Obesity hypoventilation (HI-po-ven-tih-LA-shun) syndrome (OHS) is a breathing disorder that affects some obese people. In OHS, poor breathing results in too much carbon dioxide (hypoventilation) and too little oxygen in the blood (hypoxemia).
OHS sometimes is called Pickwickian syndrome.
To understand OHS, it helps to understand how the lungs work. When you breathe, air passes through your nose and mouth into your windpipe. The air then travels to your lungs' air sacs. These sacs are called alveoli (al-VEE-uhl-eye).
Small blood vessels called capillaries (KAP-ih-lare-ees) run through the walls of the air sacs. When air reaches the air sacs, oxygen passes through the air sac walls into the blood in the capillaries. At the same time, carbon dioxide moves from the capillaries into the air sacs. This process is called gas exchange.
In people who have OHS, poor breathing prevents proper gas exchange. As a result, the level of carbon dioxide in the blood rises. Also, the level of oxygen in the blood drops.
These changes can lead to serious health problems, such as leg edema (e-DE-mah), pulmonary hypertension (PULL-mun-ary HI-per-TEN-shun), cor pulmonale (pul-meh-NAL-e), and secondary erythrocytosis (eh-RITH-ro-si-TOE-sis). If left untreated, OHS can even be fatal.
The cause of OHS isn't fully known. Researchers think that several factors may work together to cause the disorder.
Many people who have OHS also have obstructive sleep apnea. Obstructive sleep apnea is a common disorder in which the airway collapses or is blocked during sleep. This causes pauses in breathing or shallow breaths while you sleep.
Obstructive sleep apnea disrupts your sleep and causes you to feel very tired during the day. (For more information, go to the Health Topics Sleep Apnea article.)
Doctors treat OHS in a number of ways. One way is with positive airway pressure (PAP) machines, which are used during sleep.
PAP therapy uses mild air pressure to keep your airways open. Your doctor might recommend CPAP (continuous positive airway pressure) or BiPAP (bilevel positive airway pressure).
If your doctor prescribes PAP therapy, you'll work with someone from a home equipment provider to select a CPAP or BiPAP machine. The home equipment provider will help you select a machine based on your prescription and the features that meet your needs.
Other treatments for OHS include ventilator (VEN-til-a-tor) support and medicines. (A ventilator is a machine that supports breathing.)
OHS occurs with obesity, so your doctor will likely recommend weight loss as part of your treatment plan. Successful weight loss often involves setting goals and making lifestyle changes, such as following a healthy diet and being physically active.
OHS can lead to other serious health problems, so following your treatment plan is important. Your health care team, home equipment provider, and family can help you manage your treatment.
Obesity hypoventilation syndrome (OHS) is a breathing disorder that affects some obese people. Why these people develop OHS isn't fully known. Researchers think that several factors may work together to cause OHS. These factors include:
People who are obese are at risk for obesity hypoventilation syndrome (OHS). "Obesity" refers to having too much body fat. People who are obese have body weight that's greater than what is considered healthy for a certain height.
The most useful measure of obesity is body mass index (BMI). BMI is calculated from your height and weight. In adults, a BMI of 30 or more is considered obese.
You can use the National Heart, Lung, and Blood Institute's (NHLBI's) online BMI calculator to figure out your BMI, or your doctor can help you.
If you are obese, you're at greater risk for OHS if your BMI is 40 or higher. You're also at greater risk if most of your excess weight is around your waist, rather than at your hips. This is referred to as "abdominal obesity."
OHS tends to occur more often in men than women. At the time of diagnosis, most people are 40 to 60 years old.
Many of the signs and symptoms of obesity hypoventilation syndrome (OHS) are the same as those of obstructive sleep apnea. This is because many people who have OHS also have obstructive sleep apnea.
One of the most common signs of obstructive sleep apnea is loud and chronic (ongoing) snoring. Pauses may occur in the snoring. Choking or gasping may follow the pauses.
Other symptoms include:
You also may have rapid, shallow breathing. During a physical exam, your doctor might hear abnormal heart sounds while listening to your heart with a stethoscope. He or she also might notice that the opening to your throat is small and your neck is larger than normal.
When left untreated, OHS can cause serious problems, such as:
Obesity hypoventilation syndrome (OHS) is diagnosed based on your medical history, signs and symptoms, and test results.
A critical care specialist, pulmonologist (lung specialist), and/or sleep specialist may diagnose and treat your condition.
A sleep specialist is a doctor who diagnoses and treats sleep problems. Examples of such doctors include lung and nerve specialists and ear, nose, and throat specialists. Other types of doctors also can be sleep specialists.
Your health care team also may include:
Your doctor will ask about your signs and symptoms, such as loud snoring or daytime sleepiness. He or she also may ask about your use of alcohol and certain medicines, such as sedatives and narcotics. These substances can worsen OHS.
During the physical exam, your doctor will listen to your heart with a stethoscope. He or she also will check to see whether another disease or condition could be the cause of your poor breathing.
In OHS, poor breathing leads to too much carbon dioxide and too little oxygen in the blood. An arterial blood gas test can measure the levels of these gases in your blood.
For this test, a blood sample is taken from an artery, usually in your wrist. The sample is then sent to a laboratory, where the oxygen and carbon dioxide levels are measured.
Other tests also can measure the carbon dioxide level or oxygen level in your blood. These tests include a serum bicarbonate test and pulse oximetry.
A serum bicarbonate test measures the amount of carbon dioxide in the liquid part of your blood, called the serum. For this test, a blood sample is taken from a vein, usually in your wrist or hand.
Pulse oximetry measures the level of oxygen in your blood. For this test, a small sensor is attached to your finger or ear. The sensor uses light to estimate how much oxygen is in your blood.
Your doctor may recommend other tests to help check for conditions and problems related to OHS.
A polysomnogram (PSG) is a type of sleep study. You usually have to stay overnight at a sleep center for a PSG. The test records brain activity, eye movements, heart rate, and blood pressure.
A PSG also records the amount of oxygen in your blood, how much air is moving through your nose while you breathe, snoring, and chest movements. The chest movements show whether you're making an effort to breathe.
Your doctor might use the PSG results to help diagnose sleep-related breathing disorders, such as sleep apnea.
Lung function tests, also called pulmonary function tests, measure how well your lungs work. For example, these tests show:
A chest x ray is a test that creates pictures of the structures inside your chest, such as your heart, lungs, and blood vessels. This test can help rule out other conditions that might be causing your signs and symptoms.
An EKG is a test that detects and records the heart's electrical activity. The test shows how fast the heart is beating and its rhythm (steady or irregular). An EKG also records the strength and timing of electrical signals as they pass through your heart.
The results from an EKG might show whether OHS has affected your heart function.
A complete blood count (CBC) can show whether your body is making too many red blood cells as a result of OHS. A CBC measures many parts of your blood, including red blood cells.
A toxicology screen is a group of tests that shows which medicines and drugs you've taken and how much of them you've taken. A blood or urine sample usually is collected for a toxicology screen.
Treatments for obesity hypoventilation syndrome (OHS) include breathing support, weight loss, and medicines.
The goals of treating OHS may include:
Treatment for OHS often involves a machine that provides positive airway pressure (PAP) while you sleep.
PAP therapy uses mild air pressure to keep your airways open. This treatment can help your body better maintain the carbon dioxide and oxygen levels in your blood. PAP therapy also can help relieve daytime sleepiness.
Your doctor might recommend CPAP (continuous positive airway pressure) or BiPAP (bilevel positive airway pressure). CPAP provides continuous mild air pressure to keep your airways open. BiPAP works almost the same, but it changes the air pressure while you breathe in and out.
The machines have three main parts:
Some machines have other features, such as heated humidifiers. The machines are small, lightweight, and fairly quiet. The noise they make is soft and rhythmic.
Some people who have OHS receive extra oxygen as part of their PAP treatment. However, oxygen therapy alone isn't recommended as a treatment for OHS.
PAP therapy also is used to treat obstructive sleep apnea. Many people who have OHS also have this common condition.
If your doctor prescribes PAP therapy, you'll work with someone from a home equipment provider to select a CPAP or BiPAP machine. The home equipment provider will help you pick a machine based on your prescription and the features that meet your needs.
If you have severe OHS that requires treatment in a hospital, you might be put on a ventilator. A ventilator is a machine that supports breathing. This machine:
A ventilator blows air, or air with extra oxygen, into the airways through a breathing tube. One end of the tube is inserted into your windpipe, and the other end is hooked to the ventilator.
Usually, the breathing tube is put into your nose or mouth and then moved down into your throat. A tube placed like this is called an endotracheal (en-do-TRA-ke-al) tube. Endotracheal tubes are used only in a hospital setting.
Sometimes the breathing tube is placed through a surgically made hole called a tracheostomy (TRA-ke-OS-toe-me). The hole goes through the front of your neck and into your windpipe.
The procedure to make a tracheostomy usually is done in an operating room. You'll be given medicine so you won't feel any pain. The tracheostomy allows you to be on a ventilator in the hospital, in a long-term care facility, or at home.
Talk with your doctor about how long you'll need ventilator support and whether you can receive treatment at home.
For more information about ventilator support, go to the Health Topics Ventilator/Ventilator Support article.
Your doctor will likely recommend weight loss as part of your treatment plan. Successful weight loss often involves setting goals and making lifestyle changes. For example, eating fewer calories and being physically active can help you lose weight.
Medicines and weight-loss surgery might be an option if lifestyle changes aren't enough. Your doctor will advise you on the best weight-loss treatment for you.
For more information about weight loss, go to the treatment section of the Health Topics Overweight and Obesity article.
Your doctor may prescribe medicines to treat OHS (although this treatment is less common than others).
Your doctor also may advise you to avoid certain substances and medicines that can worsen OHS. Examples include alcohol, sedatives, and narcotics. They can interfere with how well your body is able to maintain normal carbon dioxide and oxygen levels.
If you're having surgery, make sure you tell your surgeon and health care team that you have OHS. Some medicines routinely used for surgery can worsen your condition.
You can prevent obesity hypoventilation syndrome (OHS) by maintaining a healthy weight. However, not everyone who is obese develops OHS. Researchers don't fully know why only some people who are obese develop the condition.
Adopting healthy habits can help you maintain a healthy weight. Many lifestyle habits begin during childhood. So, it's important to make following a healthy lifestyle a family goal.
A healthy diet is an important part of a healthy lifestyle. A healthy diet includes a variety of vegetables and fruits. It also includes whole grains, fat-free or low-fat dairy products, and protein foods, such as lean meats, eggs, poultry without skin, seafood, nuts, seeds, beans, and peas.
A healthy diet is low in sodium (salt), added sugars, solid fats, and refined grains. Solid fats are saturated fat and trans fatty acids. Refined grains come from processing whole grains, which results in a loss of nutrients (such as dietary fiber). Examples of refined grains include white rice and white bread.
For more information about following a healthy diet, go to the National Heart, Lung, and Blood Institute's "Your Guide to Lowering Your Blood Pressure With DASH" and the U.S. Department of Agriculture's ChooseMyPlate.gov Web site. Both resources provide general information about healthy eating.
To adopt other healthy lifestyle habits, follow these tips:
For more information, go to the prevention section of the Health Topics Overweight and Obesity article.
Even if you have OHS, you might be able to prevent the condition from worsening. For example, avoid alcohol, sedatives, and narcotics. These substances can interfere with how well your body is able to maintain normal carbon dioxide and oxygen levels.
Obesity hypoventilation syndrome (OHS) can be very serious. However, following your treatment plan can help improve your breathing. Treatment also can:
To make sure your treatment is working, see your doctor for ongoing care. Tell him or her if your treatment is causing any side effects or problems.
If your doctor has prescribed CPAP (continuous positive airway pressure) or BiPAP (bilevel positive airway pressure), use your machine as directed. You may find that it takes time to adjust to this treatment.
If you can't adjust to the CPAP or BiPAP machine, or if it doesn't seem to work well, talk with your doctor or home equipment provider. You may need to switch to a different device or mask. If you're having side effects from CPAP or BiPAP, your doctor may be able to treat them.
Weight loss will likely be part of your treatment plan. Your doctor will work with you to create a reasonable weight-loss plan. Your doctor and other members of your health care team can help you meet your weight-loss goals.
For more information about weight-loss treatments and for tips on losing weight, go to the Health Topics Overweight and Obesity article.
OHS can cause daytime sleepiness. Until this symptom is fully treated, know the dangers of driving or using heavy machinery while sleepy.
If you're having surgery, tell your surgeon and health care team that you have OHS. Some medicines routinely used for surgery can worsen your condition.
Ask your doctor when you should contact him or her or seek emergency medical care. In an emergency, call 9–1–1. You may want to wear a medical ID bracelet or necklace to alert others to your medical needs.
If you have a family member who has OHS, you can help him or her achieve success with treatment. Tell his or her doctor about any signs or symptoms you've noticed.
For example, many people who have OHS also have obstructive sleep apnea. Family members or bed partners usually are the first to notice symptoms, such as loud snoring and pauses in breathing. Telling the doctor about these symptoms can help him or her diagnose and treat your family member promptly.
Encourage your family member to seek medical help when needed and to follow up with his or her doctor regularly. You also can help your family member adopt healthy lifestyle habits, such as following a healthy diet and being physically active.
The National Heart, Lung, and Blood Institute (NHLBI) is strongly committed to supporting research aimed at preventing and treating heart, lung, and blood diseases and conditions and sleep disorders.
NHLBI-supported research has led to many advances in medical knowledge and care. Often, these advances depend on the willingness of volunteers to take part in clinical trials.
Clinical trials test new ways to prevent, diagnose, or treat various diseases and conditions. For example, new treatments for a disease or condition (such as medicines, medical devices, surgeries, or procedures) are tested in volunteers who have the illness. Testing shows whether a treatment is safe and effective in humans before it is made available for widespread use.
By taking part in a clinical trial, you can gain access to new treatments before they're widely available. You also will have the support of a team of health care providers, who will likely monitor your health closely. Even if you don't directly benefit from the results of a clinical trial, the information gathered can help others and add to scientific knowledge.
If you volunteer for a clinical trial, the research will be explained to you in detail. You'll learn about treatments and tests you may receive, and the benefits and risks they may pose. You'll also be given a chance to ask questions about the research. This process is called informed consent.
If you agree to take part in the trial, you'll be asked to sign an informed consent form. This form is not a contract. You have the right to withdraw from a study at any time, for any reason. Also, you have the right to learn about new risks or findings that emerge during the trial.
For more information about clinical trials related to obesity hypoventilation syndrome, talk with your doctor. You can visit the following Web sites to learn more about clinical research and to search for clinical trials:
For more information about clinical trials for children, visit the NHLBI's Children and Clinical Studies Web page.
The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.