<p>Preterm newborn lambs were resuscitated after birth with (A) high peak inspiratory pressure (PIP) to regulate (C) tidal volume (V<sub>T</sub>) at 6 ml/kg. CHF5633, Survanta, or Air was given at 15 min of age and ventilation was changed to regulate (B) Pco<sub>2</sub> at 50–60 mmHg. Lung immaturity was comparable between the groups and all the control (Air) lambs died within 90 min of age. PIP and Pco<sub>2</sub> were similarly improved by treatment with CHF5633 and Survanta. Initial response of V<sub>T</sub> to surfactant treatment was faster by CHF5633 than Survanta. *p<0.03. Some error bars are within symbols.</p
