THE STAGES OF ARDS

ARDS has generally been characterized into three stages. In full-blown cases, these three stages unfold sequentially over a period of several weeks to several months.

1 Exudative stage: Characterized by accumulation in the alveoli of excessive fluid, protein and inflammatory cells that have entered the air spaces from the alveolar capillaries. The exudative phase unfolds over the first 2 to 4 days after onset of lung injury.

2 Fibroproliferative (or proliferative) stage: Connective tissue and other structural elements in the lungs proliferate in response to the initial injury. Under a microscope, lung tissue appears densely cellular. Also, at this stage, there is a danger of pneumonia sepsis and rupture of the lungs causing leakage of air into surrounding areas.

3 Resolution and Recovery: During this stage, the lung reorganizes and recovers. Lung function may continue to improve for as long as 6-12 months and sometimes longer, depending on the precipitating condition and severity of the injury. It is important to remember that there may be and often are different levels of pulmonary recovery amongst individuals who suffer from ARDS.

Some experts recognize a fourth phase of ARDS. This is the period longer than six to twelve months after onset, when some patients experience continued health problems caused by the acute illness. These problems may include cough, limited exercise tolerance and fatigue. Others experience anxiety, depression and flashback memories of their critical illness, which are very similar to post-traumatic stress disorder. This fourth phase is incompletely characterized, and is very much in need of research.