Dynamic alterations of soft palate in OSAHS during sleep

Objectives: To evaluate the dynamic changes of the soft palate and the uvular tip in patients with obstructive sleep apnoea hypopnea syndrome (OSAHS) during sleep and whilst awake by using Ultrafast Magnetic Resonance Imaging (UMRI).

Methods: Ultrafast MRI was undertaken on the upper airway in 15 patients whilst asleep and then whilst awake after being deprived of sleep for one night. A series of midline sagittal images of the upper airway were obtained. The distance from the center of the soft palate to the X axis (an extended line from the anterior nasal spine to posterior nasal spine) (PX); from the uvular tip to the X axis (UX); from the center of the soft palate to the Y axis (a perpendicular line from the center of the pituitary to the X axis) (PY) and from the uvular tip to the Y axis were measured during sleep and wakefulness. The maximal and minimal values of the above lengths and the differences between them were analyzed through Paired t-tests.

Results: The minimum lengths of PX, PY, UX and UY during sleep were less than those during wakefulness (P<0.01); the maximal lengths of PX, PY, UX and UY during sleeping were more than those during wakefulness (P<0.01). The differences between the maximal and minimal lengths of PX, PY, UX and UY during sleep were larger than those during wakefulness (P<0.01).

Conclusion: The ranges in the direction of upward, downward, forward and backward movements of the soft palate and the uvular tip during sleep were larger than those during wakefulness, and this increasing compliance may be the trigger for each obstructive event of the airway.