Analysis of efficacy and safety markers during the ventilator hyperinflation technique: controlled and randomized study

Abstract

Introduction: Ventilator hyperinflation (VHI) has been shown to be effective in improving respiratory mechanics, secretion removal, and gas exchange in mechanically ventilated patients; however, there are no recommendations on the best ventilator settings to perform the technique. Objective: The aim of this study was to compare six modes of VHI, concerning physiological markers of efficacy and safety criteria, in order to support the optimal VHI settings selection for mechanically ventilated patients. Methods: In a crossover study, every included mechanically ventilated patient underwent six modes of VHI in a randomized order: Volume Control Continuous Mandatory Ventilation (VC-CMV) with inspiratory flow = 20Lpm (VC-CMV20), VC-CMV with inspiratory flow = 50Lpm (VC-CMV50), Pressure Control Continuous Mandatory Ventilation (PC-CMV) with inspiratory time = 1s. (PC-CMV1), PC-CMV with inspiratory time = 3s. (PC-CMV3), Pressure Support Ventilation (PSV) with cycling off = 10% of peak inspiratory flow (PSV10), and PSV with cycling off = 25% of peak inspiratory flow (PSV25). Maximum expansion, expiratory flow bias criteria, overdistension, asynchronies and hemodynamic variables were assessed during the interventions. Results: The comparison between VHI modes showed that VC-CMV20 was the most effective, followed by PC-CMV3 and PSV10. Mean arterial pressure reduced in VC-CMV20 and VC-CMV50 (P<0.05), with an effect size of 0.62 and 0.51, respectively. The modes PC-CMV3 and PSV10 showed the highest values of alveolar pressure, with 93% of the cases above 30cmH2O. The modes with more asynchronies were VC-CMV20 and PC-CMV3, whilst in PC-CMV1 and PSV modes there were few cases. Conclusion: Considering physiological markers of effectiveness, the VHI modes VC-CMV20, PC-CMV3 and PSV10 are the most effective. As VHI techniques are associated to patient-ventilator asynchronies, PSV10 is indicated for patients in assisted mechanical ventilation, whilst VC-CMV20 and PC-CMV3 are indicated for patients in controlled modes. Aiming at reducing the incidence of alveolar overdistension and hemodynamic repercussions, a pressure limit of 35cmH2O or less should be used, as long as the volume delivered achieve at least 50% above the ideal tidal volume.