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The following is a summary of “Optimum electrical impedance tomography-based PEEP and recruitment-to-inflation ratio in patients with severe ARDS on venovenous ECMO,” published in the May 2025 issue of Critical Care by Coppens et al. 

Researchers conducted a retrospective pulmonology study to compare the concordance of the recruitment-to-inflation (R/I) ratio and Electrical Impedance Tomography (EIT) in determining optimal positive end-expiratory pressure (PEEP) settings in patients with severe acute respiratory distress syndrome (ARDS) on extracorporeal membrane oxygenation (ECMO) and ventilated with very low tidal volumes. 

They performed a low-flow insufflation to detect and measure airway opening pressure (AOP). The R/I ratio was then calculated between PEEP levels of 15 and 5 cmH₂O. Following this, a decremental PEEP trial from 20 to 6 cmH₂O in 2 cmH₂O steps was conducted and monitored using EIT. The optimal EIT-based PEEP was identified at the intersection of the collapse and overdistension curves.  

The results showed that among 54 patients on ECMO (tidal volume: 4.8 [3.0–6.0] mL/kg), 13 (24%) had an AOP of 11 (8–14) cmH₂O. The median R/I ratio was 0.43 (0.28–0.61). Tertile analysis of the R/I ratio (≤ 0.34; 0.34–0.54; > 0.54) corresponded to median optimal EIT-based PEEP of 8 [8–10], 10 [8–14], and 14 [12–16] cmH₂O, respectively. The R/I ratio showed a weak inverse correlation with lung overdistension (R² = 0.19) and a positive correlation with lung collapse (R² = 0.26) measured by EIT (P< 0.01).  

Investigators concluded that the R/I ratio was feasible during ultra-protective ventilation and could guide PEEP titration, with ratios above 0.34 indicating a need for further individualized optimization using EIT, while ratios at or below 0.34 suggested moderate PEEP levels of 8–10 cmH₂O were sufficient. 

Source: ccforum.biomedcentral.com/articles/10.1186/s13054-025-05437-0