Acute Respiratory Distress Syndrome

The following criteria define the syndrome of ARDS:

1. Clinical evidence of respiratory distress
2. Chest x-ray revealing diffuse air space disease (pulmonary edema)
3. Hypoxia that is difficult to correct with oxygen supplementation (shunt)
4. Pulmonary capillary occlusion (wedge) pressure < 18 mm Hg (absence of cardiogenic pulmonary edema [CHF])
5. Total thoracic static compliance <40 ml/cm of water

Causes

A number of clinical conditions are associated with development of ARDS.

• Sepsis and the systemic inflammatory response syndrome (SIRS) are the most common predisposing factors associated with development of ARDS. These conditions may result from the indirect toxic effects of neutrophil-derived inflammatory mediators in the lungs.
• Infection - Pneumonia of any etiology and systemic sepsis (especially gram negative)
• Aspiration - Gastric contents, near drowning, and toxic inhalation
• Drug overdose
• Viral pneumonias
• Toxic inhalations
• Fracture of the long bones
• Blood transfusion

Symptoms

• Dyspnea
• Dry (nonproductive) cough
• Retrosternal discomfort
• Agitation
• Onset over hours to days

Signs

• Hypoxia (common) progressing to respiratory failure
• Tachypnea
• Coarse crackles with bronchial breath sounds (although chest examination may be relatively unimpressive for the abnormalities seen on chest x-ray)
• Signs of serious underlying disease, often including multisystem organ dysfunction

Treatment

The objective of treatment is to provide enough support for the failing respiratory system until these systems have time to heal. Treatment of the underlying condition that caused ARDS is essential.

The main supportive treatment of the failing respiratory system in ARDS is mechanical ventilation (a breathing machine) to deliver high doses of oxygen and a continuous level of pressure called PEEP to the damaged lungs.

Persons with ARDS are hospitalized and require treatment in an intensive care unit.