Decreased FRC is most consistent with which pulmonary disease?

Decreased FRC is most consistent with which pulmonary disease?

• A. Emphysema
• B. Chronic bronchitis
• C. Restrictive pulmonary disease
• D. Pulmonary emphysema and chronic bronchitis

Answer: (C)

Functional residual capacity (FRC) is the volume in the lungs after a normal exhalation, reflecting the balance between the lungs’ inward elastic recoil and the chest wall’s outward recoil. In obstructive diseases like emphysema and chronic bronchitis, air trapping and hyperinflation tend to enlarge the lungs, so FRC is increased. In restrictive pulmonary disease, the lungs and/or chest wall are less able to expand, reducing overall lung volumes, including FRC. Therefore a decreased FRC fits restrictive disease best. The other conditions involve obstruction with air trapping, which typically raises FRC rather than lowers it.

Functional residual capacity (FRC) is the volume in the lungs after a normal exhalation, reflecting the balance between the lungs’ inward elastic recoil and the chest wall’s outward recoil. In obstructive diseases like emphysema and chronic bronchitis, air trapping and hyperinflation tend to enlarge the lungs, so FRC is increased. In restrictive pulmonary disease, the lungs and/or chest wall are less able to expand, reducing overall lung volumes, including FRC. Therefore a decreased FRC fits restrictive disease best. The other conditions involve obstruction with air trapping, which typically raises FRC rather than lowers it.