Ventilator Hyperinflation With Increase of Inspiratory Time

Ventilator Hyperinflation With Increase of Inspiratory Time on Respiratory Mechanics: A Randomized Crossover Trial

The investigators hypothesis is that the adjustment of the inspiratory time may optimize the distribution of ventilation and increase tidal volume, producing potential therapeutic effects on the displacement of secretions and respiratory mechanics. The objective of this study was To evaluate the effects of hyperinflation with the ventilator associated with increased inspiratory time on respiratory mechanics.

A randomized crossover clinical trial was conducted with 38 mechanically ventilated patients with pulmonary infection. The order of hyperinflation or control (without changes in parameters) was randomized. Hyperinflation was performed for 5 minutes in the controlled pressure ventilation mode, with progressive increases of 5cmH2O until reaching a maximum pressure of 35cmH2O, maintaining PEEP. After reaching 35cmH2O, the inspiratory time and respiratory rate were adjusted so that the inspiratory and expiratory flows reached the baseline, respectively. Static compliance (Cest, sr), total resistance (Rsr) and airway resistance (Rva), slow pressure drop (ΔP2) and peak expiratory flow (PEF) were assessed before (PRÉ), immediately after the maneuver (POSSimed) and after aspiration (POSPasp). Two-way ANOVA was used for repeated measurements with Tukey post-test, considering a significant p <0.05.

Inclusion Criteria:

• Patients under mechanical ventilation for more than 48h
• Mucus hypersecretion (defined as the need for suctioning < 2-h intervals)

Exclusion Criteria:

• Severe bronchospasm,
• Positive end expiratory pressure > 10cmH2O,
• PaO2-FiO2 relationship < 150,
• Mean arterial pressure < 60mmHg,
• Pleural effusion or pneumothorax undrained,
• Bronchopleural or tracheoesophageal fistula,
• Decompensated congestive heart failure.