Central Sleep Apnoea
There are many distinct and overlapping sleep disorders which involve breathing problems ocurring during sleep. One of these is central sleep apnoea, or CSA.
Overview
CSA is marked by a limitation or cessation of breathing while sleeping. The main difference between CSA and obstructive sleep apnoea (OSA) is that no obstruction exists in the airway. In CSA, the airway remains open but breathing is interrupted. In this condition, the "central" refers to the fact that the heart and the brain (which regulate breathing during sleep) are the culprits for the pause in breathing.
Because of the different causes, the body functions also differ in these two types of apnoea. While airflow flatlines in a similar way during CSA, the respiratory effort also flatlines in CSA, whereas during OSA abdominal and upper chest movements continue in OSA. The end of a CSA episode is quiet and gradual, while in OSA a gasp or snort signals the end.
Other features are similar betwen the two apnoeas, including a decrease in oxygen saturation, the presence of central hypopnoeas and central apnoeas, and arousals at the end of the episode. Snoring can be present in both conditions.
Causes
CSA can occur in a number of different forms, some of which have their own unique causes. The feature which unifys all CSAs is that the regulation of breathing in the person is malfunctioning, rather than the airway is being obstructed. In primary CSAs, the disrupted breathing pattern occurs repeatedly.
The specific cause of the CSA is rarely known, but it occurs more often in middle-aged or elderly men than in women of a similar age. Some CSAs also seem to be inherited. Other CSAs are caused by neurological conditions, such as Parkinson's disease.
What Happens During CSA
There are different variations of CSA. Cheyne-Stokes is a breathing pattern form of CSA defined by a choppy, rhythmic set of increases and decreases in breathing effort interspersed with central apnoeas. This type occurs mainly in men over the age of 60, particularly in those with congestive heart failure or who have experienced a stroke. It is rarely seen in women and it does not seem to be inherited.
CSA can be caused by other medical conditions, but without the typical Cheyne-Stokes breathing pattern it may be due to a problem in the base of the brain where the breathing is controlled. CSA can also be caused by kidney and heart problems, and more infrequently, by other medical conditions.
The drugs which can cause CSA are almost exclusively pain medications (opiates). The possibility of these medicines causing CSA increases with their prolonged use. In such cases, the breathing pattern can vary from complete apnoea to cyclic decreases and increases, or even elements of obstruction such as that seen in OSA.
High-altitude breathing is similar to the Cheyne-Stokes breathing pattern and is caused by being at high altitudes. Some people who regularly sleep at altitudes higher than about 4,500 metres (or 15,000 feet) can have this sleeping disorder. Anyone sleeping above 7,600 metres (or 25,000 feet) will also be affected. Men are more prone than women to develop this condition because they seem to be more responsive to changes in the level of carbon dioxide and oxygen in the blood.
Prevalence of CSA
CSA is far less common than OSA. Diagnostic sleep centers claim that only 5 to 10 percent of their patients have CSA, meaning that the overall prevalence in the population at large is probably less than 1 percent. CSA is rare in children and is typically associated with older adults.
Diagnosis
The diagnosis of CSA can only be accurately made through an overnight sleep study.
Treatments
The most widely-used and effective treatment for CSA is something called Positive Airway Pressure, or PAP. This can be accomplished through Continuous Positive Airway Pressure, or CPAP. This occurs through a mask worn over the nose or face. The air is gently blown into the back of the throat, thus allowing a continuous airflow while the individual is asleep.
Several different mask types are now available, and a person can choose the mask which provides the best comfort and fit for their face. If the person's home tends to be dry or the throat and nasal passages are dry after a CPAP treatment, a small, heated humidifier can be added to the CPAP machine. The CPAP unit is generally small enough to fit on a bedside stand or table and is about the size of a small fan. CPAP units also come with carrying cases so they can be taken along when the individual has to travel and sleep away from home.
Adaptive Servo-Ventilation (ASV) is a recent advancement in treating CSA and will no doubt be an important one. Supplemental oxygen is also sometimes used in treating various forms of sleep apnoeas. Changes in medication are frequently tried if a current medication is contributing to the apnoea situation.
References
- Lack, L. et al.(2003). Insomnia : how to sleep easy. Double Bay, N.S.W. : Media 21 Publishing.
- Servan-Schreiber, D. (2006). The Duke encyclopedia of new medicine : conventional and alternative medicine for all ages. London : Rodale.
- Vukovic, L. (2005). Overcoming sleep disorders naturally. Laguna Beach, CA : Basic Health.
- Wilfred, P. (2010). Sleepmanual : how to achieve the perfect night's sleep. London : New Holland.
Posted in Central Sleep Apnoea (CSA)
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