Parameters:
(1) post-bronchodilator inspiratory capacity (IC) in liters
(2) total lung capacity (TLC)
(3) total lung capacity as percent of predicted
inspiratory fraction =
= (inspiratory capacity) / (total lung capacity)
Interpretation:
• minimum inspiratory fraction: around 0.1
• maximum inspiratory fraction: around 0.6.
• An inspiratory fraction <= 0.28 was associated with increased lung volumes and reduced exercise capacity.
• A total lung capacity > 120% of predicted was associated with lung hyperinflation.
Performance:
• The inspiratory fraction <= 28% had a sensitivity of 80% and specificity of 90% in predicting severely reduced maximum exercise capacity (peak VO2 < 60% of predicted).
• The area under the ROC curve is 0.92.
