What is Altitude-Induced Pulmonary Hypertension?
Mountainous areas attract many people for adventurous trips, seasonal jobs, and even permanent living. Every year, over 40 million people visit high-altitude areas (more than 2500 meters), and around 140 million people permanently live in these regions. At high altitudes, the reduced air and oxygen pressure can significantly lower the amount of oxygen you breathe in, compared to sea level. This decrease in oxygen can trigger an intense reaction from your body if you ascend quickly, stay at high altitude for a long time, or persistently experience low oxygen content. These reactions can cause various health problems, which can range from mild to severe.
The different ways your body responds can result in several high-altitude related health conditions – from acute mountain sickness (AMS) to high-altitude pulmonary hypertension (HAPH). AMS can happen due to a quick climb and can feel like a hangover, with generic symptoms such as headache, nausea, dizziness, fatigue, and difficulty sleeping.
High Altitude Pulmonary Edema (HAPE) is a more severe form of acute mountain sickness, where the lungs fill with fluid due to the body’s difficulty acclimatizing. The most dangerous complication of altitude sickness, High Altitude Cerebral Edema (HACE), involves swelling of the brain, leading to neurological symptoms and consequences. Long-term exposure to low oxygen at high altitudes can cause irreversible changes in the lung’s blood vessels, leading to increased resistance and a condition known as HAPH, a type of pulmonary hypertension. This article will mostly discuss the causes, symptoms, and management of HAPH.
What Causes Altitude-Induced Pulmonary Hypertension?
When you are more than 2500 meters above sea level, the air pressure is lower, meaning there is less oxygen in the air. Even though the percentage of oxygen in the air stays the same at 21%, the actual amount of oxygen that gets into your lung’s air sacs, or alveoli, is much lower than at lower altitudes. This can cause a lack of oxygen in your body (hypoxia) and a low level of oxygen in your blood (hypoxemia).
This lack of oxygen triggers the blood vessels in your lungs to tighten, leading to an increase in pressure in the lung artery. This then may produce changes in the lung vessels due to factors such as abnormal muscle production, a decrease in the natural availability of nitric oxide (a molecule that helps blood vessels to relax), and genetic factors that aren’t fully understood yet. Together, these contribute to the development of high altitude pulmonary hypertension, which is an increase in blood pressure in the lungs due to high altitude.
Risk Factors and Frequency for Altitude-Induced Pulmonary Hypertension
Acute mountain sickness can affect some people when they’re at high altitudes, but high altitude pulmonary hypertension mainly develops in those who stay at high elevations for long periods. People who already have high blood pressure in the lungs are at an even higher risk for acute mountain sickness. This is because the low oxygen levels at high altitudes can make their already high lung blood pressure even worse.
However, there’s not a lot of information about which groups of people are most likely to get high altitude pulmonary hypertension. Some studies have shown that in South America, 18 to 55% of the population could have this condition, and it seems to be more common in men. On the other hand, there are fewer cases reported among women who haven’t gone through menopause and live at high altitudes. This difference could be because female hormones could increase the rate and drive of breathing.
Signs and Symptoms of Altitude-Induced Pulmonary Hypertension
High altitude pulmonary hypertension is a condition that has symptoms similar to other forms of pulmonary hypertension. You may experience one or more of the following symptoms if you have this condition:
- Shortness of breath during exercise
- Cough
- Coughing up blood
- Chest tightness
- Fatigue
- Swelling in the lower limbs
- Fainting episodes
Upon medical examination, signs of right-sided heart failure may be observed. These signs include a loud heart sound, right ventricular heave (a powerful beating of the heart you can feel with your hands on the chest), tricuspid regurgitation (backward flow of blood from the heart’s right ventricle into the right atrium), swollen jugular vein, swelling in the legs or other areas due to fluid buildup, and fluid buildup in the abdominal cavity.
All these signs are consequences of enlargement and failure of the right side of the heart. When examining patients suspected to have high altitude pulmonary hypertension, it’s crucial to look for signs and symptoms of other potential causes of pulmonary hypertension such as underlying autoimmune diseases, heart valve conditions, drug-induced pulmonary hypertension, and infectious diseases.
Testing for Altitude-Induced Pulmonary Hypertension
If you are having symptoms such as being short of breath, struggling to catch your breath, feeling unusually tired, or noticing swelling in your feet and legs, your doctor might want to check if you have heart problems or high altitude pulmonary hypertension. This last condition is a possible diagnosis if you live at a height of more than 2,500 meters above sea level.
The medical team will always want to rule out other health problems as well. As part of this process, you may undergo a series of tests, including an EKG, an echocardiogram, a chest X-ray, lung function tests, or a specific procedure to examine the right side of your heart and the flow of blood in your lungs using a special dye (right-sided heart catheterization with pulmonary angiography).
The EKG test can give signs of long-term strain on the right side of the heart with potential findings like an enlarged right ventricle, a specific type of irregular rhythm (right bundle branch block), and tall, sharp electrical waves seen with the heartbeat.
An echocardiogram can reveal if the right ventricle and right atrium of the heart are expanded and see if the pressure in the artery supplying the lungs is increased. It’s also crucial to examine the left side of your heart to rule out the possibility of left-sided heart failure.
The chest X-ray may be normal or could show an enlarged heart or signs of excess blood flow to the lungs. Lung function tests are essential to exclude other lung diseases such as chronic obstructive pulmonary disease (COPD), asthma, or other interstitial lung diseases that could be causing the symptoms.
The procedure involving the examination of the right-sided heart and blood flow mapping in the lungs is vital in diagnosing the condition conclusively. If the average pressure in the pulmonary artery or the peak pressure is abnormally high, this would be a sign of pulmonary hypertension. If possible, the test should be done at the same altitude where the patient resides.
Treatment Options for Altitude-Induced Pulmonary Hypertension
There isn’t a lot of currently available research to help guide the long-term treatment of high altitude pulmonary hypertension. However, some studies have suggested certain treatments usually used for other types of pulmonary hypertension can help improve symptoms and reduce pulmonary artery pressure.
If a patient has high altitude pulmonary hypertension, they’re usually advised to move to a location at a lower altitude. Research has indicated that when people do this, their pulmonary artery pressure can return to normal within two years.
There are several types of medications that can be used to treat high altitude pulmonary hypertension. Phosphodiesterase inhibitors like Sildenafil help widen the pulmonary arteries and lower pulmonary artery pressure. Carbonic anhydrase inhibitors like Acetazolamide can help prevent altitude sickness symptoms, and some studies have shown they can also help reduce the resistance in the pulmonary blood vessels. However, this particular medication hasn’t been specifically studied as a treatment for high altitude pulmonary hypertension, so the benefits might be limited. Yet, since it has a low side effect profile, it can be considered a safe treatment option. Another option is endothelin receptor blockers like Bosentan, which have also been used to treat pulmonary hypertension.
There’s some evidence to suggest that venovenous extracorporeal membrane oxygenation, or ECMO, could be helpful in severe cases in a short-term setting. If all other attempts at treatment are unsuccessful and a person develops irreversible pulmonary hypertension, the primary remaining treatment option would be a lung transplant.
What else can Altitude-Induced Pulmonary Hypertension be?
People with a condition called high altitude pulmonary hypertension typically experience symptoms like breathlessness during physical activity, tiredness, chest pain, and swelling in the arms and legs. There are also other conditions that can cause symptoms similar to high altitude pulmonary hypertension, which might include:
- Asthma
- Birth defects affecting the heart
- Diseases related to connective tissue
- Chronic obstructive pulmonary disease (COPD)
- Heart problems due to impaired relaxation (Diastolic dysfunction)
- Lung disease that damages the lung tissue (Interstitial lung disease)
- Heart problems due to impaired contraction (Systolic dysfunction)
It’s crucial for doctors to consider all these conditions when diagnosing and treating high altitude pulmonary hypertension.
What to expect with Altitude-Induced Pulmonary Hypertension
Recognizing and treating pulmonary hypertension (high blood pressure in the lungs) early on is very important for effectively managing the condition. The most common way of managing this long-term is by using treatments that lower the pressure in the lung arteries and support the right side of the heart, known as pulmonary vasodilators.
Even with the best medical care, some patients may still struggle with physical activity, and others may develop a permanent state of high blood pressure in the lungs, which might require a lung transplant. After undergoing a transplant, patients usually survive around 10.7 years on average. If the transplant isn’t successful, there are still other types of treatments and procedures that can help improve the power of the right side of the heart.
When it comes to pulmonary hypertension caused by living at high altitudes, there’s not a lot of long-term studies evaluating the condition’s prognosis. Some studies suggest that the pressure in the lung arteries may return to normal around two years after moving to lower altitudes. However, the pressure might increase again if the person returns to a high altitude.
Possible Complications When Diagnosed with Altitude-Induced Pulmonary Hypertension
The main problem faced by patients with this condition is difficulty with exercise. This issue is something most patients encounter, even if they are undergoing the best available treatments and therapies. This condition can also lead to serious complications such as the progression of the disease, failure of the right side of the heart, and even death.
Common Complications:
- Difficulty with exercise
- Progression of the disease
- Right heart failure
- Death
Preventing Altitude-Induced Pulmonary Hypertension
Teaching patients about their condition is crucial for handling lung high blood pressure effectively. The best chance for a good health outcome lies in taking the right medicines and sticking to the treatment plan. Healthcare providers should assist patients in setting realistic expectations about the results of their treatment. Some patients may still struggle with intense physical activity and may eventually need a lung transplant.
Patients suffering from lung high blood pressure due to high altitude should know that their condition can get better if they come back to lower altitudes. If they understand how their disease could progress and how severe it could become, convincing them to move to a lower altitude can considerably enhance their prognosis and quality of life.
