Fig. 4From: Threshold of the upper airway cross-section for hypopnea onset during sleep and its identification under waking conditionThe shape change in the oropharynx cross-section of the upper airway after elevating the legs for 8 min. Compared to the control (a), the size of the airway in the anteroposterior direction decreased apparently, but the size in the transverse direction maintained almost unchanged after 8 min of leg raising (b)Back to article page