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06-08-2017

PE Bag Substitutes Mother's Womb

A Biobag Replicates the Size and Shape of the Uterus

Neonatal care practices have improved overall survival of premature infants and have pushed the limits of viability to 22 to 23 weeks of gestation. At that age an infant weighs below 600 grams — little more than a pound — and has a 30 to 50 percent chance of survival. But this survival comes at a high price in quality of life, with a 90 percent risk of morbidity, from chronic lung disease or other complications of organ immaturity. A unique womb-like environment could transform care for extremely premature babies, by mimicking the prenatal fluid-filled environment to give the tiniest newborns a precious few weeks to develop their lungs and other organs.

In animal studies, researchers from the Children's Hospital of Philadelphia (CHOP), PA/USA, have designed this fluid-filled environment to bridge the critical time from the mother’s womb to the outside world.

Study leader Alan W. Flake, MD, and colleagues report on preclinical studies of their extra-uterine support device in "Nature Communications". They tested and monitored effects on fetal lambs, in which prenatal lung development is very similar to that occurring in humans. The innovative system uses a unique fluid-filled container attached to custom-designed machines that provide physiologic support. The fetal lambs grow in a temperature-controlled, near-sterile environment, breathing amniotic fluid as they normally do in the womb, their hearts pumping blood through their umbilical cord into a gas exchange machine outside the bag. Electronic monitors measure vital signs, blood flow and other crucial functions.

The system mimics life in the uterus as closely as possible, building on knowledge from previous neonatal research. There is no external pump to drive circulation, because even gentle artificial pressure can fatally overload an underdeveloped heart, and there is no ventilator, because the immature lungs are not yet ready to do their work of breathing in atmospheric oxygen. Instead, the baby’s heart pumps blood via the umbilical cord into the system’s low-resistance external oxygenator that substitutes for the mother’s placenta in exchanging oxygen and carbon dioxide.

Left: Representative lamb cannulated at 107 days of gestation and on day 4 of support. Right: The same lamb on day 28 of support illustrating somatic growth and maturation (© Nature Communications 8: "An extra-uterine system to physiologically support the extreme premature lamb")

Left: Representative lamb cannulated at 107 days of gestation and on day 4 of support. Right: The same lamb on day 28 of support illustrating somatic growth and maturation (© Nature Communications 8: "An extra-uterine system to physiologically support the extreme premature lamb")

A Closed Sterile Fluid Environment

To address issues of sterility, size adaptability and efficiencies of space and fluid volume, a ‘Biobag’ design was developed − a single-use, completely closed system that minimizes amniotic fluid volumes and can be customized to more closely replicate the size and shape of the uterus.

The Biobag consists of polyethylene film that is translucent, sonolucent and flexible to permit monitoring, scanning and manipulation of the fetus as necessary. An open, sealable side was incorporated to facilitate insertion of the fetus at the time of cannulation, and various water-tight ports were designed to accommodate cannulas, temperature probes and sterile suction tubing. After cannulation, the Biobag is sealed and transferred to a mobile support platform that incorporates temperature and pressure regulation, padding and the fluid reservoirs and fluid exchange circuitry. The development of the Biobag essentially solved the problem of gross fluid contamination, and has eliminated pneumonia on lung pathology.

“Our system could prevent the severe morbidity suffered by extremely premature infants by potentially offering a medical technology that does not currently exist,” says study leader Alan W. Flake. The researchers will continue to evaluate and refine the system, and will need to downsize it for human infants, who are one-third the size of the infant lambs used in the current study. If their animal results translate into clinical care, Flake envisions that a decade from now, extremely premature infants would continue to develop in chambers filled with amniotic fluid, rather than lying in incubators, attached to ventilators.

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