RRT RRT Pulmonary Function Testing 2 — Questions and Answers
Question 1: Which flow-volume loop pattern is characteristic of a fixed upper airway obstruction?
- Normal scooped appearance on expiration
- Flattening of both inspiratory and expiratory limbs (Correct answer)
- Flattening of the inspiratory limb only
- Flattening of the expiratory limb only
Correct answer: Flattening of both inspiratory and expiratory limbs
Fixed upper airway obstruction (e.g., tracheal stenosis) produces plateauing (flattening) of both the inspiratory and expiratory limbs of the flow-volume loop.
Question 2: What does the term 'air trapping' refer to in pulmonary function testing?
- Elevated TLC with normal RV
- Elevated RV and RV/TLC ratio indicating incomplete exhalation (Correct answer)
- Reduced FVC with normal FEV1
- Elevated DLCO
Correct answer: Elevated RV and RV/TLC ratio indicating incomplete exhalation
Air trapping is diagnosed by an elevated RV and increased RV/TLC ratio (>35%), reflecting incomplete emptying of alveoli in obstructive diseases.
Question 3: Which pulmonary function test measurement best reflects small airway function?
- FEV1
- FVC
- FEF 25–75% (Correct answer)
- Peak expiratory flow
Correct answer: FEF 25–75%
FEF 25–75% (forced expiratory flow between 25% and 75% of FVC) reflects small to medium airway function and may show obstruction before FEV1 changes.
Question 4: In body plethysmography, what does functional residual capacity (FRC) represent?
- Volume of air remaining after maximal expiration
- Volume of air in the lungs at the end of a normal expiration (Correct answer)
- Volume of air inhaled above tidal volume
- Maximum volume during a forced inspiration
Correct answer: Volume of air in the lungs at the end of a normal expiration
FRC is the equilibrium volume of the lungs after passive expiration, where elastic recoil of the lungs balances outward chest wall recoil.
Question 5: A patient with pulmonary fibrosis would most likely show which spirometry result?
- FEV1/FVC ratio <0.70 with normal FVC
- Reduced FVC, reduced FEV1, normal or elevated FEV1/FVC ratio (Correct answer)
- Normal FVC with markedly reduced FEV1
- Elevated TLC with air trapping
Correct answer: Reduced FVC, reduced FEV1, normal or elevated FEV1/FVC ratio
Pulmonary fibrosis causes a restrictive pattern with reduced FVC and FEV1, but FEV1/FVC is preserved or increased because fibrosis stiffens the lung aiding forced expiration.
Question 6: What is the purpose of performing the nitrogen washout test?
- Measure diffusing capacity
- Measure lung volumes including FRC when a body box is unavailable (Correct answer)
- Assess bronchodilator responsiveness
- Evaluate respiratory muscle strength
Correct answer: Measure lung volumes including FRC when a body box is unavailable
The nitrogen washout test measures FRC by diluting resident nitrogen with 100% oxygen, calculating the original volume from the exhaled nitrogen concentration.
RRT RRT Pulmonary Function Testing 2
Which flow-volume loop pattern is characteristic of a fixed upper airway obstruction?