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The Different Types of Sleep Apnea
Sleep apnea is not the same in every sufferer. What a lot of people don't realize is that sleep apnea is divided into three different forms. So, just because you and your neighbor both suffer from sleep apnea, your treatment and/or symptoms may vary radically.
Obstructive Sleep Apnea
The most common form of sleep apnea is obstructive sleep apnea, accounting for approximately 85% of cases. Obstructive sleep apnea occurs when the throat muscles relax too much during sleep and the airway becomes almost fully closed, causing an airway blockage. As a result, the airflow that is received by the lungs is insufficient and breathing may stop for periods of ten seconds or more. When this occurs the body responds in a couple of ways. Brain activity will increase and the person will partially or fully wake up and start breathing properly again. The level of oxygen in the blood may also drop. Obstructive sleep apnea is well understood and the treatments available are usually very successful and only minimally invasive. For a detailed explanation of the various treatments for obstructive sleep apnea, read our article here.
Central Sleep Apnea
Central sleep apnea is the least common form accounting for only .4% of cases. This disorder is also referred to as Cheyne-Stokes respiration. Central sleep apnea is more a disorder of the brain, unlike obstructive sleep apnea which has a simpler, muscular origin.
In central sleep apnea the brain's control centers for respiration do not function properly. The neurological feedback mechanism that monitors the level of carbon dioxide in the blood fails in a patient with central sleep apnea. After exhaling, carbon dioxide levels in the body are higher and the brain is supposed to send a message to the respiratory system to inhale to restore the levels of oxygen. But in central sleep apnea the brain does not react to the carbon dioxide and so inhalation does not occur. During an apnea, if breathing pauses for long enough, the percentage of oxygen in the blood will drop below normal levels and the concentration of carbon dioxide will be elevated. After an episode of central sleep apnea, breathing may become faster for a few moments as the respiratory system tries to discard retained waste gases and absorb more oxygen.
Because blood cells need constant oxygen to survive, the damage to the brain can be significant if central sleep apnea is severe and goes untreated. At worst, central sleep apnea may cause sudden death. Seizures may be triggered by the lack of oxygen in the blood, and those with heart disease may suffer heart attacks. Central sleep apnea is most often found in heart disease patients, premature infants, people who have taken certain central respiratory depressing drugs, and it is also related to living at high altitude. Central sleep apnea is treated by treating the underlying condition that causes it to occur.
Mixed / Complex Sleep Apnea
The third type of sleep apnea is mixed or complex sleep apnea, which accounts for around 15% of cases. Complex sleep apnea is a combination of obstructive and central sleep apnea that usually occurs when obstructive sleep apnea is severe and longstanding. When this is the case, episodes of central apnea may develop. Research has not yet uncovered the cause of the loss of central respiratory drive during sleep in obstructive sleep apnea, but it could be related to carbon dioxide feedback malfunctions stemming from heart failure.
Complex sleep apnea has been described by researchers as a new presentation of sleep apnea. A patient with complex sleep apnea exhibits obstructive sleep apnea, but upon application of central positive airway pressure (CPAP) therapy, the patient exhibits persistent central sleep apnea. This has been shown to be the case in sleep studies, and has historically been managed either by CPAP or BiLevel therapy. Adaptive servo-ventilation modes of therapy have recently been introduced in an attempt to manage complex sleep apnea. Studies have demonstrated marginally superior performance of adaptive servo-ventilators in treating Cheynes-Stokes breathing. However, no long-term studies have been published, which suggest any differential outcomes versus standard CPAP therapy in treating complex sleep apnea with adaptive servo-ventilation therapy.
Regardless of type, the individual with sleep apnea is rarely aware of having difficulty breathing, even upon awakening. Sleep apnea is recognized as a problem by others witnessing the individual during episodes or is suspected because of its effects on the body. Symptoms may be present for years, even decades without identification, during which time the sufferer may become conditioned to the daytime sleepiness and fatigue associated with significant levels of sleep disturbance. A sleep study administered by a sleep doctor will identify what type of sleep apnea you have and how to proceed in treating it.