Recent reports linking serious tracheal injuries to various forms of high-frequency ventilation prompted this study. We compared the tracheal histopathology seen following standard-frequency, conventional mechanical ventilation with that seen following high-frequency, conventional mechanical ventilation, and two different forms of high-frequency jet ventilation. Twenty-six adult cats were examined. Each was mechanically ventilated for 16 hours. Seven received standard-frequency, conventional mechanical ventilation at 20 breaths per minute. Seven received high-frequency, conventional mechanical ventilation at 150 breaths per minute. Six received high-frequency jet ventilation at 250 breaths per minute via the Instrument Development Corporation VS600 jet ventilator (IDC). Six received high-frequency jet ventilation at 400 breaths per minute via the Bunnell Life Pulse jet ventilator (BLP). A semiquantitative histopathologic scoring system graded tracheal tissue changes. All forms of high-frequency ventilation produced significant inflammation (erosion, necrosis, and polymorphonuclear leukocyte infiltration) in the trachea in the region of the endotracheal tube tip. Conventional mechanical ventilation produced less histopathology than any form of high-frequency ventilation. Of all of the ventilators examined, the BLP, the ventilator operating at the fastest rate, produced the greatest loss of surface cilia and depletion of intracellular mucus. IDC high-frequency jet ventilation and high-frequency, conventional mechanical ventilation produced nearly identical histologic injuries. In this study, significant tracheal damage occurred with all forms of high-frequency ventilation. The tracheal damage seen with high-frequency, conventional mechanical ventilation suggests that ventilator frequency, not delivery system, may be responsible for the injuries.
P0395 / #854: TOPIC: THE LUNG. HIGH FREQUENCY JET VENTILATION COMBINED WITH BILEVEL VENTILATION TO SUPPORT CHILDREN WHO FAILED CONVENTIONAL MECHANICAL VENTILATION.
