title: Effect of PEEP on regional ventilation during laparoscopic surgery monitored by electrical impedance tomography.
abstract: BACKGROUND
  Anesthesia per se and pneumoperitoneum during laparoscopic surgery lead to atelectasis and impairment of oxygenation. We hypothesized that a ventilation with positive end-expiratory pressure (PEEP) during general anesthesia and laparoscopic surgery leads to a more homogeneous ventilation distribution as determined by electrical impedance tomography (EIT). Furthermore, we supposed that PEEP ventilation in lung-healthy patients would improve the parameters of oxygenation and respiratory compliance.
  
  
  METHODS
  Thirty-two patients scheduled to undergo laparoscopic cholecystectomy were randomly assigned to be ventilated with ZEEP (0 cmH(2)O) or with PEEP (10 cmH(2)O) and a subsequent recruitment maneuver. Differences in regional ventilation were analyzed by the EIT-based center-of-ventilation index (COV), which quantifies the distribution of ventilation and indicates ventilation shifts.
  
  
  RESULTS
  Higher amount of ventilation was examined in the dorsal parts of the lungs in the PEEP group. Throughout the application of PEEP, a lower shift of ventilation was found, whereas after the induction of anesthesia, a remarkable ventral shift of ventilation in ZEEP-ventilated patients (COV: ZEEP, 40.6 ± 2.4%; PEEP, 46.5 ± 3.5%; P<0.001) was observed. Compared with the PEEP group, ZEEP caused a ventral misalignment of ventilation during pneumoperitoneum (COV: ZEEP, 41.6 ± 2.4%; PEEP, 44 ± 2.7%; P=0.013). Throughout the study, there were significant differences in the parameters of oxygenation and respiratory compliance with improved values in PEEP-ventilated patients.
  
  
  CONCLUSIONS
  The effect of anesthesia, pneumoperitoneum, and different PEEP levels can be evaluated by EIT-based COV monitoring. An initial recruitment maneuver and a PEEP of 10 cmH(2)O preserved homogeneous regional ventilation during laparoscopic surgery in most, but not all, patients and improved oxygenation and respiratory compliance.
authors.affiliation: Department of Anesthesiology, University of Lübeck, Lübeck, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Karsten
authors.forename: H
authors.initials: H
authors.lastname: Luepschen
authors.forename: M
authors.initials: M
authors.lastname: Grossherr
authors.forename: H-P
authors.initials: HP
authors.lastname: Bruch
authors.forename: S
authors.initials: S
authors.lastname: Leonhardt
authors.forename: H
authors.initials: H
authors.lastname: Gehring
authors.forename: Torsten
authors.initials: T
authors.lastname: Meier
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000768:Anesthesia, General; D001784:Blood Gas Analysis; D003627:Data Interpretation, Statistical; D017097:Electric Impedance; D005260:Female; D006801:Humans; D010535:Laparoscopy / Q000379:methods*; D008170:Lung Compliance / Q000502:physiology; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D011028:Pneumoperitoneum, Artificial; D011175:Positive-Pressure Respiration; D012121:Respiration, Artificial / Q000379:methods*; D014054:Tomography / Q000379:methods*; D055815:Young Adult