Table 2.

Heart rate variability ascertainment methods and reporting

First author, Year	ECG duration	Time domains					Frequency domains
		SDNN	SDAN N	rMSSD	CVRR	Other	LF	HF	LF/HF	Other
Environmental exposure
Oka, 2003	5 min	X			X		X	X
Grandjean, 2004	300 R-R intervals				X		X	X	X	CCV-LF, CCV-HF
Murata, 2006	300 R-R intervals						X		X	CCV-LF, CCV- HF, PSD-LF, PSD-HF
Valera, 2008	2 h	X	X	X	X	pNN50	X	X	X	VLF
Choi, 2009	5 min				X					CCV-LF, CCV-HF
Lim, 2010	5 min	X					X	X		TP
Yaginuma-Sakurai, 2010	300 R-R intervals *				X		X		X	CCV-LF, CCV- HF, PSD-LF, PSD-HF
Valera, 2011a	2 h	X	X	X			X	X	X
Valera, 2011b	2 h	X	X	X			X	X	X
Valera, 2012	2 h	X	X	X	X		X	X	X
Occupational exposure
Piikivi, 1989	60 R-R intervals					MSDD during normal breathing, and maximal/minimal R-R during deep breathing, during Valsalva maneuver and during fast tilting
Abdel-Hamid, 2001	1 min					Maximal R-R, minimal R-R, maximal/minimal R-R, (maximal – minimal)/resting R-R

^*Heart rate variability analyses based on 100 consecutive R-R intervals with the minimal standard deviation.

Abbreviations: CCV: component coefficient of variation; CVRR: coefficient of variation of R-R intervals; pNN50: proportion of interval differences of successive R-R intervals > 50 ms; PSD: power spectral density; rMSSD: square root of the mean square differences of successive R-R intervals; SDANN: standard deviation of the average RR-intervals calculated over 5 min periods; SDNN: standard deviation of R-R intervals; VLF: very low frequency; TP: total power.