Surfactant replacement and open lung concept--comparison of two treatment strategies in an experimental model of neonatal ARDS

Abstract

Background: Several concepts of treatment in neonatal ARDS have been proposed in the last years. The present study compared the effects of open lung concept positive pressure ventilation (PPVOLC) with a conventional ventilation strategy combined with administration of two different surfactant preparations on lung function and surfactant homoeostasis.

Methods: After repeated whole-lung saline lavage, 16 newborn piglets were assigned to either PPVOLC (n = 5) or surfactant treatment under conventional PPV using a natural bovine (n = 5) or a monomeric protein B based surfactant (n = 6).

Results: Comprehensive monitoring showed each treatment strategy to improve gas exchange and lung function, although the effect on PaO2 and pulmonary compliance declined over the study period in the surfactant groups. The overall improvement of the ventilation efficiency index (VEI) was significantly greater in the PPVOLC group. Phospholipid and protein analyses of the bronchoalveolar lavage fluid showed significant alterations to surfactant homoeostasis in the PPVOLC group, whereas IL-10 and SP-C mRNA expression was tendentially increased in the surfactant groups.

Conclusion: The different treatment strategies applied could be shown to improve gas exchange and lung function in neonatal ARDS. To which extent differences in maintenance of lung function and surfactant homeostasis may lead to long-term consequences needs to be studied further.

Figure 1

Gas exchange(Pa_O2) and lung function (C_dyn). Time course of Pa_O2 (left panel) and dynamic compliance (C_dyn; right panel) over the observation period. Induction of lung injury by repetitive lavage procedures (T = 0) is followed by open lung concept positive pressure ventilation (PPVOLC; n = 5) or surfactant treatment under conventional positive pressure ventilation with a modified monomeric surfactant protein B surfactant (mon SP-B; n = 4) or a natural bovine surfactant (Alveofact^®; nat SF; n = 4). Results are given as mean and standard deviation.

Figure 2

Ventilation efficiency index (VEI). Left panel. Time course of ventilation efficiency index (VEI) over the observation period. Induction of lung injury by repetitive lavage procedures (T = 0) is followed by open lung concept positive pressure ventilation (PPV_OLC; n = 5) or surfactant treatment under conventional positive pressure ventilation with a natural bovine surfactant (Alveofact^®; nat SF; n = 4) or a modified monomeric surfactant protein B surfactant (mon SP-B; n = 4). Right panel. Difference of VEI over the study period (T5-T0). Study groups: open lung concept positive pressure ventilation (PPV_OLC; n = 5); surfactant treatment under conventional positive pressure ventilation with a modified monomeric surfactant protein B surfactant (mon SP-B; n = 4) or a natural bovine surfactant (Alveofact^®; nat SF; n = 4). Results are given as mean and standard deviation. * p < 0.05 vs PPV_OLC.

Figure 3

Histological sum scores (upper, middle and lower right lung lobe). Histologic sum scores (atelectasis, alveolar and interstitial inflammation, alveolar and interstitial hemorrhage, alveolar and interstitial edema, necrosis and overdistension) of upper, middle and lower right lung lobe using a four-point scale with no injury corresponding to 0 points and 4 points indicating maximum injury (A). Comparison of the groups showed no significant differences. Hematoxylin-eosin staining of exemplary histologic slides showing dystelectasis and neutrophiles in nearly all alveoli in the PPV_OLC group (B), regularly ventilated lung parenchyma in the monomeric SP-B group (C) and dystelectasis and neutrophiles in some of the alveoli in the natural SF group (D; hematoxylin-eosin, magnification 100×). Study groups: open lung concept positive pressure ventilation (PPV_OLC; n = 5); surfactant treatment under conventional positive pressure ventilation with a modified monomeric surfactant protein B surfactant (mon SP-B; n = 4) or a natural bovine surfactant (Alveofact^®; nat SF; n = 4). Results are given as mean and standard deviation.