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Proceedings Paper

Transillumination waveform simulator for pulse oximetry
Author(s): Camille Vazquez-Jaccaud; Gonzalo Paez; Marija Strojnik
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Paper Abstract

Pulse oximetry technique is a non invasive method useful to monitor the quantity of oxygen in hemoglobin, used in medical diagnosis and clinical decision-making. It is based on the ratio between the red and infrared light absorbance corresponding to the oxygenated (HbO2) and non-oxygenated (Hb) state of the hemoglobin. We develop the mathematical model to obtain the oxygen saturation value observing that it depends on four known parameters: two transillumination values assessed at the common pulse oximetry wavelengths (λ1 = 660 nm y λ2 = 940 nm), and the extinction coefficients for the oxy- and deoxy-hemoglobin at these given wavelengths. Analyzing the extinction curves for oxy- and deoxy-hemoglobin we note that at λ equal to 660 nm the HbO2 component almost does not contribute to the attenuation of incidance when we transilluminate tissue (7.479x10-5 cm-1M-1). In this case is the Hb component that gives the significant attenuation value (7.863x10-4 cm-1M-1). In 940 nm the extinction coefficient of the Hb is 2.589x10-5 cm-1M-1 and we can ignore it when we count attenuation. At this λ we assume that the pulsate component is only affected by the HbO2 (2.099x10-4 cm-1M-1). This analysis of hemoglobin extinction coefficients in the absorption curves highlights the signal to noise ratio between these two oxygen dependent elements. We are interested in accentuate the better contrast interval (λ pair), where this signal-to-noise ratio is higher, looking for more transillumination information and more precise SO2 value. We propose to use a transillumination waveform simulator to study the different effects (respiration, artifact body movement, absorption, low perfusion, etc) presented in complex physiological signals and to know the optical path-integrated behavior when we transilluminate tissue. This is practical for acquisition and processing transillumination signals. The present work is the first part of a λ selection method to guaratee the optimum S/N for measurements in blood using pulse oximetry and spectroscopic techniques at near infrared.

Paper Details

Date Published: 1 September 2009
PDF: 11 pages
Proc. SPIE 7453, Infrared Spaceborne Remote Sensing and Instrumentation XVII, 74530V (1 September 2009); doi: 10.1117/12.824897
Show Author Affiliations
Camille Vazquez-Jaccaud, Ctr. de Investigaciones en Óptica, A.C. (Mexico)
Gonzalo Paez, Ctr. de Investigaciones en Óptica, A.C. (Mexico)
Marija Strojnik, Ctr. de Investigaciones en Óptica, A.C. (Mexico)

Published in SPIE Proceedings Vol. 7453:
Infrared Spaceborne Remote Sensing and Instrumentation XVII
Marija Strojnik, Editor(s)

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