Respiratory Support, Surface Activity and Protein Content during Nosocomial Infection in Preterm Neonates

Abstract

Small volume bronchoalveolar lavages from 10 infants (26.6 ± 0.4 weeks gestational age) during postnatal nosocomial infection were fractioned by differential centrifugation into large (LA) and small (SA) surfactant aggregates. Before deterioration of the clinical status, the surface tension at minimum bubble radius (γ_min), as measured in a pulsating bubble surfactometer, was reduced to about 14 mN/m by LA and to about 22 mN/m by the corresponding SA. The γ_min of both LA and SA increased during clinical deterioration, was highest at the worst clinical state and returned during recovery to values in the range before deterioration. Respiratory support significantly correlated to γ_min at all times. In contrast, no correlation was observed for total protein or albumin content of the LA or SA fractions. The SA fraction was characterized by a 10-fold higher protein content than LA. These data demonstrate functional impairment of surfactant in subfractions during mechanical ventilation and nosocomial infection in preterm neonates that are not fully explained by inhibition with increasing amounts of total protein.

Pulmonary surfactant in cystic fibrosis

“…Although the inhibition of surfactant by transudated plasma is an attractive hypothesis to explain surfactant dysfunction, unequivocal evidence for this, and if so, its precise quantitative contribution, remains to be established for pneumonia and nosocomial infection [17,21]. The data from this study do not support the view that surfactant inhibition in CF does play a major role, because when the water-soluble compounds were removed by lipid extraction, surface activity did not improve.…”

“…1). The SA fraction is much less surface active and usually contains the majority of the nonsurfactant-associated proteins [17], such as serum proteins or other water soluble inhibitors of surfactant function [18]. To determine whether a strong inhibitory component might contribute to a reduced surface activity in these CF patients, the effect of the SA-fraction at a protein concentration of 4 g·L -1 was tested against a natural, bovine surfactant at a concentration of 0.5 g·L -1 .…”

Reducing Atelectasis Attenuates Bacterial Growth and Translocation in Experimental Pneumonia

“…Although extrapolation of animal data to humans should be done with caution, we feel that this study might have important implications for the pathogenesis of ventilator-associated pneumonia. In many patients with acute respiratory failure, there is evidence for surfactant abnormalities leading to increased alveolar surface tension and subsequent atelectasis (48)(49)(50).…”

Pulmonary surfactant in health and human lung diseases: state of the art

“…There were no other changes in the phospholipid composition. The surface activity of the surfactant recovered in the LA fraction was reduced during the peak of infection and returned towards normal levels afterwards; a close correlation with respiratory support, expressed as the oxygenation index, was observed [143]. The impaired surface activity was not explained by leakage of serum proteins into the airspaces.…”