Table 1.

Spectral and Valsalva maneuver parameters

Abbreviation	Definition	Significance
RRI-HF	RR interval variability in the high frequency band	Marker of parasympathetic tone
RRI-LF	RR interval variability in the low frequency band	Marker of parasympathetic tone
SBP-LF	Systolic blood pressure variability in the low frequency band	Marker of sympathetic tone
pNN50	Percentage of consecutive RR intervals that are more than 50 millisecond different from adjacent RR interval	Marker of parasympathetic tone
PRT	Pressure recovery time	Marker of sympathetic tone
BRS-a	Adrenergic baroreflex sensitivity	Marker of sympathetic tone
BRS-v	Cardiovagal baroreflex sensitivity	Marker of parasympathetic tone
Phase 2 SBP Decrement	The decrease in systolic blood pressure during the Valsalva maneuver from the start to the lowest point of phase 2	Marker of sympathetic tone
Phase 2 DBP Decrement	The decrease in diastolic blood pressure during the Valsalva maneuver from the start to the lowest point of phase 2	Marker of sympathetic tone

Spectral and Valsalva maneuver parameters and their clinical significance.