Obesity hypoventilation syndrome
Obesity hypoventilation syndrome | |
---|---|
Other names | Pickwickian syndrome |
Respirology | |
Risk factors | Obesity |
Obesity hypoventilation syndrome (OHS) is a condition in which severely overweight people fail to breathe rapidly or deeply enough, resulting in low oxygen levels and high blood carbon dioxide (CO2) levels. The syndrome is often associated with obstructive sleep apnea (OSA), which causes periods of absent or reduced breathing in sleep, resulting in many partial awakenings during the night and sleepiness during the day.[1] The disease puts strain on the heart, which may lead to heart failure and leg swelling.
Obesity hypoventilation syndrome is defined as the combination of obesity and an increased blood carbon dioxide level during the day that is not attributable to another cause of excessively slow or shallow breathing.[2]
The most effective treatment is weight loss, but this may require bariatric surgery to achieve.[3] Weight loss of 25 to 30% is usually required to resolve the disorder.[3] The other first-line treatment is non-invasive positive airway pressure (PAP), usually in the form of continuous positive airway pressure (CPAP) at night.[4][5] The disease was known initially in the 1950s, as "Pickwickian syndrome" in reference to a Dickensian character.[5]
Signs and symptoms
Most people with obesity hypoventilation syndrome have concurrent
The low oxygen level leads to physiologic constriction of the pulmonary arteries to correct ventilation-perfusion mismatching, which puts excessive strain on the right side of the heart. When this leads to right sided heart failure, it is known as
Mechanism
It is not fully understood why some obese people develop obesity hypoventilation syndrome while others do not. It is likely that it is the result of an interplay of various processes. Firstly, work of breathing is increased as
The blunted ventilatory response is attributed to several factors. Obese people tend to have raised levels of the hormone
Low oxygen levels lead to
The chronically low oxygen levels in the blood also lead to increased release of
Diagnosis
Formal criteria for diagnosis of OHS are:[4][5][11]
- Body mass index over 30 kg/m2 (a measure of obesity, obtained by taking one's weight in kilograms and dividing it by one's height in meters squared)
- Arterial carbon dioxide level over 45 arterial blood gasmeasurement
- No alternative explanation for hypoventilation, such as use of congenital central hypoventilation syndrome
If OHS is suspected, various tests are required for its confirmation. The most important initial test is the demonstration of elevated carbon dioxide in the blood. This requires an
To distinguish various subtypes,
To distinguish between OHS and various other lung diseases that can cause similar symptoms,
Classification
Obesity hypoventilation syndrome is a form of
Treatment
In people with stable OHS, the most important treatment is
While many people with obesity hypoventilation syndrome are cared for on an outpatient basis, some deteriorate suddenly and when admitted to the hospital may show severe abnormalities such as markedly deranged blood acidity (pH<7.25) or depressed
Positive airway pressure
Positive airway pressure, initially in the form of continuous positive airway pressure (CPAP), is a useful treatment for obesity hypoventilation syndrome, particularly when obstructive sleep apnea coexists. CPAP requires the use during sleep of a machine that delivers a continuous positive pressure to the airways and preventing the collapse of soft tissues in the throat during breathing; it is administered through a mask on either the mouth and nose together or if that is not tolerated on the nose only (nasal CPAP). This relieves the features of obstructive sleep apnea and is often sufficient to remove the resultant accumulation of carbon dioxide. The pressure is increased until the obstructive symptoms (snoring and periods of apnea) have disappeared. CPAP alone is effective in more than 50% of people with OHS.[5]
In some occasions, the oxygen levels are persistently too low (
Other treatments
People who fail first-line treatments or have very severe, life-threatening disease may sometimes be treated with
Prognosis
Obesity hypoventilation syndrome is associated with a reduced
Those with abnormalities severe enough to warrant treatment have an increased risk of death reported to be 23% over 18 months and 46% over 50 months. This risk is reduced to less than 10% in those receiving treatment with PAP. Treatment also reduces the need for hospital admissions and reduces healthcare costs.[5]
Epidemiology
The exact prevalence of obesity hypoventilation syndrome is unknown, and it is thought that many people with symptoms of OHS have not been diagnosed.[4] About a third of all people with morbid obesity (a body mass index exceeding 40 kg/m2) have elevated carbon dioxide levels in the blood.[5]
When examining groups of people with obstructive sleep apnea, researchers have found that 10–20% of them meet the criteria for OHS as well. The risk of OHS is much higher in those with more severe obesity, i.e. a body mass index (BMI) of 40 kg/m2 or higher. It is twice as common in men compared to women. The average age at diagnosis is 52. American Black people are more likely to be obese than American whites, and are therefore more likely to develop OHS, but obese Asians are more likely than people of other ethnicities to have OHS at a lower BMI as a result of physical characteristics.[5]
It is anticipated that rates of OHS will rise as the prevalence of obesity rises. This may also explain why OHS is more commonly reported in the United States, where obesity is more common than in other countries.[5]
History
The discovery of obesity hypoventilation syndrome is generally attributed to the authors of a 1956 report of a professional poker player who, after gaining weight, became somnolent and fatigued and prone to fall asleep during the day, as well as developing edema of the legs suggesting heart failure. The authors coined the condition "Pickwickian syndrome" after the character Joe from Dickens' The Posthumous Papers of the Pickwick Club (1837), who was markedly obese and tended to fall asleep uncontrollably during the day.[14] This report, however, was preceded by other descriptions of hypoventilation in obesity.[5][15] In the 1960s, various further discoveries were made that led to the distinction between obstructive sleep apnea and sleep hypoventilation.[16]
The term "Pickwickian syndrome" has fallen out of favor because it does not distinguish obesity hypoventilation syndrome and sleep apnea as separate disorders (which may coexist).[16][17]
References
- ^ Casey KR, Cantillo KO, Brown LK. Sleep-related hypoventilation/hypoxemic syndromes. Chest. 2007;131(6):1936-48.
- ^ American Academy of Sleep Medicine. International Classification of Sleep Disorders. 3rd ed. Darien, IL: American Academy of Sleep Medicine; 2014.
- ^ PMID 31368798.
- ^ S2CID 37801868.
- ^ PMID 17934118. Archived from the originalon 2008-12-08. Retrieved 2008-11-22.
- ISBN 978-0-7020-2510-5.
- ISBN 978-0-07-139140-5.
- ISBN 978-0-8247-9899-4.
- ISBN 978-0-397-50999-7.
- ^ S2CID 32488927.
- ^ PMID 10450601.
- PMID 18250215.
- ^ Martin TJ, Badr M Safwan, and Finlay G. Treatment and prognosis of the obesity hypoventilation syndrome. UpToDate Aug 6, 2019. https://www.uptodate.com/contents/treatment-and-prognosis-of-the-obesity-hypoventilation-syndrome
- PMID 16353591.
- PMID 13263434.
- ^ PMID 16284108.
- PMID 16353586.
Further reading
- Mokhlesi, B; Masa, JF; Brozek, JL; Gurubhagavatula, I; Murphy, PB; Piper, AJ; Tulaimat, A; Afshar, M; Balachandran, JS; Dweik, RA; Grunstein, RR; Hart, N; Kaw, R; Lorenzi-Filho, G; Pamidi, S; Patel, BK; Patil, SP; Pépin, JL; Soghier, I; Tamae Kakazu, M; Teodorescu, M (1 August 2019). "Evaluation and Management of Obesity Hypoventilation Syndrome. An Official American Thoracic Society Clinical Practice Guideline". American Journal of Respiratory and Critical Care Medicine. 200 (3): e6–e24. PMID 31368798.