[Impact of recruitment-to-inflation ratio and elastic power on the efficacy and outcomes of prone positioning in patients with moderate-to-severe acute respiratory distress syndrome].

<b>Objective:</b> To analyze the factors influencing the time-dependent effect and prognosis of recruitment-to-inflation ratio (R/I) and elastic power in the prone position in patients with moderate-to-severe acute respiratory distress syndrome (ARDS). <b>Methods:</b> A prospective, observational cohort study was conducted. A total of 113 patients with moderate-to-severe ARDS were enrolled from December 2022 to October 2024 in the intensive care unit of the First Hospital of Jinzhou Medical University. Patients were divided into survival and death groups based on their 28-day prognosis. Clinical indicators such as R/I, elastic power, mechanical power (MP), oxygenation index (OI), optimal positive end-expiratory pressure (PEEP), respiratory rate (RR), and tidal volume (VT) after 2 hours and 16 hours of prone ventilation treatment between the two groups of patients were compared. Logistic regression was used to analyze the risk factors for 28-day mortality in patients with moderate to severe ARDS treated with prone ventilation. Spearman's correlation method was used to analyze the correlation between R/I and elastic power at various time points during prone ventilation treatment. Receiver operating characteristic (ROC) curve analysis was then used to evaluate the predictive value of R/I_2h and elastic power_2h for the 28-day mortality rate in patients with moderate-to-severe ARDS who were treated with prone ventilation. <b>Results:</b> Compared to the non-survivors, the survival group demonstrated significantly higher R/I, OI, and tidal volume after 2 and 16 hours of prone positioning (all <i>P<</i>0.05). Conversely, elastic power, mechanical power, optimal PEEP, and respiratory rate were significantly lower in survivors (all <i>P</i><0.05). Logistic regression analysis revealed that R/I _2h, elastic power _2h, optimal PEEP _2h, and respiratory rate _2h were identified as independent risk factors for predicting 28-day mortality in patients with moderate-to-severe ARDS undergoing prone positioning ventilation (all <i>P</i><0.05). Spearman correlation analysis demonstrated that R/I at 2h and 16h was significantly correlated with elastic power (R values:-0.511 and -0.557, all <i>P<</i>0.05). ROC curve analysis showed that the area under the curve (AUC) for R/I_2h was 0.817, whereas the AUC for elastic power_2h was 0.703. The combined AUC for R/I_2h and elastic power_2h was 0.864 (all <i>P</i><0.001). <b>Conclusions:</b> Analysis of the impact of R/I and elastic power on the prognosis of patients with moderate-to-severe ARDS undergoing prone ventilation can be used to assess the lung recruitability within a safe pressure range, as well as the time-dependent response of various factors during the process. This analysis has good predictive value for the 28-day prognosis.