NBRC Pulmonary Function Testing 2 — Questions and Answers
Question 1: The flow-volume loop in a patient with a fixed upper airway obstruction shows:
- Normal inspiratory and expiratory curves
- Flattening of both the inspiratory and expiratory limbs (Correct answer)
- Flattening of the inspiratory limb only
- Flattening of the expiratory limb only
Correct answer: Flattening of both the inspiratory and expiratory limbs
Fixed upper airway obstructions (such as tracheal stenosis) truncate both inspiratory and expiratory flows equally, producing a flattened box-like loop.
Question 2: A variable extrathoracic obstruction (e.g., vocal cord dysfunction during inspiration) flattens which portion of the flow-volume loop?
- Expiratory limb
- Inspiratory limb (Correct answer)
- Both limbs equally
- Peak expiratory flow
Correct answer: Inspiratory limb
Variable extrathoracic obstructions worsen during inspiration because negative pressure draws the obstruction into the airway, flattening the inspiratory limb.
Question 3: The maximum voluntary ventilation (MVV) test measures:
- Resting tidal volume over one minute
- The maximum volume breathed in and out over 12–15 seconds, extrapolated to one minute (Correct answer)
- Forced vital capacity repeated three times
- Inspiratory capacity during maximal effort
Correct answer: The maximum volume breathed in and out over 12–15 seconds, extrapolated to one minute
MVV assesses the maximum minute ventilation achievable with maximal effort, reflecting overall ventilatory capacity including respiratory muscle strength and airway patency.
Question 4: Which PFT finding is most consistent with pulmonary fibrosis?
- Increased TLC, increased RV, reduced FEV1/FVC
- Reduced TLC, reduced FVC, normal or elevated FEV1/FVC, reduced DLCO (Correct answer)
- Normal TLC, reduced FEV1/FVC, increased RV
- Increased DLCO, normal TLC, reduced FVC
Correct answer: Reduced TLC, reduced FVC, normal or elevated FEV1/FVC, reduced DLCO
Pulmonary fibrosis causes restrictive physiology with reduced TLC and FVC, elevated FEV1/FVC ratio, and reduced DLCO due to loss of alveolar-capillary surface.
Question 5: Nitrogen washout and helium dilution are techniques used to measure:
- Airway resistance
- Functional residual capacity (FRC) (Correct answer)
- Peak expiratory flow rate
- Oxygen consumption
Correct answer: Functional residual capacity (FRC)
Both nitrogen washout and helium dilution techniques measure FRC by using inert tracer gases to calculate the volume of gas in communication with the open airways.
Question 6: Acceptable spirometry requires that the technician ensure the patient performs a maneuver that is:
- Of any duration as long as effort is present
- Repeatable within 150 mL for the two best FVC and FEV1 values (Correct answer)
- Performed seated or standing only
- Completed in under 3 seconds
Correct answer: Repeatable within 150 mL for the two best FVC and FEV1 values
ATS/ERS acceptability criteria require reproducibility of the best two FVC and FEV1 values within 150 mL to ensure test reliability.
NBRC Pulmonary Function Testing 2
The flow-volume loop in a patient with a fixed upper airway obstruction shows: