Microstructural Consequences of Blast Lung Injury Characterized with Digital Volume Correlation

Abstract

This study focuses on microstructural changes that occur within the mammalian lung when subject to blast and how these changes influence strain distributions within the tissue. Shock tube experiments were performed to generate the blast injured specimens (cadaveric Sprague-Dawley rats). Blast overpressures of 100 and 180 kPa were studied. Synchrotron tomography imaging was used to capture volumetric image data of lungs. Specimens were ventilated using a custom-built system to study multiple inflation pressures during each tomography scan. These data enabled the first digital volume correlation (DVC) measurements in lung tissue to be performed. Quantitative analysis was performed to describe the damaged architecture of the lung. No clear changes in the microstructure of the tissue morphology were observed due to controlled low-to moderate-level blast exposure. However, significant focal sites of injury were observed using DVC, which allowed the detection of bias and concentration in the patterns of strain level. Morphological analysis corroborated the findings, illustrating that the focal damage caused by a blast can give rise to diffuse influence across the tissue. It is important to characterize the non-instantly fatal doses of blast, given the transient nature of blast lung in the clinical setting. This research has highlighted the need for better understanding of focal injury and its zone of influence (alveolar interdependency and neighboring tissue burden as a result of focal injury). DVC techniques show great promise as a tool to advance this endeavor, providing a new perspective on lung mechanics after blast.

Novel Mechanical Strain Characterization of Ventilated ex vivo Porcine and Murine Lung using Digital Image Correlation

“…The lung surface strain maps obtained for both porcine (Figures 2, 3) and murine (Figures 5, 6) lungs demonstrate marked heterogeneous expansion across regions of the lung. Pulmonary regional heterogeneity can be due to imbalanced regional ventilation (Milic-Emili et al, 1966;Grasso et al, 2008;Mitzner, 2011), the parenchymal behavior (Denny and Schroter, 2006), or the airway geometry and material (Mead et al, 1957;Arora et al, 2017;Eskandari et al, 2019). The centrally located regions of highest stress in the pig lung appear to trend with the trajectory of the main bronchi (Figure 2), suggesting ventilation in the airways to be a main contributor to heterogeneity; post-experiment transverse plane dicing of the porcine lung reinforced this notion.…”

“…The points on the surface were used to measure the displacement and compute strain (Trilion Quality Systems GOM ARAMIS, 2016). DIC's advantages included the study of whole lung deformation continuously and in real time without the need for extensive sample preparation steps, which often alter the intact tissue properties, or image processing techniques required for digital volume correlation material (Arora et al, 2017).…”

Introducing a Custom-Designed Volume-Pressure Machine for Novel Measurements of Whole Lung Organ Viscoelasticity and Direct Comparisons Between Positive- and Negative-Pressure Ventilation

“…They report better oxygenation and less lung injury because of better distribution of air flow as indicated by dynamic computed tomography and histology (Grasso et al, 2008). Understanding air flow distribution is important, since distribution is complex and heterogeneous in diseased lungs and might behave significantly different in positive-and negative-ventilation (Gattinoni et al, 1986;Skaburskis et al, 1987;Easa et al, 1994;Grasso et al, 2008;Arora et al, 2017).…”

Quantifying 3D Strain in Scaffold Implants for Regenerative Medicine

“…Since its inception 20 years ago for measuring strain in bone [ 8 ], DVC has been applied to extensively for bone-related research [ 9 ], including bone biomechanics [ 10 , 11 ], bone micro-CT scanning optimisation [ 12 ], intact bone joint mechanics [ 13 ], use of micro-MRI for bone compression [ 14 ] and bone fracture prediction [ 15 ]. Research utilising DVC for soft tissue applications is in comparative infancy [ 16 , 17 , 18 ]. Use of DVC for medical implants has solely focused on applications in bone, namely to measure implant micromotion [ 19 ], bone damage during device implantation [ 20 ] and strain across the interface of tissue–biomaterial systems [ 21 ].…”