Effects of Hypoxia on Selected Psychophysiological Stress Responses of Military Aircrew

Table 3

Heart rate variability.

	Evaluation moment
Variables	Baseline	Hypoxia	Recovery		Moment comparison; (1): baseline; (2): hypoxia; (3): recovery
HR mean (bpm)				0.003	;
HR max (bmp)				0.375
HR min (bmp)				0.453
RMSSD (ms)				0.047
PNN50 (%)				0.074
LF (n.u)				0.039
HF (n.u)				0.064
LF/HF (ratio)				.005	;
SD1 (ms)				≤0.001	;
SD2 (ms)				≤0.001	;

HR: heart rate; RMSSD: square root of the mean of the sum of the squared differences between adjacent normal RR intervals; pNN50: the percentage of differences between RR intervals higher than 50 ms; HF: high frequency; LF: low frequency; n.u.: normalised unit; SD1: variability of the short-term HRV; SD2: variability of the long-term HRV.