Background
The Doppler effect has allowed the characterization of several vessels in maternal-fetal circulation that have been used for practical purposes. Our review of the literature showed a paucity of information about fetal pulmonary artery pressure (FMPAP) and its behavior in regard to gestational age (GA). The objectives of the study were to evaluate a formula to calculate the main FMPAP and its correlation with GA.
Methods
A total of 337 fetuses without obvious pathology were studied prospectively using Doppler evaluation of the FMPAP. Using the fetal main pulmonary artery Doppler acceleration time (FMPAT), we obtained the FMPAP using the following formula: FMPAP=90 – (0.62×FMPAT). Regression analyses, Pearson’s bivariate correlation and paired sample t-test were used when appropriate.
Results
FMPAT increases while FMPAP decreases with GA. Pearson’s correlation coefficient for FMPAP and GA was −0.544 (P-value<0.001) and for FMPAT and GA was 0.556 (P-value<0.001). FMPAP and FMPAT were highly correlated (R=−0.972; P<0.001).
Conclusion
Pulmonary artery pressure in the fetus decreases with GA.
Extreme prematurity remains one of the leading causes of neonatal death. An ex-utero treatment strategy that allows the fetus to develop beyond this period until capable of tolerating the transition to post-natal physiology would significantly impact the quality of care offered for this pre-viable patient population. In this study, we report our experience with an ex-utero support system for fetal pigs with the goal of support and survival for eight hours. Our experiment included two pigs at a gestational age equivalent to a 32-week human fetus. Following ultrasound assessment and delivery via hysterotomy, the fetuses were transferred to a 40 L glass aquarium filled with warmed lactated Ringer's solution and connected to an arteriovenous (AV) circuit that included a centrifugal pump and a pediatric oxygenator. Fetus 1 was successfully cannulated and survived for seven hours (expected maximum duration of eight hours). Fetus 2 died shortly after hysterotomy, secondary to failure at the cannulation stage. Our results suggest that ex-utero support of the premature fetal pig is feasible, contributing to a scarce body of evidence. However, further studies are needed before effectively translating an artificial placenta system into the clinical arena.
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