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 (dyspnea), rapid breathing (tachypnea), and bluish skin coloration (cyanosis). For those who survive, a decreased quality of life is common.
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. Cardiogenic pulmonary edema, as the cause, must be excluded.
Environmental exposures have been associated with an increased susceptibility to acute respiratory distress syndrome (ARDS). Chronic exposure to ambient air pollution, such as fine particulate matter (PM2.5) and ozone, have been linked to higher risks of developing ARDS following acute events such as sepsis or trauma. The exposures are thought to contribute to baseline pulmonary inflammation and endothelial dysfunction, potentially amplifying the response to subsequent lung injury. Some studies have also reported associations between higher ambient ozone levels and increased mortality among patients with ARDS.
The primary treatment involves mechanical ventilation together with treatments directed at the underlying cause. Ventilation strategies include using low volumes and low pressures. If oxygenation remains insufficient, lung recruitment maneuvers and neuromuscular blockers may be used. If these are insufficient, extracorporeal membrane oxygenation (ECMO) may be an option. The syndrome is associated with a death rate between 35 and 46%.
Globally, ARDS affects more than 3 million people a year. The condition was first described in 1967. Although the terminology of "adult respiratory distress syndrome" has at times been used to differentiate ARDS from "infant respiratory distress syndrome" in newborns, the international consensus is that "acute respiratory distress syndrome" is the best term because ARDS can affect people of all ages. There are separate diagnostic criteria for children and those in areas of the world with fewer resources.

Environmental and geographic factors may also contribute to variation in ARDS incidence and outcomes, as populations with higher exposure to air pollution have demonstrated increased susceptibility and worse clinical outcomes. ARDS accounts for approximately 10% of intensive care unit (ICU) admissions and up to 23% of patients requiring mechanical ventilation, with mortality rates ranging from 30% to 45% depending on severity and comorbid conditions.