Evaluation of end-expiratory lung volume and pulmonary mechanics with the different "PEEP" levels in mechanical ventilation of ARDS patients

The management of acute respiratory distress syndrome (ARDS) is quite complex and its mortality is high. Ventilation support is required to support gas consumption in the lungs and reduce the work of breathing. In mechanical ventilation, positive end-expiratory pressure (PEEP) titration is of great importance. However, the most appropriate approach for PEEP titration has not been clearly determined. Currently, the emphasis is on individualized PEEP implementation. In our study is aimed to evaluate the volume gain at different PEEP levels over the pressure-volume curve, the change in end-expiratory lung volume (EELV) measured by the modified multiple nitrogen washout/washin technique, and the compliance with respiratory mechanics. After the approval of the Ethics Committee, 14 adult ARDS patients hospitalized in intensive care units and undergoing invasive mechanical ventilation were included in the study. According to the Berlin Criteria; There were 2 mild, 7 moderate, 5 severe ARDS patients. Functional residual capacity (FRC) and EELV with decreased PEEP titration estimate (5 cmH2O) were measured by multiple nitrogen washout/washin technique. Gain and compliance were measured over the dynamic pressure-volume curves created by the intracheal pressure sensor. Oxygenation was assessed with arterial blood gas at each PEEP level. The highest compliance, gain, EELV values and lowest driving pressure values were reached at 10 cmH2O PEEP level. The highest values of PaO2, which are oxygenation indicators, were measured at the PEEP level of 15 cmH2O. It was seen that the gain did not materially change due to compliance, elastanes, driving pressure, and static strain and was not effected by lung distension. In conclusion; in PEEP titration, alveolar distension cannot be detected by EELV or gain parameters. Sufficient and strong evidence could not be obtained for its use alone in clinical practice. More study is needed for this. Keywords: Functional residual capacity, gain, PEEP, EELV, pulmonary mechanics