Does Regional Lung Strain Correlate With Regional Inflammation in Acute Respiratory Distress Syndrome During Nonprotective Ventilation? An Experimental Porcine Study

Abstract

Objective: It is known that ventilator-induced lung injury causes
increased pulmonary inflammation. It has been suggested that
one of the underlying mechanisms may be strain. The aim of this
study was to investigate whether lung regional strain correlates
with regional inflammation in a porcine model of acute respiratory
distress syndrome.
Design: Retrospective analysis of CT images and positron emission
tomography images using [18F]fluoro-2-deoxy-D-glucose.
Setting: University animal research laboratory.
Subjects: Seven piglets subjected to experimental acute respiratory
distress syndrome and five ventilated controls.
Interventions: Acute respiratory distress syndrome was induced
by repeated lung lavages, followed by 210 minutes of injurious
mechanical ventilation using low positive end-expiratory pressures
(mean, 4cm H2O) and high inspiratory pressures (mean plateau
pressure, 45cm H2O). All animals were subsequently studied with
CT scans acquired at end-expiration and end-inspiration, to obtain
maps of volumetric strain (inspiratory volume – expiratory volume)/
expiratory volume, and dynamic positron emission tomography
imaging. Strain maps and positron emission tomography images
were divided into 10 isogravitational horizontal regions-of-interest,
from which spatial correlation was calculated for each animal.
Conclusion: In this porcine acute respiratory distress syndrome
model, regional lung strain was spatially correlated with regional.