It's midnight and a loud rumble
breaks the silence, making the water glass on the nightstand
tremble. In California, this might presage an earthquake.
At 109 Aspen Ave, it means that Edwin Belhope, 47, is
snoring. Edwin suffers from obstructive sleep apnea (OSA).
Although it's a common condition, little is known about
it. A Canadian study in the September 1 issue of the American
Journal of Respiratory and Critical Care Medicine
sheds light on Ed's nocturnal condition. While small,
the study has important implications for upper airway
muscle regulation during sleep.
OSA patients commonly show inflammation
of the upper airway mucosa. Are they also at more risk
of injuring the muscle layer of the pharynx? A research
team headed by Dr R John Kimoff of the McGill University
Health Centre in Montreal set out to determine if pharyngeal
pressure changes and violent muscle contractions have
this effect in OSA patients. The team compared pharynx
muscle specimens from 11 OSA patients to those of seven
controls.
The muscle layer of OSA sufferers
had more inflammatory cells. This increase was largely
due to CD4+ and activated CD25+ T cells, which were
both elevated threefold in OSA patients. Inflammation
was also present in mucosal cells, with about three
times as many CD8+ T cells and CD25+ T cells in OSA
subjects. The fact that the different tissues had different
patterns of inflammation indicated to the researchers
that the muscle finding "is not simply spillover from
the adjacent mucosa."
Dr Kimoff and his colleagues also
found that OSA patients had a dramatic, nearly six-fold,
increase in intramuscular nerve fibers. This group also
showed denervation of the sarcolemmal membrane, which
covers the exterior of the muscle fibers.
The results of this study
suggest that inflammation and denervation affect not
only mucosal cells but upper airway muscles as well.
According to the researchers, this further compromises
pharangeal patency and "may have important implications
for the ability to generate adequate muscular dilating
forces during sleep."
|
