HIGH-FREQUENCY OSCILLATORY VENTILATION IN NEONATAL RDS - INITIAL VOLUME OPTIMIZATION AND RESPIRATORY MECHANICS

To determine whether initial lung volume optimization influences respi ratory mechanics, which could indicate the achievement of optimal volu me, we studied 17 premature infants with respiratory distress syndrome (RDS) assisted by high-frequency oscillatory ventilation. The continu ous distending pressure (CDP) was increased stepwise from 6-8 cmH(2)O up to optimal CDP (OCDP), i.e., that allowing good oxygenation with th e lowest inspired O-2 fraction. Respiratory system compliance (Crs) an d resistance were concomitantly measured. Mean OCDP was 16.5 +/- 1.2 c mH(2)O. Inspired O-2 fraction could be reduced from an initial level o f 0.73 +/- 0.17 to 0.33 +/- 0.07. However, Crs (0.45 +/- 0.14 ml cmH(2 )O(-1).kg(-1) at starting CDP point) remained unchanged through lung v olume optimization but appeared inversely related to OCDP. Similarly, respiratory system resistance was not affected. We conclude that there is a marked dissociation between oxygenation improvement and Crs prof ile during the initial phase of lung recruitment by early high-frequen cy oscillatory ventilation in infants with RDS. Thus optimal lung volu me cannot be defined by serial Crs measurement. At the most, low initi al Crs suggests that higher CDP will be needed.