Apneas are defined as pauses in breathing of more than 10 seconds while asleep. These occur at regular intervals throughout the night. The subject is rarely aware of their difficulty breathing even upon awakening, and the condition may go undetected for years until spotted by someone else, or detected during a sleep study. Central sleep apnea differs from obstructive sleep apnea in that there is no ‘central’ attempt made to breath, whereas in OSA, the breaths are hampered by a physical blockage. In mixed sleep apnea, there is a transition between both forms.
Central sleep apnea is largely caused by an imbalance in the brain and central nervous system during sleep. The brain monitors all blood oxygen levels, and in most people this function ensures consistent intake of oxygen and outtake of carbon dioxide. In central sleep apnea, the brain does not react quickly enough to changes in these levels in the body while sleeping, and is forced to overcompensate afterwards, resulting in long missed breaths, followed by short rapid breaths.
In extreme cases where the apneas are long enough to severely lower the level of oxygen in the blood stream, central sleep apnea can lead to brain damage or even sudden death. Central sleep apnea can also exacerbate other disorders. People suffering epilepsy may be prone to seizures due to hypoxia (a lack of oxygen in the blood stream), even if taking medication to control seizures. Seizures may also occur in subjects without epilepsy. Increased carbon dioxide levels (hypercapnia) over a long period of undetected central sleep apnea can raise the pH balance of the blood enough to lead to metabolic acidosis. Hypoxia can also lead to heart attacks, angina or arrhythmias in subjects with coronary heart disease.
A sub class of central sleep apnea is Cheyne-Stokes respiration. This is similar to central sleep apnea in that the brain reacts slowly to changes in the blood oxygen level, and must rapidly compensate after. This condition is typically found in subjects with congestive heart failure, strokes or brain tumours. It can also occur with people with no prior history of the problem when sleeping at high altitudes, and is a signal of altitude sickness.
Detecting CSA in the absence of a bed partner should be centered on recognizing common symptoms and warning signs of CSA. Common symptoms include poor sleep with consistent awakenings, occasional shortness of breath when waking, difficulty falling asleep, and excessive sleepiness during the day. Those with a bed partner should be able to detect CSA much easier, as the partner will be able to easily detect the apneas, which can last as long as 15-20 seconds.
Daytime sleepiness will be common for anyone suffering with CSA. Apneas will often cause short awakenings which the subject likely won’t be aware of. This can happen as many as 100 times a night, and severely disrupts sleep, often preventing the individual from attaining deep, regenerative sleep.
If suspected, a sleep specialist should be consulted, and an overnight sleep study obtained. The polysomnogram will clearly show the frequency and duration of the apneas, as well as the corresponding drop or rise in oxygen and carbon dioxide levels. This will not only identify the problem, but also give immediate feedback to the doctors on how serious the condition is, and what methods of treatment should be implemented. Other conditions that may be causing the central sleep apnea may also come to light during this process, so care should be given to ensure all avenues are explored.
Treatment of central sleep apnea is often determined by the cause of the events. One popular treatment is positive airway pressure (PAP). Continuous PAP (CPAP) or Bilevel PAP may be used. A relatively new PAP, adaptive servo ventilation (ASV) has recently demonstrated beneficial response for patients with central sleep apnea.
If drugs or drug abuse is causing the CSA, a switch in medications and/or a refrain from drug use may be necessary.
Reviewed September, 2007