Efficacy of Trans Alveolar Pressure Measurement as an Index for Lung Recruitment in Post Cardiac Surgery Hypoxic Patients.

After one hour from the patient's ICU admission and after stabilization of the patient's haemodynamics, alveolar recruitment will be done for hypoxic patients with hypoxic index less than 250.

The recruitment will be started in the adaptive ventilation mode (AVM mode) using modified stepwise staircase recruitment maneuver in which every 2 minutes positive end-expiratory pressure (PEEP) is increased in increments of 2 cmH2O and the driving pressure will be regulated by AVM mode.

The increase in PEEP will be guided by improvement of dynamic compliance, oxygen saturation and transalveolar pressure (PTA) till near overdistention.

Overdistension will be detected if there are decrease in the mean arterial pressure 25% from the base line value reported after stabilization of the patient's haemodynamics, or decreased oxygen saturation or sudden decrease in dynamic compliance, or inspiratory PTA more than15 cm H2O.

Then PEEP is decreased 2 cm H2O every 3 minutes till a decrease expiratory PTA less than 1 cm H2O, or a decrease in dynamic compliance or a decrease in oxygen saturation ≥ 1% from maximum oxygen saturation is observed (the derecruitment point) then return to a PEEP level 2 cm H2O above the derecruitment point (the optimal PEEP).