1792 TRACHEAL INFLAMMATION AND HIGH-FREQUENCY VENTILATION

Abstract

Tracheobronchial histopathology following conventional positive-pressure ventilation (CPPV) was compared to that following high-frequency positive-pressure ventilation (HFPPV) and two types of high-frequency jet ventilation. Twenty-six cats were each ventilated for 16 hours. Seven received CPPV via an infant ventilator (Bourns BP200) cycling at 30 bpm. Seven received HFPPV using the same ventilator cycling at 150 bpm. Six received HFJV via an IDC VS600 ventilator (HFJV1) cycling at 250 bpm. Six received HFJV using a Bunnell ventilator (HFJV2) cycling at 400 bpm. A 4-point, 9-variable histologic scoring system graded tissue changes at four levels of the tracheobronchial tree. High-frequency ventilation produced more inflammatory tracheal injury at the endotracheal tube tip when compared to CPPV (P <.05). CPPV produced more histopathology at the carina and brainstem bronchi (P <.05). There were no significant differences in injury patterns produced by HFJV1 or HFPPV; HFJV2 resulted in less lower airway damage than either HFJV1 or HFPPV (P <.05).In this study, high-frequency ventilation produced inflammatory injuries near the endotracheal tube tip. CPPV produced different and greater histopathology distally. These differences suggest that CPPV and high-frequency ventilation have different injury mechanisms. Tracheal inflammation seen with HFPPV suggests that frequency, not ventilator type, may be at least partially responsible for this lesion.