Very early ventilated lung regions appear as light blue pixels. In each map, dark red pixels indicate lung regions that are lately ventilated during a slow inflation maneuver. 13) during decremental titration of positive end-expiratory pressure (PEEP). ( Middle) Exemplary delay maps from a representative animal (pig No. Regional ventilation delay inhomogeneity expressed as SD of all single pixel regional ventilation delay-values.
( Right) Delay map to visualize all regional ventilation delay indices. Ventilation delay time (ΔtRVD) when the regional impedance time curve reaches a threshold of 40% of the maximal local impedance change. All curves are normalized to the beginning (t min) and end (t max) of the slow inflation maneuver: blue, right ventral pixel red, right dorsal pixel yellow, left dorsal pixel. ( Middle) Normalized regional impedance/time curves of three exemplary pixels. ( Left) Functional image (ventilation map) recorded by electrical impedance tomography during a slow inflation breath of 12 ml/kg ideal body weight. ( Top) Calculation of regional ventilation delay inhomogeneity, schematic description. 22, 24 To induce lung injury, abdominal pressure (measured in the urinary bladder) was increased to 15 mmHg by infusion of 0.9% saline into the abdominal cavity, 22, 24, 25 followed by titrated central venous injections of oleic acid, until a stable Pa o 2/fractional inspired oxygen concentration (F io 2) ratio of less than 200 mmHg was reached. 22, 24 Tracheotomy and instrumentation were performed as previously described.
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