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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
30
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.
Peak inspiratory to expiratory flow ratio
Dichotomous variable, defined as achieving a peak inspiratory flow rate (PIFR) less than 90% of the peak expiratory flow rate (PEFR)
Time frame: Ten minutes after the onset of intervention.
Peak expiratory flow higher than 40 Lpm
Dichotomous variable, defined as achieving a PEFR higher than 40 l/min
Time frame: Ten minutes after the onset of intervention.
Difference between peak inspiratory and expiratory flows.
Dichotomous variable, defined as achieving a difference higher than 17Lpm.
Time frame: Ten minutes after the onset of intervention.
Pulmonary expansion
Percentage of tidal volume above the normal tidal volume (estimated as 6mL/kg).
Time frame: Ten minutes after the onset of intervention.
Mean arterial pressure
Mean arterial pressure verified using the multi-parameter monitor.
Time frame: Ten minutes after the onset of intervention.
Heart Rate
Heart rate verified using the multi-parameter monitor.
Time frame: Ten minutes after the onset of intervention.
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