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Effects of ventilation strategy on distribution of lung inflammatory cell activity
Journal article   Open access   Peer reviewed

Effects of ventilation strategy on distribution of lung inflammatory cell activity

Nicolas de Prost, Eduardo L. Costa, Tyler Wellman, Guido Musch, Mauro R. Tucci, Tilo Winkler, R. Scott Harris, Jose G. Venegas, Brian P. Kavanagh and Marcos F. Vidal Melo
Critical care (London, England), Vol.17(4), pp.R175-R175
08/15/2013
DOI: 10.1186/cc12854
PMID: 23947920
url
https://doi.org/10.1186/cc12854View
Published (Version of record) Open Access

Abstract

Introduction: Leukocyte infiltration is central to the development of acute lung injury, but it is not known how mechanical ventilation strategy alters the distribution or activation of inflammatory cells. We explored how protective (vs. injurious) ventilation alters the magnitude and distribution of lung leukocyte activation following systemic endotoxin administration. Methods: Anesthetized sheep received intravenous endotoxin (10 ng/kg/min) followed by 2 h of either injurious or protective mechanical ventilation (n = 6 per group). We used positron emission tomography to obtain images of regional perfusion and shunting with infused N-13[nitrogen]-saline and images of neutrophilic inflammation with F-18-fluorodeoxyglucose (F-18-FDG). The Sokoloff model was used to quantify F-18-FDG uptake (K-i), as well as its components: the phosphorylation rate (k(3), a surrogate of hexokinase activity) and the distribution volume of F-18-FDG (F-e) as a fraction of lung volume (K-i = F-e x k(3)). Regional gas fractions (f(gas)) were assessed by examining transmission scans. Results: Before endotoxin administration, protective (vs. injurious) ventilation was associated with a higher ratio of partial pressure of oxygen in arterial blood to fraction of inspired oxygen (PaO2/FiO(2)) (351 +/- 117 vs. 255 +/- 74 mmHg; P < 0.01) and higher whole-lung f(gas) (0.71 +/- 0.12 vs. 0.48 +/- 0.08; P = 0.004), as well as, in dependent regions, lower shunt fractions. Following 2 h of endotoxemia, PaO2/FiO(2) ratios decreased in both groups, but more so with injurious ventilation, which also increased the shunt fraction in dependent lung. Protective ventilation resulted in less nonaerated lung (20-fold; P < 0.01) and more normally aerated lung (14-fold; P < 0.01). K-i was lower during protective (vs. injurious) ventilation, especially in dependent lung regions (0.0075 +/- 0.0043/min vs. 0.0157 +/- 0.0072/min; P < 0.01). F-18-FDG phosphorylation rate (k(3)) was twofold higher with injurious ventilation and accounted for most of the between-group difference in K-i. Dependent regions of the protective ventilation group exhibited lower k(3) values per neutrophil than those in the injurious ventilation group (P = 0.01). In contrast, F-e was not affected by ventilation strategy (P = 0.52). Lung neutrophil counts were not different between groups, even when regional inflation was accounted for. Conclusions: During systemic endotoxemia, protective ventilation may reduce the magnitude and heterogeneity of pulmonary inflammatory cell metabolic activity in early lung injury and may improve gas exchange through its effects predominantly in dependent lung regions. Such effects are likely related to a reduction in the metabolic activity, but not in the number, of lung-infiltrating neutrophils.
 Critical Care Medicine General & Internal Medicine Life Sciences & Biomedicine Science & Technology

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