Resumo

PEREZ, R. P; PEREZ, Jairo. J; BETANCUR, M. J  e  BUSTAMANTE, J. AN ALTERNATIVE METHOD FOR POWER CONTROL OF LUMINICINTENSITY IN PULSEOXIMETRY ON REAL TIME. Rev. ing. biomed. [online]. 2015, vol.9, n.17, pp.35-43. ISSN 1909-9762.

Pulse oximetry is an essential optical based non-invasive tool for monitoring blood oxygen saturation. It uses spectrophotometry to detect two light intensities (600 and 900 nm) through the skin; it provides information on tissue perfusion and quantity of transported oxygen. The process relies on a current control circuit, two light emitting sources, a photodetector, and a digital signal processor that adjusts the light intensities for different tissue characteristics. This paper proposes an alternative method of pulse width modulation for controlling the mean light intensity level, whose principle is a pulse width nodulation of the current applied to the LEDs in the emitting stage. This system allows modifying the DC level and the amplitude of the AC signal of the photopletismographic wave. The results is the reduction of the number of analog components and power consumption. The methodology presented, it allows adjusting the definition of the sample signal and offers power reductions of 21% and 40% compared to schematics given by Freescale Semiconductor, Inc. and Texas Instruments Incorporated, respectively. Thus, by using synchronized signal pulse width modulation to emit light, with frequencies above 333 kHz and steps of 50 ns, it will allow power reductions of 41%, compared to the conventional analog modulation module MDK pulse oximeter.

Palavras-chave : LED Drive; Signal Processing; Photoplethysmography Signal; Pulse Oximeter.

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