Optimizing PEEP: Driving Pressure vs. Recruitment-Inflation Ratio

Positive end-expiratory pressure (PEEP) titration is crucial for preserving lung mechanics and physiology in mechanically ventilated patients. End-expiratory lung volume (EELV) and compliance can be used for this purpose. Based on these parameters, the Recruitment/Inflation ratio (R/I) has been used to estimate lung recruitability. We aimed to investigate the relationship between driving pressure and the Recruitment/Inflation ratio at two consecutive PEEP levels for appropriate PEEP selection in patients receiving mechanical ventilation support. End-expiratory lung volume (EELV) was measured during a decremental PEEP trial (PEEP levels of 20,15,10 and 5 cmH2O). The PEEP level associated with the lowest driving pressure among the four tested PEEP levels was selected. Patients were then ventilated at this selected PEEP level for 24 h. Subsequently, using the collected data, the R/I ratio was calculated between consecutive PEEP levels. If the R/I ratio was equal or above a pre-defined cut-off value, the higher of the two consecutive PEEP levels was considered potentially recruiting. If the R/I ratio was below the cut-off value, the lower PEEP level was considered appropriate. Finally, the relationship between the PEEP level associated with the lower driving pressure (between two consecutive PEEP steps) and the PEEP level deemed appropriate based on the R/I ratio cut-off was examined. The highest value of the arterial partial pressure of oxygen to fraction of inspired oxygen ratio (PaO2/FiO2) was measured at the 20 cmH2O PEEP level. EELV was found to be higher in patients classified as high recruiters (Step C and Step A) (P = 0.033). The PaO2/FiO2 ratio was also higher in the high-recruiter Step C (P = 0.008). In our study, the relationship between driving pressure and the R/I ratio for appropriate PEEP selection has been determined. The agreement between PEEP selection guided by driving pressure and PEEP selection guided by the R/I ratio did not reach statistical significance in our study. Sufficient and robust evidence to support the standalone use of the R/I ratio in clinical practice has not yet been established. Further studies are needed for this purpose.