The main causes of difficult tracheal intubation were the limitations of neck extension (n=1 169), mouth opening (n=889), both neck extension and mouth opening (n=698), and micromaxillary deformity (n=69).

• 造成困难插管的原因有：头后仰活动受限(1169例)，张口活动受限(889例)，头后仰活动受限复合张口活动受限(698例)和小颌畸形(69例)。