This meta-analysis was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidance [14, 15].
Registration and protocol
This meta-analysis was registered on PROSPERO(CRD42022325145)
P-patient: adult patients were under mechanical ventilation through endotracheal intubation for ≥ 48 hours. I-index test: ΔScvO2 was measured in all included patients. C-complement: an SBT was given to all included patients who were deemed ready to be liberated from mechanical ventilation. O-outcome: the efficacy of ΔScvO2 for predicting extubation failure was estimated.
Relevant studies up to May 2022 were searched in the PubMed, Embase via OVID, and Cochrane Library databases with the following terms and their combinations: “central venous oxygen saturation or ScvO2” and “reintubation or wean or extubation.” All scanned abstracts, studies, and citations were reviewed. Moreover, references of the retrieved manuscripts were also manually cross-searched for further relevant publications.
The inclusion criteria were as follows: (1) studies on adult patients were under mechanical ventilation through endotracheal intubation for ≥ 48 hours;(2) a SBT was completed before extubation; (3)studies with SBT-induced decrease in ScvO2 as the index test; (4) studies published with full-text in any language; (5) studies providing sufficient data for constructing 2-by-2 tables, including true positive (TP), false positive (FP), true negative (TN), and false negative (FN). The exclusion criteria were as follows: (1) studies that used the same population or overlapping database;(2) reviews, case reports, editorials, letters, and conference abstracts; (3) articles with no available data for patients with ScvO2 and (4) articles without a definition of extubation failure.
Data extraction and quality assessment
All the available data were extracted from each study by two investigators independently according to the aforementioned inclusion criteria, and any differences were resolved by discussion with a third investigator. The following data were collected from each study: (1) basic characteristics of studies, including first author name, publication year, country where the research was performed, selected patients, gender, mean age, number of patients, study design, method and time of SBT, index test device for the ScvO2, definition of extubation failure; (2) diagnostic performance, including cutoff value, sensitivity, specificity, area under the receiver operator characteristic curve (AUROC), TP, FP, FN, and TN. If numbers of TP, FP, FN, and TN were unavailable, we communicated with the corresponding author to obtain these data.The quality of included studies was scored independently by two reviewers using the revised Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) criteria . The quality of studies was assessed using RevMan 5.4.
All analyses were performed using the Stata 16.0 software (Stata Corp., College Station, TX, USA). The bivariate meta-analysis model was employed to summarize sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio (DOR) [17, 18]. The sensitivity and specificity of each included study were used to plot the summary receiver operator characteristic (SROC) curve and calculate the area under the SROC curve (AUC). Diagnostic power was good, moderate, and poor if the AUC was more than 0.8, between 0.7 and 0.8, and less than 0.7, respectively. As publication bias is a concern for meta-analyses, the Deeks’ funnel plot asymmetry test was used, with P <0.10 indicating statistical significance .
Spearman’s correlation coefficient between the logit of sensitivity and logit of 1-specificity was calculated to determine any threshold effect; A strong positive correlation would suggest threshold effect. The between-study heterogeneity was evaluated using Q test and I2 statistics. A P value less than 0.10 for the Q test or I2 value ≥ 50% indicated substantial heterogeneity. A fixed effects model was used if no heterogeneity was observed. A random effects model was selected if significant heterogeneity was observed.