One of the putative advantages of HFOV is that, in contrast to CV, it facilitates expansion of alveoli without increasing surfactant turnover. There are, however, few available data examining the surfactant status in infants ventilated with HFOV, and none focusing on the surfactant status of infants during conversion from HFOV to CV as lung disease is improving. We measured surfactant indices in two samples of tracheal aspirate (TA) fluid in six infants with lung disease (1 day to 2 mths). The first sample was taken 58±23 hours (mean±SEM) after commencing HFOV, and the second 49±5 hours later, 10±2.6 hours after conversion to CV. As a control group, TA samples were also taken from 8 healthy infants (median age 1.5 mths) immediately after endotracheal intubation, prior to elective surgery. Total phospholipid (PL), disaturated phosphatidylcholine (DSPC) and surfactant protein A (SP-A) were measured in the TA fluid, and secretory component of IgA (SC) was assayed as a marker of dilution. Geometric mean values for surfactant indices in the HFOV and CV samples were compared with each other using a paired t-test, and with controls using a t-test for independent samples. RESULTS: Conversion from HFOV to CV was associated with an 10-fold increase in the total amount of surfactant phospholipid in lavage fluid, but the proportion of DSPC was significantly diminished (seetable). The SP-A concentration was also significantly higher in the CV samples. There was no statistically significant difference between either of the groups compared to controls. CONCLUSIONS: Change from HFOV to CV is associated with an increased alveolar concentration of surfactant with a low DSPC/PL ratio. This is the converse of what would be expected during lung recovery, and may be accounted for by increased surfactant turnover related to the reinstitution of CV.

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