Sleep-related hypoventilation is a breathing-related disorder that interrupts normal sleep. This condition may be diagnosed when all other sleep disorders have been ruled out, though it may appear simultaneously with other sleep disorders. Sleep-related hypoventilation can be due to shallow breathing, obstructed airways, or damaged lungs. Sleep-related hypoventilation can occur independently or, more commonly, with other medical or neurological disorders, substance abuse, or even the routine use of prescribed medications.
Sleep-related hypoventilation can occur in anyone, at any age, even in babies and young people. Because many different underlying conditions can contribute to sleep-related hypoventilation, the signs and symptoms can vary from person to person. The most common symptoms include:
- Daytime sleepiness
- Frequent awakenings during sleep
- Morning headaches
- Stomach problems
- Reduced exercise capacity.
A significant number of people with sleep-related hypoventilation experience few or no symptoms, or have only mild symptoms in early stages, and may not realize they have a potentially progressive condition. Early-stage sleep-related hypoventilation can progress to a more serious chronic hypoventilation disorder, and lead to more serious health problems, including heart failure, respiratory failure, and brain and blood disorders
Normal breathing is restricted in someone with sleep-related hypoventilation, resulting in low levels of oxygen and elevated levels of carbon dioxide in the blood. Retention of carbon dioxide in the blood can lead to respiratory acidosis, or an elevated amount of acid in the bloodstream, and can interrupt cellular respiration.
Sleep-related hypoventilation is a reduced oxygen flow during sleep, while sleep apnea is the temporary cessation of breathing during sleep. They can occur simultaneously, and continuous positive airway pressure therapy (CPAP) machines can be used in the treatment of both.
Continual low blood oxygen content, or hypoxemia, can lead to pulmonary hypertension (high blood pressure), and neurocognitive disorders.
Multiple factors can lead to sleep-related hypoventilation, such as underlying medical, environmental, and genetic circumstances, including:
- Use of medications and other substances that suppress the central nervous system, such as benzodiazepines, opiates, and alcohol
- Neuromuscular and chest wall disorders
- Asthma or another pulmonary disorder
Obesity adds additional mass to the respiratory system and can reduce lung capacity, but it is not known yet with certainty why or to what degree obesity affects hypoventilation. Sleep-related hypoventilation in overweight individuals is often diagnosed separately as obesity hypoventilation syndrome (OHS).
The most effective test of sleep-related hypoventilation is polysomnography, or a sleep study. Polysomnography can be performed in a hospital or sleep center, and records a patient's brain waves, blood-oxygen level, heart rate, and breathing.
Sleep-related hypoventilation is typically treated by addressing any underlying conditions that may be causing hypoventilation, such as substance use. Weight loss may be advised, treatment may be prescribed to restore hormone levels in those with hypothyroidism, or medications known as respiratory stimulants may be used to treat narrowing of airways that can result from drug or alcohol use. If sleep apnea or another sleep disorder is also present, use of positive airway pressure devices, known as CPAP or BPAP machines, may be required to continually feed oxygen into the lungs while sleeping.