Acute respiratory distress syndrome: Clinical

Acute respiratory distress syndrome, or ARDS is a condition where there’s inflammation throughout the lungs leading to pulmonary edema.

The main site of injury in ARDS is the alveolar-capillary membrane.

Now, any damage to the alveolar epithelium or the capillary endothelium increases the permeability of the alveolar-capillary membrane, causing fluid to move into the alveoli.

Oxygen and carbon dioxide have to travel across this fluid, so it acts as a barrier against normal gas exchange.

The fluid also dilutes out the surfactant molecules coating the alveoli, and as a result the alveoli are less able to remain open and compliant, so they become stiff.

If the injury continues, the alveoli eventually collapse.

Now, the pulmonary edema from ARDS causes the same problems as pulmonary edema from congestive heart failure, but because the triggering events are different, the term non-cardiogenic pulmonary edema is often used for ARDS.

Now, ARDS is not a primary lung disease, rather it arises as a complication of a systemic injury that causes widespread inflammation which results in damage to the alveolar-capillary membranes within the lung.

The most common underlying systemic cause of ARDS is sepsis, which causes systemic inflammation in response to an infection.

But other insults include trauma, severe burns, near-drowning, disseminated intravascular coagulation or DIC, acute pancreatitis, massive blood transfusions, aspiration of gastric contents, and toxic smoke inhalation.