Harvard Medical School, and Department of Anesthesiology, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA.
Ann Biomed Eng. 2011 Mar;39(3):1112-24. doi: 10.1007/s10439-010-0214-0. Epub 2010 Dec 4.
Acute lung injury is characterized by heterogeneity of regional mechanical properties, which is thought to be correlated with disease severity. The feasibility of using respiratory input impedance (Z(rs)) and computed tomographic (CT) image registration for assessing parenchymal mechanical heterogeneity was evaluated. In six dogs, measurements of Z(rs) before and after oleic acid injury at various distending pressures were obtained, followed by whole lung CT scans. Each Z(rs) spectrum was fit with a model incorporating variable distributions of regional compliances. CT image pairs at different inflation pressures were matched using an image registration algorithm, from which distributions of regional compliances from the resulting anatomic deformation fields were computed. Under baseline conditions, average model compliance decreased with increasing inflation pressure, reflecting parenchymal stiffening. After lung injury, these average compliances decreased at each pressure, indicating derecruitment, alveolar flooding, or alterations in intrinsic tissue elastance. However, average compliance did not change as inflation pressure increased, consistent with simultaneous recruitment and strain stiffening. Image registration revealed peaked distributions of regional compliances, and that small portions of the lung might undergo relative compression during inflation. The authors conclude that assessments of lung function using Z(rs) combined with the structural alterations inferred from image registration provide unique but complementary information on the mechanical derangements associated with lung injury.
急性肺损伤的特点是区域性机械特性的异质性，这被认为与疾病严重程度相关。本研究旨在评估使用呼吸输入阻抗（Z(rs)）和计算机断层扫描（CT）图像配准来评估实质机械异质性的可行性。在 6 只狗中，在不同充气压力下测量油酸损伤前后的 Z(rs)，随后进行全肺 CT 扫描。每个 Z(rs)谱都采用包含区域顺应性的可变分布的模型进行拟合。使用图像配准算法匹配不同充气压力下的 CT 图像对，从所得解剖变形场中计算出区域顺应性的分布。在基线条件下，平均模型顺应性随充气压力的增加而降低，反映出实质变硬。在肺损伤后，这些平均顺应性在每个压力下降低，表明去招募、肺泡积水或内在组织弹性的改变。然而，平均顺应性随着充气压力的增加而没有变化，这与同时招募和应变变硬一致。图像配准显示出区域性顺应性的峰值分布，并且在充气过程中肺部的一小部分可能会发生相对压缩。作者得出结论，使用 Z(rs)结合从图像配准推断出的结构改变来评估肺功能，可以提供与肺损伤相关的机械障碍的独特但互补的信息。
