What is sleep apnea?
Sleep apnea (apnoea in the United Kingdom) is a medical
disorder
in which someone stops breathing after falling asleep.
An apnea (or apneic event) is arbitrarily defined as
a cessation of airflow lasting at least ten seconds.
There are three types of sleep apnea:
obstructive, central, and mixed (which is a combination
of central and obstructive).
Obstructive Sleep Apnea
The most common form of sleep apnea, obstructive sleep
apnea
(OSA), is usually associated with snoring.
In OSA, the muscles of the upper airway (the back of the
throat)
relax, and the airway collapses, preventing air from being
drawn in.
This cessation of breathing causes the blood oxygen level to
fall,
which in turn causes the brain to send a signal that wakes
the sleeper.
Once the sleeper awakens enough for the airway to regain
muscle tone,
he or she is able to inhale.
This can happen repeatedly throughout
the sleep period.
Though the apnea sufferer does not remember
these awakenings
in the morning,
he or she has not had enough deep, uninterrupted sleep.
Central Sleep Apnea
In central sleep apnea, the brain fails to send the proper
signals
to the diaphragm and chest muscles.
The airway stays open, but the body "forgets" to breathe.
Central sleep apnea may be associated with
certain neurological
conditions or cardiopulmonary disorders.
As in OSA, when the blood oxygen level drops,
the brain sends a signal
waking the sleeper, which allows him or her to breathe
again.
Mixed Sleep Apnea
Mixed sleep apnea is a condition in which there are both
obstructive and central apneic events.
