Individualized flow-controlled ventilation compared to best clinical practice pressure-controlled ventilation: a prospective randomized porcine study.

Abstract

Background: Flow-controlled ventilation is a novel ventilation method which allows to individualize ventilation according to dynamic lung mechanic limits based on direct tracheal pressure measurement at a stable constant gas flow during inspiration and expiration. The aim of this porcine study was to compare individualized flow-controlled ventilation (FCV) and current guideline-conform pressure-controlled ventilation (PCV) in long-term ventilation.Methods: Anesthetized pigs were ventilated with either FCV or PCV over a period of ten hours with a fixed FiO2 of 0.3. FCV settings were individualized by compliance-guided positive end-expiratory pressure (PEEP) and peak pressure (Ppeak) titration. Flow was adjusted to maintain normocapnia and the inspiration to expiration ratio (I:E ratio) was set at 1:1. PCV was performed with a PEEP of 5 cm H2O and Ppeak was set to achieve a tidal volume (VT) of 7 ml/kg. The respiratory rate was adjusted to maintain normocapnia and the I:E ratio was set at 1:1.5. Repeated measurements during observation period were assessed by linear mixed-effects model.Results: In FCV (n=6) respiratory minute volume was significantly reduced (6.0 vs 12.7, MD -6.8 (-8.2 to -5.4) l/min; p<0.001) as compared to PCV (n=6). Oxygenation was improved in the FCV group (paO2 119.8 vs 96.6, MD 23.2 (9.0 to 37.5) torr; 15.97 vs 12.87, MD 3.10 (1.19 to 5.00) kPa; p=0.010) and CO2 removal was more efficient (paCO2 40.1 vs 44.9, MD -4.7 (-7.4 to -2.0) torr; 5.35 vs 5.98, MD -0.63 (-0.99 to -0.27) kPa; p=0.006). Ppeak and driving pressure were comparable in both groups, whereas PEEP was significantly lower in FCV (p=0.002). Computed tomography revealed a significant reduction in non-aerated lung tissue in individualized FCV (p=0.026) and no significant difference in overdistended lung tissue, although a significantly higher VT was applied (8.2 vs 7.6, MD 0.7 (0.2 to 1.2) ml/kg; p=0.025).Conclusion: Our long-term ventilation study demonstrates the applicability of a compliance-guided individualization of FCV settings, which resulted in significantly improved gas exchange and lung tissue aeration without signs of overinflation as compared to best clinical practice PCV.