内視鏡先端位置:高位置
(咽頭腔全体が見渡せ、食塊が咽頭に流入する様子や咽頭収縮を観察しやすい)
・嚥下中は視野が真っ白になる。(White out)
・White outの直前に、牛乳の咽頭流入がわずかに確認できる。

内視鏡先端位置:低位置
(喉頭内を観察し、喉頭侵入や誤嚥の有無、梨状窩の食塊残留などを確認する)

FEES position: high
(allows the observation of the whole pharynx and easy observation of the bolus transport into pharynx and pharyngeal contraction)
・a flash of white know as “White-out”
・Enable to observe the slight spillage of milk into pharynx just before White out.

FEES position: low
(allows to observe of larynx, presence of penetration and aspiration, and the bolus residue in pyriform sinuses)