Accuracy and precision of transcutaneous carbon dioxide monitoring: a systematic review and meta-analysis.

BACKGROUND: Transcutaneous carbon dioxide (TcCO2) monitoring is a non-invasive alternative to arterial blood sampling. The aim of this review was to determine the accuracy and precision of TcCO2 measurements. METHODS: Medline and EMBASE (2000-2016) were searched for studies that reported on a measurement of PaCO2 that coincided with a measurement of TcCO2. Study selection and quality assessment (using the revised Quality Assessment of Diagnostic Accuracy Studies tool (QUADAS-2)) were performed independently. The Grading Quality of Evidence and Strength of Recommendation approach was used to summarise the strength of the body of evidence. Pooled estimates of the mean bias between TcCO2 and PaCO2 and limits of agreement with outer 95% CIs (termed population limits of agreement) were calculated. RESULTS: The mean bias was -0.1 mm Hg and the population limits of agreement were -15 to 15 mm Hg for 7021 paired measurements taken from 2817 participants in 73 studies, which was outside of the clinically acceptable range (7.5 mm Hg). The lowest PaCO2 reported in the studies was 18 mm Hg and the highest was 103 mm Hg. The major sources of inconsistency were sensor location and temperature. The population limits of agreement were within the clinically acceptable range across 3974 paired measurements from 1786 participants in 44 studies that applied the sensor to the earlobe using the TOSCA and Sentec devices (-6 to 6 mm Hg). CONCLUSION: There are substantial differences between TcCO2 and PaCO2 depending on the context in which this technology is used. TcCO2 sensors should preferentially be applied to the earlobe and users should consider setting the temperature of the sensor higher than 42°C when monitoring at other sites. SYSTEMATIC REVIEW REGISTRATION NUMBER: PROSPERO; CRD42017057450.

High quality of evidence is uncommon in Cochrane systematic reviews in Anaesthesia, Critical Care and Emergency Medicine.

BACKGROUND: The association between the quality of evidence in systematic reviews and authors' conclusions regarding the effectiveness of interventions relevant to anaesthesia has not been examined. OBJECTIVE: The objectives of this study were: to determine the proportion of systematic reviews in which the authors made a conclusive statement about the effect of an intervention; to describe the quality of evidence derived from outcomes in reviews that used the Grades of Recommendation, Assessment, Development and Evaluation (GRADE) working group system for grading the quality of evidence; and to identify review characteristics associated with conclusiveness. DESIGN: Cross-sectional analysis of Cochrane systematic reviews from the Anaesthesia, Critical Care and Emergency Review Group was undertaken. DATA SOURCES: The Cochrane webpage was used to identify reviews for inclusion (http://.ace.cochrane.org/). ELIGIBILITY CRITERIA: New and updated versions of systematic reviews published up to 17 September 2015 were eligible. Protocols for systematic reviews were excluded. RESULTS: A total of 159 reviews were included. GRADE was used in 103 reviews (65%). Of these, high-level evidence for the primary outcome was identified in 11 reviews (10%). The main reasons that quality of evidence for the primary outcome was downgraded were risk of bias (n = 44; 43%) and imprecision (n = 36; 35%). Authors of 47% (n = 75) of the total number of reviews made conclusive statements about the effects of interventions. Independent predictors of conclusiveness in the subgroup of reviews with GRADE assessments were quality of evidence for the primary outcome (odds ratio 2.03; 95% confidence interval: [1.18 to 3.52] and an increasing number of studies included in reviews (OR 1.05; 95% CI: [1.01 to 1.09]). CONCLUSION: It was common for conclusive statements to be made about the effects of interventions despite evidence for the primary outcome being rated less than high quality. Improving methodological quality of trials would have the greatest impact on improving the quality of evidence.