Protein content and biophysical properties of tracheal aspirates form neonates with respiratory failure.

BACKGROUND

We aimed at assessing the quality and quantity of protein-leakage across the alveolar-capillary membrane and its influence on surfactant function during the early neonatal period in preterm infants compared to newborns both with respiratory failure.

PATIENTS AND METHODS

We therefore prospectively analyzed total protein, elastase-alpha1-proteinase inhibitor complex (E-alpha1-PI) and alpha2-macroglobulin concentrations in tracheal aspirates from 31 infants < or = 32 weeks gestational age (group 1 : 29.3 +/- 2 weeks, 1214 +/- 410 g [means +/- SEM]) and from 21 neonates > 32 weeks (group 2 : 37.5 +/- 3 weeks, 2890 +/- 600 g [means +/- SEM]) and measured their surface activity in the pulsating bubble surfactometer.

RESULTS

Day 1 total protein and alpha2-macroglobulin levels indicated an initial high leakage that declined to day 3 in both groups (from 1652 +/- 241 to 708 +/- 227 mg/l; p < 0.05; resp. from 28 +/- 6 to 12 +/- 4 mg/l [means +/- SEM]). In group 2 E-alpha1-PI concentrations were significantly elevated at day 1 compared to group 1 (15 754 +/- 5766 versus 3320 +/- 1056 microg/l [means +/- SEM]). In both groups a high minimum surface tension (15 - 30 mN/m) was recorded from day 1 - 4.

CONCLUSIONS

These results suggest in larger newborns a secondary surfactant deficiency due to protein-leakage to play an important role in the pathogenesis of respiratory failure. The increased alveolar-capillary membrane permeability might be caused by inflammatory ARDS-like mechanisms.