What Is Sleep-Related Hypoventilation?

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Sleep-related hypoventilation is breathing that is not sufficient during sleep. Breathing is either too shallow or too slow. Sleep-related hypoventilation is a category of disorders that have different underlying causes.

Overall, these disorders lead to an increase of carbon dioxide in the blood. This can potentially cause symptoms that include poor sleep quality, excessive daytime sleepiness, and morning headaches. However, some patients with these disorders do not have any symptoms. Learn more about this group of disorders in this article.

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What Is Sleep-Related Hypoventilation?

Sleep-related hypoventilation is one of four categories of sleep-related breathing disorders. The others are obstructive sleep apneas, central sleep apnea syndromes, and sleep-related hypoxemia disorder. 

Sleep-related hypoventilation disorders are characterized by insufficient ventilation, which leads to an increase of carbon dioxide levels in the arteries. Sometimes daytime (awake) hypoventilation is also present. There are six subtypes of disorders, which are due to a variety of causes.

Sleep-Related Hypoventilation Disorders

The six sleep-related hypoventilation disorders include: 

  • Obesity hypoventilation syndrome (OHS)
  • Congenital central alveolar hypoventilation syndrome (CCHS)
  • Late-onset central hypoventilation with hypothalamic dysfunction
  • Idiopathic central alveolar hypoventilation
  • Sleep-related hypoventilation due to a medication or substance
  • Sleep-related hypoventilation due to a medical disorder

Types and Their Causes

The six subtypes of sleep-related hypoventilation all have different mechanisms causing hypoventilation, or insufficient breathing. Most sleep-related hypoventilation cases are made up of either obesity hypoventilation syndrome or sleep-related hypoventilation due to a medication or medical condition. The other types are rarer.

Obesity Hypoventilation Syndrome (OHS)

OHS is present in some people who are obese, and it causes poor breathing leading to an increase in carbon dioxide in the blood. The specific cause of OHS is unknown, but experts believe it is due to both a defect in the brain and its control on breathing and excess weight on the chest that makes it difficult for the muscles to allow for proper breaths. 

Sleep-Related Hypoventilation Due to a Medication or Substance

Sleep-related hypoventilation can be provoked by drugs that cause a decrease in breathing and ventilation signals from the brain that impair muscle function. Some substances causing this are:

  • Long-acting narcotics
  • Anesthetics
  • Sedatives
  • Muscle relaxants
  • Alcohol  

Sleep-Related Hypoventilation Due to a Medical Disorder

This is diagnosed when patients have diseases of the lung tissue, airways, pulmonary blood vessels, or neurological or musculoskeletal disorders. 

Congenital Central Alveolar Hypoventilation Syndrome (CCHS)

Previously known as Ondine’s curse, CCHS usually starts in childhood. It is caused by a gene mutation. This mutation leads to a failure of the central respiratory drive (which controls the intensity of exhalation) and causes hypoventilation, which is more prominent during sleep. Sometimes it causes a person to stop breathing (respiratory arrest).

CCHS often is first detected in adulthood, occasionally being discovered after general anesthesia causes respiratory failure or severe respiratory illness, or after taking medications that cause a decrease in respiration. 

Late-Onset Central Hypoventilation with Hypothalamic Dysfunction

This disorder is related to the central control of breathing, which takes place within the central nervous system (which consists of the brain and spinal cord). This disorder causes hypoventilation during sleep. When patients have this disorder, they must have two of the following:

Idiopathic Central Alveolar Hypoventilation

Idiopathic central alveolar hypoventilation is diagnosed when other diseases, including other sleep-related hypoventilation disorders, are ruled out. The term idiopathic typically refers to an unknown cause. As such, there are still many questions related to this disorder that do not have answers.

Symptoms

While there are different causes of sleep-related hypoventilation, the buildup of carbon dioxide, called hypercapnia, can cause several symptoms including: 

Other consequences of chronic hypercapnia and hypoxemia (low oxygen blood levels) include pulmonary hypertension (high blood pressure affecting the lungs and heart) and heart enlargement and dysfunction. A physical exam might show excess fluid and laboratory tests may reveal elevated bicarbonate and polycythemia, which is increased red blood cells.

Diagnosis

Since there are many causes of sleep-related hypoventilation, a comprehensive assessment by a clinician is important. This could include taking a detailed history of sleep and sleep quality, and looking for the presence or absence of morning symptoms and daytime fatigue. An exam is also important to look for other medical conditions causing sleep-related hypoventilation and to rule out other potential contributing factors. 

The key characteristics of sleep-related hypoventilation that need to be monitored to make a diagnosis are respirations and carbon dioxide levels during sleep. The main test used for evaluating respirations during sleep is polysomnography (PSG), which is a sleep study. Given the nature of the conditions, it is recommended that this be performed in a sleep lab while being monitored and supervised by sleep medicine personnel.

What Does a Sleep Study Measure?

Polysomnography is a sleep study that records certain bodily functions and movements as you sleep or try to sleep. It records: 

  • Airflow in and out of your lungs as you breathe
  • Effort and rate of breathing
  • Level of oxygen in your blood
  • Body position
  • Brain waves, as shown on an electroencephalogram (EEG)
  • Muscle activity 
  • Eye movements
  • Heart rate

Carbon dioxide levels are measured through either a blood sample from an artery in the wrist or continuous monitoring of carbon dioxide levels exhaled while breathing.

Treatment

Treatment for sleep-related hypoventilation typically involves positive airway pressure (PAP) therapy using continuous positive airway pressure (CPAP) or noninvasive ventilation (NIV). They both provide oxygen through a mask worn when a person is asleep.

With CPAP, the air is at a constant pressure both when breathing in and breathing out. The commonly used form of NIV is BiPAP, which is bi-level PAP. This provides higher pressure when breathing in and lower pressure when breathing out.

Treatment will be determined on the underlying cause of the sleep-related hypoventilation, as well as the levels of carbon dioxide present in the blood.

A Word From Verywell

Sleep is essential for everybody. It affects your ability to function and live your life. However, sometimes you may notice difficulty sleeping or still feeling tired during the day. Many of the sleep-related disorders are treatable, and if you have concerns about your sleep quality, share them with your doctor.

Sleep-related hypoventilation can lead to complications, so it is important for your doctor to determine if you have this condition. A doctor will be able to perform an assessment and determine a diagnosis and treatment plan for you if necessary.

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