Continued from previous message on this subject...  :-)

   Ordinarily, as we breathe in, pressure within the upper portion
   of the airway, the part from the base of the tongue to just
   above the vocal cords, known as the oropharynx, is lower than
   the atmospheric pressure without.  Since this area has no bones
   or cartilage to provide support, its muscles, as well as those
   of the diaphragm and chest, must work together to hold it open.
   If these muscles fail to work, the oropharynx collapses.

   Since muscle tone drops during sleep, particularly during REM
   sleep, REM sleep is the time when problems involving muscle
   control are most likely to occur.  Relaxed muscles sag.  The
   narrower the airway, the more likely that sagging will lead
   to an obstruction.  Obesity, enlarged tonsils, chronic nasal
   congestion and congenital physical abnormalities set the scene
   for the development of upper-airway apnea.

   The muscle at the base of the tongue may also be involved in
   upper-airway apnea; this muscle's main job is to protrude the
   tongue to keep the airway open.  If the tone in this muscle
   falls abnormally low, the tongue may fall backward and partially
   or completely plug the airway.  Efforts of the diaphragm and
   chest muscles below will draw the tongue in tighter.  Sleeping
   posture makes things worse; if a sleeper were sitting up,
   gravity would make the tongue fall forward.

   The net effect of reduced muscle tone is that the upper airway
   acts like a floppy, soggy paper straw.  Trying to draw air from
   one end while the other is narrowed makes the sides stick
   together.

   This failure to coordinate muscles in order to safeguard the
   body during sleep is believed to stem from a defect not in the
   muscles but higher up, in the central nervous system.  One
   theory is that there are feedback loops involved in central
   control.  Frequent awakenings increase the need to sleep but
   also slow down muscle and nerve responses.  The poorly working
   muscles and nerves make the frequent awakenings inevitable, but
   at the same time, they make it harder and harder for the person
   to wake up.  It's a vicious circle.

   Genetics may play a role.  In one family, two sons and their
   father had apnea, while the child of a third son was a SIDS
   victim.  In this family, muscle activity of the tongue during
   sleep was abnormal.

   CENTRAL APNEA

   When the diaphragm and chest muscles stop working, causing
   central apnea, it takes drastic action--partial or full
   awakening--to get breathing started again.

   Harold, sixty-two, explains, "I just don't feel rested.  I
   can't seem to sleep the whole night through.  I wake up five,
   six, maybe ten times a night.  Sometimes, I can't seem to
   catch my breath.  I feel like I'm choking.  Just when I start
   to relax,  I feel my heart pounding.  I get kind of edgy."

   Frequent waking during the night prompts people with central
   sleep apnea to complain of trouble staying asleep--that is,
   insomnia.  Some, newly diagnosed at sleep disorders centers,
   say they have had insomnia for more than twenty years.

   Many such people had received an assortment of prescriptions
   for sleeping pills, without gaining relief.  Some had tried
   tranquilizers or alcohol in the hope of reducing the anxiety
   they presumed was waking them up.  However, since sleeping
   pills, tranquilizers and alcohol depress breathing, they not
   only can't help central apnea but may well make it worse.

   While people with central apnea may snore, their snoring isn't
   usually as loud or as repetitious as that of people with
   upper-airway apnea.  Like people with upper-airway apnea, those
   with central apnea may note loss of interest in sex, and men may
   have difficulty with erections.

   People with central apnea tend to be older than those with
   upper-airway apnea.  Central apnea is most frequent in people
   aged sixty and older.  Unlike upper-airway apnea, central apnea
   affects both sexes nearly equally.

   Central apnea also appears in people with diseases such as polio,
   or with spinal-cord injuries that have damaged or destroyed nerves.

   Since people with central apnea often breathe quite normally
   during the day [and don't necessarily snore... A.H.], establishing
   the reason for the frequent awakenings and other symptoms requires
   an evaluation during sleep.

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    - Origin: Paul's Waka Waka BBS 206-783-7979 Seattle, Wa. (1:343/117)



--- timEd/386 1.10.y2k+