Persistent pulmonary hypertension of the newborn, also known as PPHN, is defined as ongoing high blood pressure within the pulmonary artery. Normally, the pulmonary artery transports blood from the right side of the heart to the lungs, where carbon dioxide in the blood is exchanged for oxygen. This oxygen-rich blood then returns to the heart, which pumps it out to the rest of the body. PPHN occurs when a birth defect or disease prevents the flow of blood from the heart into the lungs. Symptoms of PPHN include rapid breathing, rapid heart rate and respiratory distress. PPHN is a medical emergency, which can lead to shock, heart failure, multiple organ damage and death.
Patent Ductus Arteriosus
Prior to birth, the placenta supplies a baby with the oxygen it needs through the umbilical cord. During this time, the pulmonary artery bypasses the lungs, sending the blood back to the heart through a fetal blood vessel called the ductus arteriosus. Shortly after birth, the ductus closes and the pulmonary artery begins sending blood through to the lungs. Some infants are born with a heart defect called patent ductus arteriosus (PDA) in which the ductus arteriosus remains open, allowing blood flow to continue to bypass the lungs. This bypassing of the lungs increases the blood pressure in the lung arteries, resulting in PPHN. Patent ductus arteriosus can be treated with medications, cardiac catheterization or surgery. Some PDAs are small and will close over time without treatment.
Meconium Aspiration Syndrome
According to The Merck Manuals, meconium is stool formed in an infant's intestines prior to birth. Normally, newborns begin to pass meconium once they start to feed. Occasionally, stress can cause a fetus to stool into the amniotic sac while still in utero. This meconium is then caught in the amniotic fluid within the sac where it can be inhaled by the fetus into the lungs. After birth, the inhaled meconium can cause PPHN by clogging up the lungs, thus preventing the blood vessels from dilating properly. Infants thought to have meconium aspiration syndrome at birth will receive deep suctioning using a device called a meconium aspirator to try and remove meconium from the trachea, thus preventing any further aspiration. Infants with this disease usually require supplemental oxygen or mechanical ventilation and must be monitored closely for the development of complications such as PPHN.
Diaphragmatic Hernia
Diaphragmatic hernia is a birth defect in which an opening forms in the diaphragm during fetal development. This opening, typically found on the left side of the diaphragm, allows the abdominal organs to move up into the chest cavity. Once there, these organs will hinder the growth of the lung on the affected side, stopping it from developing properly. Infants with diaphragmatic hernia will develop severe respiratory distress shortly after birth, which can lead to lung collapse and the development of PPHN. Treatment of diaphragmatic hernia consists of abdominal surgery to close the opening in the diaphragm and return the abdominal organs to the abdominal cavity.
