IADR Abstract Archives
How Should We Measure the Upper Airway?
Objectives: The diagnosis of sleep-disordered breathing should be done only by a sleep physician. At the same time, CBCT taken for orthodontic diagnosis often encompass the upper airway (UA), thus offering a valuable tool to assess UA morphology. The aims of this study is to define how to measure UA: in details, which measurements should be considered, how reproducible they are also in respect to head posture, and which are the differences between the various measurements, and their implications to airflow in the UA.
Methods: CBCT-scans from 10 subjects and MRI-scans from 10 volunteers were analysed, and the UA was segmented using a manual threshold approach. Total volume and partial volumes of the nasal cavity and pharyngeal airway (PA) were assessed, and the cross-sectional areas and hydraulic diameters were calculated based on the PA centerline. The influence of head posture during image acquisition on UA volumes was also assessed.
Results: Measurements of the UA are reliable both at intra- and inter-examiner levels (minimal ICC, 0.960). Measuring the UA volume(s) alone do not depict the true morphology of UA. Similarly, cross sections cannot illustrate the areas characterized by a higher resistance to airway flow, whilst the hydraulic diameter seems to be a better predictor. Compared to normal head posture, head extension and flexion were associated with significant UA volume increment (p=0.02) and reduction (p=0.005), respectively.
Conclusions: Measuring the UA is not trivial. By following a standardized procedure and applying a manual threshold, the UA can be reliably segmented and measured. Using the centreline as a reference, the cross section together with the hydraulic diameter can accurately characterize the UA morphology. Yet, head posture should be standardized during image acquisition as an altered position greatly influences the measurements of UA.
Methods: CBCT-scans from 10 subjects and MRI-scans from 10 volunteers were analysed, and the UA was segmented using a manual threshold approach. Total volume and partial volumes of the nasal cavity and pharyngeal airway (PA) were assessed, and the cross-sectional areas and hydraulic diameters were calculated based on the PA centerline. The influence of head posture during image acquisition on UA volumes was also assessed.
Results: Measurements of the UA are reliable both at intra- and inter-examiner levels (minimal ICC, 0.960). Measuring the UA volume(s) alone do not depict the true morphology of UA. Similarly, cross sections cannot illustrate the areas characterized by a higher resistance to airway flow, whilst the hydraulic diameter seems to be a better predictor. Compared to normal head posture, head extension and flexion were associated with significant UA volume increment (p=0.02) and reduction (p=0.005), respectively.
Conclusions: Measuring the UA is not trivial. By following a standardized procedure and applying a manual threshold, the UA can be reliably segmented and measured. Using the centreline as a reference, the cross section together with the hydraulic diameter can accurately characterize the UA morphology. Yet, head posture should be standardized during image acquisition as an altered position greatly influences the measurements of UA.