On a flow-volume loop obtained during forced spirometry, peak expiratory flow is reduced and the expiratory limb shows a scooped or concave pattern toward the volume axis. The FEV1/FVC ratio is 0.58. What pattern does this represent and which condition is most consistent?
- A Restrictive pattern; consistent with pulmonary fibrosis
- B Mixed pattern; consistent with sarcoidosis
- C Obstructive pattern; consistent with emphysema or severe COPD ✓
- D Fixed upper airway obstruction; consistent with tracheal stenosis
Correct answer: C. Obstructive pattern; consistent with emphysema or severe COPD
Explanation
An FEV1/FVC ratio below 0.70 defines obstruction. The concave (scooped) expiratory limb reflects effort-independent flow limitation at lower lung volumes, characteristic of small airway collapse in emphysema and COPD. In restriction, TLC and FVC are reduced but the ratio is preserved or elevated; the loop is narrow but not scooped. Fixed upper airway obstruction produces a plateau on both inspiratory and expiratory limbs.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
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