Pulmonary hypoplasia refers to a condition where one or both of a baby’s lungs do not develop properly in the womb. Usually, the condition is secondary to another health problem that limits lung development. This not only affects the baby’s ability to breathe, but causes heart dysfunction, difficulty feeding, poor hearing and overall poor development.
Some children with pulmonary hypoplasia develop pulmonary hypertension, which refers to increased pressure in the pulmonary arteries. Eventually, the pressure causes the arteries to narrow, meaning the right side of the heart has to work harder to force blood through them.
The lung is made up of thin-walled structures called alveoli that enable gaseous exchange in the lung. They are supplied with blood by surrounding capillaries and veins. In the alveoli, gas is exchanged for gas in the blood, which enables the delivery of oxygen to tissues and the removal of carbon dioxide through exhalation.
In pulmonary hypoplasia, affected lungs are abnormally small and do not have enough alveoli available for gaseous exchange. If the hypoplasia is severe enough, the number of alveoli is critically low and adequate exchange of oxygen and carbon dioxide cannot be maintained. This means the baby is unable to breathe independently once born. Newborns with severe pulmonary hypoplasia die as a result of lung failure in the first few days of life if they cannot be supported long enough for them to develop new lung tissue.
The presentation of pulmonary hypoplasia varies depending on how severe the problem is. Some babies may simply breathe quickly, which is referred to as tachypnea. Others may show signs of severe respiratory failure including labored breathing, rapid breathing with the use of abdominal muscles, blue skin color (cyanosis) and gasping for oxygen. The baby’s blood carbon dioxide level will be high and their blood oxygen level will be low.
The main diagnostic factors for pulmonary hypoplasia include the following:
- History of fetal anomalies linked to the condition
- History of the mother not having enough amniotic fluid
- Medical imaging of the chest that reveals abnormally small lungs
Measurements taken from ultrasound and magnetic resonance imaging are used to assess lung volume and size to establish just how small the lungs are and whether the baby has a chance of survival or not.
The treatment approach to pulmonary hypoplasia depends on how small the baby’s lungs are and what has caused the condition in the first place. When the problem is a result of compressed lungs, then it is sometimes possible to remove the compression through intervention. In case of certain conditions, surgery can be performed on the fetus to resolve the problem while it is still in the womb.
Since there have been improved survival rates among babies with other pulmonary conditions in recent years, pulmonary hypoplasia has become increasingly important as a cause of neonatal death and morbidity. It is now the most common anomaly in babies who die in the neonatal phase.
Appropriate resuscitation of babies with this condition requires special attention and techniques.
Reviewed by Catherine Shaffer, M.Sc.