Appropriate positive end expiratory pressure level in surfactant-treated preterm infants

Positive end expiratory pressure (PEEP) is routinely used when ventilating preterm infants, and high levels are recommended in those with severe respi ratory distress syndrome (RDS). Elevation of PEEP increases lung volume, as does surfactant administration. We postulated that in surfactant-treated i nfants even modest PEEP levels could result in overdistension and (CO2) ret ention. To test that hypothesis, lung volume, compliance and arterial blood gases were measured in eight preterm infants (median gestational age 28 we eks, range 26-35 weeks) at three PEEP levels. The infants, all with RDS. we re studied at a median time of 18 h, (range 12-68 h) after their last close of surfactant. Infants were routinely nursed at 3 cmH(2)O of PEEP, the PEE P level was then raised to 6 cmH(2)O or lowered to 0 cmH(2)O in random orde r. The new setting was maintained for 20 min: the PEEP level was then chang ed to the third level (0 or 6 cmH(2)O) again for 20 min. At the end of each 20-min period, lung volume, compliance and blood gases were measured. Lung volume was assessed by measuring functional residual capacity (FRC) using a helium dilution technique. Compliance was measured by relating the volume change from a positive pressure inflation maintained until no further volu me change occurred to the pressure drop (peak inflating pressure PEEP). Inc reasing PEEP from 0 to 3 cmH(2)O and particularly to 6 cmH(2)O resulted in increases in FRC (P < 0.05). oxygenation (ns) and paCO(2) (P < 0.02). Speci fic compliance (compliance/FRC) (P < 0.05) and pH (P < 0.02) fell. Conclusion Following surfactant treatment, relatively low levels of positiv e end expiratory pressure (less than or equal to 3 cmH(2)O) may be appropri ate.