Journal of clinical monitoring and computing
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J Clin Monit Comput · Apr 2002
Performance of a real-time dicrotic notch detection and prediction algorithm in arrhythmic human aortic pressure signals.
A novel algorithm for real-time detection and prediction of the dicrotic notch from aortic pressure waves was evaluated in arrhythmic aortic pressure signals from heart failure patients. A simplified model of the arterial tree was used to calculate real-time aortic flow from aortic pressure. The dicrotic notch was detected at the first negative dip from the calculated flow, prediction of the notch was performed using a percentage of the decreasing flow. ⋯ Prediction of the dicrotic notch was tested at 40%, 20%, and 0% of the decreasing calculated aortic flow. The mean time-delays to the notch were 68 +/- 14 ms, 55 +/- 12 ms, and 43 +/- 8 ms, respectively. Given these small variability, intra-beat prediction of the dicrotic notch may be used for real-time intra-aortic balloon counterpulsation inflation timing.
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J Clin Monit Comput · Apr 2002
Averaging improves the quality of impedance stroke volume measurements during the head up tilt test.
To assess the improvement in quality following averaging data from two or more tilts in the stroke volume (SV) response curve during a head-up tilt test. ⋯ Impedance measurements can be very variable, making the assessment of SV changes during a head-up tilt test difficult. By averaging the data from several tilts one can improved the quality of the SV wavelet sufficiently to identify important postural changes.
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J Clin Monit Comput · Apr 2002
Representation of somatosensory evoked potentials using discrete wavelet transform.
Somatosensory evoked potentials (SEP) have been shown to be a useful tool in monitoring of the central nervous system (CNS) during anaesthesia. SEP analysis is usually performed by an experienced human operator. For automatic analysis, appropriate parameter extraction and signal representation methods are required. The aim of this work is to evaluate the discrete wavelet transform (DWT) as such a method for an SEP representation. ⋯ The discrete wavelet transformation provides an efficient tool for SEP representation and parameterisation. Depending on the specific problem the DWT, can be adjusted to the desired accuracy, which is important for the subsequent development of automatic SEP analysers.
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New methods of data processing combined with advances in computer technology have revolutionized monitoring of patients under anesthesia. The development of systems based on analysis of brain electrical activity (EEG or evoked potentials) by neural networks has provided impetus to many investigators. Though not claiming to be the end-all in patient monitoring, the potential and efficiency of the combination does indeed stand out. Various strategies are presented and discussed, as well as suggestions for further investigation.
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J Clin Monit Comput · Apr 2002
Mycardial ischemia and determined chaos in integral homeostatic regulation.
This study was devoted to the problem of homeostatic stability loss caused by myocardial ischemia, induced by stress testing. It involved 55 patients with different variants of coronary heart disease and 15 practically healthy volunteers as controls. Routine bicycle ergometry and nonstop monitoring of the cardiac-interval duration were conducted simultaneously. ⋯ Determined chaos was shown to be the main property of these dynamics in all cases. The original method of measuring the cardiac rhythm entropy chaotisity level is presented. It is suggested that the newly revealed phenomenon of a sharp rise in the cardiac entropy trajectory chaotisity level and followed by a decrease, which happens in the multidimensional phase space, may be used as an additional criterion of myocardial ischemia development for the verification of dubious stress-testing results.