The discriminatory value of cardiorespiratory interactions in distinguishing awake from anaesthetised states: a randomised observational study

Depth of anaesthesia monitors usually analyse cerebral function with or without other physiological signals; noninvasive monitoring of the measured cardiorespiratory signals alone would offer a simple, practical alternative. We aimed to investigate whether such signals, analysed with novel, non-linear dynamic methods, would distinguish between the awake and anaesthetised states. We recorded ECG, respiration, skin temperature, pulse and skin conductivity before and during general anaesthesia in 27 subjects in good cardiovascular health, randomly allocated to receive propofol or sevoflurane. Mean values, variability and dynamic interactions were determined. Respiratory rate (p = 0.0002), skin conductivity (p = 0.03) and skin temperature (p = 0.00006) changed with sevoflurane, and skin temperature (p = 0.0005) with propofol. Pulse transit time increased by 17% with sevoflurane (p = 0.02) and 11% with propofol (p = 0.007). Sevoflurane reduced the wavelet energy of heart (p = 0.0004) and respiratory (p = 0.02) rate variability at all frequencies, whereas propofol decreased only the heart rate variability below 0.021 Hz (p < 0.05). The phase coherence was reduced by both agents at frequencies below 0.145 Hz (p < 0.05), whereas the cardiorespiratory synchronisation time was increased (p < 0.05). A classification analysis based on an optimal set of discriminatory parameters distinguished with 95% success between the awake and anaesthetised states. We suggest that these results can contribute to the design of new monitors of anaesthetic depth based on cardiovascular signals alone

Stochastic dynamics of anaesthesia

Recent developments in the analysis of synchronization and directionality of couplings for noisy nonlinear oscillators are being applied to study the complex interactions between cardiac and respiratory oscillations, and brain waves (especially delta and gamma), during anæsthesia. It is found that marked changes occur in the inter‐oscillator interactions during anæsthesia in both rats and humans. These could form a new basis for measurement of depth of anæsthesia. The new EC programme BRACCIA will explore and quantify causal relationships between the oscillatory processes for the different stages of anæsthesia and consciousness

Interacting with Broadband Society

This book discusses the personal and social lives of e-actors inteeracting within the socio-technical structures of the evolving broadband society by exploring the different ways in which individuals, social groups, institutions, operators, manufacturers, policy makers, designers and other parties contribute to human communication and social interaction in contemporary media societies. The volume covers four theoretical and empirical areas of research: the conceptual perspectives of e-actors, the emergence of new forms of agency, subjectivity, and mediated interpersonal communication, the everyday life experiences of e-actors, and finally the shaping policies and regulations in the broadband society