What Causes Pulmonary Hypertension?

Some people with COPD also have a condition called pulmonary hypertension (PH). This means that you have elevated blood pressure inside your lungs. So, what might cause a person to develop a PH? Here are three theories that researchers have developed.

What causes pulmonary hypertension?

Various conditions may cause PH. These include:^1-3

• Idiopathic: No known cause
• Genetic: It runs in your family.
• Drugs: It’s a side effect of some prescription or illegal drugs.
• Congenital: Some people are born with heart defects that may cause it.
• Left heart diseases. Examples include left-sided heart failure or diseases that affect the valves on the left side of your heart.
• Chronic lung diseases: These include cystic fibrosis, pulmonary fibrosis, and COPD.

We are a COPD community so our focus is on how COPD might lead to PH. Researchers are not 100% sure why COPD might lead to PH. However, they are aware that PH generally results in those with severe COPD. One study showed that 38% of those with severe COPD also had PH.³

Left and right heart

Consider this. The left side of your heart is called your left heart. It is responsible for pushing blood through your entire system. For this reason, it must be a powerful muscle - in fact, it is larger than your right heart. Normal systemic blood pressure is 120/80 mm Hg.⁴

The right side of your heart is called your right heart. It is responsible for pushing blood through your lungs. Your right heart is smaller than your left heart because there is a short distance from your heart to your lungs. The pressure your right heart needs to do its job is generally low. A normal resting pulmonary blood pressure is 25 mm Hg or less while a normal pressure during exercise is 30 mm Hg or less.¹

Usually, the first signs of PH in those with COPD occur during exercise. It may cause shortness of breath and chest tightness when you exert yourself. Although COPD itself may also explain these symptoms so this can complicate getting an early diagnosis for PH.⁶

Theories linking COPD to PH

Researchers are not exactly sure why COPD might cause PH, although they have devised three theories that may explain this phenomenon. These include loss of capillaries, inflammation, and hypoxia.

Loss of capillaries

 
This would be the result of severe emphysema which causes the breakdown of lung tissue. Alveoli break apart, as do the series of blood vessels (capillaries) that connect with them. Your right heart may have to generate a much stronger force to pump blood through the remaining capillaries over time.^1,5

Inflammation

Inhaling harmful substances like cigarette smoke does not cause COPD by itself. Your immune system attacks these chemicals by releasing inflammatory chemicals. After years of inhaling harmful substances, these inflammatory chemicals start to damage lung tissue and researchers think they may also be damaging to capillaries. They may cause capillary walls to become thicker than normal, making them narrow. To pump blood through constricted airways, your heart has to generate a greater force and this would cause your pulmonary blood pressure to increase.^1,5

Hypoxia

Hypoxia is a term meaning less oxygen is getting to your tissues. This may result from hypoxemia or low blood oxygen levels and also may result from less oxygen getting to your alveoli. This would be caused by severe narrowing of airways leading to alveoli which would occur in some areas of your lungs. These areas would therefore receive less oxygen - oxygenated blood (venous blood) in these areas would pick up very little oxygen.

Your body responds to this by constricting pulmonary blood vessels. This is done to shunt non-oxygenated blood away from poorly ventilated areas of your lungs and toward well-ventilated regions of your lungs. This is one mechanism your body uses to maintain normal oxygen levels and treatment for this would be home oxygen therapy. ^1-2,6

Living better and longer

These are three theories to help researchers explain links between COPD and PH. They involve very complex mechanisms but I have attempted to simplify them in this short post.

Keep in mind that most people with COPD will not develop PH. Still, it’s neat that researchers are looking to learn more about it for those who have this diagnosis. Researchers have developed strategies for helping doctors screen, diagnose, and treat it and this is all in the name of every person with COPD living better and longer despite their diagnosis.