Persistent Pulmonary Hypertension of the Newborn

Seen most often in term or post-term infants who have had a difficult birth, PPHN is a rare but life-threatening cardiopulmonary disorder wherein a newborn infant's system does not adapt to life outside of its mother's body.

When a fetus is still in the uterus, oxygen is acquired not through the lungs, but through the placenta. Because all of the fetal body's oxygen requirements are supplied through these means, blood pressure in the fetal lungs is high so that the circulation system actually bypasses the lungs, instead sending oxygenated blood directly from the placenta to other organs through a special blood vessel in the umbilical cord. When a baby is born and takes its first breath an automatic switch is meant to occur to allow the infant to survive outside the womb: blood pressure in the lungs is supposed to fall and that special umbilical blood vessel is supposed to permanently close up so that blood flow can directed through the lungs, allowing oxygen and carbon dioxide to be exchanged in a normal, non-fetal, fashion.

With PPHN, pressure within the lungs fails to fall and this switch cannot occur. With the pressure in the lungs remaining so high, the special umbilical blood vessel stays open and the baby's circulation system continues to bypass the lungs, attempting to maintain the prenatal circulation pattern even though the placenta is no longer there to provide desperately needed oxygen.

Seen most often in term or post-term infants, particularly in those who have had a difficult birth, the most common cause of PPHN is apparently Meconium Aspiration Syndrome (MAS), which itself affects less than one percent of neonates in the United States. According to an eMedicine article, thirteen percent of births are complicated by the presence of meconium in the amniotic fluid, but only five percent of those thirteen percent (approximately 0.65 percent of all births) will actually develop MAS. Some studies also indicate a higher rate of PPHN in infants born to mothers who took certain types of anti-depressant medications during pregnancy.

Treatment for PPHN involves the administration of supplemental oxygen and nitric oxide, and assisted ventilation with mechanical ventilators; additional drug therapy may also be used to assist in these treatments. Infants who suffer from Meconium Aspiration Syndrome in addition to PPHN may also require manual suctioning of the lungs to remove the accumulated meconium, and high-frequency oscillatory ventilation (with a ventilator machine attached to a vibrating platform which helps to shake congealed meconium loose, making it easier to suction the stuff out) if assisted ventilation is ineffective. If the infant also suffers from serious heart or lung failure, treatment with an extracorporeal membrane oxygenation (ECMO) machine, which adds oxygen to the blood outside of the infant's body and then pumps it back in, may be necessary. In addition, infants recovering from PPHN usually have problems feeding for several days or weeks, and often require a nasogastric feeding tube (a thin tube that is inserted through the nose and which runs down the throat and into the stomach) until they are able to begin breast or bottle-feeding on their own. While an infant is being treated, breathing rates, blood-oxygen levels and heart rate are all continuously monitored.

Long-term outcomes for babies with PPHN have improved significantly. When my son was still in the NICU, but on the road to recovery, the nurses explained to me that the new drugs and equipment available to help PPHN babies has made a huge difference in survival rates. They said that before these advances, babies with this disease just died. Even fifteen years ago, the death rate for infants with PPHN was apparently almost fifty percent, with long-term neurological damage resulting from oxygen deprivation reaching up to sixty percent. With the recent advances in treatments, these statistics have decreased to a ten percent mortality rate and a twenty percent rate of long-term damage, still very frightening numbers for a parent with a critically ill baby.

One of the most common long-term complications resulting from PPHN is sensorineural hearing loss. According to the audiologist who performed a hearing test on my son, infants who have suffered from PPHN have a thirty percent chance of developing degenerative hearing loss within the first two years of life, and the longer it takes an infant to recover from the disorder, the more likely it is that such hearing loss will occur. For this reason, several follow-up hearing tests for PPHN babies are normally recommended to ensure that any developing problems are diagnosed early.