Types of Sleep Apnea

"There are three types of sleep apnea, central sleep apnea (CSA), obstructive sleep apnea (OSA), and mixed sleep apnea (both central sleep apnea and obstructive sleep apnea).

During sleep, the brain instructs the muscles of breathing to take a breath. Central sleep apnea (CSA) occurs when the brain does not send the signal to the muscles to take a breath, and there is no muscular effort to take a breath. Obstructive sleep apnea (OSA) occurs when the brain sends the signal to the muscles and the muscles make an effort to take a breath, but they are unsuccessful because the airway becomes obstructed and prevents the flow of air. The third type of sleep apnea, mixed sleep apnea, occurs when there is both central sleep apnea and obstructive sleep apnea.

What is central sleep apnea and what causes it?

Central sleep apnea (CSA) occurs when the brain does not send the signal to breathe to the muscles of breathing. This usually occurs in infants or in adults with heart disease, cerebrovascular disease, or congenital diseases but also can be caused by some medications and high altitudes.

Central sleep apnea may occur in premature infants (born before 37 weeks of gestation) or in full term infants. It is defined as apneas lasting more than 20 seconds, usually with a change in the heart rate, a reduction in blood oxygen, or hypotonia (general relaxation of the body's muscles). These children often will require an apnea monitor that sounds an alarm when apneas occur. Central sleep apnea is not the same thing as sudden infant death syndrome (SIDS).

Under normal circumstances, the brain monitors several things to determine how often to breathe. If it senses a lack of oxygen or an excess of carbon dioxide in the blood, it will speed up breathing. The increase in breathing increases the oxygen and decreases the carbon dioxide in blood. Some people with heart disease have an increase in carbon dioxide in their blood at all times. When there is a chronic (long term) increase in blood carbon dioxide, the brain starts to ignore the oxygen level and monitors the blood carbon dioxide level to determine when to take the next breath. The control of breathing also becomes slower to respond to changes in carbon dioxide levels. Thus, if a person takes more or deeper breaths and “blows off” carbon dioxide, the drive to breathe decreases, and the rate of breathing decreases. After a while, the carbon dioxide builds back up in the blood, and the rate of breathing increases. The brain, slow to adjust, continues to signal for more rapid breathing until the carbon dioxide level drops too low. Breathing then slows down or stops until the carbon dioxide level rises again. This pattern of abnormal breathing is called Cheyne-Stokes breathing (after the men who described it). It is characterized by repetitive cycles of fast breathing followed by slow breathing and apnea. This breathing pattern happens when the person is awake or asleep, but becomes more of a problem when asleep. Some patients with heart failure have central sleep apnea associated with a Cheyne-Stokes pattern of breathing..."

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