Authors: Rosà, Tommaso et al.
Anesthesiology, September 15, 2025. DOI: 10.1097/ALN.0000000000005677
This study evaluated the recruitment-to-inflation ratio (R/I) as a bedside method to estimate lung recruitability during general anesthesia. Because patients vary in how their lungs respond to positive end-expiratory pressure (PEEP), an individualized approach to setting PEEP could prevent both atelectasis and overdistension. The R/I, calculated from ventilator data during a brief PEEP-release maneuver, offers a simple way to assess recruitment potential without additional equipment.
Twenty adults undergoing open abdominal surgery were ventilated with a PEEP of 12 cm H₂O for 30 minutes before it was rapidly reduced to 2 cm H₂O. Researchers recorded gas exchange, lung mechanics, and electrical impedance tomography data, along with end-expiratory lung volume and functional residual capacity, to correlate these findings with the R/I.
The median R/I was 0.41 (range 0–0.86) and correlated well with independently measured recruited lung volume (r = 0.82). Patients with higher R/I values (>0.40) demonstrated greater potential for recruitment and benefited from higher PEEP levels that reduced dead space, minimized collapse, and lowered dynamic lung strain. Those with lower R/I values (≤0.40) derived less physiologic benefit from higher PEEP, indicating limited recruitability.
The results confirm that R/I reliably reflects individual lung recruitment capacity and can be used to optimize PEEP selection during anesthesia. This could help clinicians apply safer, more tailored ventilatory strategies that minimize lung injury and improve gas exchange.
What You Should Know:
The recruitment-to-inflation ratio provides a simple, real-time assessment of lung recruitability during anesthesia. Patients with R/I values above 0.4 may benefit from higher PEEP to prevent collapse, while those below 0.4 are better managed with lower PEEP to avoid overdistension.
Thank you to Anesthesiology for publishing this important study advancing individualized ventilation strategies in surgical anesthesia.