What flow-volume loop pattern is typically seen in obstructive disease?

What flow-volume loop pattern is typically seen in obstructive disease?

• A. Flat loop
• B. Skinny loop
• C. Normal loop
• D. Wonky shaped with rapid inhalation followed by a drop in volume

Answer: (D)

In obstructive disease, airways are narrowed during expiration, so expelling air becomes difficult and the expiratory flow is reduced. On a flow-volume loop this shows up as a loop where the inspiratory portion can look relatively normal, but the expiratory limb becomes concave or irregular, reflecting the slowed and resisted exhalation. Descriptions of a “wonky” shaped loop with rapid inhalation followed by a drop in volume capture this difficulty with expiration—air moves in quickly but air leaving the lungs trails off prematurely as airway resistance and collapse blunt expiratory flow, producing a noticeable dip in volume. This contrasts with a flat loop (fixed obstruction), a skinny loop (restrictive pattern with reduced volumes but normal shape), or a normal loop (no obstruction).

In obstructive disease, airways are narrowed during expiration, so expelling air becomes difficult and the expiratory flow is reduced. On a flow-volume loop this shows up as a loop where the inspiratory portion can look relatively normal, but the expiratory limb becomes concave or irregular, reflecting the slowed and resisted exhalation. Descriptions of a “wonky” shaped loop with rapid inhalation followed by a drop in volume capture this difficulty with expiration—air moves in quickly but air leaving the lungs trails off prematurely as airway resistance and collapse blunt expiratory flow, producing a noticeable dip in volume. This contrasts with a flat loop (fixed obstruction), a skinny loop (restrictive pattern with reduced volumes but normal shape), or a normal loop (no obstruction).