病因呼吸系统解剖生理特点婴幼儿呼吸道短、小而窄,无鼻毛,细菌及过敏原等容易直达下呼吸道。且血管淋巴组织丰富,感染后粘膜易充血水肿而阻塞,引起张口呼吸。气管及支气管软骨较软,弹力组织发育不完善,血管多,腺体分泌少以及纤毛运动能力差,对吸入的细菌、颗粒、灰尘及过敏原等 Etiology Respiratory anatomy and physiology Infantile respiratory tract short, small and narrow, no nose hair, bacteria and allergens easily accessible to the lower respiratory tract. And rich in vascular lymphoid tissue, mucosal infection prone to congestion and edema and obstruction, causing mouth breathing. Trachea and bronchial cartilage is relatively soft, imperfectly developed elastic tissue, blood vessels, less glandular secretion and poor ciliary motility, inhalation of bacteria, particles, dust and allergens