Obesity hypoventilation syndrome (OHS)

Obesity hypoventilation syndrome (OHS)

Definition:

Obesity hypoventilation syndrome (OHS) is a condition related to obstructive sleep apnea in which a very obese person does not breathe a sufficient amount of oxygen during sleep or while awake.

Alternative Names:

Pickwickian syndrome

Causes, incidence, and risk factors:

The cause of OHS in unknown, but it is likely to involve a combination of a disorder of the brain's control over breathing and the effects of massive obesity on the chest wall. With the excess weight of massive obesity, the muscles of the chest wall can have difficulty expanding the thorax enough to exchange air efficiently.

This results in a decreased ability to oxygenate the blood and retention of carbon dioxide (see respiratory acidosis). Affected individuals suffer from chronic fatigue. This is from sleep loss, poor sleep quality, as well as chronic hypoxia (decreased blood oxygen).

Morbid (massive or excessive) obesity is the main risk factor.

Symptoms:

The main symptoms of OHS are due to sleep deprivation, which results from sleep loss and poor sleep quality (see obstructive sleep apnea).

Excessive daytime sleepiness
Falling asleep at inappropriate times during the day
Increased risk for accidents or errors at work
Depression

In addition, symptoms of chronic hypoxia (low blood oxygen level) can also occur, such as shortness of breath or fatigue after minimal physical effort.

Signs and tests:

Persons with OHS are usually very overweight. Physical signs that suggest OHS include:

Cyanosis (bluish coloration of the lips, fingers, toes, or skin)
Signs of right heart failure (cor pulmonale), including:
- Swollen legs or feet
- Shortness of breath or easy fatigue on minimal effort

Tests done to confirm the diagnosis include:

Arterial blood gas
Sleep study

Treatment:

The treatment involves mechanical ventilation to provide enough breathing for the affected person. Options include:

Non-invasive mechanical ventilation (BiPAP or other modes) through a mask that fits tightly over the nose or nose and mouth
Mechanical ventilation through a tracheostomy

Other therapies are aimed at weight loss, which may lead to reversal of the OHS.

Support Groups:

Support groups may help patients with OHS, or their family members, adjust to the lifestyle changes that are required for successful treatment. In addition, support groups may provide information about new treatments that are developed.

Expectations (prognosis):

When treated, OHS has a good prognosis. Untreated, it can lead to serious cardiovascular complications, severe disability or death.

Complications:

Complications of OHS include complications of excessive sleepiness, such as:

Increased risk for accidents
Depression, agitation, irritability
Sexual dysfunction

OHS may also include cardiovascular complications, such as

Hypertension
Cor pulmonale (right heart failure)

Calling your health care provider:

Call your health care provider if you experience excessive daytime sleepiness, or any other symptoms that suggest OHS.

Prevention:

Prevention is avoiding excessive obesity.

Review Date: 1/26/2002
Reviewed By: David A. Kaufman, M.D., Pulmonary & Critical Care Medicine, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.

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