TY - JOUR
T1 - Dynamic Mechanical Interactions between Neighboring Airspaces Determine Cyclic Opening and Closure in Injured Lung
AU - Broche, Ludovic
AU - Perchiazzi, Gaetano
AU - Porra, Liisa
AU - Tannoia, Angela
AU - Pellegrini, Mariangela
AU - Derosa, Savino
AU - Sindaco, Alessandra
AU - Batista Borges, João
AU - Degrugilliers, Loïc
AU - Larsson, Anders
AU - Hedenstierna, Göran
AU - Wexler, Anthony S.
AU - Bravin, Alberto
AU - Verbanck, Sylvia
AU - Smith, Bradford J.
AU - Bates, Jason H T
AU - Bayat, Sam
PY - 2017/4/1
Y1 - 2017/4/1
N2 - Objectives: Positive pressure ventilation exposes the lung to mechanical stresses that can exacerbate injury. The exact mechanism of this pathologic process remains elusive. The goal of this study was to describe recruitment/derecruitment at acinar length scales over short-time frames and test the hypothesis that mechanical interdependence between neighboring lung units determines the spatial and temporal distributions of recruitment/derecruitment, using a computational model. Design: Experimental animal study. Setting: International synchrotron radiation laboratory. Subjects: Four anesthetized rabbits, ventilated in pressure controlled mode. Interventions: The lung was consecutively imaged at ∼ 1.5-minute intervals using phase-contrast synchrotron imaging, at positive end-expiratory pressures of 12, 9, 6, 3, and 0 cm H2O before and after lavage and mechanical ventilation induced injury. The extent and spatial distribution of recruitment/derecruitment was analyzed by subtracting subsequent images. In a realistic lung structure, we implemented a mechanistic model in which each unit has individual pressures and speeds of opening and closing. Derecruited and recruited lung fractions (Fderecruited, Frecruited) were computed based on the comparison of the aerated volumes at successive time points. Measurements and Main Results: Alternative recruitment/derecruitment occurred in neighboring alveoli over short-time scales in all tested positive end-expiratory pressure levels and despite stable pressure controlled mode. The computational model reproduced this behavior only when parenchymal interdependence between neighboring acini was accounted for. Simulations closely mimicked the experimental magnitude of Fderecruited and Frecruited when mechanical interdependence was included, while its exclusion gave Frecruited values of zero at positive end-expiratory pressure greater than or equal to 3 cm H2O. Conclusions: These findings give further insight into the microscopic behavior of the injured lung and provide a means of testing protective-ventilation strategies to prevent recruitment/derecruitment and subsequent lung damage.
AB - Objectives: Positive pressure ventilation exposes the lung to mechanical stresses that can exacerbate injury. The exact mechanism of this pathologic process remains elusive. The goal of this study was to describe recruitment/derecruitment at acinar length scales over short-time frames and test the hypothesis that mechanical interdependence between neighboring lung units determines the spatial and temporal distributions of recruitment/derecruitment, using a computational model. Design: Experimental animal study. Setting: International synchrotron radiation laboratory. Subjects: Four anesthetized rabbits, ventilated in pressure controlled mode. Interventions: The lung was consecutively imaged at ∼ 1.5-minute intervals using phase-contrast synchrotron imaging, at positive end-expiratory pressures of 12, 9, 6, 3, and 0 cm H2O before and after lavage and mechanical ventilation induced injury. The extent and spatial distribution of recruitment/derecruitment was analyzed by subtracting subsequent images. In a realistic lung structure, we implemented a mechanistic model in which each unit has individual pressures and speeds of opening and closing. Derecruited and recruited lung fractions (Fderecruited, Frecruited) were computed based on the comparison of the aerated volumes at successive time points. Measurements and Main Results: Alternative recruitment/derecruitment occurred in neighboring alveoli over short-time scales in all tested positive end-expiratory pressure levels and despite stable pressure controlled mode. The computational model reproduced this behavior only when parenchymal interdependence between neighboring acini was accounted for. Simulations closely mimicked the experimental magnitude of Fderecruited and Frecruited when mechanical interdependence was included, while its exclusion gave Frecruited values of zero at positive end-expiratory pressure greater than or equal to 3 cm H2O. Conclusions: These findings give further insight into the microscopic behavior of the injured lung and provide a means of testing protective-ventilation strategies to prevent recruitment/derecruitment and subsequent lung damage.
KW - acute respiratory distress syndrome
KW - assisted ventilation
KW - imaging/computed tomography
KW - pulmonary oedema
KW - synchrotron
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U2 - 10.1097/CCM.0000000000002234
DO - 10.1097/CCM.0000000000002234
M3 - Article
C2 - 28107207
AN - SCOPUS:85010005898
VL - 45
SP - 687
EP - 694
JO - Critical Care Medicine
JF - Critical Care Medicine
SN - 0090-3493
IS - 4
ER -