Mechanisms of Acute Lung Injury/Acute Respiratory Distress Syndrome

Although we remain at a relatively early stage in our understanding of obesity’s effects on acute respiratory distress syndrome (ARDS), mounting data suggest that a complex and as of yet incompletely understood interaction exists. Clinical studies examining the effects of obesity suggest that a rising body mass index (BMI) is associated with an increased risk for the development of ARDS and other organ failures, as might be predicted from the baseline systemic proinflammatory state that accompanies obesity. Interestingly, however, substantial evidence also indicates that subsequent mortality from ARDS and from critical illness, in general, is in fact lower in obese patients. Although some controversy has accompanied these latter findings, additional studies carefully adjusting for potentially confounding diagnostic artifacts and process of care effects have confirmed this association. The expanding clinical and animal model data available suggest that, although the obesity-associated increase in risk for the development of ARDS may reflect inflammatory and biomechanical “priming” of the lung for this disease, the witnessed obesity-associated survival advantage may in part be driven by an attenuation of the inflammatory milieu in such patients with established ARDS.