Fig. 2From: Threshold of the upper airway cross-section for hypopnea onset during sleep and its identification under waking conditionThe cross-section of the upper airway at the same retropalatal level corresponding to the four scanning stages: the control, 1 min leg raising, 8 min leg raising, and leg lowering (from left to right). a to d were for groups 1 to 4 respectivelyBack to article page