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  • Letter
  • Open Access

Methodology of electrical impedance tomography-derived measures of regional lung ventilation

Critical Care201418:635

https://doi.org/10.1186/s13054-014-0635-5

  • Published:

Abstract

No abstract

Keywords

  • Electrical Impedance Tomography
  • Regional Lung
  • Lung Ventilation
  • Regional Compliance
  • Methodological Figure

In the previous issue of Critical Care, we read with interest the article by Blankman and colleagues [1], who studied the performance of various electrical impedance tomography (EIT)-derived measures in detecting the `best’ positive end-expiratory pressure. The aim of that study is relevant; however, the article contains some methodological inaccuracies that need to be clarified.

One of the EIT measures used to characterize ventilation distribution is the center of ventilation (COV), first introduced in [2]. The authors refer appropriately to an article that contains a methodological figure illustrating how COV is derived from EIT ventilation images [3]. However, the authors incorrectly state that COV is the ratio between the EIT-derived ventilations in the dorsal and whole-image regions, provide a wrong equation 6, and attribute it to [3].

It is important for the understanding of EIT findings to appreciate that Figure one [1] does not show images of `impedance’ and the degree of `aeration’ (legend) but of tidal impedance differences representing regional tidal volumes. Regional ventilation delay (RVD) was analyzed not in [4], but in [5], where it was calculated in each pixel. A two-dimensional map was produced from these values, and standard deviation was calculated as an aggregate measure of ventilation homogeneity. Equation 3 regarding RVD calculation was used in [5], not in [6], where an additional multiplication by maximum impedance amplitude of the studied low-flow inflation was included. It is not clear which percentages of regional compliance are presented in Figure two B [1].

EIT is currently at an important stage of its development. Its clinical use might be fostered by implementation of accurate analysis tools.

Abbreviations

COV: 

Center of ventilation

EIT: 

Electrical impedance tomography

RVD: 

Regional ventilation delay

Declarations

Authors’ Affiliations

(1)
Department of Anaesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Campus Kiel, Arnold-Heller-Str. 3, Kiel, D-24145, Germany

References

  1. Blankman P, Hasan D, Groot Jebbink E, Gommers D: Detection of `best’ positive end-expiratory pressure derived from electrical impedance tomography parameters during a decremental positive end-expiratory pressure trial. Crit Care. 2014, 18: R95-10.1186/cc13866.View ArticleGoogle Scholar
  2. Frerichs I, Hahn G, Golisch W, Kurpitz M, Burchardi H, Hellige G: Monitoring perioperative changes in distribution of pulmonary ventilation by functional electrical impedance tomography. Acta Anaesthesiol Scand. 1998, 42: 721-726. 10.1111/j.1399-6576.1998.tb05308.x.View ArticleGoogle Scholar
  3. Frerichs I, Dargaville PA, van Genderingen H, Morel DR, Rimensberger PC: Lung volume recruitment after surfactant administration modifies spatial distribution of ventilation. Am J Respir Crit Care Med. 2006, 174: 772-779. 10.1164/rccm.200512-1942OC.View ArticleGoogle Scholar
  4. Zhao Z, Steinmann D, Frerichs I, Guttmann J, Moller K: PEEP titration guided by ventilation homogeneity: a feasibility study using electrical impedance tomography. Crit Care. 2010, 14: R8-10.1186/cc8860.View ArticleGoogle Scholar
  5. Muders T, Luepschen H, Zinserling J, Greschus S, Fimmers R, Guenther U, Buchwald M, Grigutsch D, Leonhardt S, Putensen C, Wrigge H: Tidal recruitment assessed by electrical impedance tomography and computed tomography in a porcine model of lung injury. Crit Care Med. 2012, 40: 903-911. 10.1097/CCM.0b013e318236f452.View ArticleGoogle Scholar
  6. Wrigge H, Zinserling J, Muders T, Varelmann D, Gunther U, von der Groeben C, Magnusson A, Hedenstierna G, Putensen C: Electrical impedance tomography compared with thoracic computed tomography during a slow inflation maneuver in experimental models of lung injury. Crit Care Med. 2008, 36: 903-909. 10.1097/CCM.0B013E3181652EDD.View ArticleGoogle Scholar

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