0894. Time course of VILI development: a CT scan study

Methods Piglets were instrumented and ventilated with TV of corresponding to a strain (TV/FRC) >2.5. The whole study was performed in an animal CT scan facilities equipped as an ICU. Every three hours a CT scan was performed and data on respiratory mechanics were collected. CT scans were analysed and lesions were defined as clearly defined regions of poorly/not inflated tissue (-500/+100 HU) with a minimal diameter of 6 mm non present in the previous CT scan image. Lung weight was computed from the CT scan data. Results We studied 11 swine (22±5 kg), 5 healthy and 6 with basal densities which did not regain inflation after a recruitment manoeuvre. As shown in Figure 1 most the CT scan lesions were subpleural. The first CT scan lesions appeared after a median of 7 hours [4.5-12] in healthy pigs and after a median of 9 hours [6.5-11.5] in diseased ones (p=0.88 healthy vs diseased) while changes in lung mechanics developed after 20 [13 23] hours (p = 0.04 vs time of development of CT scan lesions) and oxygenation impairment, defined as PaO2FiO2 < 200, after 25 [14 36] hours (p = 0.003 vs time of development of CT scan lesions) while widespread lung oedema defined as presence of infiltrations in all lung fields at CT scan imaging developed after 18 [12 32] hours (p = 0.02 vs time of development of CT scan lesions).