Fig. 4

Scatterplots showing the relationships between hemodynamic or heart rate variability (HRV) parameters that have been found significant (p < 0.05) in the correlation analyses without Bonferroni’s correction. The dependent variables are either heat pain intensity (experimental pain) or the composite pain/analgesia score (CPAS) (see Methods’ chapter for details). The parameters tested are either the increase in heart rate as observed under Valsalva maneuver (VM) or the LF/HF ratio (HRV parameter, see Table 1 for interpretation) under deep breathing challenge (DB). The values shown for each relationship scatterplot are the Spearman’s correlation coefficient (ρ), the p value for the comparison of ρ to the null value (without Bonferroni’s correction), and the coefficient of determination R²