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

Abstract

We assessed the effects of cold face test (eFT) 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 (LF RR, 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 eFT 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 eFT 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 eFT is smaller.

Types of Interference Effects on the Autonomic-Cardiovascular Response to the Simultaneous Performance of Active Orthostatic and Cold Face Tests

“…2). While the time course of the response to AOT shows two overshoots in the sympathetic estimators and undershoots in HF RR , RR, BRS and RSAS, in CFT there are overshoots in HF RR , RR, BRS and RSAS [4,5]. From the above findings, CFAOT shows potentiation in the sympathetic and vagal indexes, in SP, RR (first decremental, then incremental) and predominance of AOT-related BRS and RSAS reductions.…”

“…In the present study, our methodology is further improved by: considering complex responses, as those of AOT and CFT; tracking the time-course of a battery of estimators including our proposed sympathetic activity indexes, LF PP and LF dmAP [4], and, particularly, assessing the FIEI in an instantaneous fashion. Both the difference between CFAOT and CFT+AOT and the FIEI assess the type and degree of FIE in each variable, but the FIEI also allows comparing among variables.…”

“…However, when we recently compared the time course of the autonomic cardiovascular effects of CFT and AOT, we found that their response patterns are quite opposite, because, while CFT elicits great increases in vagal activity, baroreflex sensitivity (BRS) and respiratory sinus arrhythmia sensitivity (RSAS), AOT shows a 7 times greater sympathetic activation, and BRS and RSAS reductions [4,5]. If CFT and AOT were performed simultaneously (CFAOT), how would the minimal sympathetic activity of the former interfere with the sympathetic predominance of the latter?…”

Instantaneous Time Course of Autonomic-Cardiovascular Response to Short-Term Hypoxia in Healthy Subjects: a Time-Frequency Analysis Approach

“…The gradual decrease of cardiac sympathetic activity, indicated by our cardiac sympathetic markers LF dmAP and LF PP (Fig. 2D-E) [8], contributes to the gradual depression of cardiac contractility (indicated by dmAP; Fig. 2F), with no changes in the vasomotor sympathetic tone (marked by LF SP ; Fig.…”

“…These features of our methodological approach differ from those of the majority of the published studies on the effects of hypoxia, where a single mean value of each variable is considered representative of the whole effect and their temporal course is not tracked, making it difficult to determine cause-effect relationships between variables. Additionally, as part of our battery of measures, we assessed the performance of two promising sympathetic indexes derived from the AP signal, LF dmAP and LF PP , that we have previously reported [8].…”