However, there is another category of apnea that, while it's not as prevalent as OSA, is still dangerous if left undiagnosed and untreated.
What is Central Sleep Apnea (CA)?
While it is mechanical dysfunction in the upper airway that defines OSA, for CA, the dysfunction is not due to any obvious obstruction. Instead, the part of the brain which regulates breathing as you sleep fails to send the proper signals to the muscles of breathing and the diaphragm, instructing them to inhale and exhale.
How breathing works as you sleep
Breathing is a mechanical process that is informed by your body chemistry. If you have too much carbon dioxide in the bloodstream, the brain tells the lungs and their accessory muscles (the diaphragm below the lungs and the many muscles tucked inside the ribcage) to work in tandem to exhale the carbon dioxide.
Meanwhile, the cells in the body also need a steady supply of oxygen for proper function. When blood oxygen levels run low, the brain signals the lungs and their companion muscles to inhale. A complete inhale/exhale cycle represents the exchange of carbon dioxide from inside the body for oxygen externally available to the body. Oxygen in, carbon dioxide out.
While we are awake, our brain works with the lungs, the bloodstream, and these muscles to maintain normal breathing to ensure this gas exchange takes places. We don't even have to think about it. But if we wanted to, we could voluntarily take a deep breath, say, to blow up a balloon.
When we are asleep, however, we rely almost entirely on the brain to keep our breathing regular and our gas exchanges normal.
When CA strikes
In the situation when CA takes place, the signals we rely on from the brain to maintain regular breathing simply don't work.
Without these signals, the muscles are inactive and the body essentially stops breathing until the oxygen levels in the bloodstream fall. When this happens, low oxygen/high carbon dioxide "alarms" go off in the brain. Its respiratory regulators, sensing these alarms, "wake up" and send new signals to the breathing muscles to start inhaling again to correct the imbalance and resume normal gas exchange.
CA can happen singularly and randomly as a kind of "technical" glitch that originates in the brain, but more often, it occurs in a series of repetitive events that create dysfunctional breathing patterns that are unhealthy.
One is called periodic breathing. Periodic breathing indicates a pattern in which shallow breathing (apnea) occurs, which starves the bloodstream of oxygen until a more robust breathing pattern resumes, usually in an extreme effort (hyperventilation), to replace depleted oxygen and release unhealthy levels of carbon dioxide from the bloodstream.
This stressful roller coaster of "flat breathing" horizons, followed by "extreme breathing" peaks and valleys sets the stage for chronic health problems if it's not treated.
Another breathing pattern that indicates CA is Cheyne-Stokes breathing (see left), a distinctive wax-and-wane respiration in which complete cessations in breathing take place between periods of hyperventilation in a repeated sequence.
What causes Central Sleep Apnea?
There are a number of health conditions and situations which can present with CA, such as:
Congestive heart failure
Sleeping at a high altitude
The presence of a brain tumor
Diseases of and injuries to the breathing center in the brain
Severe arthritis with cervical spine degeneration near the base of the skull
Use of certain medications, such as opioids or codeine sulfate, which can depress respiratory function
- Complex Sleep Apnea Syndrome, in which people suffer from a combination of OSA and CA, often in people who use continuous positive airway pressure (CPAP) to treat their OSA
In every case, the missed signals from the brain are always at the root of the condition.
Risk factors for developing CA include gender (it' s more common in males) and age (it's more common among people over age 65). It is estimated that at least 20 percent of all cases of sleep apnea are CA.
How is Central Sleep Apnea diagnosed?
An overnight attended sleep study is the best way to identify the presence of CA. Instruments that help differentiate a CA from an episode of OSA include respiratory belts, which measure the breathing effort in the chest and abdomen; airflow sensors to detect the presence or absence of oxygen flow near the nose and mouth; and a finger probe pulse oximeter, which reveals the levels of oxygen in the blood stream at any given time and captures significant drops caused by breathing cessation.
How is Central Sleep Apnea treated?
Because the relationship between CA and heart problems is serious and significant, coordination between your sleep physician and a cardiologist is a common approach for managing treatment.
Therapies include the aforementioned CPAP, which works for some patients; bilevel positive airway pressure (BPAP), which allows for more precise control over and support for pressures assigned to assist both inhalation and exhalation; and a "smart" noninvasive treatment similar to CPAP called adaptive servo-ventilation (ASV), which monitors the patient's breathing patterns, using extra pressure, sometimes with extra oxygen, to normalize breathing. There are also drugs that can be used for certain patients.
If you have been diagnosed with CA, the best therapy for you is going to be based on your history, symptoms, preexisting medical conditions, medications, and other factors. Your sleep physician should review your options with you upon diagnosis to help you arrive at your best course of treatment.
Please reach out to us at Sound Sleep Health if you have concerns about sleeping problems, for yourself or for a loved one. We have 3 locations in the greater Seattle/Kirkland areas. Call us so we can work together to Improve Your Sleep Today!