Acute Respiratory Distress Syndrome (ARDS) Overview
The cardinal feature of ARDS is sustained or refractory hypoxemia and decreased pulmonary compliance. The patient will likely experience dyspnea with pulmonary edema. Imaging will often indicate the presence of infiltrates frequently described as having a “ground glass” appearance. Patients can experience ARDS as a result of an existing lung disorder or with no prior history of respiratory disease as a result of an acute lung injury. The source of the acute lung injury could be an aspiration event, therapeutic or illicit medication(s), an inhalation injury, an infection such as sepsis, a traumatic injury, a medical disorder such pancreatitis, disseminated intravascular coagulation, or multiple blood transfusions amongst others (Grossman & Porth, 2014; Ignatavicius, Workman & Rebar, 2018; National Heart, Lung, & Blood Institute [NHLBI], 2019).
ARDS was initially given the name adult respiratory distress syndrome in 1967 when it was first diagnosed in an adult patient. It was later recognized that this disorder also occurred in children, requiring a name change to acute respiratory distress syndrome. This also replaced other names that include shock lung, wet lung, acute lung injury, noncardiac pulmonary edema, and stiff lung. There is a difference between acute lung injury (ALI) and ARDS. In 1994, during an American-European Consensus Conference, it was established that ALI and ARDS would be distinguished based on the level of hypoxemia the patient exhibited, with ARDS having a higher level of hypoxemia. This would be evaluated with objective data using the PO2 to FiO2 ratio. This was important to assist healthcare providers in determining the correct diagnosis to implement new treatment options as well as tools for prevention and continued research. This definition was updated in 2011 and is known as the Berlin definition, which further categorizes patients with ARDS into three categories. These categories include mild, moderate, and severe ARDS, with specific parameters for healthcare providers to utilize in the diagnostic process (Grossman & Porth, 2014; Ignatavicius et al., 2018; Ranieri et al., 2012).
It is challenging to know the exact number of cases that occur, but the ARDS Foundation estimates there are approximately 150,000 new cases annually in the United States. Some healthcare providers believe this estimate is low and that the actual numbers are higher as ARDS often exists with another disorder, which is more likely to be the disorder that is reported. It is estimated that approximately 42% of cases of ARDS are fatal (Ignatavicius et al., 2018).