A utilização de transformadas de wavelet e de detrended fluctuation analysis no estudo da microcirculação da pele humana
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2013
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A Fluxometria por Laser Doppler (LDF) é uma técnica não invasiva usada para medir o fluxo microvascular da pele humana. No fluxo é possível isolar componentes oscilatórias em gamas de frequências características que se encontram relacionadas com as actividades cardíaca, respiratória, miogénica, simpática e metabólica. A LDF permite assim estudar a fisiologia do fluxo sanguíneo. Neste trabalho foram realizadas medições de LDF nos tornozelos de 9 mulheres saudáveis numa situação de restrição à perfusão, usando uma braçadeira nos tornozelos. Os dados foram analisados com Transformada de Wavelet e Detrended Fluctuation Analysis (DFA) de modo a estudar os rácios das amplitudes das componentes de Wavelet e os respectivos expoentes . Estes parâmetros foram comparados nas situações de repouso, de restrição à perfusão e de recuperação após remoção da braçadeira. Observou-se que durante a restrição à perfusão houve um aumento significativo dos rácios de amplitude e dos expoentes a para as componentes cardíaca, respiratória e miogénica, o que pode reflectir vasoconstrição. Os parâmetros da componente metabólica apresentaram uma diminuição que se pode relacionar com variações na libertação de NO por parte do endotélio. Após a libertação da braçadeira, os parâmetros das componentes respiratória, miogénica e metabólica retornaram aos valores iniciais. Aanálise combinada de Wavelet com DFAoferece uma nova visão sobre a regulação do fluxo microvascular.
Laser Doppler Flowmetry (LDF) is a non-invasive technique used to assess microvascular flow oscillations. Skin microcirculation has been shown to contain oscillation components with characteristic frequency ranges. These are related to heart, respiration, and myogenic, sympathetic and metabolic activities. So, the evaluation of each component in time may hold important information regarding blood flow physiology. LDF measurements were done at the ankle of 9 female healthy subjects during ankle perfusion restriction using a cuff. Wavelet Transform and Detrended Fluctuation Analysis (DFA) were applied to LDF signals to derive component´s amplitude ratios and a exponents. Parameters were compared in rest, during perfusion restriction, and in recovery after the cuff release. During perfusion restriction a significant increase of heart, respiratory and myogenic components' parameters was observed, suggesting vasoconstriction. Metabolic parameters exhibited a decrease that could be related to NO release changes from the endothelium. Finally, after cuff release a recovery of both amplitude ratios and a exponents was noted, particularly in the respiratory, myogenic and metabolic components. Combined analysis of wavelet component amplitudes with DFAderived exponents can provide a new and more complete picture of microvascular blood-flow regulation.
Laser Doppler Flowmetry (LDF) is a non-invasive technique used to assess microvascular flow oscillations. Skin microcirculation has been shown to contain oscillation components with characteristic frequency ranges. These are related to heart, respiration, and myogenic, sympathetic and metabolic activities. So, the evaluation of each component in time may hold important information regarding blood flow physiology. LDF measurements were done at the ankle of 9 female healthy subjects during ankle perfusion restriction using a cuff. Wavelet Transform and Detrended Fluctuation Analysis (DFA) were applied to LDF signals to derive component´s amplitude ratios and a exponents. Parameters were compared in rest, during perfusion restriction, and in recovery after the cuff release. During perfusion restriction a significant increase of heart, respiratory and myogenic components' parameters was observed, suggesting vasoconstriction. Metabolic parameters exhibited a decrease that could be related to NO release changes from the endothelium. Finally, after cuff release a recovery of both amplitude ratios and a exponents was noted, particularly in the respiratory, myogenic and metabolic components. Combined analysis of wavelet component amplitudes with DFAderived exponents can provide a new and more complete picture of microvascular blood-flow regulation.
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MEDICINA, PELE, FISIOLOGIA, MICROCIRCULAÇÃO CUTÂNEA, MEDICINE, PHYSIOLOGY, SKIN, SKIN MICROCIRCULATION, FLUXOMETRIA POR LASER-DOPPLER, LASER-DOPPLER FLOWMETRY, TRANSFORMADA DE WAVELET, WAVELET TRANSFORM