In restrictive pulmonary diseases, which aspect is typically decreased?

• A. Airway resistance
• B. Functional volume
• C. Oxygen exchange
• D. Carbon dioxide elimination

Answer: (B)

In restrictive pulmonary diseases, such as pulmonary fibrosis or chest wall disorders, the primary characteristic is a decrease in lung volume. This means that the lungs cannot expand effectively during inhalation, leading to a reduction in the functional volume of the lungs, which refers to the volume of air that is effectively used during the breathing cycle.

Functional volume encompasses various measurements, including the tidal volume and the vital capacity, both of which would be reduced in a patient with a restrictive lung condition. The overall result is a decrease in the amount of air that can be taken in during a breath, which subsequently impacts ventilation efficiency and gas exchange.

While airway resistance, oxygen exchange, and carbon dioxide elimination may also be affected in restrictive diseases, they are not consistently decreased in the same manner as functional lung volume. Airway resistance may not change significantly because the issue is not primarily with the airways themselves but with the lung tissue and expansion capability. Oxygen exchange and carbon dioxide elimination can be compromised due to reduced lung volumes, but they do not directly reflect the hallmark feature of restrictive lung diseases, which is the diminished capacity of the lungs to hold air. Thus, the decrease in functional volume is the most accurate descriptor of what happens in these conditions.