Hurtado Daniel E, Erranz Benjamín, Lillo Felipe, Sarabia-Vallejos Mauricio, Iturrieta Pablo, Morales Felipe, Blaha Katherine, Medina Tania, Diaz Franco, Cruces Pablo
Department of Structural and Geotechnical Engineering, School of Engineering Pontificia, Universidad Católica de Chile, Santiago, Chile.
Institute for Biological and Medical Engineering, Schools of Engineering, Medicine and Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile.
Ann Intensive Care. 2020 Aug 6;10(1):107. doi: 10.1186/s13613-020-00725-0.
Protective mechanical ventilation (MV) aims at limiting global lung deformation and has been associated with better clinical outcomes in acute respiratory distress syndrome (ARDS) patients. In ARDS lungs without MV support, the mechanisms and evolution of lung tissue deformation remain understudied. In this work, we quantify the progression and heterogeneity of regional strain in injured lungs under spontaneous breathing and under MV.
Lung injury was induced by lung lavage in murine subjects, followed by 3 h of spontaneous breathing (SB-group) or 3 h of low V mechanical ventilation (MV-group). Micro-CT images were acquired in all subjects at the beginning and at the end of the ventilation stage following induction of lung injury. Regional strain, strain progression and strain heterogeneity were computed from image-based biomechanical analysis. Three-dimensional regional strain maps were constructed, from which a region-of-interest (ROI) analysis was performed for the regional strain, the strain progression, and the strain heterogeneity.
After 3 h of ventilation, regional strain levels were significantly higher in 43.7% of the ROIs in the SB-group. Significant increase in regional strain was found in 1.2% of the ROIs in the MV-group. Progression of regional strain was found in 100% of the ROIs in the SB-group, whereas the MV-group displayed strain progression in 1.2% of the ROIs. Progression in regional strain heterogeneity was found in 23.4% of the ROIs in the SB-group, while the MV-group resulted in 4.7% of the ROIs showing significant changes. Deformation progression is concurrent with an increase of non-aerated compartment in SB-group (from 13.3% ± 1.6% to 37.5% ± 3.1%), being higher in ventral regions of the lung.
Spontaneous breathing in lung injury promotes regional strain and strain heterogeneity progression. In contrast, low V MV prevents regional strain and heterogeneity progression in injured lungs.
保护性机械通气（MV）旨在限制全肺变形，且已被证实与急性呼吸窘迫综合征（ARDS）患者更好的临床结局相关。在没有MV支持的ARDS肺中，肺组织变形的机制和演变仍未得到充分研究。在本研究中，我们量化了在自主呼吸和MV条件下损伤肺中区域应变的进展和异质性。
通过对小鼠进行肺灌洗诱导肺损伤，随后进行3小时的自主呼吸（SB组）或3小时的低通气量机械通气（MV组）。在诱导肺损伤后的通气阶段开始和结束时，对所有受试者进行微型计算机断层扫描（Micro-CT）成像。通过基于图像的生物力学分析计算区域应变、应变进展和应变异质性。构建三维区域应变图，并从中对区域应变、应变进展和应变异质性进行感兴趣区域（ROI）分析。
通气3小时后，SB组中43.7%的ROI区域应变水平显著更高。MV组中1.2%的ROI区域应变有显著增加。SB组中100%的ROI区域应变有进展，而MV组中只有1.2%的ROI区域有应变进展。SB组中23.4%的ROI区域应变异质性有进展，而MV组中4.7%的ROI区域有显著变化。在SB组中，变形进展与非充气区增加同时发生（从13.3%±1.6%增加到37.5%±3.1%），在肺的腹侧区域更高。
肺损伤时的自主呼吸促进区域应变和应变异质性进展。相比之下，低通气量MV可防止损伤肺中区域应变和异质性进展。
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