Rapid improvement of static compliance after surfactant treatment in preterm infants with respiratory distress syndrome

Respiratory mechanics were measured in 20 preterm infants before and in the 24-hr period after treatment with surfactant. All infants were enrolled in the rescue clinical trial with Curosurf® carried out in the Neonatal Intensive Care Unit. They received a dose of 200 mg/kg lipid surfactant intratracheally after birth. Static compliance of the respiratory system (C_rs) was measured by the single breath occlusion technique during both spontaneous and mechanical ventilation. Resistance of the respiratory system (R_rs) and expiratory time constant (T_rs) were also measured. As early as 3 hr after surfactant administration a significant improvement of 45% in Crs measured during mechanical ventilation (C_rsV) was noted (0.40 ± 0.14 vs 0.58 ± 0.17 mL/cm H₂O/kg, P < 0.001), together with a significant improvement of the arterial/alveolar O₂ tension ratio (Pa/Ao₂) (0.12 ± 0.03 vs 0.30 ± 0.16. P < 0.01). The improvement of C_rsV and Pa/Ao₂ was confirmed 24 hr later (0.55 ± 0.15 mL/cm H₂O/kg and 0.33 ± 0.18, respectively). A significant correlation was found between C_rs and P_a/Ao₂ ratio (r = 0.56, P < 0.001). Time constant values were significantly higher after surfactant treatment (0.15 ± 0.07 vs 0.09 ± 0.03 sec; P < 0.01). R_rs remained unchanged. These data indicate that Curosuf® given intratracheally after birth determines a rapid improvement of respiratory mechanics as soon as 3 hr after dosing, together with the improvement of oxygenation. From the findings obtained with the present study we show evidence that respiratory system mechanics may be a useful physiological measure to guide ventilatory strategy following surfactant therapy. © 1993 Wiley-Liss, Inc.