Positive end-expiratory pressure preserves surfactant function in preterm lambs.

Area of Science:

• Neonatal Physiology
• Respiratory Medicine
• Biophysics

Background:

• Ventilation strategies impact lung injury and surfactant function.
• Surfactant therapy is crucial for preterm infants.
• The role of positive end-expiratory pressure (PEEP) in surfactant dynamics needs further elucidation.

Purpose of the Study:

• To investigate the effects of varying PEEP levels on clinical outcomes.
• To assess the influence of PEEP on surfactant pools and biophysical activity in preterm lambs.
• To compare recombinant human surfactant protein C (rSP-C) with natural surfactant under different PEEP settings.

Main Methods:

• Preterm lambs (126-d gestation) were ventilated for 7 hours with tidal volumes of 10 ml/kg.
• Lambs received either rSP-C surfactant or natural sheep surfactant.
• Three PEEP levels (0, 4, and 7 cm H2O) were applied to rSP-C treated lambs; a zero PEEP group received natural surfactant.

Main Results:

• Physiological responses were comparable between rSP-C and natural surfactant groups at zero PEEP.
• PEEP levels of 4 and 7 cm H2O significantly improved oxygenation and lung compliance compared to zero PEEP.
• Maximal lung volumes doubled with PEEP 4 and 7; alveolar large-aggregate surfactant pools increased 3-4 fold, maintaining low surface tension.

Conclusions:

• PEEP improves lung function and oxygenation in surfactant-treated preterm lambs.
• Higher PEEP levels enhance the alveolar surfactant pool size and the proportion of large-aggregate surfactant.
• PEEP is effective in maintaining the biophysically active form of rSP-C surfactant in preterm lungs.