Abstract
Breathing during fetal life is periodic, it is inhibited by maternal/fetal hypoxia and it is stimulated by maternal/fetal hypercapnia. We use ECMO to study the influence of direct changes in blood gases or temperature on the fetus in 8 sheep at 125-130 days of gestation. For ECMO a 12 F silastic catheter (drainage, external jugular) and a 9.6 F catheter (return, carotid artery) were placed. Total blood flow varied between 60-80 ml/kg/min. After connection the fetuses were maintained normocapnic and hyperoxic (PaO2 63 ± 8 mmHg in carotid or axillary artery) for 8 to 19 hours to observe changes in breathing incidence or sleep cycling. Fetal PaCO2 was varied in 3 fetuses during fetal hyperoxia or normoxia. Fetal temperature was varied by decreasing blood temperature of the system (2 fetuses). 2 Fetuses were kept hyperoxic during maternal hypoxia. Preliminary observations: a) During fetal hyperoxia the fetuses continued to cycle between high and low voltage and fetal breathing showed in some cases a decrease in incidence, but overall it did not change significantly, b) During fetal hypercapnia (4-8 mmHg), fetal breathing was stimulated and it seemed to bear a relationship with oxygenation, c) During fetal hypothermia fetal breathing was stimulated, d) Fetal breathing was stopped when the ewe was made hypoxic and the fetus was kept hyperoxic, this suggests that during maternal/placental hypoxia a substance is produced which has a direct action on fetal breathing. ECMO proved to be a possible technique to study fetal physiology.
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Blanco, C., Banford, O., Hawkings, R. et al. 5 RESPONSES IN FETAL SHEEP TO CHANCES PRODUCED BY AN EXTRACORPOREAL MEMBRANE OXYGENATION SYSTEM (ECMO). Pediatr Res 24, 261 (1988). https://doi.org/10.1203/00006450-198808000-00031
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DOI: https://doi.org/10.1203/00006450-198808000-00031