Acute respiratory distress syndrome overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Brian Shaller, M.D. [2]
Overview
Acute respiratory distress syndrome (ARDS), originally known as adult respiratory distress syndrome (to contrast with neonatal respiratory distress syndrome) is a serious and potentially life-threatening inflammatory lung condition that develops rapidly (usually within 24 to 48 hours) in the setting of sepsis, toxic exposures, adverse drug reactions, trauma, or other critical illnesses. ARDS is characterized by inflammation of the lung parenchyma resulting in increased permeability of the alveolar-capillary membrane, non-cardiogenic pulmonary edema, impaired gas exchange, and decreased lung compliance.
The vast majority of patients with ARDS are managed in an intensive care unit (ICU), where many will require mechanical ventilation at some point during the course of their illness and recovery. ARDS may be categorized as mild, moderate, or severe based on the degree to which oxygenation is impaired; however, all levels of severity carry a high mortality rate if appropriate measures to improve oxygenation and minimize the risk of further lung injury are not taken.[1]
Historical Perspective
Although the pathologic features of ARDS were first documented in the 19th century, the modern definition of ARDS did not arise until the 1960s. In 2012, the Berlin Definition of ARDS became the standard diagnostic criteria and definition of the syndrome.
Classification
ARDS may be classified according to 2012 Berlin Definition into three subtypes: mild, moderate, and severe. These levels of severity are based on the degree to which oxygenation relative to the amount of supplemental oxygen is being delivered to the patient via positive pressure ventilation.[1]
Pathophysiology
ARDS is a syndrome of inflammation and increased permeability with the lung parenchyma that leads to loss of type I pneumocytes, impaired gas exchange, inappropriate cell proliferation within alveoli, and, in survivors, fibrosis.
Causes
ARDS may be caused by either direct or indirect insults to the lung. Common causes of ARDS include sepsis, aspiration pneumonitis, and transfusion-related acute lung injury (TRALI).[2]
Differentiating ARDS from Other Diseases
ARDS must be differentiated from other diseases that cause hypoxemia and pulmonary infiltrates, such as pneumonia, pulmonary contusion, pulmonary edema, and pulmonary hemorrhage. Prior to the development of the Berlin Definition in 2012, a greater emphasis was placed on excluding other potential illnesses prior to making a diagnosis of ARDS. While it is important to recognize and treat and underlying cause of the patient's impaired ventilation and hypoxemia, this search for potential etiologies should not delay any focused efforts to improve oxygenation and ventilation.
Epidemiology and Demographics
The incidence of ARDS in the United States is estimated at approximately 75 cases per 100,000 individuals, which amounts to roughly 150,000 new cases annually.[3] There is substantial variance in the rates of ARDS between different countries and geographic regions due to factors such as mean life expectancy, prevalence of different risk factors and comorbidities, and access to healthcare.
Risk Factors
The most potent risk factor in the development of ARDS is chronic alcoholism.[4][5] Other risk factors include advanced age, cigarette smoke exposure, and chronic liver disease.
References
- ↑ 1.0 1.1 ARDS Definition Task Force. Ranieri VM, Rubenfeld GD, Thompson BT, Ferguson ND, Caldwell E; et al. (2012). "Acute respiratory distress syndrome: the Berlin Definition". JAMA. 307 (23): 2526–33. doi:10.1001/jama.2012.5669. PMID 22797452.
- ↑ Pepe PE, Potkin RT, Reus DH, Hudson LD, Carrico CJ (1982). "Clinical predictors of the adult respiratory distress syndrome". Am J Surg. 144 (1): 124–30. PMID 7091520.
- ↑ Lucas AC (1988). "The future of radiological instrumentation". Health Phys. 55 (2): 191–5. PMID 3410685.
- ↑ Moss M, Bucher B, Moore FA, Moore EE, Parsons PE (1996). "The role of chronic alcohol abuse in the development of acute respiratory distress syndrome in adults". JAMA. 275 (1): 50–4. PMID 8531287.
- ↑ Moss M, Burnham EL (2003). "Chronic alcohol abuse, acute respiratory distress syndrome, and multiple organ dysfunction". Crit Care Med. 31 (4 Suppl): S207–12. doi:10.1097/01.CCM.0000057845.77458.25. PMID 12682442.