Salvador Carrasco-Sosa

Response patterns of arterial pressure and heart period to Mueller manoeuvre and their comparison to those of Valsalva manoeuvre

Objective:  It has not been established if the Mueller manoeuvre (MM) induces characteristic arterial pressure (AP) and heart rate changes analogous to those observed during its respiratory strain opposite, the Valsalva manoeuvre (VM). Our aims were to explore, on a beat‐by‐beat basis, if MM evokes well‐defined changes in AP and heart period (HP), and to compare these responses with those of VM.

Additive effect of simultaneously varying respiratory frequency and tidal volume on respiratory sinus arrhythmia.

Our aims were to assess, in healthy young females and males, the effects of the linear joint variation of respiratory frequency (RF) and tidal volume (VT) on the logarithmic transformation of high-frequency power of RR intervals (lnHF). ECG and VT were recorded from 18 females and 20 males during three visually guided 30-s breathing maneuvers: linearly increasing RF (RFLI) at constant VT; linearly increasing VT (VTLI) followed by decreasing VT (VTLD) at fixed RF, and RFLI and VTLI-VTLD combined. VT of females was 20% smaller. Instantaneous RF and lnHF were computed from the time-frequency distributions of respiratory series and RR intervals. LnHF-RF and lnHF-VT relations were similar between genders. LnHF and RR intervals control-maneuver differences during combined maneuver were approximately equal to the sum of those of the independent maneuvers. LnHF-RFLI relation showed strong negative correlations in separated and combined conditions, with steeper slope in the latter (p < 0.001). LnHF-VTLI and lnHF-VTLD relations presented, in the independent maneuvers, three combinations of slopes of different sign, all with hysteresis, and in the combined maneuver, strong correlations with negative slope for VTLI and positive slope for VTLD, steeper (p < 0.001) and with greater hysteresis (p < 0.001) than the independent ones. LnHF responses to our fast, non-fatiguing and non-steady-state breathing maneuvers are: similar between genders; consistent attenuation due to RFLI, whether applied alone or combined; ambiguous and with hysteresis to independent VTLI-VTLD variations; systematic greater attenuation during RFLI combined with VTLI-VTLD, equal to the sum of the independent effects, indicating that there is no interference between them.

Beat-to-beat response patterns of spectral sympathetic estimators to the cold face test and their comparison to those of the active orthostatic test

We assessed the effects of cold face test (CFT) and active orthostatic test (AOT) on the RR intervals (RR), systolic pressure (SP) and maximal amplitude of arterial pressure first derivative (dmAP) time series of 25 healthy volunteers, and the instantaneous dynamics of their low-frequency powers (LFRR, LFSP and LFdmAP), to characterize their time course, and compare their performance as sympathetic markers as well as the magnitude of the sympathetic response evoked by each maneuver. All the variables studied displayed distinct instantaneous response patterns to each maneuver: while in CFT they increased to a plateau, in AOT they presented overshoots at the beginning and end of the test. In both tests, LFdmAP and LFSP dynamics were similar and strongly correlated, and presented a weak correlation with LFRR. Means of LFdmAP and LFSP in CFT were 7 times smaller than in AOT. Our findings support that LFSP and LFdmAP powers exhibit similar performance as noninvasive sympathetic markers and that all variables studied show distinctive beat-to-beat response patterns to each maneuver. Using the sympathetic response produced by AOT as reference, the one evoked by CFT is smaller.

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.