Acute respiratory distress

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. Among those who survive, a decreased quality of life is relatively common. 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. Among those who survive, a decreased quality of life is relatively 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. Diagnosis is based on a PaO2/FiO2 ratio of less than 300 mmHg despite a PEEP of more than 5 cm H2O. Heart related pulmonary edema, as the cause, must be excluded. 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 paralysis may be tried. If this is insufficient ECMO may be an option. The syndrome is associated with a death rate between 35 and 50%. ARDS affects about 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 modified diagnostic criteria for children and areas of the world with less resources. The signs and symptoms of ARDS often begin within two hours of an inciting event, but can occur after 1–3 days. Signs and symptoms may include shortness of breath, fast breathing, and a low oxygen level in the blood due to abnormal ventilation. Diffuse compromise of the pulmonary system resulting in ARDS generally occurs in the setting of critical illness. ARDS may be seen in the setting of severe pulmonary (pneumonia) or systemic infection (sepsis), following trauma, multiple blood transfusions (TRALI), severe burns, severe inflammation of the pancreas (pancreatitis), near-drowning or other aspiration events, drug reactions, or inhalation injuries. Some cases of ARDS are linked to large volumes of fluid used during post-trauma resuscitation. ARDS is a form of fluid accumulation in the lungs not explained by heart failure (noncardiogenic pulmonary edema). It is typically provoked by an acute injury to the lungs that results in flooding of the lungs' microscopic air sacs responsible for the exchange of gases such as oxygen and carbon dioxide with capillaries in the lungs. Additional common findings in ARDS include partial collapse of the lungs (atelectasis) and low levels of oxygen in the blood (hypoxemia). The clinical syndrome is associated with pathological findings including pneumonia, eosinophilic pneumonia, cryptogenic organizing pneumonia, acute fibrinous organizing pneumonia, and diffuse alveolar damage (DAD). Of these, the pathology most commonly associated with ARDS is DAD, which is characterized by a diffuse inflammation of lung tissue. The triggering insult to the tissue usually results in an initial release of chemical signals and other inflammatory mediators secreted by local epithelial and endothelial cells. Neutrophils and some T-lymphocytes quickly migrate into the inflamed lung tissue and contribute in the amplification of the phenomenon. Typical histological presentation involves diffuse alveolar damage and hyaline membrane formation in alveolar walls. Although the triggering mechanisms are not completely understood, recent research has examined the role of inflammation and mechanical stress. Diagnostic criteria for ARDS have changed over time as understanding of the pathophysiology has evolved. The international consensus criteria for ARDS were most recently updated in 2012 and are known as the 'Berlin definition'. In addition to generally broadening the diagnostic thresholds, other notable changes from the prior 1994 consensus criteria include discouraging the term 'acute lung injury,' and defining grades of ARDS severity according to degree of decrease in the oxygen content of the blood.