0449 Effect Of Neck-bending On Upper Airway (UA) Caliber And Surrounding Soft-tissues In Controls And Apneics

Abstract

Posture is a determinant of UA caliber and apnea frequency and severity. However, the effect of neck-bending on UA caliber and soft-tissues has not been well studied. We hypothesized that neck extension and flexion would increase and decrease UA caliber in controls and apneics. UA MRIs were obtained in 24 controls (AHI<5; 1.5 ± 1.5 events/hour) and 33 apneics (AHI≥5; 33.2 ± 28.7) during neck flexion, extension, and neutral position and analyzed for airway measures in the retropalatal (RP) and retroglossal (RG) regions and soft-tissue movement. Apneics were older (48.9 ± 11.9 vs. 40.8 ± 14.6, p=0.0256) and more obese (33.9 ± 4.4 vs. 28.4 ± 5.6 kg/m2, p=0.0001) than controls; subjects were 49.1% male. During extension (23.9 ± 14.9°) controls showed increased minimum cross-sectional area (CSA), anteroposterior (AP) and lateral dimension in the RP (CSA: 38.2mm2, p=0.0068; AP: 2.6mm, p=0.0145; lateral: 3.8mm, p=0.0046) and RG (CSA: 71.5mm2, p=0.0176; AP: 2.9mm, p=0.0029; lateral: 4.9mm, p=0.0120) airway relative to neutral. Apneics (19.7 ± 9.3°) showed increased RP (CSA: 16.8mm2, p=0.0021; lateral: 2.2mm, p=0.0009) and RG (CSA: 70.6mm2, p<0.0001; AP: 2.8mm, p=0.0001; lateral: 4.7mm, p<0.0001) measures. During flexion, both controls (-16.5 ± 8.2°) and apneics (-11.9 ± 5.7°) showed reduced RP lateral dimension (-2.2mm [p=0.0120] and -1.1mm [p=0.0245]) and RG CSA (-28.2mm2 [p=0.0072] and -12.3mm2 [p=0.0595]). Compared to extension, controls in flexion showed reduced RP (CSA: p=0.0011; AP: p=0.0030; lateral: p=0.0016) and RG (CSA: p=0.0033; AP: p=0.0010; lateral: p=0.0022) measures, RP lateral wall narrowing (p=0.0305), and greater posteroinferior movement of the soft palate (p=0.0019) and all tongue quadrants (p≤0.0042). Compared to extension, apneics in flexion showed reduced RP (CSA: p=0.0006; AP: p=0.0502; lateral: p<0.0001) and RG (CSA: p<0.0001; AP: p=0.0001; lateral: p<0.0001) measures, significant total lateral wall narrowing (p=0.0010), and greater posteroinferior movement of the soft palate (p=0.0005) and all tongue quadrants (p<0.0008). Controls and apneics showed reductions in both RP and RG airway caliber during neck flexion and increases during extension, primarily due to movement of surrounding soft-tissues. These data provide important insights into the role of head and neck position on UA caliber. Funded by NIH P01 HL094307.