Assessment of regional lung recruitment and derecruitment during a PEEP trial based on electrical impedance tomography.
OBJECTIVE
To investigate whether electrical impedance tomography (EIT) is capable of monitoring regional lung recruitment and lung collapse during a positive end-expiratory pressure (PEEP) trial.


METHODS
Experimental animal study of acute lung injury.


METHODS
Six pigs with saline-lavage-induced acute lung injury.


METHODS
An incremental and decremental PEEP trial at ten pressure levels was performed. Ventilatory, gas exchange, and hemodynamic parameters were automatically recorded. EIT and computed tomography (CT) scans of the same slice were simultaneously taken at each PEEP level.


RESULTS
A significant correlation between EIT and CT analyses of end-expiratory gas volumes (r=0.98 up to 0.99) and tidal volumes (r=0.55 up to r=0.88) could be demonstrated. Changes in global and regional tidal volumes and arterial oxygenation (PaO2/FiO2) demonstrated recruitment/derecruitment during the trial, but at different onsets. During the decremental trial, derecruitment first occurred in dependent lung areas. This was indicated by lowered regional tidal volumes measured in this area and by a decrease of PaO2/FiO2. At the same time, the global tidal volume still continued to increase, because the increase of ventilation of the non-dependent areas was higher than the loss in the dependent areas. This indicates that opposing regional changes might cancel each other out when combined in a global parameter.


CONCLUSIONS
EIT is suitable for monitoring the dynamic effects of PEEP variations on the regional change of tidal volume. It is superior to global ventilation parameters in assessing the beginning of alveolar recruitment and lung collapse.
Meier
Torsten
T
Department of Anesthesiology, University Medical Center Schleswig-Holstein, Campus Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany. meiert@uni-luebeck.de
Luepschen
Henning
H
Karsten
Jan
J
Leibecke
Thorsten
T
Grossherr
Martin
M
Gehring
Hartmut
H
Leonhardt
Steffen
S
D000818:Animals; D018893:Bronchoalveolar Lavage; D004195:Disease Models, Animal; D017097:Electric Impedance; D008168:Lung / Q000503:physiopathology*; D008170:Lung Compliance; D008991:Monitoring, Physiologic / Q000379:methods; D011175:Positive-Pressure Respiration / Q000379:methods*; D011659:Pulmonary Gas Exchange; D012128:Respiratory Distress Syndrome / Q000097:blood / Q000503:physiopathology* / Q000628:therapy*; D013552:Swine; D014054:Tomography / Q000379:methods