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
Is proximal airway pressure a good reflection of peripheral airspace pressure in infants and children models under HFJV?
This experimental study was carried out to determine if an alveolar positive end-expiratory pressure (PEEP) could occur during high frequency jet ventilation (HFJV) in infants, and if tracheal pressure is a good estimation of alveolar pressure. We used physical models simulating a 1.5 kg premature (P), a 3 kg newborn (N) and a 6 kg child (C) with normal compliance and normal resistance. Moreover, in the N model, we used two different resistances and lung compliance heterogeneity was studied in the P model. ⋯ The end-expiratory pressure drop between Palv and Paw (delta EEP) was higher in N and increased from 0.5 to 2 cm H2O with the shortening of Te and with airway resistances, i.e. the presence of ETT. In the heterogeneous model, PEEP and delta EEP were greater in the higher compliance alveolus. This study shows that the end-expiratory Palv is underestimated by end-expiratory Paw.(ABSTRACT TRUNCATED AT 250 WORDS)
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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.