MRI STUDY OF REGIONAL VARIATIONS OF PHARYNGEAL WALL COMPLIANCE IN CATS

Upper airway compliance indicates the potential of the airway to colla pse and is relevant to the pathogenesis of obstructive sleep apnea. We hypothesized that compliance would vary over the rostral-to-caudal ex tent of the pharyngeal airway. In a paralyzed isolated upper airway pr eparation in cats, we controlled static upper airway pressure during m agnetic resonance imaging (MRI, 0.391-mm resolution). We measured cros s-sectional area and anteroposterior and lateral dimensions from three -dimensional reconstructed MRIs in axial slices orthogonal to the airw ay centerline. High-retropalatal (HRP), midretropalatal (MRP), and hyp opharyngeal (HYP) regions were defined. Regional compliance was signif icantly increased from rostral to caudal regions as follows: HRP < MRP < HYP (P < 0.0001), and compliance differences among regions were dir ectly related to collapsibility. Thus our findings in the isolated upp er airway of the cat support the hypothesis that regional differences in pharyngeal compliance exist and suggest that baseline regional vari ations in compliance and collapsibility may be an important factor in the pathogenesis and treatment of obstructive sleep apnea.