Regional ventilation and respiratory system compliance.

<p>Ventrodorsal profiles of regional tidal volume (V<sub>T</sub>) (A), regional respiratory system compliance (C<sub>RS</sub>) (C) and differences in regional V<sub>T</sub> (ΔV<sub>T</sub>) (B) and regional C<sub>RS</sub> (ΔC<sub>RS</sub>) (D) with respect to baseline (mean values ±SD in 10 animals). Panel A (V<sub>T</sub> [%]) shows the relative distribution of V<sub>T</sub> in 32 horizontal layers in% of overall V<sub>T</sub> in the chest cross-section. Panel B (ΔV<sub>T</sub> [%]) indicates the respective differences in regional V<sub>T</sub> compared with baseline. It shows a shift in ventilation toward the dorsal regions already with higher V<sub>T</sub> at time point 1 in normal lung and more pronounced shifts at points 3 through 6 with a PEEP set 2 cm H<sub>2</sub>O above the lower inflection point in acute lung injury (ALI). Panel C (C<sub>RS</sub> [ml/kg H<sub>2</sub>O]) shows regional C<sub>RS</sub> in the same 32 layers with the respective differences to baseline provided in panel D (ΔC<sub>RS</sub> [ml/kg H<sub>2</sub>O]). The differences in regional C<sub>RS</sub> indicate slightly lower and higher C<sub>RS</sub> in the ventral and dorsal regions at time point 1. Significantly lower values were found in layers 7 to 12 and significantly higher ones in layers 16 to 25 (layers counting from 1 to 32 in the ventrodorsal direction). ALI (time point 2) resulted in significant decrease in C<sub>RS</sub> in all layers. A small increase in C<sub>RS</sub> in the dorsal regions (significant in layers 23 and 24) with the decreased C<sub>RS</sub> in the ventral regions (significant in layers 1 to 17 and 27 and 28) at time point 3/5. At all other three time points, the findings were comparable. High V<sub>T</sub>, ventilation with 10 ml/kg BW, low V<sub>T</sub>, ventilation with 5 ml/kg BW.</p>