Disclosed herein is an apparatus, method, and system that can be used to
(1) simultaneously monitor HRV and other physiological parameters, (2)
determine whether HRV can be reliably collected, (3) detect ANS arousal,
(4) determine the effects of the ANS arousal on HRV, (5) determine the
minimum extent to which a timed HRV study should be extended after an ANS
arousal, and (6) analyze the effects of ANS arousal on HRV.