A model for predicting primary blast lung injury.

BACKGROUND: This article presents a model-based method for predicting primary blast injury. On the basis of the normalized work injury mechanism from previous work, this method presents a new model that accounts for the effects of blast orientation and species difference. METHODS: The analysis used test data from a series of extensive experimental studies sponsored by the US Army Medical Research and Materiel Command. In these studies, more than 1200 sheep were exposed to air blast in free-field and confined enclosures, and lung injuries were quantified as the percentage of surface area contused. Blast overpressure data were collected using blast test devices placed at matching locations to represent loadings to the thorax. Adopting the modified Lobdell model with further modifications specifically for blast and scaling, the thorax deformation histories for the left, chest, and right sides of the thorax were calculated for all sheep subjects. Using the calculated thorax velocities, effective normalized work was computed for each test subject representing the irreversible work performed on the lung tissues normalized by lung volume and ambient pressure. RESULTS: Dose-response curves for four categories of injuries (trace, slight, moderate, and severe) were developed by performing log-logistic correlations of the computed normalized work with the injury outcomes, including the effect of multiple shots. A blast lethality correlation was also established. CONCLUSION: Validated by sheep data, the present work revalidates the previous understanding and findings of the blast lung injury mechanism and provides an anthropomorphic model for primary blast injury prediction that can be used for occupational and survivability analysis. LEVEL OF EVIDENCE: Economic and decision analysis, level III.