Atelectasis II: Pathophysiology

Atelectasis is the collapse of alveoli, resulting in loss of aeration of part or the entire lung. Because lung tissue is naturally elastic, the empty sacs shrink inward.

This mainly affects ventilation, where the movement of air in and out of the lungs is reduced or may stop entirely in the affected region.

However, blood flow, or perfusion, often continues in that same area. This ventilation-perfusion mismatch prevents oxygen from being effectively transported into the bloodstream, resulting in hypoxemia.

Carbon dioxide levels may initially remain normal as it diffuses more readily than oxygen, and hyperventilation happens in unaffected alveoli.

However, if atelectasis is extensive or prolonged, this compensation fails, and hypercapnia can develop.

As a result, patients may develop shortness of breath, rapid breathing, coughing, chest pain, and cyanosis.