What is the primary effect of increased capillary permeability in lung injury?

Increased capillary permeability in lung injury leads to pulmonary edema primarily due to the disruption of the normal blood-gas barrier. When capillaries become more permeable, proteins and fluid leak into the interstitial spaces of the lung tissue. This accumulation of fluid can overwhelm the lymphatic drainage system and lead to interstitial and alveolar edema.

As fluid fills the alveoli, it interferes with gas exchange by increasing the distance that oxygen and carbon dioxide must diffuse, thus impairing oxygen transport. Furthermore, if the edema becomes severe, it can fill the alveoli, making it even more difficult for gas exchange to occur. This process is a hallmark of various lung injuries, such as acute respiratory distress syndrome (ARDS), where increased permeability is a key feature.

While increased capillary permeability can influence other aspects of lung function and systemic health, the most immediate and recognizable consequence in the context of lung injury is indeed pulmonary edema. This condition leads to significant clinical implications, including respiratory distress and hypoxia, as the functionality of the lung is compromised by the presence of excess fluid.