CRE Pulmonary Function Testing & Interpretation 2 — Questions and Answers
Question 1: On a flow-volume loop, a concave (scooped-out) appearance of the expiratory limb is characteristic of which condition?
- Restrictive lung disease
- Fixed upper airway obstruction
- Obstructive lung disease (Correct answer)
- Normal lung function
Correct answer: Obstructive lung disease
Obstructive lung disease produces a concave expiratory limb on the flow-volume loop because airflow becomes progressively reduced as lung volumes decrease.
Question 2: A methacholine challenge (bronchoprovocation) test is primarily used to evaluate for which condition?
- COPD severity staging
- Bronchial hyperresponsiveness consistent with asthma (Correct answer)
- Pulmonary fibrosis progression
- Pulmonary vascular disease
Correct answer: Bronchial hyperresponsiveness consistent with asthma
Methacholine challenge testing measures bronchial hyperresponsiveness; a positive test (PC20 ≤8 mg/mL) supports a diagnosis of asthma.
Question 3: Maximum Voluntary Ventilation (MVV) measures which respiratory parameter?
- The maximum volume exhaled in 6 seconds
- The maximum volume breathed in and out over 12-15 seconds extrapolated to one minute (Correct answer)
- The peak expiratory flow rate during tidal breathing
- The static elastic recoil of the lung
Correct answer: The maximum volume breathed in and out over 12-15 seconds extrapolated to one minute
MVV is measured by having the patient breathe as rapidly and deeply as possible for 12-15 seconds; the result is extrapolated to L/min and reflects respiratory muscle endurance and airway function.
Question 4: Peak expiratory flow (PEF) monitoring is most commonly used to assess which chronic respiratory condition?
- Idiopathic pulmonary fibrosis
- Asthma (Correct answer)
- Emphysema
- Obstructive sleep apnea
Correct answer: Asthma
PEF monitoring is integral to asthma action plans, allowing patients to detect airflow changes and adjust therapy based on their personal best values.
Question 5: Body plethysmography is required to accurately measure which lung volume that cannot be measured by spirometry alone?
- FVC
- FEV1
- Functional Residual Capacity (FRC) (Correct answer)
- Inspiratory Reserve Volume (IRV)
Correct answer: Functional Residual Capacity (FRC)
Body plethysmography uses Boyle's Law to measure FRC (the volume of gas remaining in the lungs at the end of a normal exhalation), which includes residual volume not accessible to spirometry.
Question 6: The multiple-breath nitrogen washout test is used to measure which lung parameter?
- FEV1 percent predicted
- Functional Residual Capacity (FRC) (Correct answer)
- Diffusing capacity (DLCO)
- Maximum voluntary ventilation
Correct answer: Functional Residual Capacity (FRC)
The nitrogen washout technique measures FRC by having the patient breathe 100% oxygen until exhaled nitrogen concentration approaches zero, allowing calculation of the starting gas volume.
Question 7: When interpreting spirometry, percent predicted values are derived by comparing patient results to which reference standard?
- The patient's personal best effort from prior testing
- Age-, height-, sex-, and ethnicity-matched reference population data (Correct answer)
- A fixed hospital-specific normative database
- A universal standard independent of patient demographics
Correct answer: Age-, height-, sex-, and ethnicity-matched reference population data
Predicted values are calculated from regression equations derived from healthy nonsmoking reference populations, accounting for age, height, sex, and ethnicity.
CRE Pulmonary Function Testing & Interpretation 2
On a flow-volume loop, a concave (scooped-out) appearance of the expiratory limb is characteristic of which condition?