. 2021 Mar;37(2):195–203. doi: 10.6515/ACS.202103_37(2).20200907A

Table 2. Changes in heart rate variability (HRV) parameters during the 3-month period of DGSB.

Variable	Baseline	1 month	3 month
SDNN (ms)	28.68 ± 13.70	26.83 ± 15.62	27.29 ± 16.00
pNN50 (%)	7.65 ± 15.22	5.22 ± 12.92	5.45 ± 14.97
RMSSD (ms)	22.91 ± 17.13	19.64 ± 18.73	19.06 ± 18.64
HFP (ms²)	219.21 ± 322.10	179.74 ± 424.17	76.95 ± 350.79
LF/HF ratio (ms²)	2.708 ± 3.124	1.213 ± 4.307	0.848 ± 3.657

DGSB, Device Guided Slow Breathing; HFP, high frequency power (0.15-0.4 Hz) of heartbeat series; LF/HF ratio, the ratio between HFP and LFP [low frequency power (0.04-0.15 Hz) of heartbeat series]; pNN50, proportion of heartbeat intervals that are larger than 50 msec; RMSSD, root mean square standard of heart rate intervals; SDNN, standard deviation of heartbeat intervals.