A 16-electrode silicon belt (EIT evaluation kit 2, Dräger, Lübeck, Germany) was placed around the patient’s thoracic cage between the 6th and 7th intercostal spaces [16 (link)]. Patients were ventilated with pressure-controlled ventilation (PCV) (Engström Carestation, GE Healthcare, Madison, WI, USA) and, throughout the entire study period, the inspiratory pressure above PEEP, the Inspiration/expiration (I/E) ratio, frequency and inspired oxygen fraction (FiO2) remained unchanged.
In this study we performed a recruitment maneuver in which mechanical ventilation was continued with a pressure amplitude of 20 cm H2O while PEEP was rapidly increased from 5 to 20 cm H2O in incremental steps of 5 cm H2O: thus, a peak pressure of 40 cm H2O for a 40-s period, as long as blood pressure remained stable. Thereafter, PEEP was decreased to 15 cm H2O and the pressure amplitude was decreased from 20 to 10 cm H2O. A PEEP level of 15 cm H2O was applied for 15 minutes to achieve a steady state. Thereafter, a decremental PEEP trial was performed from 15 to 0 cm H2O PEEP in steps of 5 cm H2O. Each PEEP level was applied for 10 to 20 minutes (depending on hemodynamic stability and blood gas analyses). At the end of each PEEP step, EIT, PaO2/FiO2 ratio and dynamic compliance (tidal volume divided by pressure above PEEP) were calculated.
In this study we performed a recruitment maneuver in which mechanical ventilation was continued with a pressure amplitude of 20 cm H2O while PEEP was rapidly increased from 5 to 20 cm H2O in incremental steps of 5 cm H2O: thus, a peak pressure of 40 cm H2O for a 40-s period, as long as blood pressure remained stable. Thereafter, PEEP was decreased to 15 cm H2O and the pressure amplitude was decreased from 20 to 10 cm H2O. A PEEP level of 15 cm H2O was applied for 15 minutes to achieve a steady state. Thereafter, a decremental PEEP trial was performed from 15 to 0 cm H2O PEEP in steps of 5 cm H2O. Each PEEP level was applied for 10 to 20 minutes (depending on hemodynamic stability and blood gas analyses). At the end of each PEEP step, EIT, PaO2/FiO2 ratio and dynamic compliance (tidal volume divided by pressure above PEEP) were calculated.
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