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Open Access Original research article

Dynamics of regional lung aeration determined by electrical impedance tomography in patients with acute respiratory distress syndrome

Sven Pulletz1*, Matthias Kott2, Gunnar Elke2, Dirk Schädler2, Barbara Vogt2, Norbert Weiler2 and Inéz Frerichs2

Author Affiliations

1 Department of Anaesthesiology and Intensive Care Medicine, Klinikum Osnabrück, Am Finkenhügel 1, 49076 Osnabrück, Germany

2 Department of Anaesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, 24105 Keil, Germany

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Multidisciplinary Respiratory Medicine 2012, 7:44  doi:10.1186/2049-6958-7-44

Published: 15 November 2012

Abstract

Background

Lung tissue of patients with acute respiratory distress syndrome (ARDS) is heterogeneously damaged and prone to develop atelectasis. During inflation, atelectatic regions may exhibit alveolar recruitment accompanied by prolonged filling with air in contrast to regions with already open alveoli with a fast increase in regional aeration. During deflation, derecruitment of injured regions is possible with ongoing loss in regional aeration. The aim of our study was to assess the dynamics of regional lung aeration in mechanically ventilated patients with ARDS and its dependency on positive end-expiratory pressure (PEEP) using electrical impedance tomography (EIT).

Methods

Twelve lung healthy and twenty ARDS patients were examined by EIT during sustained step increases in airway pressure from 0, 8 and 15 cm H2O to 35 cm H2O and during subsequent step decrease to the corresponding PEEP. Regional EIT waveforms in the ventral and dorsal lung regions were fitted to bi-exponential equations. Regional fast and slow respiratory time constants and the sizes of the fast and slow compartments were subsequently calculated.

Results

ARDS patients exhibited significantly lower fast and slow time constants than the lung healthy patients in ventral and dorsal regions. The time constants were significantly affected by PEEP and differed between the regions. The size of the fast compartment was significantly lower in ARDS patients than in patients with healthy lung under all studied conditions.

Conclusion

These results show that regional lung mechanics can be assessed by EIT. They reflect the lower respiratory system compliance of injured lungs and imply more pronounced regional recruitment and derecruitment in ARDS patients.

Keywords:
Acute lung injury; Electrical impedance tomography; EIT; Respiratory time constants