Pressure helps blood flow through blood vessels. Hypertension
occurs when this pressure gets too high. When this happens in
the blood vessels in the lungs, it is called pulmonary
hypertension. Pressure may rise for any number of reasons. It
creates a potentially serious condition. The right side of the
heart needs to pump harder to move blood against the pressure.
If left untreated, the right side of the heart can eventually
fail. The blood vessels in the lungs are very sensitive to
oxygen. The lower the level of oxygen, the narrower the vessels
become. Higher pressure will be needed to push blood through the
narrow blood vessels. Pressure will also increase when there is
more blood in the lungs than normal. There are many different
causes of pulmonary hypertension in children, such as: - Birth
defects that affect the heart (eg, septal defects , leaky heart
valves) - Deformity of the chest wall (pectus excavatum) -
Conditions like scleroderma , sickle cell disease , lupus , HIV
- Chronic lung disease - Blood