Medical & biological engineering & computing
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Med Biol Eng Comput · May 2005
Influence of variable nerve fibre geometry on the excitation and blocking threshold. A simulation study.
The aim of the study was to investigate how variable fibre geometry influences the excitation and blocking threshold of an undulating peripheral nerve fibre. The sensitivity of the excitation and blocking thresholds of the nerve fibres to various geometric and stimulation parameters was examined. The nerve fibres had a spiral shape (defined by the undulation wavelength, undulation amplitude and phase), and the internodal length varied. ⋯ Owing to undulation, the blocking threshold of large fibres could be higher than the blocking threshold of small-diameter fibres, even if they had the same geometry. The results indicate that, during skeletal muscle stretching and contracting or during variation in joint angle, the excitation and blocking thresholds of the nerve fibres change owing to variations in fibre geometry. A straight fibre model could be too simple for modelling the response of peripheral nerve fibres to electrical stimulation.
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Med Biol Eng Comput · Mar 2005
Detection of needle puncture to blood vessel using puncture force measurement.
Although blood sampling is frequently performed, a system to take blood samples automatically has not yet been developed. In the paper, as a first step towards automatic blood sampling, an examination of an automatic method for puncturing blood vessels is described. The force waveforms produced by puncturing rabbit ear veins were measured. ⋯ An algorithm that allowed the detection of this peak was developed, and parameters of a filter to improve the accuracy of the algorithm were determined. Using this algorithm, automatic needle punctures were performed in a rabbit ear vein and then were simulated using the data derived from manual needle puncture on four other rabbits. The results gave 30 fully successful cases of 33 trials of needle puncture and showed that measurement of the puncture force may be important for automatic needle puncture of blood vessels.
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Med Biol Eng Comput · Jan 2005
Robust design of finger probe in non-invasive total haemoglobin monitor.
The development of a non-invasive monitor of total haemoglobin has been reported previously. The paper presents the design and testing of a finger probe used in that optical haemoglobin monitor. When a finger is inserted into the probe, light is radiated onto the nail, and a silicon detector measures transmitted light. ⋯ An optimally designed finger probe from DOE analysis, compared with the initial design, increased the correlation coefficient from 0.696 to 0.869 and improved the standard deviation from 1.18 to 0.81 g dl(-1) in predicting total haemoglobin. This was under different conditions of finger-probe alignment. Under different ambient light conditions, the optimum design improved the correlation coefficient from 0.735 to 0.870 and reduced the standard deviation from 1.14 to 0.83 g dl(-1).
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Med Biol Eng Comput · Nov 2004
Non-contact determination of vital sign alterations in hypovolaemic states induced by massive haemorrhage: an experimental attempt to monitor the condition of injured persons behind barriers or under disaster rubble.
To assess a non-contact method to determine the physical alteration of human subjects confined behind a barrier or under disaster rubble, an experimental, non-contact monitoring system was tested on rabbits in a hypovolaemic state. New Zealand male rabbits behind a barrier were subjected to hypovolaemic shock induced by the withdrawal of arterial blood (2ml per 100g body weight). The hypovolaemic state was determined by linear discriminant analysis using non-contact-derived variables: heart rate X1 and respiratory rate X2. ⋯ The hypovolaemic rabbits developed metabolic acidosis (HCO3- 18.6+/-11.1 mmol l(-1) and pH 7.15+/-0.18 in arterial blood). The systolic blood pressure of the hypovolaemic group and the control was 56+/-4 and 83+/-6 mmHg, respectively (p < 0.01). The proposed method appears promising for applications to monitor the condition of human subjects behind barriers or under disaster rubble.
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Med Biol Eng Comput · Sep 2004
Reduction of false arterial blood pressure alarms using signal quality assessment and relationships between the electrocardiogram and arterial blood pressure.
The paper presents an algorithm for reducing false alarms related to changes in arterial blood pressure (ABP) in intensive care unit (ICU) monitoring. The algorithm assesses the ABP signal quality, analyses the relationship between the electrocardiogram and ABP using a fuzzy logic approach and post-processes (accepts or rejects) ABP alarms produced by a commercial monitor. ⋯ By rejecting 98.2% (159 of 162) of the false ABP alarms produced by the monitor using the test set of data, the algorithm was able to reduce the false ABP alarm rate from 26.8% to 0.5% of ABP alarms, while accepting 99.8% (441 of 442) of true ABP alarms. The results show that the algorithm is effective and practical, and its use in future patient monitoring systems is feasible.