Effects of ventilation strategy on distribution of lung inflammatory cell activity

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• 作者：Nicolas de Prost (11)
  Eduardo L Costa (11)
  Tyler Wellman (11)
  Guido Musch (11)
  Mauro R Tucci (11)
  Tilo Winkler (11)
  R Scott Harris (12)
  Jose G Venegas (11)
  Brian P Kavanagh (13)
  Marcos F Vidal Melo (11)
  
• 刊名：Critical Care
• 出版年：2013
• 出版时间：August 2013
• 年：2013
• 卷：17
• 期：4
• 全文大小：
• 作者单位：Nicolas de Prost (11)
  Eduardo L Costa (11)
  Tyler Wellman (11)
  Guido Musch (11)
  Mauro R Tucci (11)
  Tilo Winkler (11)
  R Scott Harris (12)
  Jose G Venegas (11)
  Brian P Kavanagh (13)
  Marcos F Vidal Melo (11)
  
  11. Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA, 02114, USA
  12. Department of Medicine (Pulmonary and Critical Care Unit), Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA, 02114, USA
  13. Departments of Critical Care and Anesthesia, Hospital for Sick Children, University of Toronto, 555 University Avenue, Toronto, ON, M5G 1X8, Canada
  
• ISSN：1364-8535

文摘

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 13N[nitrogen]-saline and images of neutrophilic inflammation with 18F-fluorodeoxyglucose (18F-FDG). The Sokoloff model was used to quantify 18F-FDG uptake (K i), as well as its components: the phosphorylation rate (k 3, a surrogate of hexokinase activity) and the distribution volume of 18F-FDG (F e) as a fraction of lung volume (K i = F e × 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/FiO2) (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/FiO2 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). 18F-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.