Ventilator Hyperinflation and Hemodynamics

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.

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