterns
• Understand diffusion abnormalities
• Recognize equipment performance problems
• Apply quality control principles
• Interpret serial pulmonary function studies
• Evaluate bronchodilator responsiveness
• Strengthen clinical decision-making skills
• Improve testing accuracy
• Build confidence before exam day

Each explanation reinforces the underlying physiology and testing principles so you understand why an answer is correct—not just which option to select.

Built for First-Time Test Takers and Retake Candidates

Whether you’re preparing for your first certification attempt or improving your score after a previous exam, this practice exam is designed to strengthen your understanding of the complete RPFT blueprint.

Ideal for:

• Respiratory Therapists
• Pulmonary Function Technologists
• Pulmonary Laboratory Staff
• Respiratory Care Students
• Hospital Pulmonary Diagnostic Teams
• Sleep Laboratory Professionals expanding into PFT
• Healthcare professionals preparing for RPFT certification
• Candidates seeking additional exam practice

Comprehensive practice builds familiarity with exam wording, improves confidence under testing conditions, and helps reduce uncertainty on exam day.

Learn More Than Memorization

High scores come from understanding pulmonary physiology—not simply remembering isolated facts.

Every explanation helps you:

• Understand the reasoning behind the correct answer
• Learn from common mistakes
• Connect physiology with clinical practice
• Improve interpretation skills
• Reinforce important testing guidelines
• Strengthen long-term retention
• Prepare for complex scenario-based questions
• Develop professional decision-making abilities

The detailed rationales transform every practice question into a valuable learning opportunity, making your study sessions more productive and efficient.

Study at Your Own Pace

Flexible preparation allows you to focus on your weakest topics while reviewing material whenever it fits your schedule.

Benefits include:

• Immediate digital download
• Study anytime, anywhere
• Compatible with computers, tablets, and smartphones
• Unlimited review sessions
• Practice by topic or complete full-length review
• Excellent for independent study
• Helpful for classroom review
• Convenient for busy healthcare professionals

Consistent practice with realistic questions helps reinforce knowledge and improve confidence before your certification exam.

Why Trust Our Practice Exam?

We creates professionally written certification practice materials designed to help learners prepare efficiently for challenging professional examinations.

Our preparation materials focus on:

• Realistic exam-style questions
• Clear and accurate explanations
• Comprehensive topic coverage
• Practical clinical application
• Updated healthcare concepts
• Easy-to-follow study format
• High-quality educational content
• Confidence-building preparation

Every practice exam is developed to provide an engaging learning experience that supports both knowledge retention and exam readiness.

Start Preparing for the RPFT Certification Exam Today

Invest in a complete RPFT practice resource that combines realistic exam questions, detailed explanations, and comprehensive topic coverage in one convenient study package.

With 670 professionally written practice questions and detailed answer explanations, you’ll strengthen your understanding of pulmonary function testing, improve your clinical reasoning skills, identify knowledge gaps, and approach the NBRC Registered Pulmonary Function Technologist certification exam with greater confidence.

Prepare smarter, practice consistently, and take the next step toward earning your Registered Pulmonary Function Technologist (RPFT) credential with PrepPool.

RPFT Sample Questions and Answers

1. A 58-year-old man with progressive exertional dyspnea is referred for pulmonary function testing. His spirometry shows an FEV₁/FVC ratio of 0.61, while lung volume testing reveals a total lung capacity (TLC) above the upper limit of normal and an elevated residual volume (RV). Which interpretation best fits these findings?

A. Restrictive lung disease with reduced lung compliance
B. Obstructive lung disease with hyperinflation and air trapping
C. Normal pulmonary function for age
D. Mixed obstructive-restrictive disease with reduced TLC

Correct Answer: B

Explanation:

This combination of findings is classic for obstructive lung disease. A reduced FEV₁/FVC ratio confirms airflow obstruction, while increased TLC indicates hyperinflation. An elevated RV reflects air trapping caused by incomplete emptying of the lungs during exhalation. These findings are commonly seen in COPD, particularly emphysema, although severe asthma may produce similar results. Restrictive diseases reduce TLC rather than increase it. A mixed defect requires evidence of obstruction together with a reduced TLC. RPFTs must evaluate spirometry and lung volumes together because relying on spirometry alone may underestimate the degree of hyperinflation and fail to distinguish between simple obstruction and mixed ventilatory defects.

2. During body plethysmography, a patient repeatedly pants too rapidly despite coaching. How is this most likely to affect the measurement of thoracic gas volume?

A. It improves measurement accuracy
B. It may produce inaccurate lung volume measurements
C. It only affects diffusion capacity testing
D. It causes falsely low FEV₁ values

Correct Answer: B

Explanation:

Body plethysmography depends on slow, gentle panting near functional residual capacity. Excessively rapid panting disrupts pressure equilibration between the alveoli and mouth, producing inaccurate calculations of thoracic gas volume. The result may be either overestimation or underestimation depending on the patient’s effort and airway characteristics. Proper patient instruction is essential before testing begins, and repeated coaching should be provided if the maneuver is performed incorrectly. The error primarily affects lung volume measurements rather than spirometry or diffusion capacity. RPFTs should recognize poor technique immediately and repeat the maneuver instead of accepting questionable data that could influence clinical decisions.

3. A patient has the following post-bronchodilator spirometry results: FEV₁ increases by 16% and 280 mL compared with baseline. Which conclusion is most appropriate?

A. There is no significant bronchodilator response.
B. The patient demonstrates a significant bronchodilator response.
C. The patient has restrictive lung disease.
D. The spirometry should automatically be classified as normal.

Correct Answer: B

Explanation:

A meaningful bronchodilator response is demonstrated when post-bronchodilator values exceed accepted thresholds for significant improvement. An increase of 16% and 280 mL clearly indicates improved airflow after bronchodilator administration. Although a positive response supports reversible airflow limitation, it does not by itself establish a diagnosis of asthma or exclude COPD, since some patients with COPD also respond. RPFTs should compare pre- and post-bronchodilator measurements carefully and ensure both tests meet quality standards. The response should always be interpreted alongside symptoms, history, physical examination, and other pulmonary function results rather than in isolation.

4. A patient with known interstitial lung disease undergoes pulmonary function testing. Which pattern is most consistent with disease progression?

A. Increased TLC and increased RV
B. Reduced TLC with preserved or elevated FEV₁/FVC ratio
C. Increased FEV₁/FVC ratio with increased RV
D. Reduced RV with increased TLC

Correct Answer: B

Explanation:

Interstitial lung disease typically produces a restrictive ventilatory defect characterized by reduced lung volumes. As fibrosis progresses, TLC decreases because stiff lungs cannot expand normally. FEV₁ and FVC are both reduced, but because they decrease proportionally, the FEV₁/FVC ratio often remains normal or becomes slightly elevated. Increased TLC suggests hyperinflation rather than restriction. RPFTs should integrate spirometry, lung volume testing, and diffusion studies because restrictive disease frequently presents with reduced diffusion capacity as well. Monitoring serial pulmonary function results helps clinicians assess disease progression and determine whether treatment is slowing functional decline.

5. While performing spirometry, the patient coughs forcefully during the first second of expiration. What is the best action?

A. Accept the maneuver if FVC appears normal.
B. Report only the FEV₁ value.
C. Repeat the maneuver after additional coaching.
D. Average the results with previous attempts.

Correct Answer: C

Explanation:

A cough occurring during the first second of forced expiration invalidates measurement of FEV₁ because airflow is interrupted during the period when the value is being measured. Accepting the maneuver may underestimate airflow and lead to incorrect interpretation. The patient should receive additional instruction, be allowed adequate rest if needed, and repeat the maneuver until acceptable criteria are achieved. RPFTs play a critical role in identifying unacceptable efforts and recognizing artifacts before reporting results. High-quality testing depends as much on proper coaching and quality control as on equipment performance.

6. A patient has a markedly reduced DLCO with normal spirometry and normal lung volumes. Which condition should be strongly considered?

A. Pulmonary vascular disease
B. Upper airway obstruction
C. Neuromuscular weakness
D. Obesity-related restriction

Correct Answer: A

Explanation:

A significantly reduced diffusion capacity despite otherwise normal pulmonary function suggests impaired gas exchange at the alveolar-capillary membrane or reduced pulmonary capillary blood volume. Pulmonary vascular diseases, including pulmonary hypertension, commonly produce this isolated abnormality. Early emphysema may also reduce DLCO before spirometry becomes abnormal, but pulmonary vascular disease is an important consideration. Neuromuscular disorders generally reduce lung volumes rather than diffusion capacity alone. RPFTs should ensure correction for hemoglobin when appropriate because anemia can falsely lower measured DLCO and potentially mimic underlying disease.

7. During calibration verification, the 3-liter syringe repeatedly measures 2.82 liters. What should the technologist do before testing patients?

A. Proceed because the difference is clinically insignificant.
B. Recalibrate or troubleshoot the spirometer before patient testing.
C. Document the error and continue testing.
D. Increase patient coaching to compensate.

Correct Answer: B

Explanation:

Routine calibration verification ensures spirometry equipment remains accurate throughout the testing day. A measured volume of 2.82 liters falls outside acceptable calibration limits, indicating that patient testing should not proceed until the problem is corrected. Possible causes include equipment malfunction, leaks, environmental input errors, or calibration drift. Troubleshooting protects patient safety and prevents invalid clinical decisions based on inaccurate measurements. RPFTs are responsible for documenting calibration checks, correcting equipment issues promptly, and confirming acceptable performance before collecting patient data.

8. A patient being evaluated before lung resection has a markedly reduced predicted postoperative FEV₁ and DLCO. Why are these findings clinically important?

A. They indicate increased perioperative pulmonary risk.
B. They eliminate the need for exercise testing.
C. They confirm asthma.
D. They indicate normal postoperative recovery.

Correct Answer: A

Explanation:

Preoperative pulmonary function testing estimates whether patients can tolerate surgical removal of lung tissue. Both predicted postoperative FEV₁ and DLCO are major predictors of pulmonary complications after lung resection. Significantly reduced values indicate higher risk for respiratory failure, prolonged ventilation, and postoperative disability. Additional testing, including exercise evaluation or cardiopulmonary exercise testing, may be recommended depending on institutional protocols. RPFTs contribute valuable physiologic information that helps surgeons and pulmonologists determine whether surgery is appropriate and identify patients who may benefit from preoperative optimization.

9. Which pulmonary function finding is most characteristic of emphysema?

A. Increased DLCO
B. Reduced DLCO due to alveolar destruction
C. Increased FEV₁/FVC ratio with normal TLC
D. Markedly reduced RV

Correct Answer: B

Explanation:

Emphysema destroys alveolar walls and pulmonary capillary beds, reducing the available surface area for gas exchange. As a result, diffusion capacity decreases, often substantially. Patients also commonly demonstrate airflow obstruction, hyperinflation, and increased residual volume. Chronic bronchitis may produce obstruction while maintaining relatively preserved DLCO if emphysema is absent. RPFTs should recognize that diffusion testing provides important information beyond spirometry by helping distinguish emphysema from other obstructive disorders and by assessing disease severity over time.

10. A patient cannot maintain an adequate inspiratory breath-hold during DLCO testing. What is the most appropriate response?

A. Report the result regardless of quality.
B. Repeat the maneuver after providing additional coaching.
C. Substitute spirometry values for DLCO.
D. Estimate diffusion capacity from oxygen saturation.

Correct Answer: B

Explanation:

Successful diffusion capacity testing requires a rapid inspiration followed by a stable breath-hold for the required interval. Failure to maintain the breath-hold invalidates the measurement because gas transfer cannot be accurately calculated. The technologist should carefully explain the maneuver again, demonstrate the sequence if necessary, and repeat the test until acceptable quality standards are achieved. Reporting poor-quality results risks misleading the interpreting physician. RPFTs should always evaluate test acceptability before assessing reproducibility and should document any patient limitations affecting performance.

11. A flow-volume loop demonstrates flattening of both the inspiratory and expiratory limbs. Which condition is most likely?

A. Variable extrathoracic obstruction
B. Variable intrathoracic obstruction
C. Fixed upper airway obstruction
D. Mild restrictive lung disease

Correct Answer: C

Explanation:

Flattening of both inspiratory and expiratory portions of the flow-volume loop suggests a fixed obstruction affecting airflow throughout the respiratory cycle. Examples include tracheal stenosis, fixed tracheal tumors, or severe scarring. Variable extrathoracic obstruction primarily affects inspiration, whereas variable intrathoracic obstruction mainly affects expiration. RPFTs should recognize abnormal loop morphology because upper airway obstruction may not be obvious from spirometric values alone. Careful visual inspection of the flow-volume loop remains an essential component of pulmonary function interpretation.

12. A patient with severe obesity has reduced FVC but a normal FEV₁/FVC ratio. What should be performed to confirm whether true restriction is present?

A. Peak flow measurement only
B. Lung volume measurement
C. Arterial blood gas only
D. Pulse oximetry during exercise

Correct Answer: B

Explanation:

Spirometry alone cannot confirm restrictive lung disease because a reduced FVC may result from poor effort, obesity, air trapping, or true restriction. Measuring TLC is necessary to determine whether restriction actually exists. If TLC is reduced, restriction is confirmed. If TLC is normal or elevated, another explanation should be considered. RPFTs should avoid diagnosing restriction from spirometry alone and should recommend complete pulmonary function testing whenever the diagnosis remains uncertain after initial evaluation.

13. During spirometry, the patient stops exhaling after four seconds despite an obvious plateau not yet being reached. What is the best interpretation?

A. The maneuver is acceptable.
B. FVC may be underestimated because expiration ended too early.
C. Only peak flow is affected.
D. The maneuver confirms restrictive disease.

Correct Answer: B

Explanation:

Premature termination of forced expiration commonly underestimates FVC because the patient fails to exhale the remaining air from the lungs. This may falsely increase the FEV₁/FVC ratio and potentially mask airflow obstruction. RPFTs should encourage continued exhalation until no further volume is expelled or quality criteria are satisfied. Careful coaching, motivation, and observation are essential for obtaining valid spirometry. Accepting incomplete efforts can lead to incorrect diagnoses and inappropriate treatment recommendations.

14. Which quality assurance practice most directly supports reliable pulmonary function testing across multiple testing days?

A. Using identical mouthpieces for every patient indefinitely
B. Performing routine equipment calibration verification and documenting results
C. Testing only healthy volunteers each morning
D. Limiting testing to one technologist

Correct Answer: B

Explanation:

Quality assurance is a cornerstone of pulmonary function laboratories. Daily calibration verification, biological controls when appropriate, preventive maintenance, and complete documentation ensure equipment continues to produce accurate and reproducible measurements. Consistent quality control allows clinicians to compare patient results over time with confidence. RPFTs are responsible for identifying equipment problems early, documenting corrective actions, and ensuring laboratory procedures comply with current professional standards. Reliable testing begins before the patient enters the laboratory.

15. A patient with neuromuscular disease demonstrates reduced TLC, reduced vital capacity, and normal DLCO when corrected for alveolar volume. What is the most likely explanation?

A. Primary emphysema
B. Respiratory muscle weakness causing restrictive physiology
C. Severe asthma with hyperinflation
D. Pulmonary embolism

Correct Answer: B

Explanation:

Neuromuscular disorders reduce the ability of respiratory muscles to expand the lungs fully, producing a restrictive pattern with decreased lung volumes. Because the alveolar-capillary membrane itself remains intact, diffusion capacity corrected for alveolar volume may remain relatively preserved. This differs from interstitial lung disease, where membrane damage reduces gas transfer. RPFTs should recognize the importance of maximal inspiratory and expiratory pressure testing when respiratory muscle weakness is suspected, as these measurements provide additional functional information beyond routine spirometry.

16. Which patient should NOT undergo spirometry until further medical evaluation because of a potential contraindication?

A. A patient with controlled hypertension
B. A patient who experienced a recent myocardial infarction and remains unstable
C. A patient with seasonal allergies
D. A patient with stable chronic bronchitis

Correct Answer: B

Explanation:

Forced expiratory maneuvers substantially increase intrathoracic, intra-abdominal, and intracranial pressures. Patients with unstable cardiovascular conditions, including a recent myocardial infarction or unstable angina, may face increased risk during testing. The benefits and risks should be carefully assessed before proceeding. Stable chronic lung disease or controlled hypertension alone generally does not prevent testing. RPFTs should review the patient’s history for contraindications before beginning pulmonary function studies and consult the supervising physician whenever uncertainty exists.

17. A patient undergoing methacholine challenge experiences a significant fall in FEV₁ after a low concentration of methacholine. What does this finding suggest?

A. Decreased airway responsiveness
B. Airway hyperresponsiveness consistent with asthma physiology
C. Normal pulmonary function
D. Restrictive lung disease

Correct Answer: B

Explanation:

Methacholine challenge testing evaluates airway hyperresponsiveness by exposing the airways to progressively increasing concentrations of methacholine. A significant decline in FEV₁ at a relatively low dose indicates increased airway sensitivity, which supports asthma physiology when interpreted alongside the clinical history. The test is not diagnostic by itself because other conditions may occasionally produce increased responsiveness. RPFTs must monitor patients closely throughout the procedure, recognize when stopping criteria are reached, and administer bronchodilator therapy promptly after testing is complete.

18. During pulmonary function testing, repeated spirometry efforts vary widely despite acceptable technique. Which factor should the technologist investigate first?

A. Patient understanding and maximal effort
B. Laboratory lighting conditions
C. Printer settings
D. Age of the spirometry software

Correct Answer: A

Explanation:

Large variation between repeated spirometry efforts most commonly reflects inconsistent patient effort or misunderstanding of instructions. Before suspecting equipment malfunction, the technologist should verify that the patient understands the maneuver, provide additional demonstrations, encourage maximal effort, and ensure an adequate seal around the mouthpiece. Good coaching often improves reproducibility dramatically. RPFTs must balance patient encouragement with careful observation to identify fatigue, discomfort, or technique errors that reduce test reliability.

19. A patient with chronic dyspnea has normal spirometry but markedly reduced maximal inspiratory pressure (MIP). Which condition is most strongly suggested?

A. Respiratory muscle weakness
B. Hyperinflation from emphysema
C. Upper airway obstruction
D. Mild pulmonary fibrosis

Correct Answer: A

Explanation:

Maximal inspiratory pressure measures inspiratory muscle strength, particularly diaphragmatic function. A markedly reduced MIP despite normal spirometry suggests respiratory muscle weakness rather than primary airway or parenchymal lung disease. Causes include neuromuscular disorders, diaphragmatic dysfunction, and generalized muscle weakness. RPFTs should ensure proper patient coaching because maximal pressure testing requires strong voluntary effort. Reproducible measurements improve diagnostic confidence and help monitor progression or response to therapy in neuromuscular conditions.

20. A patient being followed for idiopathic pulmonary fibrosis has serial pulmonary function tests performed every six months. Which change most strongly suggests disease progression?

A. Increasing TLC and increasing DLCO
B. Stable FVC with improved diffusion capacity
C. Progressive decline in FVC and DLCO over serial testing
D. Increasing residual volume with normal TLC

Correct Answer: C

Explanation:

Serial pulmonary function testing is essential for monitoring progressive interstitial lung diseases. Declining FVC reflects worsening restrictive physiology, while decreasing DLCO indicates deterioration in gas exchange across the alveolar-capillary membrane. Together, these changes provide objective evidence of disease progression and may influence treatment decisions, transplant evaluation, or prognosis. Single test results are valuable, but trends over time are often more clinically meaningful than isolated measurements. RPFTs should ensure testing is performed consistently using standardized procedures so serial comparisons accurately reflect physiologic change rather than testing variability.

21. A 64-year-old former smoker performs spirometry. His FEV₁ and FVC are reduced, the FEV₁/FVC ratio is below the lower limit of normal, and TLC is also below normal. Which interpretation is most accurate?

A. Pure obstructive ventilatory defect
B. Pure restrictive ventilatory defect
C. Mixed obstructive and restrictive ventilatory defect
D. Normal aging pattern

Correct Answer: C

Explanation:

A mixed ventilatory defect is diagnosed when airflow obstruction is present together with confirmed restriction. In this patient, the reduced FEV₁/FVC ratio demonstrates obstruction, while the decreased total lung capacity confirms restriction. Spirometry alone cannot diagnose a mixed disorder because a reduced FVC may simply reflect air trapping. Lung volume measurement is required to establish true restriction. Mixed patterns occur in patients with COPD and pulmonary fibrosis, sarcoidosis with airway disease, bronchiectasis with fibrosis, or other combinations of airway and parenchymal disorders. RPFT candidates should remember that TLC is the deciding factor when distinguishing pseudo-restriction caused by air trapping from genuine restrictive lung disease. Proper interpretation requires reviewing all pulmonary function measurements together rather than relying on a single parameter.

22. During DLCO testing, the patient inspires only 75% of vital capacity before the breath-hold. What is the most likely consequence?

A. DLCO may be falsely reduced.

B. DLCO will always be falsely elevated.

C. Spirometry values become invalid.

D. Residual volume cannot be calculated.

Correct Answer: A

Explanation:

Diffusing capacity testing depends on adequate inflation of the lungs so that the maximum alveolar surface area is available for gas exchange. If the inspired volume is substantially below the recommended level, fewer alveoli participate in carbon monoxide transfer, leading to an artificially reduced DLCO. This does not necessarily indicate impaired gas exchange but rather poor test quality. The RPFT should coach the patient to inhale rapidly and completely before beginning the breath-hold. Acceptable inspiratory volume is essential for valid interpretation. Test quality indicators should always be reviewed before reporting diffusion results because technical errors frequently mimic disease.

23. A patient repeatedly leaks air around the mouthpiece during spirometry. What is the most likely effect on the measured FVC?

A. FVC becomes falsely elevated.

B. FVC becomes falsely reduced.

C. FVC remains unchanged.

D. Only peak expiratory flow is affected.

Correct Answer: B

Explanation:

An air leak allows exhaled air to escape before reaching the spirometer, resulting in underestimation of exhaled volume. Consequently, the measured FVC becomes falsely low. Depending on the timing of the leak, FEV₁ may also be underestimated. The RPFT should stop the maneuver immediately, reposition the mouthpiece, ensure the patient’s lips completely seal around it, and repeat the test. Dentures should usually remain in place if they improve the seal. Careful observation throughout testing helps identify leaks before invalid data are accepted. Maintaining proper technique is one of the most important responsibilities of the pulmonary function technologist.

24. Which disease most commonly produces a normal DLCO despite chronic airflow obstruction?

A. Emphysema

B. Chronic bronchitis

C. Idiopathic pulmonary fibrosis

D. Pulmonary arterial hypertension

Correct Answer: B

Explanation:

Patients with chronic bronchitis often have airflow obstruction without significant destruction of the alveolar-capillary membrane. Because the gas exchange surface remains relatively intact, DLCO may remain within the normal range. In contrast, emphysema destroys alveolar walls and pulmonary capillaries, resulting in reduced diffusion capacity. Interstitial lung disease and pulmonary vascular disease also decrease DLCO through different mechanisms. Understanding these differences allows RPFTs to distinguish obstructive diseases with similar spirometric findings. Combining spirometry and diffusion testing substantially improves diagnostic accuracy and assists physicians in identifying the predominant underlying pathology.

25. A patient’s flow-volume loop demonstrates a normal expiratory limb but marked flattening during inspiration. Which condition is most likely?

A. Variable extrathoracic airway obstruction

B. Variable intrathoracic airway obstruction

C. Severe emphysema

D. Pulmonary fibrosis

Correct Answer: A

Explanation:

Variable extrathoracic airway obstruction primarily limits inspiratory airflow because negative inspiratory pressure narrows the upper airway. Conditions such as vocal cord dysfunction or upper airway soft tissue collapse commonly produce this characteristic loop pattern. Variable intrathoracic obstruction mainly affects expiration, while fixed airway obstruction flattens both inspiratory and expiratory limbs. RPFTs should inspect flow-volume loops visually rather than relying solely on numeric values because upper airway abnormalities are often recognized first through loop morphology. Identifying these patterns can prevent delayed diagnosis of potentially serious airway disorders.