PathophysiologyOne of the important anatomical alterations in ARDS is alveolar damage. The damage to the alveoli is due to the accumulation of fluids as well as the compromised respiratory mechanism. The condition is also related to damage to the lung endothelium. ARDS occurs in three stages in which damage occurs to both the alveoli and the endothelium. The three phases are exudative, proliferative and fibrotic. Exudative phase Occurs approximately during the first week and usually begins within 24 to 48 hours after direct lung injury. In this phase, injury to endothelial cells of alveolar capillaries and type I pneumocytes causes interstitial alveolar edema (noncardiogenic pulmonary edema) and atelectasis. Fluid containing proteins accumulates in the interstitial and alveolar spaces. In this acute phase there is a massive concentration of cytokines and lipid mediators in the lung. In response to proinflammatory mediators, leukocytes move into the interstitia and alveoli. Furthermore, plasma proteins accumulate in the air spaces with cellular debris and dysfunctional lung surfactant to form the hyaline membrane. Refractory hypoxemia occurs due to severe V/Q mismatch and pulmonary capillary shunting. Respiratory alkalosis and increased cardiac output occur as a result of increased respiratory rate and heart rate as a compensatory mechanism for hypoxemia (Levy & Choi., 2012). Proliferative Phase This phase of ARDS usually lasts from day 7 to day 21. Some patients recover rapidly and are disconnected from mechanical ventilation during this phase. Despite the improvement, many patients still suffer from shortness of breath, tachypnea, and hypoxemia. There are some patients who have developed pulmonary injection... middle of paper... respiratory distress syndrome after lung resection. General thoracic and cardiovascular surgery, 61(9), 504-512. Doi: 10.1007/s11748-013-0276-7Marini, J. (2013). Mechanical ventilation: past lessons and near future. Critical Care (London, England), 17 Suppl 1S1. doi:10.1186/cc11499Villar, J. (2011). What is Acute Respiratory Distress Syndrome?... 26th New Horizons Symposium, “ARDS Update,” at the 56th International Respiratory Congress of the American Association for Respiratory Care, held December 6-9, 2010, Las Vegas, Nevada . Respiratory Care, 56(10), 1539-1545. doi:10.4187/respcare.01395Smith DA (2011). Chapter 33. Pulmonary emergencies. In Stone C, Humphries RL (eds), CURRENT Diagnosis & Treatment Emergency Medicine, 7e. Retrieved March 20, 2014, from http://accessmedicine.mhmedical.com.suproxy.su.edu/content.aspx?bookid=385&Sectionid=40357249.