Ventilator Hyperinflation and Hemodynamics (VHI-HD)

Hemodynamic Repercussions of Ventilator Hyperinflation Using Volume-controlled Ventilation: a Randomized Controlled Trial

Ventilator hyperinflation (VHI) has been shown to be effective in improving respiratory mechanics, secretion removal, and gas exchange in mechanically ventilated patients; however, the literature is scarce concerning its safety and adverse effects. Thus, the aim of this study is to compare the hemodynamic repercussions of VHI in volume-controlled mode. In a randomized, controlled and crossover design, 24 mechanically ventilated patients will undergo 2 modes of ventilator hyperinflation (with and without an inspiratory pause) and a control intervention. Cardiac output, cardiac index, mean arterial pressure, pulmonary vascular resistance, systolic volume and other hemodynamic variables will be recorded 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, the literature is scarce concerning its safety and adverse effects. Thus, the aim of this study is to compare the hemodynamic repercussions of VHI in volume-controlled mode. Methods: in a randomized, controlled and crossover design, 24 mechanically ventilated patients will undergo 2 modes of ventilator hyperinflation (with and without an inspiratory pause of 2 seconds) and a control intervention. For the VHI interventions, the inspiratory flow will be set at 20 Lpm, and tidal volume will be increased until a peak pressure of 40cmH2O is achieved. During the control intervention, the patients will remain in volume-control ventilation with an inspiratory flow = 60Lpm and tidal volume = 6mL/IBW. The interval between interventions (washout) will be of 10 minutes or more, according to the time needed to recover the cardiac index to baseline values (maximum difference of 10%). Cardiac output, cardiac index, mean arterial pressure, pulmonary vascular resistance, systolic volume and other hemodynamic variables will be recorded during the interventions by using impedance cardiography.

The subjects will be kept in Volume Control Continuous Mandatory Ventilation (VC-CMV) with an inspiratory flow = 60Lpm and tidal volume = 6mL/IBW. Positive end-expiratory pressure and the inspired oxygen fraction will not be modified.

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

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

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

Application of a ventilator hyperinflation intervention with Volume Control Continuous Mandatory Ventilation (VC-CMV) without an inspiratory pause.

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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