Correlation between spectral measures of systolic blood pressure variability and heart rate variability during paced breathing, standing and exercise

To provide insight on the somewhat controversial issue of the physiological correlates of spectral indexes of systolic pressure variability (SPV) we assessed the relations between them and those of heart rate variability (HRV) in 20 subjects during two sympathetic maneuvers, standing (S) and exercise (E). We also evaluated the percentage of statistical differences among 50-s epochs (PSDE) of the spectral measures dynamics obtained in 5-min steady-state conditions. From time-frequency spectra, high-frequency power of RR intervals (HF_RR), low-to-high-frequency ratio (LF_RR/HF_RR), low-frequency of systolic pressure (LF_SP), high-frequency of systolic pressure (HF_SP), high-frequency of respiration (HF_Re) and HF_SP-HF_Re time-frequency coherence were computed. LF_SP-lnHF_RR, LF_SP-RR and LF_SP-LF_RR/HF_RR correlations were -0.73±0.09, -0.77±0.06, and 0.66±0.13 respectively. During E, HF_RR decreased, HF_SP increased (p<;0.001) and HF_Re-HF_SP coherence was 0.93±0.05. Global PSDE of the measures was 41±18%. HRV spectral measures show strong correlation with LF_SP power, novel evidence that supports its suitability as sympathetic index. The differential effect of E on HF_RR and HF_SP and high HF_SP-HF_Re coherence document the mechanical respiratory origin of HF_SP. Spectral measures of supposedly steady-state maneuvers present high PSDE.