What is Obesity Hypoventilation Syndrome (OHS)

Obesity hypoventilation syndrome means that you are not breathing well enough to get air in and out of your lungs efficiently (ventilation).

This causes a low oxygen level and a high carbon dioxide level in your blood (hypoventilation). Having too much total body fat (obesity) is a significant risk factor for developing OHS.

OHS makes it harder for your heart to pump oxygen-rich blood to your body. It can cause sleep disturbances and make you feel sleepy during the day. Over time, OHS can increase your risk for:

• Heart disease.
• High blood pressure (hypertension).
• Reduced ability to absorb sugar from the bloodstream (insulin resistance).
• Heart failure. Over time, OHS weakens your heart and can lead to heart failure.

What are the causes?

The exact cause of OHS is not known. Possible causes include:

• Pressure on the lungs from excess body weight.
• Obesity-related changes in how much air the lungs can hold (lung capacity) and how much they can expand (lung compliance).
• Failure of the brain to regulate oxygen and carbon dioxide levels properly.
• Chemicals (hormones) produced by excess fat cells interfering with breathing regulation.
• A breathing condition in which breathing pauses or becomes shallow during sleep (sleep apnea). This condition can eventually cause the body to ventilate poorly and to hold onto carbon dioxide during the day.

What increases the risk?

You may have a greater risk for OHS if you:

• Have a BMI of 30 or higher. BMI is an estimate of body fat that is calculated from height and weight. For adults, a BMI of 30 or higher is considered obese.
• Are 40‒60 years old.
• Carry most of your excess weight around your waist.
• Experience moderate symptoms of sleep apnea.

What are the signs or symptoms?

The most common symptoms of OHS are:

• Daytime sleepiness.
• Lack of energy.
• Shortness of breath.
• Morning headaches.
• Sleep apnea.
• Trouble concentrating.
• Irritability, mood swings, or depression.
• Swollen veins in the neck.
• Swelling of the legs.

How is this diagnosed?

Your health care provider may suspect OHS if you are obese and have poor breathing during the day and at night. Your health care provider will also do a physical exam. You may have tests to:

• Measure your BMI.
• Measure your blood oxygen level with a sensor placed on your finger (pulse oximetry).
• Measure blood oxygen and carbon dioxide in a blood sample.
• Measure the amount of red blood cells in a blood sample. OHS causes the number of red blood cells you have to increase (polycythemia).
• Check your breathing ability (pulmonary function testing).
• Check your breathing ability, breathing patterns, and oxygen level while you sleep (sleep study).

You may also have a chest X-ray to rule out other breathing problems. You may have an electrocardiogram (ECG) and or echocardiogram to check for signs of heart failure.

How is this treated?

Weight loss is the most important part of treatment for OHS, and it may be the only treatment that you need. Other treatments may include:

• Using a device to open your airway while you sleep, such as a continuous positive airway pressure (CPAP) machine that delivers oxygen to your airway through a mask.
• Surgery (gastric bypass surgery) to lower your BMI. This may be needed if:
  • You are very obese.
  • Other treatments have not worked for you.
  • Your OHS is very severe and is causing organ damage, such as heart failure.

Follow these instructions at home:

Medicines

• Take over-the-counter and prescription medicines only as told by your health care provider.
• Ask your health care provider what medicines are safe for you. You may be told to avoid medicines that can impair breathing and make OHS worse, such as sedatives and narcotics.

Sleeping habits

• If you are prescribed a CPAP machine, make sure you understand and use the machine as directed.
• Try to get 8 hours of sleep every night.
• Go to bed at the same time every night, and get up at the same time every day.

General instructions

• Work with your health care provider to make a diet and exercise plan that helps you reach and maintain a healthy weight.
• Eat a healthy diet.
• Avoid smoking.
• Exercise regularly as told by your health care provider.
• During the evening, do not drink caffeine and do not eat heavy meals.
• Keep all follow-up visits as told by your health care provider. This is important.

Contact a health care provider if:

• You experience new or worsening shortness of breath.
• You have chest pain.
• You have an irregular heartbeat (palpitations).
• You have dizziness.
• You faint.
• You develop a cough.
• You have a fever.
• You have chest pain when you breathe (pleurisy).