An evaluation of the system to control blood flow in maintaining goat fetuses on arterio-venous extracorporeal membrane oxygenation: a novel approach to the development of an artificial placenta.

We compared various methods to control blood flow for extrauterine incubation of goat fetuses without lung respiration using arterio-venous extracorporeal membrane oxygenation via umbilical vessels to develop a suitable system for a long-term life support system for premature neonates. In twenty-seven consecutive preparations of goat fetuses, 4 designs (System 1, manual flow control without a reservoir; System 2, manual flow control with an arterial open-top reservoir; System 3, semiautomatic flow control with an arterial open top reservoir; and System 4, semiautomatic flow control with a tube occluder and an arterial open top reservoir) were tested in terms of the duration of incubation periods during which fetuses were kept under stable conditions. The incubation periods became prolonged with the advancement of the system (System 1, 5.4 h; System 2, 11.6 h; System 3, 64.8 h; and System 4, 159.8 h medians of the incubation periods). The incubation periods with System 4 were significantly longer compared to those with System 1 and System 2. These results suggest that, for extrauterine incubation of goat fetuses using arterio-venous extracorporeal membrane oxygenation via umbilical vessels, the method to control blood flow is of utmost importance for long-term maintenance, and thus a control system with the fixed vascular resistance of the extracorporeal circuit is applicable to long-term maintenance of premature goat fetuses.