Statistical Analysis of Hemodynamic Changes

The data were analyzed with the software GraphPad Prism 6.0a for Mac OS X (GraphPad Software, La Jolla, CA, USA). Comparison between two groups was performed with student t test. Multiple groups comparison was done by analysis of variance (ANOVA). Tukey’s test was used as the post-hoc test to compare the difference between two groups. The statistical significance was considered when the P value is less than 0.05.
GraphPad Prism 6.0a, which uses analysis of covariance (ANCOVA) to compare the slopes of the linear regression lines, was used to analyze the data from the blood flow test. It has been revealed that the magnitude of the hemodynamics change is related to the initial resting values (Millar et al. 2007 (link); Baross et al. 2012 (link)). Hence, ANCOVA was implemented to determine whether there was a significant difference in the contracting TA blood flow of three groups compared to the resting measures, using the resting values as the covariate. Then post-hoc analysis (Tukey’s test) was used to further determine significant difference between two groups. Linearity of data was confirmed by passing residual normality test (Kolmogorov-Smirnov test) and random distribution of residuals in residual plots (Additional file 3: Figure S3). The statistical significance was considered when the P value is less than 0.05.