The influence of cycling-off criteria and pressure support slope on the respiratory and hemodynamic variables in intensive care unit patients
© BioMed Central Ltd. 2007
Published: 22 March 2007
Modern mechanical ventilators allow changes in the flow cycling-off criteria and the pressure slope during pressure support ventilation (PSV). Changes in the cycling-off flow criteria of PSV can modify the expiratory synchrony between the mechanical and neural inspiration termination. The influences of the slope changes on the respiratory parameters in ICU patients are still under investigation.
To compare the effects of two different flow cycling-off criteria and the effects of two different pressure slopes (150 ms or 300 ms) of PSV on the respiratory parameters of ICU mechanically ventilated patients.
We prospectively evaluated 20 intubated and mechanically ventilated adult ICU patients recovering from acute respiratory failure who could be comfortably ventilated on pressure support mode (PSV) with pressure support of 15 cmH2O, PEEP of 5 cmH2O and FIO2 of 40%. Patients were ventilated on PSV, with 25% and 40% of peak expiratory flow cycling criteria, and were submitted to 150 ms and 300 ms pressure slope delay. We evaluated the respiratory rate, expiratory tidal volume, minute ventilation, VCO2, VTCO2, ETCO2, mean arterial pressure (MAP), heart rate and SpO2.
Tidal volume (ml)
Minute volume (l/min)
Changes in cycling-off criteria from 25% to 40% of the peak flow and on the pressure slope from 150 ms to 300 ms do not affect other respiratory and hemodynamic variables in mechanically ventilated patients.