Pulmonary hypoxic hypertension is a condition associated with high pressure in the blood vessels of the lungs, caused by a shortage of oxygen in the body (hypoxia). It is a type of group 3 pulmonary hypertension, as defined by the World Health Organization (WHO).
What is pulmonary hypoxic hypertension?
To ensure that oxygen transfer from the lungs to the blood is as efficient as possible, the body redirects blood flow toward areas of the lungs with more oxygen. In areas with low oxygen, a process called hypoxic pulmonary vasoconstriction is triggered. This causes the blood vessels to narrow, restricting blood flow and encouraging it to go through the blood vessels in the oxygen-rich areas of the lungs. This “vascular remodeling” is normally a fast and dynamic response to changes in oxygen levels.
However, when there is a chronic lack of oxygen or hypoxia, this can stimulate more widespread vasoconstriction in the blood vessels of the lungs. This makes it more difficult for the blood to move through the lungs, increasing blood pressure and putting the heart under increased strain to pump the blood through the lungs.
Chronic hypoxia also can trigger inflammation and damage to the blood vessels. This can lead to scarring, which narrows and stiffens the blood vessels and increases the blood pressure even more.
Causes of pulmonary hypoxic hypertension include various lung diseases, such as chronic obstructive pulmonary disease (COPD) and diffuse parenchymal lung disease (DPLD), or repeated exposure to high altitudes.
Symptoms of pulmonary hypoxic hypertension
The symptoms of pulmonary hypoxic hypertension are similar to the symptoms of other types of pulmonary hypertension and include shortness of breath (dyspnea), fatigue, dizziness or fainting spells, chest pain, swelling of the legs and ankles (edema), blue-colored lips and skin (cyanosis), and irregular heartbeat.
Diagnosis of pulmonary hypoxic hypertension
To diagnose pulmonary hypoxic hypertension, the patient’s medical and family history will be taken, along with a physical exam to assess the symptoms. Multiple medical tests will be carried out to diagnose this and other forms of pulmonary hypertension.
The key tests for a diagnosis of pulmonary hypoxic hypertension will involve:
- Echocardiography and other imaging tests to identify abnormalities in the lungs and heart, and to estimate blood flow through.
- Right heart catheterization, to measure blood pressure in the blood vessels of the lungs.
- Lung function tests to detect how efficiently oxygen is being transferred from the lungs to the blood, and to determine the volume and speed of air flow into the lungs. This also can help identify lung disease in the patient.
Treating pulmonary hypoxic hypertension
There are no therapies specifically for pulmonary hypoxic hypertension. Treatment is focused mainly on the underlying cause of the condition. For example, long-term oxygen therapy (LTOT) frequently is used to treat COPD and can reduce the symptoms of pulmonary hypoxic hypertension.
Alternatively, general pulmonary hypertension therapies can be used. These include anticoagulants, to prevent blood clots, and diuretics, to reduce swelling. Other treatments include calcium channel blockers and prostacyclins, which act to relax and open up blood vessels.
In extreme cases, a patient may be recommended for a lung transplant.
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