Pulmonary Effects after Surfactant Treatment in Premature Infants with Severe Respiratory Distress Syndrome

Abstract

To understand the mechanisms behind the improved oxygenation after intratracheal surfactant instillation, the immediate effects on lung volume and pulmonary mechanics were analyzed. All infants studied were enrolled in multicenter trials in which surfactant therapy was instituted according to a rescue protocol. Infants received either synthetic surfactant (Exosurf) or modified porcine surfactant (Curosurf). Measurements of lung volume and pulmonary mechanics were successfully performed in 12 patients with a birth weight of 1.3 ± (SD) 0.6 (range 0.7-2.7) kg, and a gestational age of 28.3 ± (SD) 1.4 weeks. Functional residual capacity (FRC) and pulmonary mechanics were measured during mechanical ventilation. The FRC increased significantly by 70% (median), from 7.10 ± (SD) 2.8 ml/kg to 11.5 ± 3.3 ml/kg after surfactant instillation. However, a concomitant decrease in specific compliance was also seen. These findings could suggest that this immediate increase in FRC is initially nonuniform. However, since no significant correlation between changes in FRC and improvement in arterial-to-alveolar oxygen tension ratio is seen, other effects of surfactant must also be considered. These could include local and/or systemic changes in hemodynamics, such as decreased shunting as well as various effects on gas diffusion.

Functional residual capacity and compliance of the respiratory system after surfactant treatment in premature infants with severe respiratory distress syndrome

“…In contrast to animal studies [1,33,42], those in human neonates have failed to demonstrate early improvement of compliance [4,7,11,14,15,19,20,24]. Also in this study, statistical improvement in CRS was not found immediately after surfactant replacement.…”

“…The results from the present study regarding FRC and CRS in infants with severe RDS are comparable to those reported previously [11,16,19,20,24,39]. Our data confirm that infants with severe RDS have non-compliant [18,43], low volume lungs [24,26,32,43].…”

“…The infants in this study treated with natural surfactant preparations responded with improved oxygenation accompanied by an increase in FRC. According to the literature, onset and magnitude of the improvement in oxygenation and of the increase in FRC are different in the published studies [11,16,19,20,24,39]. The differences in the results of various studies could be due to differences in the infants (birth weight, gestational age, acidosis, PaO 2 before treatment, FiO 2 and age at time of treatment) investigated, the use of different measurement techniques for FRC and different surfactant preparations [8,11,19,20,24].…”

“…To our knowledge, there are only a few reports [11,16,19,20,24,39] describing the effect of surfactant treatment on lung volume only selective in a small number of mechanically ventilated preterm human infants.…”

Lung Function Tests in Neonates and Infants with Chronic Lung Disease of Infancy: Functional Residual Capacity

“…82 Increases in FRC pre-and post surfactant treatment are physiologically and clinically highly relevant. [85][86][87][88][89] Interestingly, the improvement in FRC is not paralleled by improved respiratory system compliance (C rs ), and sC rs may even decrease, prompting conclusions that surfactant primarily results in expiratory stabilization of previously aerated alveoli, followed by a slow improvement in C rs after recruitment of new alveoli. 85,[88][89][90] Results of these studies suggest that assessment of C rs (i.e., postsurfactant administration) should always be related to the actual FRC (sC rs ) to avoid misinterpretation.…”