ARDS: Acute Respiratory Distress Syndrome. A fulminant lung condition in which trauma to the lungs leads to inflammation of the lungs, accumulation of fluid in the alveolar air sacs, low blood oxygen, and respiratory distress.

In ARDS there is sudden respiratory failure due to the rapid accumulation of fluid in the lungs following an abrupt increase in the permeability of the normal barrier between the capillaries and the air sacs in the lungs. In ARDS, the tiny blood vessels (capillaries) in the lungs or the air sacs (alveoli) are damaged. Fluid leaks from the blood vessels into air sacs of the lungs. While some air sacs fill with fluid, others collapse. When the air sacs collapse or fill up with fluid, the lungs can no longer fill properly with air and the lungs become stiff. And without air entering the lungs properly, the amount of oxygen in the blood drops. ARDS is the most serious response to acute lung injury.

ARDS is not a specific disease. It is a response to acute injury of the lungs. The types of trauma that may lead to ARDS are very diverse and include breathing in vomited stomach contents (aspiration), inhalation of smoke or fumes toxic to the lungs, widespread infection of the lungs as in bilateral pneumonia, sepsis (bloodstream infection), near drowning, a major blood loss, shock, direct trauma to the chest, and some drug overdoses.

ARDS forces the muscles of the lungs to work harder causing labored breathing (huffing and puffing). Despite the effort, breathing is inefficient. There is hypoxemia (an abnormally low level of oxygen in the blood), a characteristic feature of ARDS.

ARDS is a life-threatening condition. Treatment frequently involves the use of oxygen and a mechanical ventilator to help breathing. Breathing failure can occur very quickly after the condition begins. It may take only a day or two for fluid to build up. The process that causes ARDS may continue for weeks. If scarring occurs, this will make it harder for the lungs to take in oxygen and get rid of carbon dioxide.

In the past, only about 4 out of 10 people who developed ARDS survived. But today, with good care in a hospital's intensive or critical care unit, on the average about 7 out of 10 people with ARDS survive. Although many people who survive ARDS make a full recovery, some survivors have lasting damage to their lungs.

ARDS is also known as adult respiratory distress syndrome, stiff lung, shock lung, and wet lung.