What condition is defined as a pathologic reduction in the volume of air in the lungs?

Restrictive lung disease is characterized by a pathologic reduction in the volume of air that can be inhaled by the lungs, leading to decreased lung compliance. This condition results from factors that restrict lung expansion, such as stiff or fibrotic lung tissue, pleural diseases, or conditions affecting the chest wall, like obesity or neuromuscular disorders.

In restrictive lung disease, patients typically experience difficulty taking deep breaths, resulting in a reduced total lung capacity and vital capacity. This diminutive lung capacity contributes to hypoxemia, as less air can lead to lower oxygen intake.

Other conditions listed—such as obstructive lung disease, pneumothorax, and asthma—are characterized by different mechanisms. Obstructive lung diseases, for example, involve restricted airflow due to obstruction of the airways, while pneumothorax refers to the presence of air in the pleural space that can lead to lung collapse. Asthma involves reversible airway obstruction due to an inflammatory response but does not inherently involve a reduction in lung volume like restrictive diseases do.