Medical engineering & physics
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Rapid post-injury cooling of a skin burn has been shown to have both symptomatic and therapeutic benefits. However, the latter cannot be explained by temperature reduction alone, and must thus be secondary to an altered biological response. In this study, we construct a computational model to calculate the heat transfer and damage accumulation in human skin during and after a burn. ⋯ Hence our results confirm that while the reduction in tissue temperatures is indeed quicker, the therapeutic benefit of cooling cannot be explained by thermal arguments (i.e. based on Arrhenius damage models) alone. We plan to validate this hypothesis by conducting future microarray analyses of differential gene expression in cooled and non-cooled burn lesions. Our computational model will support such experiments by calculating the necessary conditions to produce a burn of specified severity for a given experimental setup.
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Increasing the selectivity of the detection system in surface electromyography (EMG) is beneficial in the collection of information of a specific portion of the investigated muscle and to reduce the contribution of undesired components, such as non-propagating components (due to generation or end-of-fibre effects) or crosstalk from nearby muscles. A comparison of the ability of different spatial filters to reduce the amount of crosstalk in surface EMG measurements was conducted in this paper using simulated signals. It focused on the influence of different properties of the muscle anatomy (changing subcutaneous layer thickness, skin conductivity, fibre length) and detection system (single, double and normal double differential, with two inter-electrode distances - IED) on the amount of crosstalk present in the measurements. ⋯ From these results it was found that the selectivity of each spatial filter varies depending on the transversal location of the measurement electrodes and on the anatomy. An increase in skin conductivity favourably affects the selectivity of normal double differential filters as does an increase in subcutaneous layer thickness. An increase in IED decreases the selectivity of all the analysed filters.
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The Pennes model predicts the ability of the skin to dissipate heat as a function of conductive heat transfer and blood flow. Conductive heat exchange may be affected by skin moisture and subcutaneous fat thickness, factors not considered by Pennes. In the present investigation, we sought to expand the Pennes model by examining subcutaneous fat and skin moisture as factors of heat dissipation and their effects on heat exchange and blood flow. ⋯ There was a significant inverse correlation between skin moisture and skin temperature after 5s of heat application (r=-0.73, p<0.001) with O and D having significantly less skin moisture than Y (p<0.05). O and D had significantly increased skin temperatures in response to local heat, as compared to Y, in all global temperatures (p<0.05). Thus, the Pennes model may need to be adjusted to take into consideration aging, diabetes, skin moisture, and subcutaneous fat thickness.
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We present a novel unbiased and normalized adaptive noise reduction (UNANR) system to suppress random noise in electrocardiographic (ECG) signals. The system contains procedures for the removal of baseline wander with a two-stage moving-average filter, comb filtering of power-line interference with an infinite impulse response (IIR) comb filter, an additive white noise generator to test the system's performance in terms of signal-to-noise ratio (SNR), and the UNANR model that is used to estimate the noise which is subtracted from the contaminated ECG signals. The UNANR model does not contain a bias unit, and the coefficients are adaptively updated by using the steepest-descent algorithm. ⋯ The benchmark MIT-BIH arrhythmia database was used to evaluate the performance of the UNANR system with different levels of input noise. The results of adaptive filtering and a study on convergence of the UNANR learning rate demonstrate that the adaptive noise-reduction system that includes the UNANR model can effectively eliminate random noise in ambulatory ECG recordings, leading to a higher SNR improvement than that with the same system using the popular least-mean-square (LMS) filter. The SNR improvement provided by the proposed UNANR system was higher than that provided by the system with the LMS filter, with the input SNR in the range of 5-20 dB over the 48 ambulatory ECG recordings tested.
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This paper reviews various bioimpedance methods permitting to measure non-invasively, extracellular, intracellular and total body water (TBW) and compares BIA methods based on empirical equations of the wrist-ankle resistance or impedance at 50 kHz, height and weight with BIS methods which rely on an electrical model of tissues and resistances measured at zero and infinite frequencies. In order to compare these methods, impedance measurements were made with a multifrequency Xitron 4200 impedance meter on 57 healthy subjects which had undergone simultaneously a Dual X-ray absorptiometry examination (DXA), in order to estimate their TBW from their fat-free-mass. Extracellular (ECW) and TBW volumes were calculated for these subjects using the original BIS method and modifications of Matthie[Matthie JR. ⋯ For ECW, a good agreement was found between various BIS methods and that of Sergi while Hannan's values were higher. Both Matthie's and Moissl's methods gave mean TBW resistivities and volumes lower than those of Jaffrin's and DXA methods. Kushner et al. method gave values of TBW not significantly different from those of Jaffrin et al. and DXA, as Hannan's method in men, but Lukaski and Deurenberg methods led to an underestimation.