Obesity Hypoventilation Syndrome

Obesity hypoventilation syndrome (OHS), or Pickwickian syndrome, is a breathing disorder that affects some people who have obesity. The condition results in too much carbon dioxide in your blood and not enough oxygen. This occurs due to hypoventilation, which means breathing at an abnormally slow rate. OHS can cause life-threatening health issues.


What is obesity hypoventilation syndrome?

Obesity hypoventilation syndrome (OHS) is a breathing disorder that affects some people who have obesity. The condition causes you to have too much carbon dioxide and not enough oxygen in your blood (hypercapnia). Normally, you exhale carbon dioxide and inhale oxygen. But when you’re breathing at a slow rate, you’re not moving enough air in and out of your lungs. This is called hypoventilation.

In addition to hypoventilation, you may also have sleep-disordered breathing due to obstructive sleep apnea. About 90% of the sleep-disordered breathing that occurs with OHS is due to obstructive sleep apnea. Therefore, OHS is typically a combination of three factors:

  • Obesity.
  • Hypoventilation.
  • Sleep-disordered breathing.

Another name for OHS is Pickwickian syndrome. In the 1950s, scientists named the condition after a character in a Charles Dickens novel that had symptoms of OHS.

Obesity hypoventilation syndrome is a serious respiratory complication of obesity. It can cause life-threatening health issues, but it’s treatable.


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Who does obesity hypoventilation syndrome affect?

OHS affects more men and people assigned male at birth (AMAB) than women and people assigned female at birth (AFAB). It also affects Black people more often than white people.

How common is obesity hypoventilation syndrome?

The exact rates of OHS are unknown. But studies estimate that OHS occurs in 0.4% to 0.6% of the U.S. adult population. That equals about 1 out of every 260 American adults.


Symptoms and Causes

What are the symptoms of obesity hypoventilation syndrome?

Obesity hypoventilation syndrome symptoms typically occur due to lack of sleep and low blood oxygen levels (hypoxemia). These symptoms may include:

  • Shortness of breath.
  • Fatigue.
  • Lack of energy.
  • Daytime sluggishness.
  • Headaches.
  • Dizziness.
  • Depression.

While you’re sleeping, your bed partner may notice the following symptoms:

  • Loud snoring.
  • Choking or gasping.
  • Pauses in your breathing.

What causes obesity hypoventilation syndrome?

Researchers don’t know the exact cause of obesity hypoventilation syndrome. They believe it may be a combination of several factors, including:

  • A defect in your brain may affect the way it controls your breathing.
  • Extra weight against your chest wall can make it more difficult for your muscles to breathe deeply and fast enough.
  • Excess fat on your neck, chest and belly (abdomen) may produce hormones that affect your breathing patterns.


Diagnosis and Tests

How is OHS diagnosed?

Your healthcare provider will document your symptoms and perform a physical exam. They’ll measure your height and weight and calculate your body mass index (BMI). People with obesity have a BMI of 30 or greater.

Your provider may then request several tests to help diagnose OHS. These tests may include:

  • Arterial blood gas: Your provider will take a sample of blood from an artery to measure the amount of carbon dioxide and oxygen in your blood.
  • Pulse oximeter: Your provider will place a sensor to your finger to measure the amount of oxygen in your blood. This test doesn’t measure the amount of carbon dioxide in your blood. It also isn’t as accurate in measuring the oxygen level in your blood as a blood sample.
  • Pulmonary function tests: These tests check your lung functioning to rule out other possible causes of your breathing difficulty.
  • Chest X-ray: A chest X-ray can also rule out possible causes of breathing difficulty.
  • Sleep study (polysomnography): A sleep study determines if you have sleep apnea as well, and if so, how severe it is.

Management and Treatment

How do you treat obesity hypoventilation syndrome?

Obesity hypoventilation syndrome treatment includes weight loss and breathing assistance.

Weight loss

Getting to and maintaining a healthy weight for your body is the first step in treating OHS. Weight loss alone may be all you need to manage your symptoms and treat issues associated with your condition. Healthy lifestyle changes such as the following can help you reach your goals:

  • Eat a healthy diet, such as the Mediterranean diet.
  • Aim for 30 minutes of physical activity a day.
  • Develop good sleeping habits.

Depending on your condition, your provider may recommend weight loss surgery to help you lose weight. This may include a procedure such as gastric bypass surgery.

Breathing assistance

Your provider may recommend a special mechanical ventilation machine to help you breathe. These noninvasive devices help keep your airways open at night, which helps increase your blood oxygen levels. You wear a special mask when you’re sleeping, and the machine delivers air to you through a tube. These devices include:

  • Continuous positive airway pressure (CPAP): A CPAP machine delivers a constant pressure of air both when you’re breathing in and when you’re breathing out.
  • Bilevel positive airway pressure (often known under the trade name BiPAP®): A BiPAP machine delivers higher pressures of air when you’re breathing in than when you’re breathing out.

Rarely, when a positive airway pressure device can’t help control your condition, you’ll need a tracheostomy. With a tracheostomy, a surgeon makes a hole in your neck through to your windpipe to help you breathe.


How can I reduce my risk of OHS?

You can reduce your risk of developing OHS by maintaining a healthy weight. If your provider prescribed a CPAP or BiPAP, make sure to continue the treatment as directed.

In addition, talk to your provider if you plan on flying or if you have an upcoming surgery. Both of these situations can increase your risk for serious complications.

Outlook / Prognosis

What is the life expectancy of someone with obesity hypoventilation syndrome?

With treatment, you may reduce the symptoms of OHS or get rid of them entirely. Some people find losing weight alone can help with their symptoms. Treatment is important because it can improve your quality of life. It also decreases your chances of further complications. Early treatment with a breathing device can reduce the mortality rate of OHS by 10%.

Left untreated, OHS can lead to life-threatening complications, including heart and blood vessel issues. A lack of oxygen puts a significant strain on your heart. You’re also at risk of developing complications related to a lack of sleep. Without treatment, your quality of life decreases, and your risk of hospitalization increases.

The outlook (prognosis) for people who don’t get treatment is poor. Untreated obesity hypoventilation syndrome typically leads to a shortened life expectancy. In people with other medical conditions, the mortality rate of OHS is 23% over an 18-month period.

What are the possible complications of obesity hypoventilation syndrome?

Left untreated, obesity hypoventilation syndrome can cause complications related to lack of sleep. These complications may include:

  • Depression.
  • Agitation and irritability.
  • Increased risk of accidents.
  • Issues with sex and intimacy.

OHS can also cause heart issues, including:

Living With

When should I see my healthcare provider?

You should see your healthcare provider if:

  • You have obesity along with other symptoms of OHS.
  • Your bed partner notices you snore loudly or pauses in your breathing.
  • You’re overly tired during the day.

A note from Cleveland Clinic

Obesity hypoventilation syndrome is a severe respiratory complication of obesity. If you have obesity, breathing problems or any sleep issues, reach out to a healthcare provider. They’re there to help. If a provider diagnoses you with OHS, they can determine the correct treatment plan for you. With early treatment, the symptoms of OHS can decrease or go away completely. Without prompt treatment, the condition can cause life-threatening health issues. So, see a provider right away.

Medically Reviewed

Last reviewed on 10/27/2022.

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