Background: High flow nasal cannula (HFNC) therapy is widely employed in acute hypoxemic respiratory failure (AHRF) patients. However, the techniques for predicting HFNC outcome remain scarce.Methods: PubMed, EMBASE, and Cochrane Library were searched until April 20, 2021. We included the studies that evaluated the potential predictive value of ROX (respiratory rate-oxygenation) index for HFNC outcome. This meta-analysis determined sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic score, diagnostic odds ratio (DOR), and pooled area under the summary receiver operating characteristic (SROC) curve.Results: We assessed nine studies with 1933 patients, of which 745 patients experienced HFNC failure. This meta-analysis found that sensitivity, specificity, PLR, NLR, diagnostic score, and DOR of ROX index in predicting HFNC failure were 0.67 (95% CI 0.57-0.76), 0.72 (95% CI 0.65-0.78), 2.4 (95% CI 2.0-2.8), 0.46 (95% CI 0.37-0.58), 1.65(95% CI 1.37-1.93), and 5.0 (95% CI 4.0-7.0), respectively. In addition, SROC was 0.75 (95% CI 0.71-0.79). Besides, our subgroup analyses revealed that ROX index had higher sensitivity and specificity for predicting HFNC failure in COVID-19 patients from non-European countries, while the acquisition time of 6 h after receiving HFNC had a lower sensitivity and specificity when compared to other times.Conclusions: This study demonstrated that ROX index could function as a novel potential marker to identify patients with a higher risk of HFNC failure. However, the prediction efficiency was moderate, and additional research is required to determine the optimal cut-off value and propel acquisition time of ROX index in the future.

Background Airway pressure release ventilation (APRV) has been described many years, however, it is still unclear whether APRV improves outcomes in critically ill patients admitted to Intensive Care Unit with acute respiratory distress syndrome (ARDS). Methods 3 databases were searched for randomized controlled trials (RCTs) until 8 August 2019. The relative risk (RR), mean difference (MD) and 95% confidence intervals (CI) were determined. Results A total of six randomized controlled trials (RCTs) were included with 360 ARDS patients. The Meta analysis showed that the mean arterial pressure (MAP) in APRV group is higher than traditional mechanical ventilation group [MD = 2.35, 95% CI=(1.05,3.64), P = 0.0004], and the airway peak pressure (Ppeak) is lower in APRV group with statistical difference [MD=-2.04,95% CI=(-3.33,-0.75), P = 0.002]. However, no significant beneficial effect on oxygen index (PaO2/FiO2) was shown between two groups (MD = 26.24, 95% CI=(-26.50,78.97), P = 0.33). Compared with conventional mechanical ventilation, APRV significantly improved 28-day mortality [RR = 0.66, 95% CI=(0.47,0.94), P = 0.02]. Conclusions For critically ill patients with ARDS, application of APRV is associated with the increase of MAP, the reduction of the airway Ppeak and 28-day mortality, while there is no sufficient evidence to support the APRV is superior to conventional mechanical ventilation in PaO2/FiO2.