Objective: To analyze the impact of in utero tracheal occlusion (TO) on lung tissue blood perfusion, as measured by fractional moving blood volume (FMBV) and conventional spectral Doppler, in a rabbit model of congenital diaphragmatic hernia (CDH). Methods: In 50 fetal rabbits, a left CDH was surgically created at 23 days of gestational age (GA). At 28 days of GA, the surviving CDH fetuses were randomly assigned to undergo either TO (CDH+TO group) or a sham operation (CDH group). Twenty littermates, which were not operated on, served as internal normal controls. At 30 days of GA, lung perfusion estimated by FMBV and spectral Doppler of the proximal intrapulmonary artery were evaluated in the right lung during cesarean section. Doppler waveform analysis included the pulsatility index (PI), peak early diastolic reverse flow and peak systolic velocity. Results: Eleven CDH fetuses, 9 CDH+TO and 20 controls were suitable for the study. CDH fetuses showed a significantly higher PI [8.0 (SD 1.8) vs. 5.22 (SD 1.1), p < 0.001] and lower FMBV [13.5% (SD 4.6) vs. 23.0% (SD 2.1), p < 0.001] than the controls. In contrast, CDH+TO fetuses had a significantly lower PI [5.8 (SD 2.3) vs. 8.0 (SD 1.8), p = 0.015] and higher FMBV [27.6% (SD 7.1) vs. 13.5% (SD 4.6), p < 0.001] than CDH fetuses, with values similar to the controls. Peak early diastolic reverse flow and peak systolic velocity showed nonsignificant differences among the study groups. The lung to body weight ratio at necropsy correlated positively with lung FMBV (r = 0.60, p < 0.001) and negatively with the pulmonary artery PI (r = –0.48, p < 0.01). Conclusion: Tracheal occlusion is consistently associated with increased lung tissue perfusion and decreased intrapulmonary impedance in a rabbit model of CDH.

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