Pulmonary hypertension refers to an abnormally elevated blood pressure within the pulmonary system.
The systemic circuit carries oxygenated blood from the left side of the heart to the organs and limbs. Then the blood comes back to the right side of the heart, where it is pumped through the pulmonary circuit to the lungs to become oxygenated and give off carbon dioxide. In this instance, the PH is caused by the emphysema. The cause is not known for sure, but some of the small arteries in the lung appear to become thick or blocked. Some cases of primary pulmonary hypertension are seen in families.