Dynamic pathophysiological features of early primary blast lung injury: a novel functional incapacity pig model.

Introduction: While there is evidence supporting the use of ultrasound for real-time monitoring of primary blast lung injury (PBLI), uncertainties remain regarding the timely detection of early PBLI and the limited data correlating it with commonly used clinical parameters. Our objective is to develop a functional incapacity model for PBLI that better addresses practical needs and to verify the early diagnostic effectiveness of lung ultrasound in identifying PBLI.

Methods: We selected six healthy male pigs to develop an animal model using a bio-shock tube (BST-I). The injuries were induced at a pressure of 4.8 MPa. We monitored the animals before and after the injury using various methods to detect changes in vital signs, lung function, and hemodynamics.

Results: The experimental peak overpressure was measured at 405.89 ± 4.14KPa, with the duration of the first positive peak pressure being 50.01ms. The mortality rate six hours after injury was 50%. The average Military Combat Injury Scale was higher than 3. Significant increases were observed in heart rate (HR), shock index (SI), alveolar-arterial oxygen gradient (AaDO₂), lung ultrasound scores(LUS), and pulmonary vascular permeability index (PVPI) at 0.5 h, 3 h, and 6 h after-injury (p < 0.05). Conversely, there were notable decreases in average arterial pressure(MAP), oxygenation index (OI), stroke volume per heartbeat(SV), cardiac output power index(CPI), global end-diastolic index (GEDI), and intrathoracic blood volume index (ITBI) during the same time periods (p < 0.05). Meanwhile, the extrapulmonary water index (ELWI) showed a significant increase at 0.5 h and 6 h after injury (p < 0.05). At 6 h after injury, pulmonary ultrasound scores were positively correlated with HR (R = 0.731, p < 0.001), AaDO₂ (R = 0.612, p = 0.012), SI (R = 0.661, p = 0.004), ELWI (R = 0.811, p < 0.001), PVPI (R = 0.705, p = 0.002). In contrast, these scores were negatively correlated with SpO₂ (R = -0.583, p = 0.007),OI (R = -0.772, p < 0.001), ITBI (R = -0.637, p = 0.006).

Conclusion: We have successfully developed a novel, and highly reproducible animal model for assessing serious PBLI functional incapacity. This model displays immediate symptoms of hypoxia, decreased cardiac output, decreased blood volume, and abnormal lung ultrasound findings within 0.5 h of injury, with syptoms lasting for up to 6 h. Lung ultrasound evaluation is crucial for the early assessment of injuries, and is comparable to commonly used clinical parameters.