Accelerated deflation promotes homogeneous airspace liquid distribution in the edematous lung

Abstract

Edematous lungs contain regions with heterogeneous alveolar flooding. Liquid is trapped in flooded alveoli by a pressure barrier-higher liquid pressure at the border than in the center of flooded alveoli-that is proportional to surface tension, Stress is concentrated between aerated and flooded alveoli, to a degree proportional to Mechanical ventilation, by cyclically increasing , injuriously exacerbates stress concentrations. Overcoming the pressure barrier to redistribute liquid more homogeneously between alveoli should reduce stress concentration prevalence and ventilation injury. In isolated rat lungs, we test whether accelerated deflation can overcome the pressure barrier and catapult liquid out of flooded alveoli. We generate a local edema model with normal by microinfusing liquid into surface alveoli. We generate a global edema model with high by establishing hydrostatic edema, which does not alter, and then gently ventilating the edematous lungs, which increases at 15 cmHO transpulmonary pressure by 52%. Thus ventilation of globally edematous lungs increases , which should increase stress concentrations and, with positive feedback, cause escalating ventilation injury. In the local model, when the pressure barrier is moderate, accelerated deflation causes liquid to escape from flooded alveoli and redistribute more equitably. Flooding heterogeneity tends to decrease. In the global model, accelerated deflation causes liquid escape, but-because of elevated-the liquid jumps to nearby, aerated alveoli. Flooding heterogeneity is unaltered. In pulmonary edema with normal , early ventilation with accelerated deflation might reduce the positive feedback mechanism through which ventilation injury increases over time. We introduce, in the isolated rat lung, a new model of pulmonary edema with elevated surface tension. We first generate hydrostatic edema and then ventilate gently to increase surface tension. We investigate the mechanical mechanisms through which ) ventilation injures edematous lungs and) ventilation with accelerated deflation might lessen ventilation injury.

The Contribution of Surface Tension-Dependent Alveolar Septal Stress Concentrations to Ventilation-Induced Lung Injury in the Acute Respiratory Distress Syndrome

“…By microscopy of the injured lung surface, flooding and hemorrhage have been observed. By histology, all three forms of injury have been observed (Wu et al, 2017).…”

Mechanical Ventilation Lessons Learned From Alveolar Micromechanics

“…and edematous alveoli (Wu et al, 2017). This stress level is proportional to the surface tension and can be exacerbated by mechanical ventilation (Wu et al, 2017).…”

“…In another isolated perfusion lung model of both local and global alveolar edema, the impact of surface tension and accelerated deflation on alveolar edema clearance was studied (Wu et al, 2017). In lungs with local edema alone, and thus a relatively normal surface tension, accelerated deflation led to release of fluid from flooded alveoli, allowing for redistribution of the fluid, and a decrease in flooding heterogeneity (Wu et al, 2017).…”

“…In another isolated perfusion lung model of both local and global alveolar edema, the impact of surface tension and accelerated deflation on alveolar edema clearance was studied (Wu et al, 2017). In lungs with local edema alone, and thus a relatively normal surface tension, accelerated deflation led to release of fluid from flooded alveoli, allowing for redistribution of the fluid, and a decrease in flooding heterogeneity (Wu et al, 2017). In lungs with global edema, accelerated deflation also led to release of fluid from flooded alveoli, but the fluid redistributed to neighboring alveoli due to the higher surface tension, with no improvement in flooding heterogeneity (Wu et al, 2017).…”

“…In lungs with local edema alone, and thus a relatively normal surface tension, accelerated deflation led to release of fluid from flooded alveoli, allowing for redistribution of the fluid, and a decrease in flooding heterogeneity (Wu et al, 2017). In lungs with global edema, accelerated deflation also led to release of fluid from flooded alveoli, but the fluid redistributed to neighboring alveoli due to the higher surface tension, with no improvement in flooding heterogeneity (Wu et al, 2017). The importance of accelerated deflation on mucous clearance has similarly been described in a porcine lung model and represents a ventilator setting that may alter the lung micro-environment (Mahajan et al, 2019).…”