OSA	obstructive sleep apnea
PSG	polysomnography
ECGs	electrocardiograms
RRI(s)	R-R interval(s)
CVHR	cyclic variation of heart rate
SpO2	oxygen saturation
ODI	oxygen desaturation index
AHI	apnea-hypopnea index
HF	high-frequency components
LF	low-frequency components
VLF	very low frequency components
SRRI	short average of RRI
LRRI	long average of RRI
VRRI	valley of the RRI fluctuation
HRV	heart rate variability
PLMS	periodic leg movement during sleep
ACAT	auto-correlated wave detection with adaptive threshold