Objectives: In order to assess the relationship between upper airway obstruction pattern and the clinical characteristics of obstructive sleep apnea syndrome (OSAS), we evaluated dynamic changes in the pharyngeal airway of patients with the disorder by using ultrafast dynamic magnetic resonance imaging (MRI).
Methods: MRI while asleep was performed on 31 patients with OSAS (29 men, 2 women; mean age, 46.6+/-8.2 years; mean body mass index, 26.7+/-4.9kg/m(2); mean AHI, 40.6+/-21.7episodes/h). Relationships between obstruction pattern focusing on differences between single-site obstruction (SO) and multiple-site obstructions (MO) and titrated value of nasal CPAP in addition to respiratory variables were investigated.
Results: The velopharynx (VP) was the main obstructive site among most of the cases with SO (17 of 18 cases), and all of the cases with MO (n=13) showed obstruction at and below the VP. AHI was significantly higher in cases with MO than in those with SO (P<0.01). As for SaO(2) variables, minimum value during sleep was significantly lower and total time with SaO(2) pound90% was longer in cases with MO than in those with SO (P<0.05 each). Titrated value of n-CPAP was also significantly higher in cases with MO than in cases with SO (P<0.05).
Conclusions: Our results strongly suggest that formation of MO manifested on ultrafast dynamic MRI could be related to increased severity of the disorder. Considering the higher titrable value of CPAP, MO could be brought about by high pharyngeal pressure.