Determinants of surfactant function in acute lung injury and early recovery

Abstract

Relationships between lung function and surfactant function and composition were examined during the evolution of acute lung injury in guinea pigs. Lung mechanics and gas exchange were assessed 12, 24, or 48 h after exposure to nebulized lipopolysaccharide (LPS). Bronchoalveolar lavage (BAL) fluid was 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 gradient 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. Similarly, the absolute amount of 30,000 g pelleted SP-A and SP-B, the phospholipid 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 protein content increased steadily over the first 48 h after LPS nebulization. In this model of acute lung injury, the intra-alveolar repletion of surfactant components in early recovery led to improved surfactant function despite the presence of potentially inhibitory plasma proteins.

Variable Tidal Volume Ventilation Improves Lung Mechanics and Gas Exchange in a Rodent Model of Acute Lung Injury

“…The animal model employed in this study causes biological and physiological changes that mimic those of human ARDS. As previously reported by Mora and coworkers (15), nebulized endotoxin results in neutrophil influx into the alveolar space, capillary leakage, increased tissue elastance, impaired gas exchange, and surfactant dysfunction, all characteristics observed in human patients during respiratory distress. We used volume-cycled ventilation applied to simulate open lung ventilation (V T ϭ 5.1 ml/kg) in accordance with the current convention that large-volume excursions are a probable source of ventilator-induced lung injury (19).…”

“…Lung mechanics were assessed by the optimal ventilator waveform technique, a forced oscillation method that uses an input volume consisting of six sine waves with frequencies between 0.5 and 14.25 Hz (15). These have been selected to minimize the nonlinear interactions at the input frequencies (16).…”

Effects of a recombinant surfactant protein-C-based surfactant on lung function and the pulmonary surfactant system in a model of meconium aspiration syndrome*

“…In accordance with these findings, other studies have shown recovery of the pulmonary surfactant system indicated by SP-B and -C concentrations reaching baseline levels not earlier than 4 hrs after induction of lung injury (40). In animal mod- els of ARDS, even up to 48 hrs have been reported for an increase of surfactant proteins after lung failure (41).…”

Acute chlorine gas exposure produces transient inflammation and a progressive alteration in surfactant composition with accompanying mechanical dysfunction

“…In the setting of vascular leak fibrin and albumin may interfere substantially with surface active function as demonstrated by BAL capillary surfactometry (Enhorning and Holm, 1993). Ingenito and colleagues (Mora et al , 2000; Ingenito et al , 2001) have observed alteration in surfactant composition, with BAL surface tension increases, correlated with significant alteration to Z rs in the early inflammatory phase following acute intratracheal endotoxin exposure. In contrast to our exposure model, where pulmonary injury is limited and mechanical dysfunction subtle, the endotoxin injury demonstrated both more severe mechanical dysfunction associated with increased vascular leak as well as more dramatic alteration of surfactant content and function.…”