Notes · Respiratory · 7 min read
Spirometry and lung function
Obstructive, restrictive or mixed — and what the transfer factor adds.
Key points
- Obstruction: FEV1/FVC below 0.7 (or below the lower limit of normal).
- Restriction: reduced FVC with a normal or high FEV1/FVC; confirm with reduced total lung capacity.
- A rise in FEV1 of 12% and 200 mL after a bronchodilator supports asthma.
- Low gas transfer (DLCO) with obstruction suggests emphysema.
- Low DLCO with restriction suggests interstitial lung disease; normal DLCO suggests a chest wall or neuromuscular cause.
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