How does acute respiratory distress syndrome (ARDS) progress following injury to alveoli?

Updated: Mar 27, 2020
  • Author: Eloise M Harman, MD; Chief Editor: Michael R Pinsky, MD, CM, Dr(HC), FCCP, FAPS, MCCM  more...
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Answer

ARDS expresses itself as an inhomogeneous process. Relatively normal alveoli, which are more compliant than affected alveoli, may become overdistended by the delivered tidal volume, also known as volutrauma, resulting in barotrauma (pneumothorax and interstitial air). Alveoli already damaged by ARDS may experience further injury from the shear forces exerted by the cycle of collapse at end-expiration and reexpansion by positive pressure at the next inspiration (so-called atelectrauma).

In addition to the mechanical effects on alveoli, these forces promote the secretion of proinflammatory cytokines with resultant worsening inflammation and pulmonary edema. The use of positive end-expiratory pressure (PEEP) to diminish alveolar collapse and the use of low tidal volumes and limited levels of inspiratory filling pressures appear to be beneficial in diminishing the observed VALI.


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