Influence of airway-occluding instruments on airway pressure during jet ventilation for rigid bronchoscopy

We measured changes in airway pressure (P-aw) caused by microsurgical instr uments introduced into a rigid bronchoscope during high frequency jet venti lation (HFJV), With approval of the institutional Ethics Committee, 10 adul ts undergoing elective tracheobronchial endoscopy and endosonography during general anaesthesia were investigated. Inflation of an endosonography prob e balloon in the left main stem bronchus caused airway obstruction. Pressur e measurements proximal and distal to the obstruction were compared after t hree degrees of obstruction (0%, 50% and 90%) acid with two different drivi ng pressure settings. Airway obstruction increased the mean (SD) peak inspi ratory pressure (PIP) from 7.5 (2.6) to 9.5 (3.5) mm Hg for 2 atm (P = 0.00 08) and from 9.7 (3.7) to 13.0 (5.1) mm Hg for 3 atm (P = 0.0001). Airway o bstruction did not alter peripheral PIP (7.2) (4.1) to 7.1 (3.7) mm Hg for 2 atm and 8.8 (4.3) to 9.4 (5.2) mm for 3 atm), but resulted in an end-expi ratory pressure (EEP) beyond the narrowing being significantly greater than in the unobstructed airway (2.5 (3.4) to 5.5 (3.7) mm Hg for 2 atm; P = 0. 0005) and 3.2 (3,6) to 8.0 (4.3) mm for 3 atm; P < 0.0001). Severe airway n arrowing increases inspiratory pressure proximal and expiratory pressure di stal to the obstruction in relation to the applied driving pressure. Since the distal EEP never exceeded PIP, even near-total airway obstruction shoul d not cause severe lung distension or barotrauma in subjects with normal lu ngs.