Acute respiratory distress syndrome

Acute respiratory distress syndrome
Other names	Respiratory distress syndrome (RDS), adult respiratory distress syndrome, shock lung, wet lung
Chest x-ray
Specialty	Critical care medicine
Symptoms	Shortness of breath, rapid breathing, bluish skin coloration, chest pain, loss of speech[1]
Complications	Blood clots, Collapsed lung (pneumothorax), Infections, Scarring (pulmonary fibrosis)[2]
Usual onset	Within a week[1]
Diagnostic method	Adults: PaO2/FiO2 ratio of less than 300 mm Hg[1] Children: oxygenation index > 4[3]
Differential diagnosis	Heart failure[1]
Treatment	Mechanical ventilation, ECMO[1]
Prognosis	35 to 90 % risk of death[1]
Frequency	3 million per year[1]

Acute respiratory distress syndrome (ARDS) is a type of respiratory failure characterized by rapid onset of widespread inflammation in the lungs.^[1] Symptoms include shortness of breath (dyspnea), rapid breathing (tachypnea), and bluish skin coloration (cyanosis).^[1] For those who survive, a decreased quality of life is common.^[4]

Causes may include sepsis, pancreatitis, trauma, pneumonia, and aspiration.^[1] 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.^[5] In effect, ARDS impairs the lungs' ability to exchange oxygen and carbon dioxide.^[1] 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.^[1] Cardiogenic pulmonary edema, as the cause, must be excluded.^[4]

The primary treatment involves mechanical ventilation together with treatments directed at the underlying cause.^[1] Ventilation strategies include using low volumes and low pressures.^[1] If oxygenation remains insufficient, lung recruitment maneuvers and neuromuscular blockers may be used.^[1] If these are insufficient, extracorporeal membrane oxygenation (ECMO) may be an option.^[1] The syndrome is associated with a death rate between 35 and 50%.^[1]

Globally, ARDS affects more than 3 million people a year.^[1] The condition was first described in 1967.^[1] 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.^[6] There are separate diagnostic criteria for children and those in areas of the world with fewer resources.^[4]