Upper airway size during tidal breathing

Dynamic changes in cross-sectional area at midtonsillar level (level 2) during tidal breathing of control subjects (top panels); and in subjects with obstructive sleep apnea (bottom panels), with 5-vol increments of inspiration (Ins) and 5-vol increments of expiration (Exp). Note the differences in anteroposterior (A-P) and lateral airway dimension.