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/).