Fig. 2.
Experimental protocol: animal preparation and lung injury induction. Incremental PEEP- and Fio2-titration without a preceding recruitment maneuver according to the ARDS Network lower PEEP/Fio2 table to define table PEEP. Maximal recruitment maneuver until Pao2 > 400 mmHg. Blood gas measurements and electrical impedance tomography during decremental PEEP titration to define “maximal oxygenation PEEP” and “minimal tidal recruitment PEEP.” Animals were transported to the single photon emission computed tomography lab without interrupting mechanical ventilation using baseline settings. Investigation of the previously defined table PEEP, maximal oxygenation PEEP, and minimal tidal recruitment PEEP in a block-wise randomized order. To prevent influences of lung volume history, systematic derecruitment and/or recruitment and a stability check were performed before every measurement cycle. During all regional measurements Fio2 was kept constant as set according to the PEEP/Fio2 table during table PEEP. ALI, acute lung injury; ARDS, acute respiratory distress syndrome; BGA, blood gas analysis; EIT, electrical impedance tomography; Fio2, fractional inspired oxygen concentration; PEEP, positive end-expiratory pressure; , ventilation/perfusion.