Introduction

Obesity is associated with a number of complications in the body, especially the heart. However, the effect of excessive weight gain on our respiratory system is often overlooked. Obesity hypoventilation syndrome, a breathing disorder involving reduced oxygenation in obese individuals, is often associated with increased pressure on the heart due to respiratory complications also known as pulmonary hypertension. These two interrelated respiratory disorders can have a significant impact on the person’s quality of life and severe consequences on heart health if left untreated.¹ Whether you have been diagnosed and require further information, or think you may have some symptoms, let us learn more about these treatable conditions, how they occur, warning symptoms and treatment options.

What is obesity hypoventilation syndrome (OHS)?

The levels of oxygen and carbon dioxide in our blood are determined by the act of breathing. Obesity can affect the mechanics of breathing resulting in incomplete exhalation and increased levels of carbon dioxide in the blood. The prevalence of OHS in obese individuals ranges from 10% to 20%.²

So why does this happen? The underlying mechanisms are inadequate movement of the diaphragm due to abdominal fat tissue, issues with the gas exchange mechanism in the lungs, or some chemical irregularities in the respiratory processes. These factors cause symptoms such as:

• Feeling of shallow breathing or feeling that you are not able to breathe in or out completely
• Disturbed sleep due to breathing issues while sleeping
• Feeling faint, breathless or tired
• Brain fog
• Excessive daytime sleepiness
• Morning headaches

The disease can lead to other conditions such as obstructive sleep apnoea, hypertension metabolic syndrome or even respiratory failure in severe cases if untreated.^1,2

Understanding pulmonary hypertension (PH)

Our heart is the pump that supplies blood to various organs in our body through tubes called blood vessels. The blood vessels that supply and bring blood to the heart from our lungs are called the pulmonary blood vessels. Pulmonary hypertension is a condition characterised by increased pressure in the pulmonary blood vessels; causing changes in the structure of the blood vessels, the way oxygen and carbon dioxide are exchanged in the lungs as well as the pumping function of the heart.³

Some symptoms of pulmonary hypertension include:

• Breathlessness even while resting
• Feeling tired all the time
• Chest pain
• Your heartbeat seems faster than normal or irregular (palpitations)
• Fainting³

If untreated pulmonary hypertension can cause heart disorders such as right heart failure, arrhythmias, thromboembolisms or organ dysfunction.³

Diagnosis of PH includes comprehensive clinical and physical assessment, thorough clinical history, blood tests and imaging scans. Echocardiography is done to visualise your heart and vessels.^3,6

Treatment includes medication and lifestyle modification, which will be discussed in detail in further sections.

The relationship between OHS and PH

How are these two disorders related? Obesity is a risk factor for both conditions, with increased body weight being a key factor causing the heart and respiratory muscles to overwork. Obesity can also cause inflammation in the blood vessels. There may be changes in the structure of organs and increased muscle size in the heart and blood vessels due to increased pressure, causing the heart to pump harder, leading to an enlarged heart. This enlargement can impair heart function and potentially lead to heart failure.^4,5

Respiratory issues noted in OHS can lead to changes in the blood vessels of the lungs. When untreated, higher carbon dioxide levels can cause the vessels to narrow, increasing pressure in the lung vessels, pulmonary vessels, and the heart. This results in pulmonary hypertension. A comprehensive treatment plan that addresses the challenges posed by these complex disorders can prevent complications such as heart failure and multiple organ dysfunctions.^4,5

Clinical implications and complications

The coexistence of PHS and PH causes a myriad of complex symptoms, complications and predisposition towards serious illnesses. Some of these are discussed below.

• Cardiovascular complications: Right heart failure, arrhythmias, systemic hypertension, and changes in the anatomy of the heart and blood vessels are caused as a result of increased pressure in the heart⁴
• Inflammatory reactions: Chronic hypoventilation and disturbed sleep due to breathing issues at night, can cause changes in the immune system resulting in widespread internal inflammation. This can worsen pre-existing conditions and cause fatigue, aches and brain fog⁴
• Quality of life: The symptoms affect day-to-day activities and functioning leading to increased psychological and social stress. Delayed treatment can affect the overall quality of life⁴

Diagnosis and management

Early diagnosis based on a thorough clinical assessment and imaging tests is key to developing a holistic treatment plan for this complex interplay of conditions. It requires a collaborative approach involving multidisciplinary specialist doctors, laboratory technicians, radiographers and the entire medical team.

Diagnosis of obesity hypoventilation syndrome (OHS)

Clinical assessment: it includes a comprehensive clinical history including your sleep patterns, diet, previous illnesses and daily routine. Your heart and breathing will be listened to through the stethoscope and your blood pressure taken.

Some diagnostic tests include a blood test to check the levels of oxygen and carbon dioxide in your blood. You may be referred to the sleep specialist for further tests.^1,2

Diagnosis of pulmonary hypertension (PH)

After taking a comprehensive clinical history, you will be booked in for an echocardiogram, which can help visualise your heart function and vessels.

A procedure called cardiac catheterisation may be done after a specialist referral, to measure the blood pressure in your pulmonary vessels.^3,4

Management strategies

The goals of the treatment are to address symptoms, alleviate underlying respiratory and cardiac issues and improve quality of life. This is achieved through medicines, maintenance therapies, lifestyle modifications and monitoring.⁵

Medicinal therapies

Antihypertensive medications and diuretics are used to address symptoms related to pulmonary hypertension. Some targeted therapies such as continuous positive airway pressure can be used to provide mechanical support and improve breathing.^5,6

Lifestyle changes

Maintaining a healthy, nutritionally balanced diet is vital to maintaining a healthy state of being. A holistic exercise plan may be implemented to promote movement gradually. It is also important to reduce smoking and alcohol intake.⁷

Long term monitoring

Regular follow-up and tests may be required to monitor the status of the disease and response to treatment. It helps catch on to any complications and signs of progression at early stages and prevent life-threatening manifestations.⁷

Prognosis and outlook

How serious is the disease and is it possible to recover? The prognosis of the disease depends on various factors, including:

• Disease severity: severity of symptoms, extent of changes in the structure of the heart muscles and vessels, as well as the blood test results can indicate disease severity^4,5
• Associated disorders: The presence of other disorders such as hypertension, type 2 diabetes, obstructive sleep apnoea and heart disorders can worsen the prognosis of the disease^4,5
• Treatment adherence: Following the treatment protocol determines how efficiently the treatment works^4,5
• Lifestyle factors: smoking and alcohol intake can worsen the prognosis of the disorders^4,5

While these conditions can increase the risk of developing cardiovascular disorders in the future, regular monitoring and a comprehensive treatment plan can improve the prognosis and enhance survival.

FAQ’s

What are the risk factors for developing obesity hypoventilation syndrome (OHS)?

Obesity hypoventilation syndrome (OHS) primarily affects individuals with obesity, particularly those with central adiposity and visceral fat accumulation. Other risk factors for OHS include male gender, older age, sedentary lifestyle, and underlying respiratory conditions such as obstructive sleep apnoea (OSA).^1,2

Can OHS be reversed with weight loss?

Weight loss is a cornerstone of OHS management and may lead to improvements in respiratory function and ventilation. Studies have shown that achieving and maintaining weight loss through lifestyle modifications, dietary interventions, and exercise can alleviate symptoms of OHS and reduce the need for respiratory support therapies such as positive airway pressure (PAP) therapy.⁷

What are the treatment options for pulmonary hypertension (PH)?

The management of pulmonary hypertension (PH) involves a combination of pharmacological therapies, lifestyle modifications, and supportive measures aimed at improving pulmonary vascular function and reducing cardiovascular strain. Medications target specific pathways involved in pulmonary vascular remodelling and vasoconstriction. Additionally, supportive measures such as supplemental oxygen therapy, diuretics, and exercise rehabilitation may be recommended to optimise clinical outcomes and enhance the quality of life for individuals with PH.⁶

Is OHS associated with an increased risk of cardiovascular complications?

Yes, individuals with obesity hypoventilation syndrome (OHS) are at increased risk of developing cardiovascular complications, including systemic hypertension, right heart failure, arrhythmias, and coronary artery disease. Chronic hypoventilation and nocturnal hypoxemia associated with OHS contribute to pulmonary vascular remodelling, endothelial dysfunction, and right ventricular strain, ultimately leading to cardiovascular morbidity and mortality.²

Can pulmonary hypertension (PH) be cured?

While there is currently no cure for pulmonary hypertension (PH), early diagnosis and aggressive management can help alleviate symptoms, improve functional status, and slow disease progression. Targeted pharmacotherapy, lifestyle modifications, and multidisciplinary care are essential in managing PH and reducing cardiovascular morbidity and mortality.⁶ 

Summary

Obesity may be associated with disorders such as obesity hypoventilation syndrome and pulmonary hypertension due to its effect on breathing and respiration.

Obesity hypoventilation syndrome is the increase of carbon dioxide levels in the blood due to incomplete exhalation.

Pulmonary hypertension is the increased pressure in the pulmonary blood vessels in the heart caused by factors including inflammation of vessels in the lungs, incomplete exhalation and changes to the structure of vessels.

These disorders can increase the risk of developing cardiovascular disorders if not treated promptly.

Diagnosis is conducted through a combination of comprehensive clinical assessment, blood tests and imaging tests. Treatment includes medicines; maintenance therapies like CPAP, lifestyle modifications and regular long-term follow-up.