Abstract :
[en] CONTEXT:
Heart rate variability (HRV) is thought to reflect the affective and physiological aspects of pain and is emerging as a possible descriptor of the functional brain organization contributing to homeostasis.
OBJECTIVES:
To investigate whether the short-term Complexity Index (CIs; short-term Complexity Index), a measure of HRV complexity, is useful to discriminate responses to potentially noxious and non-noxious stimulation in patients with different levels of consciousness.
METHODS:
Twenty-two patients (11 minimally conscious state [MCS], 11 vegetative state/unresponsive wakefulness syndrome [VS/UWS]) and 14 healthy controls [HC] were enrolled. We recorded the electrocardiographic response and calculated the CIs before (baseline), during, and following non-noxious and noxious stimulation. Mann-Whitney and Wilcoxon's tests were used to investigate differences in CIs according to the level of consciousness (i.e., HC vs patients and VS/UWS vs MCS) and the three conditions (i.e., baseline, non-noxious, noxious). The correlation between the three conditions and the Coma Recovery Scale-Revised (CRS-R) was investigated by Spearman's correlations.
RESULTS:
We observed higher CIs values in HC as compared with patients during baseline (p<.034) and following the noxious stimulation (p<.0001). We also found higher values in MCS vs VS/UWS patients following the noxious condition (p<.001) and lower values in the noxious vs non-noxious condition solely for the VS/UWS group (p<.007). A correlation was found between CIs in noxious condition and CRS-R scores.
CONCLUSION:
Our results suggest a less complex autonomic response to noxious stimuli in VS/UWS patients. Such method may help to better understand sympathovagal response to potentially painful stimulation in brain-injured patients.
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