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Volume 3 Supplement 1

ESICM LIVES 2015

Lung inhomogeneities, inflation and [18F]FDG uptake rate in ards

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Introduction

In ARDS lung parenchyma presents great variability in inflation, lung inhomogeneities and [18F]FDG uptake. In fact, inflation progressively decreases along the sternum-vertebral axis[1] leading to further inhomogeneities that may act as “stress raiser”.[2] That can activate a local inflammatory response leading to edema.

Objectives

We aimed to examine the voxel by voxel relationship between [18F]FDG uptake and inhomogeneity according to the actual classification of ARDS.

Methods

20 ARDS patients underwent a PET-CT scan at 10 cmH2O. [18F]FDG uptake was determined with the graphical Patlak approach[3] voxel by voxel. Lung inhomogeneities were determined by measuring the gas/tissue ratio in two contiguous lung regions. We defined inhomogeneities the fraction of lung volume whose inhomogeneities were greater than 1.61.[4]

Results

5 patients presented mild, 12 moderate and 3 severe ARDS. In mild and moderate ARDS a consistent lung fraction is homogeneous with a high [18F]FDG metabolic activity (53 ± 14% and 53 ± 20%). Inhomogeneous lung fraction with a higher [18F]FDG uptake increases from mild to severe (12 ± 3%, 16 ± 9% and 27 ± 11%). On the other hand, the homogeneous parenchyma with normal [18F]FDG uptake decreases in worse ARDS (33 ± 14%, 26 ± 20% and 5 ± 9%).

Conclusions

Our findings indicate that the actual classification of ARDS from mild to severe reflects the underlying pathophysiology. In fact, while a similar sized homogeneous and inflamed/metabolically more active compartment is present in all the ARDS patients, in mild ARDS it is associated with a consistent fraction of normal lung while in severe ARDS is primarily associated with inhomogeneous, inflamed/metabolically more active lung tissue.

References

  1. 1.

    Gattinoni L: Intensive Care Med. 2005, 31 (6): 776-84. 10.1007/s00134-005-2627-z.

  2. 2.

    Mead J: J Appl Physiol. 1970, 28 (5): 596-608.

  3. 3.

    Patlak CS: J Cereb Blood Flow Metab. 1983, 3 (1): 1-7. 10.1038/jcbfm.1983.1.

  4. 4.

    Cressoni M: Am J Respir Crit Care Med. 2013

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Author information

Correspondence to M Cressoni.

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Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0), which permits use, duplication, adaptation, distribution, and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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Cressoni, M., Chiumello, D., Brioni, M. et al. Lung inhomogeneities, inflation and [18F]FDG uptake rate in ards. ICMx 3, A90 (2015) doi:10.1186/2197-425X-3-S1-A90

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Keywords

  • Lung Volume
  • Normal Lung
  • Lung Parenchyma
  • Stress Raiser
  • Actual Classification