Pérez Agustín, Erranz Benjamín, Reveco Sonia, González Carlos, Avilés-Rojas Nibaldo, Hurtado Daniel E, 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.
Crit Care. 2025 Jul 24;29(1):322. doi: 10.1186/s13054-025-05536-y.
Strenuous respiratory effort has been proposed as a second hit in severe acute lung injury (ALI), introducing the concept of "patient self-inflicted lung injury" (P-SILI). In an experimental setting, noninvasive continuous positive airway pressure (CPAP) attenuates lung and diaphragmatic injury, but the underlying mechanisms remains elusive. Here we investigate the effects of noninvasive CPAP on global and regional lung strain and diaphragm velocity of contraction and relaxation in an experimental P-SILI model.
Lung injury was induced in Sprague Dawley rats through surfactant depletion followed by either three hours of standard oxygen therapy (Control group) or CPAP support (CPAP group). Subjects were assessed through inspiratory and expiratory muscle activation. Regional lung and diaphragmatic deformation amplitude (strain) and the rate of change (strain rate) maps were developed using a micro-computed tomography (µCT) scan. Morphometric tissue assessment was carried out to study biological damage.
Compared with the Control group, the CPAP group resulted in: (1) higher SpO and lower respiratory rate, nasal flaring, inspiratory and expiratory muscle activation, and minute ventilation at the end of the study; (2) lower global and regional tidal ventilation at the beginning of the study; (3) lower regional inspiratory and expiratory lung strain rate over time; and (4) higher muscle area in the diaphragm morphometric analysis. Furthermore, intragroup analysis showed that only the CPAP group reduced the inspiratory and expiratory muscle activation, the global and regional expiratory lung strain rate and the regional velocity of relaxation of the diaphragm over time.
Standard oxygen therapy resulted in worse patterns of lung strain rate and diaphragm velocity of relaxation, consistent with P-SILI and load-induced diaphragm injury. CPAP resulted in improved lung function, decreased lung strain rate, and diaphragmatic relaxation velocity throughout the respiratory cycle. We conclude that CPAP promotes biomechanical protection in injured lungs and diaphragm, more noticeably during the expiratory phase.
剧烈的呼吸努力被认为是重症急性肺损伤（ALI）中的二次打击，由此引入了“患者自身造成的肺损伤”（P-SILI）这一概念。在实验环境中，无创持续气道正压通气（CPAP）可减轻肺和膈肌损伤，但其潜在机制仍不清楚。在此，我们在实验性P-SILI模型中研究无创CPAP对整体和局部肺应变以及膈肌收缩和舒张速度的影响。
通过表面活性剂耗竭诱导斯普拉格-道利大鼠发生肺损伤，随后给予三小时的标准氧疗（对照组）或CPAP支持（CPAP组）。通过吸气和呼气肌肉激活对受试者进行评估。使用微型计算机断层扫描（µCT）扫描绘制局部肺和膈肌变形幅度（应变）以及变化率（应变率）图。进行形态计量学组织评估以研究生物损伤。
与对照组相比，CPAP组导致：（1）在研究结束时SpO₂ 更高，呼吸频率、鼻翼扇动、吸气和呼气肌肉激活以及分钟通气量更低；（2）在研究开始时整体和局部潮气量更低；（3）随着时间推移局部吸气和呼气肺应变率更低；（4）在膈肌形态计量分析中肌肉面积更大。此外，组内分析表明，只有CPAP组随着时间推移降低了吸气和呼气肌肉激活、整体和局部呼气肺应变率以及膈肌局部舒张速度。
标准氧疗导致肺应变率和膈肌舒张速度的模式更差，这与P-SILI和负荷诱导的膈肌损伤一致。CPAP在整个呼吸周期中改善了肺功能，降低了肺应变率和膈肌舒张速度。我们得出结论，CPAP可促进对受损肺和膈肌的生物力学保护，在呼气期更为明显。
