Tidal changes on CT and progression of ARDS

Cereda, Maurizio; Xin, Yi; Hamedani, Hooman; Bellani, Giacomo; Kadlecek, Stephen; Clapp, Justin; Guerra, Luca; Meeder, Natalie; Rajaei, Jennia; Tustison, Nicholas J; Gee, James C; Kavanagh, Brian P; Rizi, Rahim R

The experiments were performed on male Sprague-Dawley rats (n=73) following a protocol approved by the local Institutional Animal Care and Use Committee, fully described in our previous work 12 and in the online supplementary material 1 (please see also the list of definitions in table 1). Following general anaesthesia and intubation, hydrochloric acid (HCl, pH 1.25) was injected into the trachea, followed by stabilisation for 1 hour and mechanical ventilation for up to 4 hours (or until death). To increase variability of injury progression, animals received ranges of HCl doses (1-4 mL/kg), and were ventilated with one of several options (not randomised) of positive end-expiratory pressure (PEEP, 3-10 cmH 2 O) and tidal volume (V T , 6-12 mL/kg). In a preliminary analysis, these strategies were aggregated for overall comparison into two groups with higher versus lower propensity to injury progression: one group ventilated non-protective settings and one receiving protective ventilation (table 2) . Gas exchange, peak inspiratory pressure (PIP), driving pressure, 13 mechanical power of inspiration 14 and dynamic compliance (C dyn ) were monitored.