Which lung capacity is primarily affected in restrictive lung disease?

In restrictive lung disease, the primary issue is a reduction in lung volume due to the stiffening of lung tissue or the thoracic cavity, which limits the ability of the lungs to expand fully. Total lung capacity (TLC) reflects the maximum amount of air the lungs can hold, and in restrictive lung disease, this capacity is typically decreased.

The decreased TLC directly relates to the restrictive nature of the disease, wherein less air can be inhaled due to the reduced compliance of the lungs or the chest wall. As a consequence, the patient may experience difficulty filling the lungs completely during inhalation, leading to lower total lung capacity measurements.

The other lung volumes and capacities, such as functional residual capacity, residual volume, and vital capacity, may also be affected in restrictive diseases, but the hallmark characteristic of restrictive lung pathology is indeed the decrease in total lung capacity. This helps differentiate it from obstructive lung diseases, where total lung capacity might be normal or increased.