Acute respiratory distress syndrome
Acute respiratory distress syndrome (ARDS) is a type of respiratory failure characterized by rapid onset of widespread inflammation in the lungs. Symptoms include shortness of breath, rapid breathing, and bluish skin coloration. For those who survive, a decreased quality of life is common.
Causes
Causes may include sepsis, pancreatitis, trauma, pneumonia, and aspiration. The underlying mechanism involves diffuse injury to cells which form the barrier of the microscopic air sacs of the lungs, surfactant dysfunction, activation of the immune system, and dysfunction of the body's regulation of blood clotting. In effect, ARDS impairs the lungs' ability to exchange oxygen and carbon dioxide. Adult diagnosis is based on a PaO2/FiO2 ratio (ratio of partial pressure arterial oxygen and fraction of inspired oxygen) of less than 300 mm Hg despite a positive end-expiratory pressure (PEEP) of more than 5 cm H2O. Heart-related pulmonary edema, as the cause, must be excluded.
Signs and symptoms
The
signs and symptoms of ARDS often begin within two hours of an inciting
event, but have been known to take as long as 1–3 days; diagnostic
criteria require a known insult to have happened within 7 days of the
syndrome. Signs and symptoms may include shortness of breath, fast breathing, and a low oxygen level in the blood due to abnormal ventilation. Other common symptoms include muscle fatigue and general weakness, low blood pressure, a dry, hacking cough, and fever.
There are direct and indirect causes of ARDS depending whether the lungs are initially affected. Direct causes include pneumonia
(including bacterial and viral), aspiration, inhalational lung injury,
lung contusion, chest trauma, and near-drowning. Indirect causes include
sepsis, shock, pancreatitis, trauma (e.g. fat embolism), cardiopulmonary bypass, TRALI, burns, increased intracranial pressure. Fewer cases of ARDS are linked to large volumes of fluid used during post-trauma resuscitatio.
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