2.5. Outcome Measures
Pre- and post-treatment values of HRV were examined. HRV evaluation, based on processing R-R intervals, was divided into time- and frequency-domain linear analysis [The following time-domain parameters of HRV were considered: standard deviation of adjacent NN intervals (SDNN), the root mean square of successive R-R interval differences (RMSSD), the number of adjacent NN intervals differing by more than 50 milliseconds (NN50), and the percentage of successive R-R intervals differing by more than 50 ms (pNN50). RMSSD, NN50, and pNN50 are correlated with parasympathetic activation [The frequency-domain index of HRV analyzed in this study was the high frequency (HF) band, from 0.15 to 0.4 Hz. The HF band is indicative of parasympathetic activity and is called the respiratory band because it corresponds to the HR variations related to the respiratory cycle [