Effects of Ventilation Style on Surfactant Treatment Response in Premature Lambs. † 910

Effects of ventilation style on long term responses to surfactant have not been studied in the surfactant treated preterm. Preterm lambs were delivered at 130±1 d gestation (term 150 d) and treated with 100 mg/kg lipid extracted sheep surfactant. Three styles of ventilation that are at the extremes of clinical practice were used: (L) low rate of 15 breath/min, tidal volume 13 ml/kg; (H) high rate of 50 breath/min, tidal volume 8 ml/kg; (HFV) Sensomedics 3100 high frequency ventilation. Normal blood gas values(PCO₂ 45-50 mmHg) were achieved for all animals. Groups of 4 to 6 lambs(total N=60) were killed at 2, 5, 10 and 24h to recover alveolar wash (AW) and lung tissue for biochemical analysis. Mean airway pressure (MAP, cmH₂O), dynamic compliance (Comp. ml/cmH₂O·kg), functional residual capacity (FRC, ml/kg), lung volume at 40 cmH₂O(V₄₀, ml/kg),% functional large aggregate surfactant (%L) in AW, total protein in AW (protein, mg/kg) at 24h of age are in the table.

Table 1

Lung hyaluronan contents were similar between the 3 ventilation groups, and increased with age (2h:44±1μg/g lung tissue, 5h:50±1, 10h:68±1, 24h:90±2 2,5<10<24h p<0.05). Surfactant pool size saturated phosphatidylcholine in AW changed with time from 20±1μmol/kg at 2h to 10±1 at 24h, but there were no differences between the 3 ventilation groups. Although there are differences in MAP, Comp, FRC between groups, surfactant treated preterm lambs had similar surfactant variables and respiratory outcomes without indications of lung injury after ventilation for 24h with the 3 different styles of ventilation.