This study examines
surfactant dysfunction in rats with inflammatory
lung injury from intratracheal instillation of
hydrochloric acid (
ACID, pH 1.25), small nonacidified gastric particles (SNAP), or combined
acid and small gastric particles (CASP). Rats given CASP had the most severe
lung injury at 6, 24, and 48 h based on decreases in arterial oxygenation and increases in erythrocytes, total leukocytes, neutrophils, total
protein, and
albumin in bronchoalveolar lavage (BAL). The content of large
surfactant aggregates in BAL was reduced in all forms of aspiration injury, but decreases were greatest in rats given CASP. Large aggregates from aspiration-injured rats also had decreased levels of
phosphatidylcholine (PC) and increased levels of
lyso-PC and total
protein compared with saline controls (abnormalities for CASP were greater than for SNAP or
ACID alone). The surface tension-lowering ability of large
surfactant aggregates on a bubble surfactometer was impaired in rats with aspiration injury at 6, 24, and 48 h, with the largest activity reductions found in animals given CASP. There were strong statistical correlations between
surfactant dysfunction (increased minimum surface tension and reduced large aggregate content) and the severity of
lung injury based on arterial oxygenation and levels of
albumin,
protein, and erythrocytes in BAL (P < 0.0001).
Surfactant dysfunction also correlated strongly with reduced lung volumes during inflation and deflation (P = 0.0004-0.005). These results indicate that
surfactant abnormalities are functionally important in gastric aspiration
lung injury and contribute significantly to the increased severity of injury found in CASP compared with
ACID or SNAP alone.