What distinguishes restrictive lung diseases from obstructive lung diseases?

Restrictive lung diseases are primarily characterized by reduced lung volume, which signifies that the lungs are unable to fully expand. This reduction in lung volume can arise from various factors, including loss of lung tissue (e.g., pulmonary fibrosis), chest wall deformities, or neuromuscular diseases that affect respiratory muscles. As a result, patients with restrictive lung diseases typically experience difficulty in inhaling enough air, leading to a decreased total lung capacity.

In contrast, obstructive lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD), are distinguished by increased airway resistance, which primarily affects the ability to exhale fully. While obstructive diseases can lead to trapped air in the lungs, restrictive diseases are concerned with the overall reduction of lung volume and difficulty in getting air in.

Furthermore, restrictive lung diseases generally do not improve gas exchange since the reduced lung volumes can lead to inadequate ventilation and oxygenation, contrasting with conditions where airway resistance is treated effectively. Increased lung compliance is also not a feature of restrictive lung diseases; in fact, compliance is usually decreased, as the lungs and/or chest wall become stiff and less compliant.

Thus, the defining characteristic of restrictive lung diseases is the reduction of lung volume, which is central to understanding how these conditions