Statistical analysis
Variables were expressed as mean +/- standard deviation or median [Interquartile range (IQR)] for continuous variables, according to their distribution (Shapiro Wilk test) and number (percentage) for categorical variables. Data were analysed with both subjective and objective approaches (13). Subjective approach consisted in a graphic display of blood gas evolution depending on age and/or time compression. The objective approach consisted in a comparison of references and SimulResp values using dependent tests as appropriate. Quantitative variables were expressed as median [interquartile range] or mean +/- standard deviation, according to the distribution of the variable. Comparison between quantitative variables were performed with Wilcoxon’s signed rank tests or paired T test as appropriate. The correlation between reference and simulated data was evaluated by the coefficient of determination (R2). Intraclass correlation coefficients (ICC) and 95% confidence intervals and F test results were calculated with the R statistical packages “irr” (14) based on a single or average measurement, agreement, two-way mixed effect model (15), as appropriate. Based on statistical inference and literature (14), we considered the values of ICC to be the determinant of the level of reliability. Values under 0.5 indicated poor reliability, values between 0.5 and 0.75 indicated moderate reliability, values between 0.75 and 0.9 indicated good reliability, and values greater than 0.90 indicated excellent reliability. The agreement between SimulResp and reference data were evaluated with the Bland & Altman analysis. Bias, limits of agreement and percentage of error were calculated with the R statistical package “BlandAltman” (16,17). A p value of 0.05 was considered statistically significant. Statistical analyses were performed using open access R software (3.5.1, 2018-07-02,http://cran.r-project.org/).