What is ARDS?
A low ratio of the
partial pressure of
arterial oxygen to the
fraction of inhaled
oxygen
The acute onset
of bilateral
infiltrates on
chest x-ray, not
explained by
cardiac failure
or fluid overload
Pathophysiology
●
Can occur:
○ Directly → aspiration of highly acidic gastric contents, inhalation of toxic
gases, development of pneumonia
○ Indirectly → circulating proinflammatory mediators released in response to
systemic disorders (such as, sepsis, trauma, and multiple transfusions)
Acute immune cell-mediated injury to the alveolocapillary membrane produces
massive inflammation, increased capillary permeability and alveolar flooding with
protein rich fluid that overwhelms ion channels and lymphatic removal of fluid. This
leads to increasingly severe pulmonary edema (aka noncardiogenic pulmonary
edema) with associated shunting, VQ mismatch, reduced lung compliance, and