Rate of recruitment

In 2008 a new ventilation strategy termed variable Pressure Support ventilation (PSV) was introduced, which is able to increase the variability of the respiratory pattern independent from the inspiratory effort. In experimental lung injury, variable PSV was found to improve gas exchange and decrease the inspiratory effort, while reducing alveolar edema and inflammatory infiltration compared to conventional(non-variable) PSV. Importantly, variable PSV reduced peak airway pressure and respiratory system elastance in a variability dependent manner.In addition, preliminary observations suggest that variable PSV can reduce the work of breathing and improve patient comfort, but it is not known whether this new ventilatory strategy is able to speed the weaning from mechanical ventilation.

Since variable PSV can reduce the mean pressure support, it may lead to a faster reduction of pressure support and, therefore, a shorter weaning period than conventional PSV.

The hypothesis of this study is that variable pressure support ventilation reduces the duration of mechanical ventilation to non-variable (conventional) pressure support ventilation.

Inclusion Criteria:

• Age ≥ 18 years
• Duration of controlled mechanical ventilation ≥ 24h
• Availability of a Infinity V500 ventilator (ready to use)
• Informed consent according to local regulations
• Temperature ≤ 39 °C
• Hemoglobin ≥ 6 g/dl
• PaO2/FIO2 ≥ 150 mmHg with positive end-expiratory pressure (PEEP) ≤16 cmH2O
• Ability to breath spontaneously

Exclusion Criteria:

• Participation in another interventional trial within the last four weeks before enrollment in this trial
• Peripheral neurological disease associated with impairment of the respiratory pump
• Muscular disease associated with impairment of the respiratory pump
• Instable thorax with paradoxical chest wall movement
• Planned surgery under general anesthesia within 72 hours
• Difficult airway/intubation
• Existing tracheotomy at ICU admission
• Expected survival < 72 hours
• Home mechanical ventilation or on chronic oxygen therapy
• Suspected pregnancy