PULMONARY SURFACTANT CONCENTRATION DURING TRANSITION FROM HIGH-FREQUENCY OSCILLATION TO CONVENTIONAL MECHANICAL VENTILATION

Objective: To test the hypothesis that conventional mechanical ventila tion (CV) provides a greater stimulus to secretion of pulmonary surfac tant than high frequency oscillatory ventilation (HFO). Methodology: S equential examination of surfactant indices in lung lavage fluid in a group of six infants with severe lung disease (group 1), ventilated wi th HFO and then converted back to CV as their lung disease recovered. A similar group of 10 infants (group 2) ventilated conventionally thro ughout the course of their illness were studied for comparison. In gro ups 1 and 2, two sequential tracheal aspirate samples were taken, the first once lung disease was noted to be improving, and the second 48-7 2 h later. Group 1 infants had converted from HFO to CV during this ti me. Results: A marked increase in concentration of total surfactant ph ospholipid (PL) and disaturated phosphatidylcholine (DSPC) was seen in group 1 after transition from HFO to CV; the magnitude of this increa se was significantly greater than that sequentially observed in group II (total FL: 9.4-fold increase in group 1 vs 1.8-fold in group 2, P=0 .006; DSPC: group 1 6.4-fold increase vs, group 21.7-fold, P=0.02). Co nclusion: These findings suggest that intermittent lung inflation duri ng CV produces more secretion of surfactant phospholipid than continuo us alveolar distension on HFO, and raise the possibility that conserva tion and additional maturation of surfactant elements may occur when t he injured lung is ventilated with HFO.