Table 3 Features and measurements of acute lung injury in animal models

Histological evidence of tissue injury

Accumulation of neutrophils in the alveolar or the interstitial space

Formation of hyaline membranes

Presence of proteinaceous debris in the alveolar space (such as fibrin strands)

Thickening of the alveolar wall

Enhanced injury as measured by a standardized histology score

Alteration of the alveolar capillary barrier

An increase in extravascular lung water content

Accumulation of an exogenous protein or tracer in the airspaces or the extravascular compartment

Increase in total bronchoalveolar lavage (BAL) protein concentration

Increase in concentration of high molecular weight proteins in BAL fluid (for example albumin, IgM)

Increase in the microvascular filtration coefficient

Inflammatory response

Increase in the absolute number of neutrophils in BAL fluid

Increase in lung myeloperoxidase (MPO) activity or protein concentration

Increase in the concentrations of cytokines in lung tissue or BAL fluid (IFN-γ, TNF-α, IL-6, IL-1β, chemokine (C-X-C motif) ligand2, chemokine (C-C motif) ligand 2, IL-8, IL-10, prostaglandin E2, IL-1 receptor antagonist)

Physiological dysfunction

Hypoxemia

Increased alveolar-oxygen difference