title: Perioperative assessment of regional ventilation during changing body positions and ventilation conditions by electrical impedance tomography.
abstract: BACKGROUND
  Lung-protective ventilation is claimed to be beneficial not only in critically ill patients, but also in pulmonary healthy patients undergoing general anaesthesia. We report the use of electrical impedance tomography for assessing regional changes in ventilation, during both spontaneous breathing and mechanical ventilation, in patients undergoing robot-assisted radical prostatectomy.
  
  
  METHODS
  We performed electrical impedance tomography measurements in 39 patients before induction of anaesthesia in the sitting (M1) and supine position (M2), after the start of mechanical ventilation (M3), during capnoperitoneum and Trendelenburg positioning (M4), and finally, in the supine position after release of capnoperitoneum (M5). To quantify regional changes in lung ventilation, we calculated the centre of ventilation and 'silent spaces' in the ventral and dorsal lung regions that did not show major impedance changes.
  
  
  RESULTS
  Compared with the awake supine position [2.3% (2.3)], anaesthesia and mechanical ventilation induced a significant increase in silent spaces in the dorsal dependent lung [9.2% (6.3); P<0.05]. Capnoperitoneum and the Trendelenburg position led to a significant increase in such spaces [11.5% (8.9)]. Silent space in the ventral lung remained constant throughout anaesthesia.
  
  
  CONCLUSIONS
  Electrical impedance tomography was able to identify and quantify on a breath-by-breath basis circumscribed areas, so-called silent spaces, within healthy lungs that received little or no ventilation during general anaesthesia, capnoperitoneum, and different body positions. As these silent spaces are suggestive of atelectasis on the one hand and overdistension on the other, they might become useful to guide individualized protective ventilation strategies to mitigate the side-effects of anaesthesia and surgery on the lungs.
authors.affiliation: Department of Anesthesiology, Center of Anesthesiology and Intensive Care Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Ukere
authors.affiliation: Department of Anesthesiology, Center of Anesthesiology and Intensive Care Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany a.maerz@uke.de.
authors.forename: A
authors.initials: A
authors.lastname: März
authors.affiliation: Department of Anesthesiology, Center of Anesthesiology and Intensive Care Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: K H
authors.initials: KH
authors.lastname: Wodack
authors.affiliation: Department of Anesthesiology, Center of Anesthesiology and Intensive Care Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: C J
authors.initials: CJ
authors.lastname: Trepte
authors.affiliation: Martini Klinik, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Haese
authors.affiliation: Swisstom AG, Landquart, Switzerland.
authors.forename: A D
authors.initials: AD
authors.lastname: Waldmann
authors.affiliation: Swisstom AG, Landquart, Switzerland.
authors.forename: S H
authors.initials: SH
authors.lastname: Böhm
authors.affiliation: Department of Anesthesiology, Center of Anesthesiology and Intensive Care Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: D A
authors.initials: DA
authors.lastname: Reuter
mesh_terms: D000403:Airway Resistance; D000768:Anesthesia, General; D003422:Critical Care; D017097:Electric Impedance; D018475:Head-Down Tilt; D006801:Humans; D008297:Male; D056888:Patient Positioning; D010537:Peritoneum / Q000000981:diagnostic imaging; D016684:Prone Position; D011468:Prostatectomy; D001261:Pulmonary Atelectasis / Q000000981:diagnostic imaging; D012123:Pulmonary Ventilation; D012121:Respiration, Artificial; D065287:Robotic Surgical Procedures; D016683:Supine Position; D014054:Tomography / Q000379:methods*
keywords: atelectasis; electrical impedance; electrodes; perioperative period; respiration, artificial