Question

Compliance is decreased in all except:

• A. Pulmonary congestion
• B. COPD
• C. Decreased surfactant
• D. Pulmonary fibrosis

Hint:

Loss of elastic recoil in emphysema makes the lung easier, not harder, to inflate.

Answer 1

The Correct Option is B

Compliance tells us how readily the lung stretches for a given pressure, so conditions that stiffen the lung drop compliance, while conditions that destroy elastic tissue raise it. Working through the options, pulmonary congestion soaks the lung with fluid, and a waterlogged lung resists expansion, so its compliance falls. A shortage of surfactant lets surface tension climb, pulling alveoli toward collapse and making the lung harder to inflate, again a reduction in compliance, the hallmark of neonatal and adult respiratory distress. Pulmonary fibrosis lays down dense scar and collagen, producing a rigid, restrictive lung with strikingly low compliance. The outlier is chronic obstructive pulmonary disease. In emphysema the alveolar walls and the elastic framework are broken down, so recoil is lost and the lung becomes flabby and over-distensible, which means compliance actually goes up. Since every other choice lowers compliance and COPD raises it, COPD is the exception.
\[\boxed{\text{COPD}}\]