Volume 19 Supplement 1

35th International Symposium on Intensive Care and Emergency Medicine

Open Access

Perioperative assessment of regional ventilation during changing body positions and ventilation conditions by electrical impedance tomography with increased spatial resolution and signal quality

  • A März1,
  • A Ukere1,
  • K Wodack1,
  • C Trepte1,
  • A Waldmann2,
  • S Böhm2 and
  • D Reuter1
Critical Care201519(Suppl 1):P249


Published: 16 March 2015


Electrical impedance tomography (EIT) is a functional imaging technology allowing one to regionally monitor aeration of the lungs. We used EIT with increased signal quality and spatial resolution to describe and quantify the regional changes in aeration caused by body position, both during spontaneous breathing and mechanical ventilation in pulmonary healthy patients undergoing laparoscopic prostatectomy.


In 40 patients we performed EIT measurements at five points of time (Table 1) with the Swisstom BB2 prototype. Thirty-two electrodes were used to apply weak alternating currents to the thorax and to measure the resulting voltages, from which tomographic images of the changes in regional impedance caused by ventilation were created. We describe the ventilation distribution using a novel EIT lung function parameter called Silent Spaces that provides information about areas that do not receive much or any air during tidal breathing and are divided into nondependent (NSS) and dependent Silent Spaces (DSS) using a reference line that runs perpendicular to the gravity vector right through the centre of ventilation. NSS and DSS are expressed as a percentage of the total lung area.

Table 1








(sitting, spontaneous breathing)

(supine, spontaneous breathing)

(ventilated, supine position)

(ventilated, 30° head down position)

(ventilated, supine position)

NSS (%)

5.25 ± 2.9

4.12 ± 1.89§

3.05 ± 1.9§

2.8 ± 2.7§

2.67 ± 1.9§

DSS (%)

0.07 ± 0.3

2.29 ± 2.3§

9.23 ± 6.3§

11.5 ± 8.9§*

8.5 ± 5.8§


Perioperative changes of NSS and DSS are shown in Table 1 as mean ± SD. Statistically significant differences marked by § when compared with 1 or by * when compared with 3 (P < 0.05).


We describe for the first time the mapping of Silent Spaces during spontaneous breathing and changing ventilation conditions and body positions in patients with healthy lungs using EIT. This mapping of Silent Spaces might prove useful for developing perioperative protective ventilation strategies.

Authors’ Affiliations

University Medical Center Hamburg-Eppendor, University Hamburg
Swisstom AG


© März et al.; licensee BioMed Central Ltd. 2015

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.