Mechanical properties of fetal minipig lungs after substitution of surfactant with fluorocarbon and dipalmitoylphosphatidylcholine.

Respiratory distress syndrome (RDS) is characterized by quantitative and qualitative disturbances of surface active substances (surfactant). Therefore, intratracheal surfactant substitution is a favored subject of clinical investigations. In our study we tried to inflate and stabilize lungs in two steps: first, lungs were rinsed with a fluorocarbon and, second, artificially ventilated with a dipalmitoylphosphatidylcholine (DPPC) aerosol, the mean component of surfactant. Sixteen isolated fetal minipig lungs of day 95 (85% of the total gestation period) were used. From one pair of lungs one lung served as control (group 1), whereas the other was treated with DPPC (group II). In both groups the lungs were rinsed first with a fluorocarbon (FC-72, surface tension 12 mN/m). This maneuver was followed by an artificial ventilation with an aerosol of either salt solution (group I) or DPPC (group II) for 40 min. To characterize lung mechanics, static pressure volume curves were registered at 0, 20, and 40 min after fluorocarbon lavage. Airway opening pressure (pi), end-inspiratory volume (vi), and weight-specific end-inspiratory lung compliance (ci) were investigated. As biochemical parameters of the lungs we determined phospholipidphosphate content and DPPC, sphingomyelin (SM), and lysophosphaditylcholine (LPC) of the lung tissue. Significant differences were found with regard to phospholipidphosphate and DPPC content. No difference was seen in static pressure volume diagrams at the end of the investigation period.