Interpret · PFTs
Flow-volume loop lab
Numbers can be normal while the loop carries the diagnosis. Learn the six silhouettes and what feature gives each away.
Normal
What gives it away: Fast rise to peak, straight descent, rounded inspiratory limb.
Try the case →Obstructive
What gives it away: The scooped, concave expiratory descent: flows collapse at low lung volumes.
Try the case →Restrictive
What gives it away: A miniature but normally-shaped loop shifted toward smaller volumes.
Try the case →Variable extrathoracic
What gives it away: Flattened inspiratory limb: the upper airway collapses inward on inspiration.
Try the case →Fixed obstruction
What gives it away: Both limbs capped: the loop becomes a box.
Try the case →Mixed
What gives it away: Small volumes AND a scooped descent: two problems at once.