Regional pulmonary perfusion, blood volume, and their relationship change during early ARDS in an experimental study

Abstract

AbstractRegional pulmonary perfusion (Q) has been investigated using blood volume (Fb) imaging as an easier-to-measure surrogate. However, it is unclear if changing pulmonary conditions could affect their relationship. We hypothesized that vascular changes in early acute respiratory distress syndrome (ARDS) affect Q and Fbdifferently. Five sheep were anesthetized and received protective mechanical ventilation for 20 hours while endotoxin was continuously infused. Using dynamic18F-FDG and13NN Positron Emission Tomography (PET), regional Fband Q were analysed in 30 regions of interest (ROIs) and normalized by tissue content (Fbnand Qn, respectively). After 20 hours, the animals’ lung injury showed characteristics of early ARDS, including gas exchange and lung mechanics. PET images of Fbnand Qnshowed substantial differences between baseline and lung injury. Lung injury caused a significant change in the Fbn-Qnrelationship compared to baseline (p<0.001). The best models at baseline and lung injury were Fbn=0.32+0.690Qnand Fbn=1.684Qn–0.538Qn2, respectively. Early ARDS changed the relationship between Fband Q from linear to curvilinear. Effects of endotoxin exposure on the vasoactive blood flow regulation were most likely the key factor for this change limiting the quantitative accuracy of Fbimaging as a surrogate for regional Q.