Acute respiratory distress syndrome (ARDS) is a life-threatening lung condition that prevents enough oxygen from getting into the blood.

See also: Infant respiratory distress syndrome

ARDS can be caused by any major swelling (inflammation) or injury to the lung. Some common causes include:

• Breathing vomit into the lungs (aspiration)
• Inhaling chemicals
• Pneumonia
• Septic shock
• Trauma

ARDS leads to a buildup of fluid in the air sacs. This fluid prevents enough oxygen from passing into the bloodstream.

The fluid buildup also makes the lungs heavy and stiff, and decreases the lungs' ability to expand. The level of oxygen in the blood can stay dangerously low, even if the person receives oxygen from a breathing machine (mechanical ventilator) through a breathing tube (endotracheal tube).

ARDS often occurs along with the failure of other organ systems, such as the liver or the kidneys. Cigarette smoking and heavy alcohol use may be risk factors.

• Labored, rapid breathing
• Low blood pressure and organ failure
• Shortness of breath

Symptoms usually develop within 24 to 48 hours of the original injury or illness. Often, people with ARDS are so sick they are unable to complain of symptoms.

Listening to the chest with a stethoscope (auscultation) reveals abnormal breath sounds, such as crackles that suggest fluid in the lungs. Often the blood pressure is low. Cyanosis (blue skin, lips, and nails caused by lack of oxygen to the tissues) is often seen.

Tests used to diagnose ARDS include:

• Arterial blood gas
• Bronchoscopy
• CBC and blood chemistries
• Chest x-ray
• Sputum cultures and analysis
• Tests for possible infections

Occasionally an echocardiogram or Swan-Ganz catheterization may need to be done to rule out congestive heart failure, which can look similar to ARDS on a chest x-ray.