Authors: Rosà, Tommaso et al.
Anesthesiology, September 15, 2025. DOI: 10.1097/ALN.0000000000005677
This investigation assessed the recruitment-to-inflation ratio (R/I) as a practical, noninvasive tool to evaluate lung recruitability during general anesthesia. Optimizing PEEP settings to prevent both atelectasis and overdistension is central to lung-protective ventilation, but individual variation in recruitability complicates this process. The study aimed to determine whether R/I could accurately estimate a patient’s potential for lung recruitment using only standard ventilator data.
Twenty adult patients undergoing open abdominal surgery were ventilated with 12 cm H₂O of PEEP, which was then abruptly dropped to 2 cm H₂O to perform a single-breath PEEP-release maneuver. Researchers measured R/I values alongside several physiologic and mechanical variables, including gas exchange, lung volume, and regional strain assessed by electrical impedance tomography.
The results showed that R/I strongly correlated with independently measured recruited lung volume and functional residual capacity. Patients with R/I > 0.40 demonstrated greater recruitability, requiring higher PEEP levels (median 10 vs. 8 cm H₂O) to achieve optimal mechanics, reduce collapse, lower dead space, and decrease dynamic strain. Conversely, patients with R/I ≤ 0.40 gained little physiologic benefit from additional PEEP, suggesting lower recruitment potential.
Overall, the R/I proved to be a reliable, simple bedside metric to tailor ventilation strategies during general anesthesia. By identifying which patients benefit most from higher PEEP, anesthesiologists can reduce the risk of ventilator-induced lung injury and optimize oxygenation in real time.
What You Should Know:
The R/I ratio can individualize PEEP settings during general anesthesia without extra equipment. A value above 0.4 indicates that higher PEEP likely improves alveolar recruitment and reduces strain, while lower values suggest minimal benefit and possible overdistension with excess PEEP.
Thank you to Anesthesiology for publishing this important advancement in intraoperative respiratory monitoring and personalized ventilatory management.