What is Sleep Apnea?
Sleep apnea is a condition in which one stops breathing while asleep. During sleep, your breathing is interrupted by repeated pauses known as apneic events.
How we breathe while sleeping?
With normal respiratory drive, after exhalation, the blood level of oxygen decreases and that of carbon dioxide increases. Exchange of gases with a lungful of fresh air is necessary to replenish oxygen and rid the bloodstream of built-up carbon dioxide. Oxygen and carbon dioxide receptors in the blood stream (chemo receptors) send nerve impulses to the brain, which then signals reflex opening of the larynx and movements of the rib cage muscles. These muscles expand the chest cavity so that a partial vacuum is made within the lungs and air rushes in to fill it.
Types of Sleep Apnea
The types of sleep apnea include: obstructive sleep apnea, which is the most common form of sleep apnea; central sleep apnea; and mixed (or complex) sleep apnea, which combines the two other types.
Sleep apnea is a killer disease and can cause many serious health problems. It can increase the risk for stroke, obesity, diabetes, heart attack, heart failure, irregular heartbeat, and high blood pressure. It may also increase the risk for accidents while working or driving, as some people with sleep apnea may fall asleep during those activities.
What Is Central Sleep Apnea?
In central sleep apnea, breathing is disrupted regularly during sleep because of the way the brain functions. It is not that you cannot breathe (which is true in obstructive sleep apnea); rather, you do not try to breathe at all. The brain does not tell your muscles to breathe. This type of sleep apnea is usually associated with serious illness, especially an illness in which the lower brainstem — which controls breathing — is affected.
In central sleep apnea, the basic neurological controls for breathing rate malfunction and fail to give the signal to inhale, causing the individual to miss one or more cycles of breathing.
In general, the main risk factors for sleep apnea are male, being overweight, and being over 40 years of age. However, anyone can have any of the types of sleep apnea.
Central sleep apnea is often associated with other conditions. One form of central sleep apnea, however, has no known cause and is not associated with any other disease. In addition, central sleep apnea can occur with obstructive sleep apnea, or it can occur alone.
Conditions that may be associated with central sleep apnea include the following:
• Congestive heart failure
• Hypothyroid Disease
• Kidney failure
• Neurological diseases, such as Parkinson’s disease, Alzheimer’s disease, and amyotrophic lateral sclerosis.
• Damage to the brainstem caused by encephalitis, stroke, injury, or other factors
What happens to breathing in Sleep Apnea?
During central apneas, the central respiratory drive is absent, and the brain does not respond to changing blood levels of the respiratory gases. No breath is taken despite the normal signals to inhale. The immediate effects of central sleep apnea on the body depend on how long the failure to breathe endures. At worst, central sleep apnea may cause sudden death.
Symptoms of Central Sleep apnea
The main symptom of central sleep apnea is temporary stoppages of breathing while asleep. Although snoring is a very strong symptom of obstructive sleep apnea, snoring is usually not found with central sleep apnea. The central sleep apnea is rare when compared to obstructive sleep apnea. The symptoms of central sleep apnea are for the most part the same as those of obstructive sleep apnea. They include chronic fatigue, daytime sleepiness, morning headaches and restless sleep. But if the cause is a neurological disease, the CSA sufferer may also experience difficulty swallowing, voice changes, and an overall sense of weakness and numbness.
If the pause in breathing is long enough, the percentage of oxygen in the circulation will drop to a lower than normal level and the concentration of carbon dioxide will build to a higher than normal level. Brain cells need constant oxygen to live, and if the level of blood oxygen goes low enough for long enough, the consequences of brain damage and even death will occur. Fortunately, central sleep apnea is more often a chronic condition that causes much milder effects than sudden death.
In any person, hypoxia and hypercapnia have certain common effects on the body. The heart rate will increase, unless there are such severe co-existing problems with the heart muscle itself or the autonomic nervous system that makes this compensatory increase impossible. The more translucent areas of the body will show a bluish or dusky, which is the change in hue that occurs owing to lack of oxygen in the blood (“turning blue”).
After taking a sleep history, overnight sleep study called a polysomnogram is conducted. This test is performed in a sleep lab or home under the direct supervision of a trained technologist. During the test, the following body functions may be monitored:
• Electrical activity of the brain
• Eye movements
• Muscle activity
• Heart rate
• Breathing patterns
• Air flow
• Blood oxygen levels
After the study is completed, the technologist will tally the number of times that breathing is impaired during sleep and then grade the severity of sleep apnea. In some cases, a multiple sleep latency test is performed on the day after the overnight test to measure how quickly you fall asleep. In this test, patients are given several opportunities to fall asleep during the course of a day when they normally would be awake.
Any individual, no matter how healthy, who is given enough of a central respiratory depressant drug, will develop apnea on a central basis. Generally, drugs that are sedative effects, alcohol, opiates can make central apnea worse.
Should these individuals have general anesthesia, for example, they require prolonged monitoring after initial recovery, as compared to a person with no history of sleep apnea, because apnea is likely to occur with even low levels of the drugs in their system.
Premature babies with immature brains and reflex systems are at high risk for central sleep apnea syndrome, even if these babies are otherwise healthy. Fortunately, those premature babies who have the syndrome will generally outgrow it as they mature, providing they receive careful enough monitoring and supportive care during infancy to survive. Because of the propensity toward apnea, medications that can cause respiratory drive depression are either not given to premature infants, or given under careful monitoring, with equipment for resuscitation immediately . Cot death or sudden deaths in infants are sometimes attributable to sleep apnea.
Central Apnea and Heart Diseases
Adults suffering from congestive heart failure are at risk for a form of central sleep apnea called Cheyne-Stokes respiration. This is periodic breathing with recurrent episodes of apnea alternating with episodes of rapid breathing. In those who have it, Cheyne-Stokes respirations occur while both awake and asleep. There is good evidence that replacement of the failed heart cures central apnea in these patients. The uses of some medications that are respiratory stimulants decrease the severity of apnea in some patients. There is an association between atrial fibrillation and central sleep apnea.
How Is Central Sleep Apnea Treated?
If central sleep apnea is associated with some other condition, such as congestive heart failure, that condition is treated.
Some of the more conservative treatments for obstructive sleep apnea would likely benefit people with central sleep apnea as well. Some of these conservative treatments include:
• Losing weight if necessary, and then maintaining a healthy weight
• Avoiding the use of alcohol and sleeping pills, as these items make the airway more likely to collapse during sleep
• Sleeping on your side if you have apneic events when sleeping on your back, possibly using pillows or other devices to keep you in place
• Using nasal sprays or breathing strips to keep air flowing if you have sinus problems or nasal congestion
• Avoiding sleep deprivation
Another treatment is continuous positive airway pressure (CPAP), which is the preferred initial treatment for most people with obstructive sleep apnea. The treatment has been beneficial in people with central sleep apnea, as well. This is especially true of people who have central sleep apnea associated with heart failure.
With CPAP, patients wear a mask over their nose and/or mouth. An air blower forces air through the nose and/or mouth. The air pressure is adjusted so that it is just enough to prevent the upper airway tissues from collapsing during sleep. The pressure is constant and continuous. CPAP prevents airway closure while it is being used, but apnea episodes return when CPAP is stopped or is used improperly. Other styles and types of positive airway pressure devices are available for people who have difficulty tolerating CPAP.
Treatment for central sleep apnea differs slightly in that the device is not set at one optimal constant pressure as with CPAP, but at two different settings for inhalation (IPAP) and for exhalation (EPAP), therefore aiding respiration. Other specifications, for instance the breathing rate and the duration of a single breath, can also be programmed. This device is called BiPAP (bi-level positive airway pressure, meaning it is set at two different pressures). Both CPAP and BiPAP devices can be connected to a humidifier to humidify and heat the inhaled air, thus reducing unpleasant symptoms such as a sore throat or blocked nose that can result from inhaling cold, dry air.