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Measurement of Δ wedging ratio in supine and 30° head‐elevated positions. Δ wedging ratio = wedging ratio (30° head‐elevated) − wedging ratio (supine) = (a–b)/a × 100–(c–d)/c × 100 (%). (a) leading edge in supine position; (b) trailing edge in supine position; (c) leading edge at 30° head‐elevated position; (d) trailing edge at 30° head‐elevated position.
