What is Obesity-Hypoventilation Syndrome?

In the early 19th century, author Charles Dickens noted in his book “The Posthumous Papers of the Pickwick Club” a condition we now know as Obesity Hypoventilation Syndrome (OHS). This condition refers to a situation where an obese person has difficulty breathing properly during wakefulness, and this can’t be attributed to other conditions that might cause high carbon dioxide levels in the blood, like chronic lung disease.

OHS is associated with significant heart and lung-related health risks and can be difficult to treat. While we don’t fully know what causes OHS, a lower than normal response to high carbon dioxide levels plays a key role. This text explores the causes, spread, inner workings, physical symptoms, and evaluation of OHS. It also covers other types of sleep-related breathing disorders in subsequent sections.

What Causes Obesity-Hypoventilation Syndrome?

Several factors contribute to the development of Obesity Hypoventilation Syndrome (OHS), with obesity and sleep apnea being the main ones. There are also other factors like defects in ventilatory control that lead to reduced responsiveness to changes in oxygen and carbon dioxide levels in the body, as explained in the section on how the syndrome progresses.

Risk Factors and Frequency for Obesity-Hypoventilation Syndrome

Obesity Hypoventilation Syndrome (OHS) affects a varied number of people as per different studies. The global obesity epidemic, affecting everyone from children to adults, has resulted in an increase in OHS cases across these age groups. Currently, a significant 35% of the U.S. population struggles with obesity, with some reaching the stage of morbid obesity where the body mass index (BMI) exceeds 40 kg/m^2. The occurrence of morbid obesity has gone up five times and it’s estimated to affect 8% of the adult U.S. population. Extreme obesity, with a BMI over 50 kg/m^2 has increased ten times and continues to rise. About 20-30% of people with obstructive sleep apnea, a related condition, are estimated to have OHS.

OHS is seen more in men than women, older people, African Americans more than their white counterparts, and in the Asian community, it is observed at a lower BMI range.

While men generally have higher rates of OHS, women tend to report more cases in sleep disorder clinics. Delay in diagnosing OHS in women is correlated with adverse and more severe development of the disease.

Signs and Symptoms of Obesity-Hypoventilation Syndrome

Obesity Hypoventilation Syndrome (OHS) can have a range of presentations. Some patients might experience a severe, rapid increase in breathing issues that lead to respiratory failure and too much carbon dioxide in the blood (acute respiratory acidosis). Others, however, might be medically stable when they are diagnosed. In most cases though, patients have symptoms that are typical of Obstructive Sleep Apnea (OSA). These can include loud snoring, choking during sleep, episodes of not breathing (apneas) that are noticed by others, excessive sleepiness in the daytime, and headaches when they wake up.

People with OHS often have difficulty breathing (dyspnea) during normal activities. They might also show evidence of heart issues due to long-term high blood pressure in the lungs (cor pulmonale). When they are examined, doctors usually find that they have a large neck size, a narrow throat and airway, a strong pulse in the arteries that supply the lung, and swelling in their lower legs (edema).

  • Loud snoring
  • Choking during sleep
  • Short breathing pauses during sleep (apneas)
  • Excessive daytime sleepiness
  • Morning headaches
  • Difficulty breathing during normal activities (dyspnea)
  • Signs of heart issues due to long-term high blood pressure in the lungs (cor pulmonale)
  • Large neck size
  • Narrow throat and airway
  • Strong pulse in the artery to the lung
  • Swelling in lower legs (edema)

Testing for Obesity-Hypoventilation Syndrome

If someone has a Body Mass Index (BMI) greater than 30 kg/m^2 and experiences unusual shortness of breath when exercising and excessive sleepiness, they might be at risk for Obesity Hypoventilation Syndrome (OHS). Therefore, doctors usually recommend screening for OHS in individuals with severe obesity and those suffering from Obstructive Sleep Apnea (OSA). Additionally, signs such as lower oxygen levels when awake (below 94%), and/or an increased level of bicarbonate in the blood (above 27 mEq/L) could indicate OHS.

Bicarbonate levels in the blood can go up as a response to changes in acidity caused by long durations of high carbon dioxide in the body. A high bicarbonate level could be an early flag for chronic high carbon dioxide and has been found in 50% of OHS patients when above 27 mEq/L. In contrast, a bicarbonate level less than 27 mmol/L usually rules out OHS, assuming the prior likelihood of the disease is not very high (less than 20%).

A more definitive way to diagnose OHS is the analysis of arterial blood gases, which shows low oxygen levels when awake. It’s also helpful to look at the total sleep time spent with oxygen levels below 90%. People with an extremely high occurrence of OSA (more than 100 events per hour), or severe drops in oxygen levels during sleep (below 60%), were over 75% more likely to have OHS.

The American Academy of Sleep Medicine has set certain criteria for diagnosing OHS. These include having low oxygen levels when awake (PaCO2 greater than 45 mmHg), being obese (BMI above 30 kg/m^2), and the low oxygen levels not being primarily caused by other medical conditions like lung diseases, problems with the pulmonary blood vessels, disorders of the chest wall, drug use, nerve issues, muscle weakness, or other known issues of under-ventilation.

The best way to diagnose OHS is to confirm low oxygen levels during the day. However, getting this information usually requires a hospital setting, which is where most people with OHS first present due to complications. However, diagnosis of OHS doesn’t necessarily require polysomnography (a type of sleep study), but this can help identify patients with co-existing OSA or actual sleep-related under-ventilation.

It’s important to note that diagnosing OHS requires ruling out other conditions associated with under-ventilation. Once high carbon dioxide levels have been confirmed, lung function tests are done to exclude other possible causes. In people with OHS, these tests are usually normal or show signs of under-ventilation without significant obstruction of the airway.

Treatment Options for Obesity-Hypoventilation Syndrome

Obesity Hypoventilation Syndrome (OHS) is associated with a high rate of illness and death. The treatment goal is to normalize low oxygen and high carbon dioxide levels in the blood and improve symptoms. Several treatments, including positive airway pressure therapy, weight loss surgery, and medication, have been tried.

Positive Airway Pressure Therapy is often the go-to treatment for OHS. This therapy significantly decreases the buildup of carbon dioxide during sleep and reduces daytime sleepiness. Available options include Continuous Positive Airway Pressure (CPAP), Bi-level Positive Airway Pressure, and other non-invasive ventilation methods. Generally, CPAP is the preferred choice for patients who also experience severe sleep apnea. Non-invasive ventilation can be beneficial for patients without severe sleep apnea or for those who didn’t respond well to CPAP or couldn’t tolerate it. However, in hospitalized patients with suspected OHS experiencing acute respiratory failure due to high levels of carbon dioxide, non-invasive ventilation should be used until they have undergone further diagnostic tests and CPAP adjustments in a sleep lab.

A recent study comparing non-invasive ventilation, CPAP, and lifestyle changes showed that these treatments improved sleep-related issues. Non-invasive ventilation was found to be better at improving breathing compared to other treatments.

Weight loss can have a positive impact on both OHS and sleep apnea, as well as related heart conditions. Many studies have indicated that weight loss can improve symptoms of OHS. It significantly reduces carbon dioxide production and improves sleep apnea severity and air exchange in the lungs. It also helps improve high blood pressure in the lungs and left ventricular dysfunction, which can reduce heart-related issues in patients with OHS. Therefore, weight-loss interventions, including surgical options like bariatric surgery, that help lose 25%-30% of total body weight are recommended, if not contraindicated.

Tracheostomy, a surgical procedure that involves creating an opening in the neck to place a tube into a person’s windpipe, can relieve airway obstruction during sleep, improving inhalation and waking carbon dioxide levels in the blood. However, it may not bring all patients back to normal carbon dioxide levels as it doesn’t affect carbon dioxide production or impaired muscle strength.

Breathing difficulties can be caused by different factors which can be classified into three main categories:

  • Obstacles to Breathing: These can be due to diseases of the chest wall or problems with the muscles that help you breathe, or due to lung diseases that cause blockage.
  • Control Issues: Some individuals have inherent conditions that affect the control center of breathing, including a condition nicknamed “Ondine’s curse” where automatic control of breathing is absent. There could also be issues due to irregularities in genes, or problems associated with the brainstem, the carotid body (a sensor responsible for detecting oxygen levels in your blood), or a condition known as metabolic alkalosis, which affects your body’s pH balance.
  • Mixed Problems: In certain cases, difficulties in breathing can be due to a combination of the above issues. Some of the diseases that can impact both your body’s control over breathing and ability to breathe include Chronic Obstructive Pulmonary Disease (COPD), hypothyroidism, and sleep apnea.

Regardless of the cause, if you are experiencing breathing problems, it’s essential to seek medical attention right away.

What to expect with Obesity-Hypoventilation Syndrome

Obesity hypoventilation, a condition where overweight people have trouble breathing deeply or quickly enough, is known to lower the quality of life and extend hospital stays, especially in intensive care units. In people with other health issues like diabetes and asthma, the risk of death significantly increases – with rates as high as 23% in 18 months and 46% in 50 months.

One helpful treatment for this condition is the early use of CPAP (Continuous Positive Airway Pressure), which can reduce the risk of death by 10%. However, in some cases, such as in older patients with restrictive breathing problems or those recently experiencing severe increased CO2 levels in their blood, CPAP might not work as effectively.

Moreover, the baseline carbon dioxide pressure in arterial blood (PaCO2) can predict continued hypoventilation despite treatment.

Unfortunately, the outlook is not favorable for patients with Obesity Hypoventilation Syndrome who can’t lose weight, as it could result in a shorter lifespan.

Possible Complications When Diagnosed with Obesity-Hypoventilation Syndrome

Obesity is known to directly increase the risk of pulmonary hypertension (PH), which is high blood pressure in the lungs, in individuals with Obesity Hypoventilation Syndrome (OHS). This is true whether or not they also suffer from Obstructive Sleep Apnea (OSA). A recent study, the Pickwick trial, involving 246 people, revealed that half of the patients with OHS showed signs of PH through an echocardiography test. This test measures the blood pressure in the heart’s arteries, and in this case, found results of 40 mmHg or more, indicating pulmonary hypertension. The study highlighted that both low levels of oxygen in the blood while the patient is awake (known as low PaO2 levels), and obesity, can independently predict the occurrence of PH in severe cases of OSA. On the other hand, obesity, early/late diastolic relationship, which refers to the ratio of early to late ventricular filling velocities, were predictors of PH in mild or moderate cases of OSA.

Recovery from Obesity-Hypoventilation Syndrome

Patients suffering from Obesity Hypoventilation Syndrome (OHS) often have more concurrent health conditions compared to those with Obstructive Sleep Apnea (OSA) alone. This could potentially increase their risk of complications after surgery. As a result, after-surgery care and assessments are crucial for these patients, particularly those who’re obese, have OSA, issues with low ventilation, or unexplained low oxygen levels in their blood. This special care includes careful choice of sedation and anesthesia, ensuring the patient is positioned correctly, and using oxygen and non-invasive ventilation properly.

Preventing Obesity-Hypoventilation Syndrome

This article highlights the importance of people being aware of obesity hypoventilation syndrome. It’s extremely crucial for individuals to understand this condition, seek early diagnosis, and stick to the treatment plan. People should know the various treatment options available. These include setting targets for weight loss and considering methods beyond just diet and exercise. Treatments like surgery and bariatric procedures are also options. Lastly, patients should know how to correctly utilize their mechanical devices like positive airway pressure and non-invasive ventilation machines.

Frequently asked questions

Obesity-Hypoventilation Syndrome (OHS) is a condition where an obese person has difficulty breathing properly during wakefulness, and this cannot be attributed to other conditions that might cause high carbon dioxide levels in the blood, like chronic lung disease. It is associated with significant heart and lung-related health risks and can be difficult to treat.

The occurrence of morbid obesity has gone up five times and it's estimated to affect 8% of the adult U.S. population.

The signs and symptoms of Obesity-Hypoventilation Syndrome (OHS) include: - Loud snoring - Choking during sleep - Short breathing pauses during sleep (apneas) - Excessive daytime sleepiness - Morning headaches - Difficulty breathing during normal activities (dyspnea) - Signs of heart issues due to long-term high blood pressure in the lungs (cor pulmonale) - Large neck size - Narrow throat and airway - Strong pulse in the artery to the lung - Swelling in lower legs (edema) These symptoms can vary in severity and presentation. Some patients may experience a rapid increase in breathing issues leading to respiratory failure, while others may be medically stable at the time of diagnosis. It is important to note that many patients with OHS also exhibit symptoms typical of Obstructive Sleep Apnea (OSA), such as loud snoring, choking during sleep, and episodes of not breathing noticed by others.

Several factors contribute to the development of Obesity Hypoventilation Syndrome (OHS), with obesity and sleep apnea being the main ones. There are also other factors like defects in ventilatory control that lead to reduced responsiveness to changes in oxygen and carbon dioxide levels in the body.

The doctor needs to rule out the following conditions when diagnosing Obesity-Hypoventilation Syndrome: 1. Diseases of the chest wall or problems with the muscles that help you breathe. 2. Lung diseases that cause blockage. 3. Conditions that affect the control center of breathing, such as "Ondine's curse" or irregularities in genes. 4. Issues associated with the brainstem or the carotid body (a sensor responsible for detecting oxygen levels in the blood). 5. Metabolic alkalosis, which affects the body's pH balance. 6. Chronic Obstructive Pulmonary Disease (COPD). 7. Hypothyroidism. 8. Sleep apnea.

The types of tests needed for Obesity-Hypoventilation Syndrome (OHS) include: 1. Screening tests: - Body Mass Index (BMI) measurement - Assessment of symptoms such as shortness of breath during exercise and excessive sleepiness - Evaluation for Obstructive Sleep Apnea (OSA) 2. Blood tests: - Measurement of bicarbonate levels in the blood (above 27 mEq/L) - Analysis of arterial blood gases to assess oxygen levels when awake 3. Lung function tests: - To exclude other possible causes of under-ventilation 4. Polysomnography (sleep study): - Not always necessary for diagnosis, but can help identify co-existing OSA or sleep-related under-ventilation It's important to note that diagnosing OHS requires ruling out other conditions associated with under-ventilation. Once high carbon dioxide levels have been confirmed, lung function tests are done to exclude other possible causes.

Obesity-Hypoventilation Syndrome (OHS) can be treated through various methods. The main treatment goal is to normalize low oxygen and high carbon dioxide levels in the blood and improve symptoms. Positive Airway Pressure Therapy, such as Continuous Positive Airway Pressure (CPAP), is often the go-to treatment for OHS. This therapy significantly decreases the buildup of carbon dioxide during sleep and reduces daytime sleepiness. Non-invasive ventilation methods can also be used for patients without severe sleep apnea or those who didn't respond well to CPAP. Weight loss interventions, including surgical options like bariatric surgery, are recommended to improve symptoms and related heart conditions. Tracheostomy, a surgical procedure, can relieve airway obstruction during sleep but may not bring all patients back to normal carbon dioxide levels.

When treating Obesity-Hypoventilation Syndrome, there can be side effects associated with the different treatment options. Here are the potential side effects for each treatment: Positive Airway Pressure Therapy: - Discomfort or irritation from wearing the mask - Dry or stuffy nose - Skin irritation or pressure sores from the mask - Claustrophobia or difficulty adjusting to wearing the mask Weight Loss: - Potential complications from weight loss surgery, such as infection, bleeding, or leaks - Nutritional deficiencies - Gallstones - Loose or sagging skin Tracheostomy: - Surgical complications, such as bleeding or infection - Scarring or changes in the appearance of the neck - Difficulty speaking or swallowing - Discomfort or pain at the site of the tracheostomy It's important to note that the benefits of these treatments generally outweigh the potential side effects, and the specific side effects can vary depending on the individual and their overall health. It's recommended to discuss the potential side effects and risks with a healthcare professional before starting any treatment.

The prognosis for Obesity-Hypoventilation Syndrome is not favorable for patients who cannot lose weight, as it could result in a shorter lifespan.

A pulmonologist or a sleep specialist.

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