Experimental Study on Intracranial Pressure and Biomechanical Response in Rats Under the Blast Wave

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.

Spatial Intracranial Pressure Fields Driven by Blast Overpressure in Rats

Free-field blast exposure imparts a complex, dynamic response within brain tissue that can trigger a cascade of lasting neurological deficits. Full body mechanical and physiological factors are known to influence the body's adaptation to this seemingly instantaneous insult, making it difficult to accurately pinpoint the brain injury mechanisms. This study examined the intracranial pressure (ICP) profile characteristics in a rat model as a function of blast overpressure magnitude and brain location. Metrics such as peak rate of change of pressure, peak pressure, rise time, and ICP frequency response were found to vary spatially throughout the brain, independent of blast magnitude, emphasizing unique spatial pressure fields as a primary biomechanical component to blast injury. This work discusses the ICP characteristics and considerations for finite element models, in vitro models, and translational in vivo models to improve understanding of biomechanics during primary blast exposure.

Investigating neuropathological changes and underlying neurobiological mechanisms in the early stages of primary blast-induced traumatic brain injury: Insights from a rat model

The utilization of explosives and chemicals has resulted in a rise in blast-induced traumatic brain injury (bTBI) in recent times. However, there is a dearth of diagnostic biomarkers and therapeutic targets for bTBI due to a limited understanding of biological mechanisms, particularly in the early stages. The objective of this study was to examine the early neuropathological characteristics and underlying biological mechanisms of primary bTBI. A total of 83 Sprague Dawley rats were employed, with their heads subjected to a blast shockwave of peak overpressure ranging from 172 to 421 kPa in the GI, GII, and GIII groups within a closed shock tube, while the body was shielded. Neuromotor dysfunctions, morphological changes, and neuropathological alterations were detected through modified neurologic severity scores, brain water content analysis, MRI scans, histological, TUNEL, and caspase-3 immunohistochemical staining. In addition, label-free quantitative (LFQ)-proteomics was utilized to investigate the biological mechanisms associated with the observed neuropathology. Notably, no evident damage was discernible in the GII and GI groups, whereas mild brain injury was observed in the GIII group. Neuropathological features of bTBI were characterized by morphologic changes, including neuronal injury and apoptosis, cerebral edema, and cerebrovascular injury in the shockwave's path. Subsequently, 3153 proteins were identified and quantified in the GIII group, with subsequent enriched neurological responses consistent with pathological findings. Further analysis revealed that signaling pathways such as relaxin signaling, hippo signaling, gap junction, chemokine signaling, and sphingolipid signaling, as well as hub proteins including Prkacb, Adcy5, and various G-protein subunits (Gnai2, Gnai3, Gnao1, Gnb1, Gnb2, Gnb4, and Gnb5), were closely associated with the observed neuropathology. The expression of hub proteins was confirmed via Western blotting. Accordingly, this study proposes signaling pathways and key proteins that exhibit sensitivity to brain injury and are correlated with the early pathologies of bTBI. Furthermore, it highlights the significance of G-protein subunits in bTBI pathophysiology, thereby establishing a theoretical foundation for early diagnosis and treatment strategies for primary bTBI.