Evaluation of the Potential for Lung Recruitment with the Recruitment-to-Inflation Ratio during General Anesthesia
Authors' conclusion
During general anesthesia, the R/I reflects potential for lung recruitment.
Study context
- Population
- Patients undergoing open abdominal surgery under GA, mechanically ventilated with positive end-expiratory pressure (PEEP) 12 cm H 2 O for 30 min then abruptly reduced to 2 cm H 2 O
- Participants
- 20 patients
- Comparison
- R/I >0.40 vs R/I ≤0.40
- R/I >0.40n = 10
- R/I ≤0.40n = 10reference
- Outcome
- Agreement of R/I with individual potential for lung recruitment (recruited volume by nitrogen dilution and electrical impedance tomography)
Methodological detailsdecremental PEEP trial, electrical impedance tomography
- Decremental PEEP trial
- Electrical impedance tomography
Main finding
As reported in the abstract
R/I and recruited volume
R/I
median = 0.41, range = 0 to 0.86
Correlation of R/I with recruited volume normalized to FRC by gas dilution
r = 0.48, slope = 0.27
0.03, 0.52
Correlation of R/I with recruited volume scaled to PEEP-induced inflation volume by tomography
r = 0.82, slope = 1.2
0.77, 1.64
Further findings
PEEP required to optimize regional mechanics and balance collapse and overdistension
P = 0.03
| Outcome | R/I ≤0.40 | R/I >0.40 | P value |
|---|---|---|---|
| Change in dead space with higher PEEPMedian, % | 3 (IQR 0–5) | −2 (IQR −5–1) | P = 0.013 |
| Change in collapse with higher PEEPMedian, % | −30 (IQR −20–-38) | −44 (IQR −31–-47) | P = 0.016 |
| Change in dynamic lung strain with higher PEEPMedian | −0.04 (IQR −0.05–-0.02) | −0.06 (IQR −0.09–-0.05) | P = 0.04 |
Original publication
Evaluation of the Potential for Lung Recruitment with the Recruitment-to-Inflation Ratio during General Anesthesia. Anesthesiology. Published 21 July 2025. doi:10.
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