Journal of clinical monitoring and computing
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J Clin Monit Comput · Dec 2014
Automatic control of the NMB level in general anaesthesia with a switching total system mass control strategy.
This paper presents a model based switching control strategy to drive the neuromuscular blockade (NMB) level of patients undergoing general anesthesia to a predefined reference. A single-input single-output Wiener system with only two parameters is used to model the effect of two different muscle relaxants, atracurium and rocuronium, and a switching controller is designed based on a bank of total system mass control laws. Each of such laws is tuned for an individual model from a bank chosen to represent the behavior of the whole population. ⋯ The reference tracking improvement technique is able to produce a better reference tracking. Also, this technique showed a better performance than the (EKF). Based on these results, the switching control strategy with a bank of total system mass control laws proved to be robust enough to be used as an automatic control system for the NMB level.
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J Clin Monit Comput · Dec 2014
Randomized Controlled TrialForty-five degree wrist angulation is optimal for ultrasound guided long axis radial artery cannulation in patients over 60 years old: a randomized study.
Arterial cannulation is a common anaesthetic procedure that might be challenging and time-consuming in elderly patients. To establish an appropriate wrist joint position for arterial cannulation is crucial for ultrasound (US)-guided cannulation success. This study aimed to find out the optimal wrist joint angle for long axis in-plane (LA-IP) US-guided approach in radial artery cannulation in elderly patients. ⋯ Number of attempts and total success rate were similar among groups, whereas first attempt success rate was significantly increased in 45° group compared to other groups (p < 0.05). Mean arterial height of the first attempt successful group was statistically increased compared to the first attempt failed group (p < 0.001) and mean cannulation time and mean number of attempts were also negatively correlated with arterial height (p < 0.001; for all comparisons). The 45° wrist angle increment might be advantageous in US-guided LA-IP radial artery cannulation in elderly patients in view of cannulation time and first attempt success rate.
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J Clin Monit Comput · Dec 2014
Randomized Controlled TrialNon-stationarity of EEG during wakefulness and anaesthesia: advantages of EEG permutation entropy monitoring.
Monitors evaluating the electroencephalogram (EEG) to determine depth of anaesthesia use spectral analysis approaches for analysis windows up to 61.5 s as well as additional smoothing algorithms. Stationary EEG is required to reliably apply the index algorithms. Because of rapid physiological changes, artefacts, etc., the EEG may not always fulfil this requirement. ⋯ Especially during wakefulness a conflict between stationary EEG sequence durations and methods used for monitoring may exist. PeEn does not require stationarity and functions for EEG sequences as short as 2 s. These promising results seem to support the application of non-linear parameters, such as PeEn, to depth of anaesthesia monitoring.
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J Clin Monit Comput · Dec 2014
Evaluation of a computer program for non-invasive determination of pulmonary shunt and ventilation-perfusion mismatch.
We describe a three-compartment model (shunt and two perfused compartments) to analyse the relationship between inspired oxygen (FIO2) and arterial oxygen saturation (SaO2) in terms of pulmonary shunt and ventilation-perfusion ratio (VA/Q). The program was tested using 24 exact datasets, each with six pairs of FIO2 and SaO2 data points with known VA/Q and shunt, generated by a complex calculator of gas exchange. Additional datasets were created by adding noise and rounding the exact sets, and by reducing the number of data points per dataset. ⋯ It is probably advantageous to correct for foetal haemoglobin in neonatal datasets. Analysis of FIO2 versus SaO2 datasets using a three compartment model provides accurate estimates of shunt and VA/Q when arterio-venous difference in oxygen content is known. The estimates may have value as objective measures of gas exchange, and as a visual guide for oxygen therapy.
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J Clin Monit Comput · Dec 2014
Simulating physiological interactions in a hybrid system of mathematical models.
Mathematical models can be deployed to simulate physiological processes of the human organism. Exploiting these simulations, reactions of a patient to changes in the therapy regime can be predicted. Based on these predictions, medical decision support systems (MDSS) can help in optimizing medical therapy. ⋯ The gas exchange submodel being reactive to changes in cardiac output showed a resulting deviation of less than 0.1 %. Therefore, the proposed model is usable in combinations where cardiovascular simulation does not have to be detailed. Computing costs have been decreased dramatically by a factor 186 compared to a model combination employing the 19-compartment model.