Fetal lung liquid and fetal breathing play vital roles in fetal lung development. Current tracheal occlusion methods for treatment of congenital diaphragmatic hernia restrict the efflux of lung liquid and, therefore, the ability for fetal breathing. We hypothesised that tracheal occlusion with either balloon or hydrogel would increase transrespiratory pressure and decrease fetal breath rate. 

Diaphragmatic defects were surgically created in fetal lambs at 80d gestation (54% gestation; term ~150d) via hysterotomy. Tracheal occlusion was performed during a second hysterotomy at 100d (68% gestation) using either balloon (n=9) or methylcellulose hydrogel (n=10). A third unoccluded group served as a control (n=6). Continuous tracheal pressure measurements were obtained from a telemetric device placed during the occlusion procedure.

Tracheal occlusion (gel and balloon) increased transrespiratory pressure (p<0.05) from day 1 to 14 after occlusion compared to the untreated group. Fetal breathing increased (p<0.05) from day 1 to 14 in the untreated group, but not the occluded lambs. More breathing events were evident in the untreated lambs compared to the occluded lambs at day 14 (p<0.05). No differences were detected between the gel and the balloon groups of fetal lambs for any fetal breathing variable.

In conclusion, lambs with an untreated diaphragmatic hernia increased their fetal breathing frequency from ~100 to 114 days gestation. Tracheal occlusion during the early third trimester increases transrespiratory pressure and eliminates the increase in breath rate consequent to untreated diaphragmatic hernia. Balloon and gel pressure and fetal breathing are similar.