Blast lung injury from an explosion on a civilian bus

Objective: To assess clinical signs and management of primary blast lung injury (BLI) from explosions in an enclosed space and to propose a BLI severity scoring system. Design: Retrospective analysis. Patients: Fifteen patients with primary BLI resulting from explosions on two civilian buses in 1996. Results: Ten patients were extremely hypoxemic on admission (Pa(O2) < 65 mm Hg with oxygen supplementation). Four patients remained severely hypoxemic (Pa(O2)/fraction of inspired oxygen (F(IO2)) ratio of < 60 mm Hg) after mechanical ventilation was established and pneumothoraces were drained. Initial chest radiographs revealed bilateral lung opacities of various sizes in 12 patients (80%). Seven patients (47%) had bilateral pneumothoraces and two patients had a unilateral pneumothorax. Five (33%) had clinically significant bronchopleural fistulae. After clinical and laboratory data were collected, a BLI severity score was defined based on hypoxemia Pa(O2)/F(IO2) ratio), chest radiographic abnormalities, and barotrauma. Severe BLI was defined as a Pa(O2)/F(IO2) ratio of < 60 mm Hg, bilateral lung infiltrates, and bronchopleural fistula; moderate BLI as a Pa(O2)/F(IO2) ratio of 60 to 200 mm Hg and diffuse (bilateral/unilateral) lung infiltrates with or without pneumothorax; and mild BLI as a Pa(O2)/F(IO2) ratio of > 200, localized lung infiltrates, and no pneumothorax. Five patients developed ARDS with Murray scores > 2.5. Respiratory management included positive pressure ventilation in the majority of the patients and unconventional methods (ie, high- frequency jet ventilation, independent lung ventilation, nitric oxide, and extracorporeal membrane oxygenation) in patients with severe BLI. Of the four patients who had severe BLI, three died. All six patients with moderate BLI survived, and four of five with mild BLI survived (one with head injury died). Conclusions: BLI can cause severe hypoxemia, which can be improved significantly with aggressive treatment. The lung damage may be accurately estimated in the early hours after injury. The BLI severity score may be helpful in determining patient management and prediction of final outcome.