Dynamics of soft palate and uvula in OSAHS during sleep

Objectives: To study the dynamic motion of soft palate and uvula in patients with obstructive sleep apnea hypopnea syndrome (OSAHS) during sleep and wakefulness with ultrafast MR imaging. Methods: Ultrafast MRI was carried out in the upper airway in 15 patients during sleeping and awake after being deprived of sleeping for one night. Sequential midline sagittal images of the upper airway were obtained and displayed in the cine mode in PACK system. The length from the centre of soft palate to the X axis(the prolonged line of the hard palate)was defined as PX; the length from uvular tip to the X axis was UX; the length from the centre of soft palate to the Y axis(a perpendicular line from the centre of pituitary to the X axis)was PY; the length from uvula tip to the Y axis was UY;the differences of the maximal and the minimal of these lengths were measured. Results: The minimal lengths of UX and UY during sleeping were shorter than those during wakefulness(P<0.01), The maximal UX and UY during sleeping were longer than those during wakefulness(P<0.01). The minimal lengths of PX and PY during sleeping were shorter than those during wakefulness (P<0.01), The maximal PX and PY during sleeping were longer than those during wakefulness(P<0.01). The differences of the maximal and the minimal of UX,UY,PX,PY during sleeping were bigger than those during wakefulness(P<0.01). Conclusions: During sleep, the uvular tip and the soft palate in OSAHS group are in violent dynamic motion in every direction, and their compliance is increased. It may be the trigger for obstructive episodes.