Abstract 1173 Neonatology: Clinical Investigation Platform, Monday, 5/3

Terms infants who have required HFOV to maintain gas exchange while awaiting lung transplantation have developed ventriculomegaly on cranial ultrasonography (HUS). To determine if this observation is unique to infants receiving HFOV, we retrospectively compared 39 HUS of 6 term neonates who required HFOV for more than 30 consecutive days (HFOV) with 20 HUS of 6 term neonates who required conventional mechanical ventilation for more than 30 consecutive days (CV). Each infant had 2 or more HUS at least one month apart. Using a coronal image at the level of the Foreman of Monro, we measured the ratio of the horizontal span of the lateral ventricles to the span of the cranial cavity. The ratios and ages of the first HUS did not differ (0.24 ± .07 vs. 0.28 ± .05, p = 0.31, at 21 ± 16 days vs. at 39 ± 40 days, p=0.20, HFOV vs. CV, respectively). The ratios on the last HUS were not significantly different (0.40 ±0.14 vs. 0.32 ± .06, p=0.13, HFOV and CV, respectively). However, the age of the HFOV group at the last HUS was significantly less than that of the CV group (76 ±29 vs. 128 ± 56 days, p=.03). To normalize the change in the ratios for time, we used regression analysis for all the HUS from each subject. The slopes of the individual regression equations were 1.5-25 fold greater for the HFOV group (mean [2.5 ± 1.0] × 10-3 vs. [6.5 ± 3.2] × 10-4, p= .005). The average mean airway pressure (MAP) during ventilation was slightly greater for the HFOV group (23 ± 3 vs. 17 ± 7 cm H2O, p=0.05). However, for the 4 CV infants with MAP > 15, the rate of ventricular enlargement was still significantly less than that of the HFOV infants (p=.005). We conclude that prolonged HFOV may promote the development of ventricular enlargement in neonates. We speculate that the consistently elevated mean airway pressure during HFOV interferes with cerebral venous drainage and impairs resorption of cerebrospinal fluid. Prospective studies of intracranial hemodynamics during HFOV will be necessary. (Figure)

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