Introduction. Early HFOV with an adequate alveolar recruitment is one of essentials of RDS management. Yet, no clear agreement exists on the initial modality of this intervention. We have evaluated the effects, including on static lung compliance (Crs), of an early strategy using a progressive LVO in newborns with RDS.

Methods. Thirty four premature infants (gestational age 30.4±1.8 weeks) requiring HFOV (SM 3100A) on admission were studied. The continuos distending pressure (CDP), starting at 6-8 cmH2O, was increased stepwise until optimal CDP (OCDP) defined as that providing a good oxygenation (O2 saturation 90-95%) with the lowest FiO2. CDPxFiO2 was used as an index of the severity of lung disease. Crs (single occlusion technique) was determined at OCDP in all patients and through LVO in 17.

Results. Mean OCDP was 14.8±3.5 cmH2O (< 12 cmH2O in 8/34), with an FiO2 ≤ 0.30 in 23/34. No lung overinflation was observed. Crs (0.5±15ml/cmH2O/kg) appeared inversely related to OCDPxFiO2 (r=-0.567, p<0.01). Antenatal steroids was associated with a lower OCDPxFiO2 (p<0.01), and a higher Crs (p=0.01). Crs was decreased in outborn patients (p<0.01). Most of them had been assisted by conventional ventilation prior to admission. In 17 patients examined at different time points of LVO, Crs remained unchanged despite a marked oxygenation improvement.

Conclusions. The progressive LVO strategy is safe and reliable. During the early phase of neonatal RDS, Crs reflects the severity of surfactant deficiency and is not influenced by LVO. Thus, optimal lung volume cannot be defined by serial Crs.