Médecine Intensive-Réanimation, Groupement Hospitalier Centre, Hôpital Edouard Herriot, Lyon, France.
Université de Lyon, Lyon, France.
J Appl Physiol (1985). 2021 Jul 1;131(1):15-25. doi: 10.1152/japplphysiol.00104.2021. Epub 2021 May 13.
Regional viscoelastic properties of thoracic tissues in acute respiratory distress syndrome (ARDS) and their change with position and positive end-expiratory pressure (PEEP) are unknown. In an experimental porcine ARDS, dorsal and ventral lung (R,L and E,L) and chest wall (R,cw and E,cw) viscoelastic resistive (R) and elastic (E) parameters were measured at 20, 15, 10, and 5 cmHO PEEP in supine and prone position. E and R were obtained by fitting the decay of pressure after end-inspiratory occlusion to the equation: P (t) =R e, where t is the length of occlusion and τ time constant. E was equal to R/τ. R,cw and E,cw were measured from esophageal, dorsal, and ventral pleural pressures. Global R,L and E,L were obtained from the global transpulmonary pressure (airway pressure-esophageal pressure), and regional R,L and E,L from the dorsal and ventral airway pressure-pleural pressure difference. Lung ventilation was measured by electrical impedance tomography (EIT). Global R,cw and E,cw did not change with PEEP or position. Global R,L [median(Q1-Q3)] was 37.1 (11.0-65.1), 5.1 (4.3-5.5), 12.1 (8.4-19.5), and 41.0 (26.6-53.5) cmHO/L/s in supine, and 15.3 (9.1-41.9), 7.9 (5.7-11.0), 8.0 (5.1-12.1), and 12.9 (6.4-19.4) cmHO/L in prone from 20 to 5 cmHO PEEP ( = 0.06 for PEEP and = 0.06 for position). Dorsal R,L significantly and positively correlated with the amount of collapse measured with EIT. Global and regional lung and chest wall viscoelastic parameters can be described by a simple rheological model. Regional E and R were uninfluenced by PEEP and position except for PEEP on dorsal E,L and position on dorsal E,cw. In a porcine model of acute respiratory distress syndrome, data were successfully fitted to a rheological model of the nonlinear behavior of viscoelastic properties of lung and chest wall at different positive end-expiratory pressure (PEEP) in the supine and prone position. Prone position tended to decrease lung viscoelastic resistive component. PEEP had a significant effect on dorsal lung viscoelastic elastance. Finally, lung viscoelastic resistance correlated with the amount of lung collapse assessed by electrical impedance tomography.
急性呼吸窘迫综合征（ARDS）患者的胸壁和肺组织的区域性黏弹特性及其与体位和呼气末正压（PEEP）的关系尚不清楚。在一项实验性猪 ARDS 模型中，在仰卧位和俯卧位时，于 20、15、10 和 5 cmH2O PEEP 下测量背部和腹部肺（R，L 和 E，L）及胸壁（R，cw 和 E，cw）的黏弹阻力（R）和弹性（E）参数。通过将吸气末阻断后的压力衰减拟合到方程：P（t）=R e，其中 t 为阻断时间，τ为时间常数，获得 E 和 R。E 等于 R/τ。E,cw 和 R,cw 通过测量食管、背部和腹部胸膜压力获得。通过测量肺部通气的电阻抗断层扫描（EIT）获得整体肺（R，L 和 E，L）的参数，通过测量背部和腹部气道压力-胸膜压力差获得局部肺（R，L 和 E，L）的参数。整体肺（R，cw 和 E，cw）的参数在 PEEP 和体位变化时没有改变。仰卧位时，整体肺（R，L）[中位数（Q1-Q3）]为 37.1（11.0-65.1）、5.1（4.3-5.5）、12.1（8.4-19.5）和 41.0（26.6-53.5）cmH2O/L/s，俯卧位时为 15.3（9.1-41.9）、7.9（5.7-11.0）、8.0（5.1-12.1）和 12.9（6.4-19.4）cmH2O/L，在 20-5 cmH2O PEEP 时，差异均有统计学意义（PEEP 差异的 P 值=0.06，体位差异的 P 值=0.06）。背部肺（R，L）与 EIT 测量的塌陷程度呈显著正相关。整体和局部肺及胸壁黏弹参数可以用简单的流变学模型来描述。除了俯卧位的背部肺（E，L）和仰卧位的背部肺（E，cw）的 PEEP 以及俯卧位的胸壁（R，cw）和仰卧位的胸壁（E，cw）的体位外，PEEP 和体位对整体和局部肺及胸壁的弹性和阻力参数没有影响。在急性呼吸窘迫综合征的猪模型中，数据成功地拟合到了一个流变学模型，该模型描述了在仰卧位和俯卧位时不同呼气末正压（PEEP）下肺和胸壁的黏弹特性的非线性行为。俯卧位可能会降低肺的黏弹阻力成分。PEEP 对背部肺的黏弹弹性有显著影响。最后，肺的黏弹阻力与 EIT 评估的肺塌陷量相关。
