Effect of Positive End-Expiratory Pressure (PEEP) on Premature Lamb Lungs Treated with Recombinant SP-C Surfactant

Abstract 1242 Neonatal Disease Oriented Research: Ductus and Surfactant Platform, Sunday, 5/2

Surfactants that contain only SP-B or SP-C were reported previously to be relatively ineffective when evaluated in surfactant deficient premature rabbits that were ventilated for 15 min without PEEP. We recently showed that a new synthetic surfactant (provided by Byk Gulden) containing 2% recombinant surfactant protein C (rSP-C) in phospholipids (DPC+PG) and 5% Palmitic acid, was as effective as natural surfactant when given to premature lambs ventilated with 3cmH₂O PEEP (Am.J.Resp.Crit.Care Med., 1998).

In this study, the effect of different levels of PEEP on the function of rSP-C surfactant and treatment responses were evaluated in preterm lambs (n=21). Lambs at 126d GA were delivered by C-section, treated with 100 mg/kg rSP-C surfactant containing ³H-DPC followed by ventilation with 0, 4 and 7 cmH₂O PEEP. Over a 7 h study period, the use of PEEP significantly improved lung function as indicated by decreased ventilatory pressures, (cmH₂O, Vent.P.); increased dynamic compliances, (ml/kg·cmH₂O, Comp.) and ventilation efficiency indexes (VEI) (Table). Lung volumes, (ml/kg at 40 cmH₂O, V40) from pressure-volume curves were significantly higher for PEEP-7 and PEEP-4 than for PEEP-0. Extracellular surfactant metabolism was altered with lower recovery of saturated phosphatidylcholine, µmol/kg (Sat PC) in alveolar lavage for the PEEP-0 than PEEP-7; % of large-aggregate surfactant forms (%LA) were strikingly lower for PEEP-0 than for the other groups and % recovery of ³H-DPC after 7h ventilation was lower for 0 and 4-PEEP than PEEP-7. The effect of PEEP-0 was also studied in five additional lambs treated with sheep natural surfactant (O-Nat). The adverse effects of 0-PEEP on lung injury and extracellular metabolism of surfactant were less evident for natural surfactant than for rSP-C surfactant. Total protein in alveolar washes was 2 times higher and %LA recover was lower for rSP-C surfactant. Premature lambs treated with rSP-C surfactant had a poor response and altered surfactant metabolism when ventilated without PEEP. Surfactant treatment responses and metabolism are altered by the PEEP chosen for the ventilation of surfactant treated preterm animals.

Table 1 No caption

Funded by Grant HD-12714