Determinants of surfactant function in acute lung injury and early recovery

Relationships between lung function and surfactant function and composition were examined during the evolution of acute lung injury in guinea pigs. Lu ng mechanics and gas exchange were assessed 12, 24, or 48 h after exposure to nebulized lipopolysaccharide (LPS). Bronchoalveolar lavage (BAL) fluid w as processed for phospholipid and protein contents and surfactant protein ( SP) A and SP-B levels; surfactant function was measured by pulsating bubble surfactometry. Lung elastance, tissue resistance, and arterial-alveolar gr adient were moderately elevated by 12 h after LPS exposure and continued to increase over the first 24 h but began to recover between 24 and 48 h. Sim ilarly, the absolute amount of 30,000 g pelleted SP-A and SP-B, the phospho lipid content of BAL fluid, and surfactant function declined over the first 24 h after exposure, with recovery between 24 and 48 h. BAL fluid total pr otein content increased steadily over the first 48 h after LPS nebulization . In this model of acute lung injury, the intra-alveolar repletion of surfa ctant components in early recovery led to improved surfactant function desp ite the presence of potentially inhibitory plasma proteins.