• Maurizio Cereda, Yi Xin, Natalie Meeder, Johnathan Zeng, YunQing Jiang, Hooman Hamedani, Harrilla Profka, Stephen Kadlecek, Justin Clapp, Charuhas G Deshpande, Jue Wu, James C Gee, Brian P Kavanagh, and Rahim R Rizi.
• From the Departments of Anesthesiology and Critical Care (M.C., N.M.), Radiology (Y.X., J.Z., Y.J., H.H., H.P., S.K., J.C., J.W., J.C.G., R.R.R.), and Pathology and Laboratory Medicine (C.G.D.), University of Pennsylvania, Philadelphia, Pennsylvania; and Department of Anesthesia, Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada (B.P.K.).
• Anesthesiology. 2016 Jan 1;124(1):121-31.

BackgroundMechanical ventilation worsens acute respiratory distress syndrome, but this secondary "ventilator-associated" injury is variable and difficult to predict. The authors aimed to visualize the propagation of such ventilator-induced injury, in the presence (and absence) of a primary underlying lung injury, and to determine the predictors of propagation.MethodsAnesthetized rats (n = 20) received acid aspiration (hydrochloric acid) followed by ventilation with moderate tidal volume (V(T)). In animals surviving ventilation for at least 2 h, propagation of injury was quantified by using serial computed tomography. Baseline lung status was assessed by oxygenation, lung weight, and lung strain (V(T)/expiratory lung volume). Separate groups of rats without hydrochloric acid aspiration were ventilated with large (n = 10) or moderate (n = 6) V(T).ResultsIn 15 rats surviving longer than 2 h, computed tomography opacities spread outward from the initial site of injury. Propagation was associated with higher baseline strain (propagation vs. no propagation [mean ± SD]: 1.52 ± 0.13 vs. 1.16 ± 0.20, P < 0.01) but similar oxygenation and lung weight. Propagation did not occur where baseline strain was less than 1.29. In healthy animals, large V(T) caused injury that was propagated inward from the lung periphery; in the absence of preexisting injury, propagation did not occur where strain was less than 2.0.ConclusionsCompared with healthy lungs, underlying injury causes propagation to occur at a lower strain threshold and it originates at the site of injury; this suggests that tissue around the primary lesion is more sensitive. Understanding how injury is propagated may ultimately facilitate a more individualized monitoring or management.

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