SURFACTANT COMPOSITION REFLECTS LUNG OVERINFLATION AND ARTERIAL OXYGENATION IN PATIENTS WITH ACUTE LUNG INJURY

Pulmonary surfactant abnormalities have consistently been documented i n patients with acute lung injury (ALI), however, there is little evid ence directly correlating them to altered respiratory mechanics. To ex plore this further, surfactant composition was measured in lung aspira te fluid collected on 15 occasions from 10 patients with ALI, The comp osition was compared with lung aspirate fluid from 11 intubated patien ts prior to elective cardiac surgery (CS), and bronchoalveolar lavage fluid from 16 normal subjects, In both the ALI and cardiac groups the proportion of disaturated phospholipids (DSP) and phosphatidylcholine was reduced. Plasma levels of surfactant proteins-A and -B (SP-A and - B) were elevated, but were unrelated to alveolar surfactant levels. In the ALI group, and the ALI + CS group, DSP, normalized to the total p hospholipid content, sphingomyelin (SPH), and urea, showed strong dire ct correlations with arterial oxygen tension/inspiratory oxygen fracti on (all p less than or equal to 0.01). In the ALI group, normalized DS P was also directly related to the elastance of the positive end-expir atory pressure-induced increase in the end-expiratory lung volume (all p less than or equal to 0.02), and indirect correlations were found w ith a measure of lung overinflation (%E-2; all p less than or equal to 0.01). We conclude that surfactant composition correlates with lung f unction abnormalities in acute lung injury and cardiac patients, and t hat both groups had elevated plasma surfactant proteins-ii and -B leve ls, consistent with a concurrent increase in alveolocapillary permeabi lity.