Performance of the low frequency power of pulse pressure variability as a sympathetic activity measure during supine rest, controlled breathing, standing and exercise

In 28 healthy volunteers, we assessed the effects of 5-min maneuvers that provoke different sympathetic and respiratory activities (supine rest (SR), controlled breathing (CB), standing (S) and exercise (E)) on the instantaneous low (LF) and high frequency (HF) powers of pulse (LF_PP, HF_PP), systolic (LF_SP, HF_SP), and diastolic pressures (LF_DP, HF_DP), to associate physiological correlates to LF_PP and HF_PP, and to test the interchangeability of those of systolic and diastolic pressures. Except for LF_DP in E, LF_PP, LF_SP and LF_DP powers increased progressively from CB to SR, S and E. LF_SP and HF_SP powers were greater than LF_DP and HF_DP. Correlations of both LF_PP and HF_PP were greater with LF_SP and HF_SP. Instantaneous coherences of respiration with HF_PP, HF_SP and HF_DP were greater than 0.76. Sympathetic modulation is greater in LF_SP than in LF_DP and is smaller in LF_PP than the respiratory modulation in HF_PP. LF_PP adequately marks the progressive sympathetic increases evoked by the maneuvers, mainly due to its greater resemblance with LF_SP. LF_DP is not a satisfactory sympathetic index. LF_SP and HF_SP are not interchangeable with LF_DP and HF_DP respectively.