Alternative names
Obesity hypoventilation syndrome (OHS)

Definition

Obesity hypoventilation syndrome (OHS) is a condition related to (but can occur separately from) Obstructive sleep apnea. In OHS, a very obese person does not breathe a sufficient amount of oxygen during sleep or while awake.

Causes, incidence, and risk factors

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

This results in a decreased ability to oxygenate the blood, and the retention of carbon dioxide (see Respiratory acidosis). Affected individuals suffer from chronic fatigue due to sleep loss, poor sleep quality, and 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:       o Swollen legs or feet       o Shortness of breath or easy fatigue on minimal effort

Tests done to confirm the diagnosis include:

 
• Arterial blood gas  
• Sleep study  
• Pulmonary function

Treatment

The treatment involves mechanical ventilation to help the person breath. 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
Avoid Obesity.

Medical Encyclopedia

All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.