Pediatric researchers created a unique device that imitates the environment inside the wound. This revolutionary device could potentially alter care for very premature infants, by imitating the fluid-filled environment to permit the smallest infant a few extra weeks to develop their lungs and other organs.
A team of researchers led by Alan W. Flake M.D. tested and monitored extra-uterine support device’s effects on fetal lambs, where prenatal lung development is equivalent to that existing in humans.
The state-of-the-art system utilizes a very unique fluid-filled container that is attached to a custom-designed machine, which provides physiologic support. The fetal lambs mature in an environment that is near sterile and temperature-controlled, breathing amniotic fluid as they generally do in the would, their hearts pumped blood via their umbilical cord into what is known as a gas exchange machine located outside the bag. Meanwhile, electronic monitors measured blood flow, vital signs and other vital functions.
From one in ten births in the United States that are diagnosed as premature, younger than 37 weeks gestational age, an estimated 30,000 each year are critically premature or younger than 26 weeks gestational age. In the United States, extreme prematurity is the leading cause of infant morbidity and mortality, accounting for one-half of all cases of cerebral palsy associated with preterm birth.
Over the years, neonatal care standards have greatly improved the overall survival of preemies and nudged the limits of viability from 22 weeks to 23 weeks of gestation, at which time the newborn weighs less than 600 grams or a little more than a pound, with a 30 to 50 percent survival rate. However, this survival will be costly as far as the quality of life goes, because there is a high 90 percent risk of morbidity associated with chronic lung disease and other immature organs. The survivors will face lifelong disability.
The researchers describe development of their system over a three-year period through a sequence of four separate prototypes, starting with a glass incubator tank, moving forward to the present device. In the most recent prototype, the eight premature lambs tested were physiologically identical to a 23-week-gestation or 24-week gestation human baby.
The innovative system imitates life in the wound as closely as possible, building on the knowledge gathered from earlier neonatal research. Since even the slightest artificial pressure could potentially be a fatal overload for an underdeveloped heart, there is no external pump to drive circulation. A ventilator is also eliminated, because the premature lungs are not yet ready to breathe on their own in atmospheric oxygen. Instead, infant’s heart pumps blood through the umbilical cord into the extra-uterine support system’s low-resistance external oxygenator, which replaces the mother’s placenta in exchanging carbon dioxide and oxygen.
Also, the amniotic fluid developed in the lab flows into and out of the bag. The sterile environment is sealed inside the system, which is insulated from variants in pressure, light and pressure and especially from dangerous infections.
In previous studies, researchers examined versions of an artificial placenta in animal models. However, the results were disheartening, because the pumpless systems utilized in the studies were only able to achieve a maximum duration of 60 hours and the animals sustained brain damage. The current system is strikingly different in that it has operated up to 28 days or 670 hours with some animals that remained healthy. The fetal lambs demonstrated normal swallowing and breathing, grew wool, opened their eyes, had normal growth, became more active, organ maturation and neurological function.
The research from the Children’s Hospital of Philadelphia (CHOP) consisted of fetal medicine specialists, neonatologists, perfusionists, respiratory therapists and others. Emily Partridge, MD, PhD and CHOP research fellow came up with the initial impetus for the program. The team will continue to assess and improve the system, plus it will need to be downsized for human babies, since they are only one-third the size of the fetal lambs utilized in the new study.
The study was published in the journal Nature Communications on March 2, 2017 and published online April 25, 2017.