[Obstructive site of the upper airway in patients with obstructive sleep apnea hypopnea syndrome: analysis of dynamic MRI].

OBJECTIVE: To investigate the obstructive site and the dynamic change of the upper airway in patients with obstructive sleep apnea hypopnea syndrome (OSAHS) during sleep and wakefulness. METHODS: After being deprived of sleeping for 20 hours, sequential midline sagittal images of the upper airway were obtained in 21 patients during sleep and wakefulness with dynamic MRI. The obstructive state was studied according to hypopnea (< 10 s) and apnea (> or = 10 s). The length of obstruction site was measured and the dynamic characteristics of obstruction was observed. Statistical analysis was performed with paired t-test. RESULTS: The obstruction at the level of the palatopharynx in patients with hypopnea during wakefulness was similar to that in patients with apnea during sleep. The maximal length [(6.61 +/- 1.23) cm], the minimal length [(0.95 +/- 0.22) cm] and maximal length difference [(5.66 +/- 1.27) cm] related to apnea during sleep were longer than those correlated with hypopnea [(2.99 +/- 0.51) cm, (0.72 +/- 0.23) cm, (2.27 +/- 0.67) cm, respectively] in wakefulness. (P < 0.01). CONCLUSIONS: The obstruction of upper airway during sleep is dynamic and multilevel in patients with OSAHS. To a certain degree, hypopnea during wakefulness can give a clue to the obstructive state during sleep.