necrotizing tracheobronchitis a complication of high frequency jet ventilation the tracheal and bronchial lesions observed are described in seven patients presenting with respiratory distress syndrome and receiving both conventional and high frequency jet ventilation for various periods the histological findings are related to the duration of the exposure as well as the number of pulsations administered to the tracheobronchial tree severe damage to the mucosa leading to acute tracheobronchitis hyperplasia and hypersecretion of the mucosal glands may explain some of the clinical symptoms observed especially the upper respiratory obstruction care should be taken to limit these changes which may lead to various degrees of stenosis in survivors receiving this mode of therapy