Effect of Variable Volume Ventilation on Lung Compliance

Randomized controlled trial comparing low inspiratory and expiratory flow during variable volume ventilation with a constant volume decelerating flow (pressure controlled volume guarantee) ventilation.

Randomized controlled trial comparing low inspiratory and expiratory flow during variable volume ventilation (VVV) with a constant volume decelerating flow (PCV pressure controlled volume guarantee) ventilation. After anesthesia induction patients are VVV or PCV ventilated with a positive end expiratory pressure (PEEP) of 10 cm H2O. Average tidal volume is set at 6 ml/kg and end tidal CO2 is kept between 30 and 50 mmHg in both groups by adapting breaths per minute between 10 and 16. I/E ratio is set at 1/1 in VVV and at the standard ½ in PCV. Dynamic lung compliance is measured before and during pneumoperitoneum. If dynamic lung compliance is less than 40 or decreases below 40 a first lung recruitment (10 sec of 30 up to 40 cmH2O) is given till dyn compliance rises above 40. Dynamic lung compliance is further monitored and when value decreases again below 40, a new lung recruitment (LRM) is given and the PEEP is increased to 15 cm H2O after the second LRM. All patients get an opioid free general anesthesia with anti inflammatory agents and deep NMB with full reversal at end of surgery. The moment and number of LRM performed after induction of anesthesia with the averaged reached lung compliance is used to compare both ventilation methods. The oxygen saturation without oxygen at arrival of PACU and the need for oxygen when saturation drops below 95 % are compared between both groups.

the intervention is using a ventilation mode with variable tidal volume. The average tidal volume is 6 ml/kg and respiratory rate adapted to reach an end tidalCO2 concentration between 30 and 50 mmHg. Lung recruitment is given when dynamic lung compliance drops below 40. No drug is given. No other treatment or intervention is given.

the intervention is using ventilation mode with constant pressure and constant tidal volume. The tidal volume is 6 ml/kg and respiratory rate is adapted to reach end tidal CO2 concentrations between 30 and 50 mmHg. Lung recruitment is given when dynamic lung compliance drops below 40. No drug is given. No other treatment or intervention is given.

ventilation mode with variable tidal volume is chosen. the average tidal volume is 6 ml/kg and respiratory rate adapted to reach end tidal con between 30 and 50 mmHg

ventilation mode with constant tidal volume is chosen. the tidal volume is 6 ml/kg and respiratory rate adapted to reach end tidal con between 30 and 50 mmHg

Measuring dynamic lung compliance during mechanical ventilation. When it drops below 40 a lung recruitment is done with increase of PEEP to maximum 15 cmH2O.

during mechanical ventilation under general anesthesia between 1 and 3 hours. No outcome measurements are measured after 3 hours.

oxygen saturation on arrival of PACU without giving oxygen I measured and compared between both groups

during stay in PACU being between 1 and 4 hours post operative of the same day. No outcome measurements are measured after 4 hours.

Inclusion Criteria: laparoscopic bariatric surgery requiring mechanical ventilation Exclusion Criteria: lung disease requiring oxygen before anesthesia emergence procedure spontaneous or assisted ventilation