Objective: 

The aim of the study was to prove the hypothesis that fibrinogen protects pulmonary surfactant against inactivation by surface area cycling.

Methods: 

Natural modified surfactant Curosurf was mixed with fibrinogen (ratio 2:1) and subjected to long-term surface area cycling at 37°C. Minimum and maximum surface tension (gamamin and gamamax) of samples at 6, 9 and 12 days of cycling were evaluated by captive bubble surfactometer. Immature newborn rabbits were treated intratracheally with Curosurf. Curosurf was cycled for 6 days without (CuroCyc) or with fibrinogen (CuroCycFib). In controls, no material was instilled. Animals were ventilated with 100% O2. Tidal volume (VT) and lung-thorax compliance (CLT) were recorded. Post mortem lung gas volumes and alveolar expansion were evaluated.

Results: 

Surface properties of surfactant cycled at 10 mg/ml were not influenced by fibrinogen. At 80 mg/ml, surfactant cycled without fibrinogen for 6 days did not reach gamamin<5 mN/m. CuroCycFib had low gamamin comparable with non-cycled Curosurf. Moreover, addition of fibrinogen prevented lipid peroxidation of Curosurf. In vivo, values of VT and CLT in CuroCyc animals did not differ from non-treated controls. Animals receiving Curosurf and CuroCycFib had significantly higher VT and CLT than controls. Lung gas volumes in CuroCyc, but not in CuroCycFib group, were significantly lower than in Curosurf group.

Conclusions: 

Effect of fibrinogen on pulmonary surfactant cycled at 37 °C depends on phospholipids (PLs) concentration. At high PLs concentration used in clinical practice fibrinogen has protective effect on natural modified surfactant subjected to long-term surface area cycling.

First author is supported by Center of Excellence for Perinatological Research No.26220120036 co-financed from EU-sources.