Effect of common lung conditions on DLCO, VA, and DLCO/VA (KCO)

Condition	VA	DLCO/VA (KCO)	DLCO
Incomplete lung expansion (eg, neuromuscular weakness or inadequate inspiration)	↓↓↓	↑↑	↓
Discrete loss of alveolar units (eg, pneumonectomy)	↓↓↓	↑	↓↓
Diffuse loss of alveolar units (eg, interstitial lung disease)	↓↓	↓	↓↓↓
Emphysema	Normal to ↓	↓↓	↓↓↓
Pulmonary vascular disease	Normal	↓↓	↓↓
High pulmonary blood volume (eg, heart failure)	Normal	↑	↑
Alveolar hemorrhage	↓	↑↑↑	↑↑

DLCO: diffusing capacity for carbon monoxide; VA: alveolar volume measured during single breath DLCO; KCO: carbon monoxide transfer coefficient.

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