Immediate improvement in lung volume after exogenous surfactant: Alveolar recruitment versus increased distention

To determine whether changes in lung volume may be responsible for the clinical improvement in preterm infants given exogenous surfactant, we measured functional residual capacity (FRC), lung mechanics, and partial pressure of oxygen in seven ventilated neonates (birth weight 1080±361 gm (mean ± SD); gestational age 28.3±2.6 weeks) less than 9 hours of age who had findings typical of hyaline membrane disease. All patients received 100 mg/kg calf lung surfactant extract. FRC was measured by a closed-circuit helium-dilution technique, and lung mechanics were determined by least mean squares analysis, FRC increased in all patients (range 56% to 330%; p