Symbolic Dynamic Analysis of Relations Between Cardiac and Breathing Cycles in Patients on Weaning Trials

Traditional time-domain techniques of data analysis are often not sufficient to characterize the complex dynamics of the cardiorespiratory interdependencies during the weaning trials. In this paper, the interactions between the heart rate (HR) and the breathing rate (BR) were studied using joint symbolic dynamic analysis. A total of 133 patients on weaning trials from mechanical ventilation were analyzed: 94 patients with successful weaning (group S) and 39 patients that failed to maintain spontaneous breathing (group F). The word distribution matrix enabled a coarse-grained quantitative assessment of short-term nonlinear analysis of the cardiorespiratory interactions. The histogram of the occurrence probability of the cardiorespiratory words presented a higher homogeneity in group F than in group S, measured with a higher number of forbidden words in group S as well as a higher number of words whose probability of occurrence is higher than a probability threshold in group S. The discriminant analysis revealed the best results when applying symbolic dynamic variables. Therefore, we hypothesize that joint symbolic dynamic analysis provides enhanced information about different interactions between HR and BR, when comparing patients with successful weaning and patients that failed to maintain spontaneous breathing in the weaning procedure

An Adaptive Monitoring Scheme for Automatic Control of Anaesthesia in dynamic surgical environments based on Bispectral Index and Blood Pressure.

During surgical procedures, bispectral index (BIS) is a well-known measure used to determine the patient's depth of anesthesia (DOA). However, BIS readings can be subject to interference from many factors during surgery, and other parameters such as blood pressure (BP) and heart rate (HR) can provide more stable indicators. However, anesthesiologist still consider BIS as a primary measure to determine if the patient is correctly anaesthetized while relaying on the other physiological parameters to monitor and ensure the patient's status is maintained. The automatic control of administering anesthesia using intelligent control systems has been the subject of recent research in order to alleviate the burden on the anesthetist to manually adjust drug dosage in response physiological changes for sustaining DOA. A system proposed for the automatic control of anesthesia based on type-2 Self Organizing Fuzzy Logic Controllers (T2-SOFLCs) has been shown to be effective in the control of DOA under simulated scenarios while contending with uncertainties due to signal noise and dynamic changes in pharmacodynamics (PD) and pharmacokinetic (PK) effects of the drug on the body. This study considers both BIS and BP as part of an adaptive automatic control scheme, which can adjust to the monitoring of either parameter in response to changes in the availability and reliability of BIS signals during surgery. The simulation of different control schemes using BIS data obtained during real surgical procedures to emulate noise and interference factors have been conducted. The use of either or both combined parameters for controlling the delivery Propofol to maintain safe target set points for DOA are evaluated. The results show that combing BIS and BP based on the proposed adaptive control scheme can ensure the target set points and the correct amount of drug in the body is maintained even with the intermittent loss of BIS signal that could otherwise disrupt an automated control system

Instrumented usability analysis for mobile devices

Instrumented usability analysis involves the use of sensors during a usability study which provide observations from which the evaluator can infer details of the context of use, specific activities or disturbances. This is particularly useful for the evaluation of mobile and wearable devices, which are currently difficult to test realistically without constraining users in unnatural ways. To illustrate the benefits of such an approach, we present a study of touch-screen selection of on-screen targets, whilst walking and sitting, using a PocketPC instrumented with an accelerometer. From the accelerometer data the user’s gait behaviour is inferred, allowing us to link performance to gait phase angle, showing there were phase regions with significantly lower error and variability. The article provides examples of how information acquired via sensors gives us quantitatively measurable information about the detailed interactions taking place when mobile, allowing designers to test and revise design decisions, based on realistic user activity

The trainability and contralateral response of cold-induced vasodilatation in the fingers following repeated cold exposure

Cold-induced vasodilatation (CIVD) is proposed to be a protective response to prevent cold injuries in the extremities during cold exposure, but the laboratory-based trainability of CIVD responses in the hand remains equivocal. Therefore, we investigated the thermal response across the fingers with repeated local cold exposure of the whole hand, along with the transferability of acclimation to the fingers of the contralateral hand. Nine healthy subjects immersed their right hand up to the styloid process in 8°C water for 30 min daily for 13 days. The left hand was immersed on days 1 and 13. Skin temperature was recorded on the pads of the five fingertips and the dorsal surface of the hand. The presence of CIVD, defined as an increase in finger skin temperature of 0.5°C at any time during cooling, occurred in 98.5% of the 585 (9 subjects × 5 sites × 13 trials) measurements. Seven distinct patterns of thermal responses were evident, including plateaus in finger temperature and superimposed waves. The number (N) of CIVD waves decreased in all digits of the right hand over the acclimation period (P = 0.02), from average (SD) values ranging from 2.7 (1.7) to 3 (1.4) in different digits on day 1, to 1.9 (0.9) and 2.2 (0.7) on day 13. Average (SD) finger skin temperature (Tavg) ranged from 11.8 (1.4)°C in finger 5 to 12.7 (2.8)°C in finger 3 on day 1, and then decreased significantly (P < 0.001) over the course of the training immersions, attaining values ranging from 10.8 (0.9)°C in finger 4 to 10.9 (0.9)°C in finger 2 on day 13. In the contralateral hand, N was reduced from 2.5 to 1.5 (P < 0.01) and Tavg by ∼2°C (P < 0.01). No changes were observed in thermal sensation or comfort of the hand over the acclimation. We conclude that, under conditions of whole-hand immersion in cold water, CIVD is not trainable and may lead to systemic attenuation of thermal responses to local cooling. © Springer-Verlag 2008

NSC30753

Conversation partners on mobile phones can align their walking gait without physical proximity or visual feedback. We investigate gait synchronization, measured by accelerometers while users converse via mobile phones. Hilbert transforms are used to infer gait phase angle, and techniques from synchronization theory are used to infer level of alignment. Experimental conditions include the use of vibrotactile feedback to make one conversation partner aware of the other's footsteps. Three modes of interaction are tested: reading a script, discussing a shared image and spontaneous conversation. The vibrotactile feedback loop on its own is sufficient to create synchronization, but there are complex interference effects when users converse spontaneously. Even without vibration crosstalk, synchronisation appeared for long periods in the spontaneous speech condition, indicating that users were aligning their walking behaviour from audible cues alone

Instrumented usability analysis for mobile devices: gait phase effects

No abstract available

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