What is Pulmonary Hypertension Due to Lung Disease or Hypoxia?
Pulmonary hypertension (PH) is a serious condition that gets worse with time. If it’s not treated, it can be fatal and cause the right side of the heart to fail. The 6th world symposium on pulmonary hypertension, which took place in 2019, said that PH happens when the average pressure in the pulmonary artery is more than 20 mmHg. In 2022, the European Society of Cardiology and European Respiratory Society updated their guidelines. They now label PH as pre-capillary PH if the resistance in the pulmonary vessels is more than 2 wood units and the pressure in the pulmonary vein is 15 or less. They label it as post-capillary PH if the pressure in the pulmonary vein is more than 15 mmHg.
Additionally, the World Health Organization (WHO) sorted PH into five groups based on differences in causes and treatment options. PH that occurs due to lung problems, because of chronic lung disease with or without a lack of oxygen in the blood, is in group 3. This discussion will be about the sources, spread, patient symptoms, doctor findings, evaluation and treatments of this condition.
Other types of pulmonary hypertension include pulmonary arterial hypertension (group 1), PH due to heart disease on the left side of the heart (group 2), PH due to chronic blood clots in the lung vessels (group 4), and PH from a range of other unrelated disorders (group 5). These will be discussed separately.
What Causes Pulmonary Hypertension Due to Lung Disease or Hypoxia?
Chronic obstructive pulmonary disease (COPD) and diffuse pulmonary lung disease (like idiopathic pulmonary fibrosis and combined pulmonary fibrosis and emphysema) are the main diseases that cause chronic low oxygen levels in the blood. They are also the ones most often connected with a condition called pulmonary hypertension, which is high blood pressure in the lungs’ blood vessels. Pulmonary hypertension can vary depending on how severe the lung disease is. People with COPD generally have mild to moderate pulmonary hypertension, but in severe cases of COPD, it can be quite severe. Pulmonary hypertension tends to worsen the symptoms of these diseases, making patients feel worse, need more oxygen, and have a worse overall health outcome.
Pulmonary hypertension can also show up in other diseases like cystic fibrosis, chronic hypersensitivity pneumonitis, lung cancer, and less common lung diseases like pulmonary Langerhans histiocytosis and lymphangioleiomyomatosis. How severe the pulmonary hypertension is often matches how severe the disease is and how much it has affected the lung tissue. It can also show up in developmental lung issues like bronchopulmonary dysplasia and congenital diaphragmatic hernia.
People living above 2500 meters, or around 8200 feet, above sea level may develop pulmonary hypertension due to low oxygen levels at these high altitudes. Obesity hypoventilation syndrome and overlap syndrome are reported to be associated more frequently with pulmonary hypertension than obstructive sleep apnea. The patients with these conditions typically have more severe pulmonary hypertension and their prognosis is generally poor since they typically experience worsening lung function and lower oxygen levels at night.
Risk Factors and Frequency for Pulmonary Hypertension Due to Lung Disease or Hypoxia
Pulmonary hypertension, otherwise known as PH, comes in different forms. Group 3 PH is associated with chronic lung diseases and a lack of oxygen, and is more common than Group 2 PH, which is caused by heart disease. The exact number of patients with chronic obstructive pulmonary disease (COPD) who have PH isn’t known, but it’s thought to be somewhere from 10-30% for those with mild to moderate levels of COPD. Severe COPD is more likely to involve PH, with about 90% of those at stage IV of the disease developing it.
PH is not only associated with COPD, but is also often found in patients with a condition called idiopathic pulmonary fibrosis (IPF). Prevalence rates for PH in IPF patients range from around 37-41% but this could potentially be higher as these results are mainly from patients evaluated for lung transplants with advanced IPF.
- Group 3 PH, associated with chronic lung diseases and low oxygen levels, is more common than Group 2 PH, linked to heart disease.
- While the exact number isn’t known, experts estimate that 10-30% of mild to moderate COPD patients have PH.
- About 90% of severe COPD patients (stage IV) are likely to experience PH.
- Pulmonary hypertension is a common occurrence in people with Idiopathic Pulmonary Fibrosis (IPF), with a prevalence rate of about 37-41%, potentially higher in patients with advanced IPF being evaluated for lung transplants.
Signs and Symptoms of Pulmonary Hypertension Due to Lung Disease or Hypoxia
Pulmonary hypertension often presents with symptoms that can be common to other underlying conditions. It is especially true for Group 3 Pulmonary Hypertension, which seems very similar to other groups because it shows signs of chronic lung disease and low oxygen levels during the day or nighttime. Difficulty breathing with no apparent cause is a common symptom but, according to medical experts, isn’t very specific to this condition. Other symptoms that are more predictive of pulmonary hypertension include fainting, dizziness, and heart palpitations.
However, the disease’s physical signs are not very specific and cannot provide an accurate picture of how the disease will progress. Conditions such as poor oxygen saturation, swelling of the neck veins, fluid retention in the body, accumulation of fluid in the abdominal cavity, altered heart sounds (especially loud P2 or S2), a forcefully contracting right ventricle, and signs of right-sided heart failure including an enlarged liver are helpful in diagnosing the disease but usually appear in its later stages.
- Chronic signs of lung disease
- Low oxygen levels during day or night
- Difficulty breathing with no apparent cause
- Fainting
- Dizziness
- Heart palpitations
- Poor oxygen saturation
- Neck vein swelling
- Fluid retention in the body
- Fluid accumulation in the abdominal cavity
- Altered heart sounds
- Forceful contraction of the right ventricle
- Signs of right-sided heart failure
- Enlarged liver.
Testing for Pulmonary Hypertension Due to Lung Disease or Hypoxia
When you’re getting a check-up for lung-related issues, doctors will often use several methods to pinpoint the problem. One of the tools that doctors use is pulmonary function tests, or PFTs. These tests can differentiate between problems with restrictions in lung movement and problems with obstruction in the airway.
The PFTs look at different aspects of your lungs’ function, including how well they can diffuse, or spread, carbon monoxide (DLCO). Some possible symptoms of pulmonary hypertension (PH), a type of high blood pressure that affects the arteries connected to your lungs, include a low DLCO, a DLCO that is decreasing quite quickly, and a DLCO that is disproportionate to lung volumes. This makes screening for these symptoms an effective way to detect the development of PH in patients with a disease known as advanced Idiopathic Pulmonary Fibrosis (IPF).
Beyond PFTs, a simple six-minute walk test (6MWT) and a check of the oxygen saturation levels in your blood can also provide your doctors with important insights. Factors such as a significant decrease in the distance walked in six minutes despite stable PFT results, the need for additional oxygen during exertion, and slow heart rate recovery following exercise could indicate an underlying presence of PH.
However, if a doctor strongly suspects a case of pulmonary hypertension, they might choose to use other screening methods like echo-cardiography or a test for Brain Natriuretic Peptide (BNP) or N-terminal-proBNP. Echo-cardiography uses sound waves to make pictures of your heart and is a crucial tool in diagnosing PH. It provides information about the pressure in the arteries connected to your heart and helps distinguish between pre-capillary and post-capillary hypertension. But results from echo-cardiography can sometimes incorrectly diagnose PH, especially in patients with chronic lung disease.
Apart from these, blood tests to check levels of BNP or N-terminal-pro-BNP can also help in diagnosing PH. Unlike most other tests, right heart catheterization (RHC), where a long, thin tube called a catheter is guided to the right side of the heart to measure pressure, is used as a gold standard for confirming a diagnosis of PH. It’s typically recommended in cases where symptoms don’t correlate with the severity of existing health concerns, when patients are considered for specific treatments, and when evaluating patient suitability for a lung transplant.
Lastly, chest computed tomography (CT) scans provide valuable insight into the status of conditions that cause lung damage or injury, like COPD and ILD, by showing detailed images of the lungs. This is especially valuable when symptoms seem to be more severe than what’s expected based on lung disease severity. However, they aren’t usually able to directly correlate lung scans with the presence or severity of PH.
Treatment Options for Pulmonary Hypertension Due to Lung Disease or Hypoxia
The purpose of treating group 3 pulmonary hypertension (PH) is to manage the underlying issue and improve the patient’s overall functionality. This goal can be achieved through medication, specifically bronchodilators for obstructive lung disease, antifibrotics for fibrotic lung disease, and immunosuppressants for connective tissue disease-induced lung disorders, to slow progression.
For patients with a condition called obesity hypoventilation syndrome, the use of non-invasive mechanical ventilation, like a CPAP machine, is encouraged. Studies have shown that regular use of such machines can improve lung function.
Patients with severe disease experiencing low oxygen levels can benefit from long-term oxygen therapy, particularly those with Chronic Obstructive Pulmonary Disease (COPD). The research shows that using oxygen therapy for more than 15 hours a day slows the progression of PH and improves pressure levels in the lungs if used for more than 18 hours. Although it’s not proven that oxygen therapy directly slows the progression of PH in pulmonary fibrosis, it’s commonly prescribed to prevent the worsening of PH due to sustained low oxygen levels.
Some treatments aimed at relaxing and widening blood vessels, known as systemic vasodilators, have raised concerns. These drugs might interfere with the body’s natural response to low oxygen levels, leading to imbalances in lung function. However, studies haven’t observed these effects in multiple trials with patients having lung disorders. Some specific vasodilators have shown no benefit and might even be harmful, and one was withdrawn from a trial early due to increased side effects and death.
One specific inhaled drug, Treprostinil, showed promising results in recent studies, where patients using it could walk further in six minutes than those given a placebo. These results suggest inhaled vasodilators may have fewer side effects than systemic ones. The US FDA has approved inhaled Treprostinil as a treatment for group 3 PH related to lung disorders.
If the patient’s condition continues to progress despite therapy, systemic vasodilators may be cautiously considered on an individual basis at specialized Pulmonary Hypertension centres. Similarly, patients with advanced lung disease should be evaluated for a potential lung transplant. This recommendation applies to patients with certain measures of lung function falling below specific thresholds.
What else can Pulmonary Hypertension Due to Lung Disease or Hypoxia be?
When doctors suspect a patient has group 3 pulmonary hypertension (PH), or high blood pressure in the lungs, they need to rule out other possible causes. These could include heart valve problems, chronic blood clotting problems, and infections. Identifying the primary cause of PH is crucial because it can change the treatment approach and possible outcomes.
Group 3 PH, which is related to lung diseases, can happen alongside group 1 PH, especially in cases involving connective tissues – ILD (interstitial lung disease). PH in these patients can come from a blend of low oxygen levels and other complications related to their disease. These patients should seek treatment from a center that specializes in PH for personalized care.
In some patients with group 3 lung disease, particularly ILD, both pre-capillary and post-capillary PH can occur simultaneously due to the common occurrence of coronary artery disease. This affects the small blood vessels before (pre-capillary) and after (post-capillary) they pass through the heart.
What to expect with Pulmonary Hypertension Due to Lung Disease or Hypoxia
Pulmonary hypertension linked to COPD often ranges from mild to moderate and is measured between 20 and 35 mmHg, increasing at less than 0.5 mmHg each year. However, about 5% of COPD patients have a severe increase in pulmonary hypertension with elevated artery pressures and poor blood flow reserves compared to the expected lung reserves based on their lung function test. The presence of pulmonary hypertension in individuals with COPD is a key indicator of survival rate, with higher levels leading to negative outcomes and increased chances of death.
Similarly, pulmonary hypertension linked to Idiopathic Pulmonary Fibrosis (IPF) is associated with worse health outcomes and reduced quality of life. People with IPF have a higher risk of death in the first year compared to those lung transplant patients without any pulmonary hypertension. In the case of combined pulmonary fibrosis and emphysema, patients develop severe pulmonary hypertension and have a worse outlook than those with IPF without emphysema.
Possible Complications When Diagnosed with Pulmonary Hypertension Due to Lung Disease or Hypoxia
When chronic lung disease goes untreated, it worsens over time, leading to high pressure in the lung’s primary artery due to a lack of oxygen. This extra pressure triggers the right side of the heart (right ventricle) to work harder to pump blood. To cope with this demand, the right ventricle slowly starts to thicken and enlarge. However, this change ultimately causes it to work less efficiently, leading to a communication breakdown between the right ventricle and the lung’s primary artery.
Interestingly, one study found this right ventricle dysfunction to be more pronounced in a certain group of lung disease patients even though their blood flow resistance was less severe. The study also noted that male patients had worse outcomes.
Meanwhile, both lung over-inflation and higher pressure inside the chest can reduce the amount of blood returning to the right ventricle. This, combined with the continuous high afterload, leads to failure of the right ventricle, reducing its ability to pump blood. This condition is known as cor pulmonale.
Preventing Pulmonary Hypertension Due to Lung Disease or Hypoxia
It’s crucial for patients with Group 3 Pulmonary Hypertension (PH) to stick to their treatment plan for their underlying medical condition that’s causing the PH. Those with advanced lung diseases, both restrictive and obstructive, that require supplemental oxygen should be educated about the importance of using their oxygen regularly to avoid low oxygen levels in their blood for extended periods.
Patients with Chronic Obstructive Pulmonary Disease (COPD) should be encouraged to use their inhalers consistently. Additionally, if a patient has pulmonary fibrosis, there might be a need to consider anti-fibrotic treatment. These strategies could be key in slowing down the advancement of PH.
Regular check-ups with lung specialists and prompt referrals to PH experts are important. These actions help in identifying any signs of the disease progression early and in starting the necessary treatment. Patients should also be periodically evaluated to assess if a lung transplant is needed.
