Abstract
The precise mechanisms underlying general anaesthesia pose important and still open questions. To address them, we have studied anaesthesia induced by the widely used (intravenous) propofol and (inhalational) sevoflurane anaesthetics, computing cross-frequency coupling functions between neuronal, cardiac and respiratory oscillations in order to determine their mutual interactions. The phase domain coupling function reveals the form of the function defining the mechanism of an interaction, as well as its coupling strength. Using a method based on dynamical Bayesian inference, we have thus identified and analysed the coupling functions for six relationships. By quantitative assessment of the forms and strengths of the couplings, we have revealed how these relationships are altered by anaesthesia, also showing that some of them are differently affected by propofol and sevoflurane. These findings, together with the novel coupling function analysis, offer a new direction in the assessment of general anaesthesia and neurophysiological interactions, in general.
Highlights
General anaesthesia plays a crucial role in many surgical procedures, and it has an enormous impact on human health
The undesirable consequences of overdose or unintended awareness might in principle be ameliorated by improved control if we could understand better the changes in function that occur during general anaesthesia, in particular the dynamical brain states, the dynamics of cardiovascular oscillations and their mutual interactions [4]
The study is based on three complementary pillars: (i) anaesthesia with two of the most widely used anaesthetics, using the same experimental set-up; (ii) application of the novel methodology of cross-frequency coupling functions to determine phase-causal links and to probe the interaction mechanisms directly, and (iii) assessment of general anaesthesia based on the combined dynamics and interactions of the brain, lungs and heart oscillations
Summary
General anaesthesia plays a crucial role in many surgical procedures, and it has an enormous impact on human health. The study is based on three complementary pillars: (i) anaesthesia with two of the most widely used anaesthetics, using the same experimental set-up; (ii) application of the novel methodology of cross-frequency coupling functions to determine phase-causal links and to probe the interaction mechanisms directly, and (iii) assessment of general anaesthesia based on the combined dynamics and interactions of the brain, lungs and heart oscillations. Cross-frequency couplings are usually inferred by methods based on the statistics of the coupled signals, such as the correlation and (bi-) coherence measures Such approaches tell one about the functional connectivity [35], but they do not provide information about causality or about the form of the coupling functions. To present visually the differences between the distributions, we used standard boxplots which refer to the descriptive statistics (median, quartiles, maximum and minimum)
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Schedule a callMore From: Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
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