Fig. 5
a-d Perfusion differences with arterial/venous occlusion of small bowel model. Arterial occlusion is achieved via clamping of proximal aorta and venous occlusion is achieved via clamping of portal vein. 5A RGB image of complete arterial occlusion of small bowel gradient model. 5B LSCI contrast image of complete arterial occlusion of small bowel gradient model. 5C RGB image of complete venous occlusion of small bowel gradient model. 5D LSCI contrast image of complete venous occlusion of small bowel gradient model. While there are no perfusion differences detected under visual inspection on RGB (5A and 5C), both arterial and venous occlusion result in ischemia that can be detected via the dark blue colormap on LSCI. Complete arterial and venous occlusion result in a similar low perfusion state that can be both observed and quantified using LSCI. e Effect of changes in mean arterial pressure via progressive arterial/venous occlusion) on bowel perfusion (measured in RPU). Relative Perfusion Units (RPU) can be seen on Y axis vs Mean Arterial Pressure (MAP, mm Hg) on X axis. The MAP gradient was created via progressive arterial occlusion and venous occlusion and MAP was measured downstream via arterial line in the iliac artery. Red lines indicate changes occurring resulting from progressive arterial occlusion in both perfused and watershed bowel, while blue lines indicate changes in both perfused and watershed bowel resulting from progressive venous occlusion. Solid lines represent the behavior of the perfused segment of bowel, while dashed lines represent the behavior of the watershed bowel segment. With both progressive arterial and venous occlusion, perfused/watershed segment RPUs had a strong linear relationship with MAP – higher MAPs in observed tissue correlated with higher RPU values, while lower MAPs induced by progressive clamp correlated with lower RPU values. For arterial occlusion (red lines), R2 = 0.96/0.79 for perfused/watershed bowel (bold/dash);for venous (blue lines) occlusion, R2 = 0.06/0.96 for perfused/watershed bowel (bold/dash). An increased sensitivity to venous occlusion was observed—small decreases in MAP secondary to venous occlusion resulted in large drops in mean RPU of bowel segments