title: No change in the regional distribution of tidal volume during lateral posture in mechanically ventilated patients assessed by electrical impedance tomography.
abstract: We assessed the distribution of regional lung ventilation during moderate and steep lateral posture using electrical impedance tomography (EIT) in mechanically ventilated patients. Seven patients were placed on a kinetic treatment table. An elastic belt containing 16 electrodes was placed around the chest and was connected to the EIT device. Patients were moved to left and right lateral positions in a stepwise (10 degrees ) mode up to 60 degrees. EIT images [arbitrary units (AU)] were generated and scanned for assessment of relative ventilation distribution changes [tidal volume (V(T))]. A calibration procedure of arbitrary units (AUs) versus ventilator-derived V(T) performed in all patients during three predefined positions (supine, 60 degrees-left dependent and 60 degrees-right-dependent) showed a significant correlation between V(T) in supine, left and right lateral positions with the corresponding AUs (r(2) = 0.356, P<0.05). Changes in V(T) were calculated and compared to supine position, and specific regions of interest (ROIs) were analysed. In our study, in contrast to recent findings, a change in lateral positions did not induce a significant change in regional tidal volume distribution. In right lateral positions, a broader variation of V(T) with a trend towards an increase in the dependently positioned lung was observed in comparison with supine. Lateral positioning promotes the redistribution of ventilation to the ventral regions of the lung. The use of EIT technology might become a helpful tool for understanding and guiding posture therapy in mechanically ventilated patients.
authors.affiliation: Department of Anesthesiology, Regensburg University Hospital, Regensburg, Germany. thomas.bein@klinik.uni-regensburg.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Bein
authors.forename: Franz
authors.initials: F
authors.lastname: Ploner
authors.forename: Markus
authors.initials: M
authors.lastname: Ritzka
authors.forename: Michael
authors.initials: M
authors.lastname: Pfeifer
authors.forename: Hans J
authors.initials: HJ
authors.lastname: Schlitt
authors.forename: Bernhard M
authors.initials: BM
authors.lastname: Graf
mesh_terms: D055371:Acute Lung Injury / Q000097:blood / Q000503:physiopathology / Q000628:therapy*; D000328:Adult; D001794:Blood Pressure; D017097:Electric Impedance; D006339:Heart Rate; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D056888:Patient Positioning; D010865:Pilot Projects; D011187:Posture; D011237:Predictive Value of Tests; D012121:Respiration, Artificial; D013990:Tidal Volume; D014054:Tomography / Q000379:methods*
chemical_list: D010100:Oxygen