Study: NCT01742715

Intervention type: OTHER
Group type: EXPERIMENTAL
Intervention: PEEP by Best oxygenation
Description: Set PEEP at 25 cmH2O with fixed driving pressure that will result in delivery of a fixed Tidal Volume (TV) of 6ml/kg (IBW). FiO2 is set to 60%.~Then decrease PEEP in steps of 4 cmH2O every 10 min until PEEP of 5 cm H2O is reached. In each step static compliance of respiratory system and lung compliance will be measured along with ABGs, and hemodynamic parameters such as cardiac output and mixed venous O2 saturation. Best or optimal PEEP will be defined as the PEEP below which PaO2 /FIO2 falls by at least 20%. If at least 20% PaO2 /FIO2 decrement is not obtained, then PEEP that will result in the highest PaO2 will be selected.

Intervention type: OTHER
Group type: EXPERIMENTAL
Intervention: PEEP by Best oxygenation
Description: Set PEEP at 25 cmH2O with fixed driving pressure that will result in delivery of a fixed Tidal Volume (TV) of 6ml/kg (IBW). FiO2 is set to 60%.~Then decrease PEEP in steps of 4 cmH2O every 10 min until PEEP of 5 cm H2O is reached. In each step static compliance of respiratory system and lung compliance will be measured along with ABGs, and hemodynamic parameters such as cardiac output and mixed venous O2 saturation. Best or optimal PEEP will be defined as the PEEP below which PaO2 /FIO2 falls by at least 20%. If at least 20% PaO2 /FIO2 decrement is not obtained, then PEEP that will result in the highest PaO2 will be selected.

Intervention type: OTHER
Group type: EXPERIMENTAL
Intervention: PEEP by Best oxygenation
Description: Set PEEP at 25 cmH2O with fixed driving pressure that will result in delivery of a fixed Tidal Volume (TV) of 6ml/kg (IBW). FiO2 is set to 60%.~Then decrease PEEP in steps of 4 cmH2O every 10 min until PEEP of 5 cm H2O is reached. In each step static compliance of respiratory system and lung compliance will be measured along with ABGs, and hemodynamic parameters such as cardiac output and mixed venous O2 saturation. Best or optimal PEEP will be defined as the PEEP below which PaO2 /FIO2 falls by at least 20%. If at least 20% PaO2 /FIO2 decrement is not obtained, then PEEP that will result in the highest PaO2 will be selected.

Intervention type: OTHER
Group type: EXPERIMENTAL
Intervention: PEEP by Best Compliance
Description: In this group assessment begins with measuring intrinsic PEEP by an expiratory hold. Thereafter, plateau pressures will be recorded after a 0.5-sec inspiratory pause.~Applied PEEP will be increased by steps of 4 cm H2O, after each incremental step the patient will be observed for 10 minutes to allow for lung unit recruitment and equilibration. Plateau pressure will be measured after each incremental step of PEEP. Applied PEEP will be increased sequentially by 4 cm H2O increments until peak inspiratory pressure of 50 cm H2O, or plateau pressure of 40 cm H2O reached, or hypotension or decrease of 20% in cardiac output is observed.

Intervention type: OTHER
Group type: EXPERIMENTAL
Intervention: PEEP by Best Compliance
Description: In this group assessment begins with measuring intrinsic PEEP by an expiratory hold. Thereafter, plateau pressures will be recorded after a 0.5-sec inspiratory pause.~Applied PEEP will be increased by steps of 4 cm H2O, after each incremental step the patient will be observed for 10 minutes to allow for lung unit recruitment and equilibration. Plateau pressure will be measured after each incremental step of PEEP. Applied PEEP will be increased sequentially by 4 cm H2O increments until peak inspiratory pressure of 50 cm H2O, or plateau pressure of 40 cm H2O reached, or hypotension or decrease of 20% in cardiac output is observed.

Intervention type: OTHER
Group type: EXPERIMENTAL
Intervention: PEEP by Best Compliance
Description: In this group assessment begins with measuring intrinsic PEEP by an expiratory hold. Thereafter, plateau pressures will be recorded after a 0.5-sec inspiratory pause.~Applied PEEP will be increased by steps of 4 cm H2O, after each incremental step the patient will be observed for 10 minutes to allow for lung unit recruitment and equilibration. Plateau pressure will be measured after each incremental step of PEEP. Applied PEEP will be increased sequentially by 4 cm H2O increments until peak inspiratory pressure of 50 cm H2O, or plateau pressure of 40 cm H2O reached, or hypotension or decrease of 20% in cardiac output is observed.

Intervention type: OTHER
Group type: EXPERIMENTAL
Intervention: PEEP by Esophageal pressure
Description: Upon patient recruitment Esophageal balloon will be inserted and esophageal / pleural pressure will be measured. Thereafter, Inspiratory pressures and PEEP will be adjusted according to well established criteria. Inspiratory pressure and PEEP will be adjusted to achieve the best lung compliance possible while not exceeding transpulmonary end Inspiratory pressure of 25 to 30 cm H2O, and at the same time maintaining a positive transpulmonary end expiratory pressure of not more than 5 cm H2O.

Intervention type: OTHER
Group type: EXPERIMENTAL
Intervention: PEEP by Esophageal pressure
Description: Upon patient recruitment Esophageal balloon will be inserted and esophageal / pleural pressure will be measured. Thereafter, Inspiratory pressures and PEEP will be adjusted according to well established criteria. Inspiratory pressure and PEEP will be adjusted to achieve the best lung compliance possible while not exceeding transpulmonary end Inspiratory pressure of 25 to 30 cm H2O, and at the same time maintaining a positive transpulmonary end expiratory pressure of not more than 5 cm H2O.

Intervention type: OTHER
Group type: EXPERIMENTAL
Intervention: PEEP by Esophageal pressure
Description: Upon patient recruitment Esophageal balloon will be inserted and esophageal / pleural pressure will be measured. Thereafter, Inspiratory pressures and PEEP will be adjusted according to well established criteria. Inspiratory pressure and PEEP will be adjusted to achieve the best lung compliance possible while not exceeding transpulmonary end Inspiratory pressure of 25 to 30 cm H2O, and at the same time maintaining a positive transpulmonary end expiratory pressure of not more than 5 cm H2O.