Selecting the Best Ventilator Hyperinflation Settings (VHI1)

Selecting the Best Ventilator Hyperinflation Settings Based on Physiologic Markers: Randomized Controlled Study

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. Thus, 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. In a randomized, controlled and crossover study, 30 mechanically ventilated patients underwent 6 modes of ventilator hyperinflation. The maximum expansion (tidal volume), expiratory flow bias criteria (inspiratory and expiratory flow patterns), overdistension (alveolar pressure), asynchronies and hemodynamic variables (mean arterial pressure and heart rate) were assessed during the interventions.

Background: 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. Thus, 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). The maximum expansion (tidal volume), expiratory flow bias criteria (inspiratory and expiratory flow patterns), over-distension (alveolar pressure), asynchronies and hemodynamic variables (mean arterial pressure and heart rate) were assessed during the interventions.

Application of a ventilator hyperinflation intervention with Volume Control Continuous Mandatory Ventilation (VC-CMV) with an inspiratory flow of 20Lpm.

Application of a ventilator hyperinflation intervention with Volume Control Continuous Mandatory Ventilation (VC-CMV) with an inspiratory flow of 50Lpm.

Application of a ventilator hyperinflation intervention with Pressure Control Continuous Mandatory Ventilation (PC-CMV1) with an inspiratory time of 1 second.

Application of a ventilator hyperinflation intervention with Pressure Control Continuous Mandatory Ventilation (PC-CMV1) with an inspiratory time of 3 seconds.

Application of a ventilator hyperinflation intervention with Pressure Support Ventilation (PSV) with a cycling off of 10% of peak inspiratory flow.

Application of a ventilator hyperinflation intervention with Pressure Support Ventilation (PSV) with a cycling off of 25% of peak inspiratory flow.

Application of a ventilator hyperinflation intervention with Volume Control Continuous Mandatory Ventilation (VC-CMV). The inspiratory flow was set at 20Lpm and the tidal volume was increased in steps of 200mL until the peak airway pressure of 40cmH2O was achieved. After achieving the target pressure, this ventilatory regimen lasted 15 minutes. Positive end expiratory pressure and the inspired oxygen fraction were not modified.

Application of a ventilator hyperinflation intervention with Volume Control Continuous Mandatory Ventilation (VC-CMV). The inspiratory flow was set at 50Lpm and the tidal volume was increased in steps of 200mL until the peak airway pressure of 40cmH2O was achieved. After achieving the target pressure, this ventilatory regimen lasted 15 minutes. Positive end expiratory pressure and the inspired oxygen fraction were not modified.

Application of a ventilator hyperinflation intervention with Pressure Control Continuous Mandatory Ventilation (PC-CMV1). The inspiratory time was set at 1 second and the pressure control was increased until a peak pressure of 40cmH2O was achieved. After achieving the target pressure, this ventilatory regimen lasted 15 minutes. Positive end expiratory pressure and the inspired oxygen fraction were not modified.

Application of a ventilator hyperinflation intervention with Pressure Control Continuous Mandatory Ventilation (PC-CMV1). The inspiratory time was set at 3 seconds and the pressure control was increased until a peak pressure of 40cmH2O was achieved. After achieving the target pressure, this ventilatory regimen lasted 15 minutes. Positive end expiratory pressure and the inspired oxygen fraction were not modified.

Application of a ventilator hyperinflation intervention with Pressure Support Ventilation (PSV). The cycling off was set at 10% of peak inspiratory flow and the pressure support was increased until a peak pressure of 40cmH2O was achieved. After achieving the target pressure, this ventilatory regimen lasted 15 minutes. Positive end expiratory pressure and the inspired oxygen fraction were not modified.

Application of a ventilator hyperinflation intervention with Pressure Support Ventilation (PSV). The cycling off was set at 25% of peak inspiratory flow and the pressure support was increased until a peak pressure of 40cmH2O was achieved. After achieving the target pressure, this ventilatory regimen lasted 15 minutes. Positive end expiratory pressure and the inspired oxygen fraction were not modified.

Dichotomous variable, defined as achieving a peak inspiratory flow rate (PIFR) less than 90% of the peak expiratory flow rate (PEFR)

Inclusion Criteria: Patients under mechanical ventilation for more than 48h Exclusion Criteria: mucus hypersecretion (defined as the need for suctioning < 2-h intervals), absence of respiratory drive, atelectasis, severe bronchospasm, positive end expiratory pressure > 10cmH2O, PaO2-FiO2 relationship < 150, mean arterial pressure < 60mmHg, inotrope requirement equivalent to >15 ml/h total of adrenaline and noradrenalin, intracranial pressure > 20mmHg

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