International journal of clinical monitoring and computing
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Int J Clin Monit Comput · Aug 1994
Differences in the topographical distribution of EEG activity during surgical anaesthesia and on emergence from volatile anesthetics.
Computerized processing of a 16 channel EEG allows mapping and display of cortical electrical activity in a useful mode for intraoperative monitoring. We studied the topographical distribution of EEG-activity displayed as spectral maps comparing inhalational anaesthesia with isoflurane or enflurane during surgical anaesthesia and emergence. ⋯ At near awakening the frontal and occipital dominance of delta activity disappeared in both groups and was replaced by homogeneous delta activity over the entire cortex; variations in the topographical distribution of enflurane and isoflurane were recorded in the other spectral bands. We conclude that changes in topographic EEG patterns observed during the transition from surgical anaesthesia to emergence, in particular the disappearance of frontal and occipital dominance of delta activity common to isoflurane and enflurane, may serve to detect undesirably light levels of anaesthesia.
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Int J Clin Monit Comput · Aug 1994
Assessment of depth of general anesthesia. Observations on processed EEG and spectral edge frequency.
The daily use of muscle relaxants and the lack of correlation between the hemodynamic behavior and stages of general anesthesia represent the main obstacles in defining the level of cortical activity depression by the anesthetic drugs. Since classical EEG is cumbersome in the operating room, and demands special knowledge, computerized methods of EEG wave analysis have more or less replaced the 'raw' display of the electrical activity of CNS. The paper describes the place of spectral edge frequency (SEF), one of the parameters obtained by processing the EEG waves, in the list of variables which could be monitored during general anesthesia. ⋯ Some data also suggested that a stable SEF on that range contributed to a higher degree of immediate postoperative analgesia after Cesarean section. The limits of SEF oblige the scientists to go on looking for other monitored parameters, to be studied in correlation with processed EEG. Further studies are needed, in order to improve the anesthesiologist's capabilities to define correctly the stage of general anesthesia.
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Int J Clin Monit Comput · May 1994
The AVL-mode: a safe closed loop algorithm for ventilation during total intravenous anesthesia.
The Adaptive Lung Ventilation Controller (ALV-Controller) represents a new approach to closed loop control of ventilation. It is based on a pressure controlled ventilation mode. Adaptive lung ventilation signifies automatic breath by breath adaptation of breathing patterns to the lung mechanics of an individual patient. ⋯ Accuracy of the controller was high (27.8 ml difference between preset and applied alveolar ventilation in the mean) and stability was sufficient for clinical purposes. The results of this preliminary study show that the breathing patterns selected by the controller were well adapted to the lung mechanics of the patients. Respiratory rates, inspiratory pressures and tidal volumes were within the clinically acceptable range in all patients.
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Int J Clin Monit Comput · Feb 1994
Automatic selection of tidal volume, respiratory frequency and minute ventilation in intubated ICU patients as start up procedure for closed-loop controlled ventilation.
Before a patient can be connected to a mechanical ventilator, the controls of the apparatus need to be set up appropriately. Today, this is done by the intensive care professional. With the advent of closed loop controlled mechanical ventilation, methods will be needed to select appropriate start up settings automatically. The objective of our study was to test such a computerized method which could eventually be used as a start-up procedure (first 5-10 minutes of ventilation) for closed-loop controlled ventilation. ⋯ The analysis of standardized Test Breaths allows automatic determination of an initial ventilation pattern for intubated ICU patients. While this pattern does not seem to be superior to the one chosen by the conventional method, it is derived fully automatically and without need for manual patient data entry such as weight or height. This makes the method potentially useful as a start up procedure for closed-loop controlled ventilation.
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Int J Clin Monit Comput · Feb 1994
The effect of atropine on the T-wave amplitude of ECG during isoflurane anaesthesia.
The effect of bolus dose of atropine (20 micrograms kg-1) on the R/T-wave amplitude ratio of electrocardiogram was studied in 12 patients during isoflurane anaesthesia at electroencephalogram burst suppression level (mean ET of isoflurane 1.8 vol-%). The amplitude ratio was measured before, 1, 2, 5 and 10 min after atropine. ⋯ It is concluded, that the ECG T-wave amplitude reflects the balance of sympathetic and parasympathetic nervous activity during isoflurane anaesthesia. The use of the decibel transformation and confidence intervals seems to be a relevant method to interpret changes in physiologic measures during anaesthesia.