An evaluation of end expiratory lung volume and pulmonary mechanics with different PEEP levels in ARDS patients

Objective: The treatment of acute respiratory distress syndrome (ARDS) is highly complex, and its mortality rate remains significant. Positive end-expiratory pressure (PEEP) titration plays a crucial role in mechanical ventilation; however, the optimal approach for PEEP titration has yet to be established. This study evaluated the volume gain at different PEEP levels along the pressure-volume curve, changes in end-expiratory lung volume (EELV) measured via the modified multiple nitrogen wash-out/wash-in technique, and respiratory compliance. Materials and Methods: Following approval from the ethics committee, 14 patients with ARDS receiving invasive mechanical ventilation in intensive care units were included in the study. According to the Berlin Criteria, there were 2 patients with mild ARDS, 7 with moderate ARDS, and 5 with severe ARDS. The repeated nitrogen wash-out/wash-in technique assessed functional residual capacity (FRC) and EELV at decreasing PEEP levels (±5 cm H2O) were determined. Gain and compliance values were calculated based on the dynamic pressure-volume curves generated. Arterial blood gas analysis was conducted to measure oxygenation at each PEEP level. Results: The highest compliance, gain, and EELV values, as well as the lowest driving pressure and strain values, were observed at a PEEP level of 10 cm H2O. Conversely, the highest PaO2 values, representing oxygenation indicators, were recorded at a PEEP level of 15 cm H2O. Notably, the gain remained largely unaffected by changes in compliance, elastance, driving pressure, and static strain; it was not affected by lung distension. Conclusions: In PEEP titration, alveolar distension was not detected by EELV or gain parameters. Sufficient evidence could not be obtained solely in clinical practice.