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Obesity hypoventilation syndrome (OHS)

Obesity hypoventilation syndrome (OHS)


Pickwickian syndrome

Obesity hypoventilation syndrome (OHS) is a condition in some obese people in which poor breathing leads to lower oxygen and higher carbon dioxide levels in the blood.

I Would Like to Learn About:

  • Causes

    The exact cause of OHS is not known. Doctors believe OHS results from a defect in the brain's control over breathing and excess weight (due to obesity) against the chest wall. This makes it hard for a person to breathe deeply and quickly enough. As a result, the blood has too much carbon dioxide and not enough oxygen.

  • Symptoms

    The main symptoms of OHS are due to lack of sleep and include:

    • Poor sleep quality
    • Sleep apnea
    • Daytime sleepiness
    • Depression
    • Headaches

    Symptoms of low blood oxygen level (chronic hypoxia) can also occur. Symptoms include shortness of breath or feeling tired after very little effort.

  • Exams and Tests

    People with OHS are usually very overweight. A physical exam may reveal:

    • Bluish color in the lips, fingers, toes, or skin (cyanosis)
    • Reddish skin
    • Signs of right-sided heart failure (cor pulmonale), such as swollen legs or feet, shortness of breath, or feeling tired after little effort
    • Signs of excessive sleepiness

    Tests used to help diagnose and confirm OHS include:

    • Arterial blood gas
    • Chest x-ray or CT scan to rule out other possible causes
    • Lung function tests (pulmonary function tests)
    • Sleep study (polysomnography)

    Doctors can tell OHS from obstructive sleep apnea because a person with OHS has a high carbon dioxide level in the blood when awake.

  • Treatment

    Treatment involves breathing assistance using special machines (mechanical ventilation). Options include:

    • Noninvasive mechanical ventilation such as continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP) through a mask that fits tightly over the nose or nose and mouth (mainly for sleep)
    • Oxygen therapy
    • Breathing help through an opening in the neck (tracheostomy). Treatment is done in the hospital.

    Other treatments are aimed at weight loss, which can reverse OHS.

  • Outlook (Prognosis)

    Untreated, OHS can lead to serious heart and blood vessel problems, severe disability, or death.

  • Possible Complications

    Complications of OHS that have to do with a lack of sleep, such as:

    • Depression, agitation, irritability
    • Increased risk of accidents or mistakes at work
    • Problems with intimacy and sex 

    OHS can also cause heart problems, such as:

    • High blood pressure (hypertension)
    • Right-sided heart failure (cor pulmonale)
    • High blood pessure in the lungs (pulmonary hypertension)
  • When to Contact a Medical Professional

    Call your health care provider if you are very tired during the day or have any other symptoms that suggest OHS.

  • Prevention

    Maintain a healthy weight and avoid obesity.

Related Information

  Obstructive sleep ...Respiratory acidos...Skin discoloration...High blood pressur...     Obstructive sleep ...High blood pressur...


Duffin J, Phillipson EA. Hypoventilation and hyperventilation syndromes In: Mason RJ, Broaddus CV, Martin TR, et al., eds. Murray and Nadel's Textbook of Respiratory Medicine. 5th ed. Philadelphia, PA: Elsevier Saunders; 2010:chap 78.

Malhotra A. Disorders of ventilatory control. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 86.

Piper AJ, Grunstein RR. Obesity hypoventilation syndrome: mechanisms and management. Am J Respir Crit Care Med. 2011;183:292-298.


Review Date: 8/7/2013  

Reviewed By: Denis Hadjiliadis, MD, Assistant Professor of Medicine, Division of Pulmonary, Allergy and Critical Care, University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.

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