[Evaluation of hemodynamic and respiratory variables in patients with acute respiratory distress syndrome in two ventilatory modes].

The aim of the present study was to evaluate the hemodynamic and respiratory variations in patients with acute respiratory distress syndrome (ARDS) under two conditions: volume controlled ventilation (VCV) and pressure controlled inverse ratio ventilation (PCIRV). Seventeen patients with ARDS and the following criteria were included: lung injury score > 2.5 and peak inspiratory pressure > or = 40 cm H2O under VCV, constant flow and I/E ratio of 1/2. Measurements were obtained in VCV and after one hour in PCIRV with I/E ratio 2/1 using a similar PEEP value than VCV. PCIRV was accompanied by a significant lower tidal volume (736.10 +/- 119.20 vs 540.35 +/- 84.66 p < 0.001), peak inspiratory pressure (43.60 +/- 5.50 vs 26.26 +/- 3.47 p < 0.0001) and plateau pressure (37.64 +/- 3.70 vs 25.30 +/- 3.50 p < 0.001) and a significant higher: respiratory frequency (17.70 +/- 2.10 vs 20.94 +/- 3.38 p < 0.002), mean airway pressure (16.20 +/- 3.00 vs 19.41 +/- 2.80 p < 0.003) and static compliance (25.84 +/- 5.42 vs 35.18 +/- 9.39 p < 0.002). Similar values in the hemodynamic and oxygenation variables were observed between both groups. Our results show that PCIRV allow to ventilate patients with lower peak inspiratory and plateau pressures without significant changes in hemodynamic and oxygenation parameters. The conventional tidal volumes are excessive for lungs with SDRA, which is shown with the improvement in the static compliance and the airway pressures in PCIRV. PCIRV mode at the same PEEPt level as VCV, with normal I/E ratio does not improve the oxygenation, despite the higher level of the mean airway pressure.