People with significant obesity are at risk for developing obesity hypoventilation syndrome (OHS). OHS results when the body does not receive enough oxygen and does not eliminate enough carbon dioxide while breathing during sleep. OHS can cause extreme daytime sleepiness and lead to life threatening medical complications. OHS is easily treated with an assistive breathing device that is worn during sleep. Achieving and maintaining a healthy weight can actually eliminate the condition in many people.

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Sleep is vital for life, just like eating and breathing. Sleep allows your body to rest. It is believed that during sleep your brain performs important functions, such as storing memory and processing brain chemicals.

In a way, your body goes on “auto-pilot” while you sleep. Your brain regulates automatic functions for you, such as breathing, heart rate, and blood pressure. Although sleep is a complex process that is not fully understood, it is known that a good night’s sleep is important for optimal health and functioning.

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OHS causes people with obesity not to receive enough oxygen when they breathe during sleep. This results in a build-up of carbon dioxide. The exact cause of OHS is unknown. Researchers suspect that it may involve faulty messages in the brain and too much pressure on the chest from body fat that prevents deep breathing during sleep.

OHS is not the same thing as sleep apnea, although many people with OHS have sleep apnea. Sleep apnea is a condition in which people stop breathing numerous times when they sleep, causing awakening and gasping for air. With OHS alone, breathing does not stop, but it is inefficient, resulting in poor oxygen and carbon dioxide exchange.

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OHS can lead to sleep deprivation. You may feel excessively tired during the day. You may fall asleep during the day at unexpected times. You may feel depressed, moody, and irritable. You may have a harder time concentrating, performing your usual tasks, solving problems, and remembering things.

Severe OHS can cause low blood oxygen levels, termed hypoxia. You may feel tired after minimal activity. Your lips, fingers, or toes may appear blue. Untreated OHS can lead to right-sided heart failure. Signs of right-sided heart failure include shortness of breath, feeling tired after minimal activity, and swollen legs, ankles and feet.

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You should contact your doctor if you have obesity and excessive daytime drowsiness or other symptoms of OHS. Your doctor will review your medical history, perform a physical examination, conduct some simple tests, and refer you to other specialists as necessary.

An arterial blood gas test is used to check the amount of carbon dioxide and oxygen in your blood. A high level of carbon dioxide in the blood while a person is awake indicates OHS and differentiates it from sleep apnea. Pulmonary function tests are used to evaluate the efficiency of your lungs. Such tests usually involve breathing into a device while measurements are taken.

You may be referred to a sleep medicine doctor for a sleep study. A sleep study is helpful for diagnosing OHS, sleep apnea, and other sleep disorders. A sleep study is used to take measurements of basic body functions, such as heart rate, blood pressure, and blood oxygen levels, while you sleep. A sleep study may be conducted at a sleep clinic or in some cases, it may be conducted at your home.

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Positive Airway Pressure (PAP) is the most common treatment for people with OHS. PAP involves wearing a device over the nose during sleep. The nasal device is connected to a small machine that creates airflow and gentle air pressure to keep the airway open. The machine senses when you are inhaling and delivers more air pressure during that time. PAP is an effective way to treat OHS. Some patients may require the use of oxygen in addition to PAP therapy to keep blood oxygen levels up in the normal range.

Losing weight and maintaining a healthy weight can be a long-term solution and actually eliminate OHS. You should ask your doctor about a safe weight loss plan for you. Your doctor may refer you to a nutritionist, exercise specialist, or support group for more information and emotional support. Weight loss surgery may also be an option for some patients.

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You can help prevent the serious potential complications of OHS by contacting your doctor and receiving treatment. OHS that is treated generally has a good prognosis. Losing weight and maintaining a healthy weight can reverse OHS. Ask your doctor to help you formulate a safe weight loss plan.

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Am I at Risk

People that are very obese are at risk for OHS. Generally, adults with a body mass index (BMI) of over 30 are obese. The BMI is used to estimate what percentage of your body consists of fat. Typically, people that are 100 pounds overweight are categorized as morbidly obese.

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Untreated OHS can lead to life-threatening medical complications including high blood pressure, right-sided heart failure, and death.

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Given the serious consequences of untreated OHS treatment has focused on multiple approaches, including PAP therapy, weight reduction surgery, tracheostomy and medicines to stimulate breathing.

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This information is intended for educational and informational purposes only. It should not be used in place of an individual consultation or examination or replace the advice of your health care professional and should not be relied upon to determine diagnosis or course of treatment.

The iHealthSpot patient education library was written collaboratively by the iHealthSpot editorial team which includes Senior Medical Authors Dr. Mary Car-Blanchard, OTD/OTR/L and Valerie K. Clark, and the following editorial advisors: Steve Meadows, MD, Ernie F. Soto, DDS, Ronald J. Glatzer, MD, Jonathan Rosenberg, MD, Christopher M. Nolte, MD, David Applebaum, MD, Jonathan M. Tarrash, MD, and Paula Soto, RN/BSN. This content complies with the HONcode standard for trustworthy health information. The library commenced development on September 1, 2005 with the latest update/addition on February 16, 2022. For information on iHealthSpot’s other services including medical website design, visit