Study objectives: Obstructive sleep apnea (OSA)
is characterized by repetitive pharyngeal collapse during sleep.
Several techniques have been proposed to assess the collapsibility of
the upper airway in awake humans, but sleep-wake comparisons have
rarely been attempted and there are few studies comparing OSA patients
to control subjects. We sought to compare two collapsibility
measurement techniques between normal and apneic subjects, and between
wakefulness and sleep.
Design: We conducted three
studies. First, we examined whether collapsibility assessed by negative
pressure pulses (NPPs) during wakefulness reflected values during sleep
in 21 normal subjects. Second, we determined in these normal subjects
whether collapsibility during sleep assessed by NPPs was predictive of
collapsibility measured by inspiratory resistive loading (IRL).
Finally, we compared upper-airway collapsibility between apnea patients
(n = 22) and normal volunteers (n = 38) during wakefulness by
Setting: Clinical and research laboratories at
the Brigham and Women’s Hospital.
populations of normal subjects (n = 21 and n = 38) and OSA patients
(n = 22).
Measurements and results: Collapsibility
during wakefulness, as measured by NPPs, correlated significantly with
collapsibility during sleep (r = 0.62; p = 0.003).
There was also a significant correlation between the two measures of
collapsibility (IRL and NPP) during sleep (r = 0.53;
p = 0.04). Both measures revealed a significant increase in
pharyngeal collapsibility during sleep as compared to wakefulness.
Finally, apnea patients had significantly greater pharyngeal
collapsibility than control subjects during wakefulness
(p = 0.017).
Conclusions: These data suggest that
upper-airway collapsibility measured during wakefulness does provide
useful physiologic information about pharyngeal mechanics during sleep
and demonstrates clear differences between individuals with and without