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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.
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.
The main symptoms of OHS are due to lack of sleep and include:
Symptoms of low blood oxygen level (chronic hypoxia) can also occur. Symptoms include shortness of breath or feeling tired after very little effort.
People with OHS are usually very overweight. A physical exam may reveal:
Tests used to help diagnose and confirm OHS include:
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 involves breathing assistance using special machines (mechanical ventilation). Options include:
Other treatments are aimed at weight loss, which can reverse OHS.
Untreated, OHS can lead to serious heart and blood vessel problems, severe disability, or death.
Complications of OHS that have to do with a lack of sleep, such as:
OHS can also cause heart problems, such as:
Call your health care provider if you are very tired during the day or have any other symptoms that suggest OHS.
Maintain a healthy weight and avoid obesity.
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.