Association of heart rate variability index with depressive symptoms and lung function in chronic obstructive pulmonary disease

Table 4 Correlation between heart rate variability, Beck Depression Inventory score and lung function in chronic obstructive pulmonary disease patients

HRV		SDNN (ms)	SDANN (ms)	rMSSD (ms)	PNN50 (%)	HF (ms)	LF (ms)
BDI	r value	-0.673	-0.712	-0.706	-0.731	-0.632	-0.613
	P value	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001
FVC	r value	0.743	0.772	0.692	0.713	0.791	0.732
	P value	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001
FEV1	r value	0.782	0.731	0.785	0.698	0.801	0.763
	P value	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001
FEV1/FVC	r value	0.719	0.692	0.783	0.772	0.795	0.697
	P value	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001

SDNN: Standard deviation of normal-to-normal intervals; SDANN: Standard deviation of the average of normal-to-normal intervals; rMSSD: Root mean square of successive differences of normal-to-normal intervals; PNN50: Percent of pairs of successive normal intervals that are differing by more than 50 ms; HF: High frequency; LF: Low frequency; HRV: Heart rate variability; FEV1: First-second expiratory volume; FVC: Forced vital capacity.