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Background <p>The recruitment-to-inflation (R/I) ratio is a new bedside tool with potential to evaluate lung recruitability by positive end-expiratory pressure (PEEP) but was only validated using pressure–volume curves and the optimal threshold separating low and high recruiters by PEEP is not precisely known. The aim of the study is to evaluate the diagnostic performance of the R/I ratio using computed tomography (CT) as a gold standard in patients with acute respiratory distress syndrome (ARDS).</p> Methods <p>This study is a single-center prospective observational study performed on adults ARDS patients under invasive mechanical ventilation. The R/I ratio was measured with the ventilator, and low-dose CT scans were acquired at PEEP 15 and 5 cmH<sub>2</sub>O to compute alveolar recruitment. Patients were classified as high recruiters if the recruited lung by PEEP was greater than 5% of lung weight on CT.</p> Results <p>Fifty patients were included, and eight patients were secondarily excluded (7/50 [14%] for suspected air leaks, and 1/50 [2%] for airway opening pressure &gt; 15 cmH<sub>2</sub>O). Thirty-three patients [79%] were classified as low recruiters and 9 [21%] as high recruiters with CT.</p> <p>The median R/I ratio was not significantly higher in high recruiters (0.67 [IQR: 0.57–0.74]), than in low recruiters (0.42 [IQR: 0.24–0.64]), <i>p</i> = 0.07. There was no significant correlation between the R/I ratio and the weight of the recruited lung on CT (<i>R</i><sup>2</sup> = 0.065; <i>p</i> = 0.10). The AUC of the R/I ratio to identify high recruiters was 0.70 (CI<sub>95%</sub>: [0.52–0.89]), with an optimal threshold amounting to 0.57. Sensitivity and specificity at this threshold were 78% [CI<sub>95%</sub>:44%-100%] and 67% [CI<sub>95%</sub>: 52%-82%], respectively. The false positive and false negative rates were 11/33 [33%] and 2/9 [22%], respectively, and all false negative patients had focal ARDS. Misclassification was mainly related to overestimation of PEEP volume by the ventilators, that was confirmed by a bench study for two out of three ventilators used in the study.</p> Conclusions <p>In a population of ARDS patients with low recruitment potential, the R/I ratio had a poor diagnostic performance to predict lung recruitability, but R/I ratio values below 0.57 reliably identified ARDS patients with low recruitability, provided they did not present focal ARDS.</p>

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Diagnostic performance of the recruitment-to-inflation ratio to assess lung recruitability by PEEP in ARDS. a computed tomography study

  • 期刊论文

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  • 发表日期：

    2025年6月3日

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  • Jean-Christophe Richard,
  • Francois Dhelft,
  • Guillaume Deniel,
  • Emmanuel Roux,
  • Hodane Yonis,
  • Mehdi Mezidi,
  • Louis Chauvelot,
  • Maxime Gaillet,
  • Ines Noirot,
  • Eduardo Davila,
  • Rosalie Schoux,
  • Yorick Rodriguez,
  • Florent Baudin,
  • Ludmilla Penarrubia,
  • Loic Boussel,
  • Maciej Orkisz,
  • Laurent Bitker

摘要

Background

The recruitment-to-inflation (R/I) ratio is a new bedside tool with potential to evaluate lung recruitability by positive end-expiratory pressure (PEEP) but was only validated using pressure–volume curves and the optimal threshold separating low and high recruiters by PEEP is not precisely known. The aim of the study is to evaluate the diagnostic performance of the R/I ratio using computed tomography (CT) as a gold standard in patients with acute respiratory distress syndrome (ARDS).

Methods

This study is a single-center prospective observational study performed on adults ARDS patients under invasive mechanical ventilation. The R/I ratio was measured with the ventilator, and low-dose CT scans were acquired at PEEP 15 and 5 cmH2O to compute alveolar recruitment. Patients were classified as high recruiters if the recruited lung by PEEP was greater than 5% of lung weight on CT.

Results

Fifty patients were included, and eight patients were secondarily excluded (7/50 [14%] for suspected air leaks, and 1/50 [2%] for airway opening pressure > 15 cmH2O). Thirty-three patients [79%] were classified as low recruiters and 9 [21%] as high recruiters with CT.

The median R/I ratio was not significantly higher in high recruiters (0.67 [IQR: 0.57–0.74]), than in low recruiters (0.42 [IQR: 0.24–0.64]), p = 0.07. There was no significant correlation between the R/I ratio and the weight of the recruited lung on CT (R2 = 0.065; p = 0.10). The AUC of the R/I ratio to identify high recruiters was 0.70 (CI95%: [0.52–0.89]), with an optimal threshold amounting to 0.57. Sensitivity and specificity at this threshold were 78% [CI95%:44%-100%] and 67% [CI95%: 52%-82%], respectively. The false positive and false negative rates were 11/33 [33%] and 2/9 [22%], respectively, and all false negative patients had focal ARDS. Misclassification was mainly related to overestimation of PEEP volume by the ventilators, that was confirmed by a bench study for two out of three ventilators used in the study.

Conclusions

In a population of ARDS patients with low recruitment potential, the R/I ratio had a poor diagnostic performance to predict lung recruitability, but R/I ratio values below 0.57 reliably identified ARDS patients with low recruitability, provided they did not present focal ARDS.