title: Assessment of changes in distribution of lung perfusion by electrical impedance tomography.
abstract: BACKGROUND
  Electrical impedance tomography (EIT) is able to detect variations in regional lung electrical impedance associated with changes in both air and blood content and potentially capable of assessing regional ventilation-perfusion relationships. However, regional lung perfusion is difficult to determine because the impedance changes synchronous with the heart rate are of very small amplitude.
  
  
  OBJECTIVE
  The aim of our study was to determine the redistribution of lung perfusion elicited by one-lung ventilation using EIT with a novel region-of-interest analysis.
  
  
  METHODS
  Ten patients (65 +/- 9 years, mean age +/- SD) scheduled for elective chest surgery were studied after intubation with a double-lumen endotracheal tube during bilateral and unilateral ventilation of the right and left lungs. EIT data were acquired at a rate of 25 scans/s. Relative impedance changes synchronous with the heart rate were evaluated in the right and left lung regions.
  
  
  RESULTS
  During bilateral ventilation, the mean right-to-left lung ratio of the sum of heart rate-related impedance changes was 1.12 +/- 0.20, but the ratio significantly changed (0.81 +/- 0.16 and 1.48 +/- 0.37) during unilateral left- and right-lung ventilation with reduced perfusion of the non-ventilated lung. Increased perfusion most likely occurred in the ventilated lung because the impedance values summed over both regions did not change (0.62 +/- 0.23 vs. 0.58 +/- 0.22) compared with bilateral ventilation.
  
  
  CONCLUSIONS
  Our results indicate that redistribution of regional lung perfusion can be assessed by EIT during one-lung ventilation. The performance of EIT in detecting changes in lung perfusion in even smaller lung regions remains to be established.
authors.affiliation: Department of Anesthesiology and Intensive Care Medicine, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany. frerichs@anaesthesie.uni-kiel.de
authors.forename: Inéz
authors.initials: I
authors.lastname: Frerichs
authors.forename: Sven
authors.initials: S
authors.lastname: Pulletz
authors.forename: Gunnar
authors.initials: G
authors.lastname: Elke
authors.forename: Florian
authors.initials: F
authors.lastname: Reifferscheid
authors.forename: Dirk
authors.initials: D
authors.lastname: Schadler
authors.forename: Jens
authors.initials: J
authors.lastname: Scholz
authors.forename: Norbert
authors.initials: N
authors.lastname: Weiler
mesh_terms: D000368:Aged; D045422:Continuous Positive Airway Pressure; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011652:Pulmonary Circulation; D014054:Tomography